Infrared Study of the Adsorption of Methanol and Ethanol on Aluminum Oxide

The adsorbed surface species which result when aluminum oxide is exposed to methanol or ethanol vapor have been studied. Three different surface species have been identified for both methanol and ethanol. At 35°C a weakly bound layer of liquid alcohol is observed, which is removed by evacuation. Another species which persists after prolonged evacuation is identified as a surface methoxide in the case of methanol and an ethoxide in the case of ethanol. When the alumina sample is heated to 170°C in alcohol vapor a formate-like surface compound is formed from methanol and an acetate-like compound from ethanol. This interpretation of the surface structure has been checked by using deuterated methanols and C13-enriched methanol.