Plasma Torch Generation of Carbon Supported Metal Catalysts

摘要

We recently completed a series of studies of supported (both carbon and alumina) metal catalysts, created using a novel approach. Catalytic materials were manufactured by passing an aerosol consisting of a mixture of metal salts, and conventional support materials through a plasma torch. We postulate that metal precursors ‘atomize’ as a result of high temperatures encountered in the plasma. The metal atoms then nucleate and grow on the surface of the support in the rapid cooling zone of the plasma afterglow. For this study plasma generated Pd and Pd-Ag catalysts supported on either alumina or Norit C carbons were tested. All the Pd catalysts were found to be active for the two test reactions, I) selective hydrogenation of 1-butene and ii) the selective hydrogenation of acetylene in an ethylene feed. Surprisingly, the Pd-Ag catalysts were only active for the latter. For the first reaction, the Pd/carbon activities were similar to catalysts generated by incipient wetness and the selectivity of all the plasma generated catalysts for this reaction was superior. Plasma generated carbon supported Pd-Ag catalysts (but not Pd only catalysts) were superior to commercial catalysts in terms of overall performance for the second test reaction. Studies of surface area indicate many of the activity changes can be explained in terms of simple, and predictable, physical changes in the catalyst material. For example, on carbon supports palladium particles of extreme dispersion, hence activity/gm, were formed. These results suggest that plasma generation of catalysts can be readily controlled to create catalysts with a wide range of characteristics.