Liquid-phase ethylbenzene oxidation to hydroperoxide with barium catalysts

Barium compounds (barium oxide, barium acetylacetonate, barium nitrate) have been used as catalysts for the liquid-phase oxidation of ethylbenzene with molecular oxygen. Ethylbenzene hydroperoxide (EBHP) was the major product, although small amounts of acetophenone (ACP) and 1-phenylethanol were also formed, indicating that C-H bond activation takes place only at the alkyl chain. For barium oxide, the rate of EBHP formation was found to increase with the barium concentration up to 1 ppm Ba, thereafter decreasing at higher concentrations. The type of barium compound influenced the rate of EBHP formation to a significant extent. As a general rule, non-basic barium salts, such as nitrate and acetylacetonate, led to a decrease in the EBHP yield and also to a decrease in ethylbenzene conversion; although in the latter case it was less marked. This finding can be interpreted as being due to the partial decomposition of EBHP, under the experimental conditions employed in the present work, into ACP and 1-phenylethanol.