Au/Sn-deAl-β的制备及其催化甘油氧化酯化的性能研究

Preparation of Au/Sn-deAl-βand its catalytic performance for oxidative esterification of glycerol to methyl lactate

以SnCl_(4)接枝的脱铝β分子筛(Sn-deAl-β)为载体,采用沉积-沉淀(DP)法制备了不同Au质量分数的Au/Sn-deAl-β催化剂;利用XRD、XRF、N_(2)物理吸附和NH_(3)-TPD对Au/Sn-deAl-β进行表征,并考察了催化剂制备方法、组成、结构和反应条件对甘油氧化酯化制备乳酸甲酯性能的影响。结果表明,Si/Al摩尔比为510、Au理论质量分数为1%且DP过程中pH为9.00的条件下制备的Au/Sn-deAl-β催化剂具有最高的乳酸甲酯选择性;Au/Sn-deAl-β催化剂兼具氧化脱氢位点和Lewis酸中心,能够高选择性地实现甘油氧化酯化制备乳酸甲酯。此外,甘油氧化酯化的产物与Au颗粒尺寸和催化剂酸性密切相关,小尺寸的Au颗粒相对有利于甘油酸甲酯和乙醇酸甲酯的生成。

Sn-deAl-βis prepared by grafting SnCl_(4)onto the dealuminated Hβzeolite,and used as a carrier to load Au via a deposition-precipitation(DP)method to obtain Au/Sn-deAl-βcatalysts,which are characterized by means of XRD,XRF,N_(2)physical adsorption,and NH_(3)-TPD.The effects of composition,preparation process and structure of catalysts,as well as reaction conditions on the performance of Au/Sn-deAl-βcatalysts are investigated in the oxidative esterification of glycerin to methyl lactate.The results indicate that Au/Sn-deAl-βcatalyst,with a Si/Al molar ratio of 510,a theoretical Au loading of 1 wt%,and prepared at a controlled pH value of 9.00 in the DP process,delivers the highest selectivity of methyl lactate.Au/Sn-deAl-βcatalysts have both oxidative dehydrogenation sites and Lewis acid centers,which can convert efficiently glycerin to methyl lactate.In addition,the products from oxidative esterification of glycerin are closely related to the acidity of catalyst and the size of Au particles.The preferred selectivity of methyl glycerate and methyl glycolate can be obtained over the catalyst with smaller Au particles.