Control of unregulated emmissions from ethanol-fluelled diesel engines—A study of the effect of catalyst support on the low temperature oxidation of ethanol and acetaldehyde using precious metals

Abstract

Catalytic oxidation of ethanol and acetaldehyde over precious metal catalysts applied on monolithic cordierite substrates was studied. Platinum or palladium were applied onto a support consisting of either aluminum oxide, cerium dioxide, silicon dioxide or titanium dioxide. The catalysts were tested in a quartz reactor in synthetic exhaust from ethanol-fuelled diesel engines using mixtures of bottled gases. The catalysts were characterized using techniques such as BET surface area measurement, gas porosimetry, hydrogen-oxygen titration, pulse chemisorption of carbon monoxide, and X-ray diffraction. The effect of support material on the low temperature oxidation of ethanol and acetaldehyde in the presence of nitric oxide and carbon monoxide was investigated. The results indicate that the choice of support material influences the activity and the product distribution in catalytic oxidation of ethanol. Both platinum and palladium are active materials for ethanol oxidation, but the selectivity for acetaldehyde production is high at low temperatures. The selectivity for acetic acid formation is low for the palladium catalysts. The yield of acetic acid in the platinum catalyst experiments is of the same magnitude as the odour threshold. Acetic acid is not formed via oxidation of acetaldehyde.