Exploring the Processing of Tubular Chromite- and Zirconia-Based Oxygen Transport Membranes

Abstract

Tubular oxygen transport membranes (OTMs) that can be directly integrated in high temperature processes have a large potential to reduce CO 2 emissions. However , the challenging processing of these multilayered tubes, combined with strict material stability requirements, has so far hindered such a direct integration. We have investigated if a porous support based on (Y 2 O 3 ) 0.03 (ZrO 2 ) 0.97 (3YSZ) with a dense composite oxygen membrane consisting of (Y 2 O 3 ) 0.01 (Sc 2 O 3 ) 0.10 (ZrO 2 ) 0.89 (10Sc1YSZ) as an ionic conductor and LaCr 0.85 Cu 0.10 Ni 0.05 O 3−δ (LCCN) as an electronic conductor could be fabricated as a tubular component, since these materials would provide outstanding chemical and mechanical stability. Tubular components were made by extrusion, dip coating, and co-sintering, and their chemical and mechanical integrity was evaluated. Sufficient gas permeability (≥10 −14 m 2 ) and mechanical strength (≥50 MPa) were achieved with extruded 3YSZ porous support tubes. The high co-sintering temperature required to densify the 10ScYSZ/LCCN membrane on the porous support, however, causes challenges related to the evaporation of chromium from the membrane. This chemical degradation caused loss of the LCCN electronic conducting phase and the formation of secondary lanthanum zirconate compounds and fractures. LCCN is therefore not suitable as the electronic conductor in a tubular OTM, unless means to lower the sintering temperature and reduce the chromium evaporation are found that are applicable to the large-scale fabrication of tubular components.

A review on dual-phase oxygen transport membranes: from fundamentals to commercial deployment

“…165 Other work on the production and testing of tubular dual-phase membranes considered formulations such as CeO 2 -La 0. 267 The most advanced developments to date in the eld of tubular OTMs are related to the R&D activities of Praxair, Inc. and are described in detail in Chapter 6.…”

“…Thermoplastic extrusion allows the fabrication of tubes with wall thickness below 1 mm, where a mixture of ne, sinterable powders with molten polymers (a feedstock) is forced through a hot auger and die to shape continuous components of a xed cross-sectional area by the fast cooling of the thermoplastic feedstock immediately aer exiting the die. The obtained tube requires the removal of the thermoplastic binder system via thermal debinding, 262,267 solvent extraction or catalytic methods before densication during sintering. 328 4.2.2.2.3 Compositional and microstructural design of extrusion for tubular OTM supports.…”

“…By replacing MgO with 3YSZ as a structural support material in this thermoplastic feedstock system, Haugen et al could increase the mechanical strength of the membrane tubes signicantly and reached gas permeability values of 10 À14 m 2 . 267 The permeabilities of these extruded support tubes are still signicantly lower than those for tubular structures with micron-sized, directional pores produced by a freeze casting technique, 333 see the next section on slip casting.…”

“…Haugen et al 267 have reported the fabrication of asymmetric membranes composed of different materials. The dip coating of a porous (Y 2 O 3 ) 0.03 (ZrO 2 ) 0.97 (3YSZ) tube with a porous 10Sc1YSZ activation layer and a thin composite oxygen membrane layer of LCCN-10Sc1YSZ led to severe challenges with the subsequent co-sintering.…”

Textured multilayered piezoelectric structures for energy conversion

“…The flowing air is especially crucial since the samples had to be kept between alumina plates to stay flat. Differences in sintering shrinkage is also a potential cause of bending and delaminations during sintering [44], which is observed to some extent by the slight curvature of the multilayers (direction of bending agrees with a higher shrinkage of the porous layer versus the dense, figure 3). The overall shape of the tapes' dilatometry curves resemble that of powder of the same composition [40], but the differences in the magnitude of shrinkage is related to the softness and compressibility at low temperature, and extra shrinkage related to the use of pore formers [21].…”