Esterification of free fatty acids present in Jatropha oil: A kinetic study

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1 Indian Journal of hemical Technology Vol. 4, March 7, pp. 3-7 sterification of free fatty acids present in Jatropha oil: A inetic study T S V R Neeharia, Vidhi H Bhimjiyani, Bhushan R Dole, K N rasanna Rani*,, V Y Karadbhajne & R B N rasad entre for Lipid Research, SIR-Indian Institute of hemical Technology, Hyderabad 5 7, India Laxminarayan Institute of Technology, Nagpur 44 33, Maharashtra, India -mail: npr@iict.res.in Received 6 November 5; accepted 7 May 6 Methanesulfonic acid has been used as a catalyst for the esterification of free fatty acids (FFA) present in jatropha oil with methanol. The reaction inetics are estimated for to.5 wt% catalyst concentrations, temperature from 45-6 methanol-ffa mole ratios ranging from : to 5:. The optimum conditions are found to be : methanol-ffa mole ratio wt% catalyst at 6 4 rpm for 7 min which give a maximum conversion of 97.9%. A second-order inetic model for both the forward bacward reactions is proposed to study the reaction. The effect of temperature on the reaction rate constants equilibrium constant has been determined using Arrhenius von t Hoff equations respectively. The heat of reaction is found to be cal/mol. Keywords: Biodiesel, sterification, Free fatty acids, Jatropha, Kinetics, Methanesulfonic acid. In recent years, biodiesel has gained a lot of momentum because of its properties such as low carbon monoxide emissions, particulate matter, high flash point unburned hydrocarbons. Biodiesel consists of long-chain fatty acid methyl esters (FAM) are derived from renewable sources such as vegetable oils or animal fats. Oils lie rapeseed, sunflower, soybean, palm peanut oil, as well as animal fat are being used for the preparation of biodiesel -4. However usage of these oils for biodiesel is limited because of their high cost non availability, this forced some researchers to tae up wor using non-edible oils, animal fats waste cooing oils 5. Non-edible oils lie Jatropha curcas L oil are attractive as potential raw material for the preparation of biodiesel. Jatropha curcas L belongs to the family of uphorbiaceae can grow in arid, semi-arid waste ls 6. Methanesulfonic acid was used to reduce the acidity of crude palm oil prior to the alaline transesterification reaction by Hayyan et al. 7. The authors also used ultrasonic energy for the reduction of FFA in crude palm oil Hayyan et al. 8. Ara et al. 9 studied esterification of palm fatty acids using methanesulfonic acid. The authors showed that the presence of water in the reaction medium gave a negative effect in the reaction velocity. rotonation of the carboxylic moiety of the fatty acid were defined as rate determinant step for the reaction. Tran et al. also used methanesulfonic acid for the production of biodiesel. Fassbender et al. reports a process for preparing fatty acid esters /or fatty acid ester mixtures of monohydric alcohols having to 5 carbon using methanesulfonic acid for preparing fatty acid esters. Biodiesel was produced from the oil of Raphia taedigera Mart commonly nown as jupati, by Leyvison Rafael V. da onceicao et al. using methanesulfonic acid. Gernon et al. 3 reviewed chemical physical characteristics of methane sulphonic acid the short-chain alane sulfonic acids in general. The article emphasis that the conductivity, low solubility aqueous solubility of metal methane sulfonates mae methane sulfonic acid (aq) an ideal electrolyte for many electrochemical processes, especially those involving tin lead. Different aspects of aqueous process effluent treatment, acid recovery metal alane sulfonate salt preparation are discussed. conomic aspects of methanesulfonic acid are also considered. Though literature reports little wor using methane sulphonic acid as catalyst for esterification of free fatty acids in oil there is no detailed inetic study available, hence this wor was taen up with an aim to study the effect of process variables esterification of FFA in Jatropha curcas L oil using methane sulphonic acid as catalyst also interpret the inetic parameters.

2 4 INDIAN J. HM. THNOL., MARH 7 xperimental Section Materials Jatropha curcas L oil with acid value 55. was procured from the local industry (Local Industry, A.). All chemicals used in the experiments such as methanol (99.5%) methane sulphonic acid (99%) were of analytical grade were procured from M/s. Sd. Fine hem. vt. Ltd., Mumbai used as such. Analytical methods Acid value of the oil was determined using AOS method 4. The extent of reaction conversion was based on the titrimetric analysis of the FFA in the samples in the final product. xperimental procedure A 5 ml jaceted glass stirred vessel equipped with mechanical stirrer (propeller type impeller of 5.4 cm diameter), thermocouple, provision for sampling a condenser was used for the esterification of free fatty acids present in jatropha oil. The system was heated by circulating water through the jacet of the reactor from a thermostat Model No F 5. For a typical experiment, jatropha oil (5 g) was charged into the reactor (.3785 g) methane sulfonic acid methanol (69.85 g) were added after the reaction temperature reached 6. The speed of the agitator was maintained constant at 4 rpm. Samples were drawn at regular time intervals of 5 min 3 min. The withdrawn samples were analyzed by titration for the evaluation of free residual acidity. The sample was washed with water in order to arrest the reaction separate the catalyst alcohol from the oil phase, thoroughly dried then analyzed for FFA. The first set of experiments was carried out at different speeds of agitation ranging from 3-45 rpm at a fixed methanol-ffa molar ratio of :, catalyst concentration of % (relative to FFA) temperature of 6. The second set of experiments was carried varying catalyst concentration from.5% to.5% at fixed methanol-ffa molar ratio of : temperature of 6. The third set of experiments was carried out at different methanol-ffa molar ratios of :, 5:, : 5: at a temperature of 6 catalyst concentrations of %. The fourth set of experiments were carried out at different temperatures ranging from 45 to 6 with methanol- FFA mole ratio of : using % catalyst. Statistical analysis The data, presented was analyzed by ANOVA to evaluate the level of statistical significance Kinetic model A second order inetic model in both forward reverse directions was proposed 5 to describe the esterification inetics of FFAs in jatropha oil using methane sulfonic acid as catalyst for the present system. The acid catalyzed esterification reaction by which the conversion of FFA taes place is, R + OOH + R OH R OO R H O () The following assumptions were made in the development of the inetic model for the studied esterification reaction. (i) The rate of non-catalyzed reaction is negligible compared to the catalyzed reaction (ii) The esterification reaction is a reversible heterogeneous process the rate is inetically controlled, (iii) The chemical reaction is taing place in the oil phase (iv) The reaction is second-order in both the forward bacward directions Therefore the inetic equation can be expressed as, d Q R S () where, denotes the concentration of FFA, Q denotes the concentration of methanol, R S are the concentrations of FAM water, respectively, formed during the reaction, are the inetic rate constants for the forward reverse reactions, respectively. As (where is the concentration of acid removed of FFA), Q Q is the initial concentration (where is the initial Q concentration of methanol) M / Q, the q. () becomes, d ( )( ) M (3) The conversion,, then d d By substituting these in q. (3), we get ( )( ) M (4)

3 NHARIKA et al.: STRIFIATION OF FR FATTY AIDS RSNT IN JATROHA OIL 5 Integration of q. (4) yields, [ ( α + β )]( α β ) ( K ) βt ln (5) [ ( α β )]( α + β ) where K ( M + ) α (6) ( K ) ( K ( M + )) 4( K ) KM β (7) ( K ) equilibrium constant, K (8) The conversion as a function of time can be deduced from q. (5) as follows, β ( K ) t ( α β )( e ) β ( K ) t ( α β ) ( α + β ) e (9) Results Discussion Jatropha oil used for the present study contains 4.5% of FFA. The fatty acid composition of the oil was found to be 5.7% palmitic,.5% stearic, 38.9% oleic 33.4% linoleic acids as determined by Gas hromatography. ffect of speed of agitation The effect of agitation on the reduction of acid value, was studied at a fixed methanol-ffa molar ratio of :, catalyst concentration of % 6. Increase in speed of agitation from 3 to 4 rpm increased the conversion of FFA from 74.3% to 97.47% in 7 min. Further increase in agitation speed to 45 rpm, showed negligible increase in the reduction of FFA. It was therefore concluded that a speed of agitation of 4 rpm was above the critical speed required for the given system. All the experiments were conducted with the speed of agitation fixed at 4 rpm. ffect of catalyst concentration The effect of catalyst concentration on the conversion of FFA present in jatropha oil with methanol was studied. atalyst used in the reaction ranged from.5 to.5% based on FFA in jatropha oil. It was observed from Fig. that with an increase in the catalyst concentration from.5 to.%; the conversion reached up to from 75.86%. There was no prominent change by further increase in catalyst from. to.5%, so all the experiments were conducted using.% catalyst, : methanol/ffa mole ratio for 7 min. ffect of methanol to FFA mole ratio ffect of methanol-ffa mole ratio on the esterification of free fatty acids present in jatropha oil was studied using constant % methane sulphonic acid concentration at 6 for 7 min by varying methanol-ffa mole ratios from : to 5:. It is evident from Fig. that with : ratio a conversion of 84.8% was obtained, increasing the ratio to 5: resulted an increase in conversion of 93.6% increasing the methanol-ffa mole ratio to : increased the conversion to 97.87%, further increasing the ratio to 5: did not provide any significant increase in conversion, therefore : methanol-ffa mole ratio was considered for all experiments. ffect of temperature The reaction temperature plays an important role on reaction rate. The effect of temperature on Fig. ffect of the catalyst concentration on the esterification of FFA in jatropha oil at : methanol-ffa mole ratio, 4 rpm 6. Fig. ffect of methanol - FFA mole ratio on the esterification of FFA in jatropha oil at 6 wt% methane sulphonic acid concentration

4 6 INDIAN J. HM. THNOL., MARH 7 esterification of free fatty acids present in jatropha oil using methane sulphonic acid was studied at temperature from 45 to 6 by maintaining other reaction parameters constant. It can observed from Fig. 3 that at 45 a conversion of 56% was achieved, increasing the temperature to 5 resulted a conversion of 66.5% at 55 a value of 8.% was observed further increasing temperature to 6 the conversion was increased to 97.87%. Applying the inetic model Reaction rate constants The forward reaction rate constant,, can be calculated from the initial rates as follows: At t, the initial concentrations of products, R S, are zero i.e., q. (3) becomes, d r M M t o t M () () r M () The initial rates have been calculated using q. (), the effect of mole ratio on initial rate has been plotted in Fig. 4a for % catalyst concentration at 6, the values of have been obtained from the slopes of this plot. By substituting in q. (5), was determined by trial error until the slope of the plot of q. (5) matches the assumed value, as shown in Fig. 4b for : methanol-ffa mole ratio, % catalyst concentration at 6. The inetic rate constants were obtained similarly for 45, 5, 55 6 temperatures. The forward bacward reaction rate constants,, for % catalyst concentration at 6 were lit/(mol min) respectively. Activation energies frequency factors The effect of temperature on the reaction rate constants was obtained by fitting to the Arrhenius equation. RT Ae (3) ln + ln A (4) RT From the plots of ln as a function of the reciprocal temperature, both forward bacward reactions rate constants were obtained, the results are presented in Table. The energy of activation for the forward reaction as well as bacward reaction was found to be.47 cal/mol respectively for forward reaction cal/mol respectively for bacward reaction. quilibrium constant heat of reaction The effect of temperature on equilibrium constant, K, has also been obtained by fitting the data to van t Hoff equation. Fig. 3 ffect of temperature on the esterification of FFA in jatropha oil at : methanol-ffa mole ratio % methane sulphonic acid Fig. 4 (a) Intial rate vs methanol-ffa mole ratio; 4 (b) Determination of the inetic constant ( ) using q. (5) at : methanol-ffa mole ratio, % catalyst concentration 6.

5 NHARIKA et al.: STRIFIATION OF FR FATTY AIDS RSNT IN JATROHA OIL 7 Table Kinetic rate constants equilibrium constant for esterification of FFA in jatropha oil at different reaction conditions. Reaction onditions K R Temperature a ( ) atalyst concentration b (wt%) a At : methanol-ffa mole ratio % methane sulphonic acid b At : methanol-ffa mole ratio 6 Fig. 5 omparison of the experimental predicted conversions H lnk + const. (5) RT The values of equilibrium constant are given Table. From the plot of lnk the reciprocal temperature, the heat of reaction has been obtained was found to be cal/mol with R of.95. omparison of experimental predicted values The fitting of the experimental data to the proposed model was also assessed by comparing the experimental conversion values with the theoretically predicted values using q. (9) is presented in Fig. 5. A p-value of.3563 was obtained by regressing the values using ANOVA which was considered significant. It can be concluded from the plot that the developed inetic model explained the inetics of the esterification of free fatty acids (FFA) in jatropha oil satisfactorily. onclusion Acid value was brought to below mg KOH/g oil within 7 min using % methane sulfonic acid catalyst : methanol-ffa mole ratio at 6 4 rpm as speed of agitation. A inetic model was proposed with second-order inetics for both forward bacward reactions it represented the present system of esterification satisfactorily. The forward bacward reaction rate constants,, for % catalyst concentration at 6 were lit/(mol min) respectively. References Al-Zuhair S, Biofuels Bioprod Bioref, (7) 57. Antolin G, Tinant F V, Briceno Y, astano V, erez & Ramirez A I, Bioresour Technol, 83 (). 3 Al-Widyan M I & Al-Shyouh A O, Bioresour Technol, 85 () Ma F, lements L D & Hanna M A, Bioresour Technol, 69 (999) Zhang Y, Dube M A, Malean D D & Kates M, Bioresour Technol, 89 (3). 6 Rao K S, harabarti, Rao B V S K & rasad R B N, J Am Oil hem Soc, 86 (9) Hayyan A, Mjalli F S, Mirghani M S, Hashim M A, Hayyan M, AlNashef I M & Al-Zahran S M, hem ap, 66 () Hayyan A, Mjalli F S, Hayyan M, AlNashef I M & Mirghani M S, Afr J Biotechnol, () 5. 9 Ara D A G, Santos R T, Tapanes N O, Ramos A L D & Antunes O A, atal Lett, (8). Tran H L, Ryu Y J, Seong D H, Lim S M & Lee G, Biotechnol Bioprocess ng, 8 (3) 4. S Fassbender, U S at 455, 6 October. Da onceicao L R V, Da osta F, Da Rocha Filho G N & Zamian J R, Fuel, 9 () Gernon M D, Wu M, Buszta T & Janney, Green hem, (999) 7. 4 Firestone D, (d.), AOS Official Methods Recommended ractices of the American Oil hemists Society, 5th dn, AOS ress, hampaign 3, d 3d rasanna Rani K N, rathap Kumar T, Neeharia T S V R, Satyavathi B & rasad R B N, ur J Lipid Sci Technol, 5 (3) 69.