Ba–ZnO catalysts for soybean oil transesterification

The transesterification of soybean oil to biodiesel using Ba–ZnO as a solid catalyst was investigated. The Ba–ZnO sample with loading of 2.5 mmol/g Ba on ZnO and being calcined at 873 K for 5 h, was found to be the optimum catalyst, which could exhibit the highest basicity and the best catalytic activity for the reaction. When the transesterification reaction was carried out at reflux of methanol (338 K), with a 12:1 molar ratio of methanol to oil and a catalyst amount of 6 wt.%, the conversion of soybean oil was 95.8%. Furthermore, XRD, XPS, DTA–TG and the Hammett indicator method were employed for the catalyst characterizations, and the relation between the catalytic efficiency and the basicity of the catalysts was also discussed.