The influence of NO{sub}x on the oxidation of metal activated diesel soot

摘要

The influence of NO on the oxidation of metal (cerium, copper and iron) activated soot was studied. Without NO in the gas phase the activation energy of soot is approximately 170 kJ/mol, independent of the type of metal applied in the soot. Therate-limiting step in the oxidation with oxygen is probably the decomposition of surface oxygen complexes. In presence of NO the oxidation rate of soot mixed with a supported platinum catalyst is increased significantly, especially for cerium activatedsoot. The activation energy of the oxidation reaction is decreased by the presence of NO in the gas phase. The increase in reaction rate as a result of NO and a platinum catalyst is explained by a cycle of two catalytic reactions, where platinum oxidisesNO to NO{sub}2, which subsequently oxidises snot using cerium as a catalyst, forming NO which can participate in tile reaction more than once. This oxidation mechanism can be put into practice by combining a platinum activated particulate trap with acombination of platinum and cerium fuel additives. This combination might be a breakthrough in the search for an applicable catalytic soot removal system.