Supercritical Synthesis of Ethyl Esters via Transesterification from Waste Cooking Oil Using a Co-Solvent


Biofuels became more promising alternative to the fossil fuels because of the depletion of fossil resources, renewability, environmental benefits, and energy security. Ethanolysis of waste cooking oil with hexane as co-solvent was carried out for the production of fatty acid ethyl ester (FAEE). This process reduced the severity of process parameters with high purity biodiesel yield. Process variables such as co-solvent ratio, ethanol to oil molar ratio, reaction temperature and reaction time were optimized. The maximum biodiesel yield of 88% was obtained at ethanol/oil molar ratio of 40:1, co-solvent (hexane) to oil ratio of 0.2% (v/v), reaction temperature of 300°C in 20 min of reaction time. Fatty acid ethyl ester (biodiesel) samples produced from this process were measured and evaluated using GC-MS analytical instrument. Thermo gravimetric analysis (TGA) was also performed to examine the thermal stability of waste cooking oil, ethyl esters and fuel blends. Fuel properties of ethyl esters were determined and compared with the ASTM standards for biodiesel, regular diesel and ethyl esters from different feedstock.

Share and Cite:

Muppaneni, T. , Reddy, H. and Deng, S. (2015) Supercritical Synthesis of Ethyl Esters via Transesterification from Waste Cooking Oil Using a Co-Solvent. Journal of Environmental Protection, 6, 986-994. doi: 10.4236/jep.2015.69087.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Krisada, N., Pisitpong, I., Apanee, L. and Samai, J.I. (2009) A Comparative Study of KOH/Al2O3 and KOH/NaY Catalysts for Biodiesel Production via Transesterification from Palm Oil. Renewable Energy, 34, 1145-1150.
[2] Antolin, G., Tinaut, F., Briceno, Y., Castano, V., Perez, C. and Ramirez, A. (2002) Optimization of Biodiesel Production by Sunflower Oil Transesterification. Bioresource Technology, 83, 111-114.
[3] Muppaneni, T., Reddy, H.K., Patil, P.D., Dailey, P., Aday, C. and Deng, S. (2012) Ethanolysis of Camelina Oil under Supercritical Condition with Hexane as a Co-Solvent. Applied Energy, 94, 84-88.
[4] Gui, M.M., Lee, K.T. and Bhatia, S. (2008) Feasibility of Edible Oil vs. Non-Edible Oil vs. Waste Edible Oil as Biodiesel Feedstock. Energy, 33, 1646-1653.
[6] Supple, B., Holward-Hildige, R., Gonzalez-Gomez, E. and Leashy, J.J. (2002) The Effect of Stream Treating Waste Cooking Oil on the Yield of Methyl ester. Journal of the American Oil Chemists’ Society, 79, 175-178.
[7] Kulkarni, M.G. and Dalai, A.K. (2006) Waste Cooking Oil—An Economical Source for Biodiesel, a Review. Industrial & Engineering Chemistry Research, 45, 2901-2913.
[8] Saka, S. and Kusdiana, D. (2001) Biodiesel Fuel from Rapeseed Oil as Prepared in Supercritical Methanol. Fuel, 80, 225-231.
[9] Demirbas, A. (2002) Biodiesel from Vegetable Oils with MgO Catalytic Transesterification in Supercritical Methanol. Energy Conversion and Management, 43, 2349-2356.
[10] Demirbas, A. (2005) Biodiesel Production from Vegetable Oils via Catalytic and Non-Catalytic Supercritical Methanol Transesterification Methods. Progress in Energy and Combustion Science, 31, 466-487.
[11] Alenezi, R., Santos, R.C.D., Raymahasay, S. and Leeke, G.A. (2013) Improved Biodiesel Manufacture at Low Temperature and Short Reaction Time. Renewable Energy, 53, 242-248.
[12] Maddikeri, G.L., Pandit, B.A. and Gogate, R.P. (2012) Intensification Approaches for Biodiesel Synthesis from Waste Cooking Oil: A Review. Industrial & Engineering Chemistry Research, 51, 14610-14628.
[13] Yin, J.Z., Xiao, M. and Song, J.B. (2008) Biodiesel from Soybean Oil in Supercritical Methanol with Co-Solvent. Energy Conversion and Management, 49, 908-912.
[14] Han, H.W., Cao, W.L. and Zhang, J.C. (2005) Preparation of Biodiesel from Soybean Using Supercritical Methanol and CO2 as Co-Solvent. Process Biochemistry, 40, 3148-3151.
[15] Patil, P.D., Gude, V.G. and Deng, S. (2010) Transesterification of Camelina Sativa Oil Using Supercritical and Subcritical Methanol with Cosolvents. Energy & Fuels, 24, 746-751.
[16] Freedman, B., Butterfield, R.O. and Pryde, E.H. (1986) Transesterification Kinetics of Soybean Oil. Journal of the American Oil Chemists’ Society, 63, 1375-1380.
[17] Attanatho, L., Magmee, S. and Jenvanitpanjakul, P. (2004) Factors Affecting the Synthesis of Biodiesel from Crude Palm Kernel Oil. The Joint International Conference on Sustainable Energy and Environment (SEE), Hua Hin, 1-3 December 2004, 359-361.
[18] Garcia, M., Gonzalo, A., Sanchez, J.L., Arauzo, J. and Simoes, C. (2011) Methanolysis and Ethanolysis of Animal Fats, A Comparative Study of the Influence of Alcohols. Chemical Industry and Chemical Engineering Quarterly, 17, 91-97.
[19] Demirbas, A. (2008) Studies on Cottonseed Oil Biodiesel Prepared in Non-Catalytic SCF Conditions. Bioresource Technology, 99, 1125-1130.
[20] Demirbas, A. (2007) Biodiesel from Sunflower Oil in Supercritical Methanol with Calcium Oxide. Energy Conversion and Management, 48, 937-941.
[21] Oliveira, J.R., Silva, R.B., Moura, E.M. and Moura, C.V.R. (2008) Biodiesel of Tucum Oil, Synthesized by Methanolic and Ethanolic Routes. Fuel, 87, 1718-1723.
[22] Patil, P.D., Gude, V.G., Reddy, H.K., Muppaneni, T. and Deng, S. (2012) Biodiesel Production from Waste Cooking Oil Using Sulfuric Acid and Microwave Irradiation Processes. Journal of Environmental Protection, 3, 107-113.
[23] Lang, X., Dalai, A.K., Bakshi, N.N., Reaney, M.J. and Hertz, P.B. (2001) Preparation and Characterization of Biodiesel from Various Bio-Oils. Bioresource Technology, 80, 53-62.
[24] Muppaneni, T., Reddy, H.K., Ponnusamy, S., Patil, P.D., Sun, Y., Dailey, P. and Deng, S. (2013) Optimization of Biodiesel Production from Palm Oil under Supercritical Ethanol Conditions Using Hexane as Co-Solvent, A Response Surface Methodology Approach. Fuel, 107, 633-640.
[25] Dijkstra, A. (2006) Revisiting the Formation of Trans Isomers during Partial Hydrogenation of Triacylglycerol Oils. European Journal of Lipid Science and Technology, 108, 249-264.
[26] ASTM, American Standards for Testing of Materials (2008) D 189-01, D 240-02, D 4052-96, D 445-03, D 482-74, D 5555-95, D 6751-02.
[27] Goering, C.E., Schwab, A.W., Daugherty, M.J., Pryde, E.H. and Heakin, A. (1982) Fuel Properties of Eleven Vegetable Oils. Transactions of the ASABE, 25, 1472-1477.
[28] Graboski, M.S. and McCormick, R.L (1982) Combustion of Fat and Vegetable Oil Derived Fuels in Diesel Engines. Progress in Energy and Combustion Science, 24, 125-164.

Copyright © 2022 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.