Heterogeneous catalytic transesterification for biodiesel production: Feedstock properties, catalysts and process parameters

In recent years, biodiesel has attracted increasing interest as a substitute for fossil fuels. However, the cost of producing biodiesel is far greater than that of fossil fuels. As a means of reducing the cost of production, biodiesel has been produced from different kinds of feedstock based on local availability. Howbeit, the quality and efficiency of the transesterification process have been limited by the feedstock quality. It has been documented that the quality of biodiesel produced depends on the fatty acid compositions and the physicochemical properties of the oil feedstock. Moreover, the use of heterogeneous catalysts in the trans-esterification process has been preferred due to their reusability, and ease of product separation. Different kinds of solid-based catalysts influence the yield of the biodiesel produced, this was based on the distinct basicity and textural properties of the catalyst used. Hence, researchers have sought to improve the trans-esterification reaction by altering the basicity, surface area, and porosity of the catalyst. In addition, trans-esterification process parameters such as methanol: oil ratio, catalyst loadings, reaction time, reaction temperature, stirring rate, and ultrasonic irradiation influences the catalytic transesterification reaction. Therefore, this review considers the effect of oil feedstock properties, the heterogeneous catalytic properties, and transesterification process parameters as it affects the transesterification process. It also considers the mechanism of the transesterification reaction and discusses the challenges and areas that require improvement.