Mesostructured Cu-Mn-Ce-O composites with homogeneous bulk composition for chlorobenzene removal: Catalytic performance and microactivation course

Cu-Mn-Ce-O composites with enhanced surface area and developed mesoporosity were synthesized using a homogeneous coprecipitation (hcp) method, and were tested in the catalytic destruction of chlorobenzene (CB). X-ray diffraction (XRD), N-2 adsorption/desorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (H-2-TPR), temperature programmed desorption of CB/O-2 (CB/O-2-TPD), and diffuse reflectance ultraviolet visible spectroscopy (DRUV-Vis) were used to characterize the structure and textural properties of catalysts. Mn and Cu enter CeO2 matrix with a fluorite-like structure, and produce large amounts of oxygen vacancies. Addition of manganese promotes the formation of reduced copper phase, and the presence of large numbers of high valence Mn4+ ions strongly enhances the redox couple of Cu+-Cu2+ in the composites. Both the synthesis protocol and metal doping amount significantly affect the catalyst reducibility, surface state and oxygen density. Cu0.15Mn0.15Ce0.85Ox synthesized via the hcp method exhibits the highest catalytic activity with 90% of chlorobenzene destructed at 255 degrees C (CO2 selectivity > 99.5%). Enriched surface oxygen, excellent active oxygen mobility and CB adsorption ability guarantee the superior activity and stability of Cu-Mn-Ce-O composite catalysts. Nucleophilic and electrophilic substitutions happen in sequence during chlorobenzene destruction, and the adsorbed Cl can be finally removed in the form of Cl-2 via the Deacon reaction. Furthermore, the incorporation of CuO and MnOx phases can inhibit the formation of organic byproducts, such as phenolates, maleates, and o-benzoquinone-type species, especially at elevated reaction temperatures. (C) 2015 Elsevier B.V. All rights reserved.