Tantalum palladium coated

Buxbaum, R.E. and T.L. Marker, Hydrogen transport through non-porous membranes of palladium-coated niobium, tantalum and vanadium. /. Membr. Sci., 85, 29-38,1993. 

R.E. Buxbaum and T.L. Marker, Hydrogen Transport Through Non-porous Membranes of Palladium-coated Niobium, Tantalum, and Vanadium, 7. Membr. Sci. 85, 29 (1993). 

R.E. Buxbaum and A.B. Kinney, Hydrogen Transport Through Tubular Membranes of Palladium-coated Tantalum and Niobium, Ind. Eng. Chem. Res. 35, 530 (1996). 

Buxbaum R.E., Kinney A.V. Hydrogen transport through tubular membranes of palladium-coated tantalum and niobium. Ind.Eng.Chem.Res. 1996 35 530-537. 

The first commercial metal membranes for hydrogen separation and purification were made of palladium alloyed with 23-25 wt % silver. These membrane were of the unsupported type and tubular in shape. Nevertheless, the wall thickness was substantial by current standards—typically at least 100- an thick. Advances in drawing thin-walled metal tubes has allowed for palladium-silver tubular membranes to be made with much thinner walls, about 20- an thick. Composite membranes are also usually at least 25-/an thick. REB Research and Consulting (Oak Park, MI) provides tubular composite metal membranes consisting of a palladium coating over a tantalum base metal, although other group 4 or 5 base metals may be used. 

Buxbaum and the group at NETL have reported permeabilities for palladium coated tantalum of between 1.07 x 10 and 1.45 x 10 mol m i s Pa for temperatures 623-693 K (350-420 °C) [41]. Weekly backflushes with hydrogen to remove coke and other impurities were recommended [35]. Buxbaum and Marker have reported a permeability for Pd coated Nb of 3.2 x 10 mol m i s i Pa at 698 K (425 °C), which was only one-third of the theoretical value due to gas phase resistance [42]. The Buxbaum group has achieved a permeabihty for Zr of 2.2 X 10 mol m l s i Pa - at 698 K (425 °C) [42]. They state that hydrcgen transport through zirconium is 100 times better than through Pd under similar conditions [42]. 

Buxbaum RE, Marker TL. Hydrogen transport through nanoporous membranes of palladium-coated niobium, tantalum, and vanadium. J Membr Sci 1993 85 29-38. 

Some metals used as metallic coatings are considered nontoxic, such as aluminum, magnesium, iron, tin, indium, molybdenum, tungsten, titanium, tantalum, niobium, bismuth, and the precious metals such as gold, platinum, rhodium, and palladium. However, some of the most important poUutants are metallic contaminants of these metals. Metals that can be bioconcentrated to harmful levels, especially in predators at the top of the food chain, such as mercury, cadmium, and lead are especially problematic. Other metals such as silver, copper, nickel, zinc, and chromium in the hexavalent oxidation state are highly toxic to aquatic Hfe (37,57—60). 

Mukherjee et al. [96] used sputtered tantalum, as tantalum is reported [97] to be a cheap alternative with better permeation properties when coated with palladium compared with membranes made completely of palladium. 

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