Effects of double promoters on direct synthesis of triethoxysilane in gas–solid stirred fluidized bed

The reaction of silicon with ethanol was carried out in a gas–solid stirred fluidized bed, with cuprous chloride prepared by a wet process as the catalyst. The effect of hydrogen fluoride and ethyl chloride addition on formation of triethoxysilane in the direct process was described and discussed. The catalytic activity was evaluated using online gas chromatography, X‐ray diffraction and scanning electron microscopy to study the contact mass. The results show that the promoters hydrogen fluoride and ethyl chloride not only supplemented anions, but also depressed the catalytic activity of metallic copper. The comparison of technical‐grade silicon and polycrystalline silicon showed many differences in reactivity, reaction rate and induction period. Furthermore, the yield, selectivity of triethoxysilane and reaction rate were improved significantly with additions of hydrogen fluoride and ethyl chloride. Copyright © 2011 John Wiley & Sons, Ltd.     

新型CuCl／Hβ沸石羰基化催化剂的制备与原位红外光谱表征

采用固态离子交换法在沸石中直接引进Ｃｕ（Ⅰ）活性中心,ＣｕＣｌ分子在Ｈβ沸石中与Ｈ＾＋交换和在沸石内表面单层分散两个过程同时发生,负载阈值为２１．２％（ＣｕＣｌ％）,调节ＣｕＣｌ和Ｈβ的配比,可得到从桥羟基被部分交换到所有羟基被完全交换的ＣｕＣｌ／Ｈβ从化剂。     

Activation of CuSi and CuZnSnSi contact masses for the direct synthesis of methylchlorosilanes

The temperature-programmed-activation (TPA) of CuSi, CuSi(H) (prepared using CuCl and CuCl 2H2O, respectively), and CuSi copromoted with zinc and tin have been investigated. The main effect of promotion was to increase the activation temperature suggesting that zinc may inhibit the transfer of chlorine from CuCl to surface silicon atoms. The sample prepared using hydrated cuprous chloride initially exhibited reduced activity for the Direct Reaction relative to CuSi, apparently, due to oxidation of the contact mass surface inhibiting the formation of -Cu₃Si.     

An equilibrium ab initio atomistic thermodynamics study of chlorine adsorption on the Cu(001) surface

The effect of chlorine (Cl) chemisorption on the energetics and atomic structure of the Cu(001) surface over a wide range of chlorine pressures and temperatures has been studied using equilibrium ab initio atomistic thermodynamics to elucidate the formation of cuprous chloride (CuCl) as part of the Deacon reaction on copper metal. The calculated surface free energies show that the 1/2 monolayer (ML) c(2 × 2)-Cl phase with chlorine atoms adsorbed at the hollow sites is the most stable structure for a wide range of Cl chemical potential, in agreement with experimental observations. It is also found that at very low pressure and exposure, but elevated temperature, the 1/9 ML and 1/4 ML phases become the most stable. By contrast, a high coverage of Cl does not lead to thermodynamically stable geometries. The subsurface adsorption of Cl atoms, however, dramatically increases the stability of the 1 ML and 2 ML adsorption configurations providing a possible pathway for the formation of the bulk-chloride surface phases in the kinetic regime.     

The direct synthesis of methyldichlorosilane and dimethylchlorosilane

The synthesis of methylchlorosilanes with a siliconhydrogen bond, based on the reaction of silicon and methyl chloride with copper as a catalyst, has been investigated at a temperature of 332°C and a pressure of 1 atmosphere. By adding hydrogen to the gas phase, an overall selectivity of methyldichlorosilane and dimethylchlorosilane of over 80 mol% has been achieved together with a small quantity of by-products. The action of hydrogen consists of a reaction with the CuCl reaction intermediates; reaction of hydrogen with CuCl and silicon or with CuCl and chemisorbed methyl chloride also takes place. Metal chlorides such as CdCl₂ and ZnCl₂, which usually are promoters in the synthesis of methylchlorosilanes, do not promote the formation of the hydrogen-containing products.     

Ethynyl-terminated polysulfones: Synthesis and characterization

Hydroxy-terminated polysulfones (PSs) of number-average molecular weights from 3000 to 26,000 g/mol were converted to the corresponding 4-ethynylbenzoate–terminated PS through a three-step synthesis. The initial step involved the reaction of the hydroxy precursor with 4-bromobenzoyl chloride followed by displacement of the bromo group with trimethylsilylacetylene using a palladium catalyst. The trimethylsilyl group was subsequently cleaved with a weak base to afford the ethynylbenzoate-terminated PS. A more direct route to the ethynylbenzoate-terminated PS involved the reaction of the hydroxy-terminated PS with 4-ethynylbenzoyl chloride. The trimethylsilylethynyl and ethynyl groups undergo a thermally induced reaction to provide modified PS with better solvent resistance and higher apparent glass transition temperatures than an unmodified linear PS. The physical properties of the modified PS are compared with those of a linear PS.     

Photodecarbonylation of dibenzyl ketones and trapping of radical intermediates by copper(II) chloride in frozen aqueous solutions

This paper presents a quantitative and qualitative study of the Norrish type I reaction of dibenzyl ketone (DBK) and 4-methyldibenzyl ketone (MeDBK), producing the benzyl radicals and consequently recombination products, in frozen aqueous solutions over a broad temperature range (-80 to 20 degrees C). This work extends previous research on the cage effects in various constrained media to provide information about the dynamics and reactivity of the photochemically generated intermediates at the grain boundaries of ice matrix. As the temperature of aqueous solutions decreases, the solute concentrations become high at layers covering ice crystals, causing efficient molecular segregation. The cage effect experiments have shown that diffusion of the benzyl radicals within such reaction aggregates is still remarkably efficient at temperatures below -50 degrees C, independently of the initial ketone concentration in the range of 10(-6)-10(-4) mol L(-1). In addition, the study of trapping the benzyl radicals formed in situ by CuCl2 was used as a qualitative probe of heterogeneous bimolecular reactions in the frozen aqueous matrix and on its surface. Molecules of both solutes were found to be segregated from the ice phase to the same location and underwent chemical reactions within diffusion and intermediates lifetimes limits. Understanding the fundamental physicochemical processes in ice is unquestionably important in related environmental or cosmochemical investigations.     

咪唑类化合物-CuCl络合催化剂在甲醇氧化羰基化反应中的催化性能

研究了咪唑及其衍生物配合CuCl对甲醇液相氧化羰化合成碳酸二甲酯的催化性能。筛选出溶解性好、腐蚀性小且催化活性高的多功能助催剂。实验结果表明，反应体系中加入N-甲基咪唑后，CuCl可以完全溶解。当催化剂的浓度为0.2 mol/L, N-甲基咪唑与CuCl的量为4∶1，反应温度为120 ℃，反应压力为2.40 MPa，CO与O2的进气比2∶1，反应3 h的条件下甲醇的摩尔转化率为15.4%，选择性为98%以上。从腐蚀性试验结果看，50 ℃时，加入N-甲基咪唑化合物后，Q235钢在CuCl/CH3OH/H2O/CO/O2体系中的腐蚀速率为0.22mm/a，缓蚀效率为94.5%。动力学研究表明，反应近似为一级，加入N-甲基咪唑后，反应速率常数为0.15 min－1。     

Synthesis of cationic water‐soluble copolymers and hydrogels based on [2‐(methacryloyloxy)ethyl]trimethylammonium chloride and 2‐hydroxyethylacrylate and their complex formation with poly(acrylic acid)

Water‐soluble cationic copolymers and hydrogels were synthesized by radical copolymerization of [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT) and 2‐hydroxyethylacrylate (HEA). The kinetics of copolymerization has been studied and the reactivity ratios were determined. It was found that MADQUAT exhibits higher reactivity in copolymerization. The complexation between linear MADQUAT‐HEA and linear poly(acrylic acid) (PAA) has been studied in aqueous solutions at different pH. It results in the formation of insoluble polyelectrolyte complexes, whose composition and stability to aggregate depends on MADQUAT content in copolymers and pH. The hydrogels were synthesized by three‐dimensional radical copolymerization of MADQUAT and HEA in the presence of a crosslinker. The effects of the feed mixture composition on yield and swelling properties of the hydrogels were studied. The interactions of these hydrogels with linear PAA result in formation of gel–polyelectrolyte complexes and contraction of the samples. It was found that the contraction depends on copolymer composition, PAA molecular weight, and solution pH. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44:845–853, 2006     

ATRP grafting of styrene from benzyl chloride functionalized polysiloxanes: An AFM and TGA study of the Cu(0)/bpy catalyst

Various combinations of Cu(0), CuCl, 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) were used as catalysts for the grafting polymerizations of styrene from polysiloxane macroinitiators functionalized with benzyl chloride. While Cu(0)/bpy alone promotes the grafting, narrower polydispersities were obtained in the presence of CuCl. Analysis of the Cu(0) surface before and after polymerization by a combination of AFM, TGA and FTIR investigations reveals the formation of bpy or phen films on Cu(0). In the presence of CuCl, the ligand film appears decorated with CuCl particles which increase in size with increasing the CuCl concentration. The initial layer occurs most likely as a result of complexation between the ligands and the Cu(0) surface and acts as a support for the rest of the film. These observations are consistent with the film formation on Cu(0) from related nitrogen donors and indicate that the reactivity of the Cu surface may depend not only on its prior treatment but also on the deposition of ligands from the reaction mixture.     

Electrocrystallizations of copper on glassy carbon in CuCl2 silica sol and aqueous solutions

Electrocrystallizations of copper from both CuCl₂ silica sol and aqueous solutions were studied by the chronoamperometry technique.It was found that current density contributions of the double-layer charging（iDL） in current-time transients（CTTs） from both of the solutions were large.An adsorption-nucleation based model was proposed to analyze quantitatively the CTTs,by which copper electrocrystallization mechanism was characterized as progressive nucleation with 3D growth（3DP） under diffusion control.The diffusion coefficient of copper ions and the AN_∞products in aqueous solutions were larger than that in silica sols, which indicated that copper nucleation was inhibited in sol solution.The large iDL may be resulted from the adsorption of chloride ions on the electrode surface.     

氯化亚铜在活性炭载体表面单层分散的密度泛函理论计算

 应用量子化学计算方法研究了活性炭载体表面CuCl活性组分的单层分散行为. 以C16H10,C13H9和C12H12原子簇模型模拟活性炭表面,用密度泛函理论中的B3LYP方法计算得到了CuCl在活性炭表面分散的活性位、稳定构型、相互作用能以及单层分散阈值. 结果表明,CuCl以铜端垂直附着在活性炭表面的顶位和桥位上,相互作用能为76.84～80.79 kJ/mol,单层分散阈值为0.471 g/g. 而XRD测得的单层分散阈值为0.467 g/g,与量子化学计算的结果一致; 按照密置单层模型计算得出的单层分散阈值为0.941 g/g,远大于实验测定结果. 因此,应用量子化学计算方法可以得到活性炭表面活性组分单层分散的丰富信息,并能确定活性组分的单层分散阈值.     

A redox-hydrothermal route to β-MnO2 hollow octahedra

Beta-Manganese dioxides' (β-MnO₂) hollow octahedra have been prepared by a synergetic redox reaction using cuprous chloride (CuCl) and hydrochloric acid (HCl) as reductants and potassium permanganate (KMnO₄) as oxidant through a hydrothermal route. During the process, the self-generated chlorine (Cl₂) gas bubbles and HCl's etching appear to be necessary for the formation of MnO₂ hollow structure. The catalytic efficiency of the prepared β-MnO₂ hollow octahedra was high which has been demonstrated by the catalytic oxidation of methylene blue (MB) dye in the presence of hydrogen peroxide (H₂O₂) under natural light.     

浓度及冷冻鄄解冻处理对CuCl2水溶液中Cu2+区域结构的影响

应用扩展X射线吸收精细结构(EXAFS)光谱研究了CuCl2水溶液中Cu2+的区域环境结构, 通过测定CuCl2水溶液在不同浓度条件下及冷冻-解冻(FT)处理前后Cu K边EXAFS 吸收谱, 研究了浓度及冷冻-解冻处理对Cu2+第一配位层结构的影响. EXAFS实验结果表明, CuCl2水溶液中Cu2+第一配位层距离中心原子Cu最近邻原子为O原子, 配位数介于3.0-4.3之间, Cu—O键长在0.192-0.198 nm 之间, 这种结构与Cu2+的Jahn-Teller效应有关. 不同浓度的CuCl2水溶液中Cu2+的区域环境结构有很大不同, 随着CuCl2水溶液浓度的升高, Cu2+第一配位层配位数减小, Cu—O键伸长. 结构参数拟合结果证实冷冻-解冻处理对Cu2+的区域环境结构有影响, CuCl2溶液经冷冻-解冻处理后, Cu2+第一配位层配位数变大, 热无序度增加.     

Direct electroreduction of solid cuprous chloride to copper powder in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

Direct electroreduction of solid cuprous chloride to prepare copper powder in a “neutral” ambient-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid (BMIMBF₄) was investigated. Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid. Chronoamperometry of the salt powder filled Mo-cavity electrode (current collector) in the ionic liquid further demonstrated the conversion of chloride-to metal inside the cavity, as confirmed by scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction spectra.     

A controllable transformation in copper valence states and its applications

The present study revealed a surprising valence transformation of copper (Cu) in the sintering process of mixtures of copper chloride dihydrate (CuCl(2)·2H(2)O) with β-cyclodextrin (β-CD) in ambient atmosphere. Such a transformation in Cu valence states can be modulated by changing the initial molar ratio (IMR) of CuCl(2)·2H(2)O to β-CD in the mixtures. Firstly, as the value of IMR decreased, the content of cuprous chloride (CuCl) decreased, while the content of cupric oxide (CuO) increased gradually. That is to say, there is an unambiguous IMR-dependence of the contents of CuCl and CuO formed. However, such a controllable valence transformation from Cu(II) to Cu(I) to Cu(II) did not happen in nitrogen atmosphere. Secondly, the in situ composite of CuCl and CuO produced a highly ordered structure of self-assembled nanowires, intertwined, with a diameter of 30 to 50 nm. Furthermore, electronic structural analysis provided direct evidence that the Cu-Cl and Cu-O bonds in this composite material were simultaneously impaired by self-assembled growth. Finally, we noticed that the photoluminescence property of CuCl was regulated through the formation of composites with CuO. In addition, this in situ composite synthesis technique was used to modify the magnetic property of CuO. Furthermore, the anomalous ferromagnetic behaviour of the CuO nanocrystal was observed and explained. In short, this work not only demonstrates a flexible and easily controllable valence transformation of Cu, but also provides a novel approach for constructing inorganic nanocomposite materials. We believe that the implications of these findings are important and make significant contributions to the development of inorganic chemistry and material science.     

Synthesis,crystal structures,and thermal and thermodynamic properties of dimorphic copper(I) coordination polymers

A second modification of the literature-known copper(I) coordination polymer CuCl(pyridazine) was prepared by the reaction of CuCl with pyridazine in acetonitrile. The crystal structure of catena[CuCl(mu(2)-pyridazine-N,N)] is built up of CuCl chains of which each two are connected by the pyridazine ligands to form double chains that are directed parallel to the crystallographic a-axis. In the literature known form LI (CuCl)(2) dimers occur that are connected to chains by the pyridazine ligand. On heating, compound I and LI lose half of the pyridazine ligands and transform to the new 2:1 coordination polymer poly[(CuCl)(2)(pyridazine-N,N)] (II), which transforms at higher temperatures to CuCl. The crystal structure of II is composed of discrete CuCl tetra-chains that are linked by the pyridazine ligands to sheets parallel to (010). The same thermal reactivity is found for the literature-known compound CuBr(pyridazine) (LII), which is isotypic to LI. On heating LII a transformation into the new 2:1 compound poly[(CuBr)(2)(pyridazine-N,N)] (III) is observed, which is isotypic to II. The thermal reactivity of all compounds and the transformation behavior as well as the range of thermodynamic stability of the dimorphic modifications were studied using DTA-TG-MS and DSC measurements, temperature dependent X-ray powder investigations, and crystallization experiments.     

乙烷氧氯化制氯乙烯的研究

氯乙烯单体 ( VCM)是重要的基本化工原料 ,是生产聚氯乙烯的单体 ,其应用十分广泛 .生产VCM的传统方法是以乙烯为原料 ,分步生成目的产物 ,首先通过氧氯化反应生成 1 ,2 -二氯乙烷 ,然后脱氯化氢得到 VCM.由于乙烯法生产氯乙烯工艺复杂、成本较高 ,因此 B.F.Goodrich公司、孟山都公司及比利时的 EVC公司等世界各大化学公司都一直在研究开发乙烷一步法制氯乙烯的技术 ,以此来降低生产成本 .欧洲乙烯公司以乙烷为原料 ,采用直接氧氯化法 ,经过 9年多的开发研究 ,成功地半工业化生产出氯乙烯单体 ,使 VCM生产成本大大降低[1] .原料气乙…     

The Combustion of SiCl4 in Hot O2/H2 Flames

A simple kinetic model describing the molecular gas phase reactions during the formation of fumed silica (AEROSIL®) was developed. The focus was on the formation of molecular SiO₂, starting from SiCl₄, hydrogen and oxygen. Wherever available, kinetic and thermodynamic parameters were taken from the literature. All other parameters are based on quantum chemical calculations. From these data, an adiabatic model for the combustion reaction has been developed. It was found that a significant amount of molecular SiO₂ forms after about 0.1 and 0.6 ms at starting temperatures between 1000 and 2000 K. The initial reaction of the SiCl₄ combustion in a hydrogen/oxygen flame was found to be different from the combustion in air: The high reactivity of SiCl₄ towards water is favored over the SiCl₄ dissociation, which is the initial and rate‐determining step during the combustion of SiCl₄ in air.     

The Barbier-Grignard-type carbonyl alkylation using unactivated alkyl halides in water

The aqueous Barbier-Grignard-type alkylation of aldehydes with unactivated alkyl iodides and bromides was developed. By using a combination of zinc and cuprous iodide, catalyzed by indium(I) chloride, we successfully added tertiary, secondary, and primary alkyl halides to various aromatic aldehydes in 0.07 M aqueous Na2C2O4. A mechanistic rationale for the success of the reaction has been proposed.