| Summary: | Catalytic membrane reactors (CMR) based on H-separation membranes can improve the performance of thermodynamically-limited reactions such as high-pressure steam methane reforming, ammonia cracking, non-oxidative aromatics production, and water gas shift reaction (WGS). In these industrial processes, the membrane surfaces are typically exposed to steam, CO, CO, HS, and hydrocarbons in combination with high temperatures. Therefore, the membrane materials require long-term thermo-chemical stability under the mentioned conditions. Stability in HS is of outstanding importance since its presence, even at ppm level, gives rise to substantial surface poisoning and decomposition of most materials. Here we characterize the influence of HS on the crystalline structure, lattice composition, and hydrogen-transport properties of LaWO, one of the reference protonic membrane materials. The incorporation of sulfide ions in the crystal lattice is ascertained from XRD, XPS, FESEM, WDS, EDS, and FIB-SIMS analyses. UV-vis spectroscopy and EIS measurements illustrate the effect of the incorporated sulfur in the transport properties, i.e., vigorously promoting the electronic conductivity mediated by the concurrent partial reduction of tungsten cations (W). The rise in electronic conductivity allowed an H flux of 0.042 mL cm min to be reached at 700 °C for a ∼700 μm-thick membrane, in contrast with negligible H permeation in HS-free conditions.
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