The effect of the oxygen content in a series of manganese oxide catalysts on their catalytic activity and selectivity in the decomposition of isopropyl alcohol

Abstract

The catalytic decomposition of isopropyl alcohol vapor has been investigated from 35 to 280 °C in a flow reactor on manganese oxides of compositions varying from MnO to Mn 2O 3. The catalytic reaction products have been identified and the catalyst selectivity in dehydrogenation and dehydration calculated from the values of the reaction rates. The apparent activation energy for dehydration between 156 and 280 °C varies with the oxygen content in the catalyst series based on MnO, from 50 ± 2, stoichiometric MnO, to 56 ± 2 kcal mole −1, MnO 1.3. Two distinct apparent activation energy regions occur for the dehydrogenation reaction. Between 150 and 200 °C, the values lie from 5 to 8 kcal mole −1 while above 200 °C these become 26 to 28 ± 1 kcal mole −1. Stoichiometric Mn 2O 3 shows no dehydration activity and yields an apparent activation energy in dehydration of 15 ± 1 kcal mole −1 between 35 and 85 °C. In the discussion emphasis is placed on the role of the surface oxygen in the decomposition reactions and an interesting relationship established between the oxygen content of the catalyst and its activity in dehydrogenation.