A Novel Class of Solid Base Catalysts in Transesterification of Vegetable Oils with Methanol

Biodiesel has become more and more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. Traditional biodiesel production process generally employs homogeneous strong base as catalysts such as NaOH, KOH. The disadvantage of such catalysts is that the waste catalysts are difficult to be removed after reaction, which cause a high separation cost and a product purification cost. Heterogeneous catalysts can be easily separated from reaction mixture and reused for many times. Therefore, there is an increasing interest from both industry and academic in developing heterogeneous catalysts for biodiesel production. Many calcium oxide based catalysts show a high activity in oil and methanol transesterification at low temperature. However, most of them suffer from catalyst leaching which caused deactivation and homogeneous problem. In this study, modification of calcium-based catalyst decreased the solubility in reaction mixture and prolongs catalyst life. XRD, XPS, BET, FTIR, SEM, EDS, and Hammett indicator method were used to characterize the structure of catalysts and the nature of active sites. X-ray phases of this catalyst are CaO and CaS. It was found that there was a strong interaction between calcium species and support which makes catalyst structure stable in reaction conditions. However, the modified catalyst has a lower basicity and base strength than unmodified catalyst, which caused a slight decrease in catalyst activity.