Kinetic study of the selective oxidation of butan-2-one to diacetyl over vanadium phosphorus oxide

The selective oxidation of butan-2-one to diacetyl has been studied in the temperature range 200-380°C over a vanadium phosphorus oxide catalyst. In addition to diacetyl the principal reaction products detected were acetic acid, acetaldehyde, methyl vinyl ketone, propionaldehyde and carbon dioxide. A kinetic analysis indicated that diacetyl formation proceeds through a Mars and van Krevelen type mechanism and that there were two sources of acetaldehyde formation; the first predominating at high oxygen partial pressures involved an enol intermediate and adsorbed molecular oxygen; the second, which predominated at low oxygen partial pressures involved lattice oxygen and a diol intermediate. It is also proposed that acetoin, CH₃COCHOHCH₃, is a common intermediate in the formation of diacetyl and methyl vinyl ketone. High selectivities to diacetyl can be achieved by operation in anaerobic conditions.