By-product co-feeding reveals insights into the role of zinc on methanol synthesis catalysts

Abstract Co-feeding of two relevant by-products of methanol synthesis, viz. dimethyl ether and methyl formate, in CO + H 2 and CO + CO 2  + H 2 streams was used as a strategy to gain understanding of the reaction over ternary Cu/ZnO/Al 2 O 3 and binary Cu/ZnO, Cu/Al 2 O 3 , and ZnO/Al 2 O 3 catalysts. While dimethyl ether does not participate in the process, the addition of methyl formate remarkably increases the MeOH production by its oxygen-assisted split into active intermediate species (CH 3 O ⁎ and HCOO ⁎ ). Specifically, a breakthrough role was assigned to ZnO as catalytic partner for methyl formate conversion to methanol, since even the Cu-free ZnO/Al 2 O 3 sample shows a considerable MeOH yield on MeF co-feeding. Alternatively, in the Zn-free Cu/Al 2 O 3 sample, the presence of carbon dioxide in the inlet mixture was crucial to activate the methyl formate conversion path, likely because CO 2 provides readily available oxygen to the Cu surface.