Platinum catalysed wet oxidation of phenol in a stirred slurry reactor. The role of oxygen and phenol loads on reaction pathways

The catalytic wet oxidn. of phenol was studied in a slurry phase continuous stirred tank reactor (CSTR) using platinum on graphite support as a catalyst. The investigation was carried out in the temp. range 120-180 DegC and at total pressure of 1.8 MPa, while the phenol feed concn. was varied between 5 and 70 mol/m3, and oxygen partial pressures between 0.01 and 0.8 MPa. It was found that both the oxygen load and the stoichiometric oxygen excess det. the extent of oxygen coverage on the platinum surface, which influences the reaction pathways and selectivity to CO2 and H2O. A fully oxidized platinum surface resulted in catalyst deactivation (over-oxidn.), which favored the formation of p-benzoquinone and polymeric products. Whereas free platinum surface was vulnerable to poisoning by carbonaceous compds., a fully reduced platinum surface favored the formation of acetic and succinic acids which are difficult to oxidize. A reaction scheme for platinum catalyzed phenol oxidn. in liq. phase is proposed. [on SciFinder (R)]