Nickel-Silicon Intermetallics with Enhanced Selectivity in Hydrogenation Reactions of Cinnamaldehyde and Phenylacetylene

Nickel-silicon intermetallics have been prepared by a direct silicification method using SiH4 as the silicon source. The prepared nickel-silicon intermetallics were characterized by X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, temperature-programmed desorption, X-ray photoelectron spectroscopy, and CO chemisorption measurements. The catalytic hydrogenation of cinnamaldehyde and phenylacetylene over the nickel-silicon intermetallics was investigated. Nickel-silicon intermetallics presented much higher selectivity to the intermediate product (hydrocinnamaldehyde) than monometallic nickel catalyst, which may be attributed to the repulsive force between the electronegative silicon atoms in the nickel-silicon intermetallics and oxygen atoms in the C=O bond of cinnamaldehyde. In addition, nickel-silicon intermetallics showed excellent selectivity for the hydrogenation of phenylacetylene to styrene (ca. 93%) due to the strong modification of the electronic structure derived from the interaction of nickel and silicon.