A B S T R A C TA composite material consisting of carbon nanofibers (CNFs) grown on sintered metal fiber filters was modified by H 2 O 2 or plasma-generated O 3 . Coupling temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) techniques in the same UHV apparatus allowed the direct correlation of the nature of the created O-functional groups and their evolution as CO and CO 2 upon heating. The two oxidative treatments yielded different distributions of O-containing groups. The relative contribution of oxidized carbon was very low in the C1s region, hence the functional groups were more robustly analyzed through the O1s region. The comparison of the released oxygen by integration of the TPD CO, CO 2 and H 2 O spectra with the intensity loss of the XPS O1s spectra showed good agreement. In order to fit the data adequately, the set of O1s spectra was deconvoluted in at least four peaks for the differently activated samples. Finally, it was shown that functional groups formed by H 2 O 2 -treatment (mostly non-phenolic OH groups) are more thermally stable than those formed by O 3 -treatment. The latter treatment increases the concentration of carboxylic functionalities, which decompose at temperatures < 800 K;O 3 -activated CNFs should therefore show a more pronounced acidic behavior.

Monodispersed Pd nanoparticles (8, 11, and 13 nm in diameter) as confirmed by high resolution transmission electron microscopy were prepared via the reverse microemulsion method and deposited on structured supports consisting of carbon nanofibers (CNF) grown on sintered metal fibers (SMF). The CNF/SMF supports were subjected to oxidative treatments to introduce O-functional groups on the CNF surface. These groups were characterized by temperature-programmed decomposition (TPD) and X-ray photoelectron spectroscopy. The catalysts were used to study (a) the effect of Pd size and (b) the effect of the support nature on the selective acetylene hydrogenation. Antipathetic size dependence of TOF disappeared at particle size bigger than 11 nm. Initial selectivity to ethylene was found size-independent. The deactivation due to coke deposition was faster for smaller particles. The structure-sensitivity relations for the catalysts investigated are discussed in terms of "geometric" and "electronic nature" of the size effect and rationalized regarding Pd-C x phase formation which is size-dependent. Supports with increased acidity diminished the formation of coke and changed the byproduct distribution toward ethane.

Monodispersed Pd nanoparticles of 5 and 10 nm were obtained via reduction of Pd(acac) N], the monodispersed Pd nanoparticles were synthesized by simple heating in the absence of an additional reducing agent. The supported ionic liquid phase Pd nanoparticles on the structured CNF/SMF composites were tested for the selective hydrogenation of acetylene to ethylene and showed excellent long-term stability. The IL cation-anion network surrounding the nanoparticles suppressed the formation of active-site ensembles, known to catalyze the oligomerization of acetylene, responsible for the catalyst deactivation. The reaction rate was controlled by the internal diffusion of the reactants through the IL phase. The solubility of acetylene and ethylene in [bmim] [PF 6 ] was analyzed by NMR spectroscopy, which showed an order of magnitude difference. The lower solubility of ethylene compared to acetylene in the IL results in a high selectivity to ethylene, up to 85% at 150°C. The catalytic system also demonstrated high efficiency and long-term stability without any deactivation in ethylene-rich feed (2 vol % of acetylene, 40 vol % of ethylene, 10 vol % of H 2 in Ar), and therefore, the system shows promise for industrial application.

Structured supported ionic liquid-phase (SSILP) catalysis is a new concept with the advantages of ionic liquids (ILs) used as solvents for homogeneous catalyst and the further benefits of structured heterogeneous catalysts. This is achieved by confining the IL with the transition metal complex to the surface of a structured support consisting of sintered metal fibers (SMFs). In an attempt to improve the homogeneity of the IL film, the SMFs were coated by a layer of carbon nanofibers (CNFs). The IL thin film immobilized on CNF/SMF supports presents a high interface area, ensuring efficient use of the transition metal catalyst. The regular structure of the support with high porosity (>0.8) allows a low pressure drop and even gas-flow distribution in a fixed-bed reactor. The high thermoconductivity of the CNF/SMF support suppresses the formation of hot spots during exothermic hydrogenation reactions. The selective gas-phase hydrogenation of 1,3-cyclohexadiene to cyclohexene over a homogeneous Rh catalyst immobilized in IL supported on CNF/SMF was used as a test reaction to demonstrate the feasibility of the SSILP concept. The catalyst [Rh(H) 2 Cl(PPh 3 ) 3 /IL/CNF/SMF] showed a turnover frequency of 150-250 h −1 and a selectivity of >96%. High-pressure 1 H NMR and 1 H{ 31 P} NMR spectroscopy was used to provide insights into the nature of the active catalytic species.

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