Influence of alkali carbonates on benzyl phenyl ether cleavage pathways in superheated water

Benzyl phenyl ether conversion in superheated water yields a broad product distribution. In addition to the hydrolysis products, phenol and benzyl alcohol, a large amount of consecutive products are formed depending on the operating conditions. The influence of Li2CO3, Na2CO3, and K2CO3 on these reactions is explored between 270 and 370 °C. It is shown that high selectivity towards hydrolysis can be achieved at low temperatures and short reaction times. At higher severities the yields of phenol and especially benzyl alcohol decrease and higher molecular weight compounds are formed by consecutive reactions. Alkali carbonates effect this distribution by decreasing the concentration of protons in the system and by providing and enhancing parallel and secondary reaction mechanisms. The yields of toluene, 2 and 4-benzyl phenol are strongly enhanced in the presence of an alkali carbonate, by formation of a cation–BPE adduct in which the ether bond is strongly polarized.