THE EFFECT OF THE REACTION MEDIUM ON THE SURFACE-COMPOSITION AND VALENT STATE OF COPPER IN A COMMERCIAL COPPER-ZINC-ALUMINUM CATALYST FOR METHANOL SYNTHESIS ACCORDING TO XPS DATA

The effect of the reaction medium (CO + H-2, CO2 + H-2, and CO + CO2 H-2) on the surface composition and valent state of copper at the sur face of a commercial copper-zinc-aluminum catalyst SNM-1 for methanol synthesis is studied by XPS for the first time. Upon catalyst reductio n in hydrogen, its surface is found to contain only Cu(O). On catalyst exposure to the CO2 + H-2 mixture, Cu(O), Cu(I), and Cu(II) are shown to coexist at the surface. After treating the catalyst with the CO H-2 mixture, copper is present in the Cu(O) state, and the addition of CO2 does not change the valent state of copper. It is concluded that the active sites of the catalysts for methanol synthesis may be Cu(O) and Cu(I). It is shown that the Zn/Cu atomic concentration ratio depen ds on the gas medium composition, The action of the He + 2% O-2 oxidiz ing mixture on the reduced catalyst enhances the surface content of co pper several times.