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Electro-Oxidation of Concentrated Ce(Ⅲ) at Carbon Felt Anode in Nitric Acid Media 被引量:6
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作者 Jelinek Ludek Mikio Kumagai 《Journal of Rare Earths》 SCIE EI CAS CSCD 2006年第3期257-263,共7页
Electro-oxidation of Ce ( Ⅲ ) to Ce ( Ⅳ ) in parallel plate flow type electrolyzer divided with cation exchange membrane was carried out in nitric acid media at carbon felt anode under galvanostatic conditions. ... Electro-oxidation of Ce ( Ⅲ ) to Ce ( Ⅳ ) in parallel plate flow type electrolyzer divided with cation exchange membrane was carried out in nitric acid media at carbon felt anode under galvanostatic conditions. Carbon felt was used as an anode for its high specific surface area and high oxygen evolution overpotential. Pt coated Ti plates were used as cathode and anode current feeder. The oxidation of 1 mol· L^-1 Ce( Ⅲ ) solution in 2 mol· L^- 1 HNO3 was proceeding with a high current efficiency (92%) until about 80% of Ce( Ⅲ ) was oxidized. Then, oxygen evolution, accompanied by terminal voltage jump, took place, lowering current efficiency. Ce( Ⅲ ) was oxidized up to 90% with current efficiency of 62%. In this mode, strong carbon felt anode oxidation was observed. The wear out of carbon felt was 46% in six consequent runs (6 h of operation). After each run, carbon felt surface had to be renewed with slightly alkaline solution to remove carbon oxidation products and ensure regular operational conditions. When anode surface was blocked, oxygen evolution took place from the beginning of electrolysis due to higher actual current density. The wear out of carbon felt anode could be minimized by means of oxygen evolution prevention. In the case when electrolysis had been stopped before oxygen evolution started (at Ce( Ⅳ ) conversion of about 80% ), the wear out of anode was less than 2% during 6 consequent runs (4 h of operation). 展开更多
关键词 ELECTROLYZER ce oxidation carbon felt anode rare earths
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Preparation and characterization of Ce_(1-x)Fe_xO_2 complex oxides and its catalytic activity for methane selective oxidation 被引量:7
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作者 李孔斋 王华 +1 位作者 魏永刚 刘明春 《Journal of Rare Earths》 SCIE EI CAS CSCD 2008年第2期245-249,共5页
A series of Ce1-xFexO2 (x=0, 0.2, 0.4, 0.6, 0.8, 1) complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane ... A series of Ce1-xFexO2 (x=0, 0.2, 0.4, 0.6, 0.8, 1) complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃. 展开更多
关键词 ce1-xFexO2 complex oxides H2-TPR lattice oxygen methane selective oxidation rare earths
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Immobilization of metalloporphyrins on CeO_2@SiO_2 with a core-shell structure prepared via microemulsion method for catalytic oxidation of ethylbenzene 被引量:1
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作者 沈丹华 吉琳韬 +4 位作者 付玲玲 董旭龙 刘志刚 刘强 刘世明 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第3期862-867,共6页
Ce O2@Si O2 core-shell nanoparticles were prepared by microemulsion method, and metalloporphyrins were immobilized on the Ce O2@Si O2 core-shell nanoparticles surface via amide bond. The supported metalloporphyrin cat... Ce O2@Si O2 core-shell nanoparticles were prepared by microemulsion method, and metalloporphyrins were immobilized on the Ce O2@Si O2 core-shell nanoparticles surface via amide bond. The supported metalloporphyrin catalysts were characterized by N2 adsorption-desorption isotherm(BET), scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), ultraviolet and visible spectroscopy(UV-Vis), and Fourier transform infrared spectroscopy(FT-IR). The results show that the morphology of Ce O2@Si O2 nanoparticles is core-shell microspheres with about 30 nm in diameter, and metalloporphyrins are immobilized on the Ce O2@Si O2 core-shell nanoparticles via amide bond. Especially, the core-shell structure contains multi Ce O2 core and thin Si O2 shell, which may benefit the synergistic effect between the Ce O2 core and the porphyrin anchored on the very thin Si O2 shell. As a result, this supported metalloporphyrin catalysts present comparably high catalytic activity and stability for oxidation of ethylbenzene with molecular oxygen, namely, ethylbenzene conversion remains around 12% with identical selectivity of about 80% for acetophenone even after six-times reuse of the catalyst. 展开更多
关键词 ce O2@Si O2 core-shell structure metalloporphyrin ethylbenzene oxidation
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Density Function Theory Study on the Reaction Mechanism of Cerium with Oxygen for Ce-bearing Aerosol Particle Formation
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作者 XIE Bo WANG Qingqing +2 位作者 LONG Xinggui HU Sheng GAO Tao 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2020年第3期501-505,共5页
We obtained the reaction mechanism of cerium with oxygen by means of density functional theory (DFT) under the explosive or detonation situation. The energy level order of cerium was calculated and the potential energ... We obtained the reaction mechanism of cerium with oxygen by means of density functional theory (DFT) under the explosive or detonation situation. The energy level order of cerium was calculated and the potential energy profile was plotted. The properties of the bonds of all special structures in the reaction path were analyzed using the method of the electron localization function (ELF). The results indicate that the final reaction pathway can be expressed as Ce+O2→ FC→TS→IM→O-Ce-O, and the formation of Ce2O3 has not been found. In addition, the ELF diagram of the final product CeO2 shows that Ce bonds with both O atoms and the bond angles increase significantly. 展开更多
关键词 ce oxidation reaction mechanism electronic localized function aerosol particles
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Specific Adsorption of Trivalent La, Ce and Y by Soils and Ferro-manganese Oxides and Its Mechanism
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作者 RANYONG LIUZHENG 《Pedosphere》 SCIE CAS CSCD 1992年第1期13-22,共10页
In this paper, the adsorption-desorption variations of trivalent La, Ce, Y and mixed rare earths are discussed. The curves of pH-rare earth element adsorption were very well fitted to the equation: InD =a+b pH. The se... In this paper, the adsorption-desorption variations of trivalent La, Ce, Y and mixed rare earths are discussed. The curves of pH-rare earth element adsorption were very well fitted to the equation: InD =a+b pH. The selectivity of RE (rare earth element) ions by the samples decreased in the following order: Ce> RE> La> Y, but the sequences were: La> Ce> Y on kaolinite and Y> La on amorphous iron oxide. Since the trivalent RE ions existed in the form of RE(OH)2+ in the solutions from pH < 5.45 to 7.0, the ratio of H+ displaced to RE3+ adsorbed in micromole was proposed to be about 2. The specific adsorption mechanism for RE was proposed to be that the RE ions complexed with oxide surface and the ion-surface complex of Ce3+ promoted oxidization on Mn hydroxide. 展开更多
关键词 ce oxidization rare earth elements SELECTIVITY specific adsorption surface complexation
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Ce_xTi_(1-x)O_2 Mixed Oxides Supported CuO Catalyst for NO Reduction by CO 被引量:1
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作者 楼莉萍 蒋晓原 +3 位作者 陈英旭 吕光烈 周仁贤 郑小明 《Journal of Rare Earths》 SCIE EI CAS CSCD 2003年第3期331-336,共6页
Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2~0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effe... Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2~0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1~0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃. 展开更多
关键词 catalitic chemistry ce x Ti 1- x O 2 mixed oxides CuO/ce x Ti 1- x O 2 catalysts ceTi 2O 6 phase NO+CO reaction activity rare earths
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Selective oxidation of methane and carbon deposition over Fe_2O_3/Ce_(1-x)Zr_xO_2 oxides 被引量:4
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作者 Xiu-Li Sang Kong-Zhai Li +1 位作者 Hua Wang Yong-Gang Wei 《Rare Metals》 SCIE EI CAS CSCD 2014年第2期230-238,共9页
A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2(x = 0.1–0.4) oxides was prepared and their physicochemical features were investigated by X-ray diffraction(XRD), transmission electron micro... A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2(x = 0.1–0.4) oxides was prepared and their physicochemical features were investigated by X-ray diffraction(XRD), transmission electron microscope(TEM), and H2-temperature-programmed reduction(H2-TPR) techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity(ca. 97 %) for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation. 展开更多
关键词 Methane Carbon deposition Gas–solid reaction Selective oxidation of carbon Fe2O3/ce1-xZrxO2 catalysts
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Enhancement of potassium resistance of Ce-Ti oxide catalyst for NH_(3)-SCR reaction by modification with holmium 被引量:5
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作者 Chaopeng Duan Ruitang Guo +4 位作者 Yuanzhen Liu Guilin Wu Yufang Miao Jingwen Gu Weiguo Pan 《Journal of Rare Earths》 SCIE EI CAS CSCD 2022年第1期49-56,共8页
Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Bruna... Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),NH_(3) temperature programmed desorption(NH_(3)-TPD)and H_(2)temperature programmed reduction(H_(2)-TPR)analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability,the higher concentration of Ce^(3+)species and surface chemisorbed oxygen.In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH_(3) and NO_(x) species on catalyst surface,accompanied by the intensified reactivity of ad-NH_(3) species,which should also administer to improve the K resistance. 展开更多
关键词 NH_(3)-SCR Ho ce Ti oxide catalyst K resistance Rare earths
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Structure and catalytic property of CeO_2-ZrO_2-Fe_2O_3 mixed oxide catalysts for diesel soot combustion: Effect of preparation method 被引量:7
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作者 顾振华 桑秀丽 +1 位作者 王华 李孔斋 《Journal of Rare Earths》 SCIE EI CAS CSCD 2014年第9期817-823,共7页
A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods (co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method) and character... A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods (co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method) and characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) and H2-TPR measurements. Potential of the catalysts in the soot oxidation was evaluated in a temperature-programmed oxidation (TPO) apparatus. The results showed that all the Fe3+ and Zr4+ were incor- porated into ceria lattice to form a pure Ce-Fe-Zr-O solid solution for the co-precipitation sample, but two kinds of Fe phases ex- isted in the Ce-Fe-Zr-O catalysts prepared by other methods: Fe3+ incorporated into CeO2 lattice and dispersed Fe2O3 clusters. The free Fe2O3 clusters could improve the activity of catalysts for soot oxidation comparing with the pure Ce-Fe-Zr-O solid solution owing to the synergetic effect between free Fe2O3 and surface oxygen vacancies. In addition, the activity of catalysts strongly relied on the surface reducibility of free Fe2O3 particles. Holding both abundant free Fe2O3 particles and high oxygen vacancy concentration, the hydrothermal Ce0.5Fe0.3Zr0.202 catalyst presented the lowest Ti (251℃, ignition temperature of soot oxidation) and Tm (310 ℃, maximum oxidation rate temperature) for soot combustion (with tight-contact between soot and catalysts) among the five samples. Even after aging at 800 ℃ for 10 h, the Ti and Tm were still relatively low, at 273 and 361 ℃, respectively, indicating high catalytic stability. 展开更多
关键词 ce0.5Fe0.30Zr0.20O2 mixed oxides soot combustion solid solution INTERACTION hydrothermal method rare earths
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Preparation and characterization of Ce(1-x)PrxO2 supports and their catalytic activities 被引量:3
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作者 Kingkaew Chayakul Chanapattharapol Somkiat Krachuamram +2 位作者 Ammarika Makdee Preeya Unwiset Sirihathai Srikwanjai 《Journal of Rare Earths》 SCIE EI CAS CSCD 2017年第12期1197-1205,共9页
In this work, the addition of praseodymium(Pr) into ceria as a mixed oxide support in a form of Ce(1-x)PrxO2(x = 0.01,0.025, 0.050, 0.075 and 0.10) was prepared using a co-precipitation method. The structural an... In this work, the addition of praseodymium(Pr) into ceria as a mixed oxide support in a form of Ce(1-x)PrxO2(x = 0.01,0.025, 0.050, 0.075 and 0.10) was prepared using a co-precipitation method. The structural and textural properties of the synthesized supports were characterized by X-ray diffraction(XRD), N2 adsorption-desorption, Raman spectroscopy, H2-temperature programmed reduction(H2-TPR) and H2-chemisorption. Upon addition of Pr, XRD patterns and Raman spectra indicated an enlargement of ceria unit cell and the characteristics Raman broad peak at 570 cm^(-1) which was attributed to the existence of oxygen vacancies in the ceria lattice. This indicated that some Ce^(4+) ions in ceria were replaced by larger Pr^(3+) cations. To evidence the incorporation of Pr^(3+) cations into ceria lattice,X-ray absorption near edge structure(XANES) was employed. The results showed that the oxidation states of Ce in mixed oxide supports were slightly lower than 4+ while those of Pr were still the same as a precursor salt. Therefore, the incorporation of Pr^(3+) into ceria lattice would lead to strain and unbalanced charge and result in oxygen vacancies. The reducibility of Ce(1-x)PrxO2 mixed oxide supports was investigated by H2-TPR and temperature-resolved X-ray absorption spectroscopy experiment under reduction conditions. XANES spectra of Ce L3 edges showed a lower surface reduction temperature(Ce^(4+)to Ce^(3+)) of Ce(0.925)Pr(0.075)O2 than that of CeO2 which agreed with H2-TPR results. H2-chemisorption indicated that Pr promoted the dispersion of the metal catalyst on the mixed oxide support and increased the adsorption site for CO. For WGS reaction, 1% Pd/mixed oxide support had higher WGS activity than 1%Pd/ceria. The increase of WGS activity was due to the increase of Pd dispersion on the support and the existence of oxygen vacancies produced from incorporation of Pr into the ceria lattice. 展开更多
关键词 ce(1-x)PrxO2 mixed oxide support Oxygen vacancies Temperature-resolved in-situ H2 reduction
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