Reduction of Propanoic Acid over Pd‐Promoted Supported WO x Catalysts

Abstract Silica‐, titania‐, and zirconia‐supported tungsten oxide catalysts were synthesized by wetness impregnation techniques. When promoted with Pd, these materials catalyzed the reduction of propanoic acid to 1‐propanol at 433 K with a selectivity of up to 92 % (13.5 % conversion) in atmospheric pressure of H 2 . Over Pd‐promoted WO x /TiO 2, the observed orders of reaction were 0.2 in H 2 and 0.7 in propanoic acid, and the apparent activation energy was 54 kJ mol −1 . In situ X‐ray absorption spectroscopy of Pd‐promoted WO x /SiO 2 revealed a slight reduction of the W from +6 to an average oxidation state of about +5 during H 2 treatment above 473 K. In situ infrared spectroscopy indicated the catalyst surface was covered mostly by propanoate species during reaction. For comparison, supported phosphotungstic acid was also evaluated as a catalyst under identical conditions, but the resulting high acidity of the catalyst was deleterious to alcohol selectivity.