SnO_2-Al_2O_3固体酸催化大豆油酯交换制备生物柴油

Biodiesel preparation from transesterification of soybean oil by solid acid SnO_2-Al_2O_3 catalyst

采用共沉淀法制备SnO_2-Al_2O_3复合固体酸催化剂,用于催化大豆油甲醇解反应,考察催化剂制备条件和酯交换反应条件对大豆油转化率影响。研究结果表明,催化剂最佳制备条件为Sn/Al摩尔比3:1,煅烧温度为923K;催化大豆油酯交换反应醇油摩尔比30:1,催化剂用量3 wt%,反应时间5 h,反应温度200℃,此时大豆油转化率最高,为75.05%。当向酯交换反应体系加入一定量游离脂肪酸或水分时,SnO_2-Al_2O_3催化剂催化活性几乎不受影响,且还能同时催化酯化反应;结果还表明,固体酸SnO_2-Al_2O_3具有很好稳定性,可多次重复利用。

Transesterification of soybean oil with methanol to prepare biodiesel with solid acid SnO2-Al2O3 as the catalyst was studied. The catalyst was prepared by coprecipitation and had a high catalytic activity. Effect of conditions on the catalyst preparation and the transesterification reaction was investigated. The experimental results showed that the optimum conditions of the catalyst preparation were that the Sn/Al mole ratio was 3 ： 1, the calcination temperature and the calcination time were 923K and 4h respectively. Also, the suitable conditions of transesterification were obtained. When the mole ratio of methanol to oil was 30 ： 1, the loading of the catalyst SnO2-Al2O3 was 3% of the oil weight, and the reaction temperature and the reaction time were 200℃ and 5h respectively, the conversion of the soybean oil was highest, up to 75.05%. When a certain amount of free fatty acids and water was added into the transesterification reaction system, the catalytic activity of SnO2-Al2O3 catalyst was not affected significantly. The obtained result also showed that the solid acid had a high stability and activity and could be recycled for several times.