Development of Mixed-Counducting Ceramics For Gas Separation Applications

1998 ◽  
Vol 548 ◽  
Author(s):  
U. Balachandran ◽  
B. Ma ◽  
P.S. Maiya ◽  
J.T. Dusek ◽  
J.J. Picciolo ◽  
...  
Keyword(s):  
Gas Separation ◽  
Hydrogen Permeation ◽  
Electronic Conductivity ◽  
Ionic Conductivities ◽  
Ceramic Membranes ◽  
Oxygen Flux ◽  
Membrane Thickness ◽  
Conducting Oxides ◽  
Separation Membranes ◽  
Oxidation Of Methane

ABSTRACTMixed-conducting oxides are used in many applications, including fuel cells, gas separation membranes, sesors, and electrocatalysis. This paper describes mixed-conducting ceramic membranes that are being developed to selectively remove oxygen and hydrogen from gas streams in a nongalvanic mode of operation (i.e., with no electrodes or external power supply). Because of its high combined electronic/ionic conductivity and significant oxygen permeability, the mixed-coducting Sr-Fe-Co oxide (SFC) has been developed for high-purity oxygen separation and/or partial oxidation of methane to synthesis gas, i.e., syngas, a mixture of carbon monoxide and hydorgen. The electronic and ionic conductivities of SFC were found to be comparable in magnitude are presented as a function of temperature. The oxygen flux through dense SFC tubes during separation of oxygen from air is compared with the oxygen flux during methane conversion.Unlike SFC, in which the ionic and electronic conductivities are nearly equivalent, BaCe0.80Y0.20O3 (BCY) exhibits protonic conductivity that is significantly higher that its electronic coductivity. To enhance the electronic conductivity and increase hydrogen permeation, metal powder was combined with the BCY to form a cermet membrane. Nongalvanic permeation of hydrogen through the cermet memebrane was demonstrated and characterized as a function of membrane thickness. A sintering aid was developed to avoid interconnected porosity in and improve the mechanical properties of the cermet membrane.

The Thickness Dependence of Oxygen Permeability in Sol-Gel Derived Ce0.8Gd0.2O2-δ-CoFe2O4 Thin Films on Porous Ceramic Substrates: A Sputtered “Blocking Layer” for Thickness Control

2008 ◽  
Vol 1126 ◽  
Author(s):  
Kyle S. Brinkman ◽  
Takashi Iijima ◽  
Hitoshi Takamura
Keyword(s):  
Thin Film ◽  
Porous Ceramic ◽  
Sol Gel ◽  
Electronic Conductivity ◽  
Composite Membranes ◽  
Ceramic Membranes ◽  
Oxygen Flux ◽  
Membrane Thickness ◽  
Ceramic Substrates ◽  
Oxidation Of Methane

AbstractMixed conductive oxides are a topic of interest for applications in oxygen separation membranes as well as use in producing hydrogen fuel through the partial oxidation of methane. The oxygen flux through the membranes is governed both by the oxygen ionic conductivity as well as the material's electronic conductivity; composite membranes like Ce0.8Gd0.2O2-δ(CGO)-CoFe2O4 (CFO) use gadolinium doped ceria oxides as the ionic conducting material combined with cobalt iron spinel which serves as the electronic conductor. In this study we employ ˜ 50 nm sputtered CeO2 layers on the surface of porous CGO ceramic substrates which serve as solution ‘blocking’ layers during the thin film fabrication process facilitating the control of film thickness. Films with thickness of ˜ 2 and 4 microns were prepared by depositing 40 and 95 separate sol-gel layers respectively. Oxygen flux measurements indicated that the permeation increased with decreasing membrane thickness; thin film membrane with thickness on the micron level showed flux values an order of magnitude greater (0.03μmol/cm2 s) at 800oC as compared to 1mm thick bulk ceramic membranes (0.003 μmol/cm2).

Mixed-Conducting Membranes for Hydrogen Production and Separation

2006 ◽  
Vol 972 ◽  
Author(s):  
U. Balachandran ◽  
Beihai Ma ◽  
Tae H Lee ◽  
Sun-Ju Song ◽  
Ling Chen ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
Hydrogen Permeability ◽  
Composite Membranes ◽  
Ceramic Membranes ◽  
Electronic Charge ◽  
Membrane Thickness ◽  
Pure Hydrogen ◽  
Metal Composite ◽  
Proton Conducting ◽  
Conducting Oxides

AbstractMixed-conducting oxides, possessing both ionic and electronic charge carriers, have found wide application in recent years in solid-state electrochemical devices that operate at high temperatures, e.g., solid-oxide fuel cells, batteries, and sensors. These materials also hold promise as dense ceramic membranes that separate gases such as oxygen and hydrogen from mixed-gas streams. We are developing Sr-Fe-Co oxide (SFC) as a membrane that selectively transports oxygen during partial oxidation of methane to syngas (mixture of CO and H2) because of SFC's high combined electronic and ionic conductivities. We have evaluated extruded tubes of SFC for conversion of methane to syngas in a reactor that was operated at ≈900°C. Methane conversion efficiencies were >90%, and some of the reactor tubes were operated for >1000 h. We are also developing dense proton-conducting oxides to separate pure hydrogen from product streams that are generated during methane reforming and coal gasification. Hydrogen selectivity in these membranes is nearly 100%, because they are free of interconnected porosity. Although most studies of hydrogen separation membranes have focused on proton-conducting oxides by themselves, we have developed cermet (i.e., ceramic-metal composite) membranes in which metal powder is mixed with these oxides in order to increase their hydrogen permeability. Using several feed gas mixtures, we measured the nongalvanic hydrogen permeation rate, or flux, for the cermet membranes in the temperature range of 500-900°C. This rate varied linearly with the inverse of membrane thickness. The highest rate, ≈32 cm3(STP)/min-cm2, was measured at 900°C for an ≈15-μm-thick membrane on a porous support structure when 100% H2 at ambient pressure was used as the feed gas.

Electrical and Hydrogen Transport Properties of SrCe0.8Yb0.2O3−δ/Ni Cermet Membranes

2004 ◽  
Vol 835 ◽  
Author(s):  
S.-J. Song ◽  
T. H. Lee ◽  
L. Chen ◽  
C. Zuo ◽  
S. E. Dorris ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
Hydrogen Permeation ◽  
Electron Flow ◽  
Hydrogen Permeability ◽  
Permeation Rate ◽  
Hydrogen Separation ◽  
Metal Composite ◽  
Conducting Oxides ◽  
Separation Membranes ◽  
Increasing Demand

AbstractResearch on hydrogen separation membranes is motivated by the increasing demand for an environmentally benign, inexpensive technology for separating hydrogen from gas mixtures. Although most studies of hydrogen separation membranes have focused on proton-conducting oxides by themselves, the addition of metal to these oxides increases their hydrogen permeability and improves their mechanical stability. This study began by determining the electrical and hydrogen permeation properties of SrCe0.8Yb0.2O3−δ (SCYb). The results showed that the hydrogen permeation rate is limited by electron flow at the investigated temperatures (600 – 900°C). To further enhance hydrogen permeability, a cermet (i.e., ceramic-metal composite) membrane was made by adding Ni to the SCYb. The cermet showed no phase change after sintering in a reducing atmosphere. At 900°C, with 20% H2 /balance He as a feed gas (pH2O = 0.03 atm), the hydrogen permeation rate was 0.113 cm3/min-cm2 for Ni/SCYb (0.43-mm thick) and 0.008 cm3/min-cm2 for SCYb (0.7-mm thick). The dependences of hydrogen permeability on temperature, thickness, and hydrogen partial pressure gradients are also determined. The results demonstrate that adding Ni to SCYb considerably increases its hydrogen permeability by increasing its electron conductivity.

scholarly journals Crystal Structures of Mixed-Conducting Oxides Present in The Sr-Fe-Co-O System

1997 ◽  
Vol 496 ◽  
Author(s):  
J. P. Hodges ◽  
J. D. Jorgensen ◽  
D. J. Miller ◽  
B. Ma ◽  
U. Balachandran ◽  
...  
Keyword(s):  
Solid Oxide Fuel Cells ◽  
Elevated Temperatures ◽  
Ceramic Membranes ◽  
Rechargeable Batteries ◽  
Quantitative Phase Analysis ◽  
Ceramic Oxides ◽  
Conducting Oxides ◽  
Oxidation Of Methane ◽  
Dense Ceramic ◽  
Potential Applications

ABSTRACTThe potential applications of mixed-conducting ceramic oxides include solid-oxide fuel cells, rechargeable batteries, gas sensors and oxygen-permeable membranes. Several perovskite-derived mixed Sr-Fe-Co oxides show not only high electrical-conductivity but also appreciable oxygen-permeability at elevated temperatures. For example, dense ceramic membranes of SrFeCo0.5O3-δ can be used to separate oxygen from air without the need for external electrical circuitry. The separated oxygen can be directly used for the partial oxidation of methane to produce syngas. Quantitative phase analysis of the SrFeCo0.5O3-δ material has revealed that it is predominantly composed of two Sr-Fe-Co-O systems, Sr4Fe6-xCoxO13 and SrFe1−xCoxO3-δ. Here we report preliminary structural findings on the SrFe1−xCoxO3-δ (0 ≤ x ≥ 0.3) system.

scholarly journals Mitigating the Agglomeration of Nanofiller in a Mixed Matrix Membrane by Incorporating an Interface Agent

Membranes ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 328
Author(s):  
Manh-Tuan Vu ◽  
Gloria M. Monsalve-Bravo ◽  
Rijia Lin ◽  
Mengran Li ◽  
Suresh K. Bhatia ◽  
...  
Keyword(s):  
Gas Separation ◽  
Polymer Matrix ◽  
Ion Beam ◽  
High Surface ◽  
Mixed Matrix Membrane ◽  
Mechanical And Thermal Properties ◽  
Separation Membranes ◽  
Surface Areas ◽  
Separation Membrane ◽  
Focus Ion Beam

Nanodiamonds (ND) have recently emerged as excellent candidates for various applications including membrane technology due to their nanoscale size, non-toxic nature, excellent mechanical and thermal properties, high surface areas and tuneable surface structures with functional groups. However, their non-porous structure and strong tendency to aggregate are hindering their potential in gas separation membrane applications. To overcome those issues, this study proposes an efficient approach by decorating the ND surface with polyethyleneimine (PEI) before embedding it into the polymer matrix to fabricate MMMs for CO2/N2 separation. Acting as both interfacial binder and gas carrier agent, the PEI layer enhances the polymer/filler interfacial interaction, minimising the agglomeration of ND in the polymer matrix, which is evidenced by the focus ion beam scanning electron microscopy (FIB-SEM). The incorporation of PEI into the membrane matrix effectively improves the CO2/N2 selectivity compared to the pristine polymer membranes. The improvement in CO2/N2 selectivity is also modelled by calculating the interfacial permeabilities with the Felske model using the gas permeabilities in the MMM. This study proposes a simple and effective modification method to address both the interface and gas selectivity in the application of nanoscale and non-porous fillers in gas separation membranes.

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