Exhaust-catalyst development for methanol-fueled vehicles:: 1. A comparative study of methanol oxidation over alumina-supported catalysts containing group 9, 10, and 11 metals

Abstract

Methanol was oxidized in a laboratory flow reactor over automotive exhaust catalysts containing highly-dispersed Rh, Pd, Pt, Ag or Cu-Cr on γ-alumina beads. Experiments were carried out both in the presence and absence of a number of methanol exhaust components with emphasis given to the effects of carbon monoxide on methanol oxidation. Catalysts containing Pt and Pd oxidize methanol rapidly in the absence of CO and produce large yields of methyl formate below ~400 K. In the presence of CO, the methanol oxidation activity is strongly inhibited and methyl formate is no longer observed. H2CO yields are low over both catalysts in the presence of CO. The Rh catalyst is much less active than Pt or Pd in the absence of CO, but its activity is not greatly affected by CO. H2CO and dimethyl ether are the dominant partial oxidation products over the Rh catalyst. In contrast to the Pt and Pd catalysts, methanol oxidation over the Ag and Cu-Cr catalysts is virtually unaffected by CO. Consequently, although the Ag and Cu-Cr catalysts are much less active than the Pd and Pt catalysts in the absence of CO, their low-temperature activities are comparable to or better than those of the Pd and Pt catalysts in the presence of CO.