Hydroxylation of benzene to phenol using nitrous oxide

There is an increasing commercial interest in finding alternative ways to produce phenol that overcome the disadvantages of the current cumene process used to synthesise phenol. The drivers for the change are both economical and environmental. A direct oxidation route for producing phenol from benzene is based on using N2O as an oxidizing agent in the gas phase in the presence of modified Fe-ZSM5 zeolite. A series of selective Fe-ZSM5 catalysts with different Si/Al ratios have been prepared and evaluated for selective formation of phenol. Catalysts synthesized with high Si/Al ratios (80) and with low iron content (35mg/g) showed good long term stability (reduced deactivation rates) and demonstrated good phenol selectivity and reaction rates (6 mmol/g.h). Catalysts with high amounts of iron (~500mg/g) showed considerable deactivation particularly at high reaction temperatures (450C). High reaction temperatures (450C) in comparison with 350C were found to favour higher reaction rates however, catalysts with high iron content were particularly prone to deactivation at this temperature.