| Calcium magnesium hydroxide precipitate was prepared with sodium hydroxide, calcium nitrate and magnesium nitrate. Aluminum hydroxide precipitate was prepared with ammonia and aluminum acetate. Then calcium magnesium aluminum solid base catalyst was made by mixing and calcinating the two kinds of precipitates in turn by aging, suction filtration, washing and drying. The effects of catalyst preparation conditions on the catalytic activity were investigated by orthogonal experiment, with methanolysis reaction of castor oil as model reaction and castor oil conversion rate as the activity evaluation index. The catalyst and its precursor were characterized by Hammett indicator method, TG, XRD, BET and SEM. The results showed that the optimal preparation conditions of the catalyst were obtained as follows: n(Ca)∶?n(Mg)∶?n(Al)=1.5∶?1.5∶1, aging time 18 h, calcination temperature 400?℃ and calcination time 6 h. Under these conditions, the corresponding castor oil conversion rate was up to 88.3% with stable catalytic activity. The catalyst precursor had a significant mass loss step at 300-400?℃, and the mass did not change with temperature above 800?℃. The alkali strength of the solid base catalyst was 7.2-15.0, and the total alkali amount was 12262 mmol/g. It was mainly composed of CaO and MgO crystals, and the specific surface area, pore volume and particle size were 8383 m2/g, 0173 2 cm3/g and 2-20 μm. |
