Effect of the addition of rare earths on the activity of alumina supported copper cobaltite in CO oxidation, CH4 oxidation and NO decomposition
2015; Elsevier BV; Volume: 33; Issue: 4 Linguagem: Inglês
10.1016/s1002-0721(14)60430-0
ISSN2509-4963
AutoresBranimir Ivanov, Ivanka Spassova, Maria Milanova, G. Tyuliev, M. Христова,
Tópico(s)Nanomaterials for catalytic reactions
ResumoThe effect of the addition of small amounts of rare earths (Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/CuCo/Al catalyst were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), H2-temperature-programmed reduction (H2-TPR), electron paramagnetic resonance (EPR) spectroscopy and low temperature nitrogen adsorption. The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial reduction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/CuCo/Al catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/CuCo/Al and Nd/CuCo/Al were the most active catalysts. The catalyst Ce/CuCo/Al was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu+/Cu2+ and Ce3+/Ce4+. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2.
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