Wollastonite decorated with calcium oxide as heterogeneous transesterification catalyst for biodiesel production: Optimized by response surface methodology

CaO is efficient in catalyzing transesterification for biodiesel production , but its industrial application is inherently restricted by active sites leaching. To address this drawback, CaO is decorated into wollastonite to prepare the stable Ca/wollastonite catalyst. Microwave-assisted transesterification is used to produce biodiesel from palm oil, which effectively accelerates the reaction rate and improves the conversion efficiency. The Ca/wollastonite-0.8 catalyst with the mass ratio of CaO to wollastonite of 0.8 performs well with the fatty acid methyl ester (FAME) yield of 97.59%. Also, this catalyst is highly stable, where the FAME yield of 87.30% could be obtained for the fifth reused cycle. CaO is evenly dispersed on the wollastonite surface and the total basicity is high to 0.281 mmol g −1 . Meanwhile, transesterification parameters are optimized by response surface methodology with central composite design (RSM-CCD) and the maximum FAME yield of 98.46% is achieved at reaction temperature of 64.2 °C, molar ratio of methanol to palm oil of 15.54 and mass ratio of catalyst to palm oil of 9.21  wt % for 3 h. Besides, the mass ratio of catalyst to palm oil is the primary variable. Wollastonite is demonstrated to be feasible to enhance the stability of CaO in catalyzing transesterification.