钼酸盐对卷烟燃烧氧化反应的催化作用

用自吸烟机、气相色谱,高效液相色谱和电子自旋波谱分别检测钼酸盐处理的卷烟和对照卷烟的燃烧速度,烟气焦油量,焦油中BaP和自由基的浓度,用差热分析和热失重分析探讨反应机理,结果表明,钼酸盐添加剂对降低卷烟燃烧反应的活化能,提高卷烟的燃烧速度,降低烟气焦油量,焦油中BaP和自由基有较高的活性。     

燃烧反应动力学研究进展

化学反应动力学是燃烧过程分析的重要工具。燃烧微观反应过程、复杂反应机理、燃烧实验测量和湍流燃烧数值模拟等方面的研究工作已经取得了长足进步。本文主要介绍燃烧反应动力学研究方法,包括电子结构方法、燃烧反应热力学和速率常数的计算方法、燃烧详细机理构建和简化、反应力场分子模拟以及燃烧中间体测量、燃料点火延迟和光谱诊断等方面的研究现状。燃烧反应动力学具有很强的应用背景,燃烧过程化学物种的反应速率计算是湍流燃烧数值模拟的一个中心任务。由于燃烧反应网络的高度复杂性,我们对燃烧机理的认识还远不清楚。化学反应和湍流相互作用研究的深入、燃烧反应动力学和计算流体力学的协同发展,将对新燃料设计、燃烧数值模拟、发动机内流道流场结构的准确描述产生深远影响。     

Synthesis of boron and nitrogen co-doped graphene nano-platelets using a two-step solution process and catalytic properties for oxygen reduction reaction

Chemically modified graphenes (CMGs) show great promise for various applications owing to the feasibility of their low-cost mass production and good solution processability. Recently, hetero-atom-doped CMGs have been suggested as good candidate materials for electrochemical catalysts in oxygen reduction reaction (ORR). In this study, we synthesized B, N co-doped graphene nano-platelets (BN-rG-O) using a two-step solution process with sequential reaction of graphene oxide with borane tetrahydrofuran and hydrazine monohydrate. In the ORR measured in a basic medium (0.1 M KOH), BN-rG-O exhibits an onset potential of 0.81 V (vs. reversible hydrogen electrode), follows near four electron pathway, and shows excellent stability against methanol poisoning and during durability tests.     

β-胺基烷基膦及其在不对称合成中的应用

本文综述了β－胺基烷基膦手性配体的制备、与金属中心的配位性质及其在Grignard试剂不对称偶联反应中的应用。     

Catalyst preparation by combustion synthesis for electrochemical hydrocarbon devices

Metals and ceramics can behave as active electrocatalyst materials, particularly in hydrocarbon oxidation in anodic reaction fuel cells. Combustion synthesis is a very reliable, fruitful and rapid synthesis method to produce metals, ceramics and cermets with low particle size and high specific surface area. This work describes the preparation of nanoparticle Pt/Ru alloys, ceramic perovskites such as Sm_0.95CoO_3–, and Sm_0.95CoO_3–/Pt cermets, and shows how promising these materials can be in the role of electrochemically active materials.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

Activity of a New Metallomicelle Catalytic System on the Hydrolysis of bis(4-nitrophenyl) Phosphate Ester

A new metallomicellar system containing cerium ion (III), a macrocylic polyamine ligand and the hexadecyltrimethyl ammonium bromide (CTAB) was constructed and used as catalyst in the hydrolysis of bis(4-nitrophenyl) phosphate ester (BNPP). The catalytic rate of BNPP hydrolysis was measured kinetically with UV-vis spectrophotometric method. The results indicated that the metallomicellar system exhibited relatively high stability and excellent catalytic function in BNPP hydrolysis, and the reaction rate of the BNPP catalytic hydrolysis, compared with BNPP spontaneous hydrolysis, increased by a factor of ca. 1 × 10⁸ due to the catalytic effect of the active species and the local concentration effect of the micelle in metallomicellar system. The experimental results also showed that the mono-hydroxy complex made of the macrocyclic polyamine ligand and cerium (III) is the real active species as catalyst in BNPP catalytic hydrolysis, and the micelles provide a useful catalytic environment for reaction. On the basis of the research results, the reaction mechanism of BNPP catalytic hydrolysis was proposed in this work.     

The combustion synthesis of iron group metal fine powders

The new approach has been developed for the synthesis of nickel (Ni), cobalt (Co) and iron (Fe) powders from the appropriate oxides by the solid combustion method. The reduction was made by sodium azide (NaN₃) at the presence of carbon in the argon atmosphere. The variation of combustion temperature and velocity was performed by using alkali metal salt as an inert diluent. The values of combustion parameters were measured and also the temperature distribution in a combustion wave are obtained. The geometric sizes of reactionary zones and the activation energy of the process were estimated. The optimum conditions for single-phase metal powder synthesis were found. Powders fabricated in this way had cubic structure and particles size about 0.5-2.0 μm for Ni, Co and 1-3 μm for Fe. In a number of cases the formation of spherical particles with the average size about 5-15 μm were observed.     

Controllable synthesis and catalysis application of hierarchical PS/Au core-shell nanocomposites

Polystyrene (PS)/gold (Au) core-shell nanocomposites with tunable size, high stability, and excellent catalytic activity have been synthesized by a facile method that combines the ionic self-assembly with the in situ reduction. The composition and stoichiometry, as well as its morphology and optical properties of these nanocomposites have been examined and verified by various characterization techniques. The size and the coverage of gold nanoparticles (NPs) can be simply tailored by changing the amount of 3-aminopropyltrimethoxysilane (APTES), the functionalization time, the protonation time, and the amount of chloroauric acid (HAuCl₄). The continuous red shifts of the localized surface plasmon resonance absorption of the Au NPs on the PS spheres are observed. Importantly, the obtained Au NPs with controllable and uniform size on the surfaces of amino-functionalized PS spheres exhibit excellent size-dependent catalytic properties for the reduction of 4-nitrophenol (4-NP) by NaBH₄.     

锂掺杂ZnO陶瓷靶材制备及其掺杂引起的缺陷

采用燃烧合成和放电等离子烧结方法制备锂掺杂ZnO陶瓷靶材. 利用XRD, SEM, TEM和激光粒径分析等手段分析合成粉体与陶瓷的显微结构. 结果表明, 锂掺杂ZnO粉体与陶瓷均为纤锌矿结构, 无其他相存在; 粉体的粒径分布为0.18-1.7 μm, 烧结体致密度较高, 晶粒尺寸为1-3 μm. 此外, 分析锂元素在烧结过程中引起掺杂缺陷变化, 锂元素由ZnO晶格的间隙位置转移为替代锌晶格位置, 实现受主掺杂, 为实现p型ZnO薄膜的制备奠定基础.     

Combustion synthesis and luminescent properties of metal yttrium borates M3Y2 (BO3)4:Eu3+ (M = Ba,Sr) for PDPs applications

The polycrystalline powder samples of Eu³⁺ activated; mixed metal yttrium borate phosphors M₃Y₂(BO₃)₄ (M = Ba, Sr) with improved color purity of red emission for plasma display panels (PDPs) were prepared by solution combustion technique. The synthesis is based up on the exothermic reaction between the fuel (Urea) and oxidizer (Ammonium nitrate) .The heat generated in the reaction is utilized for auto combustion of ingredients. The formation of desired product and crystal structure was confirmed by powder XRD technique; while particle morphology was studied using FE-SEM. Samples under 254 and 147 nm excitation showed intense and pure red emission around 613 nm corresponding to the electric dipole ⁵D₀ → ⁷F₂ transition of Eu³⁺, CIE chromaticity coordinates of synthesized phosphors was found to be (x = 0.67, y = 0.32) close to National Television Standard Committee (NTSC) for red color; found suitable to employ in plasma display panels (PDPs) applications.     

Current challenges related to the deployment of shape-controlled Pt alloy oxygen reduction reaction nanocatalysts into low Pt-loaded cathode layers of proton exchange membrane fuel cells

The reduction of the amount of platinum used in proton exchange membrane fuel cell cathodes at constant power density helps lower the cell stack cost of fuel cell electric vehicles. Recent screening studies using the thin film rotating disk electrode technique have identified an ever-growing number of Pt-based nanocatalysts with oxygen reduction reaction Pt-mass activities that allow for a substantial projected decrease in the geometric platinum loading at the cathode layer. However, the step from a rotating disk electrode test to a membrane electrode assembly test has proved a formidable task. The deployment of advanced, often shape-controlled dealloyed Pt alloy nanocatalysts in actual cathode layers of proton exchange membrane fuel cells has remained extremely challenging with respect to their actual catalytic activity under hydrogen/oxygen flow, their hydrogen/air performance at high current densities, and their morphological stability under prolonged fuel cell operations. In this review, we discuss some of these challenges, yet also propose possible solutions to understand the challenges and to eventually unfold the full potential of advanced Pt-based alloy oxygen reduction reaction catalysts in fuel cell electrode layers.     

Mercury-catalyzed synthesis of heterocycles

Due to significant biological activity associated with N-, O- and S-heterocycles, a number of reports for their synthesis have appeared in recent decades. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. This review summarizes the applications of mercury metal with emphasis of their synthetic applications for heterocylces. In summary, this review article describes the synthesis of different sized heterocyclic rings containing different heteroatoms.     

Asymmetric Syntheses with the Aid of Homogeneous Transition Metal Catalysts

The progress made in the field of homogeneous catalysis during the last five to six years has led, inter alia, to the development of highly selective catalysts for asymmetric syntheses. Homogeneous asymmetric hydrogenation, using well defined transition metal catalysts, may be achieved with optical yields of 85 to 90% or more. Catalytic reactions, in which the chiral centers are generated by C? C bond formation, can result in optical yields of 70 to 80%. The hydrogenation catalysts consist primarily of rhodium(I) complexes containing “Homer phosphanes”, phosphanes with chiral C atoms, or optically active amides. Catalysts which induce optical activity through the formation of C? C bonds have been developed from π-allylnickel halides, Lewis acids, and phosphanes containing chiral C atoms. The results obtained signify a breakthrough in an area of catalysis previously restricted to syntheses involving enzymes.     

固定化离子液体在有机合成中的应用

固定化离子液体是将离子液体通过物理吸附或化学键合等方法与固载材料结合而成,不仅保持了离子液体稳定性好、挥发性低、结构可优化等特点,还提高了离子液体的催化活性和重复利用性。固定化离子液体广泛应用于缩合、偶联及不对称合成等反应中。本文介绍了固定化离子液体的制备、固载材料的分类、结合方式及固定化离子液体在有机合成中的应用进展。     

Studies of S-But-3-ynyl and gem-Dimethyl S-But-3-ynyl Thioglycoside Donors in Gold-Catalyzed Glycosylations

Gold-catalyzed glycosylation using S-but-3-ynyl and gem-dimethyl S-but-3-ynyl thioglycoside donors has been investigated for the synthesis of various types of complex oligosaccharides. It was found that 2,2-dimethyl S-but-3-ynyl thioglycoside donors are more reactive than their S-but-3-ynyl thioglycoside counterparts and gave the glycoside products in relatively higher yields.