Chemical stability in H2S and creep characterization of the mixed protonic conductor Nd5.5WO11.25-δ

Abstract

The integration of hydrogen permeable membranes in catalytic membrane reactors for thermodynamically limited reactions such as steam methane reforming can improve the per-pass yield and simultaneously produce a high-purity H2 stream. Mixed protonic-electronic materials based membranes are potential candidates for these applications due to their elevated temperature operation, good stability and potentially low cost. However, a specific mechanical behavior and stability under harsh atmospheres is needed to guarantee sufficient lifetime in real-world processes. This work presents the mechanical characterization and a study of the chemical stability under H2S containing atmospheres for the compound Nd5.5WO11.25-δ. Mechanical characterization was performed by micro-indentation and creep measurements in air. Chemical stability was evaluated by XRD and SEM and the effect of the H2S on the transport properties was evaluated by impedance spectroscopy. Under H2S atmospheres, the total conductivity increases at 600 °C and 700 °C. The conductivity increase is attributed to the incorporation of S 2ions in oxide-ion sublattice.

Lanthanum tungstate membranes for H2 extraction and CO2 utilization: Fabrication strategies based on sequential tape casting and plasma-spray physical vapor deposition

“…Hydrogen permeable ceramic membranes exhibit certain advantages over different types of membranes (Fig. 1) such as robustness, high thermal and hydrothermal stability (compared to polymers, Ag-Pd, SiO2, Carbon-SiO2 molecular sieves for CO2/H2 separation), as well as better chemical stability (no H2-induced embrittlement and sulfur poisoning particularly critical for Pd-based membranes, typically applicable up to 500 °C) [12][13][14][15]. Compared to the well-established Pd-Ag H2-permeable metallic membranes, the material costs of ceramics are lower.…”

Promotion of mixed protonic–electronic transport in La5.4WO11.1−δ membranes under H2S atmospheres

“…High-sulfur concentration areas are mainly located in the membrane surface and some occluded pores of the bulk, as previously observed for Nd 5.5 WO 11.25−d treated under similar conditions. 23 The surface-related areas with high-sulfur concentration exhibit low W concentrations, corresponding to the formation of La 2 O 2 S, as conrmed by the XRD analysis of the sample surface (Fig. S7 †).…”

Towards Upscaling of La5.5WO11.25−δ Manufacture for Plasma Spraying-Thin Film Coated Hydrogen Permeable Membranes

“…Lanthanide tungstates (Ln 6 WO 12 ) partly fulfil these requirements, i.e., (1) they present remarkable H 2 flows and infinite permselectivity [ 5 , 6 , 7 ], (2) the stability in CO 2 containing atmospheres and under H 2 S at ppm level [ 8 , 9 , 10 ] has been demonstrated and (3) the molecular formula presents some flexibility in the ratio Ln/W [ 11 , 12 ] which could favour the flexibility of the industrial production.…”