Characterization and catalytic properties of Ni–Sn intermetallic compounds in acetylene hydrogenation
Abstract
The surface and catalytic properties of Ni–Sn intermetallic compounds (IMCs), Ni3Sn, Ni3Sn2 and Ni3Sn2 and Ni3Sn4, were studied by X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR) and catalytic reactions, such as the hydrogenation of acetylene, H2–D2 equilibration and H–D exchange between C2D4 and H2. The XPS results clarified that nickel and tin atoms near the surface were reduced into Ni0 and Sn0 by the hydrogen treatment at 873 K. The surface of each Ni–Sn IMC had specific nickel compositions and Ni3d valence band spectra. The TPR results showed that each Ni–Sn IMC had a different peak temperature from pure nickel and each other. These results revealed that Ni–Sn IMCs had the genuine surface of each IMC phase. Ni3Sn and Ni3Sn2 catalysts showed the high selectivity for the partial hydrogenation of acetylene into ethylene and did not catalyze the ethane formation. The high selectivity of Ni–Sn IMCs resulted from the very low activity of Ni3Sn and inactivity of Ni3Sn2 for the ethylene hydrogenation. The H–D exchange between deuterized ethylene and hydrogen, however, proceeded even over Ni3Sn2. The cause of the low activity of Ni–Sn IMC for the ethylene hydrogenation was discussed in view of the reaction mechanism.