Use of Fluidized Bed Reactors for Direct Gas Phase Oxidation of Benzene to Phenol

A study on the direct gas phase oxidation of benzene to phenol over a Pt-VOx/SiO2 catalyst was carried out in both a conventional fluidized bed reactor (FBR) and a two-zone fluidized bed reactor (TZFBR). For this purpose, Pt-VOx/SiO2 catalyst was synthesized by a method based on two consecutive impregnations. In the FBR, the effect of the main operating variables was studied: temperature, H-2/O-2 ratio, and relative gas velocity (u/u(mf)) in order to obtain the optimal conditions. Furthermore, two configurations in a TZFBR were tested feeding the reactants separately: benzene and hydrogen or oxygen at the middle of the bed, and oxygen or hydrogen at the bottom, respectively. Depending on the TZFBR configuration, the selectivity was tailored to obtain different products. The use of TZFBR allowed the production of phenol, cyclohexanone, or cyclohexane in the same reactor simply by changing the point where every reactant was introduced. Phenol selectivity near 100% was obtained in one of the configurations studied. Continuous operation without catalyst deactivation was observed.