Green Synthesis Of Functionalized ZSM-5zeolite And Its Study On Aromatization Of Propane

In recent years,the consumption of non-recyclable petroleum resources has increased dramatically and the global environmental pollution has intensified.The utilization of low-carbon hydrocarbon resources has become a growing concern.Low carbon alkanes or alkenes can be aromatized to obtain higher value aromatic products,such as benzene,toluene and xylene(BTX),which can make low carbon hydrocarbon resources play a more important role.Propane is one of many hydrocarbons with broad commercial potential,and the shale gas revolution has made it a rich source of feedstock.At present,ZSM-5 zeolite catalyst is reported to have better catalytic performance for propane aromatization reaction,which is inseparable from the unique pore characteristics of ZSM-5 zeolite catalyst itself and the acid condition of automatic adjustment.Therefore,ZSM-5 zeolite catalyst can be controlled and adjusted through different preparation and modification pathways,so as to produce a better catalyst.Hydrothermal synthesis method need to join in the process of synthesis of a large amount of solvent,this will lead to low molecular sieve production rate and production safety and environmental pollution and so on a series of problems,and in the process of synthesis for material preparation,successful have to add some expensive template agent,greatly improve the response and is not conducive to mass production.In order to solve the above problems,in this paper,from the perspective of practical application,the green solvent-free method was used to synthesize ZSM-5zeolite.The ZSM-5 zeolite with adjustable multi-pore structure,suitable zeolite acidity and different external crystal morphology was synthesized,and the synthesized zeolite was modified to improve the catalytic performance of the aromatization reaction.The main work of this paper is as follows:1.The single microporous structure of ZSM-5 zeolite is not conducive to the diffusion of macromolecules and the exposure of catalytic active sites.The multiporous ZSM-5 zeolite was synthesized by a simple solvent-free method.Firstly,the ZSM-5 zeolite was synthesized by solvent-free seed method,and the mesoporous structure was introduced into the ZSM-5 zeolite by adding biomass polysaccharides(sodium alginate,carrageenan,chitosan,sucrose,glucose),so as to control the external morphology of zeolite,adjust the acidity of the molecular sieve and improve the activity of the reaction.The experimental results show that the addition of sodium alginate can significantly affect the morphology of zeolite.In addition,the addition of sodium alginate also changed the acidity of zeolite,resulting in a difference in catalytic performance.2.The multi-pore ZSM-5 zeolite has a large specific surface area and rich pores,which is conducive to improving the anti-carbon deposition capacity and mass transfer efficiency of zeolite.The multi-pore HZSM-5 zeolite is an excellent catalyst,but its dehydrogenation ability and aromatization activity are poor for saturated low carbon alkanes.Zn/HZSM-5 catalyst was synthesized solvent-free by impregnating active component Zn and used for aromatization of propane.The prepared Zn/HZSM-5 catalyst can significantly improve the activity of the aromatization reaction.3.The traditional impregnation method is used to load the active metal on the surface of zeolite.The dispersion of the metal is poor,and even the aggregation of large particles will occur.Multiporous Zn@HZSM-5 zeolites were synthesized in situ by solvent-free mechanical grinding of Zn source and ZSM-5 zeolites,which significantly improved the uniform distribution of Zn species on the surface of zeolites.In the process of propane aromatization,Zn@HZSM-5 catalyst prepared by solven-free in-situ method can significantly improve propane conversion and aromatics selectivity.Through the study of the above process,the solvent-free synthesis of ZSM-5zeolite can effectively solve the problems of low molecular sieve yield,production safety and environmental pollution.The mesoporous structure of ZSM-5 zeolite was introduced by adding biomass polysaccharide to control the external morphology of zeolite,adjust the acidity of the molecular sieve and improve the reaction activity.Functionalized ZSM-5 zeolite catalysts were prepared by impregnation and in situ synthesis,which can significantly improve the conversion and selectivity of propane aromatization.