INTERMEDIATE SPECIES ON ZIRCONIA SUPPORTED METHANOL AEROGEL CATALYSTS.2. ADSORPTION OF CARBON-MONOXIDE ON PURE ZIRCONIA AND ON ZIRCONIA CONTAINING ZINC-OXIDE

On pure ZrO2 and on ZnO/ZrO2 aerogels carbon monoxide interacts with t he surface hydroxyl groups to form surface formate species. This speci es is relatively stable on pure ZrO2 where it is decomposed at increas ing temperatures either resulting in regeneration of carbon monoxide a nd of surface OH's or in carbon dioxide and hydrogen. Only this second path is observed on ZnO/ZrO2 aerogel and it is paralleled by the form ation on the surface of carbonate type species like unidented carbonat e, carboxylate and ionic carbonate. This difference in the fate of the formate species onto the previous catalysts may bear some connection with the controversial problem of the pivotal species in the methanol synthesis, the formate of the carbonate type species.