Preparation of a palygorskite supported KF/CaO catalyst and its application for biodiesel production via transesterification

This study aimed to explore base catalysts with high transesterification efficiencies to be used for heterogeneous biodiesel production. Palygorskite, a promising low-cost clay mineral, served as a support for KF/CaO to prepare a base catalyst. The base catalyst was prepared via a facile impregnation method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and N-2 adsorption. Subsequently, the prepared catalyst was used for producing biodiesel via the transesterification of commercial soybean oil with methanol. The effects of the catalyst preparation conditions as well as the transesterification parameters, such as the loading amount of KF, calcination temperature, catalyst amount, methanol to oil molar ratio, reaction temperature and water content, on the biodiesel yield were investigated. Results showed that the metal oxide species dispersed on the surface of palygorskite, and the formed KCaF3 was the main active component for the activity of the catalyst. A maximum biodiesel yield of 97.9% was obtained under the optimal conditions. The separated catalyst could be directly used in the next round of reactions and gave a satisfactory yield. The biodiesel yields decreased from 97.9% to 91.3% from the first to the tenth use of the catalyst particles.