ARTICLE IN PRESS

Energy 33 (2008) 1801–1806

Contents lists available at ScienceDirect

Energy

0360-54

doi:10.1

� Corr

E-m

journal homepage: www.elsevier.com/locate/energy

Analysis of the emissions of volatile organic compounds from thecompression ignition engine fueled by diesel–biodiesel blend and diesel oilusing gas chromatography

S.L. Ferreira a,�, A.M. dos Santos a, G.R. de Souza a, W.L. Polito b

a Department of Mechanical Engineering, Center of Thermal and Fluid Engineering, University of Sao Paulo - Sao Carlos, 400 Trabalhor Saocarlense Avenue, Zip Code:

13560-970 Sao Carlos, SP, Brazilb Sao Carlos Institute of Chemistry, University of Sao Paulo, 400 Trabalhor Saocarlense Avenue, Zip Code: 13560-970 Sao Carlos, SP, Brazil

a r t i c l e i n f o

Article history:

Received 27 February 2008

Keywords:

Pollutant emissions

Fuels

Gas chromatography

42/$ - see front matter & 2008 Elsevier Ltd. A

016/j.energy.2008.08.002

esponding author. Fax: +5516 3373 8228.

ail address: serggiolf@yahoo.com.br (S.L. Ferre

a b s t r a c t

This paper describes the procedures of the analysis of pollutant gases, as volatile organic compounds

(benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) emitted by engines, using high-

resolution gas chromatography (HRGC). In a broad sense, CI engine burning diesel was compared with

B10 and a drastic reduction was observed in the emissions of the aromatic compounds by using B10.

Especially for benzene, the reduction of concentrations occurs on the level of about 19.5%. Although a

concentration value below 1mg ml�1 has been obtained, this reduction is extremely significant since

benzene is a carcinogenic compound.

& 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Due to the progress (urbanization, population growth anddevelopment of new technologies especially for motor vehicles),there has been a gradual increase in the rate of atmosphericpollutants emissions, causing several environmental problems.

Human activities have raised the amounts of pollutantslaunched into the atmosphere. In cities, emissions play animportant role in the level of air pollution, as gases like volatileorganic compounds (VOCs), carbon monoxide (CO), nitrogenoxides (NOx), sulphur oxides (SOx), acid gases among others areemitted [1].

In this way, people are exposed to high concentration levels ofatmospheric pollutants for a long time, increasing the probabilityof developing cancer or other serious health problems [1].Pollutants are the cause of serious damages to the immune,neurological, reproductive (with reduction of fertility) andrespiratory systems [1,2].

Many studies of emission, transport and deposition of atmo-spheric pollutants have been performed in a search for solutionsfor the control and reduction of air pollution in a larger number ofurban centers [3,4].

The use of biodiesel as an alternative fuel has a promisingpotential worldwide. Several countries have made a lot of

ll rights reserved.

ira).

investment in the production and possible trade of biodiesel, bymeans of production units with different capacities and distribu-tion action, particularly in Europe (France, Austria, Germany,Belgium, United Kingdom, Italy, Holland, Finland and Sweden),North America (United States) and Asia (Japan) [5].

In 2001, due to ecological reasons, the European Unionestablished the decrease of petroleum dependence on transporta-tion, responsible for more than 30% of the final energy consump-tion, by means of using alternative fuels, as biofuels [6].

Besides the importance of executing legislation, regardingfuels, vehicles’ emissions as well as air quality, as part of thepackage on the use of biofuels, must also be taken into account inthe Kyoto’s Protocol and its practical execution [6].

The advantages of biodiesel, such as high cetane number andoxygen content, promote the combustion process and improve theemission profile of exhaust gases. Many researches have shown thatbiodiesel-fueled engines produce less CO, unburned hydrocarbonsand fewer particulate emissions, in comparison with diesel fuel [7].

On the other hand, the difficulties associated with the use ofraw vegetable oils in diesel engines are injector coking, severeengine deposits, filter gumming problems, piston ring sticking,injector coking and thickening of the lubricating oil. The highviscosity and low volatility of raw vegetable oils are generallyconsidered the major drawbacks for their utilization as fuels indiesel engines. The high viscosity of vegetable oils deteriorates thefuel atomization and increases exhaust smoke [8]. The lowvolatility leads to the oil sticking to the injector or cylinder walls,resulting in a deposit formation.

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Table 1Specifications of the CI engine

Characteristics Description

Type 4-Cylinder in line, aspired, diesel oil

Displacement (cm3) 1896

Max. engine power (kW/cv) 50/68 (at 4200 rpm)

Max. engine torque (Nm/m kgf) 133/13.59 (at 2200 rpm)

Bore� Stroke (mm) 79.5�95.5

Compression ratio (cm3) 22.5:1

Injection pressure (bar) 135

Table 2Average composition of fatty acids of biodiesel

Carbon number Fatty acid Concentration (%)

C16:0 Palmitic 11.29

C18:0 Estearic 3.54

C18:1 Oleic 22.45

C18:2 Linoleic 54.62

C18:3 Linolenic 8.11

Table 3Properties and compositions of fuels

Properties No. 2 diesel oila Biodieselb

S.L. Ferreira et al. / Energy 33 (2008) 1801–18061802

However, these effects can be eliminated or reduced by theesterification of the oil to form monoesters. The transesterificationprocess removes glycerol from the triglycerides, replacing it withradicals from the alcohol used for the conversion process. Thisprocess decreases viscosity and improves the cetane number andheating value [8].

It has been reported that engine parameters, such ascompression ratio, injection timing and engine loading, have asignificant effect on the performance and emissions of dieselengine when run with biodiesel and its blend with diesel [9].

The effect of changes in the fuel injection timing at the start ofcombustion is complicated by the effect of the different fuelcetane numbers. The cetane number is an indicator of the timedelay between the fuel injection and the start of burning. Themagnitude of the unburned HC from these over-lean regions isrelated to the amount of fuel injected during the ignition delayperiod, before combustion starts. The HC emissions decrease asthe ignition delay becomes shorter [10,11]. This correlation wasunexpected, due to the large differences in volatility and oxygencontent of these fuels. The ignition delay was linearly correlated toHC emissions with no effect of fuel type [10].

This paper presents a comparative study in an attempt toobtain the concentrations of the pollutant gases (benzene,toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) (BTEX)emitted by burning diesel and diesel–biodiesel blend (B10)directly from the compression ignition engine. It is a timelycontribution to biodiesel programs in Brazil and other countriesand can really be useful for fuel and engine researchers.

Kinematics viscosity at 40 1C (cst) 2.5 a 5.5 6.0

Gross calorific values (kJ/kg) 44997 39477

Density at 20 1C (kg/l) 0.835 0.877

Flash point (1C) 38 175

Cetane number 45 57.8

Hydrocarbon types

Saturates (%) 63.4 NA

Olefins (%) 5.2 NA

Aromatics (%) 31.4 0

Max. free glycerin 0.02

Max. monoglycerides (%) 1.00

Max. diglycerides (%) 0.25

Max. triglycerides (%) 0.25

Max. total glycerin (%) 0.38

a Supplied by Ipiranga Petroleum Brazilian company.b Supplied by Soyminas-Biodiesel company.

2. Experimental part

2.1. Equipment and materials

The engine used in this study was a compression ignitionengine IDI, 1896 cm3, with four cylinders in line, aspired usingrotative injector pump-BOSCH, burning diesel oil and diesel–biodiesel blend 90:10% (v/v). The experimental setup is shown inFig. 1 and the most important engine specifications are presentedin Table 1. A hydraulic dynamometer (Schenck Dynabar) was usedto load the test engine. In the present work, the biodiesel suppliedwas prepared using soybean oil and ethanol and potassiumhydroxide (KOH) as a catalyst by the transesterification process.The average composition of fatty acids is shown in Table 2. In this

Fig. 1. Compression ignition engine burning diesel and diesel–biodiesel blend

(B10).

table, it is possible to observe the predominance of unsaturatedfatty acids, with a larger quantity of linoleic acid, and a totalcontent of saturated fatty acids occurring on the level of about14.8% [12]. Table 3 shows the properties of fuels (biodiesel andNo. 2 diesel oil). The solutions were prepared using a graduatedpipette of 1, 5 and 10 ml, a pyrex volumetric flask of 10 ml and apyrex beaker of 10 ml for chromatograph standardization. Thestandard sample utilized was a BTEX (20mg ml�1) by Supelco. Thedilutions of samples were performed with methanol 99.9% (v/v)(chromatographic degree) Mallinckrodt Baker. Tedlar bags wereused for the collection of gases. In the injection of samples, anAgilent Gases Syringe of 500ml and an Agilent Syringe of 10mlwere used.

2.2. Experimental procedure

2.2.1. Chromatograph standardization with BTEX compounds

The best conditions of temperature programming were firstlydefined to obtain the best resolution and separation of peaks forthe interesting compounds: BTEX.

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Table 4Chromatographic conditions of analysis

Column DB-5

Stationary phase 5% Phenyl/95% polydimethylsiloxane

Length 60 m

Inner diameter 0.32 mm

Film thickness 1.0mm

Oven temperature programming 60 1C after 1 min/7 1C min�1 until 165 1C

Detector FID

Detector temperature 280 1C

Injector Split

Injector temperature 220 1C

Injected volume 1ml

Column flow 2.00 ml min�1

Table 5Exposure limits of BTEX compounds for 8 h

Compound Exposure limits (mg ml�1)

Benzene 1

Toluene 200

Ethylbenzene 100

o-Xylene 100

p-Xylene 100

m-Xylene 100

Fig. 2. Gases collected from the compression ignition engine by using Tedlar bags.

Table 6Experimental operation conditions of the CI engine at 2500 rpm

Parameters Engine torque (Nm)

36.1 45.2 57.6

Diesel Condition

Fuel consumption (g/h) 2940 3488 4189

Water temperature (1C) 71.3 75.4 78.8

Engine oil temperature (1C) 97.0 99.1 100.9

B10

Fuel consumption (g/h) 2944 3523 4294

Water temperature (1C) 76.2 83.2 86.2

Engine oil temperature (1C) 94.2 98.8 99.8

S.L. Ferreira et al. / Energy 33 (2008) 1801–1806 1803

After several experiments (warm-up rates with the otherconstant variables), the oven temperature conditions that pre-sented the best resolution in chromatograph standardization withthe BTEX compounds (Table 4) were established.

According to OSHA [13], the exposure limits to the BTEX arepresented in Table 5. Therefore, the range of solution concentra-tions of the prepared sample was established for the chromato-graph standardization, mainly concerning benzene’s exposurelimit (1mg ml�1).

Based on these values for the construction of standardizationcurves, solutions of 0.125–1mg ml�1 from the standard sampleBTEX of 20mg ml�1 were prepared, observing the proportions ofeach compound: 100% benzene, 100% toluene, 100% ethylbenzene,60% m-xylene, 30% p-xylene and 10% o-xylene, i.e., 20%:20%:20%:12%:6:2% (mg ml�1), respectively. Eq. (1) was used to calculatethe sample volumes for dilution:

C1V1 ¼ C2V2 (1)

where C1 is the reference concentration (mg ml�1), V1 is requiredvolume (ml), C2 is required concentration (mg ml�1) and V2 isdilution volume (ml).

After the standardization procedure, the required volume (V1)of the samples diluted in methanol (chromatographic degree) wasadded by using volumetric flasks of 10 ml. The solutions preparedwere injected in quadruplicate. The peak area values for eachcompound were obtained using the concentration values in eachsolution for each compound in m/v percentage in the standardsample and the standardization curves were plotted.

2.2.2. Sampling

Tedlar bags totally emptied by a vacuum pump were used tosample the gases emitted from the compression ignition engine.

Fig. 2 shows the system used to collect gases from thecombustion of diesel and diesel–biodiesel mixture from theengine.

The engine used in the test and fueled with both diesel oil anddiesel–biodiesel mixture (Fig. 2) worked for 30 h. Then, the gasesemitted in the combustion were collected using Tedlar bags,varying the engine torque parameter under three conditions: 36.1,

45.2 and 57.6 Nm. The other experimental operation conditions ofCI engine are presented in Table 6. It took the Tedlar bags 10 minto be completely full.

2.2.3. Analysis of samples

The gas-emitting source used in this paper was a compressionignition engine, under one parameter considering engine torque.The tests by gas chromatography (GC) to determine the gases fromthe diesel and diesel–biodiesel mixture combustion were per-formed by injecting 400ml of the sample gases, in split mode,using a temperature programming of 60 1C for 1 min (isotherm)and with a warm-up rate of 7 1C min�1 up to a temperature of165 1C.

These gases were analyzed by a Shimadzu (GC–17A) gaschromatograph functioning with a flame ionization detector (FID).The gases were also analyzed by a Shimadzu gas chromatograph(GC/MS-QP5000).

3. Results and discussion

3.1. Chromatograph standardization with BTEX compounds

3.1.1. Calculating sample volumes for the dilution and preparation of

solutions

The sample volumes necessary for the dilution and subsequentpreparation of each solution were calculated and are shown inTable 7.

In the procedure to prepare standard solutions, a volumetricflask of 10 ml was used and the dilution was carried out withmethanol. Therefore, the standard samples were injected to

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Table 8Retention time for BTEX

Compound Retention time (min)

Benzene 7.2870.01

Toluene 9.7870.02

Ethylbenzene 12.4170.02

m-Xylene 12.6270.02

p-Xylene 13.3770.02

o-Xylene 15.3370.02

Number of replicates ¼ 4.

Table 7Sample volumes necessary for the dilution and subsequent preparation of each

solution

Point Concentration (mg ml�1) Sample volume (ml)

1 1.0 0.5

2 0.5 5.0

3 0.25 5.0

4 0.125 5.0

Table 9Equations of standardization curve, correlation coefficients and interval concen-

tration

Compound Interval

concentration

(mg ml�1)

Equations Correlation

coefficients

Benzene 0.125 a 1 Y ¼ 6113.7x+414.4 0.9923

Toluene 0.125 a 1 Y ¼ 5826.3x–485.8 0.9979

Ethylbenzene 0.125 a 1 Y ¼ 8861.2x–1034.7 0.9947

m-Xylene 0.075 a 0.6 Y ¼ 20168.3x–1366.4 0.9958

p-Xylene 0.037 a 0.3 Y ¼ 23776.2x–770.8 0.9934

o-Xylene 0.012 a 0.1 Y ¼ 137822.3x–1850.5 0.9940

Where Y—peak area of compound, x—compound concentration.

Table 10BTEX emissions from the engine burning diesel oil varying the engine torque

parameter (engine speed: 2500 rpm)

Parameter Engine torque (Nm)

36.1 45.2 57.6

Compound Concentration (mg ml�1)

Benzene 0.32370.085 0.37570.044 0.39970.014

Toluene 0.19070.019 0.23770.019 0.37670.120

Ethylbenzene 0.36570.083 0.37370.109 0.38070.136

m-xylene 0.15970.070 0.17470.089 0.25970.057

p-xylene 0.15170.068 0.15970.070 0.17070.090

o-xylene NPD NPD NPD

NPD—no peak detected, number of replicates ¼ 6.

Table 11BTEX emissions from the engine burning B10 varying the engine torque parameter

(engine speed: 2500 rpm)

Parameter Engine torque (Nm)

36.1 45.2 57.6

Compound Concentration (mg ml�1)

Benzene 0.27470.077 0.29470.031 0.30570.101

Toluene 0.21570.054 0.22670.027 0.28070.067

Ethylbenzene 0.33970.066 0.35770.090 0.37570.049

m-Xylene 0.12070.045 0.22870.103 0.27170.123

p-Xylene 0.16270.033 0.16770.046 0.20070.052

o-Xylene NPD NPD NPD

NPD—no peak detected, number of replicates ¼ 6.

S.L. Ferreira et al. / Energy 33 (2008) 1801–18061804

determine the retention time and the peak area for eachcompound (for the construction of the standardization curves).

3.1.2. Determination of the retention time for BTEX

The values obtained in terms of average and averageuncertainty (using Student’s t-test with confidence level of 95%)to determine the retention time of each VOC, i.e., BTEX arepresented in Table 8.

The standardization curves showed an excellent linear rela-tionship in the concentration range used and the analytical signalalso showed an excellent correlation coefficient near 1 (Table 9).

3.1.3. Analysis of BTEX emissions from the engine burning diesel and

diesel–biodiesel blend (B10)

As a co-elution of aromatic hydrocarbons with the saturatedhydrocarbons could occur, GC–MS analyses employing SIM mode,DB-5 column were carried out. The results obtained were veryclose to the GC–FID method, guaranteeing a higher reliability inthe identification and quantification of the interesting compounds(BTEX).

Comparing the results of the chromatographic analysis ofengine emissions burning diesel oil (Table 10) and engineemissions burning B10 (Table 11), a reduction in the benzeneand ethylbenzene concentrations was observed in the emissionsusing B10, in comparison to the emissions of pure diesel oil. This isquite evident and these experimental results strongly benefit theenvironment.

Comparing Tables 10 and 11, a reduction in the emissions ofethylbenzene and benzene was observed, evidencing a decrease inthe concentration of these two substances.

It is also relevant to observe that there was a reduction of14.5–24.5% in the benzene content, comparing the three experi-mental conditions. Although a concentration value below 1mgml�1 has been obtained, this reduction is significant, as longperiods of exposure to polluting gases can be potentially harmfulto the environment as well as to the health of humans andanimals. According to Ballesteros et al. [14], the VOCs emitted by adiesel engine are complex mixtures, containing dangerouscompounds for the environment.

This experimental fact (reduction of benzene concentration)can be explained by considering both B10 and diesel fuel

properties. It can be observed that biodiesel has a flash point of175 1C, which is higher than the value of 38 1C for the diesel fuel.Additionally, the B10 fuel is an ethyl ester with internal oxygenatoms resulting in a faster burning of the impurities under thesame conditions of use. This was also reported by Nabi et al. [15]and Kegl [16]. Any fact concerning solubility parameters ofbenzene, raising the burning potential of impurities by B10 fuel,must also be considered. Both considerations can explain why B10behaves better than the diesel fuel.

Probably, B10 results in a more complete volatilization andshorter ignition delay inside the combustion chamber due to thehigher cetane number, promoting a cleaner burning with a betterperformance in the reduction of pollutant emissions. This was alsosuggested by Pulkrabek [11] and Sureshkumara et al. [17].

As observed in Tables 10 and 11, the experimental valuesshowed an increase in the concentration for all investigatedsubstances when the engine load was increased and the enginewas fueled with either diesel oil or B10. It occurs because, by

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0.400

0.300

0.200

0.100

0.000

Con

cent

ratio

n (�

g m

l-1)

36.1

45.2

57.6

36.1

45.2

57.6

36.1

45.2

57.6

36.1

45.2

57.6

36.1

45.2

57.6

36.1

45.2

57.6

Benzene Tolune Ethylbenzene m-xylene p-xylene o-xylene

Engine Torque (Nm)

B10

Diesel

Fig. 3. Comparison of the results obtained from emissions at different engine torque using diesel and diesel–biodiesel blend (engine speed: 2500 rpm).

S.L. Ferreira et al. / Energy 33 (2008) 1801–1806 1805

increasing the engine torque, the engine needs a tantamountgreater fuel injection and, consequently, the emissions ofpollutant gases increase.

Moreover, a reduction in the toluene concentration wasobserved in the gaseous emissions when the engine burned theB10 comparatively to pure diesel oil, under the conditions of theengine torque of 45.2 and 57.6 Nm.

The increase in the concentration of p-xylene can be con-sidered in the range of average uncertainty. This increase was notstatistically significant. Among the xylenes, only the o-xylene wasnot detected in the samples of the gases analyzed due todifficulties in resolving the chromatography peak. Additionally,the experiments also suggest a reduction in the concentration ofthe m-xylene when the engine burns B10 mixture comparativelyto pure diesel oil under the condition of 36.1 Nm, as described inTables 10 and 11.

The comparison of the results obtained from emissions atdifferent loads using diesel and diesel–biodiesel blend (B10) isalso shown in Fig. 3.

The reduction in the emission of other compounds can also beexplained by using the same reasoning suggested for benzene.

The concentration values of BTEX emitted from the engineburning diesel oil and burning B10 mixture were also compared.The results in the present work showed an appreciable reductionin the emissions. A reduction in VOC was observed in some otherexperimental papers cited in the literature [18–21]. The valuesfound by these authors ranged from 22% to 38%, 29%, 21.5% and21%. These reductions can be explained by the fuel properties andengine operation conditions, such as increase in oxygen content inthe fuel, contributing to complete oxidation, cetane number,injection timing and compression ratio.

4. Conclusions

The analysis of the gases emitted from the compressionignition engine by GC showed good results with a good linearityin the methodology employed.

The results using compression ignition engine with theaddition of an alternative biofuel (biodiesel) to a traditional fuel(diesel) showed a reduction in the pollutants emissions, asdescribed in the literature.

For benzene, an average concentration reduction of about19.5% was obtained under the three conditions of engine torqueused in the experiments. This reduction is sufficiently significantsince benzene is a carcinogenic compound. The results are in goodagreement, showing the efficiency of adding biodiesel to diesel.

Acknowledgements

The authors are indebted to the financial support given byCNPq. They would also like to acknowledge Leonardo A. Valentin,Douglas W. Miwa, Angela Cristina P. Giampedro, Marcus Vinıcius I.da Silva and Delson L. Modolo (engine researcher) for the valuablesuggestions and help to this work, Center of Thermal and FluidEngineering-EESC for the supplied infrastructure and Soyminas-Biodiesel company for supplying the biodiesel.

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