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An in situ infrared investigation was conducted using four basic adsorbates to identify the acidic sites present onand aluminas. For two adsorbates, pyridine and 2,6-lutidine, adsorption studies were conducted between 298 and 983 K and at adsorbate pressures from 1.33 Pa (Pascal) to 1.33 kPa. The adsorption of acetonitrile and n-butylamine was conducted at 298 K by using adsorbate pressures from 0.66 to 8.65 kPa. Lewis acid and hydrogen-bonded complexes were identified on both aluminas for three adsorbates: acetonitrile, pyridine, and 2,6-lutidine. Using n-butylamine as the probe molecule, complexes for Bronsted, Lewis, and hydrogen-bonded sites were identified onand aluminas. Results from a calorimetric study of the aforementioned adsorbates and adsorbents are also discussed.

In situ infrared spectroscopy was used for studying the adsorption of normal and isotopically labeled acetone on partially dehydroxylated alumina. Assignment of infrared bands to the surface species includes adsorbed acetone, acetone enolate, mesityl oxide, and isophorone. Acetone enolate is very reactive on the surface and is only observed during the initial adsorption of acetone at 300 K. For isotopically normal acetone, the enolate band is observed at 1595 cm'1. A small shift from this value is observed for acetone-d6, and [2-13C]acetone shows the C=C stretch of the enolate at 1570 cm'1. Exchange of residual protons from surface hydroxyl groups with deuterium of acetone-d6 occurs concurrently with enolate formation.One of the most fruitful methods for the investigation of catalytic oxides is the adsorption of probe molecules which react specifically with acid or base sites on the surface.1 The surface reaction may be monitored by infrared spectroscopy or NMR, by observing changes either in the probe molecule or in the composition of the surface. Acetone is generally considered inappropriate as a probe molecule due to its chemical reactivity on metal oxide surfaces.1 In our laboratory we have observed that acetone

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