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Biodiesel production via alkali-catalyzed transesterication of Malaysian RBDpalm oil Characterization, kinetics model

Mohammad Reza Shahbazi a , Behnam Khoshandam a ,*, Masoud Nasiri a , Majeed Ghazvini ba Oil, Gas and Chemical Engineering Department, Semnan University Opposite Sukan Park, Semnan 35195363, Iranb Engineering Department, Shahroud Islamic Azad University End of Tehran Ave, Shahrood, Iran

1. Introduction

Nowadays increasing in application of fossil fuels in differentelds caused increasing concern about using these fuels and whathappens after use or the global warming issues. In addition,depletion of this great source of energy causes looking foralternative and efcient fuels by many researchers. Indeedremoving disadvantages of conventional diesel fuel is anotherrelative subject. One of these alternative fuels is biodiesel, whichwith respect to its benets such as non-toxicity, biodegradability,and renewability has attracted many views. In addition to thesebenets, greenhouse gas reduction and less pollution generation of this type of fuel compared with other fuels are other major reasonsto use the biodiesel [13] . A life cycle analysis of the biodieselshowed that the overall CO2 emissions were reduced by 78%compared with the petroleum based diesel fuel [3,4] .

Biodiesel or fatty acid methyl ester (FAME) is produced by thetransesterication reaction among vegetable oils, animal fats orwaste cooking oils with an alcohol in presence of a catalyst. Astrong alkali, a strong acid, and an enzyme are three kinds of catalysts which can be used in the transesterication reaction. The

main advantages of using a strong alkali as a catalyst are shorterreaction time and less amount of catalyst required in themanufacturing process of the transesterication reaction. There-fore a strong alkaline catalyst is widely used in the industry formass biodiesel production [3] .

Many studies have been carried out to investigate the effects of different parameters involved in the reaction, such as usingdifferent oils and alcohols, alcohol to oil molar ratio, types andamount of catalysts, reaction time or temperature [410] . In manyresearches also the feasibility and effect of new processes, such ascarrying out the reaction under the microwave irradiation,supercritical conditions and using ultrasonic mixing, have beenestablished [3,1113] . Although nowadays the reaction under theconventional heating in presence of alkaline catalysts is the mostcommon way to prepare biodiesel, all mentioned studies havebeen established on accelerating the chemical reaction and nallyobtaining the higher reaction yields within a short time. Reportinga conversion of 98.4% for the safower oil to methyl ester at 6 minassisted by microwave irradiation was shown that the processunder the microwave irradiation can be much faster than thatunder the conventional heating [3] . Many studies have alsofocused on the kinetics of transesterication reaction of differentfeedstocks to nd the optimum conditions and determine theFAME compositions [1418] .

One of the most important issues on production of biodiesel isits higher price compared with other fuels. The production cost isaffected by different factors. There is no doubt that the oil price is

Journal of the Taiwan Institute of Chemical Engineers 43 (2012) 504510

A R T I C L E I N F O

Article history:Received 4 October 2011Received in revised form 15 January 2012Accepted 25 January 2012Available online 18 February 2012

Keywords:BiodieselTransestericationMethyl esterRBD palm oilCatalysts

A B S T R A C T

Biodiesel as an alternative fuel wasproduced by transestericationof Malaysian RBD(Rened, Bleached,and Deodorized) palmoil withalkalinecatalysts. Potassium andsodium hydroxidewere usedas catalystsin this reaction at temperature of 60 8 C in a stirred tank reactor with 600 rpm stirring. Gaschromatography was used to determine the fatty acid methyl ester (FAME) contents in the producedbiodiesel . Yield of reaction which was carried out with KOH as a catalyst is a higher value than thereaction when NaOH wasused as a catalyst.A second-order reaction mechanism which waspurposed byLeevijit et al. (2004) was applied to calculate the product concentrations. There was a good agreementbetween the methyl ester concentrations measured experimentally and what was predicted from thekinetic model. Finally importantfuel propertiesof produced biodieselswere obtained andcomparedwithpetro diesel and the ASTM standards which indicate that the biodiesel with acceptable quality wassynthesized experimentally.Crown Copyright 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights

reserved.

* Corresponding author. Tel.: +98 9125466376; fax: +98 2313354120.E-mail addresses: [email protected] (M.R. Shahbazi),

[email protected] (B. Khoshandam), [email protected] (M. Nasiri),[email protected] (M. Ghazvini).

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Journal of the Taiwan Institute of Chemical Engineers

j o u r n al h o m ep a ge : w ww.e l sev i e r . co m/ l o c a t e / j t i ce

1876-1070/$ see front matter . Crown Copyright 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

doi: 10.1016/j.jtice.2012.01.009
http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://www.sciencedirect.com/science/journal/18761070http://www.sciencedirect.com/science/journal/18761070http://www.sciencedirect.com/science/journal/18761070http://dx.doi.org/10.1016/j.jtice.2012.01.009http://dx.doi.org/10.1016/j.jtice.2012.01.009http://www.sciencedirect.com/science/journal/18761070mailto:[email protected]:[email protected]:[email protected]:[email protected]://dx.doi.org/10.1016/j.jtice.2012.01.009


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the main factor in production cost reduction [19] . Generally, all of vegetable oils and animal fats can be used to produce biodiesel. Themost common ones are palm, sunower, rapeseed, and soybean oil.In some researches tallow and waste cooking oil also have beenused [20,21] . The amount of harvested crops and world supply of palm, soybean, and rapeseed are shown in Table 1 [11] .

As it is seen the palm oil can be the best choice compared withothers due to its higher efciency and production rate with averageyields of 3.55.0 10 3 kg/ha/year.

Despite of having lower price, raw palm oil has some limitationsfor transesterication reaction. The signicant limitation is high freefatty acid (FFA) of oil which makes force to use particular catalysts. Incase of using alkaline catalyst which is the most common catalyst for

transesterication, the glycerol and alcohol must be anhydrous withminimum FFA, because water and FFA make the reaction partiallychange to saponication which produces soap. The soap lowers theyield of ester, renders separation of ester from glycerol, and makesthe water washing stage very difcult [1,10,22] . Therefore it leads tohigher washing and purifying expenses. To eliminate the undesir-able effects of humidity and free fatty acids, it was recommendedthat the amount of them in oil be kept below 0.5 wt% and 0.05 wt%,respectively [10] .

Raw palm oil also contains some useful components, such asvitamin E, free fatty acids, cartonoides, phosphatides, and plantsterols (almost 1%), which will be removed during rening process,bleaching and deodorizing and can be reused. Also remaining palmoil is more convenient than raw oil to produce biodiesel [11] .

Generally,

regarding

with

highly

produced

palm

oil

in

the

worldand different fatty acid compositions of oils depending ongeographical locations and environmental conditions, workingon palm oil transesterication reaction is considered logically.

Depletion of fossil fuels, increasing the request to energy in theworld and low capacity of petroleum reneries in Iran beside airpollution in big cities made it necessary to nd a renewable sourceof energy like biodiesel. It would be difcult or even impossible toprovide sufcient need for oil seeds from the domestic agriculturallands because of food production and nourishment value of ediblecrops in a populated country like Iran. Palm oil produced inMalaysia in Middle East can be a good source for biodiesel.Malaysia is one of the biggest exporters of palm oil in such case thatits price in Iran can compete with other oils produced from

domestic

cultivated

crops.

In this work, biodiesel is produced by transesterication of Malaysian RBD (Rened, Bleached, and Deodorized) palm oil withmethanol in presence of sodium and potassium hydroxide ascatalysts. Mass concentration of methyl ester and production yieldare investigated and checked with reaction kinetics prediction andother previous works. The properties of biodiesel produced aremeasured and compared with the ASTM standards for biodieseland the conventional diesel fuels.

2. Experimental

2.1. Materials

The used rened palm oil was purchased from ERAPOLY SDNBHD, Malaysia. To produce RBD palm oil, further stages consist of bleaching and deodorizing were done in Margarin Mfg. Co. in Iran.In these complementary stages, remained impurities that caninterfere the reaction as mentioned before, will be decreasedsignicantly [22] . In this work the initial composition of palm oilconsisted of 96.3% triglyceride, 3.2% diglyceride, and 0.5%monoglyceride. Gas chromatographic analysis of palm oil alsorevealed that palmetic (42.56%), oleic (40.08%), linoleic (10.69%),and stearic (4.76%) acids are the major fatty acids which altogethercomprised about 98% of the total fatty acids. Acidity number andhumidity which could have negative effects on the yield of reactionwere decreased to 0.1 mg KOH/g oil and 0.03 wt%, respectively,after passing from the rening stages. Methanol, sodium hydrox-ide, potassium hydroxide, and hydrochloric acid were prepared inanalytical grade from the Merck Co. Also n-hexane as the solvent,methyl myristate as the internal standard, methyl palmitate,methyl stearate, and other reference standards in more than 99%purity were taken from the Sigma Chemical Co.

2.2. Instruments

The transesterication reaction was carried out in a 1-L two-necked ask reactor equipped with a condenser similar to set up

used in F. Mas work [23] . The reactor was heated up on a hot platethat kept at temperature of 60 0.5 8 C along the experiments. Amagnetic stirrer with a constant speed (600 rpm) provided the mixingrequirements.

2.3. Method

Biodiesel derived from the RBD palm oil was prepared byreacting 500 g of oil with 113.2 g CH3 OH (6:1 molar ratio) and 5 gcatalyst (1 wt%). Oil was heated up to 60 8 C (510 8 C less than themethanol boiling point) and kept on this temperature in thereactor. Required amount of catalyst was dissolved completely in aknown amount of methanol in a separate container and was addedto the reactor while stirring with agitation speed of 600 rpm. The

reaction

was

carried

out

for

60

min

under

the

reux

at

60

8

C.

Theoptimum conditions of the reaction were set as those reported inthe literatures [16,24,25] .

The reactor was equipped with reux condenser to condenseback the methanol escaping from the reaction mixture. Afterpassing 60 min, the reaction reaches to the equilibrium conditionand the mixture was neutralized (pH of about 7.0) withhydrochloric acid. Then the mixture was cooled immediately tothe room temperature by putting the reactor in the ice bath atabout 5 8 C. In the separation section of the experiment, the solutionwas poured into a decanter and was then held at least for 12 h toproduce two phases: ester phase and glycerol phase. The phaseseparation can be observed within the rst 10 min of settling.During this time, the ester layer was opaque and shows an

incomplete

separation.

The

opaque

ester

layer

replaced

by

a

Nomenclature

A peak area As peak area of standard solutionC s concentration of standard solutionCN cetane numberDG diglyceride

FID

ame

ionization

detectorGC gas chromatographyGL glycerink reaction rate constant of Eqs. (2)(4) (L/mol s)m i weight of component iME methyl esterMG monoglycerideMW molecular weightROH alcoholRBD Rened, Bleached, DeodorizedTG triglyceridewt% weight percentY ester biodiesel content (%)

M.R. Shahbazi et al. / Journal of the Taiwan Institute of Chemical Engineers 43 (2012) 504510 505


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transparent one if more times have been given for settling. Usually,the complete separation could take as long as 818 h. The methylester which was the upper layer in the decanter was washed threetimes with the warm distilled water to remove excess methanol,catalyst, and remained glycerol. In the washing stage, water tomethyl ester ratio was considered to be 2:1.Washed biodiesel wasdried using heating up approximately to 110 8 C in an opencontainer until making sure that no more steam rises from it.Indeed the heating process can also drive off any traces of moistureand remained methanol [24] . Finally the mixture was ltrated andcooled down to the room temperature and the pure biodiesel wasstored for any further tests.

2.4. Analysis

The gas chromatography analyzer (Shimadzu 2010 Brand)equipped with a ame ionization detector (FID) and a capillarycolumn (SP 2330 polar column 2 60 m ID: 0.32 mm; SupelcoInc.) was used for analyzing the produced biodiesel. Helium wasused as an inert carrier gas at a ow rate of 1 ml/min. Oventemperature started at 160 8 C, kept for 5 min, and then it increasedto 210 8 C at a rate of 2 8 C/min and held at this temperature for10 min. Methyl myristate and n-hexane were used as internalstandard and solvent, respectively [26] .

The FAME content (mass concentration) in the product wasmeasured by the GC analysis according to the EN 14103 testmethod [27] . In this test method the methyl heptadecanoate and n-heptane were replaced with methyl myristate and n-hexane as

internal standard and solvent, respectively. To measure thebiodiesel content in the nal product, a standard solution wasprepared as 10 mg/ml methyl myristate with hexane solution atrst. Then 250 mg of the sample was added to 5 ml of standardsolution and the mixture was injected to the GC column.

Different standard tests were applied to measure some of theimportant physical properties of the produced biodiesel. The ENISO 3675 [28] for density measurement, ASTM D445 [29] forkinematic viscosity measurement, ASTM D93 [30] for ash pointmeasurement, EN ISO 660 [31] for acidity number measurement,and ASTM 2709 [32] for humidity measurement were applied. Thecetane number was also calculated from the correlation (1) givenin [33] .

CN

33 :6

0:539 C18 :

0

0:303 C18 :

1

0:0878 C18:

2 0:233 C22 : 1 (1)

where CN indicates the cetane number and (C18:0), (C18:1),(C18:2), (C22:1) are mass concentration of stearic, oleic, linoleic,and erucic acids, respectively.

3. Product predictions using the reaction kinetics

The kinetics mechanism of the transesterication reaction canbe presented as a three stepwise reversible reactions. Twointermediates of diglyceride (DG) and monoglyceride (MG) andone mole of methyl ester (ME) in each step are produced. Indeedone mole of glycerin (GL) in the third stage is produced. The three

stepwise

reversible

reactions

are

as

follows

[15,16] :

TG ROH @k1

k2DG ME (2)

DG ROH @k3

k4MG ME (3)

MG ROH @k5

k6GL ME (4)

where ROH shows one mole of alcohol consumed in the reactions.Based on the kinetic studies of transesterication reaction, it

was supposed that the production of methyl ester is just via theabove mechanism and there is no direct conversion of reactant tothe nal product. Therefore, the general form of the governing setof second-order rate equations, characterizing the above reactionsfor transesterication of palm oil, without shunt reaction, iswritten as follows:

dTGd t

k1 TG ROH k2 DG ME (5)

dDGdt

k1 TG ROH k2 DG ME k3 DG ROH

k4 MG ME

(6)

dMGd t

k3 DG ROH k4 MG ME k5 MG ROH

k6 GL ME (7)

dGL d t

k5 MG ROH k6 GL ME (8)

dMEd t

k1 TG ROH k2 DG ME k3 DG ROH

k4 MG ME k5 MG ROH k6 GL ME (9)

dROHd t

dMEd t (10)

where k1 to k6 are the reaction rate constants and the bracketdenotes the concentration.

To evaluate our work, the molar concentration of methyl esterat the end of the reaction was compared with what was predictedfrom the kinetic model. The system of ordinary differentialequations has been solved using MATLAB software based on theODE45 command.

To calculate the weight of one mole of RBD palm oil, averagemolecular weight of oil has been determined using the fatty acidcompositions by the following equation [19] :

MW ester 3X% m i MW i 38 (11)where

MW i and

m i are

the

oil

molecular

weight

and

the

percentageof fatty acid i in the raw material, respectively. The constant valueof 38 is the summation of atomic weights of carbon and hydrogenatoms in the triglyceride structure (C3 H2 ) without consideringthree fatty acids (RCOOH).

Using the known values of methanol to oil molar ratio and theirmolecular weights, the initial molar concentrations of methanoland oil were calculated as 4.9614 mol/L and 0.8269 mol/L,respectively. Therefore by using triglyceride, diglyceride, andmonoglyceride concentrations which mentioned in Section 2.1 , theinitial molar concentrations of them were obtained as 0.7963047,0.0264608, and 0.0041345 mol/L, respectively. Methyl ester andglycerin concentrations at the beginning of reaction also wereconsidered to be zero. The reaction rate constants are presented in

Table

2

[15] .

Table 1Products from the harvested crops and world supply of vegetable oils [11] .

Palm Soybean Rapeseed

2003/04 world supply of oil (10 9 kg/yr) 29.7 29.85 14.22005/06 world supply of oil (10 9 kg/yr) 34.8 33.87 16.59Crops harvested (10 3 kg/ha) 19.1 2.3 3Oil produced (10 3 kg/ha) 4.8 0.4 1.2

M.R. Shahbazi et al. / Journal of the Taiwan Institute of Chemical Engineers 43 (2012) 504510506


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Fig. 1 shows the typical concentration prole for eachcomponent in transesterication of palm oil at 60 8 C as a functionof time. This gure shows the rate of consumption of triglycerideand formation of methyl ester and glycerin as well as theintermediate compounds. The rate of consumption of alcoholand its extra value also have been shown. The results revealed thatthe production rate of methyl ester at the beginning of reaction is

fast in such manner that the molar concentration of methyl esterreaches to an equilibrium constant value of 2.41 mol/L at about22 min.

4. Results and discussions

The FAME content (Y ester ) was determined based on the GCresults as follows [34] :

Y ester % 100 P A As As

C sV sm

(12)

where P A is the summation of the GC peak areas for all methylesters (C14:0C24:1), As is the increasing amount of the GC peakarea

of

methyl

myristate

after

adding

standard

solution,

C s is

theconcentration of standard solution as 10 mg/ml, V s is the volume of standard solution (5 ml), and m is the amount of sample (250 mg).Based on this relation, methyl ester contents in the nal biodieselswere calculated as 88 and 93 wt% for cases when NaOH and KOHused as catalyst, respectively. This value obtained as 9798% forKaranja oil (a non-edible oil) transesterication with methanol andKOH as a catalyst under the optimized conditions [35] .

Fig. 2(a)(c) shows the chromatograms of fatty acid of feedstockand produced biodiesel by transesterication of palm oil usingpotassium hydroxide and sodium hydroxide as catalyst mixedwith the standard solution. The results of analysis have been givenin Table 3.

As it is given in Table 3, according to the gas chromatographic

analysis

there

are

no

signicant

changes

in

the

concentration

of

fatty acid methyl esters after 60 min of reaction. Therefore itindicates that the amount of different fatty acids did not changeduring the transesterication reaction, and just fatty acids convertto methyl esters.

The molar concentration of methyl ester per unit volume of solution was measured using the biodiesel content in the nalproduct and molecular weight of the esters. Also the averagemolecular weight of methyl esters is calculated from the followingequation [19] :

MW ester XMW i % m i 14 (13)where MW i and %m i are the molecular weight and the weightpercent of fatty acid i obtained from the GC analysis, respectively,and constant value of 14 is the molecular weight of CH2 in themethyl ester molecular structure without considering the fattyacid.

The methyl ester concentrations in two cases of using NaOH andKOH as catalyst were measured experimentally as 2.31 mol/L and2.43 mol/L, respectively, after 60 min. There is a good agreementbetween the experimental results and what was predicted fromthe kinetic model when using the rate constants of Table 2.Therefore a second-order kinetic mechanism using the mentioned

reaction

rate

constants

can

justify

the

palm

oil

transestericationreaction, properly. Mathematical models that used for kineticstudies can be applied to predict the product concentrations,design the experiments, and optimize the biodiesel productionprocesses. The kinetics of palm transesterication reaction studiedby different researchers and the second-order kinetics presentedfor this reaction [15,16] . The second-order kinetics proposed ontransesterication reaction of soybean, sunower, brassica car-inata oils as well [14,3638] . In some studies the mass transfercontrolling step on the rate of transesterication reaction wasinvestigated and the sigmoidal kinetics shape was analyzed[39,40] . The kinetics of transesterication reaction of triglycerideswith methanol was compared with interesterication reactionwith methyl acetate in a recent work [41] . In this study 15

reactions

including

the

transesterication

reactions

with

second-order kinetics scheme were considered.At last the biodiesel conversion can be calculated as [42]

conversion % m B=MW BY ester

m O=3MW O (14)

where Y ester is the biodiesel content, m is the weight, MW is themolecular weight, and subscripts O and B show the oil andbiodiesel, respectively.

The conversion of RBD palm oil to biodiesel at mentionedoptimum conditions was calculated as 81% and 90% for two typesof produced biodiesels using NaOH and KOH as catalyst,respectively. The biodiesel produced using potassium hydroxideas a catalyst shows that the higher conversion of palm oil

transesterication

as

is

in

good

agreement

with

what

was

reportedby Meher et al. [25] on higher transesterication conversion of soybean oil with potassium hydroxide as a catalyst. Rashid andAnwar [5] reported the yield of 9596% in a process of transesterication of rapeseed oil after the reaction time of 120 min and at temperature of 65 8 C with other conditions same asthe present work. Comparing different catalysts, they alsoconcluded that the potassium hydroxide was the best catalyst.Indeed Darnoko and Cheryan [16] reported 87 wt% and 90 wt% forpalm oil methyl ester concentrations in 50 8 C and 65 8 C in thepresence of KOH as the catalyst, respectively, which arecomparable with the results obtained in the present work. As itis seen the results agree well with those achieved by the otherresearchers. The biodiesel yield was reported as 97% for virgin oils

of

sunower

and

soybean

[43] , 92%

and

89.8%

for

waste

frying

and

Table 2The reaction rate constants (L/mol s) [15] .

k1 1.057 10 2

k2 0.000k3 1.184 10 1

k4 8.187 10 2

k5 1.310 10 1

k6 2.011 10 3

Fig. 1. The concentration proles of methyl ester (ME), methanol (MeOH), glycerol(GL), triglyceride (TG), diglyceride (DG), and monoglyceride (MG) during thetransesterication of palm oil at temperature of 60 8 C, methanol/oil molar ratio of 6:1, catalyst concentration of 1 wt% oil and mixing speed of 600 rpm.



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cooking oil [43,44] when alkali catalyst used in the course of thetransesterication reaction.

The quality of synthesized alkyl esters was evaluated bymeasuring some important fuel properties and comparing with theASTM standards for biodiesel and the properties of conventionaldiesel fuel. The quality of biodiesel is signicant from the enginepoint of view. Different factors have been specied to check the

quality.

The

results

have

been

given

in

Table

4.

As the major characteristic of the fuels, the kinematic viscosityof the produced biodiesels was measured and reported in Table 4based on the method presented in the ASTM standard D445 [29] .As it is reported, the values are in an acceptable range of 1.96 mm 2 /s. High viscosity leads to the poor atomization of the fuel,incomplete combustion, choking of fuel injectors, ring carboniza-tion, and accumulation of fuel in the lubricating uid. The ASTM

D93

[30]

was

applied

for

the

ash

point

calculation.

The

ash

pointis a very important parameter to consider in the handling, storageand safety of fuels and ammable materials. The higher values inash point mean the risks of re to be decreased. The acid numberof produced biodiesels was measured as acceptable values incomparison with the maximum acid value of 0.5 mg KOH/greported in the ASTM D6751 [46] on biodiesel standards. Anotherimportant qualied parameters for biodiesels are water and thesediment content. Water in the biodiesel can promote themicrobial growth and leads to the corrosion and formation of emulsions and also causes the fuel hydrolysis and oxidation. Theresults of testing the humidity in the present work were obtainedbased on the ASTM D6751 [46] . The ASTM D976 was applied to thecalculation of the cetane index for biodiesel produced in the

presence

of

KOH

as

catalyst.

The

cetane

index

was

measured

as

Fig. 2. The GC chromatograms of (a) RBD palm oil, (b) biodiesel, using NaOH as a catalyst mixed with the standard solution, (c) biodiesel, using KOH as a catalyst mixed withthe standard solution.

Table 3Fatty acid compositions in RBD palm oil and produced biodiesel in presence of NaOH and KOH as a catalyst.

FAME RBD palm oil After using NaOH After using KOH

Myristic (C14:0) * 1.06 1.14 1.0Palmitic (C16:0) 42.56 42.04 42.54Palmitoleic (C16:1) 0.21 0.14 0.16Stearic (C18:0) 4.76 4.43 4.39Oleic (C18:1) 40.08 39.97 39.83Linoleic (C18:2) 10.69 11.74 11.60Linolenic (C18:3) 0.53 0.44 0.39Arachidic (C20:0) 0.11 0.09 0.08* Numbers in parenthesis indicate the numbers of carbons and unsaturated

bonds.



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49.5 that is very close to what was calculated from the correlation(1) . The minimum value of cetane number based on the ASTMD6751 [46] is 47, that fullled the values obtained in the presentwork. Therefore the properties of produced biodiesel in the presentwork were found within the limits of standards.

5. Conclusions

The Malaysian palm oil as a good source of FAME was used toproduce biodiesel in the present work. Sodium and potassiumhydroxides were used as catalysts in the transestericationreaction. The potassium hydroxide was a better catalyst to reachto the higher yields on the transesterication of palm oil. Indeedthe conversion of Malaysian palm oil to the produced biodieselshows higher value than that reported by the other researchesregarding to the operating temperature. The molar concentrationof fatty acid methyl esters (FAME) was compared with what waspredicted from a second-order kinetics model that it justied theresults of the present work at the time duration of 60 min.

The kinematic viscosity, ash point, and the cetane number of the produced biodiesel were measured and showed as acceptablevalues based on the ASTM standards. The biodiesel properties alsowere compared with the conventional diesel fuel properties and itshows that the synthesized biodiesel has the properties compara-ble with the conventional diesel fuel and can be considered as analternative to mix with it and use in motors.

Acknowledgments

We would like to appreciate the research laboratory operatorsof Margarin Mfg. Co. for the gas chromatography analyses. Indeedmany thanks to the personnel of research laboratory of TarbiatModarres University for measuring the ash point and thekinematic viscosity of the produced biodiesel.

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[30]

ASTM

2003-D93:

Standard

test

methods

for

ash-point

by

PenskyMartensclosed cup tester, Annual Book of ASTM Standards, volume 05.01.[31] EN ISO 660-1996, Calculating acidity number in vegetable oils.[32] ASTM 2003-D2709: Standard test methods for humidity and sediment in

middle distillate fuels by centrifuge, Annual Book of ASTM Standards, volume05.01.

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Table 4Physical properties of produced biodiesels and conventional diesel.

Property Palm oil ASTM Stand. Using NaOH Using KOH Petro diesel a

Kinematic viscosity (40 8 C) (mm 2 /s) 39.4 1.96 4.59 4.61 3.06Flash point ( 8 C) 256 Min. 130 164 166 69Density (g cm 3 ) 0.881 0.875 0.876 0.855Acid number (mg KOH/g) 0.1 Max. 0.5 0.24 0.16 0.11Water and sediment (vol %) 0.03 Max. 0.050 0.042 0.036 Cetane number b 40 Min. 47 49.13

49.5c

49.05 50

a Ref. [45] .b Calculated from the correlation presented in Ref. [33] using fatty acid methyl esters proles.c Measured by The National Iranian Oil Products Distribution Company (NIOPDC).



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[41]

Casas

A,

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MJ,

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interesterication

of

sun-ower oil with methyl acetate for biodiesel and triacetin production. ChemicalEngineering Journal 2011;171:132432.

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[46]

ASTM

2003-D6751:

Standard

specication

for

biodiesel

fuel

blend

stock(B100) for middle distillate fuels, Annual Book of ASTM Standards, Volume05.03.


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