Glycerol: Production, consumption, prices, characterization and new trends in combustion

Renewable and Sustainable Energy Reviews 27 (2013) 475ndash493

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews

1364-03httpd

n CorrE-m

journal homepage wwwelseviercomlocaterser

Glycerol Production consumption prices characterization and newtrends in combustion

Ceacutesar AG Quispe ab Christian JR Coronado c Joatildeo A Carvalho Jr an

a Satildeo Paulo State University Guaratinguetaacute Campus Department of Energy Av Ariberto Pereira da Cunha 333 CEP 12516-410 Guaratinguetaacute SP Brazilb San Marcos National University College of Mechanical and Fluids Engineering Av UniversitariaAv Germaacuten Ameacutezaga sn University City Lima 1Lima Peruc Federal University of Itajubaacute UNIFEI Mechanical Engineering Institute IEM Av BPS 1303 Itajubaacute- MG CEP 37500-903 Brazil

a r t i c l e i n f o

Article historyReceived 31 January 2013Received in revised form11 June 2013Accepted 16 June 2013Available online 3 August 2013

KeywordsGlycerolByproductsCombustionBiodiesel

21$ - see front matter amp 2013 Elsevier Ltd Axdoiorg101016jrser201306017

esponding author Tel +55 12 31232838 faxail address joaoacarvalhojrpqcnpqbr (JA

a b s t r a c t

The demand for petroleum has been rising rapidly due to increasing industrialization and modernizationThis economic development has led to a huge demand for energy most of which is derived from fossilfuel However the limited reserve of fossil fuel has led many researchers to look for alternative fuelswhich can be produced from renewable feedstock Increasing fossil fuel prices have prompted the globaloil industry to look at biodiesel which is from renewable energy sources Biodiesel is produced fromanimal fats and vegetable oils and has become more attractive because it is more environmentallyfriendly and is obtained from renewable sources Glycerol is the main by-product of biodiesel productionabout 10 of the weight of biodiesel is generated in glycerol The large amount of glycerol generated maybecome an environmental problem since it cannot be disposed of in the environment In this paper anattempt has been made to review the different approaches and techniques used to produce glycerol(hydrolysis transesterification refining crude glycerol) The world biodieselglycerol production andconsumption market the current world glycerin and glycerol prices as well as the news trends for theuse of glycerol mainly in Brazil market are analyzed The technological production and physicochemicalproperties of glycerol are described as is the characterization of crude glycerol obtained from differentseed oil feedstock Finally a simple way to use glycerol in large amounts is combustion which is anadvantageous method as it does not require any purification However the combustion process of crudeglycerol is not easy and there are technological difficulties The news and mainly research about thecombustion of glycerol was also addressed in this review

amp 2013 Elsevier Ltd All rights reserved

Contents

1 Introduction 4762 Glycerol 476

21 Glycerols physical properties 47622 Characterization of crude glycerol 477

3 World glycerol production and market 47831 World biodiesel and glycerol production 47832 Biodiesel and glycerol consumption market 47933 Current world glycerin and glycerol prices 480

4 The glycerol situation in Brazil 4805 Biodiesel and glycerol production technology 482

51 Hydrolysis 48252 Transesterification 48253 Refining crude glycerol 483

6 Alternatives for the use of glycerolmdashNew trends 484

ll rights reserved

+55 1231232835Carvalho Jr)

CAG Quispe et al Renewable and Sustainable Energy Reviews 27 (2013) 475ndash493476

61 Glycerol combustion 4867 Conclusion 488References 488

1 Introduction

Biofuels arose as a sustainable source of fuel in the search fornew energy resources and are considered an important form oftechnological progress in limiting greenhouse gas emissions anddiminishing pollution improving air quality [1] Biofuels are asource of renewable energy they are produced from naturalmaterial (biologically based) Among the most common biofuelsis ethanol generated from maize wheat or beets and biodieselfrom oily seeds andor animal fat [2] At present biofuels are usedas a source of energy as a substitute for fossil fuels because theyare biodegradable much cleaner and generate an acceptable levelof emissions gases [34]

Biodiesel stands out among biofuels It is a liquid fuel thatsobtained from natural lipids such as vegetable oil or animal fatusing industrial processes of esterification or transesterificationBiodiesel is superior to diesel oil for health and the environment(it is low in sulfur emits a low level of noxious particles like HCand CO and is better in the CO2 cycle in reducing global warming)as well as for engine performance (better lubrication high cetanenumber and more complete combustion) [5ndash7] Biodiesel isbiodegradable renewable and non-toxic It has a high flash pointbetter viscosity and caloric power similar to fossil fuels [7] Theseadvantages have convinced Asian countries to utilize biodiesel asan alternative fuel as one of the innovative solutions to reduceglobal air pollution generated by the growing number of vehicles[8] Mixtures are the most viable way to increase biodiesel usageelevating biodiesels share of the fuel market benefitting produ-cers guaranteeing competitive pricing for end users and requiringless incentives and tax exemptions [9] It has been reported thatfrom 75 to 95 of the end price of biodiesel is influenced by thecost of the raw material [10]

On the other hand production of biodiesel has a by-productglycerol Generally 10 to 20 of the total volume of biodieselproduced is made up of glycerol [11ndash15] The production of bio-ethanol also generates glycerol as a by-product up to 10 of theweight of the sugar consumed [16] Lately an intense debate hasfocused on this important problem in biodiesel production theinevitable production of glycerol as a by-product with a lowcommercial value [1217] Growing biodiesel production will leadto large surpluses of glycerol A fundamental question soon arisesWhat can be done with the glycerol This is one of the mainreasons that research at present is focused on developing technol-ogy to convert or use the glycerol in order to improve the biodieselbusiness and drastically improve its economic viability [1218]Though glycerol is a raw material and there are over 2000industrial uses incessant biodiesel production is leading glycerolto be dealt with as a waste product Specific concerns about thesocial and environmental impacts of biodiesel production havebeen growing [1920]

This manuscript is a review of the different approaches andtechniques used to produce glycerol (hydrolysis transesterifica-tion refining crude glycerol) the world biodieselglycerol produc-tion and consumption market the current world glycerin andglycerol prices and the news trends for the use of glycerol mainlyin Brazil Though it is not an ideal fuel one option (other than itsuse in the pharmaceutical or chemical industries) could be to burnit (glycerol combustion) locally in a combined heat and energy

generation process (cogeneration) replacing fossil fuels andoptimizing the efficiency of the process as well as reducing theimpacts of this byproduct The news and mainly research aboutthe combustion of glycerol was also investigated in this review

2 Glycerol

Glycerol is the main component of triglycerides found inanimal fat vegetable oil or crude oil Glycerol is derived fromsoap or from biodiesel production [1821] Its been known since2800 BCE when it was isolated by heating fat mixed with ashesto produce soap [22] However it is considered to have beendiscovered in 1779 by Swiss pharmacist K W Scheele who wasthe first to isolate this compound when he heated a mixture oflitharge (PbO) with olive oil In 1811 French chemist M E Chevrelcalled glycerin a liquid defining the chemical formulas of fattyacids and the formulas of glycerin in vegetable oil and animal fatHis work was patented It was known as the first industrialmethod to obtain glycerin soap by reacting fatty material withlime and alkaline material [23]

21 Glycerols physical properties

Glycerol is the simplest of the alcohols and is known bypropane-123-triol according to IUPAC It is also commerciallyknown as glycerin 123-propanotriol trihydroxypropane glycer-itol or glycidic alcohol [24] Glycerol is an oily liquid it is viscousodorless colorless and has a syrupy-sweet taste Glycerol is aliquid containing three hydrophilic hydroxyl groups that areresponsible for it being hygroscopic and its solubility in water[2526] Fig 1 shows the molecular structure of glycerol made upof three hydroxyls

Glycerin is completely miscible in many substances Amongthem are alcohol (methyl ethyl isopropyl n-butyl isobutylsecondary butyl and tertiary amyl) ethylene glycol propyleneglycol trimethylene glycol monomethyl ether and phenol [2829]Solubility of glycerin in acetone is 5 by weight in ethyl acetateits 9 Its slightly soluble in dioxane and ethyl and partiallyinsoluble in superior alcohol fatty acids and hydrocarbonate aswell as in chlorinated solvents such as hexane benzene andchloroform Glycerin is very viscous at normal temperatures itremains a viscous liquid even at 100 concentration withoutcrystallizing At low temperatures concentrated glycerin solutionstend to super cool as high viscosity fluid Viscosity rises at firstuntil it quickly becomes vitreous around minus89 1C Aqueous glycerinsolutions (at different concentrations) tend to have lower viscosity[30]

At low temperatures glycerin tends to super cool instead ofcrystallize Aqueous glycerin solutions resist freezing and are usedas antifreeze in cooling systems Glycerin does not oxidize in theatmosphere in normal conditions but can be easily oxidized byother oxidants Glycerin solutions need inhibitors when they areexposed to heat and in contact with ferrous metal or copper sincethe salts contained in these materials can catalyze oxidation [31]Glycerol has low volatility and low vapor pressure which is strictlylinked with its hygroscopic property Between 0 and 70 1Ctemperature changes have little effect on the vapor pressure ofglycerin solutions Like other alcohols glycerin has a lower vapor

Table 2Analysis of three glycerol fuels [44]

USP Glycerol Methylated Demethylated

C () 391 4205 6727H () 87 1014 1143N () 0 o005 o005O () 522 4332 1706S () 0 0078 o005H2O () 0 103 147Ash () 0 306 223Ca (ppm) o23 119Na (ppm) 11600 17500K (ppm) 628 541Cl (ppm) 124 154Mg (ppm) o8 29P (ppm) 2220 1750HHV (MJkg) 160 218 206

Table 3Analysis results of macro elements carbon and nitrogen measurement in crudeglycerol [12]

Feedstock Ida Gold Pac Gold Rapeseed Canola Soybean Crambe

Calcium (ppm) 117 23 24 197 110 1633Potassium (ppm) BDL BDL BDL BDL BDL 2167Magnesium (ppm) 39 66 40 54 68 1267Phosphorus (ppm) 253 480 650 587 530 1367Sulfur (ppm) 210 160 210 140 BDL 1280Sodium (wt) 117 123 106 107 120 110Carbon (wt) 240 243 253 263 260 240Nitrogen (wt) 004 004 005 005 004 006

BDL indicates values that are below the detection limit for corresponding analyticalmethod The detection limits in ppm were as follows calciummdash2 potassiummdash40magnesiummdash020 sodiummdash80 phosphorusmdash5 sulfurmdash15 carbonmdash200 andnitrogenmdash100

Table 4Average viscosity and heat of combustion of crude glycerol from different feedstock[12]

Feedstock Ida Gold Pack Gold Rapeseed Canola Soybean Crambe

Viscosity at 40 1C (cP)Crude glycerol 880 867 850 846 865 850

HHV (MJkg)Crude glycerol 18600 19428 19721 20510 19627 19472

Fig 1 Molecular structure of glycerol [27]

Table 1Physical and chemical properties of glycerol

Properties Unit Morrison[38]

Pagliaro andRossi [39]

OECD-SIDS[40]

Molecular formula C3H5(OH)3 C3H8O3

Molar mass gmol 9209 9209382 92Relative density kgm3 1260 1261 1260Viscosity Pa s 141 15 141Melting point 1C 18 182 18Boiling point (1013 kPa) 1C 290 290 290Flash point 1C 177 160

(closed cup)160

Specific heat kJkg 2435 (25 1C)Heat of vaporization kJk-mol 8212Thermal conductivity W(m K) 028Heat of formation kJmol 6678Surface tension mNm 634 640 634pH (solution) 7Auto flammability 1C 393

CAG Quispe et al Renewable and Sustainable Energy Reviews 27 (2013) 475ndash493 477

pressure than would be expected for its molecular weight Lowvapor pressure is a characteristic of alcohols water and other polarcompounds and is the result of molecular association Glycerincauses less reduction in waters vapor pressure which can beexplained by molecular contraction an effect that is attributed tohydrate formation [30]

Many researchers report different values for glycerols LHVSoares et al [32] report a LHV (low heating value) of 1607 MJkgSilva and Muumlller [33] report 1618 MJkg Vaz et al [34] report LHVof approximately 190 MJkg while Thamsiriroj and Murphy [35]report LHV 192 MJkg for glycerol obtained as a byproduct of

biodiesel production using seeds and 1482 MJkg for glycerolobtained from fat residue Combustion heat of first use oils hasan average of 1956 MJkg which is around 10 higher than that ofpure glycerol which is 1796 MJkg [36]

Glycerols caloric value depends on the raw material that wasused to produce it It is twice that of fossil fuel but is comparablewith the combustion heat of most types of biomass such as woodstraw oilseed cake bark sawdust etc [37] Table 1 lists the mostimportant physical and chemical properties of glycerol

22 Characterization of crude glycerol

The term ldquoglycerolrdquo is only applicable to the pure chemicalcompound 123 propanotrial while the term ldquoglycerinrdquo normallyapplies to purified commercial products with contents of higherthan 95 glycerol They differ slightly in glycerol content and othercharacteristics such as smell color and traces of impurities [41]Many grades of glycerin are commercially available They areobtained after removing salts methanol and free fatty acidsMethanol is generally recovered by heating and reused in thebiodiesel production process In most commercial applications thequality of glycerin must be improved until it has an acceptablepurity that is completely different from those obtained in biodieselfacilities [1842]

There are many actions and processes used to purify biodieselrecover useful agents for re-cycling and process the byproductglycerol [43] An important post-process of glycerol includesacidificationneutralization to adjust pH and evaporationdistilla-tion to separate water and excess methanol for reuse Biodieselmanufacturers normally make an effort to recover excess non-reactive methanol However because recovery of methanol is lesscost effective than using new methanol this is not always the case[44]

Methylated glycerol contains 50 to 70 glycerol 10 to 20methanol 5 to 10 salts o3 to 10 water o1 to 5 fatty acidsand 5 non-glycerol organic material (NGOM) by weightDemethylated glycerol typically contains 70 to 88 glycerol

Fig 2 Worldwide use of vegetable oil for biofuel production [60]

Fig 3 Projection of global glycerol production and prices


o1 methanol 5 to 15 salts o5 to 15 water o1 to 5 NGOMby weight [45]

Table 2 shows an analysis of three types of glycerol Values forUSP grades are included for comparison All three types (USPmethylated and demethylated) contain significant levels of oxygen(52 43 and 17 by weight respectively) However the low valuemeasured for demethylated glycerol could indicate a reasonableconcentration and larger amounts of NGOM

Frequently the triglycerides contained in vegetable oil and orfat are now used as sources of biodiesel generating raw glycerin(or raw glycerol) which is the most common form that biodieselproducers sell [18] This low-grade glycerol also contains watersalt and other organic materials including residual methanol aswell as free fatty acids Each component varies quite a bit incontent depending on the raw material used [12]

Thompson and He [12] characterized glycerol obtained inbiodiesel production utilizing various raw materials finding thatthe glycerol content is in the area of 60 to 70 by weight Use ofmustard seed as a raw material generates lower glycerol (62)while using soybean oil as a raw material gives 678 glycerol Themethanol content was from 234 to 375 which is reflected in itslow viscosity Table 3 shows the analytical results of crude glycerolcharacterization while Table 4 shows the viscosity and LHV ofcrude glycerol obtained from different raw materials obtained byThompson and He

3 World glycerol production and market

World production of biofuels has been rapidly increasing forthe last decade Biodiesel production in the European Union hasgrown exponentially [121424] Among the main reasons for theincrease in production and demand of biodiesel is the increase inoil prices Global climate change and improving energy stabilityhave become a growing concern throughout the world Thebenefits for agriculture and rural regions are an opportunity toincrease economic development in many developing nations[4647]

But the viability of the first generation of biofuels has beenplagued with concerns about substituting food products effects onthe environment and climate change because it is mainly pro-duced from the harvest of food such as grain sugar cane andvegetable oil [9] The biodiesel economy as well as that of glycerolcould be influence by the way in which glycerol and otherbyproducts are utilized [48]

31 World biodiesel and glycerol production

The European Union has been producing biodiesel on anindustrial scale since 1992 [49] After 20 years of commercial usein Europe biodiesel has proven its value as an alternative fuel indiesel motors [5051] Crude glycerol production from theseprocesses has increased at the same rate and if sustainable growthis expected in the future it is assumed that there will be an excessof glycerol on the world market [52] In 2003 the European Unionwas the largest producer of biodiesel it produced 82 of thebiodiesel [53] in the world According to the European BiodieselCouncil EU production was 5 million metric tons (MMT) in 2006There had been a dramatic increase of 28 per year since the year2000 In 2006 world production was 10 million cubic meters ofbiodiesel [49] According to Oil Worlds estimate production was167 MMT in 2007 This significant growth took place mainly in theEuropean Union and the United States [49] Whats more Eur-opean Union Directive 200330CE stated that by the year 2010member nations were required to use 575 biofuel in theirpetroleum-based fuels used for transportation calculated basedon energy level [54] Application of this rule would lead to anincrease in biodiesel production which was estimated to reached10 MMT per year by the year 2010 meaning that 1 MMT ofglycerol would be produced per year [14] However an estimatefor 2008 showed that world biodiesel production reached 108

05

15

25

20

10

0

Jan-

92

Jan-

90

Jan-

88

Jan-

86

Jan-

84

Jan-

82

Jan-

80

Jan-

06

Jan-

04

Jan-

02

Jan-

00

Jan-

98

Jan-

96

Jan-

94

US

$kg

Fig 4 Historical prices of 995 refined glycerin (USP) [69]

Fig 5 Volatility of glycerol prices on global markets [67]


MMT 60 was produced by the European Union 20 by theUnited States and the remaining 20 by other producers Thisshows that the growth trend for biodiesel production and produc-tion deadlines were reached before the time forecast [55]

Finally in 2008 global production reached 111 MMT and globalcapacity reached 326 MMT [55] The world market for biodiesel isexpected to reach 37 billion gallons by 2016 an average growth of42 per year This means that around 4 billion gallons of crudeglycerol will be produced that year [56] In 2009 the EuropeanUnion reported production of 209 MMT two countries Franceand Germany produced more than 77 million tons However theEuropean Biodiesel Council (EBB) bases its data on capacitydeclared by the existing production facilities The real quantity ofbiodiesel produced is probably less [37]

According to the US Department of Agriculture global annualproduction of the main vegetable oils in 200708 reached 1288 MMTincreasing to 1339 MMT in 200809 In 200910 141 MMT wereforecast for 201011 it was 1486 MMT even reaching 1568 MMT for201112 and 15964 MMT in 20122013 [57] Whats more in smallproduction plants approximately 31 million tons of vegetable oil andanimal fat are produced and consumed each year [58] In 2009 USbiodiesel production exceeded 102109 L (27109 gal) on theother hand the US biodiesel industry reached a key milestone byproducing more than 1 billion gallons of fuel in 2011 according toyear-end numbers released by the EPA in January 2012 [59] Recentdecreases in the price of diesel and the slim margin it generates hashad negative effects on the biodiesel industry in such that it isestimated to be currently operating at less than 25 of this capacityHowever even with reduced utilization the glycerol market is nearlysaturated [44] Fig 2 shows statistics for use of vegetable oil from themain seeds to fabricate biofuel

In Europe glycerin comes from transformation activities basedon vegetable oil fat and animal tallow Crude glycerin in theUS mainly comes from biodiesel refineries In Asia glycerin isderived from vegetable oil The largest source in Malaysia andIndonesia is palm oil in the Philippines it is coconut oil [61]According to market research today the Asia-Pacific region is thelargest glycerin producer in the world [62] In 2007 Asia wasresponsible for more than 44 of world production and WesternEurope was the second producing around 35 These two regionsand the United States were responsible for at least 91 of worldproduction that year [63]

Global consumption of glycerol in 2008 was nearly 750thousand tons [64] In 2009 194000 t of glycerol were producedin the United States [65] Its been estimated for 2010 that plansannounced for biodiesel production would add 22 million tons ofglycerol to the current production in the United States andEuropean Union However for 2011 its been forecast that morethan 318 thousand tons of glycerin would reach the NorthAmerican market a 59 increase over 2009 production [65] Onereport forecast that world glycerin production should reach2 million tons in 2015 [62] Fig 3 shows world glycerol productionand price statistics for 2010

32 Biodiesel and glycerol consumption market

As biodiesel production has increased glycerol production hasgrown and saturated the market [66] In 2005 world glyceroldemand was estimated at 900 thousand tons [13] For 2007 Asiawas the largest consumer of refined glycerin with 25 of con-sumption Western Europe was the second largest refined glycerinconsumer with 28 of world consumption in 2007 North Americawas the third largest consumer These three regions accounted for82 of world consumption in 2007 [63]

Generally Europe imports refined and crude glycerin fromAsian countries It is considered a typical importer of this resourceThe United States is also a glycerin importer receiving productfrom Indonesia Malaysia Argentina and Europe Asia exports on alarge scale to global and regional markets and glycerin is a localend product In recent years China has surged in the market as alarge importer in addition to having local production [67] Whatsmore due to the growing petroleum and chemical industries inAsia much of the glycerin production had before been exported tothe United States but with growing freight costs most of thisproduction ended up going to China [68] The Asia-Pacific regionovertook Europe as the largest market in 2009 and is now thelargest regional market with the fastest growth in the worldpropelled by the increase in glycerin applications in varioussectors such as pharmaceutical personal hygiene food and bev-erage products There are lower importation rates in some Asianmarkets This market had predicted annual growth of about 33per year from 2007 to 2015 [62] New refined glycerin markets arealso largely responsible for projected growth of world demandfrom 2007 to 2012 and for 2012 Asia is still expected to be thelargest market due to increased demand for many applicationsincluding new markets for refined glycerin [63]

The worldwide glycerin market is known for its unpredictableand complex nature since it is a byproduct Production of thechemical is directly affected by the demand by various end-usesegments Demand for glycerin plummeted from 2008 through2009 because of a slump in the macro economy The negativeimpact of the recession was clearly evident in many regionsNevertheless the glycerin market is expected to recover by


20112012 and sustain growth in the ensuing years In additionusage of glycerin in various new applications is expected toimprove glycerin demand in the near term [62] However theglycerin market recovered in 2012 and sustains growth for thefollowing years It is expected that by 2016 China will account for27 of the worlds refined glycerin consumption [63] Thailandwill also experience high growth rates as a result of epichlorohy-drin production Both Indonesia and Malaysia will continue toexport large amounts of refined glycerin Japans refined glycerinconsumption growth is expected to remain flat in the next severalyears Overall Asian consumption will significantly increase to 45of the global refined glycerin total in 2016 [63]

33 Current world glycerin and glycerol prices

From the 1970s until the year 2004 high-purity glycerin had astable price between 1200 and 1800 US$ton Market and produc-tion conditions were stable (Fig 4) When prices were high usersreformulated their production with alternatives such as sorbitol orsynthetic glycerin while low prices encouraged the use of glycerinin other applications taking the place of petrochemicals Thisrelatively stable market has been drastically altered by the arrivalof biodiesel With stable prices there was no need to obtainhistorical glycerol prices for the savings of the biofuel industrybecause in the traditional petrochemical market the value ofglycerol was essential to maintain the business model Thoughthe petrochemical industry did know that biodiesel would succeedand the volumes would be large they were incapable of under-standing how effective it would be [13]

The subsidy policies and regulations proposed in the UnitedStates and the European Union for transportation fuel rose theproduction of biodiesel and its by product glycerol Growingamounts of glycerol began to be dumped onto a relatively stablemarket and in 2005 the stable prices went into free fall Thevolumes of glycerol were enormous and are growing

Most chemical companies involved in glycerol production hadproblems purifying it or eliminating it because of its high costwhich lead various businesses to close [3970ndash73] In Europewhere the market is very dynamic local production and importa-tion lead to an important role in defining prices [67] causing acollapse in the price of crude glycerol The price has fallen by afactor of 10 in recent years [66] The large amount of glycerollargely derived from palm oil in countries like Malaysia andIndonesia (the largest glycerol producers) played a part in theprice of glycerol falling to 33 cents per kilogram or less [6974]

In 2003 refined glycerin cost around 1200 US$ton In 2006the price stabilized around 600 US$ton with a strong falling trendbecause of growing biodiesel production (Figs 4 and 5) In 2006crude glycerin (80 glycerol) cost 125 euros per ton and wasforecast at 150 euros per ton for 2008 The price of crude glycerolalso fell in 2006 In the US crude glycerol was quoted between0 and 70 US$ton Most biodiesel producers assign a value of zeroto crude glycerol [13] Figs 3 and 4 show the historical evolution ofcrude glycerol and refined glycerin prices In 2011 the price ofcrude glycerol in the US is so low 2 to 5 cents per pound (4 to 11cents per kilogram) that many biodiesel producers are storingglycerol to wait for a better market [75]

However glycerol has shown to be a volatile commodity(Fig 5) with oscillating prices leading to questions about thestability of future glycerol production [76] In the United States theglycerol surplus obtained in biodiesel production forced producersto sell crude glycerol for 44 US$ton and even less In 2007 newuses of glycerol had pushed priced to 132ndash220 US$ton Refinedglycerin prices followed the trend with low prices wavering from440 to 660 US$ton depending on quality and purity While newuses for glycerin were expected to help consume the growing

volume of crude glycerin factors of supply and demand dictate theprice For example in the United States the market price for crudeglycerin fluctuated from 110 US$ton in January 2010 to US$ 330 aton in December 2010 [65]

At the end of 2010 it was speculated that domestic glycerinprices in the United States could reach 220 US$ton in the follow-ing months because of Asian and European producers with lowerprices than in the US In the northeast of Europe local stock pricesof vegetable glycerin were assessed at 462 to 506 US$ton In Asiavegetable glycerin was assessed at 506 to 550 US$ton CFR (costand freight) in the northeast of China Even with transportationprices foreign material might become more desirable and localglycerin values in the US might grow beyond present values In theMidwest of the United States vegetable glycerin was priced at 594to 682 US$ton free on board (FOB) [61]

For November 2012 glycerin from vegetable oil was quotedat 925ndash1080 US$ton and glycerin from animal fat between 892and 1069 US$ton while pharmaceutical USP grade glycerin wasquoted at 1410ndash1565 US$ton For the same year in Europe theprice of vegetable oil glycerin was quoted between 974 and1050 US$ton and animal fat glycerin from 860ndash924 US$ton Thereare differing opinions about the price of crude glycerin (80glycerol) with the majority of the estimates at a price from 500to 571 US$ton In Northeast Asia refined glycerin prices held at825ndash880 US$ton FOB while crude glycerin fell to the range from380 to 450 US$ton CIF in 2011 for 355ndash370 US$ton CIF in 2012The price of 80 pure crude glycerin obtained in biodieselproduction remained at 44 US$ton because it had been dumpedonto the market by the rapid growth of biodiesel productionGlycerin FOB in Southeast Asia was from 860 to 880 US$ton inApril 2011 for 795ndash860 in November 2012 [77]

4 The glycerol situation in Brazil

Brazil was one of the first countries to use clean energy(in order to reduce CO2 emissions) The government decided tosubstitute alcohol for gasoline in 1973 (Proalcool) In the mid1980s approximately 95 of cars produced in Brazil were retro-fitted to utilize ethanol as fuel In 2003 flex-fuel vehicles made upmore than 80 of new vehicles sold in Brazil The use of biofuelswill certainly continue to grow [78]

The Brazilian Biodiesel Technology Development Program(PROBIODIESEL) was created to bring about the gradual substitu-tion of diesel from petroleum with biodiesel [79] In 2004 theBrazilian federal government implemented the Brazilian BiodieselProduction and Use Program to add biodiesel to metropolitandiesel made from petroleum Beginning in 2008 all diesel sold hadto be made up of 3 biodiesel this percentage rose to 4 in 2009and 5 in 2010 [80] B20 a mixture of 20 biodiesel and 80diesel is scheduled for introduction in 2020 [81] Implementationof this program will cause a glycerin glut Its estimated that with4 biodiesel the glycerin surplus is around 264 thousand tons peryear and with the addition of 5 will reach 325 thousand tons peryear [80] Endless government incentives fuel the production ofbiodiesel which is being produced on a grand scale producing aglycerin surplus that is harming the biodiesel economy [82]

In the midst of this domestic biodiesel production scenariothe forecast for 2009 was that Brazil would produce around760000 m3 of biodiesel Production of 76000 t of glycerol wasexpected causing doubts that the excess of highly-pollutingglycerol produced might be irresponsibly disposed of in theenvironment [83]

But the forecasts were low since the glycerol volume producedin 2008 was more than 10000000 m3 as a consequence of theproduction of 12 million cubic meters of biodiesel needed to fulfill

Fig 6 Basic reaction of the saponification process [98]

H

H

H

H

H

C

C

C

OR

ORrsquo + 3 NaOH

ORrdquo

GlycerolBiodieselAlcoholTriglyceride

+

H

H

H

H

H

C

C

C

ORrsquordquo

ORrsquordquo

ORrsquordquo

H

H

H

H

H

C

C

C

OH

OH

OH

Catalyst

Fig 7 Stoichiometric reaction of triglycerides and alcohol [102]

Reactor

Mineral Acid

Biodiesel

Glycerin

+ water+ saltsFatty Acids

Settler Neutralization Washing Evaporation

Glycerin Purification

Mineral Acid

Vegetable Oil

Methanol

Catalyst

Water

Fig 8 Global scheme for a typical continuous homogeneous catalyzed process [6]


legislation that established the addition of 2 biofuel to commondiesel [84] In 2010 transesterification of oil and fat in Brazilproduced 24 million cubic meters the equivalent of around24000000 m3 of aqueous glycerin [85] In 2011 there is a surplusof 100000 t of crude glycerol In 2011 had been predicted that in2013 when the mixture of biodiesel is obligated to rise from 4 to5 250000 t of crude glycerol will be produced [86] Today(March 2013) the production of biodiesel is about 275 millioncubic meters which suggests that there is a production ofapproximately 275000 m3 of glycerol [85]

According to the Brazilian Industrial Chemistry Association(Abiquim) in 2008 there was a working capacity of the domesticglycerin industry of around 415 million liters for a demand thatwas no more than 30 million liters For 2009 glycerin productionclosed at around 160 million liters and for 2010 production of 230million liters is forecast [87]

Meanwhile prices follow the international trend At thebeginning of 2007 the value of crude glycerol (of differentgrades) obtained from biodiesel production was between 114and 228 US$ton [88] The price of crude glycerin in 2008 wasaround 62 US$ton bi-distilled (96) was 123500 US$ton whilepharmaceutical USP grade glycerin (4995) was brought tomarket for 147000 US$ton [89] Since crude glycerin produc-tion is greater than internal demand is able to process todaycrude glycerol is exported to China for prices that vary from 50 to70 US$ton The great challenge facing Brazil will be to incenti-vize biotechnology research This has been timidly developed inthe country In addition the immediate transfer of new techno-logical discoveries the biodiesel mills themselves must befacilitated This will allow transportation costs for convertingto biodiesel to be reduced and will make biodiesel a highlyprofitable biofuel [88]

Biodiesel

Methanol

Vegetable oil

gt98 Glycerin

Full MeOH evap

Glycerin Glycerin

Partial MeOH

evap

Partial MeOH

evap

R2R1

Fig 9 Simplified flow chart of the heterogeneous process [6]


5 Biodiesel and glycerol production technology

Biodiesel production results in a relatively large amount ofbyproducts and residue such as gluten flour gluten pulp wastewater and crude glycerol [90] Glycerol is the main componentin all fats and oil and the main by-product with added valueproduced from oil and fat by means of saponification and transes-terification carried out during oil and chemical processes inbiodiesel production [3791189293ndash96] Glycerol is produced intwo ways natural glycerin (as a by-product of soap production orfatty acid methyl esters such as biodiesel) and synthetic glycerolNatural glycerol is initially produced in a raw form that containswater and other residues as impurities depending on the produc-tion process Generally glycerin is obtained as a byproduct whenbiodiesel is produced by transesterification [97] Crude glycerin isobtained as a result of this process It is the form of glycerin that ismost sold by biodiesel producers [18]

51 Hydrolysis

Fat and oil are triglycerides and can undergo basic or alkalinesaponification Acidic saponification simply produces glycerol andthe fatty acids that make it up while basic saponification producesthe salts of these fatty acids (Fig 6) Soap is generally produced asa result of a chemical reaction between a strong base (generallysodium hydroxide or potassium hydroxide) and some fatty acid

The essence of soap production is the saponification reactionIn saponification sodium hydroxide or potassium hydroxide reactwith triglycerides knocking off glycerol and forming soda orpotassium salts which we call soap Fatty acid is also called soapGlycerin is extracted from soap with lyemdasha brine solution that isadded to the soap at the saponification stage Wet soap is solublein weak brine but separates out as the electrolyte concentrationincreases Glycerine on the other hand is highly soluble in brineWet soap thus has quite a low electrolyte concentration and isabout 30 water (which makes it easily to pump at 70 1C)To remove the glycerin more electrolyte is added causing the wetsoap to separate into two layers crude soap and a brineglycerinmixture known as spent lye neutral lye or sweet waters [98]

52 Transesterification

Biodiesel is typically produced by the transesterification reac-tion of different triglycerides When the triglycerides are stimu-lated by a catalyst they react chemically with alcohol generallymethanol or ethanol to produce methyl ester biodiesel and ethyl

ester glycerol [1199ndash101] Biodiesel is made using transesterifica-tion in three reactions in which di and mono-glycerides areformed as intermediaries Transeterification of triglycerides inFatty Acid Methil Esters (FAME) is a catalyzed and balancedreaction in which one mol of triglycerides reacts with three molsof methanol (Fig 7) Though the general stoichiometry of thereaction requires three mols of alcohol for each mol of triglycer-ides an excess of alcohol is needed in the reaction medium toforce the reaction and obtain a high yield [697] Most industrialprocesses in biodiesel production use a 6 to 1 M ratio of alcohol tooil with an excess of 100 of alcohol in order to complete thereaction

The majority of the excess alcohol (up to 80) ends up in theglycerol layer after the reaction Producers recover the alcohol toreuse it [103] Among the different types of catalysts studied forthe transeterification reaction the most common are alkalinebases The main examples are alkaline earth metal hydroxides oralkoxides of sodium or potassium However transesterification canalso be carried out using acidic catalysts such as hydrochloricsulfuric or sulfonic acid or using metallic base catalysts such astitanium alcoholates or magnesium tin zinc and aluminum oxide[6104105]

Generally in conventional biodiesel industrial processes (Fig 8)methanolysis of vegetable oil is obtained using a homogeneouscatalyst frequently sodium hydroxide and sodium methoxide[106] The catalyst is applied either to a load of the raw materialor continuously

Sodium is recovered after the transesterification of sodiumglycerate sodium methylate and sodium soaps in the glycerolphase The salts must be neutralized with an acid neutralizationstep with aqueous hydrochloric or phosphoric acid for exampleIn this case glycerol is obtained as an aqueous solution containingsodium chlorate Depending on the process final purity of glycerolis around 80 to 95 When sodium hydroxide is used as a catalystthere are generally collateral reactions forming sodium soap Thistype of reaction is seen when sodium methoxide is employed andthere are traces of water Sodium soap is soluble in the glycerolphase and must be isolated after neutralization by decanting thefatty acid Loss of esters converted to fatty acids can reach up to 1in biodiesel production [6107] In transesterification since anexcess of methanol is added two phases are formed one richin methanol and one rich in biodiesel Glycerin is distributedbetween the two phases though it is more prevalent in themethanol phase However when ethanol is used separating thephases of the final products is complicated Methanol is used moreoften and is totally justified both physically and chemically due to

Fig 10 Types of glycerin and how they are obtained [112]

Table 5Quality specifications for each grade glycerin [112]

Properties Crudeglycerin

Technical gradeglycerin

997 USP gradeglycerin

Glycerol content 40ndash88 980 Max 9970Ash 20 Max NA NAMoisture content NA 20 Max 03 MaxChlorides NA 10 ppm Max 10 ppm MaxColor NA 40 Max (PtmdashCo) 10 Max (APHA)Specific gravity NA 1262 ( 25 1C) 12612 minSulfate NA NA 20 ppm MaxAssay NA NA 99ndash101 (dry)Heavy metals NA 5 ppm Max 5 ppm MaxChlorinatedcompounds

NA 30 ppm Max 30 ppm Max

Residue on ignition NA NA 100 ppm MaxFatty acid amp ester NA 100 Max 10 MaxWater 120 Max 50 Max 05 MaxpH (10 solution) 40ndash90 40ndash91 NADEG and relatedcompounds

NA NA Pass

Organic volatileimpurities

NA NA Pass

Organic residue 20 Max 20 Max NA

ppmmdashparts per million NAmdashNot applicable

Fig 11 Traditional glycerol uses with average worldwide values [37]


the short polar chain Recently ethanol has become more commonbecause it is less aggressive than methanol and since it is renew-able This process is still in the research development andoptimization phase [108]

The increase in biodiesel production began a search for solidacids or basic catalysts that could be used in biodiesel production[6107109] Some solid metal oxides such as tin zinc andmagnesium are known catalysts They react according to ahomogenous mechanism and end up as metal soap or metallicglycolates In this continuous process the transesterification reac-tion uses a completely heterogeneous catalyst made up of amixture of zinc and aluminum oxide which develops the reactionwithout losing catalyst The reaction is carried out at a lowertemperature and pressure that those with a homogeneous cata-lysis though with excess methanol This excess is removed byvaporization and recycled for the process Chemical conversion isreached with two successive stages of reaction and glycerolseparation in place of the balanced reaction (Fig 9)

The catalysis section included two fixed bed reactors fed withvegetable oil and methanol in the given proportions The excess ofmethanol is removed after each reaction by partial evaporationNext the esters and glycerol are separated in a decanter Glyceroloutlets are united and residual methanol is removed by evapora-tion In order to obtain biodiesel in the specifications desiredthe last traces of methanol and glycerol have to be removedThe methyl ester purification section of the outlet from decanter2 consists of a final vaporization of methanol in a vacuum followedby final purification in an absorber to remove soluble glycerol[6107]

53 Refining crude glycerol

Independent of whether animal or vegetable fat a mixture ofanimal and vegetable fat or synthetic fat are used as the sourcein most applications crude glycerol is refined before its finalutilization to obtain a higher degree of purity [1863] Averagecomposition of crude glycerol generally oscillates between 40 and70 glycerin 10 water (in the range of 8ndash50) 4 salt (from 0 to10) less than 05 methanol and approximately 05 free fattyacids [3769] Despite the many applications for crude glycerol inpharmaceutical food industrial and cosmetic products refiningcrude glycerol to a high degree is very expensive especially forsmall- and medium-sized biodiesel producers [1218110111]Crude glycerol is generally treated and refined by filtrationchemical additives and fractioned distillation in vacuum to pro-duce various types of glycerin It can also be refined by a methodusing lower-energy intensive filtration by a series of ion exchangesin resin [102] The approximate cost of crude glycerol is 033 US$kg [75] and 058 US$kg to obtain more pure glycerin

There are three basic types of refined glycerin based on theirpurity and potential end use They are (a) ldquotechnical graderdquo usedas a building block in chemical products not used for the creationof food and medicine (b) United States Pharmacopeia (USP)glycerin from animal fat or sources of vegetable oil appropriatefor food and pharmaceutical products and (c) Food ChemicalsCodex (FCC) glycerin from vegetable oil sources appropriate foruse in food (Fig 10) Glycerin is normally sold 995 to 997 pureThe majority sold today is made to meet the rigorous requirementsof United States Pharmacopeia and Food Chemicals CodexConventional uses and present market capacity cannot absorbthe surplus of crude glycerin Additional more-expensive purifica-tion is needed to obtain industrial grade (tech glycerin) that is 98pure which is also available on the market [113] Quality specifi-cations of various types of glycerin are shown on Table 5

Later refining of crude glycerol will depend on the economy ofscale of production andor the availability of a purification instal-lation Large biodiesel producers refine their raw glycerol anddistributed it in the markets of the food pharmaceutical andcosmetic industries [114]


6 Alternatives for the use of glycerolmdashNew trends

The properties of glycerin have created a versatile range ofproducts Up to the year 2000 there were more than fifteenhundred end uses in the chemical industry [115] At present it isestimated that there are more than two thousand uses for glycerolHowever in the majority of products it is only used in smallquantities There are few end uses that need large amounts ofglycerol in their formula Uses vary from energy bars to coughsyrups to sealants for ships The three main uses for refinedglycerin are food products personal hygiene products and oralhygiene products making up about 64 of total consumption(Fig 11) For a long time consumption of oil and fat was dividedamong food animal feed and industrial use at a 80614 rationbut with the increase in biodiesel production this is probablycloser to 74620 now and is expected to reach 68626 in 2020[116] showing that industrial usage has been growing inrecent years

Crude glycerol has a low value because of the impurities Enduse of glycerol varies depending on the raw material and thebiodiesel production process [12] If crude glycerol is utilized toproduce glycerol derivatives it will be more valuable [117] andhelp to improve economic viability of the biodiesel industry and atpresent alternatives uses of crude glycerol are being sought

Due to the large surplus of glycerol formed as a by-productduring the production of biodiesel new opportunities for convert-ing glycerol into value-added chemicals have emerged in recentyears which will definitely promote the commercial viability ofbiodiesel and further development Glycerol can be converted intopromising commodity chemicals and fuels through chemicallyselective catalysis such as selective oxidation selective hydroge-nolysis catalytic dehydration pyrolysis and gasification selectiveglycerol transesterification and esterification selective etherifica-tion and carboxylation and other processes [56] Thus there hasbeen an ample field of research in order to find new applicationsfor this raw material at the low cost expected [15118]

Selective oxidation processes include (1) oxidation of primaryhydroxyl groups which yields glyceric acid and also tartronic acid(2) oxidation of the secondary hydroxyl group which yields theimportant fine chemical dihydroxyacetone (DHA) or ketomalonicacid and (3) oxidation of all three hydroxyl groups which yieldsthe highly functionalized molecule mesoxalic acid [56] Extensiveresearch concerning selective catalysis of glycerol to produceglyceric acid [119ndash125] DHA [126ndash130] and mesoxalic acid wasconducted All the functional derivatives obtained have commer-cial value For instance DHA is the main active ingredient in allsunless tanning skincare preparations and might be a buildingblock of new degradable polymers if the market price is lower[131132] Mesoxalic acid is a potentially valuable chelating agentthat can be used as intermediate compounds for the synthesis offine chemicals and novel polymers [56]

Catalytic conversion gives propylene glycol propionic acidacrylic acid propanol propanediol [133ndash136] citric acid sophor-olipids and other products [15137] Selective hydrogenolysis ofglycerol in the presence of metallic catalysts and hydrogen canproduce 12-propanediol (12-PD) 13-propanediol (13-PD) orethylene glycol (EG) 12-PD is used for polyester resin liquiddetergent pharmaceuticals cosmetics tobacco humectants fla-vors and fragrances hygiene products paint animal feed anti-freeze etc 13-PD is used in specialty polyester fibers films andcoatings EG is a raw material for synthetic fibers and explosives[138]

Catalytic dehydration of glycerol can produce acrolein which isa versatile intermediate largely employed by the chemical industryfor the production of acrylic acid esters super absorbent polymersand detergents [56139]

Pyrolysis and gasification of glycerol were also found by manyresearchers to generate CO H2 Glycerol is a readily digestiblesubstance that can be easily stored for a long time The relativelyhigh energy content in the crude glycerol phase also makes it aninteresting substrate for catalytic reforming resulting in hydrogenand carbon monoxide called syngas by steam reforming insmaller reactor volumes [32140ndash143] and production of H2 byreforming glycerol [142] Is used in production of fuel oxygenateAcetal (22-dimethyl-13-dioxolan-4-yl) [144]

Selective glycerol transesterification and esterification canyield monoglycerides (MG) and polyglycerol esters (PEG) MGcan be applied as emulsifiers in the food pharmaceutical andcosmetic industries [145] Melero et al [14] reported theesterification of glycerol with acetic acid to produce glycerineacetates such as diacetylglycerol (DAG) and triacetylglycerol(TAG) which have been shown to be valuable petrol fueladditives leading to either enhanced cold and viscosity proper-ties when blended with diesel fuel or antiknocking propertieswhen added to gasoline A glycerol-based fuel additive glyceroltertiary butyl ether is an excellent additive and there is a lot ofpotential for diesel to be synthesized via etherification ofglycerol [146ndash148]

Selective etherification of glycerol can yield more valuable fueladditives or solvents with suitable properties Among these tert-butyl ethers exhibit potential for use as diesel fuel additives ingasoline They offer an alternative to oxygenates such as methyltert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) Selectiveetherification can also convert glycerol into polyglycerol (PG) andPEG which have been recommended to be used as biodegradablesurfactants lubricants cosmetics food additives [149ndash151]

Carboxylation of glycerol can produce glycerol carbonate A lotof attentions have been given to this new and interesting materialin the chemical industry [152ndash154] Inexpensive glycerol carbonatecan be utilized as source of new polymeric materials

New applications have been found in the polyglycerol polycar-bonate and polyurethane industry in the field of stabilizing wood andproduction of small molecules such as glyceric acid hydroxipyruvicacid and glycerol carbonate [155156] Recently the production of 13-propanodiol (13-PD) or trimethylene glycol (TMG) is gaining increas-ing importance due to its role as a monomer in polyester synthesisprocesses for tissues and textile applications which require a largeincrease in the production of this product [157]

Glycerol can also be used to prepare dichloropropanol (DCP)[158] and as substrate to produce organic solvent tolerant lipase[159] Polypropylene can be made from glycerin This plastic isused in vehicles appliances disposable syringes cleaning pro-ducts etc [160]

In biological conversion many known microorganisms cannaturally utilize glycerol as their only source of energy and carbon[92161ndash163] utilized in biological methane production from crudeglycerol by anaerobic digestion [28109] The higher level of sugarreduction allows reduced chemical products to be obtained suchas succinate ethanol xylitol propionate and hydrogen at higheryields than those obtained using sugar [39]

As it has been mentioned glycerol can also be used inconversion to chemical commodities (such as propylene glycolpropionic acid and isopropanol) It is also used in fertilizers [29]and as a carbon source for bioreactors treating Acid Mine Drainage[164] In Agricultural usage there are other advantages thatinclude low need for nutrients energy savings and generation bystabilized digestors that improve soil quality [143]

Glycerol from biodiesel might be used as an energetic supple-ment for cattle [29] It also has the potential use as an ingredient invarious stages of production of Broiler feed [165] and pig feed[165ndash170] Roger et al [166] report successfully including glycerinfrom biodiesel at low concentration in animal feed

Table 6List of various applications of glycerol

Products Process Uses Major research

Hydrogen Steam reforming partial oxidation auto thermalreforming aqueous-phase reforming andsupercritical water photofermentation using aphotosynthetic bacterium

New fuel and energy carrier that could be used inthe transport sector power generation chemicalindustry photovoltaic cells

Adhikari et al [142] Slinn et al [172] Byrd et al[173] Sabouring and Hallenbeck [66] Ito et al[174] Huber et al [175] Wen et al [176] Zhanget al [177] Caetano and Silveira [178] Pagliaroand Rossi [179] Wena et al [180] Menezeset al [181] Cortright et al [182] Tuza et al[183] Wang et al [184] Kamonsuangkasemet al [185] Gutieacuterrez et al [186] Reungsanget al [187] Lin [188]

Fuel additive aReactive of glycerol with acetic throughacetylation or esterification process Reaction ofglycerol with ether substrate throughetherification process Reaction of glycerol withacetone and acid anhydride through acetalationprocess Glycerol fermentation by Clostridiumpateuriunum

These products may have suitable properties foruse as solvents or additives in gasolinepetroleumengines without changes in design Uses as brakefluids as perfume based as paint thinner andhydraulic fluid

Beatrice at al [171] Karinen and Krause [189]Noudreddini et al [190] Kiatkittipong et al[191] Fernando et al [192] Rahmat et al [24]Garcia et al [144] Melero et al [14] Meleroet al [193] Klepakova et al [194] Ferreira et al[195] Agnieszka et al [196] Clacens et al [149]Klepakova et al [197] Richter et al [198] Tranet al [199] Alhanash et al [200] Chiu et al[201]

Methanol Via synthesis gas Chemical feedstock medical and industrialapplication

Gutieacuterrez et al [202] Goetsch et al [203] Tsanget al [204] Duan et al [205]

Ethanol Bioconversion of raw glycerol (glycerolfermentation by E coli

Used as fuel in the space industrial andtransportation sector Largely use in alcoholicbeverages medical applications and chemicalfeedstock

Yazdani and Gonccedilalves [17] Ito et al [174]Posada and Cardona [206] Oh et al [207]Amaral et al [208]

Animal feed ndash Cow and other animal feed pigs diet poultryfeed Animal nutrition industry

Dedrain et al [209] Cerrate et al [165] Donkinand Doane [168] Donkin et al [210] Carvalhoet al [211] Oliveira et al [212] Schieck et al[213] Li et al [214] Roger et al [166] Chunget al [215] Kansedo et al [216] Ferraro et al[217] Wang et al [218] Fisher et al [219] Casaet al [220]

Food ndash Preservation sweeteners and thickening agent Irieb [221] Lee et al [222]Acrolein aGlycerol conversion Detergent super absorber acrylic acid polymers Rahmat et al [24] Watanabe et al [223] Corma

et al [224] Zhou et al [225] Tsukuda et al[226] Ning et al [227]

minus on hot compressed waterminus by micro- and mesopourus ZSM-5minus Over activated carbon-supportedminus Over silica-supported heteropolyacid

Reaction gas phase glycerolwater mxture byzeoliteSilicotungstic acids

Chemicalindustryproducts

bGlycerol fermentation by klepsiella PneumoniaecGlycerol selective dehydroxylation bGlycerolhydrogenolysis dGlycerol with CO2 (glycerolcarbonate) Glycerol with heteropolyacid (DCP)glycerol with hidrocloric acid catalyzed by aceticacid as acid catalyst

minus Polymer industry (use as monomer in thesynthesis of several polyester and polymersunsaturated polyester)

minus Plastic industry (polyglycerol methacrylates)minus Textile industry (as a substitute for

petroleum-based polypropelene sizing andsoftening to yarn and fabric)

minus Explosives industry (nitroglycerin)mdashAntifreeze liquid

minus - Additive for liquid detergent

Rahmat et al [24] Cardona et al [228] Wanget al [229] Gong et al [230] Rosa et al [231]Villamagna and Hall [232] Pagliario [15] Arestaet al [154] Lee et al [158] Lee et al [233]

Pharmaceuticalproducts

Glycerol oxidation for produce Dihydroxyacetoneand crude glycerol with microalgal culture (DHA)

Used as a tanning agent in cosmetics industriesadditive in drugs love potion healthsupplements and nutrient

Stella [234] Bauer et al [235] Pollington et al[236] Demirel et al [237] Ciriminna et al[129] Chi et al [238]

Biogas Co-digested in anaerobic digesters syngasproduction

Fuel Skoulou et al [239] Robra et al [240] Amonet al [241] Siles et al [242] Fountoulakis andManios [243]

a Adapted by Rahmat et al [24]b Cardona et al [228]c Wang et al [229]d Aresta et al [154]


Another possible use is as boiler fuel to reduce the thermalenergy in the transesterification andor cogeneration to produceelectricity Directly burning glycerol could be a possible use forlarge quantities without needed to refine it This point will bedealt with below

To sum up glycerol can be converted into many value-added products through catalytic processes However there are

additional challenges since the glycerol obtained as a by-productfrom the biodiesel industry is crude and impure Zhou et al [136]stated the following four challenges that must be faced in theirreview article (1) New application and products for directly usingcrude glycerol need to be found (2) A cost effective purificationprocess needs to be developed to purify crude glycerol frombiodiesel processes (3) There separation of crude glycerol must

Table 7Fuel characteristics [253]

Properties Unit 100 Glycerin 10 Glycerin90 YG

Saybolt Viscosity (378 1C) mm2s (cP) 4438 (5559) 5248 (488)Specific Gravity (156 1C) 1252 0929Flash Point 1C 4120 199Ash Mass 3805 043Carbon Mass 328 7033Hydrogen Mass 856 1132Nitrogen Mass o02 o02Oxygen (by difference) Mass 5455 1770Total Sulfur Mass 0085 001Total Chlorine μgg 1815000 241000Mercury μgg o01 o002 Water (Karl Fisher) mass 1255 146Calorific Value MJkg 1461 3796

Table 8Summary of emissions tests results [253]

Pollutant Unit Results

PM10PM gNm3 458kgh 227

Nitrogen oxides ppm 10895kgh 162

Carbon monoxide ppm 20kgh 002

Sulfur dioxide ppm 2039kgh 042

VOCs ppm 1186kgh 005

Sulfuric acid mist ppm 010kgh 0003

Calcium kgh 006Potassium kgh 0012Magnesium kgh 0008Phosphorus kgh 0045Hydrogen chloride kgh 0015Chlorine kgh 0002Acrolein kgh o00036Acetaldehyde kgh o00036


be combined with catalytic conversion and (4) direct bio-catalyticconversion using crude glycerol should be investigated and devel-oped to make it economically practical

Etherification of glycerol with tert-butyl alcohol and isobuty-lene allowed to Beatrice et al [171] to identify the suitableexperimental conditions required to obtain a mixture predomi-nantly composed of higher glycerol ethers These researchersstudied the processes for converting glycerol in an oxygenatedfuel additive (glycerol alkylndashether) suitable for blending withdiesel and biodiesel

Next Table 6 presents a summary of the main applications ofglycerin its processes uses and major investigations (other morethan those already mentioned) conducted with each application

61 Glycerol combustion

The main energy generation and atmospheric pollution emis-sions problems facing the world come from burning fossil fuel incombustion chambers Industrial combustion is defined as achemical reaction in which an oxidant (oxygen generally takenfrom atmospheric air) reacts with a specific reducer (fuel) in anexothermic reaction (producing energy) Standard dry air is madeup of approximately 2315 oxygen and 7685 inert gas nitrogenamong them [244] Other combustion products can also beformed such as NOx from oxidation of nitrogen Most conventionalfuel also contains small quantities of sulfur (S) which is oxidizedduring combustion forming sulfur dioxide (SO2) or sulfur trioxide(SO3) Fuels can even contain substances that are not oxidantssuch as mineral material (ash) water and inert gas

Glycerol is biologically produced renewable and biodegrad-able Its production process is associated with the green refiningindustry which is a great environmental value as well as encoura-ging independence from fossil fuel [24] Its use including burningit as fuel does not increase atmospheric pollution globally The useof glycerol as a fuel in industrial processes has several advantagesBurning industrial glycerol has shown itself to be the simplestmethod of using crude glycerol It is also advantageous since itdoes not require any purification If combined with biodieselproduction this alternate energy would have additional advan-tages in energy integration eliminating the cost of transportationand use of fossil fuels [245]

Though it is known that glycerin has a moderate calorific level(sim16MJkg) it has not yet been used as a fuel [244478171246ndash249]The stoichiometry for burning glycerol is [37]

C3H5ethOHTHORN3 thorn 35O2-3CO2thorn4H2O 1655 kJ=mol

However crude glycerin production process is not easy fromthe technological point of view Some of the difficulties of burningglycerol cited by researchers [44245] are (a) it has a low calorificvalue which makes it incapable of maintaining a stable flame in aconventional burner as well as being harmed by the water in themixture (b) it has a high self-ignition temperature approximately370 1C in comparison to gasoline 280 1C and kerosene 210 1C(c) burning glycerol can form acrolein (d) it is highly viscous atroom temperature (kinematic viscosity approximately 450 cSt)making it hard to atomize with conventional atomizers (e) its saltcontent causes corrosion problems in burner injectors and in post-combustion systems and is also a flame inhibitor which makes itdifficult to burn glycerin

Glycerols calorific value depends on the raw material used toproduce it varying from 186 to 205 MJkg using different oilyseeds [12] The heat of combustion is half those of fossil fuels butis comparable with other types of biomass such as wood strawoilseed cake cane cake bark and sawdust Its calorific value is lowbecause of the relatively large amount of water that it is obtainedwith Glycerol has not yet been co-burned on a large scale with

other liquid or solid fuel [37] Based on its ignition point directthermal use of crude glycerol is an obvious choice Studies havereported that co-burning of crude glycerin with other biomass hadfavorable results [12] An attractive and relatively simple option forglycerol it to use it as furnace fuel to produce heat and electricity[250] According to DAF [251] and Bombos et al [252] modernboilers are designed to withstand high thermal loads in thefurnaces so using glycerol directly in existing boilers is unaccep-table because of the high ignition point and low adiabatic flametemperature Today the most common use of crude glycerin isincineration [251] Thus assuming that crude glycerin has anaverage calorific value of 185 MJkg and an average cost of 10cents per kilogram the thermal energy produced would have anaverage cost of 00054 US$MJ which is a little less than theequivalent value in natural gas today However this is consideredthe least valuable way to use glycerin since it does not add value tobiodiesel production and is sold at the price of an industrial by-product The cost of biodiesel has two aspects the raw materialfeedstock cost and production cost The recovery of the by-productglycerol makes a significant contribution to the latter

Glycerol has a high self-ignition temperature which meansthat more activation energy is needed for the oxidation reactionGenerally standard combustion burns with a single spark generat-ing a self-sustaining flame but glycerol wont self-ignite in theseconditions Even if there is an open flame near a spray of glycerolthe droplets that pass through the flame burn but do not


Pollutant Unit Results Process parameters

Combustion of demethylated glycerin (80 glycerol) Glycerin consumption 13 kghParticulate matter gm3 119 Load 45 kWNitrogen oxides ppm 88 O2 24 vvCarbon monoxide ppm 73 Coefficient of excess air 113Sulfur dioxide ppm 10 Pressure before atomizer 28 barCombustion of stable glycerol emulsion Emulsion consumed 6 kghParticulate matter gm3 05 Load 37 kWNitrogen oxides ppm 277 O2 36 vvCarbon monoxide ppm 100 Coefficient of excess air 118Sulfur dioxide ppm 993 Pressure before atomizer 10 bar

Table 10Emissions measured from 7 kW prototype burner and 82 kW refractory-lined furnace [44]

7 kW prototype burner 82 kW furnace

USP Glycerol (168 kgh) Propane (0576 kgh) Diesel (0618 kgh) Methylated Demethylated

Load (kW) 73 73 73 74 74 73 73 805 539Φ a 0444 0392 037 0562 0488 0645 0488 063 077SRa 225 255 271 178 205 155 205 158 13NOx (ppm) 3 35 36 602 628 747 625 1465 1183NOx at 0 O2 (ppm) 69 91 96 1105 1354 1178 1286 2352 1555O2 ( vv) 118 129 133 96 113 77 108 79 51CO2 ( vv) 73 67 63 68 59 7 62 125 154CO ( vv) 0 001 0 001 0 0 0 ndash ndash

THC (ppm) ndash ndash ndash ndash ndash ndash ndash 47 71Exit temp (1C)b 958 901 877 1001 974 986 946 1041 1075Flame temp (1C)c 1201 1103 1060 1359 1213 1628 1343 1782 1716

a Equivalence and stoichiometric ratios determined by excess O2 in the exhaustb Temperature measured at the throat of the exhaust for the 7 kW prototype burner and the exhaust of the 82 kW refractory-lined furnacec Adiabatic flame temperature calculated at stoichiometric ratios listed above

0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600

75 Glycerol 25 water80 Glycerol 20 water85 Glycerol 15 water90 Glycerol 10 water95 Glycerol 5 water

Fig 12 Viscosity of glycerol and aqueous solutions of glycerol as a function oftemperature


emit enough energy to maintain a continuous combustionreaction [245] In addition if there is water present it makes thecombustion of crude glycerol very difficult since it shuts off theflame in the burner and generates a large amount of black carbonIn practice special burners must be designed to carry out theco-combustion of glycerol with other liquid fuel [379144245]Co-burning with other fuels that is easier to ignite would help theignition process and sustain the flame [256]

Its been reported that burning crude glycerol derived fromsoybean oil with yellow grease made up mostly of used cooking oilbecause of the size of a 1970 Kewanee 750 HP industrial fire-tubeboiler [253] Waste glycerin was mixed with waste biomass toproduce combustible pellets as an alternative to coal for energy

production [254] Patzer [253] reported that crude glycerin used insmall amounts as a mixture taking into consideration the price on theinternational market that it could be a viable fuel but not whenanalyzed only as a fuel He reported that glycerin could maintain astable flame and had a lot of mineral salt emissions that corrodeequipment and reduce its life span Table 7 shows the basic physicaland chemical characteristics of the fuel used by Patzer [253] FinallyTable 8 shows the summary of the combustion results They are theaverage of three samples taken at different times during the test

Stiurgas [255] studied the possibility of using commercialglycerin (80 glycerol) along with stable emulsions of glyceroland heavy oil According to this author the final stable emulsionwas made up of 13 sodium oleate or soap 3 monoglyceride fattyacid 8 methanol 265 methyl ester (biodiesel) 272 glyceroland 34 heavy fuel oil The combustion system used was modifiedthe adiabatic combustion chamber was pre-heated to 100000 1Cusing natural gas a modifier burner 40 bar fuel pump the fuel waselectrically heated to between 60 and 85 1C and a cyclone to collectand analyze particulate matter Table 9 shows a summary ofcombustion results obtained by Stiurgas [255]

Metzger [245] also utilized modified equipment for directglycerin burning using a 7 kW vortex-type burner and an adiabaticcombustion chamber to improve burn and flame stability Thisauthor used laboratory grade glycerol (USP glycerol) methylatedglycerol and demethylated glycerol as fuel

Bohon [44] continued Metzgers work and improved the burnerhed used before Through elaborate computer simulationscalled Computational Field Dynamics CFD Bohon [44] improvedinsulation operation and experimental usefulness of the burner bydiminishing loss and improving stability of the glycerin flame Healso used Metzgers 7 kW burner [245] and an 82 kW vortex typeburner linked to a small refractory furnace The tests were carriedout using glycerol USP methylated glycerol and demathylated


glycerol as fuel Table 10 shows the results obtained by Bohon et al[44]

Acrolein is a product of thermal decompositions of glycerolwhen it is heated between 280 and 300 1C which is well belowglycerols self-ignition temperature [251] Acrolein is toxic in verysmall quantities around 2 ppm and some studies suggest humanhealth risk with concentrations as low as 009 ppm Acrolein isincreasingly unstable at high temperatures and highly flammabletotally consumed between 930 and 100000 1C [256] Its concei-vable that an efficient glycerol flame could consume any acroleinproduced before combustion gases are used up in the environment[245257ndash259]

Pure or refined glycerol is highly viscous which makes theatomization process difficult at room temperature [245] Glycerolsviscosity could be drastically reduced by directly heating it orheating it with steam [258] (Fig 12) which are the most commonmethods used in the combustion process The viscosity ofuntreated crude glycerol obtained from biodiesel production usingoilseed varies from 846 to 880 cS [12] Crude glycerol can containalcohol and water and have a lower viscosity but producers preferto evaporate it to recover the alcohol for reutilization Whenglycerol is mixed with water its viscosity is much lower [27] anddepending on the quantity of water (for example 20 by weight)reduction of viscosity can be dramatic (Fig 12)

The remaining menthol and sodium and potassium salt andother impurities must be analyzed because they are known toinhibit various processes [130260] Compared to liquid fossil fueltechnical glycerol (minimum 98 glycerol) has a higher mineralcontent [113] Mineral compounds sometimes found in glycerolare sodium or potassium chlorates potassium sulfate or potas-sium phosphate Compounds based on alkaline metals Na and Khas high fusion and softening temperatures As a result theconditions in which glycerol burns have a great potential ofgenerating slag and pollution increases in comparison with thatof liquid fossil fuels [251] The salt that enters the boilers canbecome encrusted on the walls and shorten the equipments lifespan [261] If the salt is not removed it creates significant amountsof ash [91] Amberlite 252 macroporous resin could be a goodchoice to remove sodium ions from glycerolwater solutions withhigh salt concentration [262263]

7 Conclusion

The problems of diminishing petroleum reserves and theincreasing awareness of environmental pollution from petroleumfuel emissions have led to the urge to find renewable alternativefuels as a substitute for petroleum based fuels The production ofecological fuel components (bioesters bioethanol) that are man-ufactured from renewable sources has in recent days increaseddrastically due to the environmental policy in many developednations of the world Biodiesel which has environmental benefitsand is produced from renewable resources has become moreattractive Crude glycerol is produced in significant quantitiesduring the transesterification of triglycerides to produce biodiesel(about 10 ww) and through the process of saponification

The global market has been dramatically altered by the arrivalof biodiesel Increasing quantities of glycerol began to be dumpedto global market and prices began to fall reaching the lowesthistorical values When refined to a chemically pure substanceglycerol can be a very valuable by-product of the biodieselproduction process with hundreds of uses Purification to thatstage however is costly and generally out of the range ofeconomic viability for small and medium biodiesel industry

Alternative uses for crude glycerol should be explored toproduce a biodiesel increasingly competitive global market

New uses are needed to add value to this residue to optimizeprocess efficiency and reduce the impacts of disposal Crudeglycerol has been widely recognized as an attractive sustainableresource for the chemical industry

The simplest utilization method of crude glycerol is its combus-tion which is an advantageous method as it does not require anypurification However this process is not easy from a technologicalpoint of view The heat of combustion is about half of that of fossilfuels it is highly viscous making it difficult to spray and it has ahigh auto-ignition temperature (about 370 1C) Also low tempera-tures of burning can generally produce acrolein (between 280 and300 1C) The presence of mineral salts causes corrosion problemsin the burner nozzles and in the combustion system itself whichalso act as inhibitors of the flame which makes combustion ofcrude glycerol very difficult

The glycerin market is a complex volatile market which isdependent on global supply There have been many changes in theglycerin market over the last twenty years making it difficult todevelop a model to predict future prices The price of domesticrefined glycerin is negatively correlated with Middle Easternpetroleum production and European glycerin production

Global glycerin production has increased dramatically in recentyears due to renewable fuel production driven by subsidies taxbreaks and usage mandates Prices have dropped due to theincreased supply of glycerin Refined glycerin prices have almosthalved while crude prices hover between five and fifteen centsa pound

Biodiesel production is inadvertently affecting the soap manu-facturing and fatty acid production industries by competing forinput feedstock and driving down glycerin prices This probablywill make some of these companies move their operations abroadSince most of the countrys refineries are owned by the manufac-turers of fatty acid and soap this could cause a decrease in refinedglycerin capacity

Coinciding with most data published in the scientific literatureburning of crude glycerol can contribute to reduce the countriesrsquodependence on imported petroleum It is renewable and it con-tributes less to global warming unlike petroleum fuels because ofits closed carbon cycle The main raw material can grow seasonafter season and most of the carbon in the fuel was originallyremoved from the atmosphere by the plant Finally today crudeglycerol has a low cost

References

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[2] Demirbas A Political economic and environmental impacts of biofuels areview Applied Energy 200986108ndash17

[3] Ma F Hanna MA Biodiesel production a review Bioresource Technology1999701ndash15

[4] Bhatti HN Hanif MA Qasim M Ata-ur-Rehman Biodiesel production fromwaste tallow Fuel 2008872961ndash6

[5] Pramanik T Tripathi S Biodiesel clean fuel of the future HydrocarbonProcessing 20058449ndash54

[6] Bournay L Casanave D Delfort B Hillion G Chodorge JA New heterogeneousprocess for biodiesel production a way to improve the quality and the valueof the crude glycerin produced by biodiesel plants Catalysis Today2005106190ndash2

[7] Knothe G van Gerpen J Krahl J The biodiesel handbook Champaign IllinoisUSA AOCS Press 2005

[8] Woo C Clean fuel trends in Asia contribution of MTBE HydrocarbonProcessing 20078685ndash8 05Jul2007

[9] Vidosh M Praksh V Alok Ch Impacts of bio-fuel use a review InternationalJournal of Engineering Science and Technology (IJEST) 201133776ndash82

[10] Yuste AJ Dorado MP A neural network approach to simulate biodieselproduction from waste olive oil Energy amp Fuels 200620399ndash402

[11] Gonzaacutelez-Pajuelo M Andrade JC Vasconcelos I Production of 13-propane-diol by Clostridium butyricum VPI 3266 using a synthetic medium and crudeglycerol Journal of Industrial Microbiology and Biotechnology 200431442ndash6


[12] Thompson JC He BB Characterization of crude glycerol from biodieselproduction from multiple feedstocks Applied Engineering in Agriculture200622261ndash5

[13] Miller-Klein Associates Impact of Biodiesel Production on the GlycerolMarket October 2006 pp 1ndash5 UK

[14] Melero JA Vicente G Morales G Paniagua M Moreno JM Roldaacuten R et alAcid-catalyzed etherification of bio-glycerol and isobutylene over sulfonicmesoestructured siacutelicas Applied Catalysis A General 200834644ndash51

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[16] Borzani W Batch ethanol fermentation the correlation between thefermentation efficiency and the biomass initial concentration depends onwhat is considered as produced ethanol Brazilian Journal of Microbiology20063787ndash9

[17] Yazdani SS Gonzalez R Anaerobic fermentation of glycerol a path toeconomic viability for the biofuels industry Current Opinion in Biotechnol-ogy 200718213ndash9

[18] Choi WJ Glycerol-based biorefinery for fuels and chemicals Recent Patentson Biotechnology 20082(3)173ndash80

[19] Ruth L Bio or bust The economic and ecological cost of biofuels EMBOReports 200812(9)130ndash133

[20] Scharlemann JPW Laurance WF How green are biofuels Science 2008319(5859)43ndash4

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[23] Gesslein BW Humectants in personal care formulation a practical guide InSchueller R Romanowski P editors Conditioning agents for hair and skinMarcel Dekker Inc 1999 p 95ndash6

[24] Rahmat N Abdullah AZ Mohamed AR Recent progress on innovative andpotential technologies for glycerol transformation into fuel additives acritical review Renewable amp Sustainable Energy Reviews 201014987ndash1000

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[26] Brady JE General chemistry principles and structure 5th ed New York JohnWiley amp Sons Inc 1990

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[28] Loacutepes FD Revilla JL Munilla MH Glycerol In Manual dos derivados da cana-de-accediluacutecar diversificaccedilatildeo mateacuterias primas derivados do bagaccedilo do melaccedilooutros derivados resiacuteduos energia Brasiacutelia ABIPTI 1999 cap 54393ndash397

[29] Chung YH Rico DE Martinez CM Cassidy TW Noirot N Ames A et alEffects of feeding dry glycerin to early postpartum Holstein dairy cows onlactational performance and metabolic profiles Journal of Dairy Science2007905682ndash91

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[31] The Soap and Detergent Association Glycerine An Overview New York1990

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[34] Vaz VHS Carvalho JBR Santanna MC Silva MS Viabilidade de usina debriquete de casca de coco e glicerina em Sergipe II Foacuterum Brasileiro deEnergia 2010 Bento Gonccedilalves ndash RS ndash Brasil langhttpwwwinstitutoventuricombrenergiatrabalhos05pdfrang (accessed 05 October 2011)

[35] Thamsiriroj T Murphy JD Can rape seed biodiesel meet the European Unionsustainability criteria for biofuels Energy amp Fuels 2010241720ndash30

[36] Lide DR editor Handbook of chemistry and physics 84th ed Boca RatonFla CRC Press Inc 1999

[37] Stelmachowski M Utilization of glycerol a by-product of the transesterifica-tion process of vegetable oils a review Ecological Chemistry and Engineer-ings 2011189ndash30

[38] Morrison LR Glycerol in encyclopedia of chemical technology New YorkWiley 921ndash32

[39] Dharmadi Y Murarka A Gonzalez R Anaerobic fermentation of glycerol byEscherichia coli a new platform for metabolic engineering Biotechnologyand Bioengineering 200694821ndash9

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[42] Hedtke D Glycerine processing In Hui YH editor Baileys industrial oil ampfat products Volume 5 industrial and consumer nonedible products fromoils and fats 5th ed New York Wiley and Sons Inc 1996 p 275ndash308

[43] Van Gerpen J Shanks B Pruszko R Clements D Knothe G Biodieselproduction technology August 2002ndashJanuary 2004 Report no NRELSR-510-36244 US DOE National Renewable Energy Laboratory 2004 ColoradoUSA

[44] Bohon MD Metzger BA Linak WP King CJ Roberts WL Glycerol combustionand emissions Proceedings of the Combustion Institute 2011332717ndash24

[45] EET Corp Glycerol Purification available at langhttpwwweetcorpcomheepmbiodieselpdfrang (accessed 18 May 2013)

[46] Francis G Edinger R Becker K A concept for simultaneous wastelandreclamation fuel production and socioeconomic development in degradedareas in India need potential and perspectives of Jatropha PlantationsNatural Resources Forum 20052912ndash24

[47] Banse M Tabeau A Woltjer G van Meijl G van Meijl H Impact of EuropeanUnion Biofuel Policies on World Agricultural and Food Markets In Papersubmitted for the GTAP conference 2007

[48] Suppes GJ Biobased propylene glycol and monomers from natural glycerinEPA 2006 Available in langhttpepagovgreenchemistrypubspgccwinnersaa06htmlrang (accessed 26 December 2012)

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[50] Wilson EK Vegetable-oil-derived biodiesel a cheap and plentiful alternativeto petroleum products is rising in popularity Chemical amp Engineering News200280

[51] Vermeersch G Development of a biodiesel activity Oleagineux Corps GrasLipides 2001833ndash8

[52] Adhikari S Fernando S Haryanto A Production of hydrogen by steamreforming of glycerin over alumina-supported metal catalysts CatalysisToday 2007129355ndash64

[53] Demirbas MF Balat M Recent advances on the production and utilizationtrends of biofuels a global perspective Energy Conversion and Management2006472371ndash81

[54] Directive 200330EC of the European Parliament and of the Council of8 May 2003 on the promotion of the use of biofuels or other renewable fuelsfor transport Official Journal of the European Union 17 May 2003

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[58] Gunstone FD Market report Lipid Technology 200820264[59] National Biodiesel Board US Biodiesel Production Capacity 2012 available

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[60] Palm Oil HQ Crude and Refined Palm Oil Global Market InformationAvailable in langhttpwwwpalm-oilorgrang (accessed 10 May 2013)

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[62] PRWeb Global Glycerin Market to Reach 44 Billion Pounds by 2015According to a New Report by Global Industry Analysts Inc October 292010 langhttpwwwprwebcomreleasesglycerin_naturaloleo_chemicalsprweb4714434htmrang (accessed 20 May 2013)

[63] Bizzari S Blagoev M Mori H Glycerin Chemical Economics HandbookmdashSRIConsulting Jun 2012 langhttpwwwihscomproductschemicalplanningcehglycerinaspxpu=1amprd=chemihsrang (accessed 20 May 2013)

[64] Metzger JO Fats and oils as renewable feedstock for chemistry EuropeanJournal of Lipid Science and Technology 2009111865ndash76

[65] Sims B Growing demand for glycerin to keep up with supply increasesBiodiesel Magazine 25Jan2011 langhttpbiodieselmagazinecomarticles7553growing-demand-for-glycerin-to-keep-up-with-supply-increasesrang(accessed 20 May 2013)

[66] Sabourin-Provost G Hallenbeck PC High yield conversion of a crude glycerolfraction from biodiesel production to hydrogen by photofermentationBioresource Technology 20091003513ndash7

[67] ICISpricing 2012 b Sample report 14th Nov 2012 Glycerine (Europe)langhttpwwwicispricingcomil_sharedSamplesSubPage170asprang (accessed21 May 2013)

[68] Nilles D Combating the glycerin glut Biodiesel Magazin 2006vol65ndash6accessed 24 October 2011langhttpwwwbiodieselmagazinecomarticles1123combating-the-glycerin-glutrang

[69] US Soybean Export Council Inc Glycerin Market Analysis Indianapolis USA 2008 Available in langhttpwwwgooglecomurlsa=tamprct=jampq=crude20glycerin20is20volatileampsource=webampcd=7ampved=0CFAQFjAGampurl=http3A2F2Fwwwasaimseacom2Fdownload_docphp3Ffile3DGlycerin2520Market2520Analysis_Finalpdfampei=brDaTob5JYuftwetsMjtAQampusg=AFQjCNE5ZJXrlrpTsh5VPOePQ24YiPYILgrang (accessed Jan 2013)

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[71] Willke TH Vorlop KD Industrial bioconversion of renewable resourcesas an alternative to conventional chemistry Applied Microbiology andBiotechnology 200466131ndash42

[72] McCoy M Agribusiness giant goes head-to-head against petroleum-basedchemical companies Chemical amp Engineering News 20068432


[73] McCoy M Glycerin Surplus plants are closing and new uses for the chemicalare being found Chemical amp Engineering News 200684(6)7

[74] Pagliaro M Rossi M The future of glycerol new uses of a versatile rawmaterial RSC Green Chemistry 20085212ndash8

[75] Werpy T Petersen G Aden A Bozell J Holladay J White J et al Top valueadded chemicals from biomass Volume I Results of screening for potentialcandidates from sugars and synthesis gas United States Department ofEnergy Energy Efficiency and Renewable Energy 2004 accessed 24 October2011langhttpwwwostigovbridgepurlcoverjsppurl=15008859-s6ri0Nnativerang

[76] McCoy M Glycerin Gambit Making chemicals from the biodiesel by-productproves challenging Chemical amp Engineering News 20098716ndash7

[77] Argus Media Ltd Argus Biofuels Premiums Steep Sideways 2011 N1 11-125pp 1-5 langhttpwwwargusmediacomBioenergysimmediaFilesPDFsSamplesArgus-Biofuelsashxrang (accessed 24 October 2011)

[78] Da Silva GP Mack M Contiero J Glycerol a promising and abundant carbonsource for industrial microbiology Biotechnology Advances 20092730ndash9

[79] Gonccedilalves BRL Perez L Acircngelo ACD Glicerol Uma inovadora fonte deenergia proveniente da produccedilatildeo de biodiesel 2nd International WorkshopAdvances in Cleaner Production Key Elements for Sustainable WorldEnergy Water and Climate Change Satildeo Paulo-Brazil May 2009

[80] Mota CJA Pinto BP Lyra JT Obtenccedilatildeo de eacutesteres de glicerol para uso comoaditivos a combustiacutevel III Congresso da rede brasileira de biodiesel BrasiacuteliaDF 2009 Anais v3 331ndash332 2009

[81] Pousa GPAG Santos ALF Suarez PAZ History and policy of biodiesel in BrazilEnergy Policy 2007355393ndash8

[82] Bowker M Davies PR Al-Mazroai LS Photocatalytic reforming of glycerolover gold and palladium as an alternative fuel source Journal of CatalysisLetters 2008128253ndash5

[83] Costa R Glicerina o tamanho do problema Revista Biodieselbr 20081(3)16ndash20 Paranaacute

[84] Freitas SM Nachiluk K Desempenho da Produccedilatildeo Brasileira de Biodiesel em2008 Anaacutelises e Indicadores do Agronegoacutecio 2009 4(2)

[85] ANPmdashBrazilian Agency of Petroleum Natural Gas and Biofuels 2013(Agecircncia Nacional do Petroacuteleo Gaacutes Natural e Biocombustiacuteveis 2013)langhttpwwwanpgovbrrang (accessed 25 May 2013)

[86] Souza FGJr La Glicerina un derivado de la produccioacuten de biodiesel podriacutealimpiar derrames de petroacuteleo en el mar 16Julio2010 langhttpbiodieselcomar3799la-glicerina-un-derivado-de-la-produccion-de-biodiesel-podria-limpiar-derrames-de-petroleo-en-el-marrang (accessed 24 October 2011)

[87] Sustanaible Carbon Uso da glicerina por ceramic eacute destaque em revista Julio2010 Available in langhttpcarbonosustentavelbrasilwordpresscom20100729uso-de-glicerina-por-ceramica-e-destaque-em-revistarang (accessed Febru-ary 2013)

[88] Rivaldi JD Sarrouh BF Fiorilo R da Silva SS Glicerol de Biodiesel Biotecno-logia Ciencia amp Desenvolvimento 20072008 Ano 10 no 37 44ndash51

[89] Beatriz A Arauacutejo YJK de Lima DP Glicerol um breve histoacuterico e aplicaccedilatildeoem siacutenteses estereossetivas Quiacutemica Nova 201134(2)306ndash19

[91] Johnson DT Taconi KA The glycerin glut options for the value-addedconversion of crude glycerol resulting from biodiesel production Environ-mental Progress 200726338ndash48

[92] Solomon BO Zeng AP Biebl H Schlieker H Posten C Deckwer WDComparison of the energetic efficiencies of hydrogen and oxychemicalsformation in Klebsiella pneumoniae and Clostridium butyricum during anae-robic growth on glycerol Journal of Biotechnology 199539107ndash17

[90] Schievano A DImporzano G Adani F Substituting energy crops with organicwastes and agro-industrial residues for biogas production Journal ofEnvironmental Management 2009902537ndash41

[93] Barbirato F Chedaille D Bories A Propionic acid fermentation from glycerolcomparison with conventional substrates Applied Microbiology and Bio-technology 199747441ndash6

[94] Barbirato F Suzette A Soucaille P Camarasa C Salmon JM Bories AAnaerobic pathways of glycerol dissimilation by Enterobacter agglomeransCNCM 1210 limitations and regulations Microbiology 1997423ndash321431997423ndash32

[95] Barbirato F Himmi EH Conte T Bories A 13-Propanediol production byfermentation an interesting way to valorize glycerin from the ester andethanol industries Industrial Crops and Products 19987281ndash9

[96] Kenar JA Glycerol as a platform chemical sweet opportunities on thehorizon Lipid Technology 200719(11)249ndash53

[97] Oliveira FCC Suarez PAZ dos Santos WLP Biodiesel Possibilidades eDesafios Quiacutemica Nova na Escola 200828 Brazil

[98] Soap and saponification Available in langhttpseattlecentraledufacultyptranbastyrsummer2007organic20lectureExperiment204Soap20Lecturepdfrang (accessed 21 May 2013)

[99] Papanikolaou S Muniglia L Chevalot I Aggelis G Marc I Yarrowia lipolyticaas a potential producer of citric acid from crude glycerol Journal of AppliedMicrobiology 20029237ndash44

[100] Mu Y Teng H Zhang DJ Wang W Xiu ZL Microbial production of 13-propanediol by Klebsiella pneumoniae using crude glycerol biodiesel pre-parations Biotechnology Letters 2006281755ndash9

[101] Canakci M Sanli H Biodiesel production from various feedstocks and theireffects on the fuel properties Journal of Industrial Microbiology andBiotechnology 200835431ndash41

[102] Marchetti JM Miguel VU Errazu AF Possible methods for biodiesel produc-tion Renewable amp Sustainable Energy Reviews 2007111300ndash11

[103] Miesiac I Methods for utilization of the glycerine fraction from methanolysisof rape oil Przemysl Chemiczny 2003821045ndash7

[104] Kreutzer U Manufacture of fatty alcohols based on natural fats and oilsJournal of the American Oil Chemistsrsquo Society 198461(2)343ndash8

[105] Suarez PAZ Meneguetti SMP Meneguetti MR Wolf CR Transformaccedilatildeo detrigliceriacutedeos em combustiacuteveis materiais polimeacutericos e insumos quiacutemicosalgumas aplicaccedilotildees da cataacutelise na oleoquiacutemica Quiacutemica Nova 200730667ndash76

[106] Hui YH Baileys industrial oil and fat products 5th edEdible oil and fatproducts processing technology Volume 4 John Wiley amp Sons Inc 1996

[107] Hillion G Delfort B le Pennec D Bournay L Chodorge JA Biodiesel produc-tion by a continuous process using a heterogeneous catalyst Fuel Chemistry200348(2)636ndash8

[108] Coronado C JR Thermoeconomical Analyses of a Biodiesel ProductionThecnical Economical and Ecological Aspects (in Portuguese) 171f Thesis(Doctorate in Mechanical Engineerig) Satildeo Paulo State University ndash UNESPCampus of Guaratinguetaacute ndash FEG 2010 Satildeo Paulo Brazil

[109] Yan S DiMaggio C Mohan S Kim M Salley SO Simon Ng KY Advancementsin heterogeneous catalysis for biodiesel synthesis Topics in Catalysis201053721ndash36

[110] Bornscheuer UT Lipase-catalyzed syntheses of monoacylglycerols Enzymeand Microbial Technology 199517578ndash86

[111] Pachauri N He B Value added utilization of crude glycerol from biodieselproduction a survey of current research activities In Proceedings of theASABE annual international meeting Portland Oregon 9ndash12 July 2006American Society of Agricultural and Biological Engineers (ASABE) St JosephMissouri USA 2006

[112] SRS Engineering Corporation 2008 Available in langhttpwwwsrsbiodieselcomGlycerinSpecificationsaspxrang (accessed 07 December 2011)

[113] Kenkel P Holcomb R Feasibility of on-farm or small scale oilseed processingand biodiesel In English BC Menard J Jensen K editors Integration ofagricultural and energy systems Atlanta Georgia Global Bioenergy Partner-ship 2008

[114] Posada JA Cardona CA Cetina DM Bioglicerol como materia prima para laobtencioacuten de productos de valor agregado En Cardona CA Avances investi-gativos en la produccioacuten de biocombustibles Manizales Artes Graficas Tizaacuten103ndash127

[115] Soap and Detergent Association Why Glycerin USP 2000 USA[116] Gunstone FD Vegetable oils in food technology composition Properties and

uses 2nd edBlackwell Publishing Ltd 2011[117] Chetpattananondh P Rukprasoot J Bunyakan Ch Tongurai Ch Glycerolysis of

crude glycerol derived from biodiesel process In PSU-UNS InternationalConference on Engineering and EnvironmentmdashICEE-2005 Novi Sad Serbia-Montenegro 19ndash21 May 2005 pp 1ndash5

[118] DAquino R Ondrey G Outlets for glycerin Chemical Engineering -New York2007114(9)31ndash7

[119] Abbadi A Bekkum HV Highly selective oxidation of aldonic acids to 2-keto-aldonic acids over Pt-Bi and Pt-Pb catalysts Applied Catalysis A General1995124409ndash17

[120] Kimura H Oxidation assisted new reaction of glycerol Polymers forAdvanced Technologies 200112697ndash710

[121] Kimura H Polyketomalonate by catalytic oxidation of glycerolover a CeBiPtcatalyst II Journal of Polymer Science Part A Polymer Chemistry1996343607ndash14

[122] Kimura H Polyketomalonates by catalytic oxidation of glycerol I Journal ofPolymer Science Part A Polymer Chemistry 1996343595ndash605

[123] Kimura H Poly(ketomalonate) by catalytic oxidation of glycerol(4)anionicpolymerization Journal of Polymer Science Part A Polymer Chemistry199836195ndash205

[124] Besson M Gallezot P Selective oxidation of alcohols and aldehydes on metalcatalysts Catalysis Today 200057127ndash41

[125] Carrettin S McMorn P Johnston P Griffin K Kiely CJ Hutchings GJ Oxidationof glycerol using supported Pt Pd and Au catalysts Chemical Physics200351329ndash36

[126] Garcia R Besson M Gallezot P Chemoselective catalytic oxidation of glycerolwith air on platinum metals Applied Catalysis A General 1995127165ndash76

[127] Gallezot P Selective oxidation with air on metal catalysts Catalysis Today199737405ndash18

[128] Fordham P Besson M Gallezot P Selective catalytic oxidation of glyceric acid totartronic and hydroxypyruvic acids Applied Catalysis A General 1995133179ndash84

[129] Ciriminna R Palmisano G Pina CD Rossi M Pagliaro M One-pot electro-catalytic oxidation of glycerol to DHA Tetrahedron Letters 2006476993ndash5

[130] Pyle DJ Garcia RA Wen Z Producing docosahexaenoic acid (DHA)-rich algaefrom biodiesel-derived crude glycerol effect of impurities on DHA produc-tion and algal biomass composition Journal of Agriculture and FoodChemistry 2008563933ndash9

[131] Davis WR Tomsho J Nikam S Cook EM Somand D Peliska JA Inhibition of HIV-1reverse transcriptase-catalyzed DNA strand transfer reactions by 4-chlorophenylhydrazone of mesoxalic acid Biochemistry-US 20003914279ndash91

[132] Kimura H Tsuto K Catalytic synthesis of DL-serine and glycine from glycerolJournal of the American Oil Chemistsrsquo Society 199370(10)1027ndash30

[133] Dasari MA Kiatsimkul PP Sutterlin WR Suppes GJ Lowpressure hydroge-nolysis of glycerol to propylene glycol Applied Catalysis A General2005281225ndash31

[134] Zheng Y Chen X Shen Y Commodity chemicals derived from glycerol animportant biorefinery feedstock Chemical Reviews 2008108(12)5253ndash77


[135] Holser RA Development of new products from biodiesel glycerin In Hou CTShaw JF editors Biocatalysis and bioenergy New Jersey Wiley-Interscience2008 p 154

[136] Zhou C Beltramini JN Fan Y Lu GQ Chemoselective catalytic conversion ofglycerol as a biorenewable source to valuable commodity chemicals Chemi-cal Society Reviews 200837(3)527ndash49

[137] Gu Y Azzouzi A Pouilloux Y Jerome F Barrault J Heterogeneously catalyzedetherification of glycerol new pathways for transformation of glycerol tomore valuable chemicals Green Chemistry 200810(2)164ndash7

[138] Kim YC Park NC Shin JS Lee SR Lee YJ Moon DJ Partial oxidation of ethyleneto ethylene oxide over nanosized Agα-Al2O3 catalysts Catalysis Today200387153ndash62

[139] Girke W Klenk H Arntz D Haas T Neher A Patent US5387720 Process forthe production of acroleiacutena 1995

[140] Buumlhler W Dinjus E Ederer HJ Kruse A Mas C Ionic reactions and pyrolysis ofglycerol as competing reaction pathways in near- and supercritical waterJournal of Supercritical Fluids 20022237ndash53

[141] Hirai T Ikenaga NO Miyake T Suzuki T Production of hydrogen by steamreforming of glycerin on ruthenium catalyst Energy amp Fuels 2005191761ndash2

[142] Adhikari S Fernando SD Haryanto A Hydrogen production from glycerin bysteam reforming over nickel catalysts Renewable Energy 200833(5)1097ndash100

[143] Santibaacutentildeez C Varnero MT Bustamante M Residual glycerol from biodieselmanufacturing waste or potential source of bioenergy a review ChileanJournal of Agricultural Research 201171(3)469ndash75

[144] Garcia E Laca M Perez E Garrido A Peinado J Newclass of acetal derivedfrom glycerin as a biodiesel fuel component Energy amp Fuels 200822(6)4274ndash80

[145] Baumann H Buumlhler M Fochem H Hirsinger F Zoebelein H Falbe J Naturalfats and oilsmdashrenewable raw materials for the chemical industry Ange-wandte Chemie International Edition of England 198827(1)41ndash62

[146] Kesling HS Karas LJ Liotta FJJr Patent US5308365 1994[147] Gupta VP Patent US5476971 Glycerine ditertiary butyl ether preparation

1995[148] Jaecker-Voirol A Durand I Hillion G Delfort B Montagne X Glycerin for new

biodiesel formulation Oil amp Gas Science and Technology 200863(4)395ndash404

[149] Clacens JM Pouilloux Y Barrault J Selective etherification of glycerol topolyglycerols over impregnated basic MCM-41 type mesoporous catalystsApplied Catalysis A General 2002227181ndash90

[150] Kunieda H Akahane A Feng J Ishitobi M Phase behavior of polyglyceroldidodecanoates in water Journal of Colloid and Interface Science2002245365ndash70

[151] Oudhoff KA Van Damme FA Mes EPC Schoenmakers PJ Kok WT Character-ization of glycerin-based polyols by capillary electrophoresis Journal ofChromatography A 20041046263ndash9

[152] Vieville C Yoo JW Pelet S Mouloungui Z Synthesis of glycerol carbonate bydirect carbonatation of glycerol in supercritical CO2 in the presence ofzeolites and ion exchange resins Catalysis Letters 199856245ndash7

[153] Dibenedetto A Pastore C Aresta M Direct carboxylation of alcohols toorganic carbonates comparison of the group 5 element alkoxides catalyticactivity an insight into the reaction mechanism and its key steps CatalysisToday 200611588ndash94

[154] Aresta M Dibenedetto A Nocito F Pastore C A study on the carboxylation ofglycerol to glycerol carbonate with carbon dioxide the role of the catalystsolvent and reaction conditions Journal of Molecular Catalysis A Chemical2006257149ndash53

[155] Claude S Research of new outlets for glycerolmdashrecent developments inFrance European Journal of Lipid Science and Technology 1999101(3)101ndash4

[156] Plasman V Caulier T Boulos N Polyglycerol esters demonstrate superiorantifogging properties for films Plastics Additives and Compounding 20057(2)30ndash3

[157] Hiremath A Kannabiran M Rangaswamy V 13-Propanediol production fromcrude glycerol from jatropha biodiesel process New Biotechnology 201128(1)19ndash23

[158] Lee SH Park DR Kim H Lee J Jung JC Woo SY Direct preparation ofdichloropropanol (DCP) from glycerol using heteropolyacid (HPA) catalysts acatalyst screen study Catalysis Communications 200891920ndash3

[159] Volpato G Rodrigues RC Heck JX Ayub MAZ Production of organic solventtolerant lipase by staphylococcus caseolyticus EX17 using crude glycerol assubstrate Journal of Chemical Technology and Biotechnology 200883821ndash8

[160] BIODIESEL Rev Ed Letra Boreal httpISSN1980-4008 no 30 pp 16ndash17Julho 2008

[161] Barbirato F Bories A Relationship between the physiology of Enterobacteragglomerans CNCM 1210 grown anaerobically on glycerol and the cultureconditions Research in Microbiology 199748475ndash84

[162] Menzel K Zeng AP Deckwer WD High concentration and productivity of 13-propanediol from continuous fermentation of glycerol by Klebsiella pneu-monia Enzyme and Microbial Technology 19972082ndash6

[163] Wang ZX Zhuge J Fang H Prior BA Glycerol production by microbialfermentation a review Biotechnology Advances 200119201ndash23

[164] Zamzow KL Tsukamoto TK Miller GC Waste from biodiesel manufacturingas an inexpensive carbon source for bioreactors treating acid mine drainageMine Water amp the Environment 200625163ndash70

[165] Cerrate S Yan F Wang Z Coto C Sacakli P Waldroup PW Evaluation ofglycerine from biodiesel production as a feed ingredient for broilers Journalof Poultry Science 200651001ndash7

[166] Roger V Fonty G Andre C Gouet P Effects of glycerol on the growthadhesion and cellulolytic activity of rumen cellulolytic bacteria and anaero-bic fungi Current Microbiology 199225197ndash201

[167] Schroder A Sudekum HK Glycerol as a by-product of the biodiesel produc-tion in diets for ruminants 10th International Rapseed Congress CanberraAustralia 1999 langhttpwwwregionalorgauaugcirc1241htmrang (accessed22 October 2011)

[168] Donkin SS Doane P Gylcerol as a feed ingredient in dairy rations In Tri StateDairy Nutrition Conference April 2007 97ndash103

[169] Kerley MC 2007 Could glycerin ndash a biodiesel byproduct ndash be used as a cattlefeed Science Daily langhttpwwwsciencedailycomreleases200705070525090245htmrang (accessed 22 October 2011)

[170] Della Casa G Bochicchio D Faeti V Marchetto G Poletti E Rossi A et al Useof pure glycerol in fattening heavy pigs Meat Science 200981(1)238ndash44

[171] Beatrice C Di Blasio G Lazzaro M Cannilla C Bonura G Frusteri F AsdrubaliF Baldinelli G Presciutti A Fantozzi F Bidini G Bartocci P Technologies forenergetic exploitation of biodiesel chain derived glycerol oxy-fuels produc-tion by catalytic conversion Applied Energy 201310263ndash71

[172] Slinn M Kendall K Mallon C Andrews J Steam reforming of biodiesel by-product to make renewable hydrogen Bioresource Technology 2008995851ndash8

[173] Byrd AJ Pant KK Gupta RB Hydrogen production from glycerol by reformingin supercritical water over RuAl2O3 catalyst Fuel 200887(1314)2956ndash60

[174] Ito T Nakashimada Y Koichiro S Matsui T Nishio N Hydrogen and ethanolproduction from glycerol-containing wastes discharged after biodiesel man-ufacturing process Journal of Bioscience and Bioengineering 2005100260ndash5

[175] Huber GW Shabaker JW Dumesic JA Raney NindashSn catalyst for H2 productionfrom biomass-derived hydrocarbons Science 20033002075ndash7

[176] Wen G Xu Y Ma H Xu Z Tian Z Production of hydrogen by aqueous-phasereforming of glycerol International Journal of Hydrogen Energy 2008336657ndash66

[177] Zhang B Tang X Li Y Xu Y Shen W Hydrogen production from steamreforming of ethanol and glycerol over ceria-supported metal catalystsInternational Journal of Hydrogen Energy 2007322367ndash73

[178] Caetano de Souza AC Silveira JL Hydrogen production utilizing glycerol fromrenewable feed stocksmdashthe case of Brazil Renewable amp Sustainable EnergyReviews 201115(4)1835ndash50

[179] Pagliaro M Rossi M The future of glycerol New usages for a versatile rawmaterial RSC Green Chem Book Ser 20085212ndash8

[180] Guodong W Yunpeng X Huaijun M Zhusheng X Zhijian T Production ofhydrogen by aqueous-phase reforming of glycerol International Associationfor Hydrogen Energy 2008336657ndash66

[181] Menezes AO Rodrigues MT Zimmaro A Borges LEP Fraga MA Production ofrenewable hydrogen from aqueous-phase reforming of glycerol over Ptcatalysts supported on different oxides Renewable Energy 201136(2)595ndash9

[182] Cortright RD Davda RR Dumesic JA Hydrogen from catalytic reformingof biomass-derived hydrocarbons in liquid water Nature 2002418964ndash7

[183] Tuza P Manfro R Ribeiro N Souza M Production of renewable hydrogen byaqueous-phase reforming of glycerol over NindashCu catalysts derived fromhydrotalcite precursors Renewable Energy 201350408ndash14

[184] Wang C Dou B Chen H Song Y Xu Y Du X et al Renewable hydrogenproduction from steam reforming of glycerol by NindashCundashAl NindashCundashMg NindashMgcatalysts International Journal of Hydrogen Energy 201338(9)3562ndash71

[185] Kamonsuangkasem K Therdthianwong S Therdthianwong A Hydrogenproduction from yellow glycerol via catalytic oxidative steam reformingFuel Processing Technology 2013106695ndash703

[186] Gutieacuterrez F Ollero P Serrera A Galera S Optimization of power andhydrogen production from glycerol by supercritical water reforming Chemi-cal Engineering Journal 2013218309ndash18

[187] Reungsang A Sittijunda S O-thong S Bio-hydrogen production from glycerolby immobilized Enterobacter aerogenes ATCC 13048 on heat-treated UASBgranules as affected by organic loading rate International Journal of Hydro-gen Energy 201338(17)6970ndash9

[188] Lin Y Catalytic valorization of glycerol to hydrogen and syngas InternationalJournal of Hydrogen Energy 201338(6)2678ndash700

[189] Karinen RS Krause AOI New biocomponents from glycerol Applied Catalysis2006306128ndash33

[190] Noureddini H Daily WR Hunt BA Production of ethers of glycerol fromcrude glycerol-the by-product of biodiesel production Chemical and Biomo-lecular EngineeringmdashResearch 199813121ndash9

[191] Kiatkittipong W Suwanmanee S Laosiripojana N Praserthdam P Assabum-rungrat S Cleaner gasoline production by using glycerol as fuel extenderFuel Processing Technology 201091(5)456ndash60

[192] Fernando S Adhikari S Kota K Bandi R Glycerol based automotive fuels fromfuture biorefineries Fuel 200786(1718)2806ndash9

[193] Melero JA van Grieken R Morales G Paniagua M Acidic mesoporous silicafor the acetylation of glycerol synthesis of bioadditives to petrol fuel Energyamp Fuels 2007211782ndash91

[194] Klepaacutecova K Mravec D Kaszonyi A Bajus M Etherification of glycerol andethylene glycol by isobutylene Applied Catalysis A General 20073281ndash13


[195] Ferreira P Fonseca IM Ramos AM Vital J Castanheiro JE Esterification ofglycerol with acetic acid over dodecamolybdophosphoric acid encaged inUSY zeolite Catalysis Communications 200910481ndash4

[196] Agnieszka MR Johannes DM Bonny WM Kuipers BH Ernersquo BM Glyceroletherification over highly active CaO-based materials new mechanisticaspects and related colloidal particle formation Chemistry A EuropeanJournal 2008142016ndash24

[197] Klepaacutecova K Mravec D Bajus M tert-Butylation of glycerol catalysed byionexchange resins Applied Catalysis A General 2005294141ndash7

[198] Richter M Krisnandi YK Eckelt R Martin A Homogeneously catalyzed batchreactor glycerol etherification by CsHCO3 Catalysis Communications200892112ndash6

[199] Tran BL Hamnik JM Blubaugh SJ Hydraulic fluids and fire-resistant fluidscomprising glycerin containing by-products USPTO patent application20080085846 Class 508583 ser no 11420140 2006

[200] Alhanash A Kozhevnikova EF Kozhevnikov IV Hydrogenolysis of glycerol topropanediol over Rupolyoxometalate bifunctional catalyst Catalysis Letters2008120307ndash11

[201] Chiu C Dasari MA Suppes GJ Sutterlin WR Dehydration of glycerol to acetolvia catalytic reactive distillation AIChE Journal 200652(10)3543ndash8

[202] Gutieacuterrez F Serrera A Galera S Ollero P Methanol synthesis from syngasobtained by supercritical water reforming of glycerol Fuel 2013105739ndash51

[203] Goetsch D Machay IS White LR Production of methanol from the crudeglycerol by-product of producing biodiesel United States PatentS7388034B1 2008

[204] Tsang SCE Oduru WO Redman DJ European patent application methanolproduction process World Intellectual Property Organization 2009WO130452A1

[205] Duan S Chen L Su F Lin J He C Weckbecker C et al European patentapplication oxygenated hydrocarbon reforming World Intellectual PropertyOrganization 2010 WO104467A1

[206] Posada JA Cardona CA Design and analysis of fuel ethanol production fromraw glycerol Energy 201035(12)5286ndash93

[207] Oh BR Seo JW Heo SY Hong WK Luo LH Joe MH et al Efficient productionof ethanol from crude glycerol by a Klebsiella pneumoniae mutant strainBioresource Technology 2011102(4)3918ndash22

[208] Amaral PFF Ferreira TF FonteS GC Coelho MAZ Glycerol valorization newbiotechnological routes Food and Bioproducts Processing 200987(3)179ndash86

[209] Defrain JM Hippen AR Kalscheur KF Jardon PW Feeding glycerol totransition dairy cows effects on blood metabolites and lactation perfor-mance Journal of Dairy Science 2004874195ndash206

[210] Donkin SS Koser SL White HM Doane PH Cecava MJ Feeding value ofglycerol as a replacement for corn grain in rations fed to lactating dairy cowsJournal of Dairy Science 200992(10)5111ndash9

[211] Carvalho ER Schmelz-Roberts NS White HM Doane PH Donkin SS Repla-cing corn with glycerol in diets for transition dairy cows Journal of DairyScience 201194(2)908ndash16

[212] Oliveira SVWB Leoneti AB Caldo GMM Oliveira MMB Generation ofbioenergy and biofertilizer on a sustainable rural property Biomass andBioenergy 201135(7)2608ndash18

[213] Schieck SJ Shurson GC Kerr BJ Johnston LJ Evaluation of glycerol a biodieselcoproduct in grow-finish pig diets to support growth and pork qualityJournal Animal Science 2010883927ndash35

[214] Li MH Minchew CD Oberle DF Robinson EH Evaluation of glycerol frombiodiesel production as a feed ingredient for channel catfish Ictaluruspunctatus Journal of the World Aquaculture Society 2010411

[215] Chung YH Rico DE Martinez CM Cassidy TW Noirot N Ames A et al Effectsof feeding dry glycerin to early postpartum Holstein dairy cows on lactationalperformance and metabolic profiles Journal of Dairy Science 2007905682ndash91

[216] Kansedo J Lee KT Bhatia S Cerbera odollam (sea mango) oil as a promisingnon-edible feedstock for biodiesel production Fuel 2009881148ndash50

[217] Ferraro SM Mendoza GD Miranda LA Gutierrez CG In vitro gas productionand ruminal fermentation of glycerol propylene glycol and molasses AnimalFeed Science and Technology 2009154112ndash8

[218] Wang C Liu Q Huo WJ Yang WZ Dong KH Huang YX et al Effects ofglycerol on rumen fermentation urinary excretion of purine derivatives andfeed digestibility in steers Animal Feed Science and Technology200912115ndash20

[219] Fisher LJ Erfle JD Lodge GA Sauer FD Effects of propylene glycol or glycerolsupplementation of the diet of dairy cows on feed intake milk yield andcomposition and incidence of ketosis Canadian Journal of Animal Science197353289ndash96

[220] Casa GD Bochicchio D Faeti V Marchetto G Poletti E Rossi A et al Use ofpure glycerol in fattening heavy pigs Meat Science 200981238ndash44

[221] Irieb Vegetable glycerin 2009 Available at langhttpwwwvapordencomnotesVegetablerang Glycerin (accessed 26 December 2012)

[222] Lee T Johnson W Earl R May non-nutritive sweetened beverages withglycerinersquo IPC8 Class AA23L238FI USPC Class 426590 2008 Available atlanghttpwwwfaqsorgpatentsapp20080226795rang (accessed 01 December2012)

[223] Watanabe M Iida T Aizawa Y Aida TM Inomata H Acrolein synthesisfrom glycerol in hot-compressed water Bioresource Technology 2007981285ndash90

[224] Corma A Huber GW Sauvanaud L OConnor P Biomass to chemicalscatalytic conversion of glycerolwater mixtures into acrolein reaction net-work Journal of Catalysis 2008257163ndash71

[225] Zhou C-J Huang C-J Zhang W-G Zhai H-S Wu H-L Chao Z-S Synthesis ofmicro- and mesoporous ZSM-5 composites and their catalytic application inglycerol dehydration to acrolein Studies in Surface Science and Catalysis2007527ndash30

[226] Tsukuda E Sato S Takahashi R Sodesawa T Production of acrolein fromglycerol over silica-supported heteropoly acids Catalysis Communications200781349ndash53

[227] Ning L Ding Y Chen W Gong L Lin R Lu Y et al Glycerol dehydration toacrolein over activated carbon-supported silicotungstic acids Chinese Jour-nal of Catalysis 200829212ndash4

[228] Cardona C Posada J Montoya M Use of glycerol from biodiesel productionconversion to added value products In Proceedings of European congress ofchemical engineering (ECCE-6) 2007

[229] Wang K Hawley MC DeAthos SJ Conversion of glycerol to 13-propanediolvia selective dehydroxylation Industrial and Engineering ChemistryResearch 2003422913ndash23

[230] Gong CS Du JX Cao NJ Tsao GT Coproduction of ethanol and glycerolApplied Biochemistry and Biotechnology 200084ndash86(1ndash9)543ndash59

[231] Rosa DS Bardi MAG Machado LDB Dias DB Silva LGA Kodama Y Starchplasticized with glycerol from biodiesel and polypropylene blends mechan-ical and thermal properties Journal of Thermal Analysis and Calorimetry2010181ndash6

[232] Villamagna F Hall BD Explosive compositions containing glycerin IPC8Class AC06B3128FI USPC Class 149-2 2008 Available at langhttpwwwfaqsorgpatentsapp20080245450rang (accessed on 10 Nov 2012)

[233] Lee SH Park DR Kim H Direct preparation of dichloropropanol (DCP) fromglycerol using heteropolyacid (HPA) catalysts a catalyst screen studyCatalysis Communications 200891920ndash3

[234] Stella M Glycerolmdashthe sweetener that doesnt sweeten your life Available atlanghttpwwwdiethealthclubcomarticles500diet-and-wellnessglycerolthesweetener-that-doesn-t-sweeten-your-lifehtmlrang (accessed 03 January 2012)

[235] Bauer R Katsikis N Varga S Hekmat D Study of the inhibitory effect of theproduct dihydroxyacetone on Gluconobacter oxydans in a semi-continuoustwo-stage repeated-fed-batch process Bioprocess and Biosystems Engineer-ing 20052837ndash43

[236] Pollington SD Enache DI Landon P Meenakshisundaram S Dimitratos NWagland A et al Enhanced selective glycerol oxidation in multiphasestructured reactors Catalysis Today 2009145169ndash75

[237] Demirel-Gulen S Lucas M Claus P Liquid phase oxidation of glycerol overcarbon supported gold catalysts Catalysis Today 2005102103166ndash72

[238] Chi Z Pyle D Wen Z Frear C Chen S A laboratory study of producingdocosahexaenoic acid from biodiesel-waste glycerol by microalgal fermenta-tion Process Biochemistry 2007421537ndash45

[239] Skoulou V Zabaniotou A Co-gasification of crude glycerol with lignocellu-losic biomass for enhanced syngas production Journal of Analytical andApplied Pyrolysis 201399110ndash6

[240] Robra S Serpa da cruz R Oliveira AM Almeida neto JA Santos JV Generationof biogas using crude glycerin from biodiesel production as a supplement tocattle slurry Biomass and Bioenergy 201034(9)1330ndash5

[241] Amon T Kryvoruchko V Amon B Schreiner M UntersuchungenzurWirkungvon Rohglycerin aus der Biodieselerzeugung als leistungssteigerndes Zusatz-mittel zur Biogaserzeugung aus Silomais Koumlrnermais Rapspresskuchen undSchweineguumllle Institut fuumlr Landtechnik Universitaumlt fuumlr Bodenkultur WienSource langhttpwwwnasbokuacatfileadmin_H93H931AmonPublikationenSEEGEndbericht pdfrang 2004 (accessed 25 June 2011)

[242] Siles JA Martiacuten MA Chica AF Martiacuten A Anaerobic co-digestion of glyceroland wastewater derived from biodiesel manufacturing Bioresource Technol-ogy 2010101(16)6315ndash21

[243] Fountoulakis MS Manios T Enhanced methane and hydrogen productionfrommunicipal solid waste and agro-industrial by-products co-digested withcrude glycerol Bioresource Technology 2009100(12)3043ndash7

[244] Newton DE Top shelf environmental chemistry Portland USA WalchPublishing 2004

[245] Metzger B Glycerol Combustion MSc Thesis North Carolina State Univer-sity 2007 Raleigh NC USA

[246] Luo N Fu X Cao F Xiao T Edwards PP Glycerol aqueous phase reforming forhydrogen generation over Pt catalystmdasheffect of catalyst composition andreaction conditions Fuel 2008873483ndash9

[247] Pyle D 2008 Use of biodiesel-derived crude glycerol for the production ofomega-3 polyunsaturated fatty acids by the microalga Schizochytrium lima-cinum Master on Sciences Thesis in Biological Systems Engineering VirginiaState University Blacksburg Virginia USA

[248] Valliyappan T Bakhshi TT Dalai AK Pyrolysis of glycerol for the productionof hydrogen or syn gas Bioresource Technology 2008994476ndash83

[249] Hajek M Skopal F Treatment of glycerol phase formed by biodieselproduction Bioresource Technology 20101013242ndash5

[250] EPP T Combustion of Glycerine for Combined Heat and Power Systems inBiodiesel Processing Facilities Bachelor Thesis University of Manitoba 2008Canada

[251] Department of Agriculture and Food (DAF) Government of WesternAustralia Glycerin Overview 2006 langhttpwwwagricwagovauPC_93205htmls=0rang (accessed 02 November 2011)


[252] Bombos D Mihaescu L Pisa I Bolma I Vasilievici G Zaharia E Burningglycerol emulsion in liquid fossil fuel Revista de Chimie 201162(5)562ndash6Bucharest

[253] Patzer R Stack Emissions Evaluation Combustion of Crude Glycerin andYellow Grease in an Industrial Fire Tube Boiler Agricultural UtilizationResearch Institute Marshall MN USA 2007

[254] Brady S Tam K Leung G Salam Ch Zero waste biodiesel using glycerin andbiomass to create renewable energy University of California RiversideUndergraduate Research Journal 200825ndash11

[255] Striugas N et al Processing of the glycerol fraction from biodiesel produc-tion plants to provide new fuels for heat generation Energetika 200854(3)5ndash12

[256] Striugas N Analysis of acroleine production during glycerol combustionLithuanian Energy Institute Laboratory of Combustion Processes KaunasLithuania 2010 langhttpwwwleiltrang (accessed January 2012)

[257] EPA U S Environmental Protection Agency Toxicological Review of AcroleinCAS No 107-02-8 EPA635R-03003 2003

[258] Bohon MD Characterization of glycerin combustion and emission MScthesis North Caroline State University USA 2010

[259] Steinmetz S Herrington J Winterrowd C Roberts W Wendt J Linak WCrude glycerol combustion particulate acrolein and other volatile organicemissions Proceedings of the Combustion Institute 201334(2)2749ndash57

[260] Mantzouridou F Naziri E Tsimidou MZ Industrial glycerol as a supplemen-tary carbon source in the production of β-carotene by Blakeslea trisporaJournal of Agricultural and Food Chemistry 2008562668ndash75

[261] BLUER Incineracioacuten de glicerina Availabe in langhttpwwwblueresAplicacionesIncineracion_glicerinahtmrang (accessed 07 December 2011)

[262] Carmona M Valverde JL Peacuterez A Warchol J Rodriguez JF Purification ofglycerolwater solutions from biodiesel synthesis by ion exchange sodiumremoval Part I Journal of Chemical Technology and Biotechnology 200984(7)738ndash44

[263] Carmona M Lech A de Lucas A Peacuterez A Rodriguez JF Purification ofglycerolwater solutions from biodiesel synthesis by ion exchange sodiumremoval Part II Journal of Chemical Technology and Biotechnology 200984(8)1130ndash5


61 Glycerol combustion 4867 Conclusion 488References 488

1 Introduction

Biofuels arose as a sustainable source of fuel in the search fornew energy resources and are considered an important form oftechnological progress in limiting greenhouse gas emissions anddiminishing pollution improving air quality [1] Biofuels are asource of renewable energy they are produced from naturalmaterial (biologically based) Among the most common biofuelsis ethanol generated from maize wheat or beets and biodieselfrom oily seeds andor animal fat [2] At present biofuels are usedas a source of energy as a substitute for fossil fuels because theyare biodegradable much cleaner and generate an acceptable levelof emissions gases [34]

Biodiesel stands out among biofuels It is a liquid fuel thatsobtained from natural lipids such as vegetable oil or animal fatusing industrial processes of esterification or transesterificationBiodiesel is superior to diesel oil for health and the environment(it is low in sulfur emits a low level of noxious particles like HCand CO and is better in the CO2 cycle in reducing global warming)as well as for engine performance (better lubrication high cetanenumber and more complete combustion) [5ndash7] Biodiesel isbiodegradable renewable and non-toxic It has a high flash pointbetter viscosity and caloric power similar to fossil fuels [7] Theseadvantages have convinced Asian countries to utilize biodiesel asan alternative fuel as one of the innovative solutions to reduceglobal air pollution generated by the growing number of vehicles[8] Mixtures are the most viable way to increase biodiesel usageelevating biodiesels share of the fuel market benefitting produ-cers guaranteeing competitive pricing for end users and requiringless incentives and tax exemptions [9] It has been reported thatfrom 75 to 95 of the end price of biodiesel is influenced by thecost of the raw material [10]

On the other hand production of biodiesel has a by-productglycerol Generally 10 to 20 of the total volume of biodieselproduced is made up of glycerol [11ndash15] The production of bio-ethanol also generates glycerol as a by-product up to 10 of theweight of the sugar consumed [16] Lately an intense debate hasfocused on this important problem in biodiesel production theinevitable production of glycerol as a by-product with a lowcommercial value [1217] Growing biodiesel production will leadto large surpluses of glycerol A fundamental question soon arisesWhat can be done with the glycerol This is one of the mainreasons that research at present is focused on developing technol-ogy to convert or use the glycerol in order to improve the biodieselbusiness and drastically improve its economic viability [1218]Though glycerol is a raw material and there are over 2000industrial uses incessant biodiesel production is leading glycerolto be dealt with as a waste product Specific concerns about thesocial and environmental impacts of biodiesel production havebeen growing [1920]

This manuscript is a review of the different approaches andtechniques used to produce glycerol (hydrolysis transesterifica-tion refining crude glycerol) the world biodieselglycerol produc-tion and consumption market the current world glycerin andglycerol prices and the news trends for the use of glycerol mainlyin Brazil Though it is not an ideal fuel one option (other than itsuse in the pharmaceutical or chemical industries) could be to burnit (glycerol combustion) locally in a combined heat and energy

generation process (cogeneration) replacing fossil fuels andoptimizing the efficiency of the process as well as reducing theimpacts of this byproduct The news and mainly research aboutthe combustion of glycerol was also investigated in this review

2 Glycerol

Glycerol is the main component of triglycerides found inanimal fat vegetable oil or crude oil Glycerol is derived fromsoap or from biodiesel production [1821] Its been known since2800 BCE when it was isolated by heating fat mixed with ashesto produce soap [22] However it is considered to have beendiscovered in 1779 by Swiss pharmacist K W Scheele who wasthe first to isolate this compound when he heated a mixture oflitharge (PbO) with olive oil In 1811 French chemist M E Chevrelcalled glycerin a liquid defining the chemical formulas of fattyacids and the formulas of glycerin in vegetable oil and animal fatHis work was patented It was known as the first industrialmethod to obtain glycerin soap by reacting fatty material withlime and alkaline material [23]

21 Glycerols physical properties

Glycerol is the simplest of the alcohols and is known bypropane-123-triol according to IUPAC It is also commerciallyknown as glycerin 123-propanotriol trihydroxypropane glycer-itol or glycidic alcohol [24] Glycerol is an oily liquid it is viscousodorless colorless and has a syrupy-sweet taste Glycerol is aliquid containing three hydrophilic hydroxyl groups that areresponsible for it being hygroscopic and its solubility in water[2526] Fig 1 shows the molecular structure of glycerol made upof three hydroxyls

Glycerin is completely miscible in many substances Amongthem are alcohol (methyl ethyl isopropyl n-butyl isobutylsecondary butyl and tertiary amyl) ethylene glycol propyleneglycol trimethylene glycol monomethyl ether and phenol [2829]Solubility of glycerin in acetone is 5 by weight in ethyl acetateits 9 Its slightly soluble in dioxane and ethyl and partiallyinsoluble in superior alcohol fatty acids and hydrocarbonate aswell as in chlorinated solvents such as hexane benzene andchloroform Glycerin is very viscous at normal temperatures itremains a viscous liquid even at 100 concentration withoutcrystallizing At low temperatures concentrated glycerin solutionstend to super cool as high viscosity fluid Viscosity rises at firstuntil it quickly becomes vitreous around minus89 1C Aqueous glycerinsolutions (at different concentrations) tend to have lower viscosity[30]

At low temperatures glycerin tends to super cool instead ofcrystallize Aqueous glycerin solutions resist freezing and are usedas antifreeze in cooling systems Glycerin does not oxidize in theatmosphere in normal conditions but can be easily oxidized byother oxidants Glycerin solutions need inhibitors when they areexposed to heat and in contact with ferrous metal or copper sincethe salts contained in these materials can catalyze oxidation [31]Glycerol has low volatility and low vapor pressure which is strictlylinked with its hygroscopic property Between 0 and 70 1Ctemperature changes have little effect on the vapor pressure ofglycerin solutions Like other alcohols glycerin has a lower vapor
















OECD-SIDS[40]



(closed cup)160























05

15

25

20

10

0

Jan-

92

Jan-

90

Jan-

88

Jan-

86

Jan-

84

Jan-

82

Jan-

80

Jan-

06

Jan-

04

Jan-

02

Jan-

00

Jan-

98

Jan-

96

Jan-

94

US

$kg






























H

H

H

H

H

C

C

C

OR

ORrsquo + 3 NaOH

ORrdquo


+

H

H

H

H

H

C

C

C

ORrsquordquo

ORrsquordquo

ORrsquordquo

H

H

H

H

H

C

C

C

OH

OH

OH

Catalyst


Reactor

Mineral Acid

Biodiesel

Glycerin




Mineral Acid

Vegetable Oil

Methanol

Catalyst

Water






Biodiesel

Methanol

Vegetable oil

gt98 Glycerin

Full MeOH evap

Glycerin Glycerin

Partial MeOH

evap

Partial MeOH

evap

R2R1





51 Hydrolysis

















NA NA Pass


NA NA Pass





































































































0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600















7 Conclusion










References




























































































































































































































































































OECD-SIDS[40]



(closed cup)160























05

15

25

20

10

0

Jan-

92

Jan-

90

Jan-

88

Jan-

86

Jan-

84

Jan-

82

Jan-

80

Jan-

06

Jan-

04

Jan-

02

Jan-

00

Jan-

98

Jan-

96

Jan-

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$kg






























H

H

H

H

H

C

C

C

OR

ORrsquo + 3 NaOH

ORrdquo


+

H

H

H

H

H

C

C

C

ORrsquordquo

ORrsquordquo

ORrsquordquo

H

H

H

H

H

C

C

C

OH

OH

OH

Catalyst


Reactor

Mineral Acid

Biodiesel

Glycerin




Mineral Acid

Vegetable Oil

Methanol

Catalyst

Water






Biodiesel

Methanol

Vegetable oil

gt98 Glycerin

Full MeOH evap

Glycerin Glycerin

Partial MeOH

evap

Partial MeOH

evap

R2R1





51 Hydrolysis

















NA NA Pass


NA NA Pass





































































































0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600















7 Conclusion










References

























































































































































































































































































05

15

25

20

10

0

Jan-

92

Jan-

90

Jan-

88

Jan-

86

Jan-

84

Jan-

82

Jan-

80

Jan-

06

Jan-

04

Jan-

02

Jan-

00

Jan-

98

Jan-

96

Jan-

94

US

$kg






























H

H

H

H

H

C

C

C

OR

ORrsquo + 3 NaOH

ORrdquo


+

H

H

H

H

H

C

C

C

ORrsquordquo

ORrsquordquo

ORrsquordquo

H

H

H

H

H

C

C

C

OH

OH

OH

Catalyst


Reactor

Mineral Acid

Biodiesel

Glycerin




Mineral Acid

Vegetable Oil

Methanol

Catalyst

Water






Biodiesel

Methanol

Vegetable oil

gt98 Glycerin

Full MeOH evap

Glycerin Glycerin

Partial MeOH

evap

Partial MeOH

evap

R2R1





51 Hydrolysis

















NA NA Pass


NA NA Pass





































































































0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600















7 Conclusion










References






























































































































































































































































































H

H

H

H

H

C

C

C

OR

ORrsquo + 3 NaOH

ORrdquo


+

H

H

H

H

H

C

C

C

ORrsquordquo

ORrsquordquo

ORrsquordquo

H

H

H

H

H

C

C

C

OH

OH

OH

Catalyst


Reactor

Mineral Acid

Biodiesel

Glycerin




Mineral Acid

Vegetable Oil

Methanol

Catalyst

Water






Biodiesel

Methanol

Vegetable oil

gt98 Glycerin

Full MeOH evap

Glycerin Glycerin

Partial MeOH

evap

Partial MeOH

evap

R2R1





51 Hydrolysis

















NA NA Pass


NA NA Pass





































































































0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600















7 Conclusion










References













































































































































































































































































Biodiesel

Methanol

Vegetable oil

gt98 Glycerin

Full MeOH evap

Glycerin Glycerin

Partial MeOH

evap

Partial MeOH

evap

R2R1





51 Hydrolysis

















NA NA Pass


NA NA Pass





































































































0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600















7 Conclusion










References





















































































































































































































































































NA NA Pass


NA NA Pass





































































































0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600















7 Conclusion










References






































































































































































































































































































































































0

100 Glycerol

400

200

800

600

1200

1000

100

1400

4020 80600 120

1600















7 Conclusion










References


















































































































































































































































































7 Conclusion










References













































































































































































































































































Glycerol: Production, consumption, prices, characterization and new trends in combustion

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Transcript of Glycerol: Production, consumption, prices, characterization and new trends in combustion