4. Conclusions
A highly efficient solid basic catalyst for biodiesel production from soybean oil with methanol was prepared by a facile method of thermally treating carbide slag waste. The influences of various factors, e.g. calcination temperature for the raw carbide slag, reaction temperature, methanol/oil molar ratio, catalyst dosage, and reaction time, on the biodiesel synthesis were systematically studied. As a result, 91.3% FAME yield could be achieved within a short reaction time of 30 min, which was corresponding to 182.6 gFAME gcat− 1 h− 1. This superior catalytic activity is among the best results obtained over Ca-based catalysts. It was found that the appropriate calcination temperature was crucial for obtaining higher catalytic activity. Moreover, the relationship between the structure and activity demonstrated that the strong basicity on the catalyst surface was responsible for the high catalytic activity. Thus, this work has provided an easily available and effective catalyst derived from waste carbide slag to synthesize sustainable energy product of biodiesel, which also has great significance in effective utilization of waste resource and environmental protection.