EVALUATION OF THE KINETICS OF A LIPASE CATALYSED BIODIESEL PRODUCTION FROM A MIXTURE OF WASTE COOKING OIL AND SOYBEAN OIL

Commercial lipase Novozym 435 was used to catalyse the transesterification of a mixture of waste cooking oil and soybean oil with methanol. A central composite experimental design was performed to analyze the effects of lipase dosage, waste cooking oil content in the mixture, and reaction time on the methyl ester yield. Lipase dosage and waste cooking oil content were the most significant variables after statistical analysis. The highest yield, 98.04%, was obtained using 12.5% of lipase, a mixture containing 50% of waste cooking oil after 10 h of reaction. The lipase was reutilized and showed a good operational stability since the yield was reduced by 6% even after five batches. Two kinetic models, Power Law and Eley-Rideal, were used to model the production process and correlate the experimental results.