PREPARATION AND CATALYSIS OVER PALLADIUM COMPOSITE MEMBRANES

Binary and ternary palladium alloys with manganese, cobalt, ruthenium, tin and lead were obtained in the form of continuous thin films on asymmetric polymer membranes, porous metal sheets and oxide plates. All of these compositions proved to be permeable for hydrogen only. Compositions on polyarilyde (polydiphenylenephtalide) were stable in air up to 473 K and did not swell in hydrocarbons. A metallised polyarilyde membrane had a hydrogen permeability of 13.8 m3/m2 h at 473 K and pressure drop of 1 MPa. Productivity and selectivity for pentadiene vapour phase hydrogenation to pentenes of these compositions are the same as for the palladium alloy foil but contained 180 times less palladium than the foil. The selectivity of palladium-ruthenium foil for ethene and propene synthesis by carbon monoxide hydrogenation increased drastically after coverage of this foil with islands of cobalt. Hydrogen permeability of a stainless steel porous sheet deposited with a 10 mum thick film of palladium-ruthenium alloy by magnetron sputtering decreased twofold after a 1000 h test at 1073 K. Introduction of a 0.8 mum thick intermediate layer of tungsten into this composition maintained its hydrogen permeability at high temperatures. Magnesia and zirconia intermediate layers were effective as well. A porous plate made of magnesia and 15% yttria covered with a 10 mum film of palladium alloy with 6% of ruthenium had a hydrogen permeability of 108 m3/m2 h (at 973 K and a pressure drop of 2 MPa) which was constant for 1000 h. Palladium-lead clusters implanted in the pores of a stainless steel sheet had 96% selectivity for the liquid phase hydrogenation of dehydrolinalool to linalool at 423 K with a productivity of 9 mol/m2 h. A membrane catalyst for acetone condensation to 2-methylpentanone-4 was prepared by introduction of active alumina particles into the porous surface of palladium alloy foil.