Transformation of olefin over Ni/HZSM-5 catalyst

Olefins in the cracked naphtha can be transformed into aromatics and isoparaffin to reduce the olefin content as well as to improve the octane number. In this work, Ni/HZSM-5 bifunctional catalyst was prepared and was characterized by nitrogen adsorption, FT-IR analysis with adsorbed pyridine as well as by X-ray powder diffraction analysis. The activity of the catalyst was investigated with the transformation of 1-hexene. The experimental results show that the main reactions occurring over Ni/HZSM-5 at relatively low temperature are cracking and isomerization of 1-hexene, which results in the high concentration of olefin in the hydrotreated product. The double-bond isomerization of 1-hexene is dominant at low temperature (<220 °C) while the skeletal isomerization is elevated at high temperature, and the aromatization activity of the Ni/HZSM-5 catalyst is promoted by high temperature. The sulfided Ni/HZSM-5 catalyst shows higher aromatization activity than the reduced one and the zeolite supported Ni catalysts show comparatively better stability than that without metal components.