Abstract
The present work is focused 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 ~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 11700 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 Scanning Electron Microscope (SEM) 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.
Highlights
In recent years, the rise in the request for hydrogen in the petrochemical industries as well as for supplying fuel cells has led to ever increasing attention on the development of new and alternative methods for hydrogen separation/purification [1].In this context, dense palladium membranes have received growing consideration owing to their complete selectivity towards hydrogen permeation with respect to all other gases
Kulprathipanja et al [35] observed a significant decrease in the H2/N2 ideal selectivity, testing 4 μm Pd–Cu supported onto a porous alumina membrane after 340 h
Pd/porous stainless steel (PSS) and Pd/Al2O3, constituted by thin palladium layers deposited onto porous supports via electroless plating (ELP) have been studied in the temperature range of 350–450 °C and from 100 to 800 kPa as retentate pressure
Summary
The rise in the request for hydrogen in the petrochemical industries as well as for supplying fuel cells has led to ever increasing attention on the development of new and alternative methods for hydrogen separation/purification [1]. In this context, dense palladium membranes have received growing consideration owing to their complete selectivity towards hydrogen permeation with respect to all other gases. Stainless steel sintered porous supports are suitable owing to good weldability and mechanical strength They seem to be more convenient with respect to ceramic substrates for integration with
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