Microkinetic Analysis for the Reduction of Nitric Oxide over Palladium in the Absence of Oxygen

utilizing the stochastic simulation, a microkinetic model that quantitatively describes the reduction of no by h-2 in the absence of 02 is developed. the parameters of elementary reaction steps are calculated by the transition state theory along with the unity bond index-quadratic exponential potential method. it is shown that no adsorbed in a dimer form (no)* on the pd(100) surface. n2o can be produced via two routes, one is the decomposition of (no)(2)* and another is the combination of adjacent no*. n-2 is formed from the decomposition of n2o*. while nh3 comes from the hydrogenation of hno*. with the increase of reaction temperature, the coverage of h* on the pd surface decreases, and the rate-limiting step also changes, which has obvious influence on the selectivity for different reduction products. from 70 degrees c to 310 degrees c, the simulated results are in accordance with the experimental data. n2o is the major reduction product via the decomposition of (no) towards n2o* at low temperature, and nh3 is obtained via the hydrogenation of (no); towards hno* at high temperature. so the selectivity for n-2 increases at first and then decreases with a maximum below 50%. according to the experimental and simulated results the reaction mechanism is suggested.