Copper Oxide Mounted on Activated Carbon as Catalyst for Wet Air Oxidation of Aqueous Phenol. 2. Catalyst Stability

Stability aspects of the Sofnocarb A21 catalyst (5% CuO on activated carbon) have been studied for catalytic wet air oxidation of phenol. The study focused on copper leaching, the main factor affecting the catalyst stability. It was found that no copper leaching took place in the experiments using fresh catalyst, when the initial phenol concentration was lower than 1.5 kg/m3. Nevertheless, copper leaching and fouling were observed through consecutive experiments reusing the catalyst, leading to deactivation of catalyst and therefore a lower phenol oxidation rate. The main reaction intermediates, namely acetic acid and p-benzoquinone, together with polymeric products are highlighted to be responsible for copper leaching and fouling. Nonetheless, the leaching of active substance measured for Sofnocarb A21 was much lower than those found for other catalysts (G-66 A, Süd Chemie, Germany) also used for catalytic decomposition of phenol. Basic conditions were demonstrated to be useful to prevent both copper leaching and fouling, thereby enhancing the catalyst lifetime.