METHOD FOR SYNTHESIZING RARE EARTH-ZSM5/ZSM11 COCRYSTALLINE ZEOLITE OF SMALL CRYSTAL GRAIN

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A method for synthesizing rare earth-ZSM5/ZSM11 cocrystalline zeolite of small crystal grain is provided. In the method, raw materials are silicon source, aluminum source, inorganic base or inorganic acid, 1, 6-hexamethylene diamine, salt of rare earth element, additive and deionized water. The method comprises the following steps : firstly raw materials are aged for 4-30 hours at a low temperature between 60-98 ℃, then crystallized at 160-195 ℃ for 15-70 hours, and hydrothermally synthesized into rare earth-ZSM5/ZSM11 cocrystalline zeolite of small crystal grain. Synthesized zeolite has ZSM5 and ZSM11 structures, with an average granularity of less than 500 nm, wherein ZSM5 content is 10-90 % by weight of the cocrystalline zeolite. The merit of this method lies in that high temperature crystallization is rendered after aging at a lower temperature so as to facilitate the formation of small crystal grained zeolite. The additive in raw material is environment friendly.