The study of carbon nanotubules produced by catalytic method

The presence of basic centers in some oxides has been recognized for a long time as being important in catalysis [1-4]. Usually both basic and acid sites exist simultaneously. The two centers may work independently or in a concerted way. For instance, in alcohol transformation, dehydration is favored on acidic sites and dehydrogenation on basic centers [3,5]. A large variety of materials are cited as having basic character. They include single-metal oxides (MgO, CaO, ZnO), supported alkali metals (Na/MgO, K/K2CO3), mixed-metal oxides (MgO-A12O3, ZnO-SiO2, MgO-TiO2), zeolites (X and Y saturated with alkaline cations of low electronegativity), hydrotalcite-type anionic clays, asbestoslike materials, carbon-supported basic catalysts, and basic organic resins. ∗ Present address: 16 rue Francois Gillet, 69003 Lyon, France.

Basic zeolites : Characterization and uses in adsorption and catalysis

The effects of molecular structure on the electronic structure and redox properties of a series of 22 systematically designed conjugated polyquinolines and polyanthrazolines are explored by cyclic voltammetry and spectroelectrochemistry on thin films. The measured electrochemical bandgap of the series of conjugated polymers was in the range 2.0−3.1 eV and found to be in good agreement with the optical bandgap. The oxidation and reduction potentials, ionization potential, and electron affinity of the series of polymers were correlated with their main structural features. All the polyquinolines and polyanthrazolines had reversible reduction with formal potentials of −1.57 to −2.08 V (versus SCE) which make them excellent n-type semiconducting polymers. Polymers containing anthrazoline units have a higher electron affinity by 0.3−0.4 eV than those containing bis(quinoline) units. On the other hand, thiophene-linked polymers have a lower ionization potential by 0.45−0.5 eV than those with phenylene linkages. ...

Electrochemical Properties and Electronic Structures of Conjugated Polyquinolines and Polyanthrazolines

We summarize here the research advances on the reactivity of metal clusters. After a simple introduction of apparatuses used for gas-phase cluster reactions, we focus on the reactivity of metal clusters with various polar and nonpolar molecules in the gas phase and illustrate how elementary reactions of metal clusters proceed one-step at a time under a combination of geometric and electronic reorganization. The topics discussed in this study include chemical adsorption, addition reaction, cleavage of chemical bonds, etching effect, spin effect, the harpoon mechanism, and the complementary active sites (CAS) mechanism, among others. Insights into the reactivity of metal clusters not only facilitate a better understanding of the fundamentals in condensed-phase chemistry but also provide a way to dissect the stability and reactivity of monolayer-protected clusters synthesized via wet chemistry.

Reactivity of Metal Clusters.

This review addresses the most relevant aspects of vibrational spectroscopies (IR, Raman and INS) applied to zeolites and zeotype materials. Surface Bronsted and Lewis acidity and surface basicity are treated in detail. The role of probe molecules and the relevance of tuning both the proton affinity and the steric hindrance of the probe to fully understand and map the complex site population present inside microporous materials are critically discussed. A detailed description of the methods needed to precisely determine the IR absorption coefficients is given, making IR a quantitative technique. The thermodynamic parameters of the adsorption process that can be extracted from a variable-temperature IR study are described. Finally, cutting-edge space- and time-resolved experiments are reviewed. All aspects are discussed by reporting relevant examples. When available, the theoretical literature related to the reviewed experimental results is reported to support the interpretation of the vibrational spectra on an atomic level.

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Probing zeolites by vibrational spectroscopies

[Pt9(CO)18]2−/NaY (orange-brown, 2056 and 1798 cm−1), [Pt12(CO)24]2−/NaY (dark-green, 2080 and 1824 cm−1 and [Pt15(CO)30]2−/NaX (yellow-green, 2100 and 1865 cm−1) were stoichiometrically synthesized by the reductive carbonylation of [Pt(NH3)4]2+/NaY, Pt2+/NaY and Pt2+/NaX, respectively. The IR bands characteristic of their linear carbonyls shift to higher frequencies whereas the bridging CO bands to lower frequencies, compared with those on the external zeolites and in solution. In-situ FTIR studies suggested that the subcarbonyl species such as PtO(CO) and “Pt3(CO)3(μ2 −CO)3” are formed as the proposed intermediates towards [Pt12(CO)24]2−/NaY in the reductive carbonylation of Pt2+/NaY.13CO exchange reaction preceded with the different intrazeolite Pt carbonyl species in the following order of activity at 298–343 K: “Pt3(CO)3(μ2 –CO)3”/NaY ≫ PtO(CO)/NaY>[Pt9(CO)18]2−/NaY >[Pt12(CO)24]2−/NaY. Pt-L3-edge EXAFS measurment for these synthesized samples demonstrated that they are consistent with the Pt carbonyl clusters having trigonal prismatic Pt9 and Pt12 frameworks infered to a series of the Chini complexes such as [NEt4]2[Pt3(CO)6]
 n
 (
 n
 = 3–5). The intrazeolite Pt9 and Pt12 carbonyl clusters exhibited higher cataytic activity in NO reduction by CO towards N2 and N2O at 473 K, compared with those on the conventional Pt/Al2O3 catalysts. The mechanism of intrazeolite Pt9-Pt15 carbonyl cluster formation are discussed in terms of the intrazeolite basicity and acidity.

Ship-in-Bottle synthesis of Pt9-Pt15 carbonyl clusters inside NaY and NaX zeolites, in-situ FTIR and EXAFS characterization and the catalytic behaviors in13CO exchange reaction and NO reduction by CO

Transformation of platinum carbonyl clusters on graphite under laser irradiation and their scanning tunneling microscopy observation

Pt carbonyl clusters [Pt3(CO)6]n,2–(n= 3,4) in NaY zeolite pores are catalytically active for the water gas shift reaction (CO + H2O) at low temperatures, and exhibited effective photocatalysis for this reaction with a marked enhancement (ca. 38 times higher at 293 K) under illumination from a Xe lamp compared with the dark reaction.

Photocatalysis of metal clusters in cages: effective photoactivation of the water gas shift reaction catalysed on NaY zeolite-entrapped Pt12 and Pt9 carbonyl clusters

SiO2-grafted dinuclear molybdenum species derived from Mo2(OAc)4, e.g.[Mo[graphic omitted]Mo]V, which are characterized by ESR and EXAFS spectroscopy, exhibit marked catalytic activity for propene metathesis reaction, but are inactive for ethane homologation

SiO2-grafted dinuclear molybdenum catalyst derived from Mo2(OAc)4 ; highly active for alkene metathesis reaction

In ethylene hydroformylation over Pd/SiO2 catalysts with 17–85% Pd-dispersion, the turnover frequency for propionaldehyde formation increased with the Pd dispersion, particularly in the region of higher dispersion, suggesting the responsibility of atoms at the corners and at edges on the surface of Pd metal particles for this reaction.

Toshiyuki Fujimoto

Papers

Ship-in-Bottle synthesis of Pt9-Pt15 carbonyl clusters inside NaY and NaX zeolites, in-situ FTIR and EXAFS characterization and the catalytic behaviors in13CO exchange reaction and NO reduction by CO

Transformation of platinum carbonyl clusters on graphite under laser irradiation and their scanning tunneling microscopy observation

Photocatalysis of metal clusters in cages: effective photoactivation of the water gas shift reaction catalysed on NaY zeolite-entrapped Pt12 and Pt9 carbonyl clusters

SiO2-grafted dinuclear molybdenum catalyst derived from Mo2(OAc)4 ; highly active for alkene metathesis reaction

Effects of Pd Dispersion on the Catalytic Activity of Pd/SiO2 for Ethylene Hydroformylation.