Synthesis of holycrystalline nano-ZSM-5 aggregate and its application in methylation of toluene
It is a great challenge to develop an efficient catalysts for the industrial application of toluene methanol alkylation technology to produce p-xylene.The holocrystalline nano-ZSM-5 aggregates were synthesized using ZSM-5 zeolites shaped by silica sol as the precursor by means of liquid phase crystallization.The characterization results showed that the amor-phous SiO2 species on the surface of shaped-ZSM-5 by silica sol were transformed into crystalline phase structure during recrystallization process.In addition to its inherent microporous pores,the formed HCZ150 zeolite possessed abundant and uniform binary pore structure,concentrated at around 1.3 nm and 10 nm,with a total specific surface area of 260 m2/g and an external specific surface area of 72 m2/g,respectively.The evaluation results of toluenealkylation with methanol showed that the holocrystalline HCZ150 zeolite had a p-xylene selectivity of 70%,which was significantly higher than that of SBZ150 extruded with pseudo boehmite as binder.The P/HCZ150 catalyst prepared by P2O5 modification exhibited a p-xylene selec-tivity of 90%,and there was no decrease in catalyst activity ever after 24 hours of reaction.The good stability was attributed to the rich pore structure and easy accessibility of active centers.A new approach for the preparation of toluene methylation catalysts was provided,which had certain guiding significance for the industrial application of this technology.
holycrystalline zeoltenano-ZSM-5 aggregatetoluene alkylation with methanolp-xylene
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