CO adsorption at low temperatures has been used to probe Al3+ Lewis acid sites created upon dehydroxylation of AI2O3, using transmission infrared spectroscopy. AI2O3 was dehydroxylated in the temperature range from 475 to 1200 K. There is an approximate linear correlation between the decreasing integrated absorbance of the Al-OH IR features and the increasing integrated absorbance of the adsorbed CO features throughout the full coverage range of hydroxyl groups. Two CO adsorption sites have been identified: the first (vco = 2195 cm'1) appears immediately upon mild dehydroxylation, while a second site (vco = 2213 cm-1) appears after an 800 K dehydroxylation treatment. CO adsorption on the Lewis acid sites formed by dehydroxylation of AI2O3 involves a binding energy of about 21 kJ/mol.

A new design for an infrared cell useful for studies of the spectrum of surface species on high area solids is presented. The cell is well suited over a wide temperature range (100–1000 K). Other demonstrated features of the cell include ultrahigh-vacuum operation, temperature control to ±1 K, linear and rapid temperature programmability and low-temperature gradients across the powdered sample. The method of sample preparation and support minimizes both heat and mass transport effects. A detailed literature search of previous infrared cell designs is included. Results of the application of the new cell design to the high-temperature dehydroxylation of Al2O3 are given as an example of the performance.

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