Hydrogenation catalysts prepared from amorphous alloys with zirconium

The hydrogenation of benzene and carbon dioxide was carried out over Zr-based catalysts prepared from amorphous alloys containing palladium, platinum, rhodium or nickel as the second metal. Although the hydrogenation activity of the alloys was very low in the virgin state, the activity gradually increased after oxidation and reduction in a hydrogen atmosphere. Characterization of the alloys revealed that the increase in surface area caused by oxidation of zirconium was responsible for the increase in hydrogenation activity. When the amorphous alloys were oxidized in an oxygen atmosphere, both the active metals for the hydrogenation and zirconium in the alloys were simultaneously oxidized. When the oxidized alloys were reduced in a hydrogen atmosphere, the oxides of the active metals were reduced to the respective metals, whereas zirconium remained in the oxide state. As a result, palladium, platinum, rhodium or nickel were highly dispersed on the produced zirconium oxide crystals. The principal advantage of a catalyst prepared from an amorphous alloy is the very high dispersion of active metal on the surface, despite the high metal content. It is considered that amorphous alloys containing zirconium as the second metal are attractive catalyst precursors for hydrogenation.