Construction Of Hierarchical Zeolite And Catalytic Pyrolysis Of Baiyinhua Lignite Volatile To Enhance Aromatic Products

Catalytic pyrolysis of lignite is one of the effective methods to improve the quality of lignite volatile.Aromatics are important products by upgrading pyrolysis tar,which have high economic value.In rapid catalytic pyrolysis,the catalyst is an important element to improve the conversion of light aromatics and reduce the activation energy.ZSM-5 zeolite is one of the main choices for its suitable micropores property in aromatization reaction.ZSM-5 zeolite is easy to coking and deactivation in the process of lignite pyrolysis tar light reaction due to its single pore structure.It is very important to modify zeolite and improve catalytic procedure.In this paper,ZSM-5 with different physical and chemical properties was synthesized by hydrothermal method by adjusting silicon source and aluminum source.Hierarchical zeolites with different crystal sizes were synthesized by using P123 as mesoporous template.A double layered bed that used to catalytic pyrolysis of lignite volatiles was formed by combining Zn/MCM-41 and ZSM-5.The physicochemical properties of the zeolites were characterized.The pyrolysis of Baiyinhua lignite catalyzed by zeolite was evaluated in a falling fixed bed reactor.The catalyst lifetime was explored.The conclusions are as follows:1.Zeolites synthesized by three Si sources shows different crystal shapes.Al sources influences crystal formation during crystallinity.2.The reaction products cannot be separated from the ZSM-5 micropores quickly,resulting in the secondary reaction and the formation of carbon deposition precursors.3.The hierarchical zeolite promotes the production of aromatics.The results show that the small cubic crystal shortens the pore channel of the catalyst and significantly improves the benzene selectivity,and the service life of the small cubic crystal is significantly longer than that of micropores zeolite.4.The double layer system can decompose macromolecules step by step,which can inhibit the formation of carbon deposition over ZSM-5 layer.It provides a new idea for industrial application.