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Performance and Long-Term Stability of Pd/PSS and Pd/Al2O3 Membranes for Hydrogen Separation

pubblicazioni - Articolo

Performance and Long-Term Stability of Pd/PSS and Pd/Al2O3 Membranes for Hydrogen Separation

Il lavoro confronta le performance e la stabilità a lungo termine di due membrane composite al palladio, una su supporto metallico, l’altra su supporto ceramico, in diverse condizioni operative di temperatura e pressione.

The present work is focused on the investigation of the performance andlong-term stability of two composite palladium membranes under different operating conditions. One membrane (Pd/porous stainless steel (PSS)) is characterized by a ~10-µm thick palladium layer on a porous stainless steel substrate, which is pretreated by means of surface modification and oxidation; the other membrane (Pd/Al2O3) is constituted by a ~7 µm-thick palladium layer on an asymmetric microporous Al2O3 substrate.

The operating temperature and pressure ranges, used for studying the performance of these two kinds of membranes, are 350–450 °C and 200–800 kPa, respectively. The H2 permeances and the H2/N2 selectivities of both membranes were investigated and compared with literature data.

At 400 °C and 200 kPa as pressure difference, Pd/PSS and Pd/Al2O3 membranes exhibited an H2/N2 ideal selectivity equal to 11,700 and 6200, respectively, showing stability for 600 h. Thereafter, H2/N2 selectivity of both membranes progressively decreased and after around 2000 h, dropped dramatically to 55 and 310 for the Pd/PSS and Pd/Al2O3 membranes, respectively. As evidenced by SEM-EDS analyses, the pinholes appear on the whole surface of the Pd/PSS membrane, and this is probably due to release of sulphur from the graphite seal rings.

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