Epoxidation of cycloalkenones over amorphous titania-silica aerogels

Epoxidation of alpha- and beta-isophorone was studied using t-butylhydroperoxide and a titania-silica catalyst containing 20 wt% titania. The mixed oxide was prepared by the sol-gel aerogel technique. Good activities and high selectivities (up to 94 - 99 %) could be achieved. The activity of the aerogel in the epoxidation of alpha-isophorone was compared to the performance of titania-silica xerogel, Mg-Al-hydrotalcite and KF/alumina catalysts. Acid-catalyzed side reactions during the epoxidation of beta-isophorone (isomerization to alpha-isophorone and epoxide ring opening) could be suppressed by treatment of the aerogel with a weak base. The influence of solvent, temperature and peroxide structure on the performance of the titania-silica aerogel is discussed.