Palladium membrane hydrogen permeability

The hydrogen membrane reactor was initially evaluated by measuring the performance of a pure palladium membrane. The permeability of pure palladium under various conditions has been well established and therefore can be used as a baseline test to verify if a new hydrogen membrane reactor is calibrated properly. At 440°C and under a simulated WGS feed stream, the pure palladium membrane exhibited a permeability of 2.0 x 10 mol m s Pa that is consistent with literature reports. 

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. 

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. 

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. 

Ceramic and semiconductor thin films have been prepared by a number of methods including chemical vapor deposition (CVD), spray-coating, and sol-gel techniques. In the present work, the sol-gel method was chosen to prepare uniform, thin films of titanium oxides on palladium Titanium oxide was chosen because of its versatility as a support material and also because the sol-gel synthesis of titania films has been clearly described by Takahashi and co-workers (22). The procedure utilized herein follows the work of Takahashi, but is modified to take advantage of the hydrogen permeability of the palladium substrate. Our objective was to develop a reliable procedure for the fabrication of thin titania films on palladium, and then to evaluate the performance of the resulting metalloceramic membranes for hydrogen transport and ethylene hydrogenation for comparison to the pure palladium membrane results. 

V.M. Gryaznov Hydrogen Permeable Palladium Membrane Catalysts , Platinum Metals Rev., 30 [2] 68-72 (1986). 

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). 

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 while using a minimal amount of hydrogen-permeable material. 

Measurement of palladium membrane permeability. The permeation rate of hydrogen gas through the palladium membrane, Q , was assumed to obey the half-power pressure law(20). The permeation flux of hydrogen through the membrane is proportional to the difference between the souare roots of the hydrogen partial pressure on the high and low pressure sides of membrane. 

The feasibility of the palladium membrane system with an oxidation reaction on the permeation side and 1-butene dehydrogenation reaction on the reaction side in a membrane reactor has been successfully demonstrated. The palladium and its alloy membrane not only can withstand high temperature but also are selectively permeable to hydrogen... 

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