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论文类型：期刊论文

发表时间：2009-06-23

发表刊物：CHEMISTRY OF MATERIALS

收录刊物：SCIE、EI、Scopus

卷号：21

期号：12

页面范围：2360-2366

ISSN号：0897-4756

摘要：Pd nanoparticle/functionalized CNF composites were synthesized by a two-step chemical vapor deposition of Pd(allyl)(Cp) as precursor at atmospheric pressure. Online mass spectrometry was used to measure the gas fragments during the two-step CVD. The functionalized CNFs and the resulting composites were characterized by temperature-programmed desorption mass spectroscopy, inductively coupled plasma-optical emission spectroscopy, X-ray diffraction, and transmission electron microscopy. The catalytic hydrogenation of cyclooctene on the Pd/CNF nanocomposites was also investigated in a fixed-bed reactor at 40 C under atmospheric pressure. No palladium deposition was observed on the raw CNFs, as a result of the absence of anchoring sites. The functionalization of CNFs with HNO(3) solution resulted in the formation of surface oxygen groups. The Pd(allyl)(Cp) precursor could be dissociatively adsorbed on the surface of the CNF by the reaction between the ligands and the surface oxygen groups. Further reduction in H(2) formed the Pd/CNF nanocomposites. The palladium loading on the functionalized CNFs depends on the degree of functionalization of the CNFs and on the amount of precursor provided. TEM and XRD results showed that highly dispersed and evenly distributed Pd particles with diameters of 2-4 nm could be prepared by this two-step CVD method. The Pd/CNF nanocomposite catalysts exhibited high activity and stability in the catalytic hydrogenation of cyclooctene, which can be attributed to the special interaction between the palladium nanoparticles and the CNFs and to the mesoporous nature of the CNFs, which prevents mass transfer limitation. The two-step CVD route has great potential in the controlled synthesis of CNF-supported metal catalysts with high dispersion and uniform distribution.