The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface are...The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m^2·g^(-1), and that calcined at 900 ℃ for 6 h is 88 m^2·g^(-1). The sample with tetragonal symmetry Ce_(0.5)Zr_(0.5)O_2 phase has a higher stability.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
A Pt-Rh three-way catalyst（M-DS） supported on CeO_2-ZrO_2-La_2O_3-Nd_2O_3 and its analogous supported catalyst（DS） were developed via a modified double-solvent method and conventional double-solvent method, respec...A Pt-Rh three-way catalyst（M-DS） supported on CeO_2-ZrO_2-La_2O_3-Nd_2O_3 and its analogous supported catalyst（DS） were developed via a modified double-solvent method and conventional double-solvent method, respectively. The as-prepared catalysts were characterized by N_2 adsorption-desorption, X-ray diffraction（XRD）, CO-chemisorption, X-ray photoelectron spectroscopy（XPS） and hydrogen temperature-programmed reduction（H_2-TPR）. The preformed Pt nanoparticles generated using ethanol as a reducing agent on M-DS presented enhanced Pt dispersion regardless of aging treatment as confirmed by XRD and CO-chemisorption measurements. The textural properties and reduction ability of M-DS were maintained to a large extent after aging treatment. This result was consistent with those of the N_2 adsorption-desorption and H_2-TPR, respectively. Meanwhile, the XPS analysis demonstrated that higher Pt^0 species and larger Ce^（3＋） concentration could be obtained for M-DS. In the conversion of a simulated compressed natural gas（CNG） vehicle exhaust, both fresh and aged M-DS showed a significant enhancement in the activity and N_2-selectivity. Particularly, the complete conversion temperature（T_（90）） of CH_4 over the aged M-DS catalyst was 65 oC lower than that over the aged catalyst by conventional double-solvent method.展开更多
The morphologies of CuO/CeO_(2)-ZrO_(2) catalysts were successfully controlled by simply changing the synthesis temperature using hydrothermal method.The catalytic performance for toluene oxidation was correlated with...The morphologies of CuO/CeO_(2)-ZrO_(2) catalysts were successfully controlled by simply changing the synthesis temperature using hydrothermal method.The catalytic performance for toluene oxidation was correlated with the characterization results of HRTEM,BET,XRD,H2-TPR,Raman,and O_(2)-TPD.It was found that toluene can be oxidized into CO_(2) and H2O completely over the obtained catalysts,and the rod-like Cu/Ce-Zr-100 exhibits the best activity and CO_(2) selectivity.The rod-like CeO_(2)-ZrO_(2) supports preferentially exposes(110)and(100)crystal planes of CeO_(2),which provides more oxygen vacancies and stronger interaction between CuO and the support in Cu/Ce-Zr-100.And the strong synergetic effect in Cu/Ce-Zr-100 promotes the dispersion of CuO on the support surface,leading to the enhancement of reducibility,oxygen vacancy concentration,adsorption and activation of gaseous oxygen,which are responsible for the good catalytic performance of toluene oxidation.展开更多
With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles,new challenges have arisen for the low-temperature performance of three-way catalysts(...With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles,new challenges have arisen for the low-temperature performance of three-way catalysts(TWCs).To guide the design of next-generation TWCs,it is essential to further develop our understanding of the relationships between microstructure and catalytic performance.Here,Rh/CeO_(2)–ZrO_(2) catalysts were synthesized with different Rh metal dispersion by using a combination of the wet impregnation method and reduction treatment.These catalysts included Rh single-atom catalysts,cluster catalysts,and nanoparticle catalysts.The results showed that the Rh nanoparticle catalyst,with an average size of 1.9 nm,exhibited superior three-way catalytic performance compared to the other catalysts.Based on the catalytic activity in a series of simple reaction atmospheres such as CO+O_(2),NO+CO,and hydrocarbons(HCs)+O_(2) and operando infrared spectroscopy,we found that metallic Rh sites on Rh nanoparticles are the key factor responsible for the low-temperature catalytic performance.展开更多
To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,opti...To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,optical and adsorption properties of ternary mixed oxide CeO_(2)-ZrO_(2)-Al_(2) O_3(CZA) are investigated.The ternary mixed oxide CZA was prepared by surfactants or mixed surfactants assisted ultrasonic coprecipitation method.The physicochemical and optical properties are estimated by different techniques like XRD,TEM,EDX,FTIR,S_(BET) and UV-Vis/DR.The CZA_T and CZA_C have hybrid shapes and high surface area.The adsorption properties of ternary mixed oxides adsorbents were characterized by sono-removing anionic dyes such as Congo red(CR) and Remazol red RB-133(RR).The different factors like contact time,different dye concentrations and temperatures also studied.The kinetics and isotherms applications showed that,the adsorption process was followed pseudo second order kinetics and the Freundlich isotherm model.Also,the adsorption is spontaneous and endothermic process through the thermodynamic study.Finally,the results showed that the ternary mixed oxide nano-adsorbent(CeO_(2)-ZrO_(2)-Al_(2) O_3) is promising and functional materials for anionic dye sweep from wastewater.展开更多
The nanostructures and redox properties of CeO_(2)-ZrO_(2)materials can be tuned via optimized thermal treatments.In this study,the CeO_(2)-ZrO_(2)-Y_(2)O_(3)-La_(2)O_(3)(CZ) materials were prepared by co-precipitatio...The nanostructures and redox properties of CeO_(2)-ZrO_(2)materials can be tuned via optimized thermal treatments.In this study,the CeO_(2)-ZrO_(2)-Y_(2)O_(3)-La_(2)O_(3)(CZ) materials were prepared by co-precipitation method and submitted to different thermal treatment conditions(atmosphere:nitrogen(N) and air(A);temperature(x):700,800 and 900℃).Due to the protective effects of the "in-situ-formed" carbon powder,treating the surfactants assisted-CZ precursors under N2atmosphere can keep the pore structures and then the CZ-N700 and CZ-N800 can achieve larger surface area than CZ-A700 and CZ-A800,respectively.In comparison,with high treatment temperature(900℃),the effects of thermal atmosphere on surface area can be ignored.However,the redox properties of CZ materials correlate closely with thermal treatment atmosphere and temperature simultaneously.As demonstrated by X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) characterizations,the N_(2)atmosphere facilitates the formation of Ce^(3+)without disturbing the mixing degree of Ce and Zr.Thereby the CZ-Nx materials exhibit superior reducibility than corresponding CZ-Ax materials.In additio n,the XRD and XPS results also demonstrate the formation of a more homogeneous CZ solid solution by Zr atoms rearrangement with temperature ignoring the atmosphere.As a result,the reducibility of CZ materials increases with the treatment temperature increasing and is not affected by the worsening of the textural properties.Specially,due to the synergistic effects of N_(2)atmosphere and high treatment temperature,the CZ-N900 shows the best reducibility.This improvement also emphasizes the important role of structural properties of CZ in explaining the temperature-dependent reducibility.展开更多
The activity and hydrothermal stability of the Rh/Ce_(x)Zr_(1-x)O_(2)(x=0,0.05,0.3,0.5) model three-way catalysts for gasoline vehicle emissions control were investigated in this work.Among the Rh/Ce_(x)Zr_(1-x)O_(2) ...The activity and hydrothermal stability of the Rh/Ce_(x)Zr_(1-x)O_(2)(x=0,0.05,0.3,0.5) model three-way catalysts for gasoline vehicle emissions control were investigated in this work.Among the Rh/Ce_(x)Zr_(1-x)O_(2) samples with different Ce/Zr ratios,the Rh/ZrO_(2) sample exhibits a significantly better activity and hydrothermal stability than the rest of the samples.The impacts of having more Ce components in the Rh/Ce_(x)Zr_(1-x)O_(2) catalysts are associated with the strong Rh-O-Ce interaction that tends to over stabilize the rhodium species.A significant amount of such rhodium atoms can be found in the bulk of the support oxides after a hydrothermal aging at 1050℃ with 10% H_(2)O in air for 12 h.Differently,the sintering of rhodium on the surface of Rh/ZrO_(2) catalysts is the main reason for the catalyst deactivation during the hydrothermal aging.These findings provide an example where high dispersion of supported metal induced by strong metal-support interactions does not necessarily lead to high catalytic activity.展开更多
文摘The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m^2·g^(-1), and that calcined at 900 ℃ for 6 h is 88 m^2·g^(-1). The sample with tetragonal symmetry Ce_(0.5)Zr_(0.5)O_2 phase has a higher stability.
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supported by the National Natural Science Foundation of China(21173153)National High-Tech Research and Development Program of China(863)(2013AA065304)~~
基金supported by the National Key Research and Development Program of China(2016YFC0204902)
文摘A Pt-Rh three-way catalyst（M-DS） supported on CeO_2-ZrO_2-La_2O_3-Nd_2O_3 and its analogous supported catalyst（DS） were developed via a modified double-solvent method and conventional double-solvent method, respectively. The as-prepared catalysts were characterized by N_2 adsorption-desorption, X-ray diffraction（XRD）, CO-chemisorption, X-ray photoelectron spectroscopy（XPS） and hydrogen temperature-programmed reduction（H_2-TPR）. The preformed Pt nanoparticles generated using ethanol as a reducing agent on M-DS presented enhanced Pt dispersion regardless of aging treatment as confirmed by XRD and CO-chemisorption measurements. The textural properties and reduction ability of M-DS were maintained to a large extent after aging treatment. This result was consistent with those of the N_2 adsorption-desorption and H_2-TPR, respectively. Meanwhile, the XPS analysis demonstrated that higher Pt^0 species and larger Ce^（3＋） concentration could be obtained for M-DS. In the conversion of a simulated compressed natural gas（CNG） vehicle exhaust, both fresh and aged M-DS showed a significant enhancement in the activity and N_2-selectivity. Particularly, the complete conversion temperature（T_（90）） of CH_4 over the aged M-DS catalyst was 65 oC lower than that over the aged catalyst by conventional double-solvent method.
基金the financial support from the National Natural Science Foundation of China(No 51776216)the Postdoctoral Science Foundation of China(No.2017 M623284).
文摘The morphologies of CuO/CeO_(2)-ZrO_(2) catalysts were successfully controlled by simply changing the synthesis temperature using hydrothermal method.The catalytic performance for toluene oxidation was correlated with the characterization results of HRTEM,BET,XRD,H2-TPR,Raman,and O_(2)-TPD.It was found that toluene can be oxidized into CO_(2) and H2O completely over the obtained catalysts,and the rod-like Cu/Ce-Zr-100 exhibits the best activity and CO_(2) selectivity.The rod-like CeO_(2)-ZrO_(2) supports preferentially exposes(110)and(100)crystal planes of CeO_(2),which provides more oxygen vacancies and stronger interaction between CuO and the support in Cu/Ce-Zr-100.And the strong synergetic effect in Cu/Ce-Zr-100 promotes the dispersion of CuO on the support surface,leading to the enhancement of reducibility,oxygen vacancy concentration,adsorption and activation of gaseous oxygen,which are responsible for the good catalytic performance of toluene oxidation.
基金supported by the National Key Research and Development Program of China(No.2022YFB3504202)the National Natural Science Foundation of China(No.52204376)Youth Foundation of Hebei Province(No.E2022103007).
文摘With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles,new challenges have arisen for the low-temperature performance of three-way catalysts(TWCs).To guide the design of next-generation TWCs,it is essential to further develop our understanding of the relationships between microstructure and catalytic performance.Here,Rh/CeO_(2)–ZrO_(2) catalysts were synthesized with different Rh metal dispersion by using a combination of the wet impregnation method and reduction treatment.These catalysts included Rh single-atom catalysts,cluster catalysts,and nanoparticle catalysts.The results showed that the Rh nanoparticle catalyst,with an average size of 1.9 nm,exhibited superior three-way catalytic performance compared to the other catalysts.Based on the catalytic activity in a series of simple reaction atmospheres such as CO+O_(2),NO+CO,and hydrocarbons(HCs)+O_(2) and operando infrared spectroscopy,we found that metallic Rh sites on Rh nanoparticles are the key factor responsible for the low-temperature catalytic performance.
文摘To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,optical and adsorption properties of ternary mixed oxide CeO_(2)-ZrO_(2)-Al_(2) O_3(CZA) are investigated.The ternary mixed oxide CZA was prepared by surfactants or mixed surfactants assisted ultrasonic coprecipitation method.The physicochemical and optical properties are estimated by different techniques like XRD,TEM,EDX,FTIR,S_(BET) and UV-Vis/DR.The CZA_T and CZA_C have hybrid shapes and high surface area.The adsorption properties of ternary mixed oxides adsorbents were characterized by sono-removing anionic dyes such as Congo red(CR) and Remazol red RB-133(RR).The different factors like contact time,different dye concentrations and temperatures also studied.The kinetics and isotherms applications showed that,the adsorption process was followed pseudo second order kinetics and the Freundlich isotherm model.Also,the adsorption is spontaneous and endothermic process through the thermodynamic study.Finally,the results showed that the ternary mixed oxide nano-adsorbent(CeO_(2)-ZrO_(2)-Al_(2) O_3) is promising and functional materials for anionic dye sweep from wastewater.
基金Project supported by the National Natural Science Foundation of China (21972097)the National Engineering Laboratory for Mobile Source Emission Control Technology (NELMS2020A04)。
文摘The nanostructures and redox properties of CeO_(2)-ZrO_(2)materials can be tuned via optimized thermal treatments.In this study,the CeO_(2)-ZrO_(2)-Y_(2)O_(3)-La_(2)O_(3)(CZ) materials were prepared by co-precipitation method and submitted to different thermal treatment conditions(atmosphere:nitrogen(N) and air(A);temperature(x):700,800 and 900℃).Due to the protective effects of the "in-situ-formed" carbon powder,treating the surfactants assisted-CZ precursors under N2atmosphere can keep the pore structures and then the CZ-N700 and CZ-N800 can achieve larger surface area than CZ-A700 and CZ-A800,respectively.In comparison,with high treatment temperature(900℃),the effects of thermal atmosphere on surface area can be ignored.However,the redox properties of CZ materials correlate closely with thermal treatment atmosphere and temperature simultaneously.As demonstrated by X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) characterizations,the N_(2)atmosphere facilitates the formation of Ce^(3+)without disturbing the mixing degree of Ce and Zr.Thereby the CZ-Nx materials exhibit superior reducibility than corresponding CZ-Ax materials.In additio n,the XRD and XPS results also demonstrate the formation of a more homogeneous CZ solid solution by Zr atoms rearrangement with temperature ignoring the atmosphere.As a result,the reducibility of CZ materials increases with the treatment temperature increasing and is not affected by the worsening of the textural properties.Specially,due to the synergistic effects of N_(2)atmosphere and high treatment temperature,the CZ-N900 shows the best reducibility.This improvement also emphasizes the important role of structural properties of CZ in explaining the temperature-dependent reducibility.
基金Project supported by the National Key Research and Development Program(2017YFC0211003)GM Global Research and Development(GAC 2696)。
文摘The activity and hydrothermal stability of the Rh/Ce_(x)Zr_(1-x)O_(2)(x=0,0.05,0.3,0.5) model three-way catalysts for gasoline vehicle emissions control were investigated in this work.Among the Rh/Ce_(x)Zr_(1-x)O_(2) samples with different Ce/Zr ratios,the Rh/ZrO_(2) sample exhibits a significantly better activity and hydrothermal stability than the rest of the samples.The impacts of having more Ce components in the Rh/Ce_(x)Zr_(1-x)O_(2) catalysts are associated with the strong Rh-O-Ce interaction that tends to over stabilize the rhodium species.A significant amount of such rhodium atoms can be found in the bulk of the support oxides after a hydrothermal aging at 1050℃ with 10% H_(2)O in air for 12 h.Differently,the sintering of rhodium on the surface of Rh/ZrO_(2) catalysts is the main reason for the catalyst deactivation during the hydrothermal aging.These findings provide an example where high dispersion of supported metal induced by strong metal-support interactions does not necessarily lead to high catalytic activity.
