The activity in the WGS reaction of Cu/ZrO2 catalysts prepared by a method of refluxing in an aqueous NH4OH solution is studied. It is shown that at 3% Cu load the methods of impregnation over monoclinic or tetragonal ZrO2 do not produce active catalysts for the WGS reaction. However, the method of refluxing generates highly active catalysts with Cu loads of 3% (w/w) or higher. The activity of the catalysts prepared by refluxing is associated with the formation of small Cu clusters, which would allow the regrouping of the H atoms to generate molecular H2 in the presence of the crystalline tetragonal ZrO2.
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Financial support under Fondecyt Project 1110184 is gratefully acknowledged as well as the kind donation of hydrous zirconia from MEL Chemicals.