The Role of Brønsted and Lewis Acid Sites in Acetalization of Glycerol over Modified Mesoporous Cellular Foams

详细信息    查看全文

• 作者：Katarzyna Stawicka ; Alba E. Díaz-Álvarez ; Vanesa Calvino-Casilda ; Maciej Trejda ; Miguel A. Bañares ; Maria Ziolek
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：August 4, 2016
• 年：2016
• 卷：120
• 期：30
• 页码：16699-16711
• 全文大小：810K
• 年卷期：0
• ISSN：1932-7455

文摘

The main objective of this work is to determine which kind of acidic sites, Brønsted (BAS) or Lewis (LAS), are more active and stable in the glycerol acetalization to solketal by means of Raman-monitoring. For this purpose, the mesoporous cellular foams (MCFs) were modified to obtain materials containing exclusively BAS occurring in different number and strength (samples MP-MCF (MP = (3-mercaptopropyl)trimethoxysilane) and CS-MCF (CS = 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane)) or the material containing exclusively LAS (NbMCF). Moreover, the materials containing both types of centers in different ratios (MoMCF and TaMCF) were also studied. Real-time Raman monitoring of the catalytic reaction allowed us to observe not only changes in substrates concentration and product yield but also the transformation of acetone–glycerol adduct (O···C═O vibrations) formed in the presence of a catalyst. The activity of the catalysts containing BAS depends on the number and strength of these centers, and the best performance was observed for CS-MCF. The maximum of solketal yield and the equilibrium state were achieved after 2 min from the start of the Raman monitoring. NbMCF containing exclusively LAS exhibited both the lowest conversion of glycerol and stability. The role of different recycling treatments was probed.