Dense cermet membranes for hydrogen separation

• Published in: Separation and purification technology Vol. 121; pp. 54 - 59
• Main Authors: (Balu) Balachandran, U., Lee, T.H., Park, C.Y., Emerson, J.E., Picciolo, J.J., Dorris, S.E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-01-2014
• Subjects: Cermet; Cermets; Dense membrane; Flux; Hydrogen; Hydrogen flux; Hydrogen permeation; Hydrogen transport membrane; Membranes; Palladium; Phase boundaries; Separation; Hydrogen flux; Cermet; Hydrogen transport membrane; Dense membrane
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2013.10.001

•Cermet (ceramic–metal) membranes have been developed for hydrogen separation.•Flux is limited by the bulk diffusion of hydrogen through metal phase.•Long term stability for a period of 4months showed relatively stable flux.•Flux showed no degradation in synthesis gas mixture at high pressures (≈200 psig).•Membrane is stable in atmospheres containing up to 400ppm H2S and 80% H2.
Dense cermet (i.e., ceramic–metal composite) membranes have been developed for separating hydrogen from mixed gases, particularly product streams generated during coal gasification and/or steam methane reforming. Hydrogen separation with these membranes yields high-purity hydrogen, thereby eliminating the need for post-separation purification steps. Extensive tests have been conducted with cermet membranes made by mixing ≈50–60vol.% Pd with Y2O3-stabilized ZrO2. Using several feed gas mixtures, the hydrogen permeation rate, or flux, for the membranes was measured in the temperature range 400–900°C. With pure hydrogen at ambient pressure as feed gas, an ≈18-μm-thick membrane on a porous substrate gave a measured flux of ≈26cm3[STP]/min-cm2 at 400°C and ≈52cm3[STP]/min-cm2 at 900°C. We also measured the hydrogen flux through a thicker (≈150μm) membrane at 400°C using a mixture of H2, CO, CO2, H2O, and He at ≈200 psig as feed gas. Hydrogen flux measurements in H2S-containing atmospheres showed that the cermet membranes are stable at 900°C in gases that contain ≈80% H2/400ppm H2S. Because formation of palladium sulfide (Pd4S) can seriously degrade hydrogen permeation through Pd-containing cermet membranes, the Pd/Pd4S stability phase boundary of the cermet membrane was determined in the temperature range 450–650°C using various feed gases that contained 10–73% H2 and 8–400ppm H2S. Given these promising results, longer studies using real-world coal gasification conditions should be pursued.