Cu-Mn catalysts modified by rare earth lantnaum for low temperature water-gas shift reaction

Abstract

The Cu-Mn catalysts doped with different amounts of lanthanum (La) for water-gas shift reaction (WGSR) were prepared, and characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed reduction of oxidized surfaces (s-TPR), temperature-programmed desorption of CO2 (CO2-TPD), infrared spectrum (FT-IR) and X-ray photoelectron spectroscopy (XPS). Catalytic activities were tested for a water-gas shift reaction. The results showed that the introduction of 0.5 mol.% La could significantly improve the catalyst activity for low-temperature shift reaction compared with the undoped catalyst, which might be from the introduction of La making the Cu and Mn components distribute uniformly and the synergistic effect between Cu and Mn increasing the dispersion of Cu on the surface of the catalyst. The apparent CuO phases besides Cu1.5Mn1.5O4 were found in the samples with at least 3.0 mol.% La content, and the basic sites increased with the increasing of La contents at a decreased rate. With excessive La doping, La particles would aggregate and cover some active sites, resulting in that Mn could not effectively inhibit the gathering together and growing up of Cu crystalline grain, and decreased the dispersion of Cu on the surface, which resulted in the poor activity of the catalyst for WGSR.