Direct liquid phase hydroxylation of benzene with an inner-circulated H2-O2 mixture over Pd or Pd-V modified Hβ catalysts at ambient conditions

摘要

The direct liquid phase hydroxylation of benzene with hydrogen (H2)-oxygen (O2) mixture was achieved through a sealed gaseous inner-circulated process in the presence of Pd-V modified H catalyst. The results indicated that Pd-V modified H with an atomic ratio of V to Pd for 4 possessed the best catalytic performance and that acidic acid aqueous solution was the excellent media for direct hydroxylation of benzene with H2 and O2. Under the optimum reaction conditions, a relatively high formation rate of phenol (41.5 mmol PhOH/mmol Pd.h) and highly-efficient utilization of H2-O2 mixture as well as negligible loss of benzene volatilization could be simultaneously realized at 333 K. Besides, a synergistic mechanism was proposed to explain the favorable effects of introducing V oxides and adding water in acetic acid medium.