Waste limescale derived recyclable catalyst and soybean dregs oil for biodiesel production: Analysis and optimization

The focus of this work is to develop a reusable heterogeneous catalyst for the preparation of biodiesel. Among the potential raw materials, soybean dregs oil is extracted from waste soybean dregs, and limescale is used as a source of calcium oxide. The basic catalyst of mixed metal oxide of CaO and Al2O3 was synthesized by sol-gel method. The structure, composition and basicity of the synthesis catalyst were characterized by TG, XRD, BET, SEM-EDX, TEM-EDX, FTIR and CO2-TPD. The results indicate that the presence of the inert substance Ca5Al6O14 inhibits the accumulation of CaO and promotes its dispersion uniform. The FAEE yield reaches 92.6 % under the optimized conditions. Kinetic analysis shows that the experimental pattern conforms to a pseudo-first-order reaction kinetic model (R2 = 0.9674), and the activation energy required for the transesterification reaction is Ea = 62.36 KJ/mol. In addition, the catalyst shows high stability in this experiment, and no obvious performance loss is observed during the process of five cycles.