Sulfur exchange capacity and thiophene hydrodesulfurization activity of sulfided molybdena-alumina catalysts promoted by nickel

The capacity of sulfur exchange (i.e. STE—the total number of exchangeable sulfur atoms) has been determined at 673 K in a circulation system with H2S (partial pressure ∼2.5 and 25 kPa) for five sulfided catalyst samples: molybdena-alumina (Mo12), NiO/Al2O3 (Ni12) and three Ni-promoted molybdena-alumina with different Ni:Mo ratios [NiMo(0.X)]. A linear correlation has been found between the STE values and thiophene hydrodesulfurization activity of the catalyst samples, containing Mo. The STE values have been determined also in exchange between catalyst sulfur and thiophene, for three samples: Mo12, Ni12, and NiMo(0.35) for comparison of the S-exchange affinity of S in thiophene with that in H2S. The isotope exchange capacity of sulfur bound to the catalyst (35Scat) with sulfur in H2S was substantially higher than that with sulfur in thiophene, but the sequence of the STE values was similar for the three samples, i.e., NiMo(0.35) > Mo12 > Ni12.