The silver-oxygen interaction in relation to oxidative dehydrogenation of methanol

The interaction of unsupported silver with oxygen at atmospheric pressure and at temperatures between 100 and 600°C has been studied using temperature programmed reduction and desorption experiments with temperatures ranging up to 900°C. In addition, the interaction of an oxygen-loaded silver surface with methanol has been studied using both these techniques and temperature programmed reaction. It appears that the silver-oxygen chemistry is influenced strongly by hydrogen dissolved in the silver during the pretreatment of the catalyst, the hydrogen giving rise to a new type of sub-surface species, possibly sub-surface OH groups, and also to an increase of the amount of sub-surface oxygen formed. Sub-surface oxygen can be converted into a strongly bound species that is not present to a measurable extent after normal oxidation. Defects, partly generated as a consequence of the interaction between oxygen and hydrogen in the sub-surface region of the silver, probably generate this strongly bound oxygen species. The presence of the sub-surface oxygen species appears to activate the silver for methanol dehydrogenation.