Removal of phenol from oil/gas produced water using supercritical water treatment with TiO2 supported MnO2 ctalyst

- MnO2/TiO2 catalyst synthesized by IWI method undergoes a two-step reduction.
- Oxygen concentration has a positive influence on phenol oxidation reaction.
- Higher Mn loading yields better phenol conversion due to greater catalyst active site population.
- MnO2/TiO2 catalyst increases selectivity of phenol to gas conversion.

MnO2 catalyst supported on TiO2 was synthesized and evaluated for removal of phenol in supercritical water. Synthesized catalysts were characterized using temperature programmed reduction, pulse chemisorption, and X-ray powder diffraction. Catalyst activity for phenol conversion was evaluated in a continuous packed bed reactor at supercritical water conditions by analyzing gaseous and liquid products. Process variables evaluated include O2 stream concentration and Mn catalyst loading. Both variables had positive effects on phenol conversion. The process achieved complete conversion of phenol at oxygen ratio of 5 based on complete phenol combustion stoichiometry. Increasing catalyst Mn loading increased its active site concentration, enhancing the contribution of heterogeneous reaction kinetics for supercritical water oxidation (SCWO) of the phenol. A phenol conversion of 70% was reached at 12% (w/w) Mn in the catalyst with oxygen ratio of 1.