溴甲烷甲基化甲苯制备对二甲苯的催化研究

HZSM-5 crystals of regular morphology and high crystallinity were synthesized by hydrothermal method. The modifications of the HZSM-5 crystal gave P/HZSM-5, Si/HZSM-5 and P-Si/HZSM-5 catalysts by impregnation method. In addition, core-shell composite crystals of HZSM-5@Silicalite-1 were obtained by in-situ growth method. Different techniques of XRD, SEM and N2 physioabsorption were employed to characterize the as-synthesized HZSM-5 and modified HZSM-5 materials. They were examined as catalysts for the methylaytion of toluene with methyl bromide. It was found that the modification of P and/or Si components led to the improvement of selectivity of papra-xylene while the catalytic activity of HZSM-5 molecular sieve declined. Especially, para-xylene selectivty up to 69.1％ and high toluene conversion of 37.2％ was observed over P-Si/HZSM-5 catalyst (P2O5 loading 5 wt% and SiO2 loading 6 wt％).