Influence of Pt Addition On the Performance of Pd-Au Hydrogen Separation Membranes

Tuesday, October 18, 2011: 4:13 PM
200 D (Minneapolis Convention Center)
Kent Coulter1, Sabina Gade2, Saurabh Chuadhari2, J. Douglas Way3, Sarah J. DeVoss4, Gökhan O. Alptekin4, Stephen N. Paglieri4, William Pledger5, David S. Sholl6 and Lymarie Semidey-Flecha7, (1)Surface Engineering & Materials Chemistry, Southwest Research Institute, San Antonio, TX, (2)Chemical Engineering, Colorado School of Mines, Golden, CO, (3)Colorado School of Mines, Golden, CO, (4)TDA Research, Inc., Wheat Ridge, CO, (5)IdaTech, LLC, Bend, OR, (6)School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, (7)Georgia Institute of Technology, Atlanta, GA

Palladium alloys have been extensively studied as hydrogen separation membranes with the permeability directly proportional to both solubility and diffusion.  Using Density Functional Theory (DFT), we have calculated that the addition of Au improves solubility of H over pure Pd but the addition of Pt has almost no effect.  Unlike in the solubility analysis, DFT calculated that the addition of Au and Pt negatively effects diffusion of H in binary systems.   Given these modeled results, experiments were performed using binary Pd-Au and ternary Pd-Au-Pt alloys.  In pure H2, a Pd-Au alloy exhibited higher permeabilities than pure Pd, which is in agreement with published values for membranes of similar compositions. The addition of Pt in concentrations ranging from 4.3 to 12.9 wt% lowered the permeability in pure hydrogen to slightly below pure Pd. For thicker (25 µm) Pd-Au-Pt membranes pretreated in air (versus nitrogen) at 400°C before exposure to H2, an increase in permeability of 10-20% was observed. The hydrogen permeability, was depressed both by water-gas shift mixtures (with or without H2S), but it appears that either substantial quantities (20 wt%) of Au or the presence of Pt in the Pd alloy (or both) inhibit sulfide formation, thereby improving both permeability and stability in WGS conditions with H2S.   In this presentation, the predicted performance of the addition of Pt will be compared with experimentally measured values and a discussion of the influence of Au and Pt on the sulfur tolerance of the membranes will be presented.

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See more of this Session: Membranes for Hydrogen Purification
See more of this Group/Topical: Separations Division