The hydrogenolysis of propane on [formula omitted] catalysts

Abstract

Metallic molybdenum on dehydroxylated alumina (prepared by impregnating Mo(CO) 6 onto alumina which had been dehydroxylated in flowing helium at 950 °C and then treating the Mo(CO) 6 Al 2O 3 by He,300–500 °;H 2,650–950 °) is one of the more active catalysts for the hydrogenolysis of propane. Its turnover frequency per surface Mo atom at 250 °C is ~0.2 sec −1 at P = l atm and C 3H 8 H 2 = 0.038. Both single and double hydrogenolyses occur simultaneously, the latter having the larger apparent activation energy. Mo Al 2O 3 catalysts with higher oxidation numbers of molybdenum are less active. Mo(0) Al 2O 3 is easily poisoned for hydrogenolysis by O 2, CO, H 2O, and even to some extent by N 2. Initial activity is restored by H 2 at ~950 °C. MoO 3/hydroxylated alumina is reduced by H 2 at 650 °C to an average ON (oxidation number) of Mo of +2 and by 800–950 °C to an ON of zero. The catalytic activities of these materials for the hydrogenolysis of propane at 200–300 °C, the hydrogenation of propylene at −46 °C, the metathesis of propylene at 65 °C, and the hydrogenolysis of cyclopropane at 0–100 °C are very nearly the same as those of Mo 2+ Al 2O 3 and Mo(O) Al 2O 3 made from Mo(CO) 6 Al 2O 3 .