Nitrogen oxides (NOx) are some of the most toxic and abundant air pollutants produced by combustion processes in automotive internal combustion engines, power plants, and other industrial processes. The selective catalytic reduction by ammonia (NH3 SCR) of NOx using metal-exchanged zeolite catalysts is an efficient means of converting these contaminants into environmentally benign products (N2 and H2O), and it is an important technology implemented now for emission control of diesel engines. The NO/NO2 feed ratio to the SCR catalyst has an important effect on the overall conversion of NOx, and conditions that lead to �fast� SCR have been reported for reaction mixtures with an equimolar NO/NO2 ratio as opposed to those with only NO or NO2. Typical NOx emissions from combustion processes contain much more NO than NO2, and the inclusion of an NO oxidation step prior to the SCR process is useful for increasing SCR rates of reaction.We will show that NO oxidation is catalyzed by chabazite zeolites in the proton (H+), sodium (Na+) and siliceous forms, by microporous carbons and by the metal-organic framework (MOF) material Basolite A100� at temperatures between 298 K and 423 K. We have investigated the kinetics of the reaction using reactor studies and conclude that the role of these materials is to stabilize a transition state of composition [N2O4]� within the micropores through Van der Waals forces and electrostatic interactions. Analysis of kinetic parameters using Transition State Theory is consistent with a gas-phase-like reaction mechanism within the materials' micropores.

Investigation of the low temperature NO oxidation reaction mechanism over microporous materials

247th National Meeting (2014)

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