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Partovi K.,Institute of Physical Chemistry and Electrochemistry | Geppert B.,Institute of Physical Chemistry and Electrochemistry | Liang F.,Institute of Physical Chemistry and Electrochemistry | Ruscher C.H.,Leibniz University of Hanover | Caro J.,Leibniz University of Hanover
Chemistry of Materials | Year: 2015

Dense single-phase perovskite-type Pr0.6Sr0.4CoxFe1-xO3-δ (0.0 ≤ x ≤ 1.0) membranes (0.6 mm thick) were synthesized via EDTA-citric acid complexing route. Subsequently, the effect of various B-site Co/Fe compositions on oxygen permeability, temperature-dependent CO2 stability, microstructure, and electrical properties of the membranes were studied. The crystal structures and the high-temperature phase stability of the perovskite structure in a CO2-containing atmosphere were analyzed using X-ray diffraction. The highest oxygen permeation flux was observed for Pr0.6Sr0.4CoO3-δ with 1.57 cm3(STP) min-1 cm-2 and 1.37 cm3(STP) min-1 cm-2 at 1000 °C under air/He and air/CO2 gradients, respectively. Furthermore, the effect of CO2 as the sweep gas on the temperature-dependent oxygen permeability and stability of the membranes was studied. Basically, the membranes with lower Co contents were found to be less susceptible to CO2 exposure and their microstructures were less affected by CO2. The partial oxidation of methane (POM) to syngas was successfully performed for more than 80 h at 950 °C using a PSCF membrane with a Co content of x = 0.2. The POM reaction shows an average CH4 conversion rate of >98% and a CO selectivity of >95%. © 2015 American Chemical Society.

Li Y.,Institute of Physical Chemistry and Electrochemistry | Li Y.,CAS Dalian Institute of Chemical Physics | Liang F.,Institute of Physical Chemistry and Electrochemistry | Bux H.,Institute of Physical Chemistry and Electrochemistry | And 2 more authors.
Journal of Membrane Science | Year: 2010

Hydrogen-based energy system could address issues related to global climate change, energy security, and local air pollution. Thermally and hydrothermally stable microporous membranes with intrinsic high H2/CO2 selectivity are highly demanded. A novel zeolitic imidazolate framework (ZIF-7) membrane was tested for its gas separation performance. ZIFs are microporous materials and belong to the new class of metal-organic frameworks (MOFs). ZIF-7 is formed by bridging benzimidazolate anions and zinc cations resulting in a sodalite (SOD) topology with a pore size of about 0.3 nm. The ZIF-7 membrane exhibited promising H2 separation abilities. At 220 °C, the H2 permeance is ∼4.5 × 10-8 mol m-2 s-1 Pa-1 and the mixture separation factors for H2/CO2, H2/N2, and H2/CH4 are 13.6, 18.0, and 14.0, respectively. As a result of molecular sieving mechanism, the ideal selectivities and mixture separation factors are identical. The permeation of H2 through the ZIF-7 membrane is highly activated with an apparent activation energy of 11.9 kJ mol-1. Due to the ultra-hydrophobic properties of ZIF materials, the ZIF-7 membrane also showed excellent hydrothermal stability in the presence of steam. Our results clearly demonstrate that ZIF-7 membranes have an intrinsic high H2/CO2 selectivity and a promising application in hydrogen separation, which is based on its very narrow and well-defined crystal pore structure. © 2010 Elsevier B.V. All rights reserved.

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