Isoparaffin-rich gasoline synthesis from DME over Ni-modified HZSM-5
Ni-modified HZSM-5 was prepared using a wet impregnation technique and tested for isoparaffin-rich gasoline synthesis from DME (DTG). The results verified that nickel modification of HZSM-5 can evidently promote the formation of isoparaffins; the isoparaffin content of the gasoline-range hydrocarbons can increase from 42.7% to 66.3% on complete conversion of the DME. Some physical and chemical characterization methods were used, like TPR-H2, XRD, TPD-NH3 and N2 adsorption/desorption isotherm tests, and the results confirmed that the active state of the surface Ni species on HZSM-5 has great influence on the product hydrocarbon distribution from the DTG reaction. NiOx (0 < x < 1) mainly contributes to hydroisomerization of the olefins, while metal Ni0 particles promote a cracking reaction of the paraffins. The nickel modification could significantly decrease the acidic site strength but increase the acidic site numbers of HZSM-5, which in turn influences the catalytic performance of HZSM-5 for conversion of DME to hydrocarbons.