Improved <i>para</i>‐Xylene Selectivity in <i>meta‐</i>Xylene Isomerization Over ZSM‐5 Crystals with Relatively Long <i>b</i>‐Axis Length

Abstract

Abstract ZSM‐5 zeolite crystals with controllable b‐ axis length (sheet‐like, S‐ZSM‐5; chain‐like, C‐ZSM‐5) have been synthesized by using urea and starch as additives in the starting aluminosilicate gels. X‐ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images show that these zeolite samples have good crystallinity. Transmission electron microscopy (TEM) images show that there is a strong chemical interaction between the stacked crystals in C‐ZSM‐5 samples. N 2 sorption isotherms indicate that C‐ZSM‐5 crystals are mesoporous. Catalytic tests for the formation of p ‐xylene from m‐ xylene isomerization show that, compared with other zeolite catalysts, C‐ZSM‐5 catalysts give both high conversion and improved p ‐xylene selectivity, which are attributed to the combination of relatively long b ‐axis length and the present mesoporosity in the crystals. The improvement of p ‐xylene selectivity in catalytic m‐ xylene isomerisation is of great importance for selective industrial production of p ‐xylene in the future.