Oxidation of Methanol over a Palladium Monolithic Automotive Catalyst

摘要

The oxidation of methanol and its partial oxidation products, carbon monoxide and formaldehyde, were studied using a monolithic catalyst containing palladium. Experimental conditions simulated those in the catalytic converter of a methanol-fueled automobile. With a properly activated catalyst and a fuel-lean feed, carbon dioxide was the only carbon-containing product, and the methanol conversion above the light-off temperature of the catalyst appeared to be controlled by mass transfer from the bulk gas stream to the surface of the monolith. Under fuel-rich conditions, carbon monoxide and formaldehyde were formed along with carbon dioxide. The highest formaldehyde yield, about 4% of the methanol reacted, occurred at a relatively low feed temperature, about 350 K, essentially the light-off temperature of the catalyst. The formaldehyde yield decreased as the feed temperature increased and was essentially zero above about 600 K. When a thermally-deactivated catalyst was used, the formaldehyde yield increased significantly and formaldehyde was observed over a wider range of feed temperatures and under fuel-lean conditions. With the properly activated catalyst, multiple steady states were observed in the form of a reaction hysteresis with respect to feed temperature.