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

The N-15 kinetic isotope effects (KIE) in the catalytic decomposition of ni trous oxide on MgO powder were determined in the temperature range 675-875 K, and the following temperature dependence was found: KIE(N-15)=(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 represen ted by two transition states: a bent product-like NNO and a fork-type NNOO.