Aldol condensation of acetaldehyde to form high molecular weight compounds on TiO 2

Abstract

Temperature-programmed desorption, hydrogenation, and oxidation are used to show that acetaldehyde undergoes continued aldol condensation beyond crotonaldehyde formation on Degussa P-25 titania to form hexan-2,4-diene-al and higher molecular weight compounds containing conjugated C=C bonds. Aromatic compounds also form, and at higher temperatures coke forms. Degussa P-25 TiO2 has more sites that catalyze chain propagation reactions beyond formation of C4 species than do pure anatase or rutile surfaces. These reactions may be responsible for deactivation observed during photocatalytic oxidation of acetaldehyde at elevated temperatures.