Designed Synthesis And Properties Of Nanosized Hierarchical Zeolites And Metal-zeolite Composites

Zeolite is one of the most common materials for industrial application with a long in research history.Since the first report of artificial synthesis of zeolite in the 1940 s,the designed synthesis of zeolite has become one of the hottest areas in inorganic chemistry and material chemistry for coping with complex practical needs.Due to its excellent chemical and physical stability,high surface area,modifiable acidic and basic catalytic sites,orderly crystallized pore structure,and inexpensive availability,zeolites are recognized as one of the best catalysts.Whether as a catalyst or carrier for other catalytically active substances,the catalytic performance of zeolites is often limited by the narrow pore structure that hinders the diffusion of bulky molecules,resulting in poor mass transfer performance.Furthermore,,the metal nanoparticles in the metalzeolite composite turn to aggregation after the catalytic process,which will cause a decreased activity.Herculean work has been done in the area of designed synthesis of zeolites,and the most conventional ways to overcome these problems are utilization of nanosized or hierarchical zeolites.Focusing on this issue,this paper mainly revolves around the use of in situ topology conversion methods and the “crystallization in package” synthesis strategy to design and synthesize nanoscale hierarchical zeolites and highly stable metal-zeolite nanocomposite materials.And we have achieved the following results:(1)Using St?ber sphere as non-crystalline silica precursors and tetrapropylammonium hydroxide(TPAOH)as a dual-functional template agent,we have succeeded in converting different sized St?ber spheres into corresponding sized zeolites topologically through a simple hydrothermal process with a low content of water in the system.By controlling the reaction conditions and the degree of crystallization,we can achieve the sustomized nano-sized zeolites with hierarchical structure.Characterized by various instruments,we demonstrated that the initial sol concentration of the reaction is the key to determine the reaction mechanism of the entire system in this transformation process.(2)We have further modified the nanosized zeolites with hierarchical structure.Through the recrystallization process of zeolite,aluminum ions can be doped crystallized into the pore walls of the zeolite crystals,the modified nanosized zeolites possesses good acid catalytic activity.Due to the open mesoporous channels of nanosized zeolites,we have successfully anchored catalytically active Pd nanoparticles in mesoporous structures.The resulting material catalyzes the cascade synthesis of benzimidazole derivatives due to independent catalytic sites.(3)We design and synthesize a metal-zeolite nanostructure encapsulating impregnated cobalt oxide nanoparticles through a “crystallization in package” synthetic approach.We chose poly-2,6-diaminopyridine(PDAP)as the outer polymer layer and then coated Silicalite-1,an all-silicon zeolites impregnated with a cobalt nitrate solution.The synthesized materials were verified by basic characterization methods.It was proved that PDAP was successfully coated on the surface of Silicalite-1.In the process of carbonization and removal of PDAP,cobalt oxide was successfully immobilized in the pores of the zeolites.We then conducted a preliminary catalytic exploration of the worthy material and found that it exhibits good catalytic activity in the catalytic oxidation of benzyl alcohol.