Preparation, Characterization And Performance Of Meso-zeolite Y

Zeolite Y with three dimensional pore faujasite framework and Si/Al>1.5, belongs to hexagonal system. Because of its high catalytic activity, excellent ion exchange capacity and adsorption performance. Zeolite Y has been widely used in petroleum chemical industry, fine chemical, environment protection, as well as in the area of new functional materials, especially in the process of the fluid catalytic cracking(FCC). Zeolite Y shows an irreplaceable role. Especially in the process involving macromolecules in catalytic and biological macromolecules separation of application, the narrow channels and the large difrudion resistance of zeolite Y, make its wide application extremely be limited. The main problems are as follows:high reaction temperature, quick catalyst deactivation because of coke, and decreased product selectivity in some reactions. Introduction of mesopores in zeolite Y crystal is an important method to solve this problem.Herein, we show a method for preparation of mesoporous zeolite Y. Fumed silica was first organic functioned by organosilane, and then this organic functioned SiO2 was used as silica source in the synthesis of zeolite Y. Meso-zeolite Y with a certain mesoporous volume and external surface area has been successfully synthesized using this method.The preparation conditions have been investigated detailedly. A series of silica source functioned by different amount of organosilane has been used, and the experimental results show that the silica source with modifiy rate Y-5669/SiO2=13.8% is the best one to prepare meso-zeolite Y. The molar composition of silylanization structure directing agent was 13Na2O:15SiO2: Al2O3:32OH2O, and the molar composition of synthesis zeolite Y was 3.5Na2O: 9SiO2:Al2O3:120H2O:3-5% directing agent. The aging time, aging temperature, crystallization time, crystallization temperature and alkalinity were investigated detailedly. And the optimum preparation conditions for meso-zeolite Y was as follows:the alkalinity Na2O/SiO2=0.32, aging 5-8 hours at 40℃ under stirring, crystallization at 100℃ for 22 hours, then the product was washed with distilled water, filtered, dried overnight at 90℃, and calcined at 550℃ for 5 hour. The pore structure parameters of meso-zeolite Y were as follows:the BET surface area of 818m2/g, external specific surface area of 72m/g, the mesopore volume of 0.093 cm/g.The TEM images of meso-zeolite Y show that the samples were aggregates of nano-particles; N2-adsorption-desorption result shows a type Ⅰ and Ⅳ isotherms and HU-type hysteresis loop; DFT pore size distribution shows that in that mesopore around 5-5.5nm were existed; The 29Si MAS NMR and 27Al MAS NMR indicates that lots of Si-OH exists on the surface of meso-zeolite Y, and variable disturbtion surface tetrahedral-coordinate aluminum exists; NH3-TPD results showe that the sample has more mediate strong acid.The molecules diffusion processes in the zeolite Y and meso-zeolite Y were investigate the ZLC method and toluene as adsorbate molecules. The effective diffusion time constants(D/R2) value of meso-zeolite Y are larger than zeolite Y, and the activation energy(Ea) of meso-zeolite Y are smaller. Due to existence intercrystalline mesopores of meso-zeolite Y, the diffusion resistance was reduced, which making diffusion process speed up.