Effects of preparative parameters on the structure and performance of Ca–La metal oxide catalysts for oil transesterification

The effects of preparative parameters on the surface basicity, composition, and transesterification activities of several Ca–La metal oxide catalysts were investigated. Four different preparation methods: ammonia–ethanol–carbon dioxide precipitation, physical mixing, impregnation, and co-precipitation, were studied. It was found that the ammonia–ethanol–carbon dioxide precipitation method resulted in the highest BET specific surface area, base strength and base site concentration. Moreover, catalyst surface composition and basicity are a function of calcination temperature, precipitants, pH, and molar ratio of Ca to La in precursor solution, and storage conditions. XRD, XPS, basicity and BET tests revealed that catalyst structure and dispersion of Ca species strongly influenced the catalyst activity. High surface concentration of Ca species, strong base strength and high concentration of base sites, and high specific surface area are characteristics of an active transesterification catalyst.

A sequential precipitation method with ammonia solution, ethanol and carbon dioxide as precipitants for solid base catalyst preparation has been developed. A cooperative effect among the precipitants contributes to a high BET specific surface area, base strength and base site concentration. The catalyst shows a higher catalytic activity in oil transesterification than those prepared by physical mixing, impregnation and co-precipitation methods.Figure optionsDownload high-quality image (137 K)Download as PowerPoint slide