Carbon nanotubes supported Pt catalysts for phenylacetylene hydrogenation: effects of oxygen containing surface groups on Pt dispersion and catalytic performance

Abstract

Carbon nanotubes with different surface groups were achieved by oxidative treatments with HNO3–H2SO4 and followed thermal treatments. Deposition of Pt particles onto carbon nanotubes was achieved through chemical reduction of H2PtCl6·6H2O by ethylene glycol in the presence of NaOH. The as-prepared samples were characterized by temperature programmed desorption, Fourier transform infrared spectroscopy, X-ray diffraction and high resolution transmission electron microscopy. The type and amount of surface oxygen functional groups on the carbon nanotubes can be regulated by thermal treatments at different temperatures in an inert atmosphere. Both dispersion and sintering resistance of Pt nanoparticles were found to be a function of amount of oxygen surface groups on the carbon nanotubes, however, the amount of oxygen surface groups apparently did not affect the Pt loading on the carbon nanotubes. The Pt nanoparticles supported on the functionalized carbon nanotubes by oxidation treatment gave superior catalytic activity for the phenylacetylene hydrogenation, which phenylacetylene conversion and selectivity to styrene are 99% and 88%, respectively. This may be due to the higher dispersion (i.e., smaller particle size) of the Pt nanoparticles, which is beneficial for the hydrogenation of phenylacetylene.