文献类型：期刊文献

英文题名：Roles of ethanol and Si-OH in the aldol condensation of ethyl acetate over a Cs/SBA-15 catalyst

作者：Tian, Xiang[1];Tian, Hengshui[1]

机构：[1]East China Univ Sci & Technol, Coll Chem Engn, Shanghai 200237, Peoples R China

年份：2021

卷号：6

期号：6

起止页码：1002

外文期刊名：REACTION CHEMISTRY & ENGINEERING

收录：;EI(收录号：20212310461253);WOS:【SCI-EXPANDED(收录号:WOS:000638255000001)】；

语种：英文

外文关键词：Electronegativity - Ethanol - Ascorbic acid - Catalyst activity - Molar ratio - Chemical bonds - Ketones - Condensation - Condensation reactions - Silicon compounds

摘要：Alkali and alkaline earth metal-supported mesoporous SBA-15 catalysts via impregnation were characterized and tested in the vapor phase aldol condensation of ethyl acetate and formaldehyde in ethanol to synthesize ethyl acrylate (EA) and acrylic acid (AA). Ethanol dehydrogenation exerts a negative effect on the main reaction, and Lewis acid sites donated by either gust or support prefer forming acetaldehyde to compete for formaldehyde with the main aldol condensation. Combined with the good dispersion of active sites and acceptable diffusion conditions, the pairs of weak acidity and weak-medium basicity enable 5Cs/SBA-15 to achieve the highest yield of 63% for acrylic products based on formaldehyde. Aliphatics are confirmed as the main compositions of coke depositions to lead the deactivation of cesium-modified catalysts whose activity could be regenerated completely by calcination. According to experimental and DFT results, Si-OH assisting Si-O-Cs plays the role of accelerating the enol structure formation by decreasing the activation barrier, and performs the necessary favor for the cleavage of ethanol hydroxyl by reducing the electronegativity of ethanol oxygen. The predominant pathway for producing AA is also confirmed through EA hydrolysis, and the relatively strong adsorption energy of EA should account for the high AA/EA molar ratio.