Hydroxylation/oxidation of benzene over Cu-ZSM-5 systems: Optimization of the one-step route to phenol

Cu-containing ZSM-5 materials were carefully prepared using a solid-state ion-exchange procedure to provide an outstanding performance in the direct gas-phase benzene oxidation to phenol using both oxygen and oxygen/hydrogen mixtures as oxidants. In particular, a ZSM-5 catalyst with a 100% modification level of copper (Cu/Al = 0.5) showed a phenol yield increasing with temperature up to 400 °C and approaching a high value of ca. 10%. The study shows that optimization of the phenol yield in the Cu-ZSM-5 system appears to be correlated with the appearance of size-limited Cu species, and that the presence of H2 in the feed has beneficial/detrimental effects depending on the zeolite loading with Cu.