Pt-catalysts supported on activated carbons for catalytic wet air oxidation of aniline: Activity and stability

Abstract

Three activated carbons (ACs) were prepared from olive stones using KOH as activation agent at different temperatures. These materials present similar surface chemistry, but a larger porosity (mainly microporosity) is developed by increasing the activation temperature. The ACs were used as supports for Pt-catalysts and those with a larger porosity led to the highest Pt dispersion. The ACs and the supported Pt-catalysts were tested in the degradation of aniline by catalytic wet air oxidation. Aniline conversion and mineralization was found to depend on the porosity and Pt dispersion of the catalysts. The materials were characterized before and after reaction by different techniques (N-2 and CO2 adsorption, elemental analysis, TPD and XPS). Analysis of the catalysts after reaction indicated some loss of microporosity, accompanied by an increase of the oxygenated surface groups and changes in the Pt oxidation state. In addition, no Pt leaching was detected. The performance of the catalysts was evaluated during three consecutive cycles without any reactivation treatment. The activity decreased after the first cycle, which is due to the saturation of the adsorption capacity; however, the catalytic performance was constant during the second and third cycles, showing the high stability of the tested catalysts.