Wet air oxidation is the liquid phase oxidation of organics at elevated temperatures (125-320℃) and pressures (0.5-20 MPa) using molecular oxygen as oxidant. Wet oxidation is suitable for the treatment of the wastewater which is too concentrated and/or toxic to be treated with biological approach because any organic compound could be ideally mineralized to the desired end products by wet oxidation. Using the proper catalysts for the wet oxidation system not only moderates the severity of the reaction conditions but also makes it possible to treat only a single pollutant, or a group of similar pollutants, out of a complex mixture of pollutants.
In this study, wet air oxidation of phenol was investigated over the noble metal catalysts or the metal oxide catalysts.
First, wet oxidation of phenol over alumina supported Pt catalysts was investigated. The Ce addition effect on metal dispersion, reducibility of catalysts, and catalytic activity of wet oxidation of phenol was observed for two different Pt precursors. $Pt/Al_2O_3$ made from $H_2PtCl_6$ showed the higher activity for the wet oxidation of phenol than that from $Pt(NH_3)_4Cl_6$, which could be explained with the Pt surface area: the Pt surface area of the former catalyst is higher than that of the latter one. Cerium addition lowered the catalytic activity of $Pt/Al_2O_3$ catalysts from $H_2PtCl_6$ while it improved the activity of $Pt/Al_2O_3$ catalysts from $Pt(NH_3)_4Cl_6$. The former could be explained by the decrease of the platinum surface area with addition of cerium while the latter could not be explained by platinum surface area because of little change in platinum surface area. The increase of activity of $Pt/Al_2O_3$ catalysts from $Pt(NH_3)_4Cl_6$ could be explained with the enhanced surface reducibility by the interactions between platinum and cerium.
There were carbonaceous deposits on the $Pt/Al_2O_3$ catalyst surfaces after wet oxidation reaction, and the chemical species of the depo...