Simultaneous transesterification and esterification for biodiesel production with and without a sulphated zirconia catalyst

Simultaneous catalysed transesterification of rapeseed oil and esterification of 10 wt% myristic acid with methanol was studied using sulphated zirconia and in the absence of catalyst. The maximum total FAME content of 86% was obtained at a catalyst loading of 3 wt%, temperature of 170 degrees C, pressure of 22 bars, molar ratio of oil to methanol of 1: 20 and stirring rate of 600 rpm for 60 min. At these conditions, FFA was observed to reach 2.95% (2.94 mg/ml sol.). Thermo/catalytic cracking and hydrolysis of triglyceride was presumed to form the FFA. Water was also formed: dehydration of methanol is likely to be the principal source. Three sets of main reactions occurred at distinctly different rates. Esterification of myristic acid was the most rapid reaction. Direct transesterification of triglyceride and side-reactions of thermo/catalytic cracking of triglyceride followed by esterification of fatty acid and hydrolysis of triglyceride followed by esterification of fatty acid occurred afterward. Dehydration of methanol was observed throughout the reaction, producing a constant supply of water, thereby facilitating hydrolysis reactions. (C) 2012 Elsevier Ltd. All rights reserved.