Thin-sheet microfibrous-structured nanoporous gold/Al fiber catalysts for oxidative coupling of methanol to methyl formate

Active, selective, and stable nanoporous gold (NPG) catalysts supported on Al fiber, with enhanced heat transfer, have been developed for the oxidative coupling of methanol to methyl formate. The NPG/Al fiber catalysts are obtainable by galvanically depositing AuAg alloy on a thin-sheet microfibrous structure using 50-μm Al fiber and subsequently dealloying by leaching Ag using HNO₃ aqueous solution. At 100 °C, NPG-7/Al fiber (Au loading: 7 wt%) catalyst is capable of achieving ∼100% methyl formate selectivity with ∼25% methanol conversion of a 10 vol% methanol feed at 5000 mL g_cat.^-1 h^-1. Gold loading can be reduced to 1 wt% with acceptable reactivity (35% conversion with 85% selectivity at 160 °C). The catalyst is stable for at least 300 h without NPG sintering. Lowering the Ag residual content of the NPG catalysts is essential for higher selectivity of methanol, by nature, due to the reduction in the amount of unselective surface O species.