Bimetallic Bi-Pt, Ru-Pt and Ru-Pd and trimetallic catalysts for the selective oxidation of glyoxal into glyoxalic acid in aqueous phase

Various bi- and trimetallic associations have been tested as catalysts for the selective oxidation of glyoxal into glyoxalic acid in aqueous phase. All catalysts were supported on carbon and consisted of a noble metal (Pd or Pt) in association with a second (or third) metal acting as promoter (Ru or Bi). Out of all the possible combinations, some families of catalysts were selected as interesting candidates and a detailed kinetic study was undertaken, in order to determine the rate constant associated with the formation of glyoxalic acid. In particular, the BiPt/C catalysts gave very high activity, but low selectivity (due to over-oxidation to oxalic acid), the PdRu/C catalysts gave the highest yields in glyoxalic acid, but with long reaction times and a marked sensitivity to the preparation procedure, while the trimetallic catalysts gave high yields in relatively short periods of time.