Cationic Copolymerization of Epichlorohydrin with Styrene Oxide and with Cyclohexene Oxide

Cationic copolymerizations of epichlorohydrin (ECH) (chloro-methyl oxirane) with styrene oxide (SO) (phenyl oxirane) and with 1,2-cyclohexene oxide (CO) (7-oxabicyclo [410] heptane) were carried out at 50°C by employing the salt triphenylmethyl hexachloro-antimonate (HC) (Ph₃CSbCl₆) as initiator. NMR spectra before and after attempted extractions of the polymeric products indicated that the resulting polymeric products were true copolymers and not mixtures of the respective homopolymers. Monomer reactivity ratios for both pairs of comonomers were determined; for one pair the values were r ₁(ECH) = 3.29, r ₂(CO) = 0.16 and for the second pair r ₁(ECH) = 0.57, r ₂(SO) = 0.16.     

A High-Performance Asymmetric Supercapacitor Based on Tungsten Oxide Nanoplates and Highly Reduced Graphene Oxide Electrodes

Tungsten oxide/graphene hybrid materials are attractive semiconductors for energy-related applications. Herein, we report an asymmetric supercapacitor (ASC, HRG//m-WO₃ ASC), fabricated from monoclinic tungsten oxide (m-WO₃) nanoplates as a negative electrode and highly reduced graphene oxide (HRG) as a positive electrode material. The supercapacitor performance of the prepared electrodes was evaluated in an aqueous electrolyte (1 m H₂SO₄) using three- and two-electrode systems. The HRG//m-WO₃ ASC exhibits a maximum specific capacitance of 389 F g⁻¹ at a current density of 0.5 A g⁻¹, with an associated high energy density of 93 Wh kg⁻¹ at a power density of 500 W kg⁻¹ in a wide 1.6 V operating potential window. In addition, the HRG//m-WO₃ ASC displays long-term cycling stability, maintaining 92 % of the original specific capacitance after 5000 galvanostatic charge–discharge cycles. The m-WO₃ nanoplates were prepared hydrothermally while HRG was synthesized by a modified Hummers method.     

介孔氧化铝负载Ni-Co氧化物催化剂上丙烷氧化脱氢制丙烯

以非离子型三嵌段共聚物作为模板剂, 异丙醇铝为氧化铝的前驱物, 采用一锅法合成了一系列介孔氧化铝负载镍氧化物、钴氧化物以及镍-钴双金属氧化物催化剂, 并以介孔氧化铝为载体, 采用浸渍法制备了负载Ni-Co 氧化物催化剂. 采用N₂吸附-脱附、高分辨透射电镜(HRTEM)、X射线粉末衍射(XRD)、H₂程序升温还原(H₂-TPR)以及激光拉曼光谱(LRS)等技术对催化剂的结构与性质进行表征, 并考察了催化剂的丙烷氧化脱氢反应性能. 结果表明: 一锅法制备的各催化剂均有大的比表面积和规整的孔道结构, 且负载的金属氧化物高度分散; 而浸渍法制备的催化剂, 其载体的介孔结构被破坏并有Co₃O₄晶相生成. 在考察的催化剂中, 一锅法合成的介孔氧化铝负载Ni-Co 氧化物催化剂表现出最佳的丙烷氧化脱氢性能. 在450 °C、C₃H₈:O₂:N₂的摩尔比为1:1:4和空速(GHSV)为10000 mL·g^-1·h^-1条件下, 该催化剂上丙烯产率为10.3%, 远高于浸渍法制备的催化剂上所获得的丙烯产率(2.4%). 关联催化剂表征和反应结果, 讨论了催化剂结构与性能之间的关系.     

The Isoelectric Point of an Exotic Oxide: Tellurium (IV) Oxide

The pH-dependent surface charging of tellurium (IV) oxide has been studied. The isoelectric point (IEP) of tellurium (IV) oxide was determined by microelectrophoresis in various 1-1 electrolytes over a concentration range of 0.001–0.1 M. In all electrolytes studied and irrespective of their concentration the zeta potential of TeO₂ was negative over the pH range 3–12. In other words the IEP of TeO₂ is at pH below 3 (if any). TeO₂ specifically adsorbs ionic surfactants, and their presence strongly affects the zeta potential. In contrast the effect of multivalent inorganic ions on the zeta potential of TeO₂ is rather insignificant (no shift in the IEP). In this respect TeO₂ is very different from metal oxides.     

负载型P-Mo-V/SBA-15催化剂上的甲烷选择氧化反应

以磷钼钒杂多酸(H₅PMo₁₀V₂O₄₀)为前驱体、介孔SBA-15为载体, 采用浸渍法制备不同负载量的P-Mo-V氧化物催化剂. 在甲烷选择氧化反应中, 考察了负载量、反应温度、空速等对甲烷转化率和产物选择性的影响. 结果表明, 催化剂对甲烷选择氧化制甲醛具有较高活性, 甲烷转化率随负载量的增大和反应温度的升高而提高, 甲醛的选择性随负载量的增大先升后降. 反应温度为640 ℃、空速为48300 L•kg^－1•h^－1、氧化物负载量w＝2.89%时, 甲醛的时空产率最高(295 g•kg_cat^－1•h^－1). 多种表征表明, 氧化物负载量w≤2.89%时, P-Mo-V氧化物在载体介孔孔道内以高分散形式存在. 催化剂的酸性和氧化还原性质与负载量相关, NH₃-TPD和H₂-TPR的测试结果表明, 较弱的酸性位和较低还原温度的活性组分有利于甲烷选择氧化制甲醛.     

Heat of formation of Benzophenone Oxide

The heat of formation of benzophenone oxide, Ph₂CO₂, was measured using photoacoustic calorimetry. The enthalpy of the reaction Ph₂CN₂ + O₂ → Ph₂CO₂ + N₂ was found to be ?48.0 ±0.8 kcal mol^?1 and ΔH_f(Ph₂CN₂) was determined by measuring the reaction enthalpy for Ph₂CN₂ + EtOH → Ph₂CHOEt + N₂ (?53.6 ±1.0 kcal mol^?1). Taking ΔH_f(PhCHOEt) = ?10.6 kcal mol^?1 led to ΔH_f(Ph₂CN₂) = 99.2 ± 1.5 kcal mol^?1 and hence to ΔH_f(Ph₂CO₂) = 51.1 ± 2.0 kcal mol^?1. The results imply that the self-reaction of benzophenone oxide i.e., 2Ph₂CO₂ → 2Ph₂CO + O₂ is exothermic by ?76.0 ±4.0 kcal mol^?1.     

钴掺杂的磁性氧化铁纳米粒子的可控合成

通过油酸盐前驱体高温热解法制备出大小均匀的钴掺杂四氧化三铁球形纳米粒子, 其钴/铁摩尔比可以通过调节油酸钴与油酸铁的比例进行调变. 当产物中钴/铁摩尔比从0.024增加到0.156, 所制备的氧化铁纳米粒子的饱和磁矩从39 emu·g^-1逐渐减小到30 emu·g^-1, 而矫顽力从0 Oe升至190 Oe. 在305℃下, 随着反应体系的热解时间由0.5 h 增加到3 h, 所制备出的氧化铁纳米粒子尺寸逐渐由7 nm增加到14 nm. 热解时间较短时, 以高价态的四氧化三铁的晶型为主, 辅之以少量的氧化亚铁; 热解时间增加至2 h, 产物的晶型为四氧化三铁和氧化亚铁的复合物; 而继续增加热解时间至3 h, 除四氧化三铁和氧化亚铁之外, 还出现少量的零价态的CoFe合金, 说明铁(钴)元素经历了由三价到二价, 最后被还原为零价的过程. 随着反应温度的升高, 产物的尺寸逐渐增大, 同时产物中氧化亚铁的含量增多.     

Hydrogen‐Atom Abstraction from Methane by Stoichiometric Vanadium–Silicon Heteronuclear Oxide Cluster Cations

Vanadium–silicon heteronuclear oxide cluster cations were prepared by laser ablation of a V/Si mixed sample in an O₂ background. Reactions of the heteronuclear oxide cations with methane in a fast‐flow reactor were studied with a time‐of‐flight (TOF) mass spectrometer to detect the cluster distribution before and after the reactions. Hydrogen abstraction reactions were identified over stoichiometric cluster cations [(V₂O₅)_n(SiO₂)_m]⁺ (n=1, m=1–4; n=2, m=1), and the estimated first‐order rate constants for the reactions were close to that of the homonuclear oxide cluster V₄O₁₀⁺ with methane. Density functional calculations were performed to study the structural, bonding, electronic, and reactivity properties of these stoichiometric oxide clusters. Terminal‐oxygen‐centered radicals (O_t ^. ) were found in all of the stable isomers. These O_t ^. radicals are active sites of the clusters in reaction with CH₄. The O_t ^. radicals in [V₂O₅(SiO₂)_1–4]⁺ clusters are bonded with Si rather than V atoms. All the hydrogen abstraction reactions are favorable both thermodynamically and kinetically. This work reveals the unique properties of metal/nonmetal heteronuclear oxide clusters, and may provide new insights into CH₄ activation on silica‐supported vanadium oxide catalysts.     

Structure Formation and Conduction of Nanosized Nickel Oxide in Porous Glass

Nickel(II) oxide was deposited on the surface of a porous glass in the amount of 0.5-7.0 mmol g^{- 1} by impregnation of the glass with an aqueous solutions of Ni(NO₃)₂, followed by decomposition of the salt at 673 K. The size features of the formation of the oxide structure were characterized by the data of optical and X-ray photoelectron spectroscopy and by measurements of density and electrical conductivity.     

Hybrid Transition-Metal Oxide and Nitride@N-Doped Reduced Graphene Oxide Electrodes for High-Performance,Flexible, and All-Solid-State Supercapacitors

Nanoscale composites for high-performance electrodes employed in flexible, all-solid-state supercapacitors are being developed. A series of binder-free composites, each consisting of a transition bimetal oxide, a metal oxide, and a metal nitride grown on N-doped reduced graphene oxide (rGO)-wrapped nickel foam are obtained by using a universal strategy. Three different transition metals, Co, Mo, and Fe, are separately compounded with nickel ions, which originate from the nickel foam, to form three composites, NiCoO₂@Co₃O₄@Co₂N, NiMoO₄@MoO₃@Mo₂N, and NiFe₂O₄@Fe₃O₄@Fe₂N, respectively. These as-prepared active materials have similar regular variation patterns in their properties, including better conductivity and battery-mimicking pseudocapacitance, which result in their high whole-electrode capacitance performance [2598.3 F g⁻¹ (39.85 F cm⁻²), 3472.6 F g⁻¹ (41.43 F cm⁻²) and 1907.5 F g⁻¹ (3.41 F cm⁻²) for the composites incorporating Co, Mo, and Fe, respectively]. The as-assembled flexible, all-solid-state NiCoO₂@Co₃O₄@Co₂N//KOH/PVA//NiCoO₂@Co₃O₄@Co₂N device can be easily bent and exhibits high energy density and power density of 92.8 Wh kg⁻¹ and 1670.4 W kg⁻¹, respectively. The universality of this design strategy could allow it to be employed in producing hybrid materials for high-performance energy-storage devices.     

A Laboratory Investigation of the Reduction of Chromium Oxide by a Reverse-Polarity DC Plasma-Driven Molten Oxide Electrolysis Process

A method for producing chromium metal/chromium alloys using a reverse-polarity DC plasma-driven molten oxide electrolysis process was investigated. A laboratory-scale 50 kW DC plasma-crucible system was designed and built to investigate the feasibility of this process. Experiments on molten oxide electrolysis were successfully conducted to produce chromium metal from chromic oxide. Two starting slag systems, SiO₂–CaO–Al₂O₃–Cr₂O₃–Na₂O and SiO₂–CaO–Cr₂O₃–Na₂O, were used in this study. It was found that in each case chromic oxide was successfully reduced to metallic chromium. Aluminum was also reduced with the presence of alumina in the starting slag. Small amounts of carbon monoxide gas were introduced to the electrolysis system to study oxygen evolution rates from the plasma/slag interface. For the SiO₂–CaO–Al₂O₃–Cr₂O₃–Na₂O system, the oxygen evolution rate showed a maximum during the electrolysis process. For the SiO₂–CaO–Cr₂O₃–Na₂O system, the oxygen evolution rates displayed a declining trend with processing time. These two reduction behaviors were apparently controlled by different mechanisms. The significance of this process is that it might be used to produce carbon-free chromium metal/chromium alloys without carbon containing reducing agent and since no carbon based reactants are used for heating or reduction there are no carbon dioxide emissions.     

A Stable Primary Phosphane Oxide and Its Heavier Congeners

(Ferrocenylmethyl)phosphane ( 1 ) oxidation with hydrogen peroxide, elemental sulfur and grey selenium produced (ferrocenylmethyl)phosphane oxide 1O , sulfide 1S and selenide 1Se , respectively, as the first isolable primary phosphane chalcogenides lacking steric protection. At elevated temperatures, compound 1O disproportionated into 1 and (ferrocenylmethyl)phosphinic acid. In reactions with [(η⁶-mes)RuCl₂]₂, 1O underwent tautomerization into a phosphane complex [(η⁶-mes)RuCl₂{FcCH₂PH(OH)-κP}], whereas 1S and 1Se lost their P-bound chalcogen atoms, giving rise to the phosphane complex [(η⁶-mes)RuCl₂(FcCH₂PH₂-κP)] (Fc=ferrocenyl, mes=mesitylene). No tautomerization was observed in the reaction of 1O with B(C₆F₅)₃, which instead produced a Lewis pair FcCH₂P(O)H₂-B(C₆F₅)₃. Phosphane oxide 1O added to C=O bonds of aldehydes and ketones and even to cumulenes PhNCE (E=O and S). However, both PH hydrogens were only employed in the reactions with aldehydes and cyanates.     

Low-Temperature H2 Reduction of Copper Oxide Subnanoparticles

Subnanoparticles (SNPs) with sizes of approximately 1 nm are attractive for enhancing the catalytic performance of transition metals and their oxides. Such SNPs are of particular interest as redox-active catalysts in selective oxidation reactions. However, the electronic states and oxophilicity of copper oxide SNPs are still a subject of debate in terms of their redox properties during oxidation reactions for hydrocarbons. In this work, in situ X-ray absorption fine structure (XAFS) measurements of Cu₂₈O_x SNPs, which were prepared by using a dendritic phenylazomethine template, during temperature-programmed reduction (TPR) with H₂ achieved lowering of the temperature (T₅₀=138 °C) reported thus far for the Cu^II→Cu^I reduction reaction because of Cu−O bond elongation in the ultrasmall copper oxide particles.     

Structural Phase Transitions of a Molecular Metal Oxide

The structural phase of a metal oxide changes with temperature and pressure. During phase transitions, component ions move in multidimensional metal–oxygen networks. Such macroscopic structural events are robust to changes in particle size, even at scales of around 10 nm, and size effects limiting these transitions are particularly important in, for example, high-density memory applications of ferroelectrics. In this study, we examined structural transitions of the molecular metal oxide [Na@(SO₃)₂(n-BuPO₃)₄Mo^V₄Mo^VI₁₄O₄₉]⁵⁻ (Molecule 1 ) at approximately 2 nm by using single-crystal X-ray diffraction analysis. The Na⁺ encapsulated in the discrete metal-oxide anion exhibited a reversible order–disorder transition with distortion of the Mo–O molecular framework induced by temperature. Similar order–disorder transitions were also triggered by chemical pressure induced by removing crystalline solvent molecules in the single-crystal state or by substituting the countercation to change the molecular packing.     

Potential of Supported Copper and Potassium Oxide Catalysts in the Combustion of Carbonaceous Particles

Different oxide carriers (TiO₂ and ZrO₂) as supports for low amounts of Cu²⁺ and K⁺ species (2 wt % as equivalent oxide) were tested in the catalytic oxidation of carbon black. The K-Cu/oxide catalysts were shown to have a lower soot combustion temperature than K/oxide, Cu/oxide, and pure oxide carriers. The K-Cu/ZrO₂ catalyst was found to be the most active; it exhibited activity in a loose contact nearly similar to that obtained in a tight contact mode. Physicochemical characterization by EPR, XPS, and TPR revealed the interaction of K⁺ species with Cu²⁺ species and the ZrO₂ carrier in K-Cu/ZrO₂ as well as a strongly distorted Cu²⁺ species on the ZrO₂ surface. The potassium ions ensure promoting effects towards the contact between the carbon black and the catalyst surface. Although potassium ions were found to lower the reducibility of the cupric oxide species, the oxidation rate of carbon black increased in the presence of K/oxide and K-Cu/oxide.     

Methane Combustion Over Fe, Co and Ni Modified Manganese Oxide Catalysts

Fe-Mn, Co-Mn and Ni-Mn composite oxide catalysts based on high specific surface area MnO₂ precursor were prepared and applied to catalytic combustion of CH₄. Results were compared with that of unmodified MnOx and 1wt.% Pd/-Al₂O₃. Below 450°C, manganese oxide catalysts show higher activity than Pd/-Al₂O₃, while the modified manganese oxide catalysts exhibit higher activity than the unmodified one below 420°C. All catalysts were characterized by means of N₂-BET, XRD, TG-DTA and H₂-TPR. Due to the interaction between Fe, Co or Ni oxides and manganese oxide, the activity of the oxygen species of the modified catalysts is improved, which leads to the increase of their CH₄ combustion activity.     

Titanium Dioxide-Yttrium(III)-Oxide Composite Based Cataluminescence Gas Sensor for Fast Detection of Propylene Oxide

By using nano TiO₂-Y₂O₃ as catalyst, cataluminescence (CTL) phenomenon of propylene oxide (PO) was studied, and it was found that the sensor has high sensitivity and good selectivity for the detection of propylene oxide. The common volatile organic compounds (VOCs) such as acetone, acetaldehyde and benzene show no response to the catalysis of TiO₂-Y₂O₃. Based on this phenomenon, a propylene oxide CTL sensor was designed. The ratio of TiO₂ and Y₂O₃ and the annealed temperatures of the composites were optimized. It was found that when the mass ratio of TiO₂ and Y₂O₃ was 1:3 and the annealed temperature was 500 °C, the catalytic materials showed the best performance. 0.3 L min^?1 of carrier gas flow rate, 490 nm of detection wavelength and 197 °C of working temperature were selected as the optimal working conditions, and under the optimized conditions, the quantitative analysis was performed and CTL intensity was linearly correlated with PO concentration from 4.5 mg L^–1 to 1375 mg L^–1 with a detection limit (3σ) of 1.25 mg L^–1. The sensor was used for quantitative analysis and real-time monitoring of propylene oxide residues in fumigation cereals. The result was consistent with that analyzed by gas chromatography. The CTL sensor proposed here had many merits such as high sensitivity, rapidity and simple operation and had potential application prospects in the rapid detection of propylene oxide in food. At last, the mechanism of catalytic oxidation of PO was discussed as well.     

Preparation and Characterization of Niobium Oxide Coated Cellulose Fiber

The Nb₂O₅/cellulose composite was prepared by reacting α-cellulose with NbCl_5-n(OC₂H₅)_n, in nonaqueous solvent, under nitrogen atmosphere and submitting the obtained material to hydrolysis. An increase in the crystallinity degree is observed in the composite material because the precursor reagent reacts with the amorphous phase of the cellulose fibers. Loadings between 4.5 and 16.0% of the oxide were achieved and in every case the oxide particles uniformly cover the fiber surface. Lewis and Brønsted acid sites were determined by using pyridine as the basic molecular probe.     

Structures of Stoichiometric Sodium Oxide Cluster Cations Studied by Ion Mobility Mass Spectrometry

Structures of stable compositions of sodium oxide cluster cations (Na_nO_m⁺,n≤11) have been investigated by ion mobility mass spectrometry. Stoichiometric compositions series, Na(Na₂O)_(n-1)/2⁺ (n=3, 5, 7, 9, and 11), were observed as stable composition series, and NaO(Na₂O)_(n-1)/2⁺ series (n=5, 7, 9, and 11) were observed as secondary stable series in the mass spectra. To assign the structures of these cluster ion series, collision cross sections between the ions and helium buffer gas were determined experimentally from the ion mobility measurements. Theoretical collision cross sections were also calculated for optimized structures of these compositions. Finally, the structures of Na(Na₂O)_(n-1)/2⁺ and NaO(Na₂O)_(n-1)/2⁺ were assigned to those having similar structural frames for each n except for n=9. All bonds in the assigned structures of Na(Na₂O)_(n-1)/2⁺ were between sodium and oxygen. On the other hand, there was one O-O bond in addition to Na-O bonds in NaO(Na₂O)_(n-1)/2⁺. This result indicates that NaO(Na₂O)_(n-1)/2⁺ have a peroxide ion (O₂^2-) as a substitute for an oxide ion (O^2-) of Na(Na₂O)_(n-1)/2⁺. As a result, both stable series, Na(Na₂O)_(n-1)/2⁺ and NaO(Na₂O)_(n-1)/2⁺, are closed-shell compositions. These closed-shell characteristics have a strong influence on the stability of sodium oxide cluster cations.