The Kinetics of H2-D2 Exchange Over PdCu Surfaces

Thursday, November 11, 2010: 9:45 AM
Alta Room (Marriott Downtown)
Casey O'Brien1, James Miller1, Bryan Morreale1, Andrew Gellman1 and Petro Kondratyuk2, (1)USDOE National Energy Technology Department, Pittsburgh, PA, (2)Dept. of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA

Very high purity H2 can be produced from mixed gas streams, such as coal gasification syngas, by the use of dense Pd-based membranes which have the unique ability to dissociate molecular H2 and allow only atomic H to permeate through its bulk. To improve Pd's mechanical properties and its resistance to minor gas-phase components that can cause deterioration of membrane performance, such as H2S, Pd is often alloyed with other metals, including Cu.

In this work, we use the H2-D2 exchange reaction to probe the H2 dissociation activity of clean and sulfur-contaminated Pd, Cu and PdCu alloy surfaces. Over fixed beds of clean, diced Pd foils, the rate of H2-D2 exchange is limited by the desorption rate of product HD; over clean Cu, the reaction is limited by the relatively large barrier to dissociative adsorption. PdCu alloys display intermediate behaviors.

To provide a basis for understanding membrane performance in environments typical of the separation application, we also present kinetic analyses of H2-D2 exchange over Pd and PdCu surfaces in the presence of H2S. Our results contribute to the design basis for next generation purification devices.


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See more of this Session: Reactions and Separations for Hydrogen Production
See more of this Group/Topical: Topical 8: Hydrogen Production and Storage