The paper reviews the influences of pore structure,acidity,and morphology of the molecular sieve materials on xylene isomerization,ethylbenzene dealkylation,and ethylbenzene isomerization reactions.The formation of reaction intermediates are limited in microporous channels,and the differences in diffusion of xylene isomer molecules lead to different selectivity towards xylene.The molecular sieves of three-dimensional 10 membered-ring(MR)micropores,e.g.,ZSM-5,exhibit good performance in ethylbenzene dealkylation reaction.MOR molecular sieves of 12 MR micropores and those of one-dimensional 10 MR micropores with pore-mouth catalysis have high selectivity for ethylbenzene isomerization reaction.The optimization and adjustment of acid type,acid strength,and acid content is beneficial to improving the performance of the xylene isomerization and ethylbenzene dealkylation reactions.The distribution of acidic sites on the outer surface or micropores and mass transfer in micropores and channels of various dimensions can be precisely regulated by morphology control of molecular sieves,thus endowing the molecular sieves of different morphologies with unique reaction performance.The application of molecular sieve membrane materials allows for the coupling of xylene isomerization reaction and separation,and greatly improves the selectivity of para xylene;however,the low reaction activity and para xylene flux limit its industrial application in this field.
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