Liquid phase benzene hydroxylation to phenol using semi-batch and continuous membrane reactors

Liquid phase phenol production by direct hydroxylation of benzene with H2O2 was studied in a semibatch membrane system and in a continuous membrane reactor. In these systems the phenol produced was recovered by using water on the stripping side of the membrane unit. The influence of the hydrophilic and hydrophobic character of the membrane material on the phenol recovery was investigated at different flow rates of the feed and the stripping phases. Better performance was achieved using a hydrophilic membrane, with a total feed flow rate of 2 mL min1 and a stripping flow rate of 1 mL min1, in terms of phenol recovery (25%) and selectivity (94%). In addition the continuous removal of the phenol from the reaction side reduces the possible formation of by-products such as benzoquinone, avoiding completely biphenyl formation that was not detected in all the tests carried out in the continuous mode.