Modelling the Kinetics of Jatropha Oil Transesterification

Aldo A. Okullo¹, Abraham K. Temu²

¹Department of Chemistry, Faculty of Science, Kyambogo University (KYU), Kampala, Uganda.
²Department of Chemical and Mining Engineering, University of Dar Es Salam (UDSM), Dar Es Salaam, Tanzania.

DOI: 10.4236/epe.2015.74013                

Abstract

Kinetics of a chemical reaction provides an important means of determining the extent of the reaction and in reactor designs. Transesterification of jatropha oil with methanol and sodium hydroxide as a catalyst was conducted in a well mixed reactor at different agitation speeds between 600 and 800 rpm and temperature range between 35°C and 65°C. The effect of variation of temperature and mixing intensity on rate constants were studied. The initial mass transfer controlled stage was considered negligible using the above impeller speeds and second order mechanism was considered for the chemically controlled kinetic stage. Samples were collected from the reaction mixture at specified time intervals and quenched in a mixture of tetrahydrofuran (THF) and sulphuric acid. The mixture was centrifuged at 2000 rpm for 15 minutes and the methyl ester was separated from the glycerol. The ester was washed with warm water (50°C), dried and analysed using gas chromatography coupled with flame ionization detector (GC/FID) to determine free and total glycerine and methyl ester. A mathematical model was fitted using second order rate law. High temperature and high mixing intensity increased reaction rates. The model fitted well with a high correlation coefficient (R²) of 0.999.

Keywords

Second Order Kinetics, Rate Constants, Jatropha Oil, Transesterification

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Keith, O. (2000) A Review of Jatropha Curcas: An Oil Plant of Unfulfilled Promise. Biomass and Bioenergy, 19, 1-15. http://dx.doi.org/10.1016/S0961-9534(00)00019-2
[2]	Sulle, E. and Nelson, F. (2009) Biofuels, Land Access and Rural Livelihoods in Tanzania. IIED, London.
[3]	Darnoko, D. and Cheryan, M. (2000) Kinetics of Palm Oil Transesterification in a Batch Reactor. Journal of American Oil Chemical Society, 77, 1263-1267. http://dx.doi.org/10.1007/s11746-000-0198-y
[4]	Theerayut, L. (2006) Wisutmethangoon Worawut, Prateepchaikul Gumpon, Tongurai Charktir and Allen Michael, Transesterification of Palm Oil in Series of Continuous Stirred Tank Reactor. Asian Journal of Energy and Environment, 7, 336-346.
[5]	Vicente, G., Martinez, M., Aracil, J. and Estaban, A. (2005) Kinetics of Sunflower Oil Methanolysis. Industrial Engineering Chemistry Research, 44, 5447-5454.
[6]	Vicente, G., Martinez, M. and Aracil, J. (2006) Kinetics of Brassica carinata Oil Methanolysis. Energy and Fuels, 20, 1722-1726. http://dx.doi.org/10.1021/ef060047r
[7]	Noureddini, H. and Zhu, D. (1997) Kinetics of Transesterification of Soybean Oil. Journal of American Oil Chemical Society, 74, 1457-1462.
[8]	Bambase Manolito Jr., E., Nakamura, N., Tanaka, J. and Matsumura, M. (2007) Kinetics of Hydroxide-Catalyzed Methanolysis of Crude Sunflower Oil for the Production of Fuel-Grade Methyl Esters. Journal of Chemical Technology and Biotechnology, 82, 273-280. http://dx.doi.org/10.1002/jctb.1666
[9]	Stamenkovic, O.S., Todorovic, Z.B., Lazic, M.L., Veljkovic, V.B. and Skala, D.U. (2008) Kinetics of Sunflower Methanolysis at Low Temperatures. Bioresource Technology, 99, 1131-1140. http://dx.doi.org/10.1016/j.biortech.2007.02.028
[10]	Leevijit, T., Worawut, W., Gumpon, P., Charktir, T. and Allen, M. (2004) Second Order Kinetics of Palm Oil Transesterification. The Joint International Conference on Sustainable Energy and Environment (SEE), Hua Hin, 1-3 December 2004.
[11]	Freedman Bernard, H., Butterfield Royden, O. and Pryde Everett, H. (1986) Transesterification Kinetics of Soybean Oil. Journal of American Oil Chemical Society, 63, 1375-1380.
[12]	Bruno, W., Maicon, T., Apreciado, M. and Alexander, K. (2006) Modelling Chemical Kinetics of Soybean Oil Transesterification Process for Biodiesel Production: An Analysis of Molar Ratio between Alcohol and Soybean Oil Temperature Changes on the Process Conversion Rate. Bioautomation, 5, 13-22.
[13]	Karel, K., Frantisek, S., Radek, S. and Jaroslav, M. (2002) Kinetics and Mechanism of the KOH-Catalyzed Methanolysis of Rapeseed Oil for Biodiesel Production. European Journal of Lipid Science Technology, 104, 728-737.
[14]	Abdel-Latiff, A.S. and Lamina, A.M. (2010) Determination of the Rate Constants for Consecutive Second Order Irreversible Chemical Reaction Using MATLAB Toolbox. European Journal of Scientific Research, 4, 412-419.
[15]	ASTM International (2009) ASTM D 6751-09 Standard Specification for Biodiesel Fuel (B100) Blend Stock for Distillate Fuels.
[16]	Okullo, A., Temu, A.K., Ntalikwa, J.W. and Ogwok, P. (2010) Optimization of Biodiesel Production from Jatropha Oil. International Journal of Engineering Research in Africa, 3, 62-74.
[17]	Tobias, K. (2004) Kinetic Investigation of Base-Catalyzed Glycerolysis of Fatty Acid Methyl Esters. Doctor of Engineering Dissertation, Faculty of Mathematics and Natural Sciences, Technical University of Berlin Germany, November.