Kinetic modeling of selective catalytic reduction of NOx with octane over Ag–Al2O3

A kinetic model for the selective catalytic reduction of NOx with octane over a Ag–Al2O3 catalyst was developed. Analysis of experimental data indicated that feed concentrations of NO and hydrogen had significant effects on the NOx conversion, indicating that nitrates poisoned the catalytic sites and hydrogen's role was to reduce nitrate species. As a result nitrate poisoning was a key component of the kinetic model. Also in the model, gas phase n-octane reacted with surface oxygen to form surface hydrocarbon intermediate species that could either reduce surface NO2 species to nitrogen or be fully oxidized. An additional site was included in the model on which various oxidation reactions occurred when the NOx reduction site was fully poisoned by nitrate species. The model also accounted for experimentally observed large temperature increases due to hydrogen oxidation, during hydrogen feed. The model was constructed from transient experimental data, both with and without hydrogen feed and from a range of reactant concentrations and temperatures.