Oxygen free conversion of natural gas to useful hydrocarbons and hydrogen over monometallic Mo and bimetallic Mo-Fe, Mo-Co or Mo-Ni/HZSM-5 catalysts prepared by mechanical mixing

摘要

This work aims to approach a compromise of the activities of Mo/HZSM-5 catalyst as well known high performance aromatization catalyst after substituting half its Mo with Fe, Co or Ni (well known active hydrogen releasing metals) for hydrocarbons and hydrogen production. The catalysts were prepared by the mechanical mixing procedure in order to keep the zeolitic pores almost free of metal incorporation and hence reducing the metal/zeolite acid interaction. The catalytic performance of the catalysts was investigated during the non-oxidative conversion of natural gas to hydrocarbons and hydrogen in a fixed bed flow reactor at 700 °C and gas hourly space velocity (GHSV) of 1500 ml/g/h. The catalysts were characterized by XRD and TGA, where the results showed that the bimetallic 3%Mo-3%Fe, 3%Mo-3%Co or 3%Mo-3%Ni containing catalysts significantly decreased hydrocarbon (ethylene and aromatics) yield and selectivity as compared to the monometallic 6%Mo/HZSM-5 catalyst. The substitution of group VIII metals enhances the rate of coke and hydrogen formation in the direction of going from Fe → Co→ Ni. This behavior can be attributed to the electronic properties of these metals, where maximum reaction rates are exhibited by the metals with six to eight d-electrons.