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 semi-batch 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 min−1 and a stripping flow rate of 1 mL min−1, 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.

Scheme of continuous membrane reactor.Figure optionsDownload as PowerPoint slideHighlights
► Phenol production from direct hydroxylation of benzene in a continuous membrane reactor.
► Performance compared with a semi-batch configuration.
► Selectivity exceeding the 90%.
► Reduction by-products formation such benzoquinone and biphenyl.