Study On The Preparation Of MCM-41 And It's Application In Esterification Reaction As Solid Superacid Catalyst

The discovery of M41S mesoporous material has attracted the world-wide attention. With large pore size and regular pore structure, M41S mesoporous materoal has great potential in the fields of catalysis and adsorption. However, the cost and the condition of synthesis limit its practical applications at a certain extent. In this article, we studied the synthesis of mesoporous molecular sieve MCM-41 at low mass fraction of surfactant. Then we prepared solid superacid using MCM-41 as carrier of the catalyst. Besides, we tried to use post-alumination method to synthesize mesoporous molecular sieve MCM-41.Mesoporous molecular sieve MCM-41 was prepared by hydrothermal crystallization reation using low mass fraction (1%~3%) of CTAB as structure template and TEOS as silica source. The structure, surface area, pore diameter, stability, appearance and composition of the sieve were observed by XRD, N2 Adsorption/Desorbtion at low temperature, TG-DTA, FT-IR, TEM. The mechanism of MCM-41 mesoporous molecular sieve was discussed as well. Moreover, influence of the process conditions was investigated. Proper process parameters were selected as follows: molar ratio of reactant n(CTAB): n(TEOS): n(NaOH): n(H2O)=1: 3.75: 1.64: 434, crystallizing at 100℃ for 72h and calcining precursor to remove template at 550℃. Thus, under the optimized conditions silica mesoporous molecular sieve MCM-41 with good crystalline structure, average pore size of 3.09nm and area(BET)= 998.022m2/g was synthesized. Low cost, simple technology were the obvious advantages of the preparation of mesoporous molecular sieve MCM-41. Moreover, the area and the pore size of the production were both bigger than them reported in some literature.Mesoporous molecular sieve MCM-41 has superiority to absorption and reaction of big molecular for it has some particular virtues. So we prepared solid superacidusing it as carrier of the catalyst. The solid superacid TiO2/S2O82- supported by mesoporous molecular sieve MCM-41 was made by the liquid-phase precipitation. Mechanism was dicussed in this paper. The esterification reaction of acetic acid and iso-amyl alcohol was selected as a grobe reaction to test the catalytic performance. The optimum conditions for preparation of the catalyst were obtained. The structure of the solid superacid was characterized by XRD, N2 Adsorption/Desorbtion at low temperature and FT-IR. The results showed that it was still mesoporous structure as MCM-41, with a high BET surface area of 211.36m2/g and it was better Lewis acid. Then we optimized the condition of the esterification reation using the solid superacid catalyst. The time of the reation was reduced greatly and yield of iso-amyl acetate was highest, that was 99.27%.Post-alumination is an efficiency method to incorporate Al atoms into the framework of mesoporous material. Compared different post-alumination methods, post-alumination methods with anhydrous AlCl3 as aluminun source and anhydrous ethanol or methanol as solvent was the best. The mesoporous samples were observed by XRD and FT-IR. The results showed that Al atoms have been imported into the framework of mesoporous molecular sieve MCM-41 successfully.