CeO2–MnOx composite loaded on Al2O3 as a catalyst for HCl oxidation

Abstract

Catalytic oxidation of HCl to Cl₂ catalyzed by CeO₂ is an effective and economic way for sustainable chlorine recycling. Pure CeO₂ exhibited remarkably stable Cl₂ production, while its catalytic activity still cannot satisfy industrial requirements. In this work, we developed a novel catalyst with a CeO₂–MnO_x composite loaded on Al₂O₃ (denoted as CeO₂–MnO_x/Al₂O₃) for HCl oxidation. The catalyst with the optimum Mn content exhibited remarkably improved activity and stability with a X_HCl of above 72% for at least 200 h. X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) characterization suggested that the CeO₂ and MnO_x lattices were completely integrated. X-ray photoemission spectroscopy (XPS) characterization revealed the highest ratio of Ce³⁺/Ce⁴⁺, Mn⁴⁺/Mn³⁺ and surface oxygen vacancies on the surface of CeO₂–MnO_x/Al₂O₃ with the optimum Mn content. In addition, H₂-temperature programmed reduction (H₂-TPR) characterization suggested the improved reducibility of CeO₂–MnO_x/Al₂O₃ compared with CeO₂/Al₂O₃. Furthermore, compared with CeO₂/Al₂O₃, the significantly improved chlorine adsorption on the bulk and surface of the catalyst was justified by XPS and XRD. Therefore, both the strong adsorption of Cl and strong re-oxidation ability result in the high activity and stability of the CeO₂(12)–MnO_x(13)/Al₂O₃ catalyst.