焦炭催化CO还原NO的反应机理研究

利用密度泛函理论,研究了焦炭催化作用下CO还原NO的化学反应机理,优化得到了均相反应路径以及在Zigzag和Armchair型焦炭表面上的异相反应路径中所有驻点的几何构型与能量,并对三条反应路径进行了动力学分析。结果表明,均相NO还原反应的活化能为254.06 kJ/mol,而Zigzag型与Armchair型焦炭表面NO异相还原反应的活化能分别为86.94与52.16 kJ/mol,说明焦炭在NO还原反应中能够起到催化作用。在焦炭表面进行的CO还原NO的反应路径经历N_2形成、N_2释放及两步CO_2释放四个阶段,最终生成一个N_2分子与两个CO_2分子。此外,通过对比不同路径下异相反应的能量变化与动力学参数可知,焦炭表面结构对NO还原反应特性存在较大影响;与Zigzag型焦炭表面相比,基于Armchair型焦炭表面的NO还原反应决速步能垒值更低且反应速率更快,表明在Armchair型焦炭表面上的NO还原反应更易进行。     

Eleciroreduction of Oxygen on Pyrolytk Graphite Electrode with Adsorbed Layer of Cobalt Tetra.sulfonaied Phthalocyaninc In Acetonitrile and Dimethylformamide

The catjpdoc polarization characteristics indicate that the presence of a pre-adsorbed surface layer of CoTSPc innibits the reduction of O2 to O2- on an ordinary pyroiytic graphite electrode (OPG) in AN and DMF solution of 0. 1 mol/L, TEAP, The transfer coefficient a and the heterogeneous rate constant k for this reaction or, OPG with and without pre-adsorbed CoTSPc obtained by rotating disk electrode method were found to be fairly close to thar obtained by cyclic voltammetry. The a remains almost the same, bat the k de creases by a factor of 2-5 with CoTSPc as compared with OPG alone. The possible reason is that the adsorbed CoTSPc as an anion renders the effective potential diffaence less negative, which thus lowers the rase of O2 reduction.     

Reactivity at the interface of chiral amphiphilic dendrimers. High asymmetric reduction by NaBH(4) of various prochiral ketones.

New amphiphilic dendrimers derived from PAMAM and D-gluconolactone were found to induce chirality in the reduction of prochiral ketones by NaBH(4), in heterogeneous (THF) and homogeneous (water) conditions. The third generation of these amphiphilic dendrimers, G(3)G, was found to be a good chiral ligand for the reduction of various prochiral ketones in heterogeneous conditions. Even with substrates well-known to give poor results (especially linear ketones), good enantioselectivities were obtained. It is also important to notice that under heterogeneous conditions (THF) the dendrimer could be recovered by filtration, regenerated, and recycled (up to 10 times), leading to reproducible results in asymmetric reduction of ketones. We have also discussed the reduction of acetophenone in water. Evidence is presented that the selectivity is dominated by the architecture of the dendrimer and some supramolecular ordering in the position of the ketone at the chiral solvating interface. The results obtained showed a correlation between stereoselectivity of the reduction and the compact character of the dendritic particles.     

紫外吸收光谱法在高通量筛选中的应用

 与传统化合物的单独合成及结构性能测定相比,高通量筛选技术具有简化并缩短发现目标化合物过程的特点. 以紫外吸收光谱法为手段,利用高通量筛选技术考察了Co-Ce/HZSM-5对甲烷还原NOx反应的催化活性. 研制了专用的平行反应器,使每个反应通道的反应温度相同,气体空速相近; 建立了一种高通量初级筛选催化剂库的快速方法,初步评价了不同Co/Ce比的Co-Ce/HZSM-5催化剂样品的催化活性. 结果表明,当w(Co)=2.5%及m(Co)/m(Ce)=2时,催化剂的活性最高,其活性因数达到了0.67.     

卟啉化合物电化学性质研究 Ⅰ.5,10,15,20-四-(4-乙酰氧基苯)卟吩及其Cu、Zn、Fe、Co、Ni配合物的合成及循环伏安研究

本文报道了5,10,15,20-四-(4-乙酰氧基苯)卟吩[T(4AOP)P]及其Cu、Zn、Fe、Co、Ni配合物的合成及其在CH_2Cl_2-0.1mol/1 TBAP体系中的循环伏安(CV)研究结果.CV实验表明:Cu~(2+)、Zn~(2+)、Ni~(2+)离子以稳定的+2价存在于T(4AOP)P中,电子转移反应在卟啉环上进行,而Fe~(3+)、Co~(2+)离子在氧化还原过程中发生价态变化。实验发现:不同金属卟啉在卟啉环上氧化还原顺序及其非均相电子转移反应速率常数与环上π电子云密度成规律性变化.     

Kinetics of oxygen reduction reactions involving catalytic decomposition of hydrogen peroxide: Application to porous and rotating ring-disk electrodes

Kinetic equations for the combined 2- and 4-electron processes for oxygen reduction in alkaline solution are reexamined for mechanisms involving hydrogen peroxide decomposition of heterogeneous catalytic type. It is shown that previous conclusions regarding these mechanisms apply to porous electrodes only under diffusion-limiting conditions. They have particular significance to diagnostic criteria obtained using the rotating ring-disk electrode technique, and new equations derived here permit unambiguous determination of all the rate constants involved in the reaction by separate kinetic measurements on oxygen and hydrogen peroxide containing solutions.     

卟啉化合物电化学性质研究 Ⅰ.5,10,15,20-四-(4-乙酰氧基苯)卟吩及其Cu、Zn、Fe、Co、Ni配合物的合成及循环伏安研究

本文报道了５，１０，１５，２０－四（４－乙酰氧基苯）卟吩（Ｔ（４ＡＯＰ）Ｐ）及其Ｃｕ，Ｚｎ，Ｆｅ，Ｃｏ，Ｎｉ配合物的合成及其在ＣＨ２Ｃｌ２－０．１ｍｏｌ／ＩＴＢＡＰ体系中的循环伏安（ＣＶ）。研究结果。ＣＶ实验表明：Ｃｕ＾２＾＋，Ｚｎ＾２＾＝，Ｎｉ＾２＾＋离子以稳定的＋２价存在于Ｔ（４ＡＯＰ）Ｐ中，电子转移反应在卟啉环上进行，而Ｆｅ＾３＾＋，Ｃｏ＾２＾＋离子在氧化还原过程中发生价态变化。实验发现...     

Hexacyanoferrate as the Electrochemical Probe for 2-Mercaptobenzothiazole Modified Gold Electrode

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｒａｔｅｏｆｅｌｅｃｔｒｏｎｔｒａｎｓｆｅｒｉｓｍｕｃｈａｆｅｃｔｅｄｂｙｓｅｖｅｒａｌｆａｃｔｏｒｓ，ｓｕｃｈａｓｅｌｅｃｔｒｏｄｅｍａｔｅｒｉａｌ，ｅｌｅｃｔｒｏｄｅｆａｂｒｉｃａｔｉｏｎｔｅｃｈｎｉｑｕｅｓ，ｐｏｌ...     

Palladium Supported on Porous Organic Polymer as Heterogeneous and Recyclable Catalyst for Cross Coupling Reaction

Palladium immobilized on an amide and ether functionalized porous organic polymer (Pd@AEPOP) is reported to be an effective heterogeneous catalyst for the Heck cross-coupling reaction of aryl iodides with styrene for the synthesis of diphenylethene derivatives. Excellent yields can be obtained using a 0.8 mol% Pd catalyst loading under the optimized reaction condition. The heterogeneous Pd@AEPOP catalyst can also be applied on the Suzuki reaction and the reduction of nitroarene.     

煤焦催化HCN还原NO的反应机理

通过量子化学密度泛函理论研究了均相和煤焦催化的HCN还原NO反应机理,计算了反应动力学参数。结果表明,均相还原反应的活化能为306 kJ/mol,而煤焦催化的NO还原反应的活化能为136 kJ/mol。典型再燃温度1 400 K下,HCN异相还原NO的反应速率略小于煤焦异相还原NO的反应速率;HCN参与下的煤焦异相还原NO反应较CO参与下的煤焦异相促还原NO反应更易发生。各组分的吸附顺序对HCN异相还原NO的反应有明显的影响;在典型再燃温度下,NO先吸附时煤焦表面的异相还原反应速率常数为5.28×10~(10),比HCN先吸附时最快反应路径的反应速率常数大一个数量级。煤焦对NO还原具有显著的催化作用;煤焦表面作为NO的还原反应位点,对反应气体具有明显的活化作用。     

Core-shell Ag–Pt nanoparticles: A versatile platform for the synthesis of heterogeneous nanostructures towards catalyzing electrochemical reactions

Heterogeneous nanostructures that are defined as a hybrid structure consisting of two or more nanoscale domains with distinct chemical compositions or physical characteristics have attracted intense efforts in recent years. In this review, we focus on the introduction of a number of heterogeneous nanostructures derived using core-shell Ag–Pt nanoparticles as starting materials, including hollow, dimeric and composite structures and also highlight their application in catalyzing electrochemical reactions, e.g., methanol oxidation reaction and oxygen reduction reaction. This review not only shows the capability of core-shell Ag–Pt nanoparticles in producing various heterogeneous nanostructures as starting templates, but also highlights the structural design or electronic interaction that endows the heterogeneous nanostructures with enhanced catalytic properties either in methanol oxidation or in oxygen reduction. Further, we also make some perspectives for more heterogeneous nanostructures that may be prepared by using core-shell Ag–Pt particles or their derivatives so as to offer the readers the opportunities and challenges in this field.     

含氮煤焦还原NO反应路径研究

采用量子化学密度泛函理论结合热力学和动力学分析研究了含氮煤焦还原NO的途径;从微观角度探究了含氮煤焦还原NO的间接还原和直接异相还原两种途径,分析了NO还原过程中的能量变化。结果表明,含氮煤焦先产生中间体NH_2再还原NO(间接还原)的过程决速步能垒值较直接异相还原NO的决速步能垒值高183.76 kJ/mol;由能垒角度分析,含氮煤焦与NO直接发生异相还原的过程更为有利。从热力学角度分析,含氮煤焦直接异相还原NO为可自发进行的单向放热反应,较间接还原过程有利。动力学分析结果表明,含氮煤焦间接还原NO的过程决速步速率常数较直接异相还原至少低10个数量级,说明含氮煤焦直接异相还原NO的路径更容易发生。     

Lead dioxide coating obtained by pulsed current technique

The electrocatalytic β-lead dioxide coating on a Ti/SnO₂ substrate was obtained with the use of the pulsed current technique. The effect of the pulsed current density on the heterogeneous nucleation, on the morphology of the coating as well as on its crystalline form was studied by means of scanning electron microscopy (SEM) and X-ray diffraction. The obtained results indicate that the increase in the pulsed current density induces a preferential heterogeneous nucleation on the substrate, reduces the dimensions of the crystals, effects their orientation and increases the internal stress of the lead dioxide coating.     

Lewis acid double metal cyanide catalysts for hydroamination of phenylacetylene

Double metal cyanides (DMCs) are highly active recyclable heterogeneous catalysts for hydroamination of phenylacetylene with 4-isopropylaniline. The best hydroamination yields are obtained with Zn-Co DMCs, especially if the particle size is decreased by a reverse emulsion synthesis technique.     

Charge heterogeneity of surfaces: mapping and effects on surface forces

The DLVO theory treats the total interaction force between two surfaces in a liquid medium as an arithmetic sum of two components: Lifshitz–van der Waals and electric double layer forces. Despite the success of the DLVO model developed for homogeneous surfaces, a vast majority of surfaces of particles and materials in technological systems are of a heterogeneous nature with a mosaic structure composed of microscopic and sub-microscopic domains of different surface characteristics. In such systems, the heterogeneity of the surface can be more important than the average surface character. Attractions can be stronger, by orders of magnitude, than would be expected from the classical mean-field DLVO model when area-averaged surface charge or potential is employed. Heterogeneity also introduces anisotropy of interactions into colloidal systems, vastly ignored in the past. To detect surface heterogeneities, analytical tools which provide accurate and spatially resolved information about material surface chemistry and potential — particularly at microscopic and sub-microscopic resolutions — are needed.Atomic force microscopy (AFM) offers the opportunity to locally probe not only changes in material surface characteristic but also charges of heterogeneous surfaces through measurements of force–distance curves in electrolyte solutions. Both diffuse-layer charge densities and potentials can be calculated by fitting the experimental data with a DLVO theoretical model. The surface charge characteristics of the heterogeneous substrate as recorded by AFM allow the charge variation to be mapped. Based on the obtained information, computer modeling and simulation can be performed to study the interactions among an ensemble of heterogeneous particles and their collective motions. In this paper, the diffuse-layer charge mapping by the AFM technique is briefly reviewed, and a new Diffuse Interface Field Approach to colloid modeling and simulation is briefly discussed.     

A comparison of heterogeneous and homogeneous kinetics in the formation of a polyurethane

The extent of reaction between a liquid polyfunctional aromatic isocyanate and a diol was studied using infrared spectroscopy to follow the reduction in concentration of the isocyanate group. For the homogeneous conditions the reaction was performed in benzene solution. For the heterogeneous conditions the isocyanate was dispersed as droplets in the diol and the reaction proceeded interfacially. From a proposed model for the interfacial reaction based on the steady-state diffusion theory the second-order rate constant of the reaction can be evaluated. The values obtained were compared to the second-order rate constants obtained for the solution method. For a range of temperature the heterogeneous rate constant was approximately six decades higher than that obtained for the homogenous conditions. However the activation energies obtained corresponded within a factor of 1.5.     

Determination of the Rate Coefficient for the Heterogeneous Recombination of Chlorine Atoms in a Plasma Reactor by the Relaxation Technique

The relaxation technique was used to study the recombination kinetics of atoms in a chlorine plasma. It was revealed that time changes in the parameters of electronegative- and electropositive-gas plasmas under the conditions of pulsed discharge firing differed in character. A procedure was proposed for the treatment of experimental data with the aim of determining the rate coefficient for heterogeneous recombination of chlorine atoms under pulsed discharge excitation. A numerical value for the coefficient of heterogeneous recombination of chlorine atoms on glass was obtained for pure chlorine and chlorine–oxygen plasmas.     

Preparation,characterization, and application of fine metal particles and metal colloids using hydrotriorganoborates

The reduction of transition metal salts and oxides using hydrotriorganoborates in organic media allows the production of X-ray amorphous nanopowders of metals and alloys under mild conditions. For example, the reduction of needle-shaped iron oxides at 80°C in organic solvents leads to acicular iron-magnet pigments suitable for recording magnetic signals. The reduction of TiCl₄ with K[BEt₃H] gives an ether-soluble [Ti(0)·0.5THF]_x which serves as a catalyst for the hydrogenation of titanium or zirconium sponges and related systems and as a powerful activator for heterogeneous hydrogenation catalysts. The use of tetraalkylammonium hydrotriorganoborates as reducing agents leads to colloidal transition metals in organic phases. These colloids may also be obtained using conventional reducing agents after first reacting the metal salts with the stabilizing tetraalkylammonium halide. Colloidal metals prepared in this way serve as sources for heterogeneous metal catalysts.     

On the characterization of disordered and heterogeneous carbonaceous materials by Raman spectroscopy

The applicability of Raman spectroscopy to characterize disordered and heterogeneous carbonaceous materials (CM) is discussed, by considering both natural and synthetic CM. First, different analytical mismatches during the measurement are discussed and technical indications are provided in order to eliminate them. Second, the accuracy and relevance of the different parameters obtained by the decomposition of spectra by conventional fitting procedure, is reviewed. Lastly, a new Raman technique (Raman area mode microspectroscopy) giving an homogeneous repartition of power within a large laser beam is presented, this technique being powerful to study strongly heterogeneous CM and/or photosensitive samples.     

氧在铁卟啉/聚吡咯膜修饰电极上的还原

用旋转环盘电极技术研究含中位四（ 对磺基苯基） 卟啉合铁（ＦｅＴＰＰＳ） 的聚吡咯膜覆盖的玻碳电极上的氧还原过程． 结果表明该修饰膜的存在降低了氧还原的过电位,还原产物中有Ｈ２Ｏ２ ,过程用异相氧化还原催化（ＥＣ） 机理解释． 与金或铂比较,碳是较好的电极基体材料,适合于产生破坏水中有机物所需的过氧化物． 在酸性介质中氧在该膜修饰电极上的还原速度比在中性介质中大,由ＫｏｕｔｅｃｋｙＬｅｖｉｃｈ 关系式求出修饰膜中催化剂和分子氧反应的表观速度常数值．