Low NOx options in catalytic combustion and emission control

The options for preventing the release of nitrogen oxides into the atmosphere from combustion processes is considered both from the viewpoint on the one hand of using catalytic combustion to prevent the formation of nitrogen oxides and on the other of using hydrocarbons for the selective reduction of nitrogen oxides to nitrogen in the presence of excess oxygen. Combustion of methane at low temperatures on palladium-based catalysts is discussed, and some new results relating to the nature of the active catalyst and the rate determining step are presented. Current attempts to develop selective reduction catalysts for the removal of nitrogen oxides are summarised and the particular advantages and disadvantages of platinum group metal-based catalysts are discussed. The mechanism of the nitrogen oxide to nitrogen reaction is considered and some new results are presented which are consistent with a dissociative mechanism, possibly involving adsorbate-assisted dissociative adsorption of nitric oxide.