Bret H. Howard

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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 H2 partial pressure in the retentate(More)
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 H2 partial pressure differences as great as 2.6 MPa. 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(More)
The kinetics of the high-temperature (1070-1134 K), low and high-pressure gasphase forward water-gas shift reaction were evaluated in an empty quartz reactor and a quartz reactor packed with quartz particles. The power law expression for the reaction rate was consistent with the Bradford mechanism and was invariant with respect to pressure. The experimental(More)
A sulfate-reducing bacterium has been isolated in pure culture from sheep rumen contents. Its properties agree in all respects tested with those ascribed to Desulfovibrio desulfuricans. The populations observed (about 10(8)/ml) are sufficient to account for published rates of ruminal sulfide production.
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-temperature rate of reaction of the homogeneous, reverse water-gas shift reaction, rWGSR, has been evaluated in quartz reactors with rapid feed pre-heating at low-pressure and high-pressure conditions. The form of the powerlaw rate expression was consistent with the Bradford mechanism. The Arrhenius expressions for the reaction rate constant(More)
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 different(More)
Introduction The Water Gas Shift Reaction (WGSR), an important industrial reaction for the production of chemicals and/or hydrogen, is expected to play a key role in the integration of gasification technologies with a H2 production/recovery unit. The effluent stream of the gasifier, mainly H2, CO and CO2 at high pressure (up to 30 atm) and temperature (up(More)
Approach • Complete reverse kinetics and Computational Fluid Dynamics (CFD) modeling to optimize reactor geometry for forward reactions • Measure forward kinetics in quartz & Inconel reactors to determine reactor wall catalysis • Measure forward kinetics in reactor packed with membrane material to determine catalytic activity • Measure membrane H2(More)