MIXTURE EFFECTS AND METHANOL OXIDATION-KINETICS OVER A PALLADIUM MONOLITH CATALYST

Methanol oxidation has been investigated using a simulated methanol fueled vehicle exhaust and a commercial palladium monolith catalyst. The presence of water and CO led to severe inhibition of the methanol conversion at any temperature; propylene addition had no effect on the conversion profile. The CO inhibition is described as competitive adsorption of the CO on palladium oxidation sites. The methanol conversion was described through a Langmuir-Hinshelwood model. At low temperature, and under reducing conditions, the methanol conversion displayed a local maximum. This maximum is attributable to a shift in the oxidation state of the palladium catalyst within the temperature range of the methanol oxidation reaction. Temperature programmed oxidation and differential scanning calorimetry reveal that the catalyst changes from a relatively reduced surface at low temperature to a less active, relatively oxidized surface as the temperature is increased.