Selective Hydrogenation Catalyzed by Intermetallic Compounds

Catalytic properties of intermetallic compounds for hydrogenation reactions are reviewed focusing on the differences in selectivity compared with monometallic catalysts. Intermetallic compound catalysts were prepared to form single phase particles of the target compound to clarify the specific catalytic properties. Pt3Ti showed higher activity than Pt for H-2 activation and ethylene hydrogenation. Various intermetallic compounds were found to be more selective than monometallic catalysts for the partial hydrogenation of alkyne into alkene. RhBi showed regioselectivity for the terminal C=C hydrogenation of trans-1,4-hexadiene. Combination of Pd3Bi and RhSb gave trans-stilbene in the hydrogenation of diphenylacetylene through partial hydrogenation into cis-stilbene on Pd3Bi and subsequent isomerization on RhSb. RhPb2 exhibited higher activity and selectivity than Rh for the chemoselective hydrogenation of p-nitrostyrene into p-aminostyrene. The higher selectivity of intermetallic compounds than monometals is discussed based on their unique atom arrangement on the surface of intermetallic compounds originating from their regular crystal structures.