Four manganese oxide (MnO_(x)) catalysts with different phases were prepared via a hydrothermal method, and the toluene oxidation over the four manganese dioxide (MnO_(x)) catalysts was studied. Among the catalysts, ...Four manganese oxide (MnO_(x)) catalysts with different phases were prepared via a hydrothermal method, and the toluene oxidation over the four manganese dioxide (MnO_(x)) catalysts was studied. Among the catalysts, δ-MnO_(2) exhibits the best performance, excellent stability, and reusability. Moreover, δ-MnO_(2) possesses the highest specific surface area, with more exposed active sites compared to the other catalysts with which to make contact with toluene, leading to it exhibiting excellent activity. Furthermore, δ-MnO_(2) shows more lattice defects, Mn^(3+)/(Mn^(3+) + Mn^(4+)), oxygen vacancies, and surface adsorbed oxygen than the other catalysts, resulting in its excellent redox properties and catalytic performance. In addition, oxygen molecules adsorb on the oxygen vacancies of δ-MnO_(2), which are beneficial to the adsorption and oxidation of toluene, with benzyl alcohol, benzaldehyde, benzoic acid, and benzoic acid ester detected as specific intermediate products.展开更多
A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined ...A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.展开更多
Catalytic properties of MnOx-FeOx complex oxide （hereafter denoted as Mn-Fe） catalysts modified with different loadings of chromium oxide were investigated by using the combination of physico-cbemical techniques, su...Catalytic properties of MnOx-FeOx complex oxide （hereafter denoted as Mn-Fe） catalysts modified with different loadings of chromium oxide were investigated by using the combination of physico-cbemical techniques, such as N2 physisorption, X-ray diffraction （XRD）, high-resolution transmission electron microscope （HRTEM）, in situ Fourier transform infrared spectroscopy （in situ FT-IR） and temperature-programmed reduction （TPR） and their catalytic activities were evaluated with the selective catalytic reduction （SCR） of NOx by NH3. It was found that with the addition of Cr, more NO could be removed in the low-temperature window （below 120 ℃）. Among the tested catalysts, Mn-Fe- Cr （2 ： 2 ： 1） catalyst exhibited the best catalytic performance at 80 ℃ with the NO conversion higher than 90%. The combination of the reaction and characterization results indicated that （1） the strong interaction among tertiary metal oxides existed in the catalysts when Cr was appropriately added, which made the active components better dispersed with less agglomeration and sintering and the largest BET specific surface area could be obtained; （2） Cr improved the low-temperature reducibility of the catalyst and promoted the formation of the active intermediate （-NH3＋）, which favored the low-temperature SCR reaction.展开更多
基金supported by the National Natural Science Foundation of China (No. 21872096)the Natural Science Youth Fund of Henan Province (No. 202300410034)+3 种基金the Young Teacher Foundation of Henan University of Urban Construction (No. YCJQNGGJS201903)the Key Scientific and Technological Project of Henan Province (No. 182102311016)the Henan Key Scientific Research Projects (No. 20A610003)the Doctoral Research Start-up Project of Henan University of Urban Construction (No. 990/Q2017011)
文摘Four manganese oxide (MnO_(x)) catalysts with different phases were prepared via a hydrothermal method, and the toluene oxidation over the four manganese dioxide (MnO_(x)) catalysts was studied. Among the catalysts, δ-MnO_(2) exhibits the best performance, excellent stability, and reusability. Moreover, δ-MnO_(2) possesses the highest specific surface area, with more exposed active sites compared to the other catalysts with which to make contact with toluene, leading to it exhibiting excellent activity. Furthermore, δ-MnO_(2) shows more lattice defects, Mn^(3+)/(Mn^(3+) + Mn^(4+)), oxygen vacancies, and surface adsorbed oxygen than the other catalysts, resulting in its excellent redox properties and catalytic performance. In addition, oxygen molecules adsorb on the oxygen vacancies of δ-MnO_(2), which are beneficial to the adsorption and oxidation of toluene, with benzyl alcohol, benzaldehyde, benzoic acid, and benzoic acid ester detected as specific intermediate products.
基金supported by the National Natural Science Foundation of China (Grant No. 51078185)
文摘A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.
基金supported by Jiangsu Natural Science Foundation (No. BK2012347)the National High Technology and Development Program of China (863 Programs, No.2007AA061802)
文摘Catalytic properties of MnOx-FeOx complex oxide （hereafter denoted as Mn-Fe） catalysts modified with different loadings of chromium oxide were investigated by using the combination of physico-cbemical techniques, such as N2 physisorption, X-ray diffraction （XRD）, high-resolution transmission electron microscope （HRTEM）, in situ Fourier transform infrared spectroscopy （in situ FT-IR） and temperature-programmed reduction （TPR） and their catalytic activities were evaluated with the selective catalytic reduction （SCR） of NOx by NH3. It was found that with the addition of Cr, more NO could be removed in the low-temperature window （below 120 ℃）. Among the tested catalysts, Mn-Fe- Cr （2 ： 2 ： 1） catalyst exhibited the best catalytic performance at 80 ℃ with the NO conversion higher than 90%. The combination of the reaction and characterization results indicated that （1） the strong interaction among tertiary metal oxides existed in the catalysts when Cr was appropriately added, which made the active components better dispersed with less agglomeration and sintering and the largest BET specific surface area could be obtained; （2） Cr improved the low-temperature reducibility of the catalyst and promoted the formation of the active intermediate （-NH3＋）, which favored the low-temperature SCR reaction.
