| The precipitates of calcium, magnesium, zinc carbonate and aluminum hydroxide were prepared by coprecipitation with calcium nitrate, zinc nitrate, magnesium acetate and aluminum acetate as raw materials and sodium carbonate as precipitation agent, and then the calcium magnesium zinc aluminum solid base catalyst was prepared by the aging, washing, drying and calcination. The effects of preparation conditions on the catalytic activity were investigated by orthogonal experiment, with castor oil conversion rate in methanolysis reaction of castor oil as the activity evaluation index. The optimal conditions for the preparation of the catalyst were obtained as follows: n(Ca)∶?n(Mg)∶?n(Zn)∶?n(Al)=2∶?0.5∶?0.5∶?1, pH of the mixed solution 8, calcination temperature 850?℃, and calcination time 7 h. With the solid base obtained under these conditions as catalyst in methanolysis reaction of castor oil, the castor oil conversion rate was up to 93.2%. The catalyst and its precursor were characterized by thermogravimetric analysis, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy and Hammett indicator method. The results showed that the catalyst precursor had a significant weight loss step in the temperature range of 700-800?℃, and the mass did not change with temperature above 800?℃.The solid base catalyst was mainly constituted of three kinds of crystals CaO, ZnO and MgO. The specific surface area and pore volume of the catalyst were 44.08 m2/g and 0.062 65 cm3/g respectively, and it was porous continuous honeycomb structure. The alkali strength of the solid base catalyst was between 7.2 and 15.0, and the total alkali amount was 14.895 mmol/g. |
