Catalytic Performance Of Hierarchical Y Zeolites Supported Metal Ions And Encapsulated Metal Complexes

Y zeolite has been used as adsorbent, catalyst or catalyst support in petrochemical industrial, petroleum refining and fine chemicals synthesis due to its regular pore structure, high hydrothermal stability and strong acidic. However,its small pore diameter limits the diffusion rate of reactants and products in the pores. The limited pore size of zeolite imposes the long diffusion path, the slow rate of diffusion and spatial resistance, which greatly reduces the accessibility of active sites, resulting in the maximal availiablity of zeolite difficult to be implemented in catalysis fields. Recently, hierarchical zeolites have been conceived. These zeolites integrate the native microporosity with an auxiliary level of inter or intra-crystalline mesopores. In this paper, a series of hierarchical Y zeolites with different pore structures were prepared by post-synthesis and used as hosts for encapsulation of metal complexes and loading metal ions.Metal complex guests were successfully encapsulated in the cavities of hierarchical Y zeolite hosts by the “ship-in-bottle” method, and the host effects of hierarchical Y zeolite were investigated. In addition, the supported Co catalysts were also prepared by ion-exchange, and their catalytic performancesin oxidation of alkene and cyclohexane were investigated. The main results are as follows:1) Preparation and characterization of hierarchical Y-zeolitesHierarchical Y zeolites were prepared by post-treating zeolite Y with a sequential dealumination and desilication method. A series of hierarchical Y zeolites with different pore structures were prepared by change alkali concentrations. We got Y-0.05 M zeolite with the highest Smeso(287 m2/g) and hierarchy factor(0.15) at 0.05 M Na OH and Y-0.2M zeolite with Smeso(130 m2/g)and hierarchy factor(0.09) at 0.2M Na OH.2) Preparation, characterization of Co/Z and their catalytic propertiesWe prepared the Co/Z(Z=Y, Y-0.05 M, Y-0.2M) catalysts by the ion exchange method and investigated their catalytic behaviors in the oxidation of cyclooctene and cyclohexane. The catalytic reaction results showed that the Co/Y-0.05 M and Co/Y-0.2M exhibited much better performances than Co/Na-Y in the oxidation reactions of cyclooctene or cyclohexane. The hierarchical zeolite exhibited significant improved host effect, especially for molecular oxygen or hydrogen peroxide was used as oxidants in reactions. However, when styrene was used as the substrate, the host effect of the hierarchical zeolite was not as obvious as in the oxidation of cyclooctene and cyclohexane. This indicated that the hierarchical host effect was closely to the oxidants and the size of the reaction substrates.3) Preparation, characterization and catalytic properties of Fesalcn/YAn efficient strategy for the encapsulation of metal complex guest into zeolite Y was proposed. This strategy involves loading iron ion on Y-zeolite by ion exchange method and coordinating the metal ions with the organic ligand by flexible ligand method. The characterized of XRD, N2 physical absorption, SEM,FT-IR, UV-vis, ICP, as well as the catalytic performance in cycloalkane oxidation indicated that Fesalcn could be encapsulated in the supercages without affecting the zeolite framework structure. The results showed that, Fe complexes encapsulated in hierarchical Y-zeolite gave higher catalytic activities in the oxidation of cyclohexane than those encapsulated in zeolite Y. The hierarchical zeolite exhibited significant improved host effect. The prepared Fesalcn/Y-0.05 M catalyst exhibited excellent shape-selective catalytic properties to the different substrates. Detailed investigation about the influence of reaction factors such as oxidants, reaction temperature, reaction time and other factors on the catalytic performance over Fesalcn/Y-0.05 M were carried out.4) Preparation, characterization of Cuphen/Y and their catalytic propertiesIn order to investigate the effect of different Y zeolites on the cyclohexane oxidation performance of the composite materials, Cuphen/Y with different hosts were prepared. The oxidation of cyclohexane tests showed that zeolites Y with different pore structures could greatly influence the catalytic activities of the composite materials. At the identical reaction conditions, Cuphen/Y-0.05 M and Cuphen/Y-0.2M have higher activity than Cuphen/Y in cyclohexane oxidation due to less resistance on the diffusion of substrate and products forthem. Cuphen/Y-0.2M exhibited the highest reactivity. In addition, the effects of the composite materials loading amount on catalytic activity were also investigated. The results showed that the TON of catalyst drastically decreased with the increased of loading amount.