| Popis: |
The performance of gold/graphite as an oxidation catalyst has been investigated in an electrochemical cell (electrooxidation at ambient temperature and pressure) and in a high pressure reactor (conventional catalytic oxidation typically at 3 bar and 333 K). A range of gold/graphite catalysts having various metal loadings were prepared and characterised by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The technique of lead underpotential deposition (Pdupd) was used to reveal the presence of {111}, {100}, and {110} facets in the surfaces of the gold microcrystals. Oxidation of 1-propanol to propionic acid, of 2-propanol to acetone, and of glycerol to wide range of products was investigated both in electrooxidation and in conventional catalytic oxidation. Variation of the surface morphology of the gold active phase was achieved by (i) thermal annealing and sintering of the catalysts under air and under hydrogen, (ii) deposition of bismuth onto the gold surface, and (iii) preparation of further catalysts in which Au was deposited onto Pt/graphite. Conventional catalytic oxidation of the 1-propanol, 2-propanol, and glycerol over the full range of gold-containing catalysts is reported. Variations in catalyst structure were accompanied by changes in activity and selectivity, indicating that these reactions were indeed structure sensitive. However, few correlations of these experimental outcomes with the surface states identified by the voltammetric techniques were evident. |
