Benzene conversion to phenol in membrane reactors

Benzene is an important precursor to produce phenol. This one, indeed, is a raw material for the synthesis of petrochemicals, agrochemicals, and plastics. Some examples of phenol employment as intermediate are: production of phenolic resins, bisphenol A, aniline, alkyl phenols and other useful chemicals. Current worldwide capacity for phenol production is nearly 7 million metric tons per year. Today, almost 95% of the worldwide phenol production is based on the so called "cumene process" but, despite its great success, this process has some disadvantages: poor ecology, an explosive intermediate (cumene hydroperoxide) and a multisteps character, which makes difficult to achieve high phenol yields with respect to benzene and results in an oversupply in the market of a high acetone production as co-product. In the chapter, we discuss various studies concerning a new approach based on one-step and acetone-free methods for the conversion of benzene to phenol. A particular attention is devoted to phenol production processes studied using various configurations of membrane reactors (MRs) and a photocatalytic membrane reactor (PMR). In particular, the biphasic membrane reactor allowed to get high selectivity values (97-98%). The various studies show that the direct oxidation of benzene to phenol is a difficult task, thus efforts to search and replace the three steps process of the traditional process to convert benzene into phenol with a process of direct oxidation must be intensified