Xiuxia Meng

Mixed ionic‐electronic conducting La_0.8Ca_0.2Fe_0.95O_3−δ‐Ag (LCF‐Ag) ceramic hollow fiber membranes possess high structural stability and up to 2.24‐fold higher oxygen permeation fluxes relative to LCF hollow fibers. In this work, the oxygen permeation of LCF‐Ag hollow fiber membrane module is simulated under sweep gas and vacuum operation modes, whereas the kinetic parameters were obtained by fitting the experimental data with the simplified Tan–Li model. The good correlation obtained from the data regression confirmed the compatibility of the selected model on the LCF‐Ag hollow fiber membrane. The simulated results revealed that the countercurrent flow configuration is generally favored in sweep gas operation given its potential of complete oxygen separation under optimized conditions. For vacuum operation, the oxygen yield is practically the same for both flow configurations at a moderate vacuum setting. At a very low vacuum pressure setting, however, cocurrent flow is preferred over countercurrent flow for maximizing the oxygen yield.

Ce_0.85Sm_0.15O_1.925–Sm_0.6Sr_0.4Al_0.3Fe_0.7O_3‐δ (SDC‐SSAF) hollow fiber membranes aimed for oxyfuel application are fabricated via a phase inversion‐sintering technique using powders synthesized from EDTA–citrate complex method. Oxygen ions transport is revealed to be the limiting step that determines the overall oxygen transport rate in SDC‐SSAF. SDC‐SSAF hollow fiber membrane attained a maximum flux of 2.6 ml min⁻¹ cm⁻² at 950°C under an oxygen partial pressure difference of 1/0.02 atm (feed/permeate). Variation in oxygen partial pressure on the permeate side exerts larger influence on the oxygen permeation flux relative to the change on the feed side. Stability tests over 100 h demonstrate stable oxygen permeation flux under both He and CO₂ sweep conditions.

Clarifying the mechanism for the gas transportation in the emerging 2D materials-based membranes plays an important role on the design and performance optimization. In this work, the corresponding studies were conducted experimentally and theoretically. To this end, we measured the gas permeances of hydrogen and nitrogen from their mixture through the supported MXene lamellar membrane. Knudsen diffusion and molecular sieving through straight and tortuous nanochannels were proposed to elucidate the gas transport mechanism. The average pore diameter of 5.05 Å in straight nanochannels was calculated by linear regression in the Knudsen diffusion model. The activation energy for H₂ transport in molecular sieving model was calculated to be 20.54 kJ mol⁻¹. From the model, we can predict that the gas permeance of hydrogen (with smaller kinetic diameter) is contributed from both Knudsen diffusion and molecular sieving mechanism, but the permeance of larger molecular gases like nitrogen is sourced from Knudsen diffusion. The effects of the critical conditions such as temperature, the diffusion pore diameter of structural defects, and the thickness of the prepared MXene lamellar membrane on hydrogen and nitrogen permeance were also investigated to understand the hydrogen permeation difference from Knudsen diffusion and molecular sieving. At room temperature, the total hydrogen permeance was contributed 18% by Knudsen diffusion and 82% by molecular sieving. The modeling results indicate that molecular sieving plays a dominant role in controlling gas selectivity.

In this work, hydrogen (H₂) permeation fluxes through 230 nm‐thick graphene oxide (GO) membrane deposited on porous YSZ hollow fiber were measured and correlated to an explicit H₂ permeation model. H₂ fluxes through such GO‐YSZ hollow fiber membrane increased from 4.83 × 10⁻⁸ mol cm⁻² s⁻¹ to 2.11 × 10⁻⁷ mol cm⁻² s⁻¹ with temperature rise from 20 to 100 °C. The activation energy of H₂ permeation was determined by the linear regression of the experimental data and was applied in the theoretical calculations. The model predictions fit well the temperature dependent and the argon sweep gas flow rate dependent H₂ fluxes data. Using the derived permeation model, the effects of vacuum pressure at lumen side and H₂ partial pressure at shell side, membrane area, and GO membrane film thickness on the membrane performance were simulated and discussed to provide insights for practical applications. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2711–2720, 2018