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Keywords:

  • alcohols;
  • copper;
  • electrochemistry;
  • gold;
  • heat transfer

Abstract

The highly active and selective gold-on-copper fiber catalysts with excellent heat conductivity were successfully prepared for high-efficiency gas-phase selective oxidation of various alcohols. The Au/Cu-fiber catalysts were obtained by conducting galvanic deposition of Au onto a thin-sheet microfibrous structure that consisted of 5 vol % Cu-fiber (8 μm diameter), and 95 vol % voidage. The best catalyst was Au-3/Cu-fiber-200 (Au loading: 3 wt %; calcined at 200 °C in air), which was effective for acyclic, benzylic, and polynary alcohols using a high weight hourly space velocity of 20 h−1. Benzyl alcohol conversion of 86 % was obtained with 99 % selectivity to benzaldehyde at 220 °C. Cyclopropanemethanol could be transformed to cyclopropanecarboxaldehyde, with conversion of 91 % and selectivity of 95 % at 250 °C. 1,2-Propanediol demonstrated a high conversion of 92 %, with a medium selectivity of 74 % at 340 °C. An oxidation of volatile unsaturated alcohols, such as crotyl alcohol and 3-methyl-2-butenol, could also proceed highly selectively with good conversions at 280 °C. A low ΔT of less than 10 °C between the catalyst bed and the external wall of the reactor was observed in the selective oxidation of benzyl alcohol owing to the enhanced heat-transfer ability that permits rapid dissipation of large quantities of the reaction heat. Special AuCu(alloy)–Cu2O active composites were formed during the reaction, and their cooperative effect contributed to increasing the low-temperature activity. By nature, the AuCu alloy can catalyze the oxidation of Cu2O–H species with O2 to release active Cu2O sites.