Catalytic Properties Of Mesoporous Zeolite Materials

Nowadays, porous materials are of interest for catalysis, adsorption, separation and other applications. Zeolites as solid acid catalysts have been widely used in industry as heterogeneous catalysts, However, relatively small and sole micropores in zeolites strongly influence the mass transport, which severely limit their performance of industrial catalysts. Ordered mesoporous aluminosilicates were synthesized to solve the diffusion limitation of microporous zeolites. But these mesoporous aluminosilicates exhibited lower hydrothermal stability, weaker acidity, and lower catalytic activities than microporous zeolites which was attributed to their amorphous framework, which limited the performance of mesoporous aluminosilicates in catalytic field.To overcome these limitations, various methods such as synthesis of nanosized zeolites, invention of various ultralarge-pore zeolites and ordered mesoporous materials with higher hydrothermal stability had been successfully pursued. To change the amorphous walls of mesoporous materials, a series of ordered mesoporous aluminosilicates were synthesized by assembly of preformed nanosized zeolite precursors as aluminosilicate sources with surfactant micelle. Compared with conventional zeolites, the hydrothermal stability of these mesoporous aluminosilicates was still low, which was attributed to the semi-crystallized mesoporous walls. Some efforts have been devoted to the development of mesoporous zeolites, with the aim of combining the advantages of the high acidity and high hydrothermal stability of the crystalline zeolite and the facile diffusion of bulky molecules in mesoporous materials.Mesoporous zeolite materials, which are defined as the zeolite crystalline materials containing a large amount of mesopores, not only inherit excellent acidity and hydrothermal stability, but also improve the adsorption and diffusion of large molecules. Mesoporous zeolite materials have much effective and potential applications in catalysis, especially catalytic reaction over large molecules.Recently, mesoporous zeolites from carbon templates had been successfully synthesized, but their applications are still limited by the complexity of synthetic procedure and hydrophobicity of carbon templates.The aims of the present paper are: to develop facile, low cost and efficient routes to novel mesoporous zeolites. To characterize the structure and properties of mesoporous zeolites. To analyze the interaction factors during the synthetic system. To investigate the applicability of mesoporous zeolites to catalysis.We demonstrate here a unique, facile, controllable, and universal route for the synthesis of mesoporous zeolites. More importantly, these novel mesoporous zeolites exhibit excellently catalytic properties, compared with conventional zeolites.Mesoporous Beta zeolite is synthesized from a mixture of small organic ammonium salts and mesoscale cationic polymers as template. The route involves a one-step hydrothermal synthesis, and the templated mixture is homogeneously dispersed in the synthetic gel. Mesoporous Beta exhibited a better catalytic activity in reactions of alkylation of benzene with isopropanol than conventional Beta.Mesoporous ZSM-5 zeolite with hydrothermal stability and high catalytic activities has been successfully synthesized from a mesoporous template of bread. The bread with environmental benignity, abundant porosity, and good hydrophilicity is suitable and beneficial for the facile synthesis of zeolites with mesoporosity. Mesoporous ZSM-5 is much more active than conventional ZSM-5 in catalytic cracking of bulky molecules (1, 3, 5-tri-isopropylbenzene). Moreover, mesoporous ZSM-5 zeolite exhibited high hydrothermally stability.We develop some kinds of facile, low cost and efficient routes to synthesis of mesoporous zeolites. These mesoporous zeolites have a large amount of mesopores and not only inherit excellent acidity and hydrothermal stability, but also improve the adsorption and diffusion of organic molecules. These mesoporous zeolite materials is much more effective and active in some different catalysis than conventional zeolites.