CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared s...CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.展开更多
A series of monolithic Ni/CeO_2-ZrO_2/γ-Al_2O_3 catalysts for the POM reaction were prepared. The activity test shows that the catalyst has the best performance when CeO_2-ZrO_2 content is 8 wt%.The synergistic actio...A series of monolithic Ni/CeO_2-ZrO_2/γ-Al_2O_3 catalysts for the POM reaction were prepared. The activity test shows that the catalyst has the best performance when CeO_2-ZrO_2 content is 8 wt%.The synergistic actions between CeO_2-ZrO_2 and γ-Al_2O_3 improve highly catalytic activity by increasing CH_4 conversion, H_2 and CO selectivity. XPS analysis of the used catalyst indicates that there coexist Ce^(4+) and Ce^(3+).展开更多
Dry reforming of methane(DRM)converts CH4 and CO_(2) to syngas.Photothermal DRM,which integrates temperature and light,is a sustainable method for storing solar energy in molecules.However,challenges such as limited l...Dry reforming of methane(DRM)converts CH4 and CO_(2) to syngas.Photothermal DRM,which integrates temperature and light,is a sustainable method for storing solar energy in molecules.However,challenges such as limited light absorption,low photocarrier separation efficiency,Ni sintering,and carbon deposition hinder DRM stability.Herein,we regulated Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance the optical characteristics while addressing Ni sintering and carbon deposition issues.The(3Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst had insufficient Ni content,while the(9Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst showed excessive carbon deposition,leading to lower stability compared to the(6Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst,which achieved CH4 and CO_(2) rates to 231.0 μmol gcat^(-1)s^(-1) and 294.3 μmol gcat^(-1)s^(-1) ,respectively,at 973 K,with only 0.2 wt.%carbon deposition and no Ni sintering.This work adjusted Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance DRM performance,which has implications for improving other reactions.展开更多
The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal cent...The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal center renders it to exhibit electrochemical activity only under high overpotentials.Herein,we report P-and S-doped Ni single-atom catalysts,i.e.symmetric Ni_(1)/PN_(4)and asymmetric Ni1/SN_(3)C can exhibit high catalytic activity of CO_(2)reduction with stable potential windows.It is revealed that the key intermediate*COOH in CO_(2)electroreduction is stabilized by heteroatom doping,which stems from the upward shift of the axial d_(z2)orbital of the active metal Ni atom.Furthermore,we investigate the potential-dependent free energetics and dynamic properties at the electrochemical interface on the Ni1/SN3C catalyst using ab initio molecular dynamics simulations with a full explicit solvent model.Based on the potential-dependent microkinetic model,we predict that S-atom doped Ni SAC shifts the onset potential of CO_(2)electroreduction from–0.88 to–0.80 V vs.RHE,exhibiting better activity.Overall,this work provides an in-depth understanding of structure-activity relationships and atomic-level electrochemical interfaces of catalytic systems,and offers insights into the rational design of heteroatom-doped catalysts for targeted catalysis.展开更多
Nickel and sulfate co-modified CeO2-ZrO2 catalysts were prepared by sol-gel method. The catalysts were characterized by XRD, FTIR, XPS, NH3 chemisorption and NH3-SCR activity tests. The results showed that the enhance...Nickel and sulfate co-modified CeO2-ZrO2 catalysts were prepared by sol-gel method. The catalysts were characterized by XRD, FTIR, XPS, NH3 chemisorption and NH3-SCR activity tests. The results showed that the enhanced acidity of CeO2-ZrO2 catalysts by nickel and sulfate co-modification was responsible for the broadened temperature window and improved the selectivity to N2 in NH3-SCR deNOx. The introduction of nickel to CeO2-ZrO2 solid solutions resulted in more Ce3+ on surface of catalyst, leading to an in...展开更多
Ce-Zr-Al-Nd2O3 （CZAN） support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction （XRD）, low temperature nitrogen adsorption-desorption,...Ce-Zr-Al-Nd2O3 （CZAN） support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction （XRD）, low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction （H2-TPR） and X-ray photoelectron spectroscopy （XPS）. The Pd-only three-way catalysts （Pd-TWC） supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3＋ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.展开更多
Reverse water gas shift (RWGS) reaction can serve as a pivotal stage in the CO2 conversion processes, which is vital for the utilization of CO2. In this study, RWGS reaction was performed over Pt/CeO2 catalysts at the...Reverse water gas shift (RWGS) reaction can serve as a pivotal stage in the CO2 conversion processes, which is vital for the utilization of CO2. In this study, RWGS reaction was performed over Pt/CeO2 catalysts at the temperature range of 200-500 degrees C under ambient pressure. Compared with pure CeO2, Pt/CeO2 catalysts exhibited superior RWGS activity at lower reaction temperature. Meanwhile, the calculated TOF and E-a values are approximately the same over these Pt/CeO2 catalysts pretreated under various calcination conditions, indicating that the RWGS reaction is not affected by the morphologies of anchored Pt nanoparticles or the primary crystallinity of CeO2. TPR and XPS results indicated that the incorporation of Pt promoted the reducibility of CeO2 support and remarkably increased the content of Ce 3 + sites on the catalyst surface. Furthermore, the CO TPSR-MS signal under the condition of pure CO2 flow over Pt/CeO 2 catalyst is far lower than that under the condition of adsorbed CO2 with H-2 -assisted flow, revealing that CO2 molecules adsorbed on Ce3+ active sites have difficult in generating CO directly. Meanwhile, the adsorbed CO2 with the assistance of H-2 can form formate species easily over Ce3+ active sites and then decompose into Ce3+-CO species for CO production, which was identified by in-situ FTIR. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B. V. and Science Press. All rights reserved.展开更多
The electrocatalytic activity and stability of Pt/C catalyst modified by using CeO_2-ZrO_2 mixed oxides for the alcohols electrochemical oxidation as probes were investigated. The catalyst samples were characterized b...The electrocatalytic activity and stability of Pt/C catalyst modified by using CeO_2-ZrO_2 mixed oxides for the alcohols electrochemical oxidation as probes were investigated. The catalyst samples were characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The electrochemical properties were measured by a three electrode system on electrochemical workstation（IVIUM）. The results showed that the presence of CeO_2-ZrO_2 might be associated with the presence of Pt, which indicated that possibly there was synergistic effect between CeO_2-ZrO_2 and Pt nanoparticles. The electrocatalytic activity and stability of Pt-MO_x/C（M=Ce, Zr） for methanol and ethanol oxidation was better than that of Pt-CeO_2/C, which was attributed to that CeO_2-ZrO_2 composited oxides enhanced oxygen mobility and promoted oxygen storage capacity（OSC）. Furthermore, the best performance was found when the molar ratio of CeO_2 to ZrO_2 was 2：1 for the oxidation of methanol and ethanol. The forward peak current density of Pt-MO_x/C（M=Ce, Zr, Ce：Zr=2：1） towards the methanol electrooxidation was about 3.8 times that of Pt-CeO_2/C. Pt-MO_x/C（M=Ce, Zr） appeared to be a promising and less expensive methanol oxidation anode catalyst.展开更多
The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based so...The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.展开更多
High surface area CeO2 was prepared by the surfactant-assisted route and was employed as catalyst support. The 0-3 at.% Cu doped Cu-Ni/CeO2 catalysts with 10 wt.% and 15 wt.% of total metal loading were prepared by an...High surface area CeO2 was prepared by the surfactant-assisted route and was employed as catalyst support. The 0-3 at.% Cu doped Cu-Ni/CeO2 catalysts with 10 wt.% and 15 wt.% of total metal loading were prepared by an impregnation-coprecipitation method. The influence of Cu atomic content on the catalytic performance was investigated on the steam reforming of ethanol （SRE） for H2 production and the catalysts were characterized by N2 adsorption, inductively coupled plasma （ICP）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, temperature-programmed rerduction （TPR） and H2-pulse chemisorption techniques. The activity and products distribution behaviors of the catalysts were significantly affected by the doped Cu molar content based on the promotion effect on the dispersion of NiO particles and the interactions between Cu-Ni metal and CeO2 support. Significant increase in the ethanol conversion and hydrogen selectivity were obtained when moderate Cu metal was doped into the Ni/CeO2 catalyst. Over both of the 10Ni98.5Cu1.5/CeO2 and 15Ni98.5Cu1.5/CeO2 catalysts, more than 80% of ethanol conversion and 60% of H2 selectivity were obtained in the ethanol steam-reforming when the reaction temperature was above 450 ℃.展开更多
The atomic structure of the active sites in Cu/CeO2 catalysts is intimately associated with the copper-ceria interaction. Both the shape of ceria and the loading of copper affect the chemical bonding of copper species...The atomic structure of the active sites in Cu/CeO2 catalysts is intimately associated with the copper-ceria interaction. Both the shape of ceria and the loading of copper affect the chemical bonding of copper species on ceria surfaces and the electronic and geometric character of the relevant interfaces. Nanostructured ceria, including particles(polyhedra), rods, and cubes, provides anchoring sites for the copper species. The atomic arrangements and chemical properties of the(111),(110) and(100) facets, preferentially exposed depending on the shape of ceria, govern the copper-ceria interactions and in turn determine their catalytic properties. Also, the metal loading significantly influences the dispersion of copper species on ceria with a specific shape, forming copper layers, clusters, and nanoparticles. Lower copper contents result in copper monolayers and/or bilayers while higher copper loadings lead to multi-layered clusters and faceted particles. The active sites are usually generated via interactions between the copper atoms in the metal species and the oxygen vacancies on ceria, which is closely linked to the number and density of surface oxygen vacancies dominated by the shape of ceria.展开更多
The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the propertie...The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the properties of CeO2-supported Co catalysts including the surface area, the crystallite size and the morphology of CeO2, the reduction degree of cobalt species and the adsorption performance of hydrogen and nitrogen. As a consequence, the samples promoted with an appropriate amount of Ba show higher ammonia synthesis rates, while the catalysts with high Ba loading or K promoter all exhibit low catalytic activities.展开更多
Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of...Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.展开更多
Pt-CeO2-ZrO2/MgO （Pt-CZ/MgO） catalysts with 0.8 wt% Pt, 3.0 wt% CeO2 and 3.0 wt% ZrO2 were prepared by wet impregnation method. Support MgO was obtained using ion exchange resin method or using commercial MgO. XRD, ...Pt-CeO2-ZrO2/MgO （Pt-CZ/MgO） catalysts with 0.8 wt% Pt, 3.0 wt% CeO2 and 3.0 wt% ZrO2 were prepared by wet impregnation method. Support MgO was obtained using ion exchange resin method or using commercial MgO. XRD, BET, SEM, TEM, DTA-TG and CO2-TPD were used to characterize the catalysts. CH4-CO2 reforming to synthesis gas （syngas） was performed to test the catalytic behavior of the catalysts. The catalyst Pt-CZ/MgO-IE（D） prepared using ion exchange resin exhibits more regular structure, smaller and more unique particle sizes, and stronger basicity than the catalyst Pt-CZ/MgO prepared from commercial MgO. At 1073 K and atmospheric pressure, Pt-CZ/MgO-IE（D） catalyst has a higher activity and greater stability than Pt-CZ/MgO catalyst for CH4-CO2 reforming reaction at high gas hourly space velocity of 36000 mL/（g.h） with a stoichiometric feed of CH4 and C02. Activity measurement and characterization results demonstrate that modification of the support using ion exchange resin method can promote the surface structural property and stability, therefore enhancing the activity and stability for CH4-CO2 reforming reaction.展开更多
A series of VOx/CeO2 catalysts we re synthesized via vanadia supported on ceria with different BET surface areas.The catalysts were employed to investigate the active sites for the selective catalytic reduction of NO ...A series of VOx/CeO2 catalysts we re synthesized via vanadia supported on ceria with different BET surface areas.The catalysts were employed to investigate the active sites for the selective catalytic reduction of NO with NH3(NH3-SCR).The kinetic results show that VOx/CeO2 catalysts exhibit nearly constant apparent activation energies(Ea),indicating the same SCR reaction mechanism.The V-O-Ce bridging modes and oligomeric VOx were identified and quantified by Raman,FT-IR and H2-TPR.The amounts of the V-O-Ce bridging modes calculated by H2-TPR are correlated to the NH3-SCR intrinsic reaction rates.The turnover frequencies(TOFs) show a constant value at the same temperature,which were calculated based on the number of V-O-Ce bridging modes of VOx/CeO2 catalysts.Therefore,it can be concluded that the V-O-Ce bridging modes are the active sites of VOx/CeO2 catalysts for the NH3-SCR reaction.展开更多
基金supported by the National Natural Science Foundation of China (NO. 20976013, 21006057)
文摘CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.
文摘A series of monolithic Ni/CeO_2-ZrO_2/γ-Al_2O_3 catalysts for the POM reaction were prepared. The activity test shows that the catalyst has the best performance when CeO_2-ZrO_2 content is 8 wt%.The synergistic actions between CeO_2-ZrO_2 and γ-Al_2O_3 improve highly catalytic activity by increasing CH_4 conversion, H_2 and CO selectivity. XPS analysis of the used catalyst indicates that there coexist Ce^(4+) and Ce^(3+).
基金support from the National Natural Science Foundation of China(22078134)State Key Laboratory of Clean and Efficient Coal Utilization of Taiyuan University of Technology(SKL2022006)Natural Science Foundation of Chongqing(CSTB2023NSCQ-MSX0162)are greatly appreciated for the work.
文摘Dry reforming of methane(DRM)converts CH4 and CO_(2) to syngas.Photothermal DRM,which integrates temperature and light,is a sustainable method for storing solar energy in molecules.However,challenges such as limited light absorption,low photocarrier separation efficiency,Ni sintering,and carbon deposition hinder DRM stability.Herein,we regulated Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance the optical characteristics while addressing Ni sintering and carbon deposition issues.The(3Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst had insufficient Ni content,while the(9Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst showed excessive carbon deposition,leading to lower stability compared to the(6Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst,which achieved CH4 and CO_(2) rates to 231.0 μmol gcat^(-1)s^(-1) and 294.3 μmol gcat^(-1)s^(-1) ,respectively,at 973 K,with only 0.2 wt.%carbon deposition and no Ni sintering.This work adjusted Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance DRM performance,which has implications for improving other reactions.
文摘The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal center renders it to exhibit electrochemical activity only under high overpotentials.Herein,we report P-and S-doped Ni single-atom catalysts,i.e.symmetric Ni_(1)/PN_(4)and asymmetric Ni1/SN_(3)C can exhibit high catalytic activity of CO_(2)reduction with stable potential windows.It is revealed that the key intermediate*COOH in CO_(2)electroreduction is stabilized by heteroatom doping,which stems from the upward shift of the axial d_(z2)orbital of the active metal Ni atom.Furthermore,we investigate the potential-dependent free energetics and dynamic properties at the electrochemical interface on the Ni1/SN3C catalyst using ab initio molecular dynamics simulations with a full explicit solvent model.Based on the potential-dependent microkinetic model,we predict that S-atom doped Ni SAC shifts the onset potential of CO_(2)electroreduction from–0.88 to–0.80 V vs.RHE,exhibiting better activity.Overall,this work provides an in-depth understanding of structure-activity relationships and atomic-level electrochemical interfaces of catalytic systems,and offers insights into the rational design of heteroatom-doped catalysts for targeted catalysis.
基金Project supported by the "863 Project" (2009AA06Z304 and 2009AA064801)
文摘Nickel and sulfate co-modified CeO2-ZrO2 catalysts were prepared by sol-gel method. The catalysts were characterized by XRD, FTIR, XPS, NH3 chemisorption and NH3-SCR activity tests. The results showed that the enhanced acidity of CeO2-ZrO2 catalysts by nickel and sulfate co-modification was responsible for the broadened temperature window and improved the selectivity to N2 in NH3-SCR deNOx. The introduction of nickel to CeO2-ZrO2 solid solutions resulted in more Ce3+ on surface of catalyst, leading to an in...
基金Project supported by National Natural Science Foundation of China (20773090, 20803049)the Specialized Research Fund for the Doctoral Program of Higher Education (20070610026, 200806100009)
文摘Ce-Zr-Al-Nd2O3 （CZAN） support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction （XRD）, low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction （H2-TPR） and X-ray photoelectron spectroscopy （XPS）. The Pd-only three-way catalysts （Pd-TWC） supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3＋ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.
基金National Natural Science Foundation of China (nos.21476226 and 21506204)National Key Projects for Fundamental Research and Development of China (2016YFB0600902)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB17020400)the Youth Innovation Promotion Association CAS for financial support
文摘Reverse water gas shift (RWGS) reaction can serve as a pivotal stage in the CO2 conversion processes, which is vital for the utilization of CO2. In this study, RWGS reaction was performed over Pt/CeO2 catalysts at the temperature range of 200-500 degrees C under ambient pressure. Compared with pure CeO2, Pt/CeO2 catalysts exhibited superior RWGS activity at lower reaction temperature. Meanwhile, the calculated TOF and E-a values are approximately the same over these Pt/CeO2 catalysts pretreated under various calcination conditions, indicating that the RWGS reaction is not affected by the morphologies of anchored Pt nanoparticles or the primary crystallinity of CeO2. TPR and XPS results indicated that the incorporation of Pt promoted the reducibility of CeO2 support and remarkably increased the content of Ce 3 + sites on the catalyst surface. Furthermore, the CO TPSR-MS signal under the condition of pure CO2 flow over Pt/CeO 2 catalyst is far lower than that under the condition of adsorbed CO2 with H-2 -assisted flow, revealing that CO2 molecules adsorbed on Ce3+ active sites have difficult in generating CO directly. Meanwhile, the adsorbed CO2 with the assistance of H-2 can form formate species easily over Ce3+ active sites and then decompose into Ce3+-CO species for CO production, which was identified by in-situ FTIR. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B. V. and Science Press. All rights reserved.
基金supported by National Natural Science Foundation of China(51474133,21407084)Talent Incubation Funding of School of Materials and Metallurgy(2014CY012)
文摘The electrocatalytic activity and stability of Pt/C catalyst modified by using CeO_2-ZrO_2 mixed oxides for the alcohols electrochemical oxidation as probes were investigated. The catalyst samples were characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The electrochemical properties were measured by a three electrode system on electrochemical workstation（IVIUM）. The results showed that the presence of CeO_2-ZrO_2 might be associated with the presence of Pt, which indicated that possibly there was synergistic effect between CeO_2-ZrO_2 and Pt nanoparticles. The electrocatalytic activity and stability of Pt-MO_x/C（M=Ce, Zr） for methanol and ethanol oxidation was better than that of Pt-CeO_2/C, which was attributed to that CeO_2-ZrO_2 composited oxides enhanced oxygen mobility and promoted oxygen storage capacity（OSC）. Furthermore, the best performance was found when the molar ratio of CeO_2 to ZrO_2 was 2：1 for the oxidation of methanol and ethanol. The forward peak current density of Pt-MO_x/C（M=Ce, Zr, Ce：Zr=2：1） towards the methanol electrooxidation was about 3.8 times that of Pt-CeO_2/C. Pt-MO_x/C（M=Ce, Zr） appeared to be a promising and less expensive methanol oxidation anode catalyst.
文摘The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.
基金Project supported by the National Natural Science Foundation (21076047)the Natural Science Foundation of Zhongkai University of Agriculture and Engineering (G3100026)
文摘High surface area CeO2 was prepared by the surfactant-assisted route and was employed as catalyst support. The 0-3 at.% Cu doped Cu-Ni/CeO2 catalysts with 10 wt.% and 15 wt.% of total metal loading were prepared by an impregnation-coprecipitation method. The influence of Cu atomic content on the catalytic performance was investigated on the steam reforming of ethanol （SRE） for H2 production and the catalysts were characterized by N2 adsorption, inductively coupled plasma （ICP）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, temperature-programmed rerduction （TPR） and H2-pulse chemisorption techniques. The activity and products distribution behaviors of the catalysts were significantly affected by the doped Cu molar content based on the promotion effect on the dispersion of NiO particles and the interactions between Cu-Ni metal and CeO2 support. Significant increase in the ethanol conversion and hydrogen selectivity were obtained when moderate Cu metal was doped into the Ni/CeO2 catalyst. Over both of the 10Ni98.5Cu1.5/CeO2 and 15Ni98.5Cu1.5/CeO2 catalysts, more than 80% of ethanol conversion and 60% of H2 selectivity were obtained in the ethanol steam-reforming when the reaction temperature was above 450 ℃.
文摘The atomic structure of the active sites in Cu/CeO2 catalysts is intimately associated with the copper-ceria interaction. Both the shape of ceria and the loading of copper affect the chemical bonding of copper species on ceria surfaces and the electronic and geometric character of the relevant interfaces. Nanostructured ceria, including particles(polyhedra), rods, and cubes, provides anchoring sites for the copper species. The atomic arrangements and chemical properties of the(111),(110) and(100) facets, preferentially exposed depending on the shape of ceria, govern the copper-ceria interactions and in turn determine their catalytic properties. Also, the metal loading significantly influences the dispersion of copper species on ceria with a specific shape, forming copper layers, clusters, and nanoparticles. Lower copper contents result in copper monolayers and/or bilayers while higher copper loadings lead to multi-layered clusters and faceted particles. The active sites are usually generated via interactions between the copper atoms in the metal species and the oxygen vacancies on ceria, which is closely linked to the number and density of surface oxygen vacancies dominated by the shape of ceria.
基金supported by National Natural Science Foundation of China(21776047,21203028)
文摘The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the properties of CeO2-supported Co catalysts including the surface area, the crystallite size and the morphology of CeO2, the reduction degree of cobalt species and the adsorption performance of hydrogen and nitrogen. As a consequence, the samples promoted with an appropriate amount of Ba show higher ammonia synthesis rates, while the catalysts with high Ba loading or K promoter all exhibit low catalytic activities.
文摘Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.
基金supported by the National Natural Science Foundation of China (No. 20873013)
文摘Pt-CeO2-ZrO2/MgO （Pt-CZ/MgO） catalysts with 0.8 wt% Pt, 3.0 wt% CeO2 and 3.0 wt% ZrO2 were prepared by wet impregnation method. Support MgO was obtained using ion exchange resin method or using commercial MgO. XRD, BET, SEM, TEM, DTA-TG and CO2-TPD were used to characterize the catalysts. CH4-CO2 reforming to synthesis gas （syngas） was performed to test the catalytic behavior of the catalysts. The catalyst Pt-CZ/MgO-IE（D） prepared using ion exchange resin exhibits more regular structure, smaller and more unique particle sizes, and stronger basicity than the catalyst Pt-CZ/MgO prepared from commercial MgO. At 1073 K and atmospheric pressure, Pt-CZ/MgO-IE（D） catalyst has a higher activity and greater stability than Pt-CZ/MgO catalyst for CH4-CO2 reforming reaction at high gas hourly space velocity of 36000 mL/（g.h） with a stoichiometric feed of CH4 and C02. Activity measurement and characterization results demonstrate that modification of the support using ion exchange resin method can promote the surface structural property and stability, therefore enhancing the activity and stability for CH4-CO2 reforming reaction.
基金Project supported by the National Key Research and Development Program (2017YFC0211302)China Huadian Science and Technology Institute (CHDI.KJ-20)。
文摘A series of VOx/CeO2 catalysts we re synthesized via vanadia supported on ceria with different BET surface areas.The catalysts were employed to investigate the active sites for the selective catalytic reduction of NO with NH3(NH3-SCR).The kinetic results show that VOx/CeO2 catalysts exhibit nearly constant apparent activation energies(Ea),indicating the same SCR reaction mechanism.The V-O-Ce bridging modes and oligomeric VOx were identified and quantified by Raman,FT-IR and H2-TPR.The amounts of the V-O-Ce bridging modes calculated by H2-TPR are correlated to the NH3-SCR intrinsic reaction rates.The turnover frequencies(TOFs) show a constant value at the same temperature,which were calculated based on the number of V-O-Ce bridging modes of VOx/CeO2 catalysts.Therefore,it can be concluded that the V-O-Ce bridging modes are the active sites of VOx/CeO2 catalysts for the NH3-SCR reaction.
