CeO2–MnOx composite loaded on Al2O3 as a catalyst for HCl oxidation†
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–MnOx composite loaded on Al2O3 (denoted as CeO2–MnOx/Al2O3) for HCl oxidation. The catalyst with the optimum Mn content exhibited remarkably improved activity and stability with a XHCl 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 MnOx 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–MnOx/Al2O3 with the optimum Mn content. In addition, H2-temperature programmed reduction (H2-TPR) characterization suggested the improved reducibility of CeO2–MnOx/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)–MnOx(13)/Al2O3 catalyst.