(560gh) Metal Oxide Catalysts for Low Temperature NOx Adsorption

The increasing efficiency of automotive engines has resulted in lower exhaust temperatures. Such improvements call for enhanced after-treatment systems to mitigate NO_x emissions, particularly in the cold start period with the exhaust temperature in the range of 100-200 ^oC. However, the state-of-art commercial deNOx catalysts for diesel vehicles are only effective at temperatures above 200 ^oC. This work tries to formulate a catalyst which can adsorb and store NO in the form of metal-nitrates below 200 ^oC and subsequently release NO₂ in 200-400 ^oC regime, where commercial deNOx catalysts eliminate it effectively. Thermogravimetric analysis results show that nitrates of copper, cobalt and lanthanum supported over alumina are stable at temperatures below 200 ^oC, but totally decomposed to NO₂ in the 200-400 ^oC window. This indicates the potential application of these base metal oxides in NO adsorption at low temperatures. In order to accelerate the adsorption of NO and transformation to metal-nitrates at low temperatures, an additional active metal which oxidizes NO to NO₂ will be combined with alumina supported copper oxide, cobalt oxide and lanthanum oxide. The insights drawn from this study will be useful in the design of low-temperature NO adsorption catalysts formulated with base metals.