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

The present work is fo cused on the investigation of the performance and long-term stability of two composite palladium membranes under different operating conditions. One membrane (Pd/porous stainless steel (PSS)) is characterized by a similar to 10 mu m-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 similar to 7 aem-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 degrees C and 200-800 kPa, respectively. The H-2 permeances and the H-2/N-2 selectivities of both membranes were investigated and compared with literature data. At 400 degrees C and 200 kPa as pressure difference, Pd/PSS and Pd/Al2O3 membranes exhibited an H-2/N-2 ideal selectivity equal to 11700 and 6200, respectively, showing stability for 600 h. Thereafter, H-2/N-2 selectivity of both membranes progressively decreased and after around 2000 h, dropped dramatically to 55 and 310 for the Pd/PSS and