Li-Ca-Zn-Al-O催化油酯醇解反应

以锂、钙、锌、铝的硝酸盐为原料，尿素为沉淀剂，采用沉淀焙烧法制备了Li-Ca-Zn-Al-O复合氧化物催化剂,采用单因素试验考察了制备条件对催化剂活性的影响。找到的制备复合氧化物催化剂的优化工艺为：元素配比n(Li):n(Ca):n(Zn):n(Al)=1:4:2:2，反应温度120 ℃，焙烧温度800 ℃，焙烧时间7 h。将优化条件下制备的Li-Ca-Zn-Al-O复合氧化物用于催化蓖麻油和甲醇的醇解反应，在n(甲醇):n(蓖麻油)=9:1，m(催化剂):m(蓖麻油)=0.04:1，搅拌速率550 r/min，反应温度65 ℃，反应时间3 h的条件下，蓖麻油转化率可达91.9%。采用Hammett指示剂法、TG、BET及XRD对复合氧化物及其前驱体进行了表征。结果显示：Li-Ca-Zn-Al-O复合氧化物的碱强度为7.2～11.2；Li-Ca-Zn-Al类水滑石在温度升至800℃时质量趋于稳定；Li-Ca-Zn-Al-O复合氧化物催化剂比表面积为25.70 m2/g、孔容为0.0477 4 cm3/g，且主要由CaO及ZnO两种晶体构成。

ALCOHOLYSIS REACTION OF VEGETABLE OIL CATALYZED BY Li-Ca-Zn-Al-O

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.