The Infrared Study of the Adsorption of Ethanol on Alumina

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Abstract
The structure of ethanol adsorbed on alumina has been studied by means of infrared spec-troscopy. At room temperature physically-adsorbed ethanol was observed, but it was completely removed by evacuation at 70°C for 2 hr. On the contrary, another adsorbed species remained after long evacuation at 70°C; it was identified as a surface ethoxide (C2H5OAl<). The concentration of the surface ethoxide on alumina had a linear correlation with the intensity of the CH3 symmetric deformation band at 1387 cm−1. The molar absorption coefficient of the band at 1387 cm−1 decreased parallel with 1/T at a higher temperature. The number of adsorption sites was calculated as 2.1×1014 sites/cm2 when the ethanol was exposed at 70°C to an alumina catalyst which had been evacuated at 550°C for 5 hr.