| Zeolite Beta is the only high silica zeolite with a three dimensional net work of 12 membered ring pores channel system. Owing to the unique pore structure, it exhibit some unique advantages compared with other zeolites. Compared with zeolite Y, zeolite Beta has greater modulation range for the ratios of Si/Al, so that the hydrothermal stability and adjustable acid is superior to FAU zeolite. Compared with ZSM-5, it has a larger pore size, so that it is conducive to the diffusion of larger molecules in the pores.Due to the unique topology BEA and composition, it exhibit excellent performance in terms of the hydrothermal stability, molecular shape selectivity, anti-coking and hydrophobicity, etc. As the catalyst, it can be used for low pressure hydrocracking, hydroisomerization, dewaxing, aromatization, olefin isomerization, hydrocarbon conversion and other industrial catalytic processes. However, like other zeolites, due to restrictions of micropore channels, some of the larger kinetic diameter molecules could not reach the position of the active center of the zeolite Beta, resulting in a lower utilization of the active center. On the other hand, due to the impediment of its innate small micropores, product molecules could not be spread to the outside of the hole leading to the secondary reaction even coke, seriously affecting its catalytic activity and selectivity. Not only mesoporous zeolite improve the rate of diffusion of molecules, but also has strongly acidic, high hydrothermal stability and thermal stability, etc. As a new type of catalytic materials, its design, synthesis and catalytic applications become a hot research field of catalysis.To obtain different acidic mesoporous zeolite Beta, organic silane coupling agent Y-5669 as an alkylating agent, based on silanizing of silica source in advance, mesoporous zeolite Beta with different Si/Al was prepared under hydrothermal conditions based on a " bond-blocking principle ". The silica to alumina atomic ratio in the range of 10 to∞ (pure silicalite). Under the same conditions the degree of silanization, mesoporous zeolites Beta with different Si/Al have different pore size distribution, the pore size distribution become gradually smaller with the ratio increase.In this paper, we first proposed a route for preparing mesoporous zeolite Beta with mesoporous template SX. The synthesis process was simple and mesoporous template cheap and easy to get, and explored the feasibility of a relatively low-cost method for industrial productionIn this study, the factors of crystallization time, pre-crystallization time, the type and amount of mesoporous template, water content, etc. were investigated respectively and finally the optimum conditions for preparing mesoporous zeolite Beta is determined. Material molar ratio is SiO2:0.026Al2O3:0.04Na2O: 0.26TEAOH:0.031SX:15.61H2O:0.37Alcohol, crystallization temperature was 140℃, crystallization time was 10 days. The pore diameter size of mesoporous zeolite Beta prepared mainly distributed in 4-6 nm, the total and mesoporous surface area is 801m2/g and 327m2/g respectively. In addition, by changing the content of surface active agent and water could be implemented the modulation of pore size, while changing the ratio of the zeolite micropores and mesopores. In the benzylation reaction of naphthalene, mesoporous zeolite Beta as solid acid catalysts exhibit superior catalytic performance. The main reason is that generating mesopores greatly improve the utilization of the active sites of the zeolite and the residence time of reaction product was reduced in the crystal, thereby increasing the diffusion rate of molecules.Five liters scale mesoporous zeolite Beta were completed successfully by using respectively "bond-blocking principle"and mesoporous template, which fully illustrated the feasibility of method for the production of mesoporous zeolite Beta by using both methods. |
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