Palladium alloy membranes performance

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. 

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. 

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... 

Hatlevik, S. K. Gade, M. K. Keeling, P. M. Thoen, A. P. Davidson and J. D. Way, Palladium and palladium alloy membranes for hydrogen separation and production History, fabrication strategies, and current performance, Sep. Purif. TechnoL, 2010, 73, 59-64. 

Damle, A.S., C. Richardson, C. Love, T. Powers, and J. Aquaviva, High performance palladium-alloy based composite membranes for hydrogen production, 2007 NHA Annual Meeting, San Antonio, TX, March 2007. 

Cheng Y.S. Performance of alumina, zeolite, palladium, Pd-Ag alloy membranes for hydrogen separation from Towngas mixture. J.Membr.Sci 2002 204 329-340. 

Howard BH, Killmeyer RP, Rothenberger KS, Cugini AV, Morreale BD, Enick RM, and Bustamante F. Hydrogen performance of palladium-copper alloy membranes over a wide range of temperatures and pressures. J. Membr. Sci. 2004 241 207-218. 

The Effect of Continuous H2S Exposure on the Performance of Thick Palladium-Copper Alloy Membranes... 

Complex substrate modifications involving intermediate layers and palladium alloy deposition methods are often required for superior membrane performance. Modification of a membrane support surface before palladium deposition by sintering on smaller particles can create a smoother surface with smaller pores, facilitating the deposition of a defect-free palladium layer. Nickel microparticles have been sintered together to form a porous support that was sputter-coated with palladium and then copper [118]. Thermal treatment at 700 °C for 1 h promoted reflow to create a durable, pinhole-free membrane with a Pd-Cu-Ni alloy film. In another case, starting with commercially available PSS with a 0.5 pm particle filtration cut-ofF, submicron nickel particles were dispersed on the surface, vacnium sintered for 5 h at 800 °C, and then sputtered with UN [159]. The nickel particles created a smoother surface with smaller pores, so a thinner palladium alloy layer... 

To ensure high permeabilities, it is important to work with low membrane thickness without compromising membrane integrity. For this purpose, several techniques for the production of composite membranes, in which thin palladium alloy layers are deposited onto porous supports have been developed (Fig. 9.8) and are summarized by Drioli et al. [11]. The main problems related to composite membranes concern the achievement of defect-free deposited layers which maintain performance both with time, and also with thermal cycling. Usually, the dif-... 

Membrane reactors (MRs) for fuel processing combine the unit operation of membrane separation with catalytic reactions such as reforming and WGS. The membrane separation process is usually performed by hydrogen removal from the reformate by application of membranes made of ceramics or palladium and palladium alloys, while polymeric membranes are less convenient for systems of smaller than industrial scale, because several separation steps are required owing to their relatively low selectivity of the separation process. In MRs the equilibrium... 

It was not equally obvious that dense ceramic hydrogen-permeable membranes would be of similar interest. There are clearly needs for hydrogen purification membranes, but polymers and microporous materials as well as metals such as palladium and its alloys appeared to fill these needs. In addition, possible candidates for dense ceramic hydrogen-permeable materials were not as appealing as the oxygen-permeable ones in terms of performance and stability. 

However, the cost of these membranes is relatively high, which is the problem that could severely affect their massive development and commercial/industrial applications. Therefore, research is very active in its attempts to make high performance membranes, which could make up for their high fixed costs, and reduce the palladium content, with a consequent decrease of the material cost. The use of Pd-alloys not only allows a decrease of the palladium content in the membrane, but also provides some advantages in performances and/or mechanical resistances. 

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