Abstract
The methanol oxidation reaction on the catalysts of Pt, Pd, Rh, Ir, and Cu has been investigated to select suitable catalysts for the purification of methanol engine exhaust gases. For all of these catalysts, the presence of NO showed an inhibitory effect on the methanol oxidation reaction and caused the formation of formaldehyde. By comparison with other exhaust components (CO, H2O, HC), it was found that NO had a stronger effect than those components. In the presence of NO, the relative activity sequence was also obtained as Pt≒Pd>Rh≒Ir>Cu. The temperature conditions for formaldehyde formation were revealed for each catalyst in the presence of NO, and it was also found that formaldehyde formation was suppressed the most by using the Pd catalyst. Consequently, Pd is a catalyst which is superior for reducing unburned methanol.
