Adsorption and catalytic properties of CoMoAl₂O₃ catalysts and of their components in thiophene hydrodesulfurization reaction

The catalytic activities of CoMoAl₂O₃ catalysts and of their components in the thiophene hydrodesulfurization reaction (HDS) were studied by a flow circulation technique. Catalysts in the oxidic form with CoMoO₄ as the main phase are shown to possess the highest activity for the thiophene HDS reaction. Adsorption of H₂, thiophene, and of their mixture on sulfided CoMoO₄ and technical CoMoAl₂O₃ catalysts was investigated by TPD. H₂ is adsorbed both molecularily and dissociatively on the catalysts studied, while thiophene is molecularily adsorbed. Desorption activation energies for the different H₂ and thiophene forms were measured. The thiophene HDS reaction involves high-temperature forms of adsorbed thiophene, while hydrogenation of unsaturated hydrocarbons (butenes) involves high-temperature forms of adsorbed hydrogen. A scheme of the thiophene HDS reaction on sulfided CoMoO₄ and technical CoMoAl₂O₃ catalysts is suggested on the basis of the results obtained.