Journal of Membrane Science 241 (2004) 207–218 Hydrogen permeance of palladium–copper alloy membranes over a wide range of temperatures and pressures B.H. Howard a,∗ , R.P. Killmeyer a , K.S. Rothenberger a , A.V. Cugini a , B.D. Morreale b , R.M. Enick c , F. Bustamante c a United States Department of Energy, National Energy Technology Laboratory (NETL), P.O. Box 10940, Pittsburgh, PA 15236, USA b NETL Site Support Contractor, Parsons Project Services Inc., P.O. Box 618, South Park, PA 15129, USA c NETL Research Associate, University of Pittsburgh, Department of Chemical and Petroleum Engineering, Pittsburgh, PA 15261, USA Received 1 August 2003; received in revised form 2 April 2004; accepted 8 April 2004 Abstract The permeance of Pd–Cu alloys containing 40, 53, 60, and 80 wt.% Pd has been determined over the 623–1173 K temperature range for H 2 partial pressure differences as great as 2.6MPa. Pure palladium and copper membranes were also evaluated. The Pd–Cu alloys exhibited predictable permeances that reflected the crystalline phase structures as shown in the binary phase diagram. Under conditions of face-centered-cubic (fcc) stability, the permeance increased steadily with palladium content, approaching the permeance of pure palladium membranes. The 53 and 60 wt.% Pd alloys were evaluated at temperatures within the body-centered-cubic (bcc) stability region. For both alloys, the bcc permeance was several times greater than the fcc permeance with the 60 wt.% Pd bcc permeance at 623 K reaching about 70% of the permeance of palladium. These bcc alloys were subjected to temperature increases during testing that resulted in transition from bcc to fcc, followed by temperature decreases that should revert the alloys to bcc. The permeances dropped abruptly during the transition from bcc to fcc. However, on cooling back to the bcc stability region, neither the 60 nor 53 wt.% Pd alloy completely regained a bcc permeance during the test period. All of the Pd–Cu alloys subjected to testing at 1173 K showed some permeance decline that was attributed to intermetallic diffusion between the membrane and support. The application of a diffusion barrier between the support and membrane foil in a 53 wt.% Pd permeance test successfully blocked the intermetallic diffusion and prevented degredation of the membrane’s performance. © 2004 Elsevier B.V. All rights reserved. Keywords: Gas separations; Inorganic membranes; Metal membranes; Hydrogen; Palladium–copper 1. Introduction Hydrogen production is expected to increase in the future as the US moves toward widespread use of hydrogen as an energy carrier. Industrial processes, such as coal gasifica- tion, can be used for the production of hydrogen from do- mestic energy sources; however, hydrogen produced in this way is mixed with carbon dioxide and other gases requiring ancillary separation processes impacting the cost of hydro- gen production. Advances in membrane technology have the potential to improve the efficiency of hydrogen separation and recovery and reduce the cost associated with hydrogen production. ∗ Corresponding author. Tel.: +412 386 5908; fax: +412 386 5920. E-mail address: bret.howard@netl.doe.gov (B.H. Howard). Membrane poisoning by the contaminants typically found in gasifier effluent streams has been identified as a substan- tial scientific hurdle impeding the implementation of mem- brane technology in the generation of hydrogen via gasifica- tion. These contaminants include S, Cl and Hg compounds which are known poisons to palladium-based membranes [1–4]. Sulfur in the form of H 2 S is of special interest in the gasification of coal and other fossil fuels. Thus, the develop- ment of a robust, poison resistant and economical hydrogen membrane material is necessary for successful implementa- tion of advanced fossil energy plants. Recent studies have reported that palladium–copper alloy materials possess the high permeability [5–12] and resistance to sulfur poisoning needed to be considered as viable candidates for hydrogen separation within the coal gasification scheme [5,6,13,14]. The highest reported values of Pd–Cu alloy permeabil- ity were comparable to the permeability of pure palladium 0376-7388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2004.04.031