Infrared study of the adsorption of acetone on rutile

Abstract

The associative adsorption of acetone onto Lewis acidic Ti⁴⁺ ion sites on rutile is followed by the formation of a surface enolate complex which reacts with a further acetone molecule to give mesityl oxide. The enolate is also an intermediate in the exchange of hydrogen atoms between acetone and hydroxyl groups on rutile. The effects of dehydroxylation and dehydration of the rutile surface on the associative adsorption of acetone and on the formation of the enolate complex and mesityl oxide have been studied using infrared spectroscopy. The reversibility of the surface reactions has been established, in part by a study of the adsorption of mesityl oxide, which not only associatively adsorbs onto Ti⁴⁺ ion sites but also decomposes to enolate complex and coordinatively liganded acetone molecules. Reduction of rutile in hydrogen decreases the Lewis acidity of the oxide surface but promotes the formation of surface acetate ion by the chemisorption of acetone.