Shape selective disproportionation of toluene over HZSM-5 zeolite modified by chemical liquid deposition:II Effect of hydrothermal treatment and reaction conditions

Hydrothermal treatment on the conversion of toluene and selectivity of p-xylene(PX) in toluene disproportionation over the HZSM-5 catalyst modified with silica by chemical liquid deposition were investigated.The catalyst was treated with steam at the temperature of 250～500 ℃ under atmospheric pressure.After the steam treatment at 300～350 ℃ for 2 hours,the conversion of toluene and selectivity of PX reached 23.5% and 96.5%,respectively.Reaction conditions,such as reaction temperature,pressure,WHSV and H_2/toluene(molar ratio),were investigated in toluene disproportionation.The results indicated that high pressure,relatively low reaction temperature and low WHSV increased the yield of PX.The activity,selectivity and yield of PX reached 25.8%,94.1% and 10.5%,respectively,under the reaction conditions of 420 ℃,2.5 MPa,(1.5h~(-1)),2～3 of molar ratio of H_2/toluene.