SnO2负载硅钨酸催化制备月桂酸单甘酯

以金属氧化物、硅钨酸为原料,采用浸渍法合成了系列金属氧化物负载硅钨酸催化剂。通过FTIR、XRD、TGA-DTG、BET及固态~(31)P MAS NMR表征技术对催化剂的结构、热稳定性、表面形貌及酸性进行了表征与测试。考察了该系列催化剂在月桂酸单甘酯(GML)制备中的催化性能。结果表明,20HSiW/SnO_2〔即20%H_4SiW_(12)O_(40)/SnO_2,20%表示硅钨酸的含量(以H_4SiW_(12)O_(40)和Sn O_2总质量为基准,下同),缩写为20HSiW/SnO_2,下同〕催化剂显示出较好的催化性能,这归因于较强的Br?nsted酸性及硅钨酸(Br?nsted)与载体(Lewis)间的酸性协同效应。以20HSiW/SnO_2为催化剂,在n(甘油)∶n(月桂酸)=5∶1、20HSi W/SnO_2催化剂用量为月桂酸质量的7%、反应时间3 h、反应温度423 K条件下,月桂酸转化率为91.4%,GML产率为78.9%;20HSiW/SnO_2催化剂显示出较好的重复使用性能,经5次循环利用后,GML的产率为73.6%;动力学研究表明,20HSi W/Sn O_2催化制备GML反应活化能为33.02 kJ/mol。

Preparation of Monoglyceride Laurate Catalyzed by Silicotungstic Acid Supported on SnO2

A series of metal oxide supported silicotungstic acid catalysts have been successfully synthesized through impregnation method. The catalysts so fabricated of the structure, stability and acidity were characterized by various physicochemical techniques such as FTIR, XRD, TGA-DTG, BET, and 31P MAS NMR and their catalytic performances during the preparation of monoglyceride laurate (GML) were assessed. The results showed that 20HSiW/SnO2 catalyst exhibited the superior catalytic performance in the preparation of GML owing to strong Br?nsted acidity and Br?nsted-Lewis acid synergy for supported catalyst. A maximum GML yield of 78.9% was achieved for the 20HSiW/SnO2 catalyst under the optimal conditions: molar ratio of glycerol (GL) to lauric acid (LA) was 5:1, the mass fraction of 20HSiW/SnO2 catalyst was 7% (based on LA), the reaction time was 3 h, and the reaction temperature was 423 K. The yield of GML could still reach 73.6% after 20HSiW/SnO2 catalyst was reused 5 times, indicating that this catalyst had excellent durability. Further kinetic studies confirmed that the esterification of GL with LA to GML with an activation energy of 33.02 kJ/mol.