Preparation And Application Of Hybrid Solid Acid

The solid acid catalyst is one of the most widely used acid catalysts, which has manyadvantages of high selectivity; fewer by-products and easy separation of products. Besides,there is no corrosion to equipment and eco-friendly. But there are some disadvantages: poormechanical strength and stability, smaller pore size, shorter life, higher costs, etc. In this paper,in order to solve the shortcomings, four kinds of silica with different porous size were used ascarrier and the pore as micro-reactor. The carrier was modified physically or chemically firstand the organic styrene-based sulfonic solid acid was formed in the silica bore. Theconcentration of coupling agent and monomer, polymerization and sulfonation temperature,the amount of sulfonation agent, sulphonation time were investigated, which could influencethe catalysts. The main contents are as follows:1.modification physically: the styrene polymerization reaction with AIBN occurred at80℃for10h, and then it was sulfonated at150℃for5h.2.modification chemically: we employed VTEOS as modifier in order to interact withSi-OH(at50℃for24h), and then it would react with styrene (at80℃for10h), finally thesulfonation reaction was carried out under concentrated sulfuric acid at150℃for5h.BET, IR, SEM, TG-TGA, and element analysis were employed for structuralcharacterization. Meanwhile, Py-IR and acid-base titration were used for acid characterization.BET results showed that the aperture and the surface area were lower than before. Elementanalysis indicated that the content of C, H, S significantly increased compared with the carrier.There were peaks of benzene ring and sulfonate in the IR spectrum. The gap between smallsilicon spheres was smaller after modification and the silicon balls adhered each other fromSEM. TG and TGA curves told us the solid acid substantial weight loss occurred above200℃,which explained the better stability of the solid acid. As measured by Py-IR and chemical titration, the solid acid catalyst had not only Bronsted acid but Lewis acid. The acid amount ofchemically modified solid acid (5.54mmol/g) was better and higher than physicalmodification, which was obviously higher than732sulfonic acid resin (1.52mmol/g).In order to detect the catalytic activity and stability of the solid acid, synthesis of ethylacetate was taken as an example in the batch reactor and fixed bed reactor and the influence tothe ester yield were studied. Results demonstrated that the yield of product was more than85%. The catalyst could be used more than13times, whose life is up to40h for continuoususe. The results showed that the solid acid catalyst had efficient catalytic activity and longerlife. Besides, the reason of inactivation was concluded. And the factor might consist of thedestruction of the catalyst skeleton, the loss of active ingredient, conversion from sulfonicacid to sulfonate.