关键词: 复合氧化物, 固体碱, 催化剂, 油脂, 醇解

Abstract: Using nitrates of lithium, calcium, zinc and aluminum as raw materials, urea as precipitating agent, the Li-Ca-Zn-Al-O composite oxide catalysts were prepared by precipitation-calcination method. Effect of preparation conditions on the catalytic activity for alcoholysis is investigated by single factor experiment. The optimal conditions for preparing the optimal catalyst are: the element ratio of n(Li):n(Ca):n(Zn):n(Al) =1:4:2:2, reaction temperature of 120 ℃, calcination temperature of 800 ℃, calcination time of 7.0 h. With Li-Ca-Zn-Al-O catalyst prepared under optimal conditions, the alcoholysis reaction of castor oil and methanol was tested at the conditions of n(methanol):n(castor)=9:1, m(catalyst):m(castor oil)=0.04:1, stirring speed of 550 r/min, reaction temperature of 65 ℃, reaction time of 3 h. The castor oil conversion is 91.9%. The optimal catalyst and its precursor were characterized by Hammett indicator method, TG, BET and XRD. The results show that the base strength of Li-Ca-Zn-Al-O composite oxide is in the range of 7.2-11.2, the weight of Li-Ca-Zn-Al with hydrotalcite-like structure is invariable when the calcination temperature is above 800 ℃, proven by TG analysis. The specific surface area of the optimal catalyst is 25.70 m2/g, the pore volume is 0.047 74 cm3/g, and is mainly composed of CaO and ZnO crystals.

Key words: composite oxide, solid base, catalyst, vegetible oil, alcoholysis