Permeability, palladium-containing

Table I. Hydrogen permeability for Palladium containing materials.

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. 

High pressures can be assayed in their buildup phase by using a macroversion of such voids (Fig. 12.84). The apparatus (Minevski and Lin, 1998) shows an electrochemical cell in which the cathode is a cylinder of palladium (chosen for its large permeability coefficient for the throughput of H) that contains a void space into which H2 diffuses from the deposition of H on the surface of the cylinder. This space is connected to a pressure transducer, which works on the principle of a piezoresistor, i.e., it contains a substance that produces an electrical potential upon being compressed. The rise of pressure inside the void space is shown in Fig. 12.85. 

In the patent by Hill, an aUoy of titanium containing 13 wt%vanadium, 11 wt% chromium and 3 wt% aluminum was developed as a hydrogen transport membrane material [12]. In this alloy, the crystal structure of titanium, which is normally hexagonal below 1153 K (880 °C), is stabilized in its high-temperature body centered cubic allotropic form. The body centered cubic crystal lattice is preferred for hydrogen transport. This titanium alloy was found to have hydrogen permeability superior to that of pure palladium in the range 300-450 °C (573-723 K)... 

For the preferred composition of coatings of palladium-silver alloys, the patent of Hunter [36] is referenced by Makrides et al.. In the Hunter patent, maximum hydrogen permeability through membranes of Pd-Ag was obtained using a composition containing 27 wt% silver. 

In a more specialized approach, IL phases have been immobilized in membrane materials. Although the primary driver of this work was the use of these materials as electrochemical devices, they have also been investigated for catalytic applications [20]. Membrane materials composed of air-stable, room-temperature ILs and poly(vinylidene fluoride)-hexafluoropropene copolymers were prepared with the incorporation of the active catalyst species in the form of palladium on activated carbon. Optical imaging revealed that the prepared membranes contained a high dispersion of the palladium catalyst particles. Studies on the materials included evaluating their gas permeability and their catalytic activity for the hydrogenation reaction of propene. 

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