Synthesis,Modification And Alkylation Catalytic Performance Of MCM-22 Zeolite

Toluene and xylene are important initial materials in chemical industry,which currently produced via the alkylation of benzene with methanol,instead of the traditional catalytic reformation or naphtha pyrolysis,so as to solve the problem of benzene in excess and xylene in deficit.However,the products distribution of benzene alkylation with methanol is complicated,the low selectivity of xylene,the coke and by-product ethylbenzene from side reaction methanol to olefins are still a great challenge due to the acidity of the catalyst.The solutions of these problems are necessary for the industrialization of the alkylation of benzene with methanol.Efforts on pore modification,Si/Al ratio adjustment and the framework molars substitution have been made to explore their influence on the reaction.The main research content and the related conclusion are as follows.Piperidine was used as an organic template in static synthesis of MCM-22,which precursor was swallowed and pillared to establish MCM-36.The catalytic performance of ZSM-5,MCM-22 and MCM-36 was evaluated,and a conclusion that MCM-22 held the best properties on alkylation of benzene with methanol due to its structural characteristics and acid strength was reached.Introducing boron to the framework to substitute aluminum was proved a successful method to regulate the acid distribution in external and internal surface of MCM-22 zeolite as well as an effective way to modify the porous structure of the catalyst.The amount of B incorporated was varied and its effect on the catalytic performance in alkylation of benzene with methanol was studied.The best B/Al ratio was found to be 3,which brought out the best benzene conversion and xylene selectivity of the alkylation reaction.The effects of the reaction conditions on the alkylation of benzene with methanol were studied.The appropriate reaction conditions were come to as:T=753 K,P=1.0bar,WHSV=2.0 h^-1,flow rate=40 mL/min.When the conditions changed,the selectivity of by-product ethylbenzene hardly varied due to the special structural characteristics and appropriate acid strength.While the selectivity of main target product xylene depended more heavily on reaction temperature and flow rate of carrier gas rather than weight hourly space velocity or reaction pressure.