Toluene Disproportionation Reaction over Modified HY and LaHY Catalysts

Abstract

A series of catalysts were prepared by the modification of NH4NaY zeolite. Effects of pretreatment such as calcination, steaming, NH+4 ion-exchange, and La3+ ion-exchange of zeolite Y on the reaction of toluene disproportionation and its transient period were studied. It was found that the acid strength of zeolite increased with pretreatment by La3+ ion-exchange. The hydrothermal treatment caused more significant dealumination of zeolite than it did calcination, and the presence of La3+ ion in the zeolite could inhibit the dealumination process. It also indicated that the higher the acid strength, the higher the initial conversion, and the shorter the transient period; however, the catalysts calcined at 773 K gave the maximum average conversion. It was concluded that the best way to prepare Y zeolite catalysts for the toluene disproportionation reaction was NH+4 ion-exchange followed by La3+ ion-exchange, and then calcination at 773 K followed by another NH+4 ion-exchange. The appropriate amount of La3+ in LaHY zeolite was found to be 3.07-4.80 wt.-% for the reaction of toluene disproportionation.