Solid oxide membrane-assisted electrolytic reduction of solid Cr_(2)O_(3) to Cr in molten CaCl_(2) was performed using a sintered porous Cr_(2)O_(3) cathode paired with an yttria-stabilized zirconia(YSZ)tube anode con...Solid oxide membrane-assisted electrolytic reduction of solid Cr_(2)O_(3) to Cr in molten CaCl_(2) was performed using a sintered porous Cr_(2)O_(3) cathode paired with an yttria-stabilized zirconia(YSZ)tube anode containing carbon-saturated liquid copper alloy.Analyses of the reduction mechanism,ion migration behavior,and effects of cathode pellet porosity and particle size on the electrolysis products and reduction rate revealed that the cathode microstructure and electrolytic conditions were key factors influencing the electrolysis process.Optimal results were obtained when the cathode was characterized by high porosity and a small particle size because this combination of features contributed to ion migration.Good electrochemical activation was observed when cathode pellets prepared by 4 MPa molding followed by 2 h of sintering at 1150℃ were applied.The electrode reduction process(Cr^(3+)→Cr^(2+)→Cr)was promoted by high electrode voltages,and Cr metal was efficiently formed.The proposed method appears to be well suited for electrolytic Cr production because it does not require expensive pre-electrolysis techniques or generate harmful by-products.展开更多
Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0＜x＜1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examin...Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0＜x＜1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examined in a fixed-bed reactor. The former group presented higher activity in the OCM, but the main product was carbon dioxide. While the later group showed lower activity but much higher selectivity to C2 hydrocarbons compared with the former. Electrochemical measurements were conducted in a solid oxide membrane reactor with La0.8 Na0.2CoO3 as catalyst. The results showed that methane was oxidized to carbon dioxide and ethane by two parallel reactions. Ethane was oxidized to ethene and carbon dioxide. A fraction of ethene was oxidized deeply to carbon dioxide. The total selectivity to C2 hydrocarbons exceeded 70%. Based on the experimental results, a kinetic model was suggested to describe the reaction results.展开更多
In the field of modern hydrogen energy,obtaining pure hydrogen and syngas and then being able to use them for green energy production are significant problems.Developing solid oxide fuel cells(SOFC)and catalytic membr...In the field of modern hydrogen energy,obtaining pure hydrogen and syngas and then being able to use them for green energy production are significant problems.Developing solid oxide fuel cells(SOFC)and catalytic membranes for oxygen separation as well as materials for these devices is one of the most likely ways to solve these problems.In this work,the authors’recent studies in this field are reviewed;the fundamentals of developing materials for SOFC cathodes and oxygen separation membranes’permselective layers based on research of their oxygen mobility and surface reactivity are presented.Ruddlesden-Popper phases Ln_(2-x)Ca_(x)NiO_(4+δ)(LnCNO)and perovskite-fluorite nanocomposites PrNi_(0.5)Co_(0.5)O_(3-δ)-Ce_(0.9)Y_(0.1)O_(2-δ)(PNC-YDC)were studied by isotope exchange of oxygen with C_(18)O_(2)and^(18)O_(2)in flow and closed reactors.For LnCNO a high oxygen mobility was shown(D*~10^(-7)cm^(2)/s at 700℃),being provided by the cooperative mechanism of oxygen migration involving both regular and highly-mobile interstitial oxygen.For PNC-YDC dominated a wide fast diffusion channel via fluorite phase and interphases due to features of the redistribution of cations resulting in superior oxygen mobility(D*~10^(-8)cm^(2)/s at 700℃).After optimization of composition and nanodomain structure of these materials,as cathodes of SOFC they provided a high power density,while for asymmetric supported oxygen separation membranes-a high oxygen permeability.展开更多
基金the National Natural Science Foundation of China(Nos.51664005,51774102,U1812402,and 51804088)Talents of Guizhou Science and Technology Cooperation Platform(Platform Talent[2017]5626 and KY(2015)334)。
文摘Solid oxide membrane-assisted electrolytic reduction of solid Cr_(2)O_(3) to Cr in molten CaCl_(2) was performed using a sintered porous Cr_(2)O_(3) cathode paired with an yttria-stabilized zirconia(YSZ)tube anode containing carbon-saturated liquid copper alloy.Analyses of the reduction mechanism,ion migration behavior,and effects of cathode pellet porosity and particle size on the electrolysis products and reduction rate revealed that the cathode microstructure and electrolytic conditions were key factors influencing the electrolysis process.Optimal results were obtained when the cathode was characterized by high porosity and a small particle size because this combination of features contributed to ion migration.Good electrochemical activation was observed when cathode pellets prepared by 4 MPa molding followed by 2 h of sintering at 1150℃ were applied.The electrode reduction process(Cr^(3+)→Cr^(2+)→Cr)was promoted by high electrode voltages,and Cr metal was efficiently formed.The proposed method appears to be well suited for electrolytic Cr production because it does not require expensive pre-electrolysis techniques or generate harmful by-products.
基金This work was supported supported by the Center Petrochemical Company of China (X599027).
文摘Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0＜x＜1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examined in a fixed-bed reactor. The former group presented higher activity in the OCM, but the main product was carbon dioxide. While the later group showed lower activity but much higher selectivity to C2 hydrocarbons compared with the former. Electrochemical measurements were conducted in a solid oxide membrane reactor with La0.8 Na0.2CoO3 as catalyst. The results showed that methane was oxidized to carbon dioxide and ethane by two parallel reactions. Ethane was oxidized to ethene and carbon dioxide. A fraction of ethene was oxidized deeply to carbon dioxide. The total selectivity to C2 hydrocarbons exceeded 70%. Based on the experimental results, a kinetic model was suggested to describe the reaction results.
基金the Russian Science Foundation(Project 16-13-00112)the budget project#AAAA-A17-117041110045-9 for Boreskov Institute of Catalysis is gratefully acknowledged.
文摘In the field of modern hydrogen energy,obtaining pure hydrogen and syngas and then being able to use them for green energy production are significant problems.Developing solid oxide fuel cells(SOFC)and catalytic membranes for oxygen separation as well as materials for these devices is one of the most likely ways to solve these problems.In this work,the authors’recent studies in this field are reviewed;the fundamentals of developing materials for SOFC cathodes and oxygen separation membranes’permselective layers based on research of their oxygen mobility and surface reactivity are presented.Ruddlesden-Popper phases Ln_(2-x)Ca_(x)NiO_(4+δ)(LnCNO)and perovskite-fluorite nanocomposites PrNi_(0.5)Co_(0.5)O_(3-δ)-Ce_(0.9)Y_(0.1)O_(2-δ)(PNC-YDC)were studied by isotope exchange of oxygen with C_(18)O_(2)and^(18)O_(2)in flow and closed reactors.For LnCNO a high oxygen mobility was shown(D*~10^(-7)cm^(2)/s at 700℃),being provided by the cooperative mechanism of oxygen migration involving both regular and highly-mobile interstitial oxygen.For PNC-YDC dominated a wide fast diffusion channel via fluorite phase and interphases due to features of the redistribution of cations resulting in superior oxygen mobility(D*~10^(-8)cm^(2)/s at 700℃).After optimization of composition and nanodomain structure of these materials,as cathodes of SOFC they provided a high power density,while for asymmetric supported oxygen separation membranes-a high oxygen permeability.
