Preparation And Performance Evaluation Of Ultra-large Mesoporous Solid Acid Catalysts

Microporous zeolite solid acids have narrow channels less than 2 nm. The aperture of traditional mesoporous solid acids are smaller than 20 nm. For macromolecule involved reactions, large molecules can not enter into small holes. Therefore, they cannot contact the inner active sites of the catalysts, and may lead to inefficient catalytic performance. Above all, it is important to develop a solid acid catalyst with bigger pore sizes. This work focused on the preparation of larger mesoporous solid acid catalysts and their applications in the macromolecular reactions.Mesostructured cellular silica foam has a largest aperture in silica-based mesoporous materials. It has three-dimensional channels and good hydrothermal stability. The pore size could be adjusted from 20 to 50 nm. Thus, two types of solid acid catalysts were prepared in this work, namely, organic-inorganic silica foam solid acid and ZSM-5 composed foam composite solid acid.Organic-inorganic silica foams were prepared using three block copolymer P123 and 1,3,5-trimethyl benzene as templates, and 1,4-bis(triethoxy silicon) benzene as silicon source. Then organic-inorganic silica foam solid acid catalysts, namely, OSMCF-0.75-SO3H and OSMCF-1.00-SO3H, were successfully prepared by sulfonating benzene ring of foam skeleton. TEM, SEM and N2 adsorption results proved that the catalysts had three-dimensional porous structures and the pore sizes ranged from 28 to 50 nm. In addition, FT-IR, chemical titration and TG-DTG results showed that sulfonic acid groups were successfully grafted onto the benzene rings, and the acidic content was 0.778 mmol/g and 0.952 mmol/g, respectively. Both catalysts have good thermal stability at 600 ?. Then, the catalysts were applied to the cellulose hydrolysis reaction at 120·? for 1.5 h as the weight ratio of catalyst to cellulose was 0.3, the reducing sugar yield reached a highest value of 58.9% and 62.1%, respectively. The corresponding TOF values were 14.78 h-1 and 11.46 h-1. The catalysts can be reused as well.Aluminum containing silica was prepared using P123 and 1,3,5-methyl benzene as templates, tetraethyl orthosilicate as silicon source and sodium aluminate as aluminum source. Then the H-ZSM-5/MCF composite solid acid was successfully prepared by impregnating with TPAOH and gas-phase crystallization. TEM, SEM and N2 adsorption proved that the porous structure of the form was remained. The mesoporous apertures were-27.1 nm, microporous apertures were ?0.56 nm. Pyridine infrared adsorption and TG-DTG showed that the catalyst contained B and L acid. H-ZSM-5/MCF had good thermal stability. It was applied to the esterification of oleic acid and methanol reaction at 100 ? for 6 h. When the weight of catalyst was 0.4 g, the conversion of oleic acid reached a maximum of 48%. However, the commercial HZSM-5 without mesoporous structures had merely 28%. Therefore, H-ZSM-5/MCF are promising to be applied to some reactions of macromolecular.