In-Situ Synthesis Of Hierarchical Zeolite Y

Hierarchical zeolite Y can reduce the diffusion limitation of large heavy oil molecules, make it easier to access to active sites to be cracked by increasing the mass transfer of catalyst, which effectively improves the catalytic transformation of large heavy oil molecules, so it is important for industrial production. At present, hierarchical zeolite Y is commonly synthesized by TPOAC (dimethyltrimethoxysilylpropyloctadecylammonium chloride) and CTAB (cetyltrimethylammoniumbromide) as template. However, high cost of template limits industrial application of hierarchical zeolite Y.In-situ synthesis of mesoporous Y using TPHAC (cetyldimethyltrimethoxysilylpropylammoniumchloride) as the mesoporous template directly synthesized by alkyl amines and silane coupling agent was investigated in this paper. In view of the above problems, The optimal feedstork molar ratio is 2.9 Na2O·Al2O3·8.4 SiO2·250 H2O. The mass transfer capacity of the system can be improved by the double deck impeller. The product has clear characteristic diffraction peaks of zeolite Y. The total surface area is 663 m2·g-1. The mesoporous surface area is 133 m2·g-1.The pilot-scale synthesis of hierarchical zeolite Y in 10 L autoclave is achieved. The cost of it is 12731 yuan/ton. The best experimental conditions of pilot-scale products are:hydrolysis time is 1.5 h and crystallization time is 24 h. The relative crystallinities exceed 80%, indicating that the reproducibility of the experimental results is excellent. After hydrothermal treatment for 4 h, the reserved ratio values of mesoporous surface area of the modified zeolite is 39%, indicating that hydrothermal stability of the pilot-scale product is excellent.Crystallization mother liquor contains a large number of TPHAC template and other unreacting completely raw materials. Hierarchical zeolite Y was synthesized by mother liquor recycling. The mesoporous surface area of product is 126 m2·g-1. The products by mother liquor recycling for five times have high relative crystallinity and surface area. After hydrothermal treatent for 4 h The reserved ratio values of mesoporous surface area of the modified zeolite is 38%, indicating that hydrothermal stability of the product is excellent.Hierarchical zeolite Y is prepared by a method combining soft templating with post-synthetic treatment. The relative crystallinity of the product is 84%. The total surface area and mesoporous surface area are 720 m2·g-1 and 174 m2·g-1, respectly. Structure parameters are greatly improved compared to conventional synthesis.