Synthesis of biodiesel over ZnO/Ca(OH)_2/KF catalyst prepared by the grinding method

摘要

Anovel ZnO/Ca(OH)_2/KF solid base catalyst was prepared by the grinding method and applied to biodiesel synthesis by the transesterification of soybean oil. The effect of various parameters such as KF molar amount, calcination temperature, the amount of catalyst, molar ratio of methanol to oil, reaction temperature, and time on the activity of the catalyst were investigated. The catalysts were characterized by several techniques of thermogravimetry/derivative thermogravimetry, X-ray diffraction, Hammett indicator method, and scanning electron microscopy. The analysis results indicated that the KF interacted with Ca(OH)_2 and formed KCaF_3 phase before calcination of the catalyst. The formed KCaF_3 crystal phase was the main catalytic active component for the catalyst activity. In addition, the basicity of ZnO/Ca(OH)_2/KF was greatly influenced by the different calcination temperates, and the catalyst activity was correlated closely with the basicity.Adesired biodiesel yield of 97.6 %was obtained at catalyst amount of 3 %, methanol/oil of 12:1, and reaction time of 1.5 h at 65 ℃.