Abstract
Previous research suggested that ethyl esters derived from recycled restaurant grease might be a potential source of biodiesel. Accordingly, response surface methodology (RSM) was employed to optimize reaction parameters—temperature, time, level of lipase, mole ratio of reactants—in the PS-30 lipase-catalyzed transesterification reaction of grease to ethyl esters using 95% ethanol. The regression equation obtained by a modified central composite design of RSM predicted optimal reaction conditions of 38.4°C, 2.47 h, 13.7 wt% lipase (PS-30), and a mole ratio of grease to ethanol of 1:6.6. Under these conditions the predicted optimal percentage ethyl ester yield was 85.4%. Subsequent experiments using the predicted parameter combinations indicated a trend where experimental percentage yields of ethyl ester were consistently lower than predicted values. In an effort to improve the experimental yield of esters, a second portion of PS-30 lipase was added without success; however, the addition of 5% SP435 one hour after the start of the initial reaction increased the yield of esters to >96%. Neither lipase PS-30 nor lipase SP435 alone, however, gave the RSM-predicted yield of ethyl esters.
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Wu, W.H., Foglia, T.A., Marmer, W.N. et al. Optimizing production of ethyl esters of grease using 95% ethanol by response surface methodology. J Amer Oil Chem Soc 76, 517–521 (1999). https://doi.org/10.1007/s11746-999-0034-2
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DOI: https://doi.org/10.1007/s11746-999-0034-2