固体超强酸SO_4~(2-)/SnO_2-SiO_2催化制备生物柴油的研究

以固体超强酸SO_4~(2-)/SnO_2-SiO_2为催化剂催化大豆油和甲醇的酯交换反应制备生物柴油,考察了催化剂的制备条件和反应的最佳条件.结果表明,当催化剂的Sn/Si摩尔比达1/3以上.浸渍硫酸溶液的浓度为1.0～1.5 mol/L,450℃焙烧5 h,该催化剂对酯交换反应有很高的催化活性.在醇油摩尔比为13:1、每摩尔油使用1.0 g催化剂、120℃反应3 h,脂肪酸甲酯的收率达90%以上.催化剂具有L酸中心和B酸中心,具有超强酸性.反应体系的水抑制催化剂的活性,但催化剂的活性不受体系中游离脂肪酸的影响,这意味着催化剂能高效催化那些未精炼原油和那些不可食用的油料,使酯化和酯交换一步完成.

Preparation of biodiesel with the catalysis of solid suoeracid SO_4~(2-)/SnO_2-SiO_2

SO_4~(2-)/SnO_2-SiO_2,a solid superacid catalyst,is prepared and used to produce biodiesel through transesterifieation of soybean oil with methanol.The factors affecting catalyst preparation and biodiesel production are investigated.It's found that SO_4~(2-)/SnO_2-SiO_2 exhibites high activity for transesterification under the conditions of Sn/Si molar ratio higher than 1/3,the concentration of impregnating sulfuric acid solution of 1.0-1.5 mol/L,and calcination temperature of 450℃.The yield of methylesters can reach over 90%under the conditions of 120℃,methanol/oil molar ratio of 13:1,reaction time period of 3 hours and 1.0 g of catalyst per mol oil.The catalyst shows Lewis and Bronsted acid centers on itself,and it has superacidity.The activity of the catalyst can be strongly reduced by the presence of water.But the catalytic activity can not be affected by fatty acid.This means a variety of unrefined crude oils and non-edible oils might be transesterificated over the catalyst with high efficiency.With the catalyst both the esterification and trenesterifieation can be conducted in a single operation.