Microstructured Au/Ni-fiber catalyst: Galvanic reaction preparation and catalytic performance for low-temperature gas-phase alcohol oxidation

The highly active and selective gold catalysts were successfully prepared by galvanically depositing Au onto a thin-sheet microfibrous structure consisting of 5 vol.% 8-μm Ni-fiber and 95 vol.% voidage, with high heat conductivity and good stability for the gas-phase oxidation of alcohols. The best catalyst was Au-4/Ni-fiber-300 (Au-loading: 4 wt%; calcined at 300 °C in air), being effective for oxidizing acyclic, benzylic, and polynary (1,2-propanediol) alcohols. For benzyl alcohol, the conversion of 95% was achieved with 99% selectivity to benzaldehyde within 660 h test at 250 °C, while a low ΔT of <10 °C between catalyst bed and reactor external wall was observed. Transformation of NiCl₂ formed at Au galvanic deposition step into NiO was identified along with the low-temperature activity promotion. This suggests a special synergistic effect between NiO and Au particles, of which comprehensive understanding is particularly desirable.