Application Study On Alkylation Of Benzene With Methanol Over ZSM-11 And Other 10 Rings Zeolites

The alkylation of benzene with methanol can not only solve the problem of benzene pollution and the problem of excess methanol resources,but also produce high value-added xylene.In this paper,the application of ten-membered zeolites,especially hierarchical pore ZSM-11 zeolites,in the alkylation of benzene with methanol were studied,and the role of seed crystals in the synthesis of molecular sieves was discussed.Firstly,compared to other microporous zeolites,MCM-56 has a larger specific surface area and pore volume due to its unique honeycomb structure which results in the high conversion of benzene(52.5%),and the total selectivity of TX is 91.3%;Compared to ZSM-5 and ZSM-5/11,benzene,toluene,xylene,and trimethylbenzene have less diffusion restriction in the ZSM-11 zeolites,thus ZSM-11 has a higher conversion of benzene and higher selectivity of xylene,meanwhile a higher C9 selectivity.Secondly,Hierarchical pore ZSM-11 zeolites was obtained by optimizing the synthesis conditions,which increased the specific surface area and pore volume of zeolites,and improved the diffusion limitation due to the micropores;It was found that the samples had larger specific surface area,porous volume and lower acidity with the high molar ratio of Si/Al.And with Si/Al increased from 30 to 180,the conversation of benzene and the selectivity towards xylene increased,but the ethylbenzene decreased.The catalyst with a Si/Al ratio of 180 could achieve high benzene conversion(62.4%)and high xylene selectivity(38.9%)as well as excellent suppression of ethylbenzene formation(0.2%).Finally,by adding seeds to the synthesis of the hierarchical pore ZSM-11,the crystallization time was reduced from 3 d to 1 d,but did not change the performance of the zeolites;and the amount of template that were harmful to the environment was reduced by seeds,and it was found that as the content of the seeds increases,the particle size of the zeolites becomes smaller.