Gold Catalysts, Along with Catalyzed HC Traps: Low Temperature Exhaust Emission Control

Abstract

The demand of stringent environmental laws on exhaust emission and the manufacturers' growing desire to cut down the total cost of the catalytic converter by employing lesser amounts of precious elements, needs for the development of improved catalytic exhaust treatment devices. Till now the converters in practice consist of Pt group metals as catalysts, which inherently have very high light-off temperatures for CO oxidation, around 150°C to 300®C [1], which in turn is the major pollutant of the exhaust emissions. This is where Au particles exhibit their importance, accounting to their inherent property to stimulate the oxidation reactions at even below room temperature. This article discusses the exhaust treatment device developed by Moroz et al., with Au nanoparticles as the prime component and explains why it is better than the other patented methods used for the purpose. Brief comparisons are made between these patents. Also discussed are the factors stimulating low temperature CO oxidation on Au catalyst, the reaction mechanism and how it is different from that on Pt group metals, and the use of catalysed HC trap to reduce the HC inhibition of catalytic activity.