Kinetics of ammonia oxidation over Pt foil studied in a micro-structured quartz-reactor

Abstract

The kinetics of Pt-catalyzed ammonia oxidation on polycrystalline Pt were investigated at partial pressures of ammonia and oxygen up to 6 kPa and temperatures between 286 and 385• C, applying a micro-structured reactor that ascertained temperature control of the exothermic reaction. Using literature-based mechanistic models, a micro-kinetic model was derived based on parameter optimization and a model discrimination procedure. The model described the rates of formation of all nitrogen-containing products, i.e. N 2 , N 2 O and NO. Catalyst characterization of platinum samples by electron microscopy indicated that reaction-induced restructuring of the Pt surface limited the accuracy of derived kinetic parameters already at the low temperature applied in this work. Despite of necessary simplifications, the best-fitting kinetic model predicted reasonable product selectivities for the reaction conditions of an industrial ammonia burner.

NH3-Slip Catalysts: Experiments Versus Mechanistic Modelling

“…In a first step we want to test how well the literature mechanism [8] extrapolates, without further parameterization, to automotive exhaust conditions. The only adjustable parameter here is the concentration of active sites or the platinum dispersion.…”

“…The simulations presented in this work are based on the reaction network of Krähnert et al [8]. The reactions are listed in Table 1 …”

“…Additionally the observations are supplemented by quantum chemistry [1][2][3]. Based on these results a number of mechanistic models have been developed [4][5][6][7], the most recent one being the mechanism of Krähnert et al [8]. This mechanism forms the basis for our simulation work on NH 3 -slip catalysts.…”

Selective Oxidation of Ammonia by Co-adsorbed Oxygen on Iridium Surfaces: Formation of N2O

“…Selective catalytic oxidation of ammonia is one of the most important heterogeneous catalytic processes [1], which has received increasing interest [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The reaction proceeds through the three competing pathways to yield N-containing products of N 2 , NO and N 2 O.…”

The O2 + NH3 Reaction Over Rh(110): Steady State Kinetics and Oscillatory Behavior

“…Ammonia reacts with oxygen to form the main products N 2 , NO, and H 2 O [1][2][3]. On Pt at elevated pressures (p [ 10 -2 mbar) a minor amount of N 2 O is also formed during ammonia oxidation [23]. The main reactions pathways are the following:…”