Palladium, permeability

The first step in the application of nonporous metal membranes was made by T. Graham [15], who discovered palladium permeability for hydrogen only. He mentioned that... 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Palladium Diffusion. Palladium is very permeable to hydrogen but not permeable to other gases. As a result, it is a useful hydrogen purifier. A palladium membrane, heated to 400 °C, purifies hydrogen to <10 ppb but requires a high pressure differential for net diffusion to take place at reasonable rates of hydrogen supply. 

Gryaznov, V.M., Hydrogen permeable palladium membrane catalysts, an aid to the efficient production of ultra purechemicals and pharmaceuticals, Plat. Met. Rev., 30,68-72,1986. 

Gryaznov, V.M., M.M. Ermilova, L.S. Morozova, and N.V. Orekhova, Palladium alloys as hydrogen permeable catalysts in hydrogenation and dehydrogenation reactions, ]. Less-Common Metals, 89,529-535,1983. 

Knapton, A.G., Palladium alloys for hydrogen diffusion membranes—A review of high permeability materials, Plat. Met. Rev., 21,44-50,1977. 

Uemiya, S., T. Matsuda, and E. Kikuchi, Hydrogen permeable palladium-silver alloy membrane supported on porous ceramics, /. Membr. Sci., 56, 315,1991b. 

New approaches to catalyst recovery and reuse have considered the use of membrane systems permeable to reactants and products but not to catalysts (370). In an attempt to overcome the problem of inaccessibility of certain catalytic sites in supported polymers, some soluble rho-dium(I), platinum(II), and palladium(II) complexes with noncross-linked phosphinated polystyrene have been used for olefin hydrogenation. The catalysts were quantitatively recovered by membrane filtration or by precipitation with hexane, but they were no more active than supported... 

Membrane processes are based on the selective transmission characteristics of the membrane material for different molecules, whereby the most effective membranes are usually also the most expensive. For example, the purest hydrogen can be captured by palladium membranes with suitable additives, but their low permeability make it necessary to use large membrane surfaces and high pressures, which result in high costs. 

Mishchenko, A. P., M. E. Sarylova, V. M. Gryaznov, V. S. Smirnov, N. R. Roshan, V. P. Polyakova and E. M. Savitskii. 1977. Hydrogen permeability and catalytic activity of membranes made of palladium-copper alloys in relation to the dehydrogenation of 1,2-cyclohexanediol. Izv. Akad. Nauk SSSR, Ser. Khim. 7 1620-1622. 

Mishchenko, A. P. and M. E. Sarylova. 1981. Hydrogen permeability and catalytic activity of a membrane catalyst from a palladium alloy containing 6% ruthenium in relation to hydrogenation of 1,3-pcntadicnc. Met. i Splavy Membrane Kak. Katalyz. M. 75-81. 

Metal-based PRBs involve the introduction of metals, usually zero-valent iron, but sometimes metal wool, palladium, or other metals to chemically react with the target contaminant(s), causing chemical adsorption with and/or destruction of the contaminants. These materials are typically permeable to water and thus avoid the groundwater management and flow problems associated with impermeable barriers. 

Abstract Pressure-sensitive paint (PSP) is applied to the areodynamics measurement. PSP is optical sensor based on the luminescence of dye probe molecules quenching by oxygen gas. Many PSPs are composed of probe dye molecules, such as polycyclic aromatic hydrocarbons (pyrene, pyrene derivative etc.), transition metal complexes (ruthenium(II), osumium(II), iridium(III) etc.), and metalloporphyrins (platinum (II), palladium(II), etc.) immobilized in oxygen permeable polymer (silicone, polystyrene, fluorinated polymer, cellulose derivative, etc.) film. Dye probe molecules adsorbed layer based PSPs such as pyrene derivative and porphyrins directly adsorbed onto anodic oxidised aluminium plat substrate also developed. In this section the properties of various oxygen permeable polymer for matrix and various dye probes for PSP are described. 

PtOEP is widely used as a PSP probe among the metalloporphyrins. The absorption and emission maximum of PtOEP are 381 and 535, and 646 nm, respectively. For examples of PSPs based on the OEP metal complexes in silicone polymer films, PSPs based on the platinum or palladium OEP immobilized in poly(TMSP) film have been reported. Oxygen permeability of poly(l-trimethylsily-l-propyne) (poly(TMSP)) film is about ten times larger than that of poly(dimethylsiloxane) (poly(DMS)) film, and provides a tough and thin film [14,15]. The poly(TMSP) film is a porous polymer matrix with a high oxygen permeability and diffusion, indicating that the probe... 

Kurungot et al. [48] developed a novel membrane material and a catalytic membrane reactor for the partial oxidation of methane. The driver of the development was the fact that rates of reforming reactions are much higher compared with the low permeability of conventional palladium membranes [49], Silica was previously recognized as a low-cost alternative to palladium [50], Additionally, the conventional... 

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