Sythesis Of Hierarchical Zeolite β

Because of its unique topology, high thermal stability, hydrothermal stability and excellent performance in catalysis, microporous zeolite has been widely applied in chemical engineering. However, pore size of conventional microporous zeolite is so small that they may face steric hindrance of reactants, especially in the catalysis involving bulky molecules in fine chemical industry. In order to expand the range of applications of microporous zeolites, hierarchical zeolites were investigated by many research groups all over the world through different routes.Hierarchical zeolite combines both the merits of mesoporous materials and microporous zeolites. These materials have been proven to be the promising catalysts that combine the advantage of shape selectivity and high efficiency of mass transfer. Moreover, some zeolites with mesoporosity have been used in a number of industrial processes including the cracking of heavy oil fraction, the production of cumene, hydro-isomerization of alkanes, and the synthesis of fine chemicals. In this dissertation, we screened several mesopore-directing agents and used nano-carbon black and bisphenol A epoxy resin as the hard mesoporous templates for the synthesis of hierarchical zeolite β and studied its mass transfer performance. The main results in this dissertation are as follows:Firstly, suitable mesoporous templates from sucrose, amylum, activated carbon, nano-carbon black, silica gel and bisphenol A epoxy resin were screened. The result suggests that nano-carbon black and bisphenol A epoxy resin are useful hard templates to approach the synthesis of hierarchical zeolite (3.Secondly, the zeolite β crystal with mesoporous pore size was synthesized by using the nano-carbon black as hard mesoporous template. The mesoporosity within zeolite corresponds well to the morphology of the nano-carbon black, which confirms the template effect of nano-carbon black. Our study also suggested that vacuum impregnation can reduce the separation of two phases, which enriches the mesoporous structure.Thirdly, hierarchical zeolite β was synthesized by hydrothermal method using epoxy-resin as mesoporous template and TEAOH as structure-directing agent under basic conditions. The results showed that the sample had rather high crystallinity and plenty of mesoporous structures were formed in the sample. The effects of synthesis conditions such as the alkalinity, water content and crystallizing time on the crystallinity and structure of hierarchical zeolite β were investigated.Finally, toluene was used as the probe molecule to study the mass transfer performance of hierarchical zeolite β. It was found that β zeolite with mesoporous structures has significantly improved in mass transfer performance compared with the conventional zeolite β. The improvement is more significantly when use bisphenol A epoxy resin as mesoporous template.