Isotopic study of ethanol dehydrogenation over a palladium membrane

• The dehydrogenation of ethanol and the subsequent permeation were studied on a Pd membrane in a continuous ethanol supply. Hydrogen could not be extracted as efficiently from ethanol as from methanol. In ethanol, at least four of the six hydrogen atoms were not available for permeation because of methane formation. Hydrogens bonded to a carbon atom in a C-O group were available for permeation, while hydrogen atoms bonded to a carbon atom without oxygen were not. The efficiency of hydrogen permeation from ethanol was 5% compared to that of pure hydrogen, which could be compared to 25% for methanol compared to pure hydrogen. The hydrogen permeation could be enhanced by adding CO to the EtOH + O2 supply. The permeation probability of the hydrogen bonded to the methylene hydrogen increased while the water formation with this hydrogen atom decreased. Acetic acid was formed upstream when oxygen was in excess. The differently bonded hydrogen atoms in an ethanol molecule experienced different reaction pathways. The results did not contradict the models made from surface experiments in ultrahigh vacuum by Davis and Barteau, Holroyd and Bowker, or Bowker et al.

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