Synthesis and characterization of acidic ordered mesoporous organosilica SBA-15: Application to the hydrolysis of cellobiose and insight into the stability of the acidic functions
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- 作者：Mariam Karaki ; Ali Karout ; Joumana Toufaily ; Franck Rataboul ; Nadine Essayem ; B¨¦n¨¦dicte Lebeau
- 关键词：Sulfonated periodic mesoporous organosilicas ; Cellobiose hydrolysis ; Isopropanol dehydration ; Solid hybrid acid catalysts ; Water-tolerant solid acids
- 刊名：Journal of Catalysis
- 出版年：2013
- 出版时间：September, 2013
- 年：2013
- 卷：305
- 期：Complete
- 页码：204-216
- 全文大小：1812 K
文摘
The present work aimed to investigate the potential of acidic ordered mesoporous organosilica SBA-15 with a controlled local environment of the acid sites for applications in acid-catalyzed reactions in hot water, such as cellobiose hydrolysis. The hybrid silica was prepared by condensation of 1,4-bis(triethoxysilyl)benzene. The material was sulfonated using chlorosulfonic acid or 3-mercaptopropyltrimethoxysilane and further oxidized with H2O2 to give Br?nsted solid acids, which were fully characterized. Their acidic properties were studied by calorimetry of NH3 adsorption and in the model reaction of gas-phase isopropanol dehydration and compared with the reference acidic sulfonated resin, Amberlyst 15. The introduction of mercaptopropyl organic arms, oxidized by H2O2, did not change the structure of the material, while sulfonation with chlorosulfonic acid led to a less organized solid. In both cases, calorimetry of NH3 adsorption has evidenced the heterogeneity of the acid strength distribution, suggesting the presence of distinct sites of sulfonation, contrary to our expectation. This was supported by XPS analysis. For gas-phase isopropanol dehydration, the solids sulfonated with chlorosulfonic acid exhibited activity equivalent to that of the sulfonated resin, Amberlyst 15, but were less stable due to sulfur species release, assumed to be sulfonated silanols. The acidic organosilicas SBA-15 obtained via H2O2 oxidation of the mercaptopropyl group are less acidic catalysts, showing low activity for gas-phase isopropanol dehydration. However, no sulfur release was observed. The hybrid solid acids were evaluated in a reaction of great interest in the context of the biomass valorization: cellobiose hydrolysis in hot water. The solids were active at 150 ¡ãC; however, sulfur leaching analysis showed that the reaction proceeds mainly homogeneously, especially for the material acidified with chlorosulfonic acid. A hot washing pretreatment applied to the catalysts containing the sulfonated propyl groups led to a decrease in their hydrolysis activity, but along with an increase in stability, allowing recycling.