Nitrogen-15 and oxygen-18 kinetic isotope effects in the catalytic decomposition of N2O over MgO

Abstract

The ¹⁵N kinetic isotope effects (KIE) in the catalytic decomposition of nitrous oxide on MgO powder were determined in the temperature range 675–875 K, and the following temperature dependence was found: KIE(¹⁵N)=(0.231±0.149)+(1353±114)/T. At initial pressures of N₂O between 40 and 60 kPa, the reaction is of the order of +1 in N₂O and has an apparent activation energy of 125±4 kJ mol⁻¹. According to the Bigeleisen formalism, the rate-determining and isotope fractionation governing step was well represented by two transition states: a bent product-like NNO and a fork-type NNOO.