Carbon Nanotubes Supported Mono- and Bimetallic Pt and Ru Catalysts for Selective Hydrogenation of Phenylacetylene

Deposition of Pt, Ru, Pt-Ru alloy, Ru@Pt, and Pt@Ru nanoparticles onto carbon nanotubes (CNTs) has been achieved by chemical reduction of the corresponding RuCl3 center dot 3H(2)O and/or H2PtCl6 center dot 6H(2)O by ethylene glycol in the presence of NaOH. The as-prepared catalysts were characterized by X-ray diffraction, H-2-temperature programmed reduction, H-2-temperature programmed desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Liquid-phase selective hydrogenation of phenylacetylene was used as a probe reaction to evaluate their catalytic performances. The as-prepared Pt, Ru, Pt-Ru alloy, Ru@Pt, and Pt@Ru nanoparticles fell in the range of 1.5-3.0 nm in diameter, and were uniformly dispersed on the CNTs. All the bimetallic catalysts displayed the characteristic diffraction peaks due to a Pt face-centered cubic structure, but the 2 theta values were shifted to slightly higher ones, indicating the formation of alloy or core shell structures. XPS analysis revealed that the catalysts contained mostly Pt(0) and Ru(0), with traces of Pt(II), Pt(IV), and Ru(IV). The Pt@Ru/CNTs and Ru@Pt/CNTs core-shell catalysts showed different catalytic properties in selective hydrogenation of phenylacetylene from the Pt Ru alloy and the mixed monometallic samples with the correspondingly identical composition.