The mechanism of pyridine hydrogenolysis on molybdenum-containing catalysts: I. The monolayer MoO 3Al 2O 3 catalyst: Preparation and catalytic properties

Abstract

Preparation of a MoO 3Al 2O 3 catalyst with a monolayer of molybdenum oxide on the alumina was possible by adsorbing MoO 2(OH) 2 at 600 °C from the gas phase. From the amounts of molybdenum adsorbed and the surface areas of the catalysts a characteristic value of 17 Å 2 was calculated for the area occupied by one MoO 3 molecule. Longer times of preparation and high partial pressures of MoO 2(OH) 2 yielded an aluminum molybdate (Al 2O 3 · 3MoO 3) as evidenced by X-ray analysis. High coverage of the alumina with molybdenum oxide was also possible by adsorbing polymolybdate ions from acid solutions. The dehydrogenation of cyclohexane on the prepared catalysts was studied using a pulse reactor. For the different catalysts the rate of dehydrogenation, expressed per unit weight of MoO 3, was found to be constant. Hydrogenolysis of pyridine at high hydrogen pressures on a monolayer MoO 3Al 2O 3 catalyst and a cobalt promoted MoO 3Al 2O 3 catalyst showed that both catalysts have the same activity and selectivity pattern.