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

The capacity of sulfur exchange (i.e. S-TE-the total number of exchangeable sulfur atoms) has been determined at 673 K in a circulation system with H2S (partial pressure similar to 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 S-TE values and thiophene hydrodesulfurization activity of the catalyst samples, containing Mo. The S-TE 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 (S-35(cat)) 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. (C) 2011 Elsevier B.V. All rights reserved.