Nickel–Cobalt on Carbonaceous Supports for the Selective Catalytic Hydrogenation of Cinnamaldehyde

The catalytic hydrogenation of α,β-unsaturated carbonyl compounds can lead to several different products, of which the unsaturated alcohol (en-ol) is most difficult to obtain. In this regard, cobalt is known to have a positive influence on platinum catalysts. Little is known about such an effect on more cost-effective nickel catalysts. Nickel and cobalt (5 mass % each) were supported on graphite (GRA), multiwalled carbon nanotubes (MWCNT), and activated carbon (AC). The catalysts were characterized by N2-physisorption, X-ray diffraction (XRD), H2-chemisorption, and high-resolution transmission electron microscopy. XRD indicated the formation of a Ni–Co alloy. For cinnamaldehyde as the substrate, the en-ol selectivity and the turnover frequency (TOF) of the catalysts increased in the order GRA < AC < MWCNT. Ni–Co/MWCNT showed the highest selectivity over the whole conversion range, and at a conversion of 63% (TOF: 14.4 h–1) the product contained 62% en-ol and 38% saturated aldehyde. A positive influence of both cobalt and the support (MWCNT) on the selectivity of nickel catalysts is clearly indicated.