Zinc and manganese promoted silica supported copper catalysts show an activity increase in methyl acetate hydrogenolysis and methanol synthesis after high temperature reductive treatments. The effect of reduction can largely be reversed by applying a treatment in an inert atmosphere at reduction temperature, which results in a decrease in copper surface area as measured by N2O chemisorption and which is accompanied by distinct changes in the XRD pattern of the catalyst. These phenomena could be explained with a model assuming the reversible formation of epitaxial, two-dimensional, copper particles on top of a mixed oxide phase.