| 1. |
- Amandusson, H., et al.
(author)
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Alcohol dehydrogenation over Pd versus PdAg membranes
- 2001
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In: Applied Catalysis A. - 0926-860X .- 1873-3875. ; 217:1-2, s. 157-164
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Journal article (peer-reviewed)abstract
- The dehydrogenation of methanol and ethanol and the subsequent permeation of hydrogen through Pd and Pd70Ag30 membranes, respectively, have been studied. In order to keep a continuous hydrogen permeation rate, oxygen needs to be added to the alcohol supply. Without oxygen, the decomposition products will form a contaminating layer on the upstream membrane surface. The extraction of hydrogen from ethanol is six times more effective through a Pd70Ag30 membrane than through a pure Pd membrane (at optimum conditions). For methanol, the hydrogen permeation is 30% larger through a Pd70Ag30 membrane than through a membrane of pure Pd. The increased hydrogen permeation yield through Pd70Ag30 compared to Pd can be attributed mainly to a lower upstream consumption of hydrogen due to water formation, but also to an increased conversion of the alcohol in the presence of oxygen. © 2001 Elsevier Science B.V.
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| 2. |
- Amandusson, H., et al.
(author)
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Effect of CO and O2 on hydrogen permeation through a palladium membrane
- 2000
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In: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 153:4, s. 259-267
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Journal article (peer-reviewed)abstract
- Hydrogen permeation through a 25-µm thick palladium membrane during continuous exposures of hydrogen together with different combinations of oxygen and carbon monoxide has been studied at membrane temperatures of 100 °C-250 °C (total pressures of 40-150 Torr). Both CO and O2, individually, inhibit hydrogen permeation through the membrane. The cause of the inhibition is, however, somewhat different. CO blocks available hydrogen dissociation sites, while oxygen both blocks dissociation sites and also consumes adsorbed hydrogen through the production of water. When a combination of CO and O2 is supplied together with hydrogen, new reaction pathways will emerge. The carbon dioxide formation will dominate the water forming reaction, and consequently, the blocking effect caused by the formation of water will be suppressed. In a mixture of CO+O2+H2, the hydrogen permeation can become either larger or smaller than that due to only O2+H2 or CO+H2 depending on the CO/O2 ratio. It is thus possible to find a situation where carbon monoxide and oxygen react to form CO2 leaving adsorbed hydrogen free to permeate the membrane.
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| 3. |
- Amandusson, H., et al.
(author)
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Hydrogen permeation through surface modified Pd and PdAg membranes
- 2001
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In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 193:1, s. 35-47
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Journal article (peer-reviewed)abstract
- The hydrogen permeation through surface modified Pd and Pd70Ag30 membranes has been studied at temperatures between 100 and 350°C. Silver has been evaporated on Pd and Pd70Ag30 foils with a thickness of 25µm in order to study the role of the surface composition in comparison with the membrane bulk composition. The Pd70Ag30-based membranes display the largest permeation rates at temperatures below 200°C, while Pd membranes with 20Å silver evaporated on the upstream side show the largest permeation rates above 200°C. There are, consequently, different rate limiting processes above and below 200°C: at temperatures below 200°C, the bulk diffusion through the membrane is rate limiting, while at temperatures above 200°C, the influence of the surface composition starts to become significant. It has further been concluded that a sharp silver concentration gradient from the surface to the bulk is important for the hydrogen permeation rate at temperatures above 200°C. Adding oxygen to the hydrogen supply will almost totally inhibit the hydrogen permeation rate when a pure Pd membrane surface is facing the upstream side, while for silver-containing surfaces the presence of oxygen has almost no effect. On a clean Pd surface, oxygen effectively consumes adsorbed hydrogen in a water forming reaction. With Ag on the surface, no water formation is detected. Co-supplied CO inhibits the permeation of hydrogen in a similar manner on all studied membrane surfaces, independent of surface silver content. © 2001 Elsevier Science B.V. All rights reserved.
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| 4. |
- Amandusson, H., et al.
(author)
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Isotopic study of ethanol dehydrogenation over a palladium membrane
- 2000
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In: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 195:2, s. 376-382
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Journal article (peer-reviewed)abstract
- The dehydrogenation of ethanol and the subsequent permeation were studied on a Pd membrane in a continuous ethanol supply. Hydrogen could not be extracted as efficiently from ethanol as from methanol. In ethanol, at least four of the six hydrogen atoms were not available for permeation because of methane formation. Hydrogens bonded to a carbon atom in a C-O group were available for permeation, while hydrogen atoms bonded to a carbon atom without oxygen were not. The efficiency of hydrogen permeation from ethanol was 5% compared to that of pure hydrogen, which could be compared to 25% for methanol compared to pure hydrogen. The hydrogen permeation could be enhanced by adding CO to the EtOH + O2 supply. The permeation probability of the hydrogen bonded to the methylene hydrogen increased while the water formation with this hydrogen atom decreased. Acetic acid was formed upstream when oxygen was in excess. The differently bonded hydrogen atoms in an ethanol molecule experienced different reaction pathways. The results did not contradict the models made from surface experiments in ultrahigh vacuum by Davis and Barteau, Holroyd and Bowker, or Bowker et al.
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| 5. |
- Gold, J, et al.
(author)
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Chemical characterization and reactivity of iron chelator-treated amphibole asbestos
- 1997
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In: ENVIRONMENTAL HEALTH PERSPECTIVES. - : US DEPT HEALTH HUMAN SERVICES PUBLIC HEALTH SERVICE. - 0091-6765. ; 105, s. 1021-1030
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Journal article (other academic/artistic)abstract
- Iron in amphibole asbestos is implicated in the pathogenicity of inhaled fibers. Evidence includes the observation that iron chelators can suppress fiber-induced tissue damage. This is believed to occur via the diminished production of fiber-associated re
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| 6. |
- Nielsen, A.T., et al.
(author)
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Hydrogen production from organic waste
- 2001
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In: International journal of hydrogen energy. - 0360-3199 .- 1879-3487. ; 26:6, s. 547-550
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Journal article (peer-reviewed)abstract
- The extraction of pure hydrogen from the fermentation of household waste by a mixed anaerobic bacterial flora is demonstrated. Simulated household waste (600 g) was fermented in a bioreactor, which was continuously sparged with nitrogen (30 ml/min) fed in from the bottom. The gas stream from the biorector passes through a sulphide trap (ZnO) and then through a heated palladium-silver membrane reactor to separate hydrogen from the gas stream. In this way, waste remediation and biological hydrogen production is combined in a process where a large proportion of the hydrogen produced can be collected, free of other gaseous species from the fermentation. © 2001 International Association for Hydrogen Energy.
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