Synthesis And Catalytic Performace Of Composite Molecular Sieve With Mesoporous And Microporous Structure

As compared with microporous zeolites, MCM-41 possesses a regular hexagonal array of ordered mesoporous channels with pore diameters in the region of 1.5 to 10nm. Consequently, MCM-41 has been considered as a very interesting material in the field of petroleum chemistry and fine chemistry. However, these mesostructured materials have relatively low hydrothermal stability, which severely hinders their practical applications. Researchers discovered that minicrystal-incorporation approach can successfully improve hydrothermal stability of MCM-41. Aimed at this object, it is mainly researched in this paper.In this paper, Y/MCM-41 was synthesized by a two-step crystallization process. Firstly, the solid-liquid mixture of Y was synthesized; then the template and Na2SiO3 were added to the mixture, and H2SO4 was used to adjust PH. The effects of use level of materials, temperature and crystallization time on the synthesized products were investigated. The results have demonstrated that Y/MCM-41 can be successfully synthesized by a two-step crystallization process. The adding Order of materials affectedpoorly Y/MCM-41, but use level of materials affected severely Y/MCM-41 and different use level of Na2SiO3 can synthesize Y/MCM-41 that had different relative content of mesoporous molecular sieve and microporous molecular sieve. In the first step, along with crystallization time increasing, the content of MCM-41 in Y/MCM-41 increased. In the second step, the optimal condition was that the homogeneous solution crystallized 1 day in 130 ℃.Physicochemical properties of Y/MCM-41 were characterized by XRD, SEM and BET methods. The results have shown that Y/MCM-41 possessed simultaneously characteristic peak of Y and MCM-41 and crystal shape of Y/MCM-41 was different from that of Y and MCM-41. The N2 adsorption-desorption isotherm of Y/MCM-41 exhibited only a typical reversible type isotherm. According to desorption isotherm, the pore size of Y/MCM-41 was calculated. The results indicated pore size distribution lied in microporous and mesoporous region.Alkylation of phenol was used to research catalytic activity of Y/MCM-41. The results have shown that Y/MCM-41 has higher catalytic activity than the traditional Y and MCM-41. For the Y/MCM-41(D), not only the conversion of phenol raised with tert-butyl alcohol and reaction temperature raising, but also Useful time of Y/MCM-41(D) was longer. For the Y/MCM-41 (A), the conversion of phenol raised with reaction time raising, But that increased slowly after 3 hours.