Preparation Of Hierarchical ZSM-5 Supported Catalysts And Their Performance For Toluene Catalytic Combustion

Concomitant with the rapid economic growth,volatile organic compounds(VOCs)emitted from industrial production have seriously affected the air quality.Studies have shown that VOCs are the main precursors of ozone and organic aerosols,which significantly change the atmospheric phychemical properties in the processes of chemical reactions,and exert significant adverse influence on regional and global environment result from long distance transmission.In recent years,air problems such as haze and PM2.5 have become increasingly serious in China.It is imperative to control VOCs emission from the sources.As an economically feasible and environmentally friendly VOCs elimination method,the research core of catalytic combustion is the development of efficient and stable catalysts.This paper mainly focuses on the preparation of hierarchical ZSM-5 supported catalysts and the study of toluene catalytic combustion performance.The main conclusions of this paper are as follows:(1)The hierarchical ZSM-5 were prepared by steam assisted crystallization method,and the effect of temperature of gel drying,duration of gel drying and temperature of steam-assisted crystallization were investigated for mesoporous structure.Experimental results had shown that adjusting duration of gel drying can significantly affect the aggregation behavior of the micelle,to change the microstructure of subsequent gel crystallization into ZSM-5 zeolite and finally realized to control the mesoporous volume of hierarchical ZSM-5 zeolite.(2)Preparetion hierarchical ZSM-5 zeolite supported Pt atalysts with different mesoporous volumes and used to study on toluene catalytic combustion.The effect from mesoporous volumes of hierarchical ZSM-5 on Pt dispersity has investigated.The experimental results showed that increasing the mesoporous volume was beneficial to improve Pt dispersity,and thus to promote the performance of corresponding catalyst in catalytic combustion of toluene.In addition,increasing the mesoporous capacity can promote the diffusion of reactants.(3)Non-noble metal catalysts were prepared by loading cobalt-manganese composite oxides on hierarchical ZSM-5 zeolite.The cobalt-manganese composite oxides were loaded onto hierarchical ZSM-5 zeolite by redox method,and the relationship between the microstructure and surface properties of the catalyst and the catalytic combustion of toluene has investigated.The experimental results shown that the surface of the catalysts has more species of surfactant adsorption oxygen,high oxidation state of Co species and low oxidation state of Mn species,it will result in toluene catalytic combustion performance significantly improved.Hierarchical zeolite can promote the enrichment of VOCs molecules,the dispersion of active species and the stability of catalysts.