Preparation of nano-solid based catalyst CaO@SiO₂ for the transesterification of soybean oil to biodiesel

The CaO@SiO₂ alkaline catalyst was prepared by sol-gel method that chooses polystyrene as hard template and P123 as soft template to control the microstructure. Furthermore, the prepared catalyst was applied to the transesterification of soybean and methanol. Also, the nano-solid based catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), CO₂-TPD and N₂ absorption-desorption (BET). The results show that the catalyst possesses an ordered morphology and core-shell structure. In addition, the effect of the ratio of SiO₂/CaO (mass ratio), reaction temperatures, catalyst dosages and the ratio of oil/methanol (mol ratio) on the yield of biodiesel was examined. Under the best reaction condition, the yield of biodiesel can reach 95.6%.