Experimental and Theoretical Study of Hydrogen Atom Abstraction from Ethylene by Stoichiometric Zirconium Oxide Clusters

The reactions of cationic zirconium oxide clusters （ZrxOy^＋） with ethylene （C2H4） were investigated by using a time-of-flight mass spectrometer coupled with a laser ablation/supersonic expansion cluster source. Some hydrogen containing products （ZrO2）xH^＋（x=-1-4） were observed after the reaction. The density functional theory calculations indicate that apart from the common oxygen transfer reaction channel, the hydrogen abstraction channel can also occur in （ZrO2）x^＋＋C2H4, which supports that the observed （ZrO2）xH^＋ may be due to （ZrO2）x^＋＋C2H4→（ZrO2）xH^＋＋C2H3. The rate constants of different reaction channels were also calculated by Rice-Rarnsberger-Kassel-Marcus theory.     

激光溅射Cu等离子体与气相C2H5OH团簇的反应

用激光溅射-分子束技术研究了气相中Cu的等离子体与乙醇分子团簇的反应.观察到三种团簇正离子Cu＋(C2H5OH)n、CuO＋(C2H5OH)n、H＋(C2H5OH)n和三种团簇负离子(C2H5OH)nC2H5O－、(C2H5OH)n(H2O)OH－、(C2H5OH)n(H2O)2OH－(n≤12).详细考察了在不同的载气压力下激光烧蚀等离子体作用于脉冲分子束， 以及在一定的压力下等离子体作用于分子束不同位置时，对团簇产物种类和团簇尺寸大小的影响.分析了Cu＋(C2H5OH)n、CuO＋(C2H5OH)n、H＋(C2H5OH)n、(C2H5OH)nC2H5O－、(C2H5OH)n(H2O)OH－、(C2H5OH)n(H2O)2OH－等团簇的产生机理.     

激光溅射Cu等离子体与气相CH3CN团簇的反应

The gas phase reaction of Cu plasma and acetonitrile clusters is studied by the laser ablation-molecular beam（LAMB） method. Four series of clustered complex ions Cu+（CH3CN）n, CH2CN+（CH3CN）n,H+（CH3CN）n and CH3CHCN+（CH3CN）n are observed. Interestingly,the species and sizes of the product clusters vary observably when the plasma acts on the different parts of the pulsed acetonitrile molecular beam. When the laser ablated Cu plasma acts on the head of the beam,the metal acetonitrile complex clusters Cu+（CH3CN）n together with protonated acetonitrile clusters H+（CH3CN）n and deprotonated acetonitrile clusters CH2CN+ （CH3CN）n are domain,while the plasma acts on the middle of the beam. However,CH2CN+（CH3CN）n and H+（CH3CN）n along with the clusters CH3CHCN+（CH3CN）n turn out to be the main resulting clusters. By comparing the intensities and the cluster sizes of CH3CHCN+（CH3CN）n with H+（CH3CN）n and CH2CN+（CH3CN）n,the formation of CH3CHCN +（CH3CN）n is contributed to the intracluster ion-molecule reaction of acetonitrile clusters.     

Ag/Se二元团簇的形成以及Ag与Se团簇反应的研究

用飞行时间质谱仪研究了激光直接溅射Ag/Se混合样品产生的二元团簇以及团簇正离子的光解行为;并用串级溅射反应装置研究了Ag和Se正负离子产物.在直接溅射产生的Ag/Se二元团簇中,正离子主要系列是:[(Ag₂Se)_nAg⁺],[(Ag₂Se)_nAg₃⁺];负离子主要系列是:[(Ag₂Se)_nAgSe^-],[(Ag₂Se)_nAgSe₂^-],[(Ag₂Se)_nSe^-].团簇正离子的光解结果表明,同样条件下Ag/Se二元团簇正离子光解比率比Ag/S大.在Ag和Se样品串级溅射实验中,主要得到AgSe_n⁺(n=4～9)和AgSe_nSe^-(n=4～7)系列的产物,在AgSe_n⁺系列中,n=4,6时丰度较大.这表明串级溅射反应和直接溅射二元混合样品两种过程中成簇机理是不同的.     

钒氧阴离子团簇与小分子碳氢化合物反应的实验和理论研究(英文)

为了在分子层次上揭示相关催化反应的机理,人们对过渡金属氧化物团簇与碳氢化合物分子反应进行了大量研究.相比于过渡金属氧化物团簇阳离子,阴离子对一些碳氢化合物的活性弱得多,因此研究还很少.在本工作中,我们通过激光溅射产生钒氧团簇阴离子VxOy-,产生的团簇在接近热碰撞条件下与烷烃(C2H6和C4H10)以及烯烃(C2H4和C3H6)在一个快速流动反应管中进行反应,飞行时间质谱用来检测反应前后的团簇分布.在VxOy-与烷烃的反应中,生成了产物V2O6H-和V4O11H-;在与烯烃的反应中,产生了相应的吸附产物V4O11X-(X=C2H4或C3H6).密度泛函理论计算表明:V2O6-和V4O1-1可以活化烷烃(C2H6和C4H10)的C-H键,也可以与烯烃(C2H4和C3H6)发生3+2环化加成反应形成一个五元环结构(-V-O-C-C-O-),C-H键活化与环加成反应都需经历可以克服的反应能垒.理论计算与实验观测结果相符合.V2O6-和V4O1-1团簇都具有氧原子自由基(O·或O-)的成键特征,活性O-物种也经常出现在钒氧催化剂表面,因而本研究在分子水平上,揭示了表面活性氧物种与碳氢化合物反应的机理.     

A Molecular Placeholder Strategy To Access a Family of Transition‐Metal‐Functionalized Vanadium Oxide Clusters

Systematic access to metal‐functionalized polyoxometalates has thus far been limited to lacunary tungsten oxide and molybdenum oxide clusters. The first controlled, stepwise bottom‐up assembly route to metal‐functionalized molecular vanadium oxides is now presented. A di‐vacant vanadate cluster with two metal binding sites, (DMA)₂[V₁₂O₃₂Cl]^3? (DMA=dimethylammonium) is formed spontaneously in solution and characterized by single‐crystal X‐ray diffraction, ESI mass spectrometry, ⁵¹V NMR spectroscopy, and elemental analyses. In the cluster, the metal binding sites are selectively blocked by hydrogen‐bonded DMA placeholder cations. Reaction of the cluster with transition metals TM (Fe³⁺, Co²⁺, Cu²⁺, Zn²⁺) gives access to mono‐functionalized vanadate clusters (DMA)[{TM(L)}V₁₂O₃₂Cl]^n? (L=ligand). Metal binding is accomplished by significant distortions of the vanadium oxide framework reminiscent of a pincer movement. Cluster stability under technologically relevant conditions in the solid‐state and solution is demonstrated.     

Experimental and Theoretical Study of Hydrogen Atom Abstraction from C2H6 and C4H10 by Zirconium Oxide Clusters Anions

The reactions of anionic zirconium oxide clusters Zr_xO_y^- with C₂H₆ and C₄H₁₀ are investi-gated by a time of flight mass spectrometer coupled with a laser vaporization cluster source.Hydrogen containing products Zr₂O₅H^- and Zr₃O₇H^- are observed after the reaction. Den-sity functional theory calculations indicate that the hydrogen abstraction is favorable in the reaction of Zr₂O₅^- with C₂H₆, which supports that the observed Zr₂O₅H^- and Zr₃O₇H^- are due to hydrogen atom abstraction from the alkane molecules. This work shows a newpossible pathway in the reaction of zirconium oxide cluster anions with alkane molecules.     

Development of a SIMION-Simulated Ion Funnel Tube for Proton Transfer Reaction Mass Spectrometry

Because the optimum working pressure of ion funnel (IF) is very close to the typical operating pressure of a traditional drift tube for proton transfer reaction mass spectrometry (PTR-MS), it is possible to develop an IF drift tube for PTR-MS to improve the sensitivity. In this study, an ion funnel capable of functioning as a drift tube in a PTR-MS system was designed and studied by computer simulation. To optimize the geometrical and electrical parameters of the ion funnel, five ion funnel configurations were constructed. The merits and features of the respective ion funnels were evaluated, and the ion transmission characteristics were investigated and analyzed. An optimized ion funnel model was compared against the typical traditional drift tube that was used in PTR-MS for ion transmission, and it was found that the ion traveling trajectories in the ion funnel and traditional drift tube had different shapes and ion transmission efficiencies. Preliminary investigations revealed that this ion funnel improved the ion transmission efficiency by at least 10 times. The simulation and experiment results are helpful in guiding the design of an improved ion funnel to develop a PTR-MS system with higher sensitivity.     

纳米尺寸氧化钇团簇阴离子与正丁烷反应的研究

在单一原子量分辨水平上研究纳米尺寸过渡金属氧化物团簇(M_xO_y^q)与小分子的反应不仅能够获得氧化物纳米颗粒的反应性随原子组成和尺寸连续变化的演变规律, 而且对认识其结构特征以及表面活性氧物种(如O^-•自由基)的产生机制等具有重要意义. 本工作分别采用耦合快速流动反应管和耦合四极质量过滤器-线形离子阱的两套反射式飞行时间质谱研究了不同“氧缺陷指数”(Δ)的氧化钇团簇Y_xO_y^- (x≤50,y≤76; Δ≡2y–1–3x, Δ=0~5)和掺杂氟(F)原子团簇Y _xO_yF^- [x≤49,y≤74; Δ≡(2y+1)–1–3x, Δ=1]与 n-C₄H₁₀分子的反应. 实验观测到Δ=1系列团簇(Y₂O₃)_NO^- (N=1~25)、(Y₂O₃)_NYO₂F^- (N=1~24)及Δ=4系列团簇(Y₂O₃)_NYO₄^- (N=1, 3~24)具有氢抽取反应活性, N≥2时其它Δ系列团簇(Δ=0, 2, 3, 5)在相同实验条件下没有表现出明显的反应性. 密度泛函理论研究Δ=1或4系列小尺寸团簇(Y₂O₃)_NY_xO_yF_0,1^- (N≤4;x=0, 1)的结构揭示O^-•自由基是氢抽取反应的活性位点, 结合实验可推测Δ=1或4系列纳米尺寸团簇(Y₂O₃)_NY_xO_yF_0,1^- (x=0, 1)结构中也含有O^-•自由基. 这些结果表明Δ=0系列惰性纳米尺寸团簇(Y₂O₃)_NYO₂^-可以通过吸附一个O₂分子发生电子转移生成O^-•自由基(O^2-+O₂→O^-•+O₂^-•), 也可以通过掺入F原子的方式生成O^-•自由基(O^2-+F^•→O^-•+F^-).     

Use of a Carbon Paste Electrode Modified with Spinel‐Type Manganese Oxide as a Potentiometric Sensor for Lithium Ions in Flow Injection Analysis

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel‐type manganese oxide (lambda‐MnO₂), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li⁺ against other alkali and alkaline‐earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6×10^?5–1.0×10^?2 mol L^?1 with a slope 78.9±0.3 mV dec^?1 over a wide pH range 7–10 (Tris buffer), without interference of other alkali and alkaline‐earth metals. For a flow rate of 5.0 mL min^?1 and a injection sample volume of 408.6 μL, the relative standard deviation for repeated injections of a 5.0×10^?4 mol L^?1 lithium ions was 0.3%.     

Studies of the Methane Steam Reforming Reaction at High Pressure in a Ceramic Membrane Reactor

The effects of temperature and pressure on the steam reforming of methane 3H2+CO) were investigated in a membrane reactor (MR) with a hydrogen permeable membrane. The studies used a novel silica-based membrane prepared by using the chemical vapor deposition (CVD) technique with a permeance for H2 of 6.0×l0-8 mol·m-2·s-1·Pa-1 at 923 K. The results in a packed-bed reactor (PBR) were compared to those of the membrane reactor at various temperatures (773-923 K) and pressures (1-20 atm, 101.3-2026.5 kPa) using a commercial Ni/MgAl2O4 catalyst. The conversion of methane was improved significantly in the MR by the countercurrent removal of hydrogen at all temperatures and allowed product yields higher than the equilibrium to be obtained. Pressure had a positive effect on the hydrogen yield because of the increase in driving force for the permeance of hydrogen. The yield of hydrogen increased with pressure and reached a value of 73×10-6 mol·g-1·s-1 at 2026.5 kPa and 923 K which was higher by 108% than the value of 35×10-6 mol·g-1·s-1 obtained for the equilibrium yield. The results obtained with the silica-based membrane were similar to those obtained with various other membranes as reported in the literature.     

柱前衍生／流动注射微柱预富集和ICP－AES法测定高纯氧化钅兰中痕量非稀土元素

利用自合成的碳硅凝胶为吸附材料，以铜试剂（ＮａＤＤＴＣ）为柱前衍生试剂，实现了Ａｌ（Ⅲ）、Ｃｒ（Ⅵ）、Ｃｕ（Ⅱ）、Ｆｅ（Ⅲ）、Ｖ（Ⅴ）流动注射（ＦＩ）微柱预富集．以稀ＨＮＯ３停流洗脱富集物，ＩＣＰ－ＡＥＳ法测定洗脱液中上述元素．在优化条件下，富集倍数近１０倍，检出限为ｎｇ／ｍＬ级，ＲＳＤ＜５．０％（ｎ＝７），方法用于高纯Ｌａ２Ｏ３中非稀土杂质测定，结果满意     

Indirect Spectrophotometric Determination of Vanadium(IV) by Flow Injection Analysis Based on the Redox Reaction with Copper(II) in the Presence of Neocuproine

Abstract

An indirect photometric method with a continuous-flow analysis is presented for the determination of trace amounts of vanadium(IV). It is based on the redox reaction of copper(II) with vanadium(1V) in the presence of neocuproine. In the presence of neocuproine, copper(I1) is reduced easily by vanadium(I V) to a copper(1)-neocuproine complex, which shows a n absorption maximum at 454 nm. By measuring t h e absorbance of the complex at this wavelength, vanadium(1V) in t h e range 2×10^?6 - 8 × mol dm^?5 mol dm^?3 can be determined at a rate of 120 samples h^?1. The fractional determination of vanadium(1V) and iron(I1) is also studied.     

利用手持技术与T形玻璃管探究钠与空气中的氧气反应*

针对钠与氧气反应教学中存在的不足,引入手持技术数字化创新实验,自主设计创新反应装置T形玻璃管以定量探究钠与氧气反应。本研究利用氧气传感器,通过测定密闭体系内氧气含量的变化,帮助学生基于四重表征模型、从定性和定量的角度认识钠与空气中的氧气在室温和加热条件下反应的区别;借助氧气、二氧化碳、湿度等3种传感器从定量的角度探究空气中的二氧化碳与水蒸气对钠的影响,形成对钠与氧气反应的科学认知。     

Flow injection spectrophotometry coupled with a crushed barium sulfate reactor column for the determination of sulfate ion in water samples

A new type of a reactor column, a crushed BaSO₄ reactor column used for the flow injection spectrophotometric determination of sulfate ion using the exchange reaction of sulfate ion and barium-dimethylsulfonazo III is proposed. The column is very simple and economical. It can be continuously used for 8 h before washing with water for repeated usage of at least 1 month. The procedure is sensitive. Application to various water samples was demonstrated.     

A vacuum ultraviolet photoionization time-of-flight mass spectrometer with high sensitivity for study of gas-phase radical reaction in a flow tube

Photoionization mass spectrometry as a powerful analytical method has been widely utilized and provided valuable insight in the field of gas-phase reactions. Here, a highly sensitive vacuum ultraviolet (VUV) photoionization time-of-flight mass spectrometer combined with a microwave discharge generator and a fast flow tube reactor has been developed to study radical reactions of atmospheric and combustion interests. Two kinds of continuous light sources, the tunable VUV synchrotron radiation at Hefei, China for isomer-specific product detection and a commercial krypton discharge lamp for time-consuming kinetic measurements, are employed as photoionization sources in the apparatus. A multiplexed detection with high sensitivity (the limit of detection ∼0.8 ppb) and high mass resolution (M/ΔM ∼ 2100) has been approached. As representative examples, the self-reaction of the methyl radical, CH₃, and the reaction of the methyl radical with molecular oxygen are studied and multiple species including reactive radicals and isomeric/isobaric products are detected and identified. In addition, some preliminary results related to the reaction kinetics are also presented.     

氧泵型催化膜反应器中甲烷氧化偶联反应—SEM和XPS研究

氧泵型催化膜反应器中甲烷氧化偶联反应—ＳＥＭ和ＸＰＳ研究国秀梅，陈洪钫（天津大学化工系，天津３０００７２）关键词甲烷氧化偶联，氧泵型催化膜反应器，ＳＥＭ，ＸＰＳ由于氧泵型催化膜反应器具有可简化分离过程，改变催化剂性质，控制传递氧量，避免副反应发生等优...     

Multilayer‐Functionalized Reduced Graphene Oxide Decorated with Gold Nanoparticles as a Designed Nanonanocatalyst for the Selective Oxidation of Cyclohexene by Molecular Oxygen in a Solvent‐Free System

The aerobic oxidation of cyclohexene is of great significance from the viewpoints of both fundamental and industry studies as it can transfer the petrochemical feedstock into valuable chemicals. In this research, gold nanoparticles were synthesized on the multi‐layer functionalized reduced graphene oxide . The surface of reduced graphene oxide (rGO) was modified with hydrophobic and hydrophilic layers to create the rGO with scattered hydrophilic positions. The gold nanoparticles were synthesized and immobilized simultaneously in small hydrophilic micro reactors in a mild condition. Characterization of synthesized nanocatalyst was confirmed with different techniques such as TEM, XRD, FT‐IR, and SEM. TEM images of synthesized catalyst show the gold nanoparticles have diameters less than 5 nm. Designed nanonanocatalyst was investigated for the selective liquid phase oxidation of cyclohexene with molecular oxygen in solvent free condition which after optimized conditions a maximum of 88% conversion and 91% selectivity was obtained.     

Analytical challenges in doping control: Comprehensive two-dimensional gas chromatography with time of flight mass spectrometry,a promising option

Doping control screening based on the enhanced resolution of comprehensive two-dimensional (2D) gas chromatography hyphenated to time of flight mass spectrometer was investigated. The identification of anabolic agents (clenbuterol, norandrosterone, epimetendiol, two methyltestosterone metabolites and 3′-hydroxystanozolol) contained in a spiked urine sample (2 ng/ml) was demonstrated. Special emphasis was given to 3′-hydroxystanozolol, mainly considering the difficulty in its detection. In contrast to conventional GC–MS approaches that must use single-ion monitoring, the GC × GC–TOFMS method enabled the identification of that metabolite through the deconvolution of the full mass spectrum and also resolved the co-eluted peaks of 3′-hydroxystanozolol and an endogenous component.