Abstract:

A composite-modified nano ZSM-5 zeolite catalyst was prepared through multi-step impregnation with the precur-sor of SiO₂,MgO,P₂O₅ and Pt.The catalytic performance for alkylation of toluene with methanol was investigated in a six-stage fixed bed reactor,which is filled with more than 720 g of the catalyst.The result shows that the conversion rate of toluene was controllably adjusted in the range of 22%~30% by adjusting the amount-of-substance ratio of toluene to methanol,as well as the selectivity to xylene in liquid products of alkylation and selectivity to p-xylene in xylene（o-xylene,m-xylene and p-xylene） both simultaneously stabilized above 95%.The life of the catalyst reaches 1 300 h in alkylation reaction and the catalytic activity decreased after 1 200 h.The fresh and deactivated catalysts were characterized by XRD,TG-DTG and N₂ adsorption-desorption.It is indicated that the generated coke blocked the pores of ZSM-5 zeolite or deposited on the active sites of catalyst,leading to the catalytic deactivation.The catalytic activity of deactivated catalyst almost can be restored after in-situ regeneration.

Key words: ZSM-5 zeolite, alkylation of toluene with methanol, p-xylene, in-situ regeneration