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49

BIODIESEL PRODUCTION FROM COTTONSEED & PONGAMIA OIL

M.P. Sharma

ABSTRACT

Indiscriminate use of fossil fuels coupled with serious gaseous emissions has led to thesearch for alternative to diesel fuel in recent years. Among oil resources, cotton seed & Pongamiaoil were choosen to investigate the kinetics of transesterification for conversion to biodiesel(methyl/ethyl ester). The paper reviews the transesterification, effect of various parameters, oilsand biodiesel properties with emphasis on the kinetics of reactions as well as techno-economicevaluation of biodiesel production. The kinetic data indicate that the reaction of conversion fromTriglycerides (TG) to Diglycerides (DG) is fastest, slower from Diglycerides to Monoglycerides(MG) & slowest from MG to methyl ester and glycerine. It is evidenced by the kinetic data that at70°C & 6:1 molar ratio, the value of K1 to K3 increases while K4-K6 decreases in the case ofcotton seed oil while value of K1-K6 decreases in the case of Pongamia oil giving only 56% and69% yield of ME respectively. Further increase in molar ratio to 9:1 results in 70% yield of MEin both the cases. Under optimum conditions of temp. & molar ratio of methanol to oil (70°C at6:1), the cotton seed & Pongamia oil yielded 0.688 kg biodiesel / kg of both the oils, but pooryield of biodiesel (0.070 kg) from cotton seed compared to Pongamia oil (0.30 kg/kg of oil). Atechno economic analysis of various oils indicated that cost of production of biodiesel is minimumfrom Pongamia (Rs. 10.50) and maximum from sesame oil (Rs. 54/-) with Rs. 14.22/- from cottonseedoil compared to diesel (Rs.38/- per liter).

Keywords: Vegetable oils, Transesterification, Reaction kinetics, Biodiesel, Methanol, Glycerol,Methyl Esters, Triglycerides.

INTRODUCTION

In recent years, the world over energy crisis owingto depleting fossil fuel resources and increasedenvironmental problems has initiated the search forsustainable and environment friendly alternative fuels.For the developing countries, the biofuels like biomass,biogas, alcohol, vegetable oils, synthetic fuels etc arebecoming important which can be used directly whileothers need some sort of modification before they areused as substitute of conventional fuels.

As per an estimate, India consumed about 40.34million tones (MT) of diesel during 2000-01, which was43.2% of the total consumption of petroleum products(MNRE, 2007) and two third of the demand was metby import costing about Rs. 20,000/- crores. With the

expected growth rate of diesel consumption of morethan 14% per annum, shrinking crude oil reserves andlimited refining capacity, India have to heavily dependon imports of crude. This situation has forced the searchfor alternative fuel like biodiesel as substitute of biodiesel.

A number of studies of acid and base catalyzedtransesterification of vegetable oils have been reportedin the literature. More than 95% yields of fatty esterusing alkaline catalyst has been achieved in 1 hr. byFreedman et. al (1984). Freedman et. al. (1986), studiedthe kinetics of transesterification of soyabean oil andfound that the value of k (reaction rate constant)increases with increase in temp. and the order ofmagnitude of k is k2MG>k2DG>k2TG and the activationenergies for TG-DG, DG-MG and MG-ME were 14.7,14.2 and 6.4 k cal/mole. It was also found that formaximum ester yield, the acid value should be less than1mg KOH/g of oil with moisture free alcohol andvegetable oil. The effect of catalysts on methyl and ethyl

Alternate Hydro Energy Centre, Indian Institute of Technology,Roorkee

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esters of rapeseed oil at room temperature was studiedby Nye and Southwell (1983). A New method ofproducing methyl ester much faster has been developedwhere acid and base catalysed process using frying oilwere compared (Noureddinin, 1997; Ali et al, 1995 andRao and Gopalakrishnan, 1991). The Kinetics oftransesterification of rapeseed oil to biodiesel usingsupercritical and other methods has been studied todevelop kinetic parameters for reactor design(Noureddini, 1997; Fillieres et. al, 1995 and Formo,1954). The acid catalysed production of biodiesel fromwaste frying oil was developed by Zheng et al (2006)who reported that the transesterification reaction is ofpseudo first order and is 99% completed within 4 hrsperiod with no detection of monoglycerides in thebiodiesel. Barnwal and Sharma (2005) has explored thepossibility of biodiesel production from vegetable oilresources in India and it was shown techno-economically that the cost of biodiesel from linseed oilis cheaper (Rs. 15.56) and highest from Sesam oil(Rs.54/-) compared to diesel (Rs. 38/- per liter). As pera study, about 596 million litres of biodiesel has beenestimated to be needed for the year 2020 for UttarPradesh State Road Transport Corporation (Chauhanet al, 2007) using Jatropha oil. Kose et al (2002) havecarried out immobilized lipase catalysed alcoholysis ofcotton seed oil in a solvent free medium. Simoni et al(2006) have used classical catalytic system for

ethanolysis of caster & cotton seed oil and found thatmost efficient esterification of castor oil than cottonseedoil is possible by base catalysts. Transesterification ofPongamia oil using KOH as catalyst & methanol assolvent was carried out by Karmee and Chadha (2005)who achieved 92% methyl ester yield using solid acidcatalysts like H-Zeolite, montmorillonite K-10 and ZnO.The above literature has revealed no much work oncotton seed (edible) and Pongamia (non-edible oil).

The present paper reviews biodiesel resources, theproduction of biodiesel, processes developed/ beingdeveloped, the kinetic studies of transesterification ofPongamia oil & Cottonseed oil, fuel characteristics, andtechno-economic analysis of the biodiesel production.The findings reveal that the transesterification reactionof Pongamia oil is slower than cottonseed but yields ofbiodiesel from the former is more (0.30 kg) than thelater (0.070 kg/kg of oil).

Triglycerides as substitute diesel fuel

The use of vegetable oils e.g. palm, soyabean,sunflower, peanut, olive oils etc as alternative fuels fordiesel engines dates back almost nine decades, but dueto the rapid decline in crude oil resources, the use ofvegetable oils as substitute of diesel has been againpromoted in different countries who are looking fordifferent types of vegetable oils as a substitute of diesel

Table 1 Production of Oilseeds (2002–2003) in India

Name of oil seed

Total production (Annual) Million

tonne (MT)

Seed Production,

[T/ha]

% Total oil availability

(MT)

Oil recovery (% age of

seed)

Cost (Rs./

ton of oil

Soya bean 123.2 4.30 0.63 17 4300 Cotton seed 34.3 4.60 0.39 11 3200 Groundnut 19.3 4.60 0.73 40 6200 Sunflower 25.2 1.32 0.46 35 5360 Rape seed 34.7 4.30 1.37 33 5167 Sesame 2.5 0.62 NA NA 6800 Palm kernels 4.8 NA NA NA NA Copra 4.9 0.65 0.42 65 3035 Linseed 2.6 0.20 0.09 43 NA Castor 1.3 0.51 0.21 42 NA Niger 0.8 0.08 0.02 30 NA Rice Bran NA NA 0.60 15 2000 Pongamia oil NA 7-9 1.75-2.25 25 2588 Total 253.6 21.18-30.18 6.67-7.71 - -

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(Krawczyk, 1996). For example, Soyabean oil in U. S.,rapeseed and sunflower oils in Europe, Palm oil in south-east Asia (mainly Malaysia and Indonesia) and coconutoil in the Philippines are considered as substitute fordiesel. The production of oil seeds, % oil recovery &respective cost is given in Table 1 which indicates thatthe use of vegetable oils as the source of diesel wouldrequire more efforts to be made to increase theproduction of oil seeds and to develop new and high oilyielding seed plant species (Annoymous, 1996 andGoering et al, 1982). Keeping in view that primary focusof seed oil production is to meet the human oilrequirements for edible purposes, some species of non-edible oils e.g. Jatropha, Pongamia and Karanji may

play significant role in providing resources which maybe grown on massive scale on agricultural/degraded/waste lands so that the cheap resources may be availablefor the production of biodiesel as “Farm fuel”.

Chemical Compositions

The vegetable oils comprise of 98% triglyceridesand small amounts of mono and di-glycerides.Triglycerides are esters of free fatty acids (FFA) andone glycerol molecule and contain substantial amountsof oxygen. Fatty acids vary in carbon chain length andin the number of double/triple bonds. Various type ofoils have different types of fatty acids attached withglycerol. The empirical formula and type of fatty acids

Table 2 Chemical structure of common fatty acids

Name of Fatty acid

Chemical name of Fatty acids

Structure

(xx:y)a

Empirical Formula

Lauric Dodecanoic 12 : 0 C12H24O2 Myristic Tetradecanoic 14 : 0 C14H28O2 Palmitic Hexadecanoic 16 : 0 C16H32O2 Stearic Octadecanoic 18 : 0 C18H36O2 Arachidic Eicosanoic 20 : 0 C20H40O2 Behenic Docosanoic 22 : 0 C22H44O2 Lignoceric Tetracosanoic 24 : 0 C24H48O2 Oleic cis-9-Octadecenoic 18 : 1 C18H34O2 Linoleic cis-9,cis-12-Octadecadienoic 18 : 2 C18H32O2 Linolenic cis-9,cis-12,cis-15-

Octadecatrienoic 18 : 3 C18H30O2

Erucle cis-13-Docosenoic 22 :1 C32H42O2

axx indicates no. of carbon and y, no. of double bonds in the fatty acid chain

Table 3 Properties of Vegetable Oils Vegetable oil Kinematic

viscosity at 40 0C(mm2

/s)

Cetane no. (0C)

Heating value

(MJ/Kg)

Cloud point (0C)

Pour point (0C)

Flash point (0C)

Density (Kg/l)

Corn 34.9 37.6 39.5 -1.1 -40.0 277 0.9095 Cottonseed 33.5 41.8 39.5 1.7 -15.0 234 0.9148 Crambe 53.6 44.6 40.5 10.0 -12.2 274 0.9048 Linseed 27.2 34.6 39.3 1.7 -15.0 241 0.9236 Peanut 39.6 41.8 39.8 12.8 -6.7 271 0.9026 Rapeseed 37.0 37.6 39.7 -3.9 -31.7 246 0.9115 Safflower 31.3 41.3 39.5 18.3 -6.7 260 0.9144 Sesame 35.5 40.2 39.3 -3.9 -9.4 260 0.9133 Soyabean 32.6 37.9 39.6 -3.9 -12.2 254 0.9138 Sunflower 33.9 37.1 39.6 7.2 -15.0 274 0.9161 Palm 39.6 42.0 - 31.0 - 267 0.9180 Babassu 30.3 38.0 - 20.0 - 150 0.9460 Pongamia 36.4 42.2 39.7 1.9 -16.0 150 0.9135 Diesel 3.06 50 43.8 - -16 76 0.855

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present in vegetable oils are given in Table 2 (Marckley,1960).

Properties of Vegetable oils as Fuel

The fuel properties of vegetable oils as listed inTable 3 indicates the kinematic viscosity of vegetableoils varies from 30 to 40 cst at 380C. High viscosity ofthese oils is due to large molecular mass in the range of600 to 900, which is about 20 times more than the diesel.The flash point of vegetable oils is very high (above2000). The energy contents in the range of 39 to 40 MJ/kg are lower than diesel (about 45 MJ/kg). Thepresence of chemically bound oxygen in vegetable oilslowers their heating value by about 10%. The cetanenumbers are in the range of 32 to 40.

Use of Vegetable Oils as Diesel Fuel

The raw vegetable oils can, however, be used assubstitute of diesel in diesel engines. The injection,atomization and combustion characteristic of vegetableoils in diesel engines are significantly different fromdiesel. The high viscosity of vegetable oils interfereswith the injection process and leads to poor fuelatomization. The inefficient mixing of oil with aircontributes to incomplete combustion, thereby, emittingheavy smoke and high flash point attributes to its lowervolatility characteristics. These factors coupled withreactivity of unsaturated vegetable oils do not allow theengine to operate in trouble free mode for longer periodof time and can be overcome only by modifying theraw oil.

Utilization of bio-diesel

Bio-diesel is the monoalky ester of long-chain fatty

acids derived from renewable feedstocks such asvegetable oils or animal fats for use in compressionignition (CI) engines. The bio-diesel has been provedas a possible substitute or extender of conventional dieseland is comprised of fatty acid methyl/ethyl esters madefrom the triglycerides by transesterifcation withmethanol/ethanol respectively. Bio-diesel is compatiblewith conventional diesel and both can be blended in anyproportion.

Fuel properties of bio-diesel

The fuel properties of bio-diesel and diesel fuel asgiven in Table 4 (Feuge and Gros, 1949; Dunn and Bagby,1995 and Chang et al, 1996) show the good resemblanceand make bio-diesel as a strong alternative to diesel.The biodiesel (methyl ester) has 1/3 to 1/4 less molecularweight than straight vegetable oil (500) and viscosity isreduced by a factor of about 1/8 of the oil. It contains10 to 11% more oxygen (v/w), thus, enhancing itscombustion in engine. It is also reported that the use oftertiary fatty amines and amides can also enhance theignition quality of the biodiesel without having anynegative effect on its cold flow properties (Agarwal,1988 and 1996). The starting problem, however, persistsin cold conditions. Further, the biodiesel has 12% lowervolumetric heating values, high cetane number and flashpoint. The cloud point and flash points of biodiesel are15° to 25C° higher than the diesel.

BIODIESEL PRODUCTION PROCESS

Transesterification Reaction

The details of chemistry of transesterifications,catalysts, alcohol and other conditions have already beenreported in our earlier paper (Barnwal and Sharma, 2005)

Table 4: Properties of Biodiesel from different oils Vegetable

oil methyl esters

(Bio diesel)

Kinematic viscosity (mm2/s) at 40°C

Cetane no.

Lower heating value

(MJ/Kg)

Cloud point (0C)

Pour point (0C)

Flash point (0C)

Density (Kg/l)

Peanut 4.9 54 33.6 5 - 176 0.883 Soyabean 4.5 45 33.5 1 -7 178 0.885 Babassu 3.6 63 31.8 4 - 127 0.875 Palm 5.7 62 33.5 13 - 164 0.880 Sunflower 4.6 49 33.5 1 - 183 0.860 Tallow - - - 12 9 96 - Cotton seed 4.0 48 34.8 - -15 150 0.8850 Pongamia 4.2 50 33.5 - - 174 0.8941 Diesel 3.06 50 43.8 - -16 76 0.855

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Optimum reaction conditions for the maximum yieldof methyl esters have been reported as 0.8 % (w/w) ofpotassium hydroxide catalyst and 100 % excessmethanol at room temperature for 2.5 hours. Glycerolseparation does not occur if < 67% of the theoreticalamount of methanol is used. The excess methanol isusually removed by distillation. The traces of methanol,KOH, free fatty acids (FFA), chlorophyll etc associated

with glycerine phase can be processed such that about90-95 % of glycerine is obtained in 98% pure form infirst stage itself. The process schematic of biodieselproduction is given in Fig. 1. The glycerin, being heavier,forms the bottom layer and the upper organic layer isseparated as biodiesel (esters). The esters are washedwith water for the catalyst recovery and finally driedusing silica gel. The biodiesel is now suitable for blendingin desired blends for engine operation.

Vegetable oils Recycled

Dilute acid Sulphur + methanolEsterification

Methanol + KOHTransesterification

Methanol Crude Glycerin Crude bio-diesel Recovery

Glycerin Refining Refining

Glycerin BiodieselResidue

Fig. 1 Basic Transesterification Process

Production Process Variables

The most important variables influencing thetransesterification reaction are:

Reaction Temperature

The rate of reaction is strongly influenced by thereaction temperature and therefore, it is carried out closeto the boiling point of methanol (60° to 70°C) atatmospheric pressure. Such mild conditions require theremoval of FFA from the oil by refining or pre-esterification and hence the degummed and deacidifiedoil is usually used as feedstock. This pretreatment is,however, not required, if the reaction is carried out underhigh pressure (9000 k Pa) and high temperature (240°C)when the simultaneous esterification andtransesterification take place with maximum yieldobtained at temperature ranging from 60° to 70°C at amolar ratio of 6:1 (Feuge and Gros, 1949; Hui, 1996 andSaka and Dadan, 2001).

Ratio of Alcohol to Oil

Stoichiometrically, the reaction requires 3 mole ofalcohol per mole of triglyceride to give 3 moles of fatty

esters and 1 mole of glycerol (Zheng et al, 2006). Toshift the reaction to the right, use of either excess alcoholor removal of one of the products from the reactionmixtures becomes necessary. The second option isusually preferred for the reaction to proceed tocompletion. A molar ratio of 6:1 is normally used inindustrial processes to obtain methyl ester yields higherthan 98% (w/w).

Catalysts

Alkali metal alkoxides are the most effectivetransesterification catalysts compared to the acidiccatalysts e.g. sodium alkoxides are the most efficientcatalysts, although KOH and NaOH can also be used.Transmethylation occurs both in presence of an alkalineand acidic catalyst (Agarwal, 1988). Alkaline catalysts,being less corrosive, are preferred more in the industrialprocesses. Concentration in the range of 0.5 to 1% (w/w) has been reported to achieve 94 to 99% conversionof vegetable oil into esters (Formo, 1954 & Feuge andGros, 1949).

Mixing Intensity

The mixing plays significant role during the reaction.

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After phase separation, the mixing becomesinsignificant.

Purity of Reactants

Impurities in the oil affect the conversionconsiderably as evident from the fact that about 65 to84% conversions of crude vegetable oils have beenobtained compared to 94 to 97% convession of refinedoil under the same conditions. The FFA contents in thecrude oils interfere with the catalyst and can be avoided,if the reaction is carried under high temperature andpressure conditions.

Supercritical Methanol (Catalysts free)Transesterification

The considerable time consuming and catalystseparation problem faced during the above process canbe solved by using supercritical methanol method oftransesterification, because, the tendencies of two-phaseformation of vegetable oil/methanol mixture is eliminateddue to decrease in dielectric constant of methanol insupercritical state. As a result, the reaction was foundto be complete in a very short time within 2-4 min.Further, since no catalyst is used, the purification ofbiodiesel is much easier, trouble free & environmentfriendly (Encinar et al, 1999).

The result of transesterification of rapeseed oil insupercritical methanol method has indicated that attemperature of 239°C and pressure of 8.09 Mpa,glycerol and methyl esters are obtained as principleproducts (Encinar, et al, 1999). Diasakev et al, (1998)have reported the optimal molar ratio of methanol toCynara oil between 4.05-5.57, beyond which either thecatalytic transesterification is incomplete or glycerinseparation becomes very difficult. More than 98%conversion of vegetable oils to the methyl esters couldbe achieved at the molar ratio of 6:1. When the oilcontains a high FFA contents, higher molar ratio evenupto 45:1 is also used. (Freedman et al, 1984 andDarnokes and cheryan, 2000).

It is also observed that under supercritical conditionsthat the conversion of rapeseed oil increased withincrease in molar ratio of methanol and oil & completeconversion with 95% yield took place with molar ratioof 42:1 of 42 (Encinar et al, 1998) at a criticaltemperature of 350°C, while conversion of rapeseed oilto methyl esters was incomplete at molar ratio of lessthan 6:1.

KINETICS OF TRANSESTERIFICATION

Literature survey reveals that no work has beenreported on transesterification kinetics of Cottonseedoil & Pongamia oil. However, the kinetics oftransesterification reaction of other oils like Soyabean,Rapeseed, waste cooking oils etc is available in theliterature. Darnokes and cheryan (2000) have studiedthe kinetics of transesterification of palm oil in a batchreactor and reported the reaction to be of second orderupto 30 minutes and thereafter, it became first orderand then zero order. Noureddini & Zhu (1997) studiedthe transesterification of soyabean oil and found it ofpseudo second order reaction. Kusdiana and Saka(2001) studied the kinetics of supercritical methanoltransesterification of rapeseed oil and found the reactionof first order.

Experimental Set Up

The reactions were performed in a 1-L three-neckedglass reactor equipped with a reflux condenser, athermometer, a sample withdrawing port and stirrer. Thewhole reactor was immersed in a constant temperaturewater bath having precise temperature control (±0.2°C). Agitation of reaction mixture was carried by amechanical stirrer to constant speed throughout theperiod of experiment.

Materials

Refined and bleached cottonseed oil & pongamiaoil were obtained from local market. Free fatty acid(FFA.) of the oil were found about 1%. Analytical gradeanhydrous methanol, potassium hydroxide & otherchemicals of high purity were used. The chemicals forstandardization were procured from Sigma chemicalcompany (Germany).

Reaction Conditions

The various mole ratios of methanol to oil i.e. 3:1,6:1 and 9:1 have been used at different temperature of50°C, 60°C and 70°C. The reactor was initially filledwith 500 ml vegetable oil and heated to the desiredtemperature. A known amount of KOH catalyst wasdissolved in the measured amount of methanol andheated separately to the desired temperature. Theheated methanolic KOH was then added slowly toreaction mixture in the reactor to prevent evaporationof methanol. The reactor contents were reflexed for 90minutes and 5ml sample was withdrawn quickly fromthe reactor at a interval of 10 minutes and analysed by

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Gas Chromatography (GC) for TG, DG, MG and MEconcentration. The concentration of each was computedfrom the chromatographic data. The yield data werefitted in kinetic equations to calculate the differentreaction rate constants from K1 to K6 and the resultsare reported in table 5 & 6 for Cottonseed & Pongamiaoil respectively. The variation of % ME yield from cottonseed & Pongamia oil is shown in Fig. 2 & Fig. 3respectively.

Analytical Standards

The standard chemicals for calibration of GasChromatograph were prepared and used as perprocedure described by Hui (1996) and Clark et al(1984). Netel Make Gas Chromatograph equipped withan on-column injector fused-silica capillary column(10m×0.32mm I.D) coated with a 0.1-µm film of DB-5and a flame ionization detector (FID) was used for theanalysis of reaction products. Acquisition and processingof data was performed with an IBM compatible PC.

Aliquots of 1 µ ml were injected into GC at anoven temperature of 50°C. After an isothermal periodof 1 minute, the GC oven was heated at 15°/min to180°C, at 7°C/min to 230°C and ballistically to 370°C(held for 10 min). Nitrogen was used as carrier gas at aflow-rate of 3 ml/min at 50°C. Detector temperaturewas 370°C. The nitrogen served as detector make upgas at an inlet pressure of 0.5 bar. Time for each runwas 30 min.

The final reaction results in the 2 phases: upperorganic and lower glycerol phase. The upper layer waswashed thrice with water and the resulting methyl ester(biodiesel) was boiled to remove moisture to get purebiodiesel. The purity was checked using thin layerchromatography & flash point.

RESULTS & DISCUSSIONS

Diasakov (1998) reported six different rate constantsfor the whole transesterification reaction. The finalproducts of transesterification reaction are methyl esters(biodiesel) and glycerol and accordingly, a simplermathematical model was developed by ignoring theintermediate reactions and converting 3 steps to onesteps as follow:

k1

TG + CH3 OH DG + RI COORk2

k3DG + CH3 OH MG + RII COOR

k4

k5MG + CH3 OH ME + RIII COOR

k6

CH—COOR1 Catalyst C H2 OH RI COOCH3 k1 +

CH—COORII + 3 CH3 OH CHOH + RII COO CH3 k2 +

CH3—COORIII CH2OH RIII COO CH3Triglyceride Methanol Glycerol (Biodiesel)

R’ = R’’ = R’’’ = Same or different long chainhydrocarbon molecule.

This above reaction is assumed to be of first order,being the function of the concentration of triglyceride(TG) and reaction temperature.

Each of the above reaction is reversible with adifferent rate constant (kn) which denotes that theforward and reverse reactions occur at different rates.Since these reactions are of second order (or pseudo-second order) and so can be expressed as the rate ofthe various components in a series of differentialequations.

The rate of various reactions are expressed by thefollowing equations:

(i)[ ]dtTGd

= -K1 [TG][A]+K2[DG][ME]

(ii)[ ]dtDGd

= -K1 [TG][A]+K2[DG][ME] –K3

[DG][A]+K4 [MG][ME]

(iii)[ ]dtMGd

= K3 [DG][A]-K4[MG][ME]-

K5[MG][A]+k6[GL][ME]

(iv)[ ]dtGLd

= K5 [MG][A] –K6[GL][ME]

(v)[ ]dtMEd

= K1[TG][A]-K2[DG][ME]

+K3[DG][A]+K4[MG][ME] = K5[MG][A]-K6[GL][ME]

(vi)[ ]dtAd

= - [ ]dtEd

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where [TG] denotes the molar concentration of thetriglyceride[DG] denotes the molar concentration of the diglyceride[MG] denotes the molar concentration of themonoglyceride[A] denotes the molar concentration of the methanol[ME] denotes the molar concentration of the methylester[GL] denotes the molar concentration of the glycerol

The results given in Table 5 and 6 show that lowervalue of K under the conditions of temp. & molar ratioof alcohol to oil indicate the slower rate of reaction,while the higher value of K indicates the higher rate ofreaction. As can be seen that at 70 ºC & 6:1 molarratio, the value of reaction rate constants K1 & K3 ishigher than at 50° & 60°C indicating that increase intemp. from 50°-70°C enhance the rate of reactions. Inthis optimum ratio at 70°C, there is an increase in rateconstant from K1 to K3 and decrease from K4 to K6indicating that conversion of TG to DG is slowest whileconversion DG to MG is faster and fastest from MG toME & glycerol in the case of cottonseed while in thecase of Pongamia oil, value of K1 to K6 is decreasingshowing the overall reaction is quite slow. In the presentstudy, the uncertainties and confidence level has notbeen calculated as the Gas chromatograph, which hasbeen used to compute the % ME, was calibrated usingstock solution of Heptamethyldecanoid in n-heptanesolvent. At 70°C and 6:1 mole ratio. However, at 70°Cand 6:1 molar ratio, 50% yield of ME was obtained fromcotton seed and 69% from Pongamia oil. However, at700C and 9:1 molar ratio, 69% yield of ME was obtainedfrom cottonseed while 70% from Pongamia oil (Fig. 2& 3). It may, therefore, be inferred that a maximum of70% yield of ME can be obtained at higher molar ratioof 9:1. Under these conditions, the rate of reaction isfastest in the initial stage which decreases with timeand finally the conversion of MG to glycerine & biodieseltakes longer period of time. Further, it is also found thatPongamia and cottonseed oil yielded 0.688 kg ofbiodiesel per kg of oil but 0.070 & 0.30 kg of biodieselper kg of cotton & pongamia seeds respectively, (Table7) perhaps due to the variation of oil contents in theseeds Fig. 2 and 3 also shows that maximum conversionhas taken place within first 20 minutes in both cottonseed & pongamia oil and thereafter, it becomes almostconstant with very slow reaction. This means that basecatalysed transesterification takes a maximum of 30minutes for 70% yield of ME.

Economic feasibility of Biodiesel

Currently, it is found that production of biodieselfrom vegetable oils is much more expensive due to highcosts of vegetable oils (about four times the cost ofdiesel in India) and therefore, is not competitive withdiesel unless the protection from the tax levies are notgranted/ applied to biodiesel. This can be overcome byusing cheaper non-edible oil resources like Jatropha,Pongamia, Karanji, waste cooking oils etc.

An economic analysis of biodiesel production usingdifferent edible and non-edible oils has been carried outand the results as reported in table 8 indicates that costof biodiesel from Linseed oil is Rs. 13.56 & Rs. 54/-per litre from Sesame oil. The analysis assumed thecost of plant as Rs. 11,74,000/- with installed capacityof 1,00,000 litres per year and depreciation @10%,O&M cost of @2% and plants life of 10 years (Otera,1993). The table shows that the cost of biodieselproduced from Pongamia oil is minimum (Rs. 10.50)followed by Linseed oil (Rs. 13.50), Cottonseed oil (Rs.14.22), Coconut oil (Rs. 18.61) Sesame oil (Rs. 54/-)compared to diesel (Rs. 38/=) per litre. The cost ofproduction of biodiesel could be further lowered by usingnon-edible oils, like neem, mahua, pongamia, karanji,babassu, Jatropha etc used-frying oils, acid oils etc. Thenon-edible oil producing plants can be grown on arableand waste lands, on massive scale for sustainablebiodiesel production.

CONCLUSIONS

Alternative fuels have gained important in recentyears due to depleting petroleum reserves coupled withits environmental concerns. The kinetics oftransesterification of cotton seed & Pongamia oilindicated that the reaction of conversion of TG to DG isslower, DG to MG is fastest and MG to methyl ethylester & glycerol is slowest in both the oil. The wholereaction is of first order. The yield of biodiesel obtainedis 0.688 kg biodiesel per kg of oil from both the resourcewhile it is 0.30 kg and 0.070/kg of seed of pongamia &cotton seed respectively. The production from differentoils indicate that cost of biodiesel is minimum fromPongamia oil (Rs.10.50), cottonseed (Rs. 14.22) andmaximum from sesame oil (Rs.54/-) compared to Rs.38/- per litre of diesel.

ACKNOWLEDGEMENT

The author gratefully acknowledges the financial

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Table 5 Reaction constant of cottonseed oil at different reaction conditions (min-1)

Reaction Condition (Temp. & Molar ratio)

k1 k2 k3 k4 k5 k6

50 0C & 6:1 ratio 0.09 0.074 0.116 0.038 0.036 0.046 60 0C & 6:1 ratio 0.178 0.114 0.318 0.147 0.0187 0.022 70 0C & 6:1 ratio 0.221 0.493 0.558 0.247 0.0437 0.044 70 0C & 3:1 ratio 0.017 0.042 0.05 0.022 0.007 0.015 70 0C & 9:1 ratio 0.681 0.053 1.023 1.75 0.286 0.087

Table 6 Reaction constant of Pongamia oil at different reaction conditions (min-1)

Reaction Condition (Temp. & Molar

ratio)

k1 k2 k3 k4 k5 k6

500C & 6:1 ratio 0.179 0.125 0.114 0.082 0.022 0.026 600C & 6:1 ratio 0.493 0.241 0.558 0.257 0.044 0.048 70 0C & 6:1 ratio 2.6 0.814 0.216 0.151 0.0121 0.003 70 0C & 3:1 ratio 0.093 0.084 0.125 0.051 0.045 0.001 700C & 9:1 ratio 4.56 1.37 0.857 0.613 0.121 0.003

Table 7 Optimum yields

Vegetable oil

Temperature Molar ratio

% Yield of biodiesel (by mole)

Biodiesel Yield(Kg)

ME GL Others per Kg oil Per Kg Seed Pongamia 70 0C 6:1 75 25 0 0.688 0.30 Cottonseed 70 0C 6:1 60 20 20 0.688 0.070

Table 8 Total Cost Per litre of Biodiesel from VariousVegetable Oils

Vegetable Oil

Cost of Vegetable Oil Per litre (RS)

Cost of Biodiesel Per litre

(RS) Groundnut 58 48.28 Mustard 48 38.60 Sesame 64 54.00 Coconut 28 18.61 Safflower 60 50.26 Soyabean 40 30.26 Sunflower 50 40.26 Cotton seed 25 14.22 Linseed 23 13.56 Pongamia 18 10.50 Diesel - 38.00

Fig. 2 Variation of yield of methyl ester from cottonseedoil

Fig. 3 Yield of Methyl ester of Pongamia oil at variousconditions

J. Indian Water Resour. Soc. Vol. 29 No. 1, January, 2009

58

support from Ministry of Human ResourceDevelopment (MHRD), Govt. of India in the form ofResearch Project to carryout this work.

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