Shape-Selective Alkylation of Toluene with Methanol over Modified Nano-scale HZSM-5 Zeolite

Shape-selective alkylation of toluene(T) with methanol(M) was performed over Si-P-Mg-modified nano-scale HZSM-5 zeolite. The change of acidity and pore structure of the catalyst was studied by X-ray diffraction,NH3 temperature-programmed desorption,Fourier transform infrared spectroscopy,and N2 adsorption.The effects of temperature,space velocity(WHSV) ,and flow rate of N2 carrier gas on the reaction were investigated in a continuous flow fixed-bed reactor. Under the optimized conditions(2 h–1,460 oC,n(T) /n(M) = n(H2O) /n(HC) = n(N2) /n(HC) = 8,where HC represents toluene and methanol) ,during 500 h on stream over the Si-P-Mg modified nano-scale HZSM-5 catalyst,the toluene conversion of about 10% and the selectivity to p-xylene of more than 97% were maintained,indi-cating that the catalyst exhibits high selectivity and good stability.