The role of metal-support interaction in catalytic activity of nanodiamond-supported nickel in selective phenylacetylene hydrogenation

Metal precursor coordination and its reduction mechanism in Ni catalysts supported on detonation nandiamonds (ND) have been studied. TPR demonstrated multistage reduction of NiO supported on ND, which was explained by the presence of two types of Ni species on the ND surface. Weakly bonded Ni species are held on the ND surface by van der Waals forces, whereas strongly bonded ones are chemically bonded to the functional groups on the ND surface. Both Ni-Ni and Ni-O-C scattering paths were found in Ni/ND catalysts using Morlet wavelet analysis of EXAFS data. The ratio of weakly and strongly bonded Ni species in the catalyst was tailored either by removal of functional groups by annealing of ND support in Ar at 900 degrees C or by calcination of NiO/ND precursor in air at 300 degrees C. The former resulted primarily in weakly bonded Ni species in the catalyst, while the latter led to strongly bonded ones. These two catalysts demonstrated drastic differences in selective styrene formation upon phenylacetylene hydrogenation: weakly bonded Ni species gave rise mainly to ethylbenzene, while Ni species strongly bonded to the surface through the Ni-O-C bond afforded mainly styrene. (C) 2016 Elsevier Inc. All rights reserved.