Palladium alloy membranes

Hopkins, S., High-Performance, Durable, Palladium-Alloy Membrane for Hydrogen Separation and Purification, Proceedings of 2007 U.S. DOE Hydrogen Annual Merit Review Meeting, Arlington, VA, May 2007. 

Gryaznov, V. M. 1986. Surface catalytic properties and hydrogen diffusion in palladium alloy membranes. Z. Phys. Chem. Neue Folge 147 761-70. 

The next step in the processor development will be to integrate the palladium alloy membrane with the methanol steam reformer reactor. The researchers anticipate that the addition of the palladium membrane will improve the reactor performance due to in-situ hydrogen removal. 

Ma, Y., Mardilovich, I.P. and Engwall, E.E. (2003) Thin composite palladium and palladium/alloy membranes for hydrogen separation. Annals of the New York Academy of Sciences, 984, 346—360. 

US Patent 6,183,542 was issued in 2001 for a palladium membrane process. This process provides an apparatus that can handle high flow rates of gas, per unit area of membrane, while using a minimal amount of hydrogen-permeable material. This is accomplished by using stainless steel mesh elements to reinforce the thin-walled, palladium or palladium alloy membranes. This process also provides the ability to withstand large pressure gradients in opposite directions and thus will make it easier to clean membranes that have been clogged with contaminants. 

H. Yoshida, S. Konishi and Y. Naruse, Effects of Impurities on Hydrogen Permeability through Palladium Alloy Membranes at Comparatively High Pressures and Temperatures , J. Less-Common Metals, 89 429-36 (1983). 

Shown in Table 8.6 arc some literature data on the use of dense membrane reactors for liquid- or multi-phase catalytic reactions. Compared to gas/vapor phase application studies, these investigations are relatively few in number. Most of them involve hydrogenation reactions of various chemicals such as acetylenic or ethylenic alcohols, acetone, butynediol, cyclohexane, dehydrolinalool, phenylacetylene and quinone. As expected, the majority of the materials adopted as membrane reactors are palladium alloy membranes. High selectivities or yields are observed in many cases. A higher conversion than that in a conventional reactor is found in a few cases. 

Hydrogen permeation flux data (pmoles/cm -min) of activated and non-activated palladium alloy membranes... 

Corrosive reaction streams. In some application environments, the reactive or corrosive nature of one or more of the reaction components in a membrane reactor can pose a great technical challenge to the selection as well as the design of the membrane element Feed streams often contain some Impurities that may significantly affect the performance of the membrane. Therefore, attention should also be paid to the response of the selected membrane material to certain impurities in the reactant or product streams. Care should be taken to pretreat the feed streams to remove the key contaminants as far as the membrane is concerned in these cases. For example, palladium alloy membranes can not withstand sulfur- or carbon-containing compounds at a temperature higher than, say, 500 C [Kamcyama et al., 1981]. Even at lOO C, the rate of hydrogen absorption (and, therefore, permeation) in a pure palladium disk is... 

Dense palladium and palladium alloy membranes have been repeatedly demonstrated to show extremely high sclcctiviiies of hydrogen and certain solid electrolyte membranes... 

Composite membrane catalysts can also be assembled with polymeric supports or intermediate layers [117-119]. These membranes were tested as membrane catalysts for selective hydrogenation of some dienic hydrocarbons and proved to be as selective as monolithic palladium alloy membranes [117]. The use of polyarilyde has been proposed in order to widen the temperature range of polymer-supported membrane application... 

The key problem of the cross-flow reactor is not how to construct an effective separation of the two flowing phases. It is instead connected with how to design the porosity and location of the catalytic active zones of the separating walls so that the transport resistance across the wall does not limit the conversion and the selectivity of the chemical reactions. Palladium-alloy membranes, or thin films of these alloys on porous ceramic tubs, seem to have the potential to be good solutions of the separating-wall problem for cross-flow reactors used for hydrogenation reactions. 

Gryaznov ct al. [30-32] have done pioneering work in the study of differently designed palladium-alloy membrane reactors for reactions in both gas phase and liquid phase. Most interest was directed to the composition and properties of the membranes, which were decisive questions at this stage of the development, and still are. Selectivity problems in various organic chemical reactions were also of importance to study. 

Yoshida, H., Konishi, S., and Naruse, Y., Effects of impurities on hydrogen permeability through palladium alloy membranes at comparatively high pressures and temperatures, J. Less-Comm. Met., 89, 429, 1983. 

Evans, J., Harris, I.R., and Ross, D.K., A proposed method of hydrogen isotope separation using palladium alloy membranes, J. Less-Comm. Met., 89, 407, 1983. 

Yoshida, H. et al., Preliminary design of fusion reactor fuel clean-up system hy the palladium alloy membrane method, Nucl. Technol./ Fusion, 3, 471, 1983. 

Hydrogen is able to permeate selectively through palladium or palladium alloy membranes. This has led to the demonstration of membrane reformers in the labora-... 

Despite these efforts, the cost of palladium-alloy membranes is still perceived by many to be prohibitive. However, even without a judicious reclamation and recycling program, the cost of palladium in current state-of-the-art, thin supported membranes is a small fraction of the total cost of the associated reformer and fuel cell system. With further development work from the private sector and government labs33 (supported by the Department of Energy), the prospect for volume commercial products is encouraging. 

Darling, A. S., Hydrogen separtaion by diffusion through palladium alloy membranes. Symposium on the less common means of separation. Institution of chemical engineers 1963. 

The use of a membrane reactor with a hydrogen-permeable palladium alloy membrane inside a catalyst-packed bed allowed a shifting of the chemical equilibrium to efficiently drive the dehydrogenation process at lower temperatures, e.g., waste heat. It thus serves as a chemical heat pump system. 

Juda W, Krueger CW, Bombard TR. Method of producing thin palladium-copper and the hke, palladium alloy membranes by solid-solid metallic interdifiusion, and improved membrane. US Patent 6238465,2001. 

---