Mechanistic studies and kinetics of the desulfurization of 2-phenylcyclohexanethiol over sulfided Mo, Ni-Mo, and Co-Mo on γ-Al2O3

The desulfurization of 2-phenylcyclohexanethiol (2-PCHT) was studied over sulfided Mo/γ-Al2O3, Ni-Mo/γ-Al2O3, and Co-Mo/γ-Al2O3 catalysts under 5.0 MPa H2 or Ar at 240 °C. Under H2, the desulfurization of 2-PCHT proceeded mainly through the hydrogenolysis and β-elimination pathways. The former was faster than the latter over Mo/γ-Al2O3. Ni and Co accelerated the β-elimination pathway but hardly affected the hydrogenolysis pathway. The activity of Mo/γ-Al2O3 was enhanced by Ni, whereas Co did not show any promoting effect. Under Ar, the desulfurization of 2-PCHT occurred mainly through the β-elimination and dehydrogenation pathways. The β-elimination pathway was faster than the dehydrogenation pathway. Both pathways were enhanced by Ni and Co. Ni and Co promoted the dehydrogenation pathway mainly by promoting the dehydrogenation-ring closure reaction. The inhibiting effects of piperidine depended on the reaction and catalyst. Under Ar, Ni-Mo/γ-Al2O3 was more sensitive to piperidine inhibition.