CuMn mixed oxides catalysts doped with La were prepared following a co-precipitation method and used for the catalytic oxidation of toluene. Catalysts properties of the catalysts were investigated by X-ray diffraction...CuMn mixed oxides catalysts doped with La were prepared following a co-precipitation method and used for the catalytic oxidation of toluene. Catalysts properties of the catalysts were investigated by X-ray diffraction, N_2 adsorption/desorption,scanning electron microscopy, H_2-temperature-programmed reduction(H_2-TPR), O_2-temperature-programmed desorption(O_2-TPD) and X-ray photoelectron spectroscopy techniques. Characterization data reveal that the phase change and decrease in crystallinity of the La-doped catalysts increase the number of oxygen vacancies. Improvements in reducibility and an increase in the amount of chemisorbed oxygen of the La-doped catalysts were also verified by H_2-TPR and O_2-TPD. The activity of the CuMn mixed oxides catalysts is significantly improved by the addition of a nominal amount of La. The CuMn/La-4 mol% catalyst exhibits the best catalytic activity, with a 90%conversion temperature of 255 ℃,attributed to a high Mn^(3+)ratio, superficial chemisorbed oxygen,and high surface area. This study indicates La to be a promising dopant for Cu-Mn catalysts toward toluene oxidation.展开更多
A series of La_(1-x)Sr_(x)MnO_(3) samples were prepared by sol-gel method and used to degrade rhodamine B(RhB) in water.All samples were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),N_...A series of La_(1-x)Sr_(x)MnO_(3) samples were prepared by sol-gel method and used to degrade rhodamine B(RhB) in water.All samples were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),N_(2) adsorption-desorption,temperature-programmed reduction of H_(2)(H_(2)-TPR) and temperature-programmed desorption of O_(2)(O_(2)-TPD).The results show that the degradation of RhB is highly dependent on the initial pH value of solution.Sr doping enhances the degradation ability of LaMnO_(3) for RhB in the time range of 0-40 min under a strong acidic environment,but all samples exhibit similar degradation rate from 40 to 60 min.In La_(0.7)Sr_(0.3)MnO_(3)-RhB reaction system,there are two different degradation pathways,including N-de-ethylation,chromophore cleavage,ring-opening and mineralization.La_(1-x)Sr_(x)MnO_(3)(x ≤0.3) has the perovskite structure of La-Mn oxides,while La_(0.6)Sr_(0.4)MnO_(3) exhibits a Sr_(0.4)MnLa_(0.6)O_(2).98 perovskite phase.Sr doping leads to distortion of rhombohedral crystal structure and increases the relative content of Mn^(4+).The perovskite structure is stable in strong acidic environment during RhB degradation,but the relative content of Mn^(4+)and Mn^(3+) on the material surface changes.Sr doped LaMnO_(3) achieves specific surface area of 58.8 m^(2)/g and total pore volume of 0.152 cm^(3)/g.Furthermore,Sr^(2+)doping improves redox properties of La-Mn oxides,and the presence of defects makes oxygen diffusion easier compared with the undoped samples.展开更多
基金the National Natural Science Foundation of China(51508356)Science and Technology Support Program of Sichuan Province(2014GZ0213,2016GZ0045)Youth Project in Science and Technology Innovation Program of Sichuan Province(17-YCG053)~~
基金Project supported by Sichuan Provincial Science and Technology Agency(2018GZ0414)the Chengdu Science and Technology Bureau Huimin Projects(2016-HM01-00075-SF)
文摘CuMn mixed oxides catalysts doped with La were prepared following a co-precipitation method and used for the catalytic oxidation of toluene. Catalysts properties of the catalysts were investigated by X-ray diffraction, N_2 adsorption/desorption,scanning electron microscopy, H_2-temperature-programmed reduction(H_2-TPR), O_2-temperature-programmed desorption(O_2-TPD) and X-ray photoelectron spectroscopy techniques. Characterization data reveal that the phase change and decrease in crystallinity of the La-doped catalysts increase the number of oxygen vacancies. Improvements in reducibility and an increase in the amount of chemisorbed oxygen of the La-doped catalysts were also verified by H_2-TPR and O_2-TPD. The activity of the CuMn mixed oxides catalysts is significantly improved by the addition of a nominal amount of La. The CuMn/La-4 mol% catalyst exhibits the best catalytic activity, with a 90%conversion temperature of 255 ℃,attributed to a high Mn^(3+)ratio, superficial chemisorbed oxygen,and high surface area. This study indicates La to be a promising dopant for Cu-Mn catalysts toward toluene oxidation.
基金Project supported by Sichuan Science and Technology Program (2020YFG0065)。
文摘A series of La_(1-x)Sr_(x)MnO_(3) samples were prepared by sol-gel method and used to degrade rhodamine B(RhB) in water.All samples were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),N_(2) adsorption-desorption,temperature-programmed reduction of H_(2)(H_(2)-TPR) and temperature-programmed desorption of O_(2)(O_(2)-TPD).The results show that the degradation of RhB is highly dependent on the initial pH value of solution.Sr doping enhances the degradation ability of LaMnO_(3) for RhB in the time range of 0-40 min under a strong acidic environment,but all samples exhibit similar degradation rate from 40 to 60 min.In La_(0.7)Sr_(0.3)MnO_(3)-RhB reaction system,there are two different degradation pathways,including N-de-ethylation,chromophore cleavage,ring-opening and mineralization.La_(1-x)Sr_(x)MnO_(3)(x ≤0.3) has the perovskite structure of La-Mn oxides,while La_(0.6)Sr_(0.4)MnO_(3) exhibits a Sr_(0.4)MnLa_(0.6)O_(2).98 perovskite phase.Sr doping leads to distortion of rhombohedral crystal structure and increases the relative content of Mn^(4+).The perovskite structure is stable in strong acidic environment during RhB degradation,but the relative content of Mn^(4+)and Mn^(3+) on the material surface changes.Sr doped LaMnO_(3) achieves specific surface area of 58.8 m^(2)/g and total pore volume of 0.152 cm^(3)/g.Furthermore,Sr^(2+)doping improves redox properties of La-Mn oxides,and the presence of defects makes oxygen diffusion easier compared with the undoped samples.
