Controllable Synthesis Of Zeolite Catalysts For The Catalytic Epoxidation Of Bulky Alkenes Efficiently

Zeolite,as the most important solid catalyst,is widely used in chemical industry and occupies a very important strategic position in the national economy.However,due to the limitation of microporous structure,zeolite has low catalytic efficiency for organic bulky molecules.In order to break through this limitation,various methods have been reported for the synthesis and modification of zeolite molecular sieves.The method of synthesizing and preparing layered molecular sieves effectively increases the ratio of outer/microporous specific surface area of molecular sieves,and greatly improves the catalytic efficiency of zeolite.In this paper,zeolite catalysts were systematically studied for epoxidation of bulky alkenes through using the abundant working experience accumulated by our group.At the beginning,we researched the effects of rotational and static hydrothermal crystallization modes on the synthesis of Ti-FER（Pre）and investigated systematically the influence of reactor speed（0 rpm,30 rpm,60 rpm,100 rpm）for material synthesis,morphology,size,physical and chemical properties,etc.We studied the physical and chemical properties of Ti-ITQ-6（Cal）catalyst which was obtained by delamination and calcination of the layered precursor of Ti-FER（Pre）.The catalysts were applied to the catalytic epoxidation of norbornene with hydrogen peroxide as the oxidant.The results showed that the Ti-ITQ-6（Cal）catalyst obtained by rotational synthesis displayed the most excellent catalytic activity,which was attributed to smaller crystal size,larger specific surface area,and highly exposed tetracoordinate titanium species of the catalyst.Subsequently,under the synthetic condition of60 rpm,we investigated the effects of gel composition on the synthesis of layered precursor Ti-FER（Pre）and physicochemical properties of Ti-ITQ-6（Cal）catalyst.Based on the structure-activity relationship study,the optimal molar ratio of the gel was finally determined.Finally,CoSAPO-5 molecular sieves were synthesized in situ by a one-step hydrothermal rotation method.For comparison,two-step method(Co²⁺-exchange or impregnation method)was used to prepare Co/SAPO-5 catalyst.The one-step rotation method is simple,and the product exhibits higher activity and selectivity for styrene epoxidation,possibly due to the fact that CoSAPO-5 synthesized by one-step method facilitates the dispersion of Co²⁺in the active position of zeolite framework.