Bret H Howard

Learn More
Metal membranes play a vital role in hydrogen purification. Defect-free membranes can exhibit effectively infinite selectivity but must also provide high fluxes, resistance to poisoning, long operational lifetimes, and low cost. Alloying offers one route to improve on membranes based on pure metals such as palladium. We show how ab initio calculations and(More)
The high-pressure (100-2500 kPa) hydrogen permeance of two membranes, each composed of a thin palladium film (~22 μm) deposited on the oxidized surface of a porous stainless steel tubular substrate (0.2 μm grade support) has been determined over the 623 – 723 K temperature range. The hydrogen flux was proportional to the H 2 partial pressure in the(More)
14 The hydrogen permeability of bulk tantalum and tantalum coated with thin films of palladium was measured at temperatures from 623 to 1173 K and hydrogen partial pressures from 0.1 to 2.6 MPa in a flowing gas system. Palladium coatings were deposited by both electroless plating (1–2 ␮m thick Pd layer) and cold plasma-discharge sputtering with two(More)
Keywords: Palladium–copper membrane Hydrogen sulfide Palladium sulfide Sulfur poisoning a b s t r a c t In pure H 2 gas, hydrogen fluxes through pure Pd and Pd 47 Cu 53 (mol%) foils at 350 • C are similar. In the presence of 1000 ppm H 2 S in H 2 , the hydrogen fluxes through both foils are substantially reduced, but with significantly different decay(More)
Palladium-copper alloys continue to be of interest for hydrogen membrane applications because of their high catalytic activity for hydrogen dissociation, high hydrogen permeability, robustness, and degradation resistance in the presence of sulfur-containing compounds. This sulfur tolerance makes these alloys attractive for membrane applications where sulfur(More)
Hydrogen membranes have been identified as a promising technology for extracting pure hydrogen from processes such as coal gasification, hydrocarbon steam-reforming or any hydrogen producing process. Novel palladium-copper (Pd-Cu) alloys continue to be of interest due their highly catalytic surface, high performance, suppression of the hydride-phase(More)
  • 1