Synergism between unsupported Re and Co or Ni sulfide catalysts in the HDS and HDN of gas oil

Two series of unsupported Co-Re and Ni-Re binary sulfide catalysts with variable atomic ratio α = Me/(Me + Re) from 0 to 1 were prepared by the co-maceration method. The catalysts were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and evaluated in the simultaneous hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions of a real gas oil feed under industrial relevant conditions. The results showed a synergetic effect of the Co or Ni sulfide on the ReS₂ in both HDS and HDN reactions. A maximum in activity at the same atomic ratio α ∼ 0.5 was observed for both reactions and both Co-Re and Ni-Re catalysts. The magnitude of the synergy was generally superior for HDS than for HDN, and at low reaction temperature (598 K) larger for Ni-Re than for Co-Re catalysts, especially in HDS, while at high temperature (648 K) it was reverse. Moreover, the Co-Re catalysts exhibited higher HDN/HDS selectivity than the Ni-Re catalysts. Neither XRD nor XPS results evidenced the presence of a "Co-Re-S" or "Ni-Re-S" like phase. It is suggested that the synergism could be associated to the hydrogen activation and spillover from the Co or Ni sulfide to ReS₂.