PCa

IC

a

ARRAA

KABCJPE

dcFhp2d

h0

Industrial Crops and Products 57 (2014) 132–140

Contents lists available at ScienceDirect

Industrial Crops and Products

jo u r n al homep age: www.elsev ier .com/ locate / indcrop

erformance and emission characteristics of a CI engine fueled withocos nucifera and Jatropha curcas B20 blends accompanyingntioxidants

.M. Rizwanul Fattah ∗, H.H. Masjuki, M.A. Kalam, M.A. Wakil, H.K. Rashedul, M.J. Abedinentre for Energy Sciences, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

r t i c l e i n f o

rticle history:eceived 16 November 2013eceived in revised form 8 March 2014ccepted 19 March 2014vailable online 16 April 2014

eywords:ntioxidantiodieseloconut biodiesel

atropha biodieselerformancemission

a b s t r a c t

A biodiesel is a clean-burning alternative fuel. It has drawn attention of the energy researchers over thelast two decades as a solution to problems of environmental concerns, rising fossil fuel price, increas-ing dependency on foreign energy sources. However, it is susceptible to oxidative degradation due toautoxidation in the presence of oxygen, which hinders its widespread use. The addition of an antioxi-dant to it reduces this phenomenon significantly. It is expected that antioxidants may affect the cleanburning characteristic of a biodiesel. Coconut (Cocos nucifera) and Jatropha (Jatropha curcas) are twopromising feedstock growing in the South-East Asian region. This paper presents an experimental inves-tigation of the effect of addition of an antioxidant on the performance and emission characteristics of afour-cylinder diesel engine fueled with 20% blends of two biodiesels (CB20 and JB20). A biodiesel fromcoconut oil was produced by transesterification process using potassium hydroxide (KOH) as a catalyst.Jatropha biodiesel production was preceded by an esterification step, using sulfuric acid as a catalyst.To study the antioxidant effect, two low-cost synthetic antioxidants, 2(3)-tert-butyl-4-methoxyphenol(BHA) and 2,6-di-tert-butyl-4-methylphenol (BHT), at a concentration of 2000 ppm, were used in thisstudy. Addition of antioxidants increased their oxidation stability without causing any negative effect onother physicochemical properties. BHT and BHA were found to increase the stability of JB20 and CB20,respectively. Performance results indicate that JB20 and CB20 showed, respectively, 0.95% and 2.97%lower mean brake power (BP) and 5.02% and 4.76% higher mean brake-specific fuel consumption (BSFC)than to diesel. The addition of antioxidants increased BP and reduced BSFC slightly. Emission results show

that untreated JB20 and untreated CB20 increased nitrogen monoxide (NO) emission by 5.52% and 8.02%,but reduced carbon monoxide (CO) and hydrocarbon (HC) emission. Antioxidant-treated blends reducedNO emission by 2.6–5.0%, but increased CO emission by 4.9–20.8% and HC emission by 23.2–40.2% com-pared to B20 depending on feedstock. Thus, antioxidant-treated JB20 and CB20 blends can be used indiesel engines without any modification.

© 2014 Elsevier B.V. All rights reserved.

Abbreviations: ACS, American Chemical Society; AR, Analytical Reagent; BHA, 2(3)-tert-butyl-4-methoxyphenol; BHT, 2,6-di-tert-butyl-4-methylphenol; BP, brake pow-er; BSEC, brake specific energy consumption; BSFC, brake specific fuel consumption; CAS No., Chemical Abstracts Service registry number; CBD, coconut biodiesel; CFPP,old filter plugging point; CN, cetane number; CO, carbon monoxide; CP, cloud point; DPPD, N,N′-diphenyl-1,4-phenylenediamine; EHN, 2-ethylhexyl nitrate; FA, fatty acid;

AAE, fatty acid alkyl esters; FFA, free fatty acid; FRIM, Forest Research Institute Malaysia; IP, induction period; IV, iodine value; JBD, Jatropha biodiesel; KOH, potassiumydroxide; HHV, higher heating value; NPPD, N-phenyl-1,4-phenylenediamine; NaOH, sodium hydroxide; PAH, polyaromatic hydrocarbon; PM, particulate matter; PG,ropyl 3,4,5-trihydroxybenzoate (propyl gallate); PP, pour point; PY, benzene-1,2,3-triol (pyrogallol); TBHQ, 2-tert-butylbenzene-1,4-diol (tert-butyl hydroquinone); CB20,0% CBD + 80% diesel; CB20 BHA, 20% CBD + 80% diesel + 2000 ppm BHA; CB20 BHT, 20% CBD + 80% diesel + 2000 ppm BHT; JB20, 20% JBD + 80% diesel; JB20 BHA, 20% JBD + 80%iesel + 2000 ppm BHA; JB20 BHA, 20% JBD + 80% diesel + 2000 ppm BHA.∗ Corresponding author at: Department of Mechanical Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia. Tel.: +60 3 79674448; fax: +60 3 79675317.

E-mail address: rizwanul.buet@gmail.com (I.M. Rizwanul Fattah).

ttp://dx.doi.org/10.1016/j.indcrop.2014.03.022926-6690/© 2014 Elsevier B.V. All rights reserved.

al Crop

1

(pfdcrtpspafiH(dseoe

aaepSdwtiRdcracPamtItoRre

–

1

ciopasykc

rM

I.M. Rizwanul Fattah et al. / Industri

. Introduction

Biodiesels refer to monoalkyl esters of long-chain fatty acidsFAs) prepared from plant oils, such as soybean oil, rapeseed oil,alm oil, coconut oil, sunflower oil, and Jatropha oil, and animalats, such as poultry fat, and tallow fat. Biodiesels produced fromifferent sources have different properties due to their dissimilar FAomposition (Zuleta et al., 2012). Increasing fossil oil prices, limitedeserve of fossil fuel, and environmental concerns have boosted uphe research on biodiesel fuels. Advantages of a biodiesel over aetroleum diesel fuel include derivation from renewable feedstock,uperior lubricity and biodegradability, lower toxicity, higher flashoint and cetane number (CN), ability to blend with a petrodieselt any proportion, adaptability to engines without major modi-cation, positive energy balance, and reduced emissions of CO,C, particulate matter (PM), and polycyclic aromatic hydrocarbon

PAH) (Hoekman and Robbins, 2012; Kivevele et al., 2011b). Itsisadvantages include limited feedstock availability, higher feed-tock cost, inferior oxidative and storage stability, lower volumetricnergy content, inferior cold flow properties, higher consumptionf specific fuels, and higher emission of nitrogen oxide (Özcanlıt al., 2011).

The major drawback of a biodiesel fuel is its inferior oxidativend storage stabilities. The primary mechanism of degradation isutoxidation in presence of atmospheric oxygen (Rizwanul Fattaht al., 2014a). Biodiesels are more susceptible to degradation com-ared to fossil diesel because of FA chain unsaturation (Pullen andaeed, 2012). This degradation is exasperated if two or more carbonouble bonds (polyunsaturation) are present in the FA chain. Oneay of increasing the resistance of a biodiesel against autoxida-

ion without modifying the fuel properties significantly is to treatt with antioxidants and thus stabilizing it (Fernandes et al., 2013;amos et al., 2009). According to their modes of action, antioxi-ants are classified as free radical terminators, metal ion chelatorsapable of catalyzing lipid oxidation, and oxygen scavengers thateact with oxygen in closed systems (Shahidi et al., 1992). Thesere primary antioxidants that react with high-energy lipid radi-als to convert them to thermodynamically more stable products.henolic antioxidants, which are the most used antioxidants, andmine-type antioxidants belong to the group of free radical ter-inators. The term, “stabilization factor” is often used to denote

he effectiveness of an antioxidant, where F = IPx/IPo, where IPx andPo denote, respectively, the induction period in the presence andhat in absence of an antioxidant (Loh et al., 2006). The–OH groupf antioxidants scavenges reactive radicals (e.g., peroxyl radicals,OO•). The resulting phenoxyl radical (R–O•) tends to be poorlyeactive and limits oxidative reaction (Reaction (1)) (Varatharajant al., 2011).

OH + ROO• → R–O• + ROOH (1)

.1. Botanical description of Cocos nucifera and Jatropha curcas

C. nucifera L. or coconut palm is a member of the family Are-aceae. It is native to tropical eastern regions. However, it is grownn the Asian continent, Central and South America, and some partsf Africa. It is a large palm, growing up to a height of 30 m, withinnate leaves being 4–6 m long and pinnae 60–90 cm long. It has

single trunk, 20–30 m tall. Its cultivation requires sandy, salineoils with abundant sunlight and regular rainfall throughout theear. A coconut palm tree can yield up to 75 fruits per year. It isnown for the versatile uses of its different parts in many domestic,

ommercial, and industrial applications.

J. curcas L. is a poisonous, semi-evergreen shrub or small tree,eaching a height of 6 m. The place of origin of J. curcas plant isexico. Portuguese traders spread it across Asia and Africa as a

s and Products 57 (2014) 132–140 133

hedge plant. It belongs to the family Euphorbiaceae. It can growon areas of poor soil and low rainfall (250 mm a year) (Sarin et al.,2007). However, it grows well with more than 600 mm rainfall peryear. In Malaysia, it is known as “Jarak Pagar” (Mofijur et al., 2012).These trees are easy to establish; they grow relatively quickly andare immune to drought. Under optimal cultivation conditions, eachmature tree produces about 4 kg of seed per year on average. It has along productive period of around 30–50 years (Banapurmath et al.,2008).

1.2. Objectives of this study

In this study, two promising biodiesel feedstock of Malaysianorigin, namely coconut (C. nucifera) and Jatropha (J. curcas), wereused. Recently, many studies have published reports on the produc-tion of coconut biodiesel (CBD) and its use as a fuel in diesel engines(Atabani et al., 2013a; Liaquat et al., 2013). In addition, manyresearchers have discussed the production of Jatropha biodiesel(JBD) and its application in diesel engines (Kannan et al., 2012;Mofijur et al., 2013). Moreover, the effect of using additives forJBD has also been reported by researchers (Palash et al., 2014;Varatharajan et al., 2011). However, the effect of the addition ofan antioxidant to CBD has not yet been discussed. Besides, addi-tion of antioxidants up to a concentration of 1000 ppm has beenreported by many authors (Ileri and Koc ar, 2013; Ryu, 2010). Thus,in this study, antioxidants up to a concentration of 2000 ppm wereadded to 20% of both biodiesels. More than 90% of FAs of coconutoil are saturated and only around 10% are unsaturated, making itsusceptible to oxidative degradation during storage (Kumar et al.,2013). As addition of an antioxidant is preferred for better oxidativestability, a proper investigation of its effect on engine perfor-mance and emission is needed. It has been reported that both2(3)-tert-butyl-4-methoxyphenol (BHA) and 2,6-di-tert-butyl-4-methylphenol (BHT) show moderate inhibition to many biodiesels(Rizwanul Fattah et al., 2014a). The present study is an endeavor todemonstrate the use of antioxidants BHA and BHT with 20% CBDand 20% JBD blends, and to compare their effects on the perfor-mance and emission characteristics of an indirect-injection dieselengine.

1.3. Literature review

Ileri and Koc ar (2014) reported the effects of addition of fourantioxidants on the emission characteristics of a turbochargedfour-cylinder diesel engine. Antioxidants, viz. EHN, BHA, BHT, and2-tert-butylbenzene-1,4-diol (TBHQ), were added to 20% canolabiodiesel. They reported 1.21–4.05% decrease in average NOx emis-sion and 0.66–19.72% increase in average CO emission compared toB20. However, in case of HC, antioxidants did not show any specifictrend. They found EHN as the best NOx reducing additive, with neg-ative impact on CO and HC emission. Rizwanul Fattah et al. (2014b)reported the effect of addition of BHA and BHT (1000 ppm con-centration each) to 20% palm biodiesel on the performance andemission characteristics of a turbocharged indirect-injection dieselengine. They reported a marginal increase in brake power anddecrease in BSFC compared to B20 without antioxidants.

Varatharajan and Cheralathan (2013) studied the effect of addi-tion of two aromatic amine antioxidants (DPPD and NPPD) tosoybean biodiesel on the emission criteria of a single-cylinder dieselengine. They found 9.35% reduction of NO emission, with a penaltyof 9.09% increase in CO and 10.52% increase in HC, using a DPPD-added 20% soybean biodiesel. In another study, Varatharajan et al.

(2011) investigated the effect of antioxidants on NOx emissionfrom a single-cylinder diesel engine using a JBD fuel containing0.025 mass% of additives, p-phenylenediamine, ethylenediamine,l-ascorbic acid, �-tocopherol acetate, and BHT. Test results showed

134 I.M. Rizwanul Fattah et al. / Industrial Crops and Products 57 (2014) 132–140

Table 1Properties of used chemicals.

Chemical Chemical structure CAS number Assay (%) Molecularweight (g/mol)

Melting point(◦C)

Grade

BHA

2(3)-tert-Butyl-4-methoxyphenol

25013-16-5 ≥98.5 180.24 58–60

BHT

CH3

CH3

CH3

CH3

OHCH3

CH3CH3

2,6-di-tert -butyl-4-methylpheno l

2,6-di-tert-Butyl-4-methylphenol

128-37-0 ≥99.0 220.35 69–73

Methanol CH3OH 67-56-1 ≥99.9 32.04 −98 ACSSulfuric acid H2SO4 7664-93-9 ≥98 98.08 AR

10-5857-82

A

t4ec

tbHbobaoewuoa

2

2

tuapaT

2

e

Potassium hydroxide KOH 13Sodium sulfate (anhydrous) Na2SO4 77

CS: American Chemical Society; AR: Analytical Reagent.

hat the addition of p-phenylenediamine led to a mean reduction of3.55% in NOx emission compared to that by a neat biodiesel. How-ver, addition of antioxidants increased the emission of HC and COompared to that by a neat biodiesel as well as blends.

Kivevele et al. (2011a) reported that a biodiesel dosed withhe antioxidant PY showed lower BSFC compared to an untreatediodiesel, while having less effect on CO, HC, and NOx emission.owever, at the full-load condition, heat release by the stabilizediodiesel is similar to that by diesel. Ryu (2010) studied the effectf addition of different concentrations of antioxidants to a soybeaniodiesel. Tert-butylhydroquinone (TBHQ) was the best stabilizermong the five tested antioxidants. Using various concentrationsf TBHQ and PG, Ryu analyzed the combustion, performance, andmission of an engine. With the use of TBHQ, no significant changeas observed in smoke, HC, and NOx emission compared to thentreated diesel. Hess et al. (2005) studied the effects of additionf different antioxidants to 20% soybean biodiesel on NOx emissionnd found that addition of BHA and BHT reduced NOx emission.

. Materials and methods

.1. Materials

In this study, crude coconut and Jatropha oils purchased fromhe local market were used to produce a biodiesel. The antioxidantssed were BHA, BHT, and TBHQ. These antioxidants exhibit moder-te inhibitory effect on biodiesel oxidation. Methanol, sulfuric acid,otassium hydroxide (KOH), anhydrous sodium sulfate (Na2SO4),nd qualitative filter papers were used for biodiesel production.able 1 shows the properties of used chemicals.

.2. Biodiesel production

In this study, CBD was produced using an alkali-catalyzed trans-sterification process. In this process, crude coconut oil was placed

-3 ≥85.0 56.11 360 ACS-6 ≥99.0 142.04 884 ACS

in a jacket reactor along with methanol (6:1 molar ratio) and KOH(1% w/w of oil). Temperature was maintained at 60 ◦C using a cir-culating water bath. The reaction was carried out for 2 h, and themixture was stirred at 1100 rpm using a motor stirrer. Afterward,a separation time of 12 h was given to this mixture to separateglycerin from methyl ester or biodiesel. The methyl ester sepa-rated from glycerin was washed with distilled water to remove theentrained impurities and glycerin. In this process, 50% (v/v) dis-tilled water at 60 ◦C was sprayed over ester and shaken gently. Theopaque lower layer containing water and impurities were takenout. Then, the methyl ester was distilled under a vacuum at 65 ◦Cfor 1 h using a rotary evaporator to remove water and methanol.Finally, the methyl ester was dried using anhydrous Na2SO4 for 3 hand filtered using qualitative filter papers.

Crude Jatropha oil had a high free fatty acid (FFA) content of 8%,i.e., an acid value of 16 mg KOH/g. Ramadhas et al. (2005) showedthat, if the acid value of oil is less than 4, then it can undergo trans-esterification. As the FFA content was very high, conversion of thisoil to the biodiesel through one-step alkaline transesterificationwas not possible and needed a pretreatment. Esterification of FFAwith methanol in the presence of acidic catalysts is the most com-monly used pretreatment method (Koh and Mohd. Ghazi, 2011).Thus, for producing JBD, first an acid-catalyzed pretreatment pro-cess was carried out. In this process, crude Jatropha oil was placedwith methanol (in 12:1 molar ratio) and H2SO4 (1% v/v) in the samesetup. Temperature was maintained at 60 ◦C for 3 h, and the mix-ture was stirred at 1100 rpm. Afterward, a separation time of 1 hwas given to this mixture to separate out the esterified productand catalyst layer. After separation, the lower layer is taken outto remove excess methanol and water using a rotary evaporator.The yield of this step is about 98%. Transesterification of the ester-

ified product and its purification were then carried out using theabovementioned method.

Table 2 shows a summary of the equipment used in this studyto measure the physicochemical properties of CBD, JBD, and their

I.M. Rizwanul Fattah et al. / Industrial Crops and Products 57 (2014) 132–140 135

Table 2List of equipment used in the characterization of fuels.

Property Equipment Manufacturer Standardmethod

ASTMD6751limit

Accuracy

Kinematic viscosity at 40 ◦C SVM 3000—automatic Anton Paar, UK D7042 1.9–6.0 ±0.35%Dynamic viscosity at 40 ◦C SVM 3000—automatic Anton Paar, UK D7042 n.s. ±0.35%Viscosity index SVM 3000—automatic Anton Paar, UK D2270Density at 40 ◦C SVM 3000—automatic Anton Paar, UK D7042 n.s. 0.0005 g/cm3

Density at 15 ◦C DM40 LiquiPhysicsTM density meter Mettler Toledo, Switzerland D4052 ±0.1 kg/m3

Flash point Pensky-Martens flash point—automatic NPM 440 Normalab, France D93 130 min ±0.1 ◦COxidation stability 873 Rancimat—automatic Metrohm, Switzerland D675 3 h ±0.01 hHigher heating value C2000 basic calorimeter—automatic IKA, UK D240 n.s. ±0.1% of readingCloud point Cloud and Pour point tester—automatic NTE 450 Normalab, France D2500 Report ±0.1 ◦CPour point Cloud and Pour point tester—automatic NTE 450 Normalab, France D97 ±0.1 ◦CCFPP Cold filter plugging point—automatic NTL 450 Normalab, France D6371 n.s.

M

n

bpCr

S

I

C

wdm

2

gi3oo252csf

TP

Acid value G-20 Rondolino automated titration system

.s. = not specified in the ASTM test method.

lends. Table 3 shows the properties of crude oil and the biodieselroduced. The saponification number (SN), iodine value (IV), andN of the produced biodiesel were calculated using Eqs. (2)–(4),espectively (Mohibbe Azam et al., 2005).

N =∑(

560 × Ai

MWi

)(2)

V =∑(

254 × D × Ai

MWi

)(3)

N = 46.3 +(

5458SN

)− (0.225 × IV) (4)

here Ai is the percentage of each component, D is the number ofouble bonds, and MWi is the mass of each component. Molecularass of each component is given in Table 4.

.3. Fatty acid composition

A biodiesel sample (1 �L) was injected into a gas chromato-raph (Shidmadzu, GC-2010A series) equipped with a flameonization detector (FID) and a BPX70 capillary column of0 m × 0.25 �m × 0.32 mm inner diameter. An initial temperaturef 140 ◦C was held for 2 min, which was then increased at a ratef 8 ◦C/min to 165 ◦C, 3 ◦C/min to 192 ◦C, and finally 8 ◦C/min to20 ◦C. The column was held at the final temperature for another

min. The oven, injector, and detector ports were set at 140 ◦C,

40 ◦C, and 260 ◦C, respectively. The carrier gas was helium with aolumn flow rate of 1.10 mL/min, with a split ratio of 50:1. Table 4hows the composition of CBD and JBD produced. CBD has beenound to contain 91.3% saturated, 7.1% monounsaturated, and 1.5%

able 3hysicochemical properties of crude oil and the biodiesel produced.

Property Unit Coconut oil CB

Kinematic viscosity at 40 ◦C mm2/s 27.420

Dynamic viscosity at 40 ◦C mPa s 24.908

Density at 15 ◦C kg/m3 908.5 87Viscosity index 167.4 28Higher heating value MJ/kg 37.806 3Flash point ◦C 300.5 12Oxidation stability at 110 ◦C h 6.99 1Cloud point ◦C 17 −Pour point ◦C 19 −Cold filter plugging point ◦C 23 −Acid value mg KOH/g 3.5

Saponification number 24Iodine value g I2/100 g

Cetane number 6

a Data obtained from Atabani et al. (2013b).b Data obtained from Ong et al. (2013).

ettler Toledo, Switzerland D664 0.5 max ±0.001 mg KOH/g

polyunsaturated methyl esters, whereas JBD contains 24.3% satu-rated, 42.6% monounsaturated, and 33.1% polyunsaturated methylesters. Higher saturation signifies higher cetane number and oxi-dation stability but lower iodine value and CFPP (Ramos et al.,2009).

The experimental investigation was carried out on a 2.5 Lfour-cylinder, four-stroke, water-cooled, turbocharged, indirect-injection diesel engine. The engine had a compression ratio of 21:1and was capable of producing 55 kW power at a constant speed of4000 rpm. It had a swirl-type combustion chamber, to which fuelwas injected using a distribution-type jet pump. The test enginewas directly coupled to a Froude Hofmann AG250 eddy currentdynamometer. The engine fuel system was modified by adding sep-arate tanks with two-way valves, which allowed rapid switchingof fuels. To carry out tests using biodiesel blends, the engine wasrun with diesel until a steady operating condition was achieved.Then the fuel was changed to a biodiesel blend. Data acquisitionwas started after consumption of a sufficient amount of blend fuel,to ensure complete removal of residual diesel from the fuel line.After each test, the engine was again run with diesel to drain out allthe blends in the fuel line. This procedure was followed for all theblends. Accuracies of engine speed, engine power, and fuel flowmeasurement are ±1 rpm, ±0.1 kW, and ±0.089 l/h, respectively.The test fuels used were fossil diesel, 20% JBD in diesel (JB20), and20% CBD in diesel (CB20). To determine the effect of an antioxi-dant, 2000 ppm of BHA and BHT was added to both JB20 and CB20

(JB20 BHA, JB20 BHT, CB20 BHA, and CB20 BHT). It is prominent thatantioxidants are consumed at a constant rate during the inhibitionperiod, and when all the antioxidants are used up, the inhibitionperiod is over and oxidation proceeds as rapidly as that in the

D CBDa Jatropha oil JBD JBDb

2.8550 3.1435 34.072 4.2684 3.912.4479 – 30.693 3.67395.4 – 918.9 878.8 879.02.1 230.8 199.7 220.78.284 38.300 39.420 40.899 40.4272.5 118.5 210.5 176.5 161.52.38 8.01 1.2 8.41 9.405 1 12 3 34 −4 1 2 21 −1 22 1 00.1 16 0.2 0.249.3 192.69.2 93.8 1056.1 53.5 58.2

136 I.M. Rizwanul Fattah et al. / Industrial Crops and Products 57 (2014) 132–140

Table 4Fatty acid composition of various biodiesels (wt.%).

Fatty acid ester Structure Molecular mass Formula CBD CBDa JBD JBDb

Methyl octanoate 8:00 158.24 CH3(CH2)6COOCH3 6.5 7.7 n.d. n.d.Methyl decanoate 10:00 186.29 CH3(CH2)8COOCH3 5.4 6.4 n.d. n.d.Methyl laurate 12:0 214.34 CH3(CH2)10CO2CH3 47.4 48.6 n.d. 0.1Methyl myristate 14:0 242.40 CH3(CH2)12COOCH3 18.6 17.8 0.1 0.1Methyl palmitate 16:0 270.45 CH3(CH2)14CO2CH3 10.4 8.9 17.7 13.0Methyl palmitoleate 16:1 268.43 CH3(CH2)5CH CH(CH2)7COOCH3 n.d. n.d. 0.8 0.7Methyl stearate 18:0 298.50 CH3(CH2)16CO2CH3 2.7 2.2 6.4 5.8Methyl oleate 18:1 296.49 CH3(CH2)7CH CH(CH2)7CO2CH3 6.9 6.8 41.8 44.5Methyl linoleate 18:2 294.47 CH3(CH2)3(CH2CH CH)2(CH2)7CO2CH3 1.9 1.6 32.9 35.4Methyl linolenate 18:3 292.46 CH3(CH2CH CH)3(CH2)7COOCH3 n.d. n.d. 0.1 0.3Methyl arachidate 20:0 326.56 CH3(CH2)18COOCH3 n.d. n.d. 0.1 0.2

n

aob1

ouREgnlT±wpmbw

3

3

f

aCLrdt(osio

OH

.d. = not detected.a Data obtained from Jiang and Tan (2012).b Data obtained from Ong et al. (2013).

bsence of an antioxidant (Niki, 1987). Hence, a higher amountf antioxidants are used to study their effects. Test fuels werelended using a homogenizer device at a speed of 3000 rpm for0 min.

The engine was operated between 1000 and 4500 rpm, at a stepf 500 rpm, at the 100% load condition. Fuel flow was measuredsing a KOBOLD ZOD positive-displacement-type flow meter. AEO-dCA data acquisition system collected the data automatically.xhaust emissions were measured using a BOSCH BEA-350 exhaustas analyzer. In this equipment, the CO measuring instrument usesondispersive infrared detectors, NO analyzer uses a heated chemi-

uminescence detector (CLD), and HC analyzer uses a heated FID.he accuracies of CO, CO2, HC, and NO are ±0.001 %vol., ±0.01 %vol.,1 ppm vol., and ±1 ppm vol., respectively. A statistical analysisas carried out by applying two-sided Student’s t-test for inde-endent variables to test for significant differences between theean values of samples using Microsoft Excel 2013. Differences

etween mean values at a level of p = 0.05 (95% confidence level)ere considered statistically significant.

. Results and discussions

.1. Effect of antioxidant addition on fuel properties

Table 5 shows some important characteristics of the testeduels. The kinematic viscosity of JB20 and CB20 are 3.2530

nd 2.9746 mm2/s, respectively. Thus, the viscosity of JB20 andB20 is 5% higher and 3.2% lower, respectively, than that of diesel.ower kinematic viscosity indicates that the fluid receives loweresistance during its flow though the fuel line, resulting in a lesserelay in the start of injection (Hoekman et al., 2012). In addi-ion, lower kinematic viscosity also leads to better fuel atomizationHas imoglu et al., 2008). Hence, better combustion efficiency is

CH3

R R

OH

LOO LO•

R = tert-bu tyl

bserved for coconut blends, which ultimately ensure better emis-ion characteristics. Viscosity affects the atomization of a fuel uponnjection into the combustion chamber and thereby the formationf engine deposits (Berman et al., 2011). The higher the viscosity,

the greater the tendency of the fuel to cause such problems. Addi-tion of antioxidants increases both density and kinematic viscositycompared to B20. Addition of BHT imparts greater kinematic vis-cosity than that of BHA, for both JB20 and CB20 blends. This resultsin a slight delay in the start of injection, and hence a delay in thestart of combustion of antioxidant-stabilized blends (Lapuerta et al.,2008). Addition of antioxidants to JB20 and CB20 reduces theirHHVs slightly (0.08%). Flash point is reciprocally related to fuelvolatility. As CBD contains lighter constituents (≤C12) (Table 4),its flash point is inherently lower (122.5 ◦C), which does not meetthe ASTM D6751 specification of 130 ◦C. However, CB20 meets theASTM D7467 specification. The CN is a measure of a fuel’s autoigni-tion quality characteristics. Both JBD and CBD possess higher CNscompared to diesel, meeting the ASTM D6751 specification of ≥47.The stability periods of pure JBD and CBD against oxidation are 8.41and 12.38 h, respectively. The high saturation percentage of CBDimparts greater stability. These meet both the ASTM D6751 and theEN 14214 standard specifications of oxidation stability. Blending of20% JBD and CBD with diesel (B20) increases the stability to 36.98and 73.16 h, respectively; these meet both the ASTM D7467 specifi-cation limit of 6 h and the EN 590 limit of 20 h (Mofijur et al., 2013).Antioxidants BHA and BHT provide stabilization depending on thefeedstock. As can be seen from Table 5, BHA provides greater stabi-lization (F = 1.31) to CB20, whereas BHT does so for JB20 (F = 1.85).Antioxidants form stable radical intermediates with moderate res-onance delocalization (Reaction (5)), which hinders the oxidationof fuels (Shahidi et al., 1992).

CH3

R R

O

R R

OLOO•

H3C OOL

(5)

3.2. Analysis of engine performance

3.2.1. Brake powerThe brake power outputs at different speeds with different test

fuels at the full-load condition are shown in Fig. 1. It can be seen thatbrake power increases steadily up to 4000 rpm and then decreases.The maximum brake powers recorded at this speed for diesel,JB20, JB20 BHA, JB20 BHT, CB20, CB20 BHA, and CB20 BHT were

48.9, 48.5, 48.7, 48.6, 47.1, 47.4, and 47.3 kW, respectively. Thus,JB20 and CB20 produce, respectively, 0.82% and 3.68% reduction inthe maximum power output. These changes were significant at alevel of 0.01 < p < 0.02. The average brake power recorded for the

I.M. Rizwanul Fattah et al. / Industrial Crops and Products 57 (2014) 132–140 137

Table 5Fuel characteristics of biodiesel blends and fossil diesel.

Property Diesel JB20 JB20 BHA JB20 BHT CB20 CB20 BHA CB20 BHT ASTM D7467a

Higher heating value (MJ/kg) 44.468 43.406 43.368 43.390 42.813 42.761 42.776Kinematic viscosity at 40 ◦C (mm2/s) 3.0738 3.2530 3.2557 3.2750 2.9746 2.9835 2.9946 1.9–4.1Dynamic viscosity at 40 ◦C (mPa s) 2.5501 2.7167 2.7199 2.7372 2.4833 2.4922 2.5008Density at 40 ◦C (kg/m3) 829.6 835.1 835.6 835.3 834.8 835.2 835Oxidation stability (h) 59.1 36.98 39.33 68.47 73.16 96.13 94.47 6 (min)Flash point (◦C) 69.5 79.5 80.5 80.5 78.5 79.5 79.5 52 (min)Cloud point (◦C) 8 8 8 8 7 7 7 ReportPour point (◦C) 7 3 3 3 −15 −15 −15

e3doprHwlJ0Caaf2act

3

dtat(tt

Higher density and viscosity lead to decreased atomization and fuel

CFPP (◦C) 8 8 8

a Data obtained from de Guzman et al. (2010).

ntire speed range for these fuels were 34.64, 34.31, 34.51, 34.48,3.61, 33.81, and 33.78 kW, respectively. Thus, JB20 and CB20 pro-uce, respectively, 0.95% and 2.97% reduction in the average powerutput. The low brake powers obtained using these blends, in com-arison with those obtained using diesel, is mainly due to theirespective higher heating values (HHVs) (Kalam et al., 2011). TheHV of CB20 was 1.37% lower than that of JB20. This togetherith a lower density and viscosity of CB20 resulted in additional

oss in power due to higher leakages in the pump compared toB20 (Karabektas et al., 2008). Addition of antioxidants results in.5–0.6% increase in the average brake power output for JBD andBD blends, which can be attributed to an increase in the densitynd kinematic viscosity of these blends. A higher density of thentioxidant-treated blends results in the injection of a large mass ofuel into the engine for the same fuel volume (Gumus and Kasifoglu,010). Again, the more the viscosity of the blend, the less the leak-ge in the fuel pump (Gürü et al., 2010). The higher mass flowompensates the lower heat energy content of the antioxidant-reated blends (Hazar and Aydin, 2010).

.2.2. Brake specific fuel consumptionThe brake-specific fuel consumption (BSFC) of a diesel engine

epends on the relationship between the volumetric fuel injec-ion system, fuel density, viscosity, and HHV (Qi et al., 2010). Withn increase in speed from 1000 to 2500 rpm, consumption of all

he fuels decreases due to an increase in the atomization ratioOzsezen et al., 2008). From 2500 to 4500 rpm, the fuel consump-ion increases due to decreasing volumetric efficiency. Fig. 2 showshe variation of BSFC with engine speed for the test fuels. The

Fig. 1. Variation of the brake power (BP) with engine speed for the test fuels.

8 7 7 7

average BSFC for diesel, JB20, JB20 BHA, JB20 BHT, CB20, CB20BHA, and CB20 BHT are 346.60, 364.00, 361.13, 361.14, 363.08,360.64, and 361.07 g/kWh, respectively. It has been seen that BSFCof both JB20 and CB20 is, respectively, about 5.02% and 4.76% higherthan that of diesel fuel, primarily because of their lower HHVs andhigher density (Jindal et al., 2010; Sayin, 2010). These changes werefound to be significant at p < 0.01. The higher fuel consumption canbe attributed to the volumetric effect of a constant fuel injectionrate together with the higher viscosity of biodiesel blends (Boudyand Seers, 2009). Addition of an antioxidant helps in decreasingBSFC. Addition of BHA and BHT to JB20 resulted in a mean reduc-tion of BSFC by 0.79% and 0.78%, respectively. Addition of theseantioxidants to CB20 led to 0.67% and 0.55% reductions of BSFC,respectively. This can be attributed to the higher power output withsimilar fuel consumption with lower calorific value. This findingconcurs with previous study results (Kivevele et al., 2011a; Ryu,2010).

3.2.3. Brake thermal efficiencyFig. 3 shows the variation of brake thermal efficiency (BTE)

with engine speed for the test fuels. A lower BTE was observed forbiodiesel blends with or without antioxidants compared to diesel.The higher viscosity, density, and HHV of biodiesel blends thanthose of diesel fuel are the primary causes of their lower efficiency.

vaporization, resulting in an uneven combustion compared to thatof diesel fuel (Banapurmath et al., 2008). These result in a slowercombustion as well as antagonize the benefits of the presence of

Fig. 2. Variation of brake specific fuel consumption (BSFC) with engine speed forthe test fuels.

138 I.M. Rizwanul Fattah et al. / Industrial Crops and Products 57 (2014) 132–140

Ff

oCdaB2ptsAilt

3

3

dsoBaiprbbaAdcd2htNOri

et al., 2013; Puhan et al., 2007). A higher CN exhibits a shorter igni-tion delay and allows better combustion. Then the oxygen contentof the biodiesel comes into play, which enhances the combus-tion process. A high oxygen content ensures a higher in-cylinder

ig. 3. Variation of brake thermal efficiency (BTE) with engine speed for the testuels.

xygen in enhancing the combustion process (Aliyu et al., 2011;hauhan et al., 2012). The maximum BTE obtained was 28.0% foriesel, followed by 27.4% for JB20 and 27.90% for CB20. The aver-ge values of BTE for diesel, JB20, JB20 BHA, JB20 BHT, CB20, CB20HA, and CB20 BHT were 23.82%, 23.20%, 23.38%, 23.36%, 23.51%,3.69%, and 23.65%, respectively. These changes were significant at

< 0.02. The decrease in BTE for JB20 and CB20 can be attributed toheir lower calorific values together with a higher fuel supply. CB20hows higher efficiency than JB20 owing to its lower calorific value.ddition of antioxidants to both JB20 and CB20 resulted in a slight

ncrease in their efficiencies. Higher power output together withower BSFC possibly contributed to the higher BTE of antioxidant-reated samples.

.3. Engine emission analysis

.3.1. NO emissionFig. 4 illustrates NO emission from the test diesel engine for

ifferent test fuels. NO is the most deleterious pollutant thathould be controlled at the combustion stage. The average valuesf NO emission for diesel, JB20, JB20 BHA, JB20 BHT, CB20, CB20HA, and CB20 BHT were 175.8, 185.8, 176.9, 178.5, 189.9, 180.4,nd 184.9 ppm, respectively. Thus, JB20 and CB20 produced meanncreases of 5.52% and 8.02%, respectively, in NO emission com-ared to diesel. These changes were found to be significant in theange 0.01 < p < 0.03. This increase can be attributed to the higherulk modulus of elasticity together with higher CNs. The higherulk modulus of a biodiesel leads to an early opening of the nozzlend advancement in the injection time compared to fossil diesel.

biodiesel is an oxygenated fuel and possesses a shorter ignitionelay due to higher CNs. The high oxygen content of a biodieselreates a high in-cylinder temperature under both premixed andiffusion combustion conditions (Adi et al., 2009; Kannan et al.,012). Thus, biodiesel blends are expected to combust earlier andence contribute to higher NO emission compared to diesel. Addi-ion of 2000 ppm BHA and BHT to JB20 showed significant average

O reductions of 4.8% and 3.9%, respectively, compared to JB20.n the other hand, for CB20, these values were 5.0% and 2.6%,

espectively. Phenolic hydroxyl groups present in BHA and BHTnterfere with the mechanism of prompt NO formation to various

Fig. 4. Variation of NO emission with engine speed for the test fuels.

extents. This result is also supported by a previously publishedwork (Hess et al., 2005). Thus, the NO reduction potential of antiox-idants depends on the feedstock used.

3.3.2. CO emissionCO is produced most readily from petroleum fuels because of the

absence of fuel-borne oxygen in their molecular structure (Gumuset al., 2012). It is formed during combustion, whenever charge isburned with an insufficient air supply with low flame tempera-ture. The variation of CO emission as a function of engine speedfor diesel, B20, and stabilized B20 is depicted in Fig. 5. The averagereductions in CO emission for JB20, JB20 BHA, JB20 BHT, CB20, CB20BHA, and CB20 BHT were 31.7%, 22.3%, 17.5%, 40.7%, 35.8%, and37.7%, respectively, compared to diesel. Thus, CB20 had the low-est CO emission compared to other test fuels due to the combinedeffects of its higher oxygen content and higher CN (Buyukkaya

Fig. 5. Variation of CO emission with engine speed for the test fuels.

I.M. Rizwanul Fattah et al. / Industrial Crop

coT(tapsawrio

3

fif(dbtfeliai2BcBf

4

Srt

Salley, S.O., 2010. 2009 quality survey of retail biodiesel blends in Michigan. Fuel

Fig. 6. Variation of HC emission with engine speed for the test fuels.

ombustion temperature, promoting more complete combustionf fuels (Kivevele et al., 2011a). JB20 also lead to lower CO emission.hese results are in agreement with previously reported trendsCecrle et al., 2012). The increase in CO emission for antioxidant-reated blends can be explained by the hindrance created by thentioxidants during conversion of CO to CO2. During oxidation,eroxyl and hydrogen peroxide (H2O2) radicals are formed succes-ively. These species further convert to hydroxyl radicals (OH) bybsorbing heat from the combustion chamber. Treating a biodieselith antioxidants reduces the concentration of peroxyl and H2O2

adicals, which affects the CO conversion process greatly. This effects more prominent in treated JB20s, as they possess less fuel-bornexygen than treated CB20s.

.3.3. HC emissionThe two major causes of HC emission from a diesel engine are as

ollows: (1) fuel mixed to leaner than the lean combustion limit dur-ng the delay period and (2) undermixing of fuels, which leave theuel injector nozzle late in the combustion process at a low velocityRizwanul Fattah et al., 2013). Fig. 6 illustrates the HC emission ofifferent test fuels at various speeds. The average reductions in HCy JB20 and CB20 were 40.1% and 49.6%, respectively, comparedo that in diesel. This result is expected, as CB20 possesses higheruel-borne oxygen than JB20. Addition of BHA and BHT reduces themission reduction benefits of JB20 and CB20 fuels. However, theevel of HC emission is still much lower than that of fossil diesel. Thencrease in HC emission for the stabilized biodiesel blends is due to

reduction in free radical formation by antioxidants, which signif-cantly reduces the oxidation of HC (Varatharajan and Cheralathan,013). The mean HC emission reductions for JB20 BHA and JB20HT are 18.9% and 16.1%, respectively, compared to diesel. On theontrary, the mean HC emission reductions for CB20 BHA and CB20HT are 23.2% and 34.8%, respectively, compared to diesel. Thus,

or both the cases addition of BHT produces lesser HC conversion.

. Conclusions

Coconut and Jatropha are two promising sources of a biodiesel.

ince a biodiesel and its blends are susceptible to oxidation, theyequire an antioxidant treatment. In this study, CBD was formulatedhrough one-step transesterification and JBD using the two-step

s and Products 57 (2014) 132–140 139

esterification–transesterification method. Based on the experimen-tal observations, the following conclusions can be made:

• Blending of 20% CBD and 20% JBD with diesel meets the ASTMspecification of blends (ASTM D7467).

• Addition of an antioxidant increases the kinematic viscosity, den-sity, flash point, as well as oxidation stability of CB20 and JB20 butreduces their calorific value. Thus, these blends are safe to storeand have higher oxidative stability.

• The effect of addition of an antioxidant on oxidation stabilitydepends on the feedstock. Thus, BHT shows better stabilizationfor JB20 than CB20.

• CB20 shows a very low pour point compared to others.• BSFC for JB20 and CB20 blends is higher by 5.02% and 4.76%,

respectively, than that for diesel, and addition of antioxidantsto these blends reduces BSFC by 0.55–0.79%, depending on thefeedstock.

• BTE for JB20 and CB20 blends is lower by 2.60% and 1.30%, respec-tively, than diesel, and addition of antioxidants to these blendsincreases BTE by 0.60–0.77%, depending on that feedstock.

• Both antioxidants have shown reductions in NO emission com-pared to base B20 blend.

• Addition of antioxidants to both blends increases the HC and COemissions compared to pure blends, primarily due to a reductionin the number of oxidative free radicals.

Acknowledgement

The authors would like to thank the University of Malaya forfinancial support through High Impact Research grant titled: CleanDiesel Technology for Military and Civilian Transport Vehicles hav-ing grant number UM.C/HIR/MOHE/ENG/07.

References

Adi, G., Hall, C., Snyder, D., Bunce, M., Satkoski, C., Kumar, S., Garimella, P., Stanton, D.,Shaver, G., 2009. Soy-biodiesel impact on NOx emissions and fuel economy fordiffusion-dominated combustion in a turbo-diesel engine incorporating exhaustgas recirculation and common rail fuel injection. Energy Fuels 23, 5821–5829.

Aliyu, B., Shitanda, D., Walker, S., Agnew, B., Masheiti, S., Atan, R., 2011. Performanceand exhaust emissions of a diesel engine fuelled with Croton megalocarpus(musine) methyl ester. Appl. Therm. Eng. 31, 36–41.

Atabani, A.E., Badruddin, I.A., Mahlia, T.M.I., Masjuki, H.H., Mofijur, M., Lee, K.T.,Chong, W.T., 2013a. Fuel properties of Croton megalocarpus, Calophyllum ino-phyllum, and Cocos nucifera (coconut) methyl esters and their performance in amulticylinder diesel engine. Energy Technol. 1, 685–694.

Atabani, A.E., Mahlia, T.M.I., Masjuki, H.H., Badruddin, I.A., Yussof, H.W., Chong, W.T.,Lee, K.T., 2013b. A comparative evaluation of physical and chemical propertiesof biodiesel synthesized from edible and non-edible oils and study on the effectof biodiesel blending. Energy 58, 296–304.

Banapurmath, N.R., Tewari, P.G., Hosmath, R.S., 2008. Performance and emissioncharacteristics of a DI compression ignition engine operated on Honge, Jatrophaand sesame oil methyl esters. Renew. Energy 33, 1982–1988.

Berman, P., Nizri, S., Wiesman, Z., 2011. Castor oil biodiesel and its blends as alter-native fuel. Biomass Bioenergy 35, 2861–2866.

Boudy, F., Seers, P., 2009. Impact of physical properties of biodiesel on the injectionprocess in a common-rail direct injection system. Energy Convers. Manage. 50,2905–2912.

Buyukkaya, E., Benli, S., Karaaslan, S., Guru, M., 2013. Effects of trout-oil methyl esteron a diesel engine performance and emission characteristics. Energy Convers.Manage. 69, 41–48.

Cecrle, E., Depcik, C., Duncan, A., Guo, J., Mangus, M., Peltier, E., Stagg-Williams,S., Zhong, Y., 2012. Investigation of the effects of biodiesel feedstock on theperformance and emissions of a single-cylinder diesel engine. Energy Fuels 26,2331–2341.

Chauhan, B.S., Kumar, N., Cho, H.M., 2012. A study on the performance and emissionof a diesel engine fueled with Jatropha biodiesel oil and its blends. Energy 37,616–622.

de Guzman, R.C., Tang, H., Wadumesthrige, S., Zhou, T., Garcia-Perez, M.D., Ng, K.Y.S.,

89, 3662–3667.Fernandes, D.M., Montes, R.H.O., Almeida, E.S., Nascimento, A.N., Oliveira, P.V.,

Richter, E.M., Munoz, R.A.A., 2013. Storage stability and corrosive character ofstabilised biodiesel exposed to carbon and galvanised steels. Fuel 107, 609–614.

1 al Crop

G

G

G

H

H

H

H

H

I

I

J

J

K

K

K

K

K

K

K

L

L

L

M

a Jatropha biodiesel fuelled DI diesel engine using antioxidant additives. Fuel90, 2721–2725.

40 I.M. Rizwanul Fattah et al. / Industri

umus, M., Kasifoglu, S., 2010. Performance and emission evaluation of a compres-sion ignition engine using a biodiesel (apricot seed kernel oil methyl ester) andits blends with diesel fuel. Biomass Bioenergy 34, 134–139.

umus, M., Sayin, C., Canakci, M., 2012. The impact of fuel injection pressure on theexhaust emissions of a direct injection diesel engine fueled with biodiesel–dieselfuel blends. Fuel 95, 486–494.

ürü, M., Koca, A., Can, Ö., C ınar, C., S ahin, F., 2010. Biodiesel production from wastechicken fat based sources and evaluation with Mg based additive in a dieselengine. Renew. Energy 35, 637–643.

asimoglu, C., Ciniviz, M., Özsert, I., Ic ingür, Y., Parlak, A., Sahir Salman, M., 2008.Performance characteristics of a low heat rejection diesel engine operating withbiodiesel. Renew. Energy 33, 1709–1715.

azar, H., Aydin, H., 2010. Performance and emission evaluation of a CI engine fueledwith preheated raw rapeseed oil (RRO)–diesel blends. Appl. Energy 87, 786–790.

ess, M.A., Haas, M.J., Foglia, T.A., Marmer, W.N., 2005. Effect of antioxidant additionon NOx emissions from biodiesel. Energy Fuels 19, 1749–1754.

oekman, S.K., Broch, A., Robbins, C., Ceniceros, E., Natarajan, M., 2012. Review ofbiodiesel composition, properties, and specifications. Renew. Sustain. EnergyRev. 16, 143–169.

oekman, S.K., Robbins, C., 2012. Review of the effects of biodiesel on NOx emissions.Fuel Process. Technol. 96, 237–249.

˙ leri, E., Koc ar, G., 2013. Effects of antioxidant additives on engine performance andexhaust emissions of a diesel engine fueled with canola oil methyl ester–dieselblend. Energy Convers. Manage. 76, 145–154.

˙ leri, E., Koc ar, G., 2014. Experimental investigation of the effect of antioxidant addi-tives on NOx emissions of a diesel engine using biodiesel. Fuel 125, 44–49.

iang, J.-J., Tan, C.-S., 2012. Biodiesel production from coconut oil in supercriticalmethanol in the presence of cosolvent. J. Taiwan Instit. Chem. Eng. 43, 102–107.

indal, S., Nandwana, B.P., Rathore, N.S., 2010. Comparative evaluation of combus-tion, performance, and emissions of Jatropha methyl ester and karanj methylester in a direct injection diesel engine. Energy Fuels 24, 1565–1572.

alam, M.A., Masjuki, H.H., Jayed, M.H., Liaquat, A.M., 2011. Emission and perfor-mance characteristics of an indirect ignition diesel engine fuelled with wastecooking oil. Energy 36, 397–402.

annan, D., Pachamuthu, S., Nurun Nabi, M., Hustad, J.E., Løvås, T., 2012. Theoreticaland experimental investigation of diesel engine performance, combustion andemissions analysis fuelled with the blends of ethanol, diesel and Jatropha methylester. Energy Convers. Manage. 53, 322–331.

arabektas, M., Ergen, G., Hosoz, M., 2008. The effects of preheated cottonseed oilmethyl ester on the performance and exhaust emissions of a diesel engine. Appl.Therm. Eng. 28, 2136–2143.

ivevele, T.T., Kristóf, L., Bereczky, Á., Mbarawa, M.M., 2011a. Engine performance,exhaust emissions and combustion characteristics of a CI engine fuelled withcroton megalocarpus methyl ester with antioxidant. Fuel 90, 2782–2789.

ivevele, T.T., Mbarawa, M.M., Bereczky, A., Laza, T., Madarasz, J., 2011b. Impactof antioxidant additives on the oxidation stability of biodiesel produced fromCroton megalocarpus oil. Fuel Process. Technol. 92, 1244–1248.

oh, M.Y., Mohd. Ghazi, T.I., 2011. A review of biodiesel production from Jatrophacurcas L. oil. Renew. Sustain. Energy Rev. 15, 2240–2251.

umar, N., Varun, Chauhan, S.R., 2013. Performance and emission characteristicsof biodiesel from different origins: a review. Renew. Sustain. Energy Rev. 21,633–658.

apuerta, M., Armas, O., Rodríguez-Fernández, J., 2008. Effect of biodiesel fuels ondiesel engine emissions. Prog. Energy Combus. Sci. 34, 198–223.

iaquat, A.M., Masjuki, H.H., Kalam, M.A., Fattah, I.M.R., Hazrat, M.A., Varman,M., Mofijur, M., Shahabuddin, M., 2013. Effect of coconut biodiesel blendedfuels on engine performance and emission characteristics. Procedia Eng. 56,583–590.

oh, S.-K., Chew, S.-M., Choo, Y.-M., 2006. Oxidative stability and storage behavior

of fatty acid methyl esters derived from used palm oil. J. Am. Oil Chem. Soc. 83,947–952.

ofijur, M., Masjuki, H.H., Kalam, M.A., Atabani, A.E., 2013. Evaluation of biodieselblending, engine performance and emissions characteristics of Jatropha curcasmethyl ester: Malaysian perspective. Energy 55, 879–887.

s and Products 57 (2014) 132–140

Mofijur, M., Masjuki, H.H., Kalam, M.A., Hazrat, M.A., Liaquat, A.M., Shahabuddin,M., Varman, M., 2012. Prospects of biodiesel from Jatropha in Malaysia. Renew.Sustain. Energy Rev. 16, 5007–5020.

Mohibbe Azam, M., Waris, A., Nahar, N.M., 2005. Prospects and potential of fattyacid methyl esters of some non-traditional seed oils for use as biodiesel in India.Biomass Bioenergy 29, 293–302.

Niki, E., 1987. Antioxidants in relation to lipid peroxidation. Chem. Phys. Lipids 44,227–253.

Ong, H.C., Silitonga, A.S., Masjuki, H.H., Mahlia, T.M.I., Chong, W.T., Boosroh, M.H.,2013. Production and comparative fuel properties of biodiesel from non-edibleoils: Jatropha curcas, Sterculia foetida and Ceiba pentandra. Energy Convers. Man-age. 73, 245–255.

Özcanlı, M., Keskin, A., Aydın, K., 2011. Biodiesel production from terebinth (Pistaciaterebinthus) oil and its usage in diesel engine. Int. J. Green Energy 8, 518–528.

Ozsezen, A.N., Canakci, M., Sayin, C., 2008. Effects of biodiesel from used frying palmoil on the performance, injection, and combustion characteristics of an indirectinjection diesel engine. Energy Fuels 22, 1297–1305.

Palash, S.M., Kalam, M.A., Masjuki, H.H., Arbab, M.I., Masum, B.M., Sanjid, A., 2014.Impacts of NOx reducing antioxidant additive on performance and emissionsof a multi-cylinder diesel engine fueled with Jatropha biodiesel blends. EnergyConvers. Manage. 77, 577–585.

Puhan, S., Nagarajan, G., Vedaraman, N., Ramabramhmam, B., 2007. Mahua oil (Mad-huca indica oil) derivatives as a renewable fuel for diesel engine systems in India:a performance and emissions comparative study. Int. J. Green Energy 4, 89–104.

Pullen, J., Saeed, K., 2012. An overview of biodiesel oxidation stability. Renew. Sus-tain. Energy Rev. 16, 5924–5950.

Qi, D.H., Chen, H., Geng, L.M., Bian, Y.Z., 2010. Experimental studies on the com-bustion characteristics and performance of a direct injection engine fueled withbiodiesel/diesel blends. Energy Convers. Manage. 51, 2985–2992.

Ramadhas, A.S., Jayaraj, S., Muraleedharan, C., 2005. Biodiesel production from highFFA rubber seed oil. Fuel 84, 335–340.

Ramos, M.J., Fernández, C.M., Casas, A., Rodríguez, L., Pérez, Á., 2009. Influence of fattyacid composition of raw materials on biodiesel properties. Bioresour. Technol.100, 261–268.

Rizwanul Fattah, I.M., Masjuki, H.H., Kalam, M.A., Hazrat, M.A., Masum, B.M., Imte-nan, S., Ashraful, A.M., 2014a. Effect of antioxidants on oxidation stability ofbiodiesel derived from vegetable and animal based feedstocks. Renew. Sustain.Energy Rev. 30, 356–370.

Rizwanul Fattah, I.M., Masjuki, H.H., Kalam, M.A., Mofijur, M., Abedin, M.J., 2014b.Effect of antioxidant on the performance and emission characteristics of a dieselengine fueled with palm biodiesel blends. Energy Convers. Manage. 79, 265–272.

Rizwanul Fattah, I.M., Masjuki, H.H., Liaquat, A.M., Ramli, R., Kalam, M.A., Riazuddin,V.N., 2013. Impact of various biodiesel fuels obtained from edible and non-edibleoils on engine exhaust gas and noise emissions. Renew. Sustain. Energy Rev. 18,552–567.

Ryu, K., 2010. The characteristics of performance and exhaust emissions of a dieselengine using a biodiesel with antioxidants. Bioresour. Technol. 101, S78–S82.

Sarin, R., Sharma, M., Sinharay, S., Malhotra, R.K., 2007. Jatropha–palm biodieselblends: an optimum mix for Asia. Fuel 86, 1365–1371.

Sayin, C., 2010. Engine performance and exhaust gas emissions of methanol andethanol–diesel blends. Fuel 89, 3410–3415.

Shahidi, F., Janitha, P., Wanasundara, P., 1992. Phenolic antioxidants. Crit. Rev. FoodSci. Nutr. 32, 67–103.

Varatharajan, K., Cheralathan, M., 2013. Effect of aromatic amine antioxidants onNOx emissions from a soybean biodiesel powered DI diesel engine. Fuel Process.Technol. 106, 526–532.

Varatharajan, K., Cheralathan, M., Velraj, R., 2011. Mitigation of NOx emissions from

Zuleta, E.C., Baena, L., Rios, L.A., Calderón, J.A., 2012. The oxidative stability ofbiodiesel and its impact on the deterioration of metallic and polymeric materi-als: a review. J. Braz. Chem. Soc. 23, 2159–2175.