One-step hydroxylation of benzene to phenol using N2O

There is an increasing commercial interest in finding alternative ways to produce phenol that overcome the disadvantages of the current cumene process used to synthesize phenol. The drivers for the change are both economic 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. One of the main objectives was to examine the effect of different Si/Al ratios, temperatures and iron content on the selective conversion of benzene to phenol with a desire to achieve high selectivity and minimise catalyst deactivation. Also one of the research objectives was to identify the active sites in the catalyst and design the catalyst which is able to delay coke formation. The methodology was to incorporate iron directly at extra-framework positions via liquid ion-exchange. In this project, a series of selective Fe-ZSM5 catalysts with different Si/Al ratios have been prepared and evaluated for selective formation of phenol. The catalyst samples were characterized (by Atomic Absorption Spectroscopy (AAS), Malvern mastersizer and Nitrogen adsorption using N2 at 77 K via Micromeritics to determine the elemental composition, average particle size, BET surface area and pore size distribution) and their catalytic activities compared. A quantitative comparison between the number of active sites using isopropylamine decomposition method shows that active sites increase as the Si/Al ratio increased and also as the iron content increased. (Continues...).