Oxidative dehydrogenation of aqueous ethanol on a carbon supported platinum catalyst

The kinetics of the selective oxidative dehydrogenation of ethanol to ethanal over a platinum on graphite catalyst with oxygen in water was investigated in a three-phase continuous stirred tank reactor by variation of temp., pH and reactant concns. No effect of the pH on the disappearance rate of ethanol was obsd. The oxidn. proceeds by a sequence in which ethanal and ethanoate are formed successively. The reaction kinetics of the oxidative dehydrogenation of ethanol to ethanal can be described adequately by a relatively simple rate equation based on an irreversible dissociative adsorption of oxygen and an equilibrated dissociative adsorption of ethanol on the same type of sites. The dissociative adsorption of ethanol proceeds by abstraction of the hydroxyl hydrogen. These steps are followed by an irreversible surface reaction between the ethoxy and the oxygen surface species. At typical conditions, i.e. a temp. of 324 K, an ethanol concn. of 500 mol m-3, a pH of 8, and an oxygen partial pressure of 50 kPa, the fractional surface coverages amt. to 0.25 for oxygen and 0.11 for both ethoxy species and hydroge