Reduction of Propanoic Acid over Pd-Promoted Supported WOx Catalysts

摘要

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 WOx/TiO2, 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 WOx/SiO2 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.