Indication of interaction of metals from TPR and XPS in relation with their reactivity for 1,3-butadiene hydrogenation

A series of nickel base catalysts supported on silica has been used for selective hydrogenation of 1,3-butadiene. The materials were characterized by means of temperature-programmed reduction, hydrogen chemisorption, x-ray photoelectron spectroscopy, and x-ray absorption near edge structure. Cu-Ni interaction affected the reduction behavior of the catalysts. TPR results reveal the presence of more reducible nickel species formed by interaction of nickel with the surface of copper oxide. These results are in agreement with XPS results of Ni 2p spectra showing significant shifts towards lower binding energies with increasing copper loading. XPS shows that the Ni-Cu alloy is formed with enrichment of Ni on the surface. The addition of copper on Ni/SiO2 causes the conversion rate to decrease and increases selectivity to 1-butene. This selectivity behavior is explained by the variation of the electronic properties of nickel induced by copper. Hydrogen chemisorption results show that the dilution of the nickel surface atoms is responsible for the decrease in activity.