Palladium alloy membranes production

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... 

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. 

Un-supported Palladium Alloy Membranes for the Production of Hydrogen... 

The data presented in Fig. 5.6 were derived from membrane modules using Pd- Cu foil (planar) membranes with the membrane area sized to deliver 0.78 Nm h i of product hydrogen. Even though palladium alloy membranes are often criticized as being too expensive for commercial applications due to the cost of palladium, it is clear that as membrane thickness is reduced to 10 pm and less, the cost associated with the value of palladium in the membrane can be very reasonable. 

Membrane failure modes have been discussed above, and the connection to module design has also been discussed. Poor design for cyclic durability will be measured by the customer - the operating costs will be adversely affected by the requirement to replace membranes prematurely. Although the cost of membrane replacement should be offset by a recycle credit, the cost of materials and labor, and potential lost productivity, is stQl likely to be significant. The credit for recy-cUng palladium alloy membranes may be as great as 95% of the market value of the palladium (for foil membranes, perhaps only 85% of the market value if the palladium alloy is deposited onto a porous substrate). Environmentally, recycle also offers benefits versus recovery and purification of palladium from ore. 

Conventional production of vitamin K consists of four steps hydrogenation of 2-methylnaphthoquinone-l,4 to 2-methylnaphthohydroquinone-l,4 in a solvent in the presence of Raney nickel separation of the product from the catalyst by filtration evaporation of the solvent and boiling with acetic anhydride. Because the anhydride is highly corrosive, it tends to attack the nickel, and hence complete separation of the catalyst is necessary. On the other hand, use of a palladium alloy membrane reactor eliminates corrosion and makes it possible to complete the whole process in a single step (Gryaznov et al., 1986). The overall reaction 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. 

In parallel with the development of the membrane reformer system, a new concept membrane module, which has a palladium alloy membrane coated on the porous support tube with catalytic activity has been developed (Nishii, 2009). This membrane module is expected to provide a more compact reactor because the reactor does not require a separate catalyst. It is also expected that this module can be manufactured at low cost by applying the industrially-established mass production process used to make oxygen sensors for combustion control in vehicles with internal combustion engines. 

Lanning B., Arps J. (2005), Cost-effective method for producing self-supported palladium alloy membranes for use in efficient production of coal derived hydrogen , Quaterly Techn. Prog. Report, DOE. 

Lanning BR, Ishteiwy O, Way JD, Edlxmd DJ, Coulter KE. Un-supported palladium alloy membranes for the production of hydrogen. In Bose AC, editor. Inorganic membranes for energy and environmental applications. New York Springer Science+Business Media, LLC 2009. p. 203-20. 

Dense palladium-alloy membranes are generally used for the production of ultrapure hydrogen, although their high cost prevents their widespread use. However, their properties, such as infinite selectivity to hydrogen, chemical and thermal resistance, allow the use of the Pd-based membranes in MRs. Theoretical studies on the adsorption of gases on palladium-alloy surfaces... 

Selective gas permeation has been known for generations, and the early use of palladium silver-alloy membranes achieved sporadic industrial use. Gas separation on a massive scale was used to separate U from U using porous (Knudsen flow) membranes. An upgrade of the membranes at Oak Ridge cost 1.5 billion. Polymeric membranes became economically viable about 1980, introducing the modern era of gas-separation membranes. H2 recovery was the first major application, followed quickly by acid gas separation (CO2/CH4) and the production of N2 from air. 

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. 

As mentioned earlier, two compatible reactions may be coupled or conjugated properly by a shared membrane through which the species (as a product on one side of the membrane and a reactant on the other) common to both reactions selectively passes. Summarized in Table 8.5 are some documented studies of reaction coupling using dense palladium-based membranes with the alloying component ranging from nickel, ruthenium, rhodium to silver. 

Metal- and alloy-containing membranes are currently applied mainly in ultrapure hydrogen production. Pilot plants with palladium alloy tubular membrane catalyst were used in Moscow for hydrogenation of acetylenic alcohols into ethylenic ones. In the Topchiev Institute of Petrochemical Synthesis, a laboratory-scale reactor of the same type was tested... 

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-... 

Roa F, Way D, Paglieri SN. Process for preparing palladium alloy composition membranes for use in hydrogen separation, palladium alloy composite membranes and products incorporation or made from the membranes. United States Patent 8119205 2012. 

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