Dense cermet membranes for hydrogen separation

Abstract

Argonne National Laboratory (ANL) and the National Energy Technology Laboratory (NETL) are developing dense ceramic-based membranes for separating hydrogen from the products of coal gasification and other partial-oxidation streams. Hydrogen separation with these membranes is nongalvanic, i.e., it does not use electrodes or an external power supply to drive the separation, and hydrogen selectivity is nearly 100% because the membranes contain no interconnected porosity.Novel cermet (i.e., ceramic-metal composite) membranes have been developed to separate hydrogen from gas mixtures at high temperature and pressure. Hydrogen permeation rates have been measured in the temperature range of 600-900°C for three classes of cermet membranes (ANL-1, -2, and -3). ANL-3a membranes, with a thickness of 40 µm, provide the highest hydrogen flux (≈20 cm 3 [STP]/min-cm 2 at 900°C with 100% H 2 as the feed gas). The effects of membrane thickness and hydrogen partial pressure on hydrogen flux indicate that the bulk diffusion of hydrogen is rate-limiting in ANL-3 membranes with a thickness >40 µm. ANL-3b membranes were tested in simulated syngas at several temperatures, and no performance degradation was observed for times that approached ≈200 h; this observation suggests that the membrane is chemically stable and may be suitable for long-term operation. The performance of membranes in separating hydrogen from high-pressure gas streams is being evaluated with NETL's in-house R&D facilities. The present status of membrane development at ANL/NETL will be presented in this paper.

SrCe0.95Y0.05O3−δ–ZnO dual-phase membranes for hydrogen permeation

“…This can be achieved by adding another percolative phase with high electronic conductivity such as metal (e.g., Ni, Ag, Pd, Au or Pt) or perovskite with prevailing electronic conductivity. 19,20 Enhanced hydrogen uxes have indeed been achieved in such dual-phase membranes, e.g., Ni-Ba(Zr 0.1 Ce 0.7 Y 0.2 )O 3 , Ni-BaCe 0.95 Tb 0.05 -O 3Àd , BaCe 0.8 Y 0.2 O 3Àd -Ni and Ce 0.8 (Sm 0.8 Sr 0.2 ) 0.2 O 2Àd -SrTi 0.5 -Fe 0.5 O 3Àd . [21][22][23][24] The future trend would be to move away from precious metals considering their high cost.…”

On the manufacture of silver-BaCe0.5Zr0.3Y0.16Zn0.04O3−δ composites for hydrogen separation membranes

“…A major challenge in this approach is the high content of the metal needed (>30 vol%) [5,17] to achieve percolation in the electronically conductive phase. Most composites used for oxygen separation therefore contain high levels of the electronically conductive phase [18].…”

Simulation of Limestone Calcination for Calcium Looping: Potential for Autothermal and Hydrogen-Producing Sorbent Regeneration

“…Palladium-based membranes have been studied by many authors for in situ hydrogen separation in membrane-assisted reformers. ,,− These membranes have relatively high permeability, together with nearly infinite hydrogen perm-selectivity, at moderate operating temperatures. , However, palladium can lose its hydrogen selectivity and mechanical stability at operating temperatures exceeding 550–620 °C. , Therefore, palladium-based membranes may be unsuitable for a MA-MRC-CAL unit, simply due to the high operating temperatures required for such a process. Numerous studies have been conducted to fabricate and test alternative membrane materials which could operate properly at high operating temperatures (e.g., for gasification and DMR) including nickel, cermet/cement, and Group Vb metals. ,− Supporting Information (Table S.1) compares these membrane materials for high-temperature hydrogen separation applications. Among these alternatives, nickel is a promising membrane material with moderate hydrogen permeability and selectivity (e.g., 10 times less permeability compared to palladium, and hydrogen selectivity of 500 at 800 °C), together with being commercially available in various sizes and at much lower price .…”

“…Palladium-based membranes are the most commonly used materials for the removal of hydrogen from reformer gaseous mixtures. − However, palladium loses its hydrogen selectivity and mechanical stability at operating temperatures exceeding 550–620 °C. , In addition, these membranes are highly sensitive to poisoning when contacting species such as CO and sulfur compounds . Alternative hydrogen-selective materials, including nickel, cermet/cement, and Group Vb metals, have been also studied for high-temperature hydrogen separation purposes. ,− However, these materials normally suffer from low hydrogen permeability, low hydrogen selectivity, unfavorable reactivity (with other syngas species), or low mechanical stability …”