Investigation of process yield in the transesterification of coconut oil with heterogeneous calcium oxide catalyst

Abstract

The commercial success of biodiesels has to date been limited by high production costs of vegetable oil methyl esters. High feedstock costs are compounded by side reactions such as soap formation during conversion using conventional catalysts, and the consequent costs of product refining and purification. Recent studies on the heterogeneous catalysis of the transesterification reaction with commercial ion exchange resins have met with some success; the findings suggest that use of heterogeneous catalyst improves yield compared to conventional processing with homogeneous acid or alkaline catalyst. This study investigated the performance of heterogeneous calcium oxide catalyst in the production of coconut methyl ester. Specifically, the study investigated the effect of temperature, time, excess methanol and catalyst to oil ratio on conversion of oil in batch reactions as well as the level of trace calcium in the final product using a two-level factorial experimental design. The tests achieved conversion levels of 91.5 – 95.7%, based on measured TG levels of 0.6 – 1.2%. The specific gravity of the biodiesel phase was also found to be in the range of 0.83 – 0.87, which is also indicative of high conversion. Only temperature was found to have a statistically significant effect on triglyceride conversion, which implies that the overall rate of reaction is controlled by surface reaction kinetics rather than mass transfer. On the other hand, none of the experimental factors were found to have a statistically significant effect on the level of calcium contamination of the biodiesel product.