Catalytic decomposition of nitrous oxide on transition metal exchanged sodium-A zeolites

Abstract

The catalytic decomposition of nitrous oxide (2N2O → 2N2+ O2) has been studied on four series of Na-A zeolites exchanged with varying quantities of cobalt, copper, nickel and manganese. Decomposition obeys first-order kinetics without oxygen retention on all catalysts studied. All zeolites except those containing copper show linear Arrhenius plots. The rate-determining step in N2O decomposition is suggested to be electron transfer from the zeolite to adsorbed nitrous oxide. Activation energies are markedly higher for sieves containing an average of only one transition metal ion per unit cell compared with those where the transition metal ion content exceeds 1.5 per unit cell. This is also considered to reflect variation in the electronic properties of the catalysts with transition metal ion content. Transition metal ion exchanged zeolites are very much less active for N2O decomposition than bulk oxides or solid solutions but are of similar activity to transition metal ion exchanged X zeolites.