The Study Of The Modified HZSM-5 Zeolite By The Dual-metal Cr,Zn For The MTA Reaction

In recent years,due to the shortage of the petroleum resource and the overplus of the methanol capacity,the methanol to hydrocarbons(MTH)become the focus in the development of coal chemical industry.Among which the aromatization of methanol(MTA)produce the high additional-value light aromatics(BTX)by the low-cost methanol.The MTA could meet the market demand of the BTX and achieve a high economic benefit,therefore the MTA reaction has attracted wide attention from the researchers.For the study of the catalysts in the MTA reaction,the acid sites,structure property and reactive conditions were mainly explored.In this study,the co-impregnation of Zn and the second metals of Zr,Ce,Mo,Cr species into HZ zeolite by the' incipient impregnation method was investigated.Under the conditions:the temprature of 430?,the pressure of 0.1 Mpa,the LHSV of 1.2 h-1 and the flow of N2?25 mL/min,the results of active tests revealed that the ZrZn/HZ,CeZn/HZ,MoZn/HZ catalysts showed lower yield of BTX and poor stability,but the CrZn/HZ exhibited higher catalytic activity.Then the CrxZnl/HZ catalyst was characterized using the XRD,BET,SEM,TEM,NH3-TPD and XPS techniques.The well metal dispersity and the large amount of ZnOH+ sites were analysed in the Cr2Zn1/HZ catalyst.The stability and the carbon deposit of the Cr2Zn1/HZ catalyst were valued in the fixed-bed,the result showed that the conversion of methanol was 100%,the yield of BTX was 56.81%,The life-span of the catalyst was 32h and the low rate of the coke deposit.Therefore,Cr,Zn dual-metal modified catalyst showed well catalytic performance.The hierarchical CHZ zeolite has been synthesized using the surfactant CTAB as mesoporous template agent.The influence of the different CTAB content on the structure property of zeolite has been characterized by the XRD,BET,SEM,TEM and NH3-TPD methods.The results exhibited that the CHZ-12M catalyst with the mesoporous pore had high BET surface area and pore volume,such as 387.896 m2g-1,0.2617 cm3g-1 respectively.The performance of the CHZ-12M catalyst was also tested and the results showed that the conversion of methanol and the yield of BTX at the 8h on the stream were 100%and 29.29%,respectively,which suggested that the CHZ-12M catalyst had the good catalytic activity.Then the modified hierarchical CHZ zeolite by the dual-metal Cr,Zn were characterized and valued.There were well diffusion channels and more medium-strength acid in the Cr2Zn1/CHZ-12M catalyst.So the Cr2Zn1/CHZ-12M catalyst showed stable and efficient performance,the initial yield of BTX was 54.52%,the weight loss rate of carbon deposition was 10.04%,the catalytic life-span was 69h.Therefore,the appropriate adjusting the acid distribution and optimizing the diffusion channel in the HZSM-5 catalyst could effectively promote the catalytic performance in the process of the MTA.