Study On Synthesis And Shape Selective Ethylation Of Core-shell MFI Catalytic Materials

Para-diethylbenzene is an organic chemical intermediate with high added value,which is usually prepared by shape-selective disproportionation and ethylation reaction of ethylbenzene.Shape-selective catalysis has always been one of the important research directions in the field of zeolite and catalysis.Improving shape-selective selectivity is the key to the development of catalysts,and preparing core-shell zeolite is one of the most effective ways.On the other hand,as the raw material for the production of p-diethylbenzene,ethylbenzene,it can itself be prepared by the ethylation reaction of benzene and ethylene,and during this reaction,diethylbenzene is also an important by-product.Therefore,this thesis focuses on the preparation of core-shell MFI catalytic materials and attempts to synthesize ethyl-benzene co-production p-diethylbenzene by shape-selective ethylation of benzene:1.The core-shell composite ZSM-5/MCM-41 material with high shape-selective catalytic ability was synthesized by multiple coating methods,and the effects of multiple coatings on the physicochemical properties and catalytic properties of the core-shell materials were studied.The core-shell material has a rich and regular mesoporous structure,which can effectively passivate the acid sites on the outer surface of the catalyst and reduce the diffusion resistance between mass transfers.In the shape-selective ethylation reaction of benzene and ethylene,the core-shell composite ZSM-5/MCM-41 material improves the shape-selective selectivity of the reaction,and has high reaction stability and life.2.A core-shell binder-free zeolite was successfully prepared by gas-solid phase crystal transfer method,which the amorphous silica binder in the industrial extruded sample was crystallized into a MFI-type zeolite.It was compared with the sample containing the binder to investigate the effect of the binder on the physical and chemical properties of the zeolite.Core-shell binder-free zeolite improves the influence of the binder on the zeolite and inactivates the acid sites on the outer surface of the zeolite.In the shape-selective ethylation reaction of benzene,the reaction stability is higher,but the para-selectivity is raised slightly.3.The MgO modified core-shell ZSM-5 zeolite was prepared by impregnation method,which not only passivated the acid sites on its outer surface,but also changed the overall acidity of the catalyst.Comparing it with CLD modified samples,in the shape-selective ethylation of benzene and ethylene,the MgO modified sample has higher para-selective selectivity and better catalyst stability.