Perovskite-type La1-xCexMnO3 (x= 0-10%) catalysts were prepared by flame spray pyrolysis and their activities during the catalytic oxidation of benzene were examined over the temperature range of 100-450 ℃. The str...Perovskite-type La1-xCexMnO3 (x= 0-10%) catalysts were prepared by flame spray pyrolysis and their activities during the catalytic oxidation of benzene were examined over the temperature range of 100-450 ℃. The structural properties and reducibility of these materials were also characterized by X-ray diffraction (XRD), N2 adsorption/desorption, H2 temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The incorporation of Ce was found to improve the benzene oxidation activity, and the perovskite in which x was 0.1 exhibited the highest activity. Phase composition and surface elemental analyses indicated that non-stoichiometric compounds were present. The incorporation of Ce had a negligible effect on the specific surface area of the perovskites and hence this factor has little impact on the catalytic activity. Introduction of Ce^4+ resulted in modification of the chemical states of both B-site ions and oxygen species and facilitated the reducibility of the perovskite. The surface Mn^4+/Mn^3+ ratio was increased as a result of Ce^4+ substitution, while a decrease in the surface-adsorbed O/lattice O (Oads/Olatt) ratio was observed. The relationship between the surface elemental ratios and catalytic activity was established to allow a better understanding of the process by which benzene is oxidized over perovskites.展开更多
The design and synthesis of highly active non-noble metal oxide catalysts, such as transition- and rare-earth-metal oxides, have attracted significant attention because of their high efficiency and low cost and the re...The design and synthesis of highly active non-noble metal oxide catalysts, such as transition- and rare-earth-metal oxides, have attracted significant attention because of their high efficiency and low cost and the resultant potential applications for the degradation of volatile organic compounds(VOCs). The structure-activity relationships have been well-studied and used to facilitate design of the structure and composition of highly active catalysts. Recently, non-noble metal oxides with porous structures have been used as catalysts for deep oxidation of VOCs, such as aromatic hydrocarbons, aliphatic compounds, aldehydes, and alcohols, with comparable activities to their noble metal counterparts. This review summarizes the growing literature regarding the use of porous metal oxides for the catalytic removal of VOCs, with emphasis on design of the composition and structure and typical synthetic technologies.展开更多
Flame spray pyrolysis (FSP) was utilized to synthesize Ce-Mn oxides in one step for catalytic oxidation of benzene. Cerium acetate and manganese acetate were used as precursors. The materials synthesized were charac...Flame spray pyrolysis (FSP) was utilized to synthesize Ce-Mn oxides in one step for catalytic oxidation of benzene. Cerium acetate and manganese acetate were used as precursors. The materials synthesized were characterized using X-ray diffraction (XRD), N2 adsorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and H2-temperature programmed reduc- tion (H2-TPR) and their benzene catalytic oxidation behavior was evaluated. Mn ions were evidenced in multiple chemical states. Crystalline Ce-Mn oxides consist of particles with size 〈40 nm and specific sur- face areas (SSA) of 20-50 m2/g. Raman spectrums and H2-TPR results indicated the interaction between cerium and manganese oxides. Flame-made 12.5%-Ce-Mn oxide exhibited excellent catalytic activity at relatively low temperatures (T95 about 260℃) compared to other Ce-Mn oxides with different cerium- to-manganese ratios, Redox mechanism and strong interaction conform to structure analysis that Ce-Mn strong interaction formed during the high temperature flame process and the results were used to explain catalytic oxidation of benzene.展开更多
Mesoporous TiO2 was synthesized via nonhydrolytic template-mediated sol-gel route.Catalytic degradation performance upon dichloromethane over as-prepared mesoporous TiO2,pure anatase and rutile were investigated respe...Mesoporous TiO2 was synthesized via nonhydrolytic template-mediated sol-gel route.Catalytic degradation performance upon dichloromethane over as-prepared mesoporous TiO2,pure anatase and rutile were investigated respectively.Disproportionation took place over as-made mesoporous TiO2 and pure anatase under the presence of water.The mechanism of disproportionation was studied by in situ FTIR.The interaction between chloromethoxy species and bridge coordinated methylenes was the key step of disproportionation.Formate species and methoxy groups would be formed and further turned into carbon monoxide and methyl chloride.Anatase(001)played an important role for disproportionation in that water could be dissociated into surface hydroxyl groups on such structure.As a result,the consumed hydroxyl groups would be replenished.In addition,there was another competitive oxidation route governed by free hydroxyl radicals.In this route,chloromethoxy groups would be oxidized into formate species by hydroxyl radicals transfering from the surface of TiO2.The latter route would be more favorable at higher temperature.展开更多
A co-current flow rotating packed bed was applied to remove volatile organic compounds(VOCs) by sodium hypochlorite(Na Cl O) and surfactant(sodium dodecyl benzene sulfonate,SDBS) from air stream. Xylene was used...A co-current flow rotating packed bed was applied to remove volatile organic compounds(VOCs) by sodium hypochlorite(Na Cl O) and surfactant(sodium dodecyl benzene sulfonate,SDBS) from air stream. Xylene was used as a model VOC herein. The effect of p H,concentration of Na Cl O and SDBS solution, liquid flow rate, gas flow rate and rotational speed on xylene removal efficiency and overall mass transfer coefficient(KGa) were discussed. Then, a correlation for KGa of the co-current rotating packed bed was proposed by fitting the experimental data of KGa and independent variables of liquid/gas ratio,rotational speed, p H, Na Cl O concentration and treatment time, which was in good agreement with the experimental data(the deviation ≤ ± 30%).展开更多
Hierarchical sea-urchin-shaped manganese oxide microspheres were synthesized via a facile method based on the reaction between KMnO4 and MnSO4 in HNO3 solution at 50℃. The average diameter of the microspheres is -850...Hierarchical sea-urchin-shaped manganese oxide microspheres were synthesized via a facile method based on the reaction between KMnO4 and MnSO4 in HNO3 solution at 50℃. The average diameter of the microspheres is -850 nm. The microspheres consist of a core of diameter of -800 nm and nanorods of width -50 nm. The nanorods exist at the edge of the core, The Brunauer-Emmett-Teller surface area of the sea-urchin-shaped microspheres is 259.4 m^2/g. A possible formation mechanism of the hierarchical sea-urchin-shaped microspheres is proposed. The temperature for 90% conversion of benzene (T90%) on the hierarchical urchin-shaped MnO2 microspheres is about 218 ℃.展开更多
基金the financial support of the National High Technology Research and Development Program of China(Grant Nos.2012AA062702 and 2010AA064903)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDB05050300)+2 种基金the National Natural Science Foundation of China(No.21306199)the Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YZ200722)the 12th Five-years National Key Technology R&D Program(Grant Nos. 2012BAJ02B03 and 2012BAJ02B07)
文摘Perovskite-type La1-xCexMnO3 (x= 0-10%) catalysts were prepared by flame spray pyrolysis and their activities during the catalytic oxidation of benzene were examined over the temperature range of 100-450 ℃. The structural properties and reducibility of these materials were also characterized by X-ray diffraction (XRD), N2 adsorption/desorption, H2 temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The incorporation of Ce was found to improve the benzene oxidation activity, and the perovskite in which x was 0.1 exhibited the highest activity. Phase composition and surface elemental analyses indicated that non-stoichiometric compounds were present. The incorporation of Ce had a negligible effect on the specific surface area of the perovskites and hence this factor has little impact on the catalytic activity. Introduction of Ce^4+ resulted in modification of the chemical states of both B-site ions and oxygen species and facilitated the reducibility of the perovskite. The surface Mn^4+/Mn^3+ ratio was increased as a result of Ce^4+ substitution, while a decrease in the surface-adsorbed O/lattice O (Oads/Olatt) ratio was observed. The relationship between the surface elemental ratios and catalytic activity was established to allow a better understanding of the process by which benzene is oxidized over perovskites.
基金supported by the National High Technology Research and Development Program of China(2012AA062702)the strategic project of the Chinese Academy of Sciences(XDB05050000)
文摘The design and synthesis of highly active non-noble metal oxide catalysts, such as transition- and rare-earth-metal oxides, have attracted significant attention because of their high efficiency and low cost and the resultant potential applications for the degradation of volatile organic compounds(VOCs). The structure-activity relationships have been well-studied and used to facilitate design of the structure and composition of highly active catalysts. Recently, non-noble metal oxides with porous structures have been used as catalysts for deep oxidation of VOCs, such as aromatic hydrocarbons, aliphatic compounds, aldehydes, and alcohols, with comparable activities to their noble metal counterparts. This review summarizes the growing literature regarding the use of porous metal oxides for the catalytic removal of VOCs, with emphasis on design of the composition and structure and typical synthetic technologies.
基金financial supports from National Nature Science Foundation of China(Grant No.51002154)Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YZ200722)+2 种基金National High Technology Research and Development Program of China(Grant Nos.2012AA062702, 2010AA064903)the 12th Five-Year National Key Technology R&D Program(Grant Nos.2012BAJ02B03,2012BAJ02B07)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB05050300)
文摘Flame spray pyrolysis (FSP) was utilized to synthesize Ce-Mn oxides in one step for catalytic oxidation of benzene. Cerium acetate and manganese acetate were used as precursors. The materials synthesized were characterized using X-ray diffraction (XRD), N2 adsorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and H2-temperature programmed reduc- tion (H2-TPR) and their benzene catalytic oxidation behavior was evaluated. Mn ions were evidenced in multiple chemical states. Crystalline Ce-Mn oxides consist of particles with size 〈40 nm and specific sur- face areas (SSA) of 20-50 m2/g. Raman spectrums and H2-TPR results indicated the interaction between cerium and manganese oxides. Flame-made 12.5%-Ce-Mn oxide exhibited excellent catalytic activity at relatively low temperatures (T95 about 260℃) compared to other Ce-Mn oxides with different cerium- to-manganese ratios, Redox mechanism and strong interaction conform to structure analysis that Ce-Mn strong interaction formed during the high temperature flame process and the results were used to explain catalytic oxidation of benzene.
文摘Mesoporous TiO2 was synthesized via nonhydrolytic template-mediated sol-gel route.Catalytic degradation performance upon dichloromethane over as-prepared mesoporous TiO2,pure anatase and rutile were investigated respectively.Disproportionation took place over as-made mesoporous TiO2 and pure anatase under the presence of water.The mechanism of disproportionation was studied by in situ FTIR.The interaction between chloromethoxy species and bridge coordinated methylenes was the key step of disproportionation.Formate species and methoxy groups would be formed and further turned into carbon monoxide and methyl chloride.Anatase(001)played an important role for disproportionation in that water could be dissociated into surface hydroxyl groups on such structure.As a result,the consumed hydroxyl groups would be replenished.In addition,there was another competitive oxidation route governed by free hydroxyl radicals.In this route,chloromethoxy groups would be oxidized into formate species by hydroxyl radicals transfering from the surface of TiO2.The latter route would be more favorable at higher temperature.
基金financially supported by the Strategic Project of Science and Technology of Chinese Academy of Science(No.XDB05050000)
文摘A co-current flow rotating packed bed was applied to remove volatile organic compounds(VOCs) by sodium hypochlorite(Na Cl O) and surfactant(sodium dodecyl benzene sulfonate,SDBS) from air stream. Xylene was used as a model VOC herein. The effect of p H,concentration of Na Cl O and SDBS solution, liquid flow rate, gas flow rate and rotational speed on xylene removal efficiency and overall mass transfer coefficient(KGa) were discussed. Then, a correlation for KGa of the co-current rotating packed bed was proposed by fitting the experimental data of KGa and independent variables of liquid/gas ratio,rotational speed, p H, Na Cl O concentration and treatment time, which was in good agreement with the experimental data(the deviation ≤ ± 30%).
基金supported by the National High Technology Research and Development Program 863 of China,No.2010AA064903National Natural Science Foundation of China(NSFC) No. 51002154
文摘Hierarchical sea-urchin-shaped manganese oxide microspheres were synthesized via a facile method based on the reaction between KMnO4 and MnSO4 in HNO3 solution at 50℃. The average diameter of the microspheres is -850 nm. The microspheres consist of a core of diameter of -800 nm and nanorods of width -50 nm. The nanorods exist at the edge of the core, The Brunauer-Emmett-Teller surface area of the sea-urchin-shaped microspheres is 259.4 m^2/g. A possible formation mechanism of the hierarchical sea-urchin-shaped microspheres is proposed. The temperature for 90% conversion of benzene (T90%) on the hierarchical urchin-shaped MnO2 microspheres is about 218 ℃.