过渡金属同晶替换的铁氧化物及其在非均相Fenton反应中的应用

过渡金属同晶替换的铁氧化物因其具有稳定、高效和可重复利用等特点而被广泛应用于催化处理难降解有机物领域。本文综述了这种新型催化剂的制备过程、过渡金属的同晶替换对催化剂物理化学性质(如比表面积、表面羟基数量、铁离子溶出量及热稳定性)的影响以及促进非均相Fenton反应的催化机制(氧化还原电对结构及氧空位理论)。本文还探讨了这种新型铁氧化物在难降解有机物处理中的应用进展,为后续研究提供了新的思路。     

The synthesis and characterisation of immobilised palladium carbene complexes and their application to heterogeneous catalysis

Silica supported palladium NHC complexes have been prepared by two different routes: one involving the reaction of silica-supported imidazolium salts with palladium acetate and a direct immobilisation of a pre-formed complex by reacting a (trimethoxysilylpropyl)-N-aryl-imidazolylidene palladium complex with surface hydroxyl groups. A small range of catalysts of varying steric bulk were prepared in order to evaluate the effect on catalytic conversion. The activity of the palladium catalysts in Suzuki cross-coupling reactions has been established. The catalysts prepared by immobilising pre-formed palladium complexes gave superior results for the conversion of aryl bromides and aryl chlorides. In addition, use of sterically bulky NHCs (such as the N-2,6-(diisopropyl)phenyl-substituted ligand) resulted in increased catalytic activity, which is analogous to the trends noted in homogeneous catalysis.     

Electron transport membrane: Preparation of polypeptide membrane with spacers between the polymer matrix and viologen moiety and their application to an electron transfer reaction

Polypeptide membranes with several lengths of spacers [? (CH₂)_n? ; n = 3, 6, 12] between the polymer matrix and viologen moiety as a functional group were prepared. Reduction of K₃Fe(CN)₆ with Na₂S₂O₄ across the obtained membrane in aqueous media were carried out and reduction rate of K₃Fe(CN)₆ across the membrane of n = 6 was faster than that of n = 3. However, the reduction of the membrane (n = 12) did not proceed chemically and electrochemically at all.     

Fabrication of hollow palladium spheres and their successful application to the recyclable heterogeneous catalyst for suzuki coupling reactions

Novel palladium hollow spheres were synthesized using silica spheres as a template, and they were successfully applied as recyclable heterogeneous catalysts for Suzuki cross coupling reactions.     

Effect of high rates of mass transport on oxygen reduction at copper electrodes: Implications for aluminium corrosion

The reduction of oxygen at copper microelectrodes (25 μm diameter) in aqueous solution (pH 7) has been studied under conditions of high mass transport, similar to those experienced by μm sized copper-containing inclusions in aluminium alloys during corrosion. Contrary to previous studies at copper electrodes operating at lower mass transport rates, oxygen reduction limiting currents show an apparent number of electrons which decrease towards 2 as the mass transport rate increases (mass transfer coefficients up to ca. 0.55 cm s⁻¹), rather than a 4-electron process. These new data suggest that the treatment of oxygen reduction as a 4-electron transfer process at micron and smaller-sized copper intermetallics in aluminium alloys may require revision.     

可用于环境修复的半导体光催化剂及其改性策略研究进展

多相光催化技术作为一种直接利用太阳光降解多种污染物的先进氧化工艺在环境修复领域的研究中引起了广泛关注.在多相光催化过程中,半导体材料在太阳光的激发下,其强大的氧化/还原能力可快速高效降解各种污染物.研究者通常根据环境中污染物的状态和种类选择合适的半导体材料及修饰策略,构建高效多相光催化体系,探究光催化材料在环境修复中的...     

Plenary lecture: Ion enthalpies and their application in mass spectrometry

The experimental determination of ionization and appearance energies is discussed, together with the calculation of heats of formation of ions. Results are presented for the ions [C_nH_2n+1]⁺, [C_nH_2n+2N]⁺ and [C_nH_2n+1O]⁺. The low temperature (～350K), low energy (12.1eV) mass spectra of some alkanes, amines and alcohols are presented and discussed.     

Preparation of microgels and their industrial application as fluidity controlling agents

Microgels, intramolecularly crosslinked macromolecules with sizes of less than 100 nm, were originally manufactured via an emulsion polymerization process involving the use of novel amphiphilic oligomers containing the zwitterion moiety as emulsifiers. Application of microgels as additives to coatings has been studied here. Newtonian flow of an original coating composition was altered to pseudoplastic flow by the addition of microgels. The mechanism of this fluidity alteration was discussed in terms of electron microscopic observation of the coating composition.     

A new approach to determining gas-particle reaction probabilities and application to the heterogeneous reaction of deliquesced sodium chloride particles with gas-phase hydroxyl radicals

The reaction kinetics for gaseous hydroxyl radicals (OH) with deliquesced sodium chloride particles (NaCl(aq)) were investigated using a novel experimental approach. The technique utilizes the exposure of substrate-deposited aerosol particles to reactive gases followed by chemical analysis of the particles using computer-controlled scanning electron microscopy with energy-dispersive analysis of X-rays (CCSEM/EDX) capability. Experiments were performed at room temperature and atmospheric pressure with deliquesced NaCl particles in the micron size range at 70-80% RH and with OH concentrations in the range of 1 to 7 x 10(9) cm(-3). The apparent, pseudo first-order rate constant for the reaction was determined from measurements of changes in the chloride concentration of individual particles upon reaction with OH as a function of the particle loading on the substrate. Quantitative treatment of the data using a model that incorporates both diffusion and reaction kinetics yields a lower limit to the net reaction probability of gamma(net) > or = 0.1, with an overall uncertainty of a factor of 2.     

Measurement of the reactivity of OH with methyl nitrate: Implications for prediction of alkyl nitrate-OH reaction rates

The rate of the gas phase reaction of hydroxyl radical with methyl nitrate has been measured to be (3.4 ± 0.4) × 10^?14 cm³ molecule^?1 s^?1 at 298 K using flow discharge/ resonance fluorescence techniques. By means of correlation methods, this rate determination is used to predict a vertical ionization potential of 12.6 eV, a bond dissociation energy for H? CH₂ONO₂ of 101 kcal mol^?1, and a rate for O(³P) reaction with methyl nitrate of ca. 9 × 10^?17 cm³ molecule^?1 s^?1. In conjunction with previously derived relative data for reaction of alkyl nitrates with OH radical in the gas phase, a priori estimated reactivities for 1-, 2-, and 3-positionally substituted straight chain alkyl nitrates have been reexamined. Revised reactivities for OH abstraction of specific hydrogens substituted on straight chain alkyl nitrates are presented and discussed, and an atmospheric lifetime of ca. 2 yrs is estimated for methyl nitrate removal due to OH.     

Sol-gel route to zirconia-Pt-nanoelectrode arrays 8 nm in radius: their geometrical impact in mass transport

The fabrication of advanced nanoelectrode arrays and their electrochemical characterization are presented. These nanoelectrode arrays are constituted of nanoperforations of 8 nm in radius leading to platinum and protected by an inorganic matrix made of crystalline zirconia. These nanoelectrodes arrays provide a ceramic support with a high thermal and chemical stability. These devices present a well characterized structure with a control of size, shape, and spacing of the nanoelectrodes, allowing studying in depth both the mass transport and the charge transfer properties in the nanometer range. The radial diffusion occurs when the experimental scan rate is superior to a theoretical scan rate estimated from the model proposed by Amatore and colleagues. The coupling between electrochemical analysis and nanoscale structural characterizations successfully demonstrates that the theory defined for microelectrode arrays can be directly transposed for well-defined metal-ceramic nanocomposite nanoelectrodes.     

Preparation of metal "nanosalts" and their application in catalysis: heterogeneous and homogeneous pathways

A novel type of nanoparticles have been designed based on self-organization of the metal centers with organic functional groups. Size- and shape-controlled synthetic procedures were developed to prepare nanostructured Pd and Ni particles in high yields from easily available precursors. The presence of the non-metallic functional groups in the particle's core forced the metal centers to adopt a divalent oxidation state bearing polar chemical bonds ("nanosalt"). The Pd and Ni particles were excellent catalysts to accomplish a highly selective synthetic route to vinyl chalcogenides. The mechanisms of the catalytic reactions via the heterogeneous and homogeneous pathways were revealed and studied in detail.     

Simultaneous application of two or more supported liquid-phase organometallic catalysts: heterogeneous multifunctional reaction systems

Using the form of supported liquid-phase catalysts, two or more homogeneous catalysts can simultaneously be used with retaining their own activities and taking the advantage of catalyst-product separation and catalyst recycling.     

A two-color laser photolysis method for determining reaction rates of short-lived intermediates by product analysis: application to the o-quinodimethane problem

A time-delayed, two-color pulse laser photolysis technique was used for a kinetic study of short-lived transient species through product analysis, the determination of the rate constant of the cycloaddition of o-quinodimethane (1) and maleic anhydride (2) in room-temperature solutions. o-Quinodimethane (1) was generated from 1,2-bis[(phenylseleno)methyl]benzene (3) by the irradiation of a pulse of a KrF excimer laser (248 nm) in the presence of excess 2, and a successive pulse of a XeCl excimer laser (308 nm) was irradiated to the reaction mixture after varied delay times from 0 to 0.1 s for the decomposition of the remaining 1 to quench the cycloaddition reaction. The rate constant of the cycloaddition of 1 and 2 was 2.1 x 10(5) M(-1) s(-1), which was obtained by the analysis of the delay-time dependence of the product yields.     

Electron correlation theories and their application to the study of simple reaction potential surfaces

This paper serves two purposes. The first is to describe an implementation of the coupled cluster theory with double substitutions (CCD ) previously developed by Cizek. The second is to apply this method and closely related fourth-order perturbation methods to some simple molecules and reaction potential surfaces. These studies show that CCD theory gives results close to those of a Møller-Plesset perturbation treatment to fourth order in the space of double and quadruple substitutions MP 4(DQ). Addition of contributions from single substitutions at fourth order makes little change in predicted relative energies. Preliminary results on the potential surfaces for 1,2-hydrogen shifts in C₂H₂, HCN, CH₂O, and N₂H₂ are discussed and compared with previous studies.     

Reactive MALDI mass spectrometry: application to high mass alkanes and polyethylene

A molecular solid of fullerene (C(60)) intercalated with cobalt cyclopentadienyl dicarbonyl (CoCp(CO)(2)) was shown to be an effective matrix for matrix-assisted laser desorption/ionization mass spectrometry (MALDI) of large alkanes (demonstrated up to C(94)H(190)) and polyethylenes that otherwise cannot be produced as intact ions in the gas phase.     

Statistical rates for reactions on heterogeneous surfaces: The influence of non-ideal collisions

Using the random patch model, kinetic expressions are derived for the pressure dependence of first- and second-order surface reactions. Collisions beteen gas-phase and adsorbed molecules which affect the desorption probability are taken into account. For first-and second-order reactions a representation for the rates is given in terms of incomplete gamma functions for three distributions. These collisional effects cause the surface rates to rise steeply in a narrow range of pressure, due to the exponential dependence of the local isotherm on pressure.     

Synthesis of monodentate ferrocenylphosphines and their application to the palladium-catalyzed Suzuki reaction of aryl chlorides

Racemic and enantiopure ((p)()S)-1-bromo-2-methylferrocene 6 were synthesized in 4 steps from 2-(4,4-dimethyloxazolinyl)ferrocene and (S)-2-(4-methylethyloxazolinyl)ferrocene, respectively (46 and 81% overall yield). Bromolithium exchange and addition of ClPR(2) gave the corresponding racemic or enantiopure 2-methylferrocenyl phosphine ligands 2-MeFcPR(2) 11 (R = Ph), 12 (R = Cy), and 13 (R = (t)Bu) in 28-93% yield. Use of PCl(3) gave the C(3)-symmetric phosphine (2-MeFc)(3)P 5 from ((p)()S)-6(72% yield) but racemic 6 did not lead to the formation of triferrocenyl phosphines. Combination of 5 and Pd(2)(dba)(3) gave an active catalyst for the Suzuki reaction of aryl chlorides, for example, 4-chlorotoluene and phenylboronic acid reacted at only 60 degrees C in dioxane (86% yield). Other examples are reported together with the use of 12 in this same protocol. From the X-ray crystal structure of 5 the cone angle was determined as 211 degrees. With this, and the electronic character of 11, 12, and other phosphines (derived from nu(CO) of trans-[(R(3)P)(2)Rh(CO)Cl]), an analysis is made of the steric and electronic influences on ligand activity in the Suzuki reaction.