Dimerization of Acetylene to Monovinylacetylene (MVA) by Bimetallic Zr/Cu Catalyst in Nieuwland Catalytic System

Nieuwland catalyst is a key step in the dimerization of acetylene. Various zirconium metal additives incorporating Nieuwland catalysts were prepared, and their catalytic performances were assessed in acetylene dimerization. Different characterization techniques (i.e., thermogravimetric analysis, temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen ion concentration measurement and transmission electron microscopy) were employed in this study. The best catalytic performance was obtained over zirconium-acetylacetonate-incorporated Nieuwland catalysts, with an acetylene conversion of 53.3% and a monovinylacetylene selectivity of 87.4%. Based on these results, the zirconium acetylacetonate additive could reduce the types of transition state complexes, and it could also change the morphology of the catalyst. In addition, the additives could significantly inhibit the occurrence of trimerization products and polymers. Hence, the conversion of acetylene, monovinylacetylene selectivity, and stability of the Nieuwland catalysts were enhanced.     

Stability improvement of the Nieuwland catalyst in the dimerization of acetylene to monovinylacetylene

In the process of dimerization of acetylene to produce monovinylacetylene (MVA),the loss of active component CuCl in the Nieuwland catalyst due to the formation of a dark red precipitate was investigated.The formula of the precipitate was CuCl·2C2H2·1/5NH 3,and it was presumed to be formed by the combination of NH 3,C2H2 and [Cu]-acetylene π-complex,which was an intermediate in the dimerization reaction.The addition of hydrochloric acid into the catalyst can reduce the formation of precipitate,whereas excessive H+ is unfavorable to the dimerization reaction of acetylene.To balance between high acetylene conversion and low loss rate of CuCl,the optimum mass percentage of HCl in the added hydrochloric acid was determined.The result showed the optimum mass percentage of HCl decreased from 5.0% to 3.2% when the space velocity of acetylene was from 140 h-1 to 360 h-1.The result in this work also indicated the pH of the Nieuwland catalyst should be kept in the range of 5.80-5.97 during the reaction process,which was good for both catalyst life and acetylene conversion.     

Acetylene coupling on Cu(111): formation of butadiene, benzene, and cyclooctatetraene

Acetylene trimerizes to benzene on the (111) face of copper, as it does on the (100) and (110) planes. However, Cu(111) also yields butadiene and cyclooctatetraene, the latter never previously found with Cu or any other material. No coverage threshold is observed for the onset of these coupling reactions, implying high adsorbate mobility: gaseous benzene is formed by a surface reaction rate-limited process, whereas butadiene and cyclooctatetraene are formed by desorption rate-limited processes. H/D isotope tracing shows that benzene formation proceeds via a statistically random associative mechanism, whereas butadiene formation is associated with strong kinetic isotope effects, probably associated with C-H cleavage. A pericyclic mechanism involving dimerization of C4H4 metallocycles is proposed to account for the formation of cyclooctatetraene. We also found that approximately 45 nm alpha-alumina supported copper particles operated under catalytic conditions at atmospheric pressure yield the same principal reaction products as those found with Cu(111) under vacuum conditions. It therefore seems likely that the elementary reaction steps that describe the surface chemistry of the model system are also important under practical conditions. Comparison of the structure, bonding, and reactivity of acetylene on Cu(111) and Pd(111) indicates that the effectiveness of copper in promoting C-H cleavage in adsorbed acetylene is associated with greater rehybridization of the C-C bond with concomitant weakening of the C-H bond.     

Mechanistic Insights into Copper‐Catalyzed Sonogashira–Hagihara‐Type Cross‐Coupling Reactions: Sub‐Mol % Catalyst Loadings and Ligand Effects

An efficient catalytic system for Sonogashira–Hagihara‐type reactions displaying ligand acceleration in the copper‐catalyzed formation of C(sp²)? C(sp) bonds is described. The structure of the ligand plays a key role for the coupling efficiency. Various copper sources show excellent catalytic activity, even in sub‐mol % quantities. A wide variety of substituents is tolerated in the substrates. Mechanistic details have been revealed by kinetic measurements and DFT calculations.     

Nieuwland's cuprocatalytic reaction in terms of crystal chemical analysis

Crystallochemical treatment of the Nieuwland reaction is carried out on the basis of structural data obtained for crystalline acetylene complexes of the formulas NH₄Cu₈Cl₉·4C₂H₂·1/2HCu₂Cl₃·H₂O (I), NH₄Cu₃Cl₄·C₂H₂ (II), KCu₈Cl₉·4C₂H₂·1/2HCu₂Cl₃·H₂O (III), KCu₃Cl₄·C₂H₂ (IV), (NH₄)₂Cu₃Cl₅·4/9H₂O·(xC₂H₂) with x=0 (Va), 1/9 (Vb), and 4/9 (Vc) and divinylacetylene (DVA) copper chloride compounds 2CuCl·DVA (VI) and 3CuCl·DVA (VII). Because of the π-coordination of a copper atom, the C≡C bond of the acetylene molecule is activated, as indicated by its significant (up to 1.32 Å) stretch (complexes I and II). The zeolite-like structure of complexes Va-Vc, which form in a catalytic solution, is realized as an infinite {[Cu₁₀₈Cl₁₆₈(H₂O)₁₆]^60?}_n anion with discrete [Cl(NH₄)₆]⁵⁺ cations inside. In this structure, only 16 Cu(1) atoms have a trigonal-pyramidal environment with the oxygen atom of the crystallization water located in the vertex (d_Cu?O=2.79 Å). Under the liquid-phase conditions of the Nieuwland reaction, these copper atoms are active centers stimulating the reaction to the subsequent acetylene oligomerization due to the π-interaction with the C₂H₂ molecule. The mutual arrangement of the catalytically active Cu(1) atoms in structure Va serves as a matrix for the synthesis of DVA, as shown by the structure of the 2CuCl·DVA adduct.     

Catalytic carbonyl Z-dienylation via multicomponent reductive coupling of acetylene to aldehydes and alpha-ketoesters mediated by hydrogen: Carbonyl insertion into cationic rhodacyclopentadienes

Exposure of aldehydes or alpha-ketoesters to equal volumes of acetylene and hydrogen gas at ambient temperature and pressure in the presence of cationic rhodium catalysts provides products of carbonyl Z-butadienylation, which arise via multicomponent coupling of four molecules: two molecules of acetylene, a molecule of vicinal dicarbonyl compound, and a molecule of elemental hydrogen. The collective data suggest a catalytic mechanism involving carbonyl insertion into a cationic rhodacyclopentadiene intermediate derived via oxidative dimerization of acetylene. Hydrogenolytic cleavage of the resulting oxarhodacycloheptadiene via formal sigma-bond metathesis provides the product of carbonyl addition and cationic rhodium(I) to close the catalytic cycle. Studies involving the hydrogenation of 1,6-diyne 14a in the presence of alpha-ketoester 6a corroborate the proposed catalytic mechanism. These multicomponent couplings represent the first use of acetylene gas, a basic chemical feedstock, in metal-catalyzed reductive C-C bond formation.     

Double indication in catalytic—kinetic analysis; Determination of iron(III), cyanide and molybdenum(VI)

The reactions in catalytic—kinetic methods are followed simultaneously with two independent indication systems. The information delivered by the two indication methods can be used alone or in combination for the determination of the catalyst or the inhibitor. The following examples illustrate the method: the determination of iron(III) by its catalytic action on the decomposition of hydrogen peroxide (thermometric and biamperometric indication)in the range 10–100 ng Fe/6 ml; the determination of cyanide which inhibits the catalytic activity of copper on the decomposition of hydrogen peroxide thermometric and biamperometric indication) in the range 2–60 μg CN^-/7 ml; and the determination of molybdenum based on the Landolt-type system iodide—bromate— ascorbic acid (thermometric and photometric indication) in the range 0.8–40 μg Mo/8 ml.     

Copper(II) complexes containing pyridine-based and phenolate-based systems: Synthesis,characterization, DFT study,biomimetic catalytic activity of catechol oxidase and phenoxazinone synthase

A template Schiff condensation of 2,6-pyridine dicarbaldehyde or 2,6-diformyl-4- bromophenol and 1,3–diamino-2-hydroxy propane or 3,4-diaminotoluene in the presence of copper(II) salts (CuX₂) (X = Cl, Br, CH₃COO, or ClO₄) affords different types of copper(II) complexes. Depending on the employed molar ratio of the dicarbonyl compounds and diamines, different types of copper(II) complexes formed during the template condensation reaction. Structural formulation of the complexes was confirmed by elemental analysis (C, H, N, and M), physical measurements such as thermal analysis (TAG & DTG), molar conductivity, and magnetic moments in addition to spectral studies (UV–Vis, IR, and ESR). Homobinuclear in a four-coordinate square planar and five-coordinate square pyramidal and trigonal bipyramidal in monomeric structures are proposed. A mononuclear hexa-coordinate in an octahedral geometry is suggested as well. Oxidase biomimetic catalytic activity of these newly synthesized copper(II) complexes was examined toward the aerobic oxidation of 4-tert-butylcatechol (4-TBCH₂) and o-aminophenol under catalytic conditions. Both catalytic and kinetic investigations demonstrate promising oxidase catalytic activity and based on the kinetic results, probable mechanistic catalytic implications are discussed. Geometrical structures of representative copper(II) complexes were determined by optimizing their bond lengths, bond angles, dihedral angles, and the structural index (τ).     

Catalytic Activity Dependency on Catalyst Components in Aerobic Copper–TEMPO Oxidation

The influence of catalyst components in the copper–TEMPO (2,2,6,6‐tetramethylpiperidine N‐oxide) catalysed aerobic oxidation of alcohols was investigated. The type and amount of base greatly influences reactivity. The bipyridyl ligand concentration had no major influence on catalysis, but excessive amounts led to a decrease in activity for longer reaction times. The kinetic dependency for TEMPO was found to be 1.15, and for copper 2.25, which is an indication of a binuclear catalytic system. Optimised conditions with various allylic and aliphatic alcohols give good to excellent rapid oxidations.     

Lewis-Pair-Mediated Selective Dimerization and Polymerization of Lignocellulose-Based β-Angelica Lactone into Biofuel and Acrylic Bioplastic

This contribution reports an unprecedentedly efficient dimerization and the first successful polymerization of lignocellulose-based β-angelica lactone (β-AL) by utilizing a selective Lewis pair (LP) catalytic system, thereby establishing a versatile bio-refinery platform wherein two products, including a dimer for high-quality gasoline-like biofuel (C₈–C₉ branched alkanes, yield=87 %) and a heat- and solvent-resistant acrylic bioplastic (M_n up to 26.0 kg mol⁻¹), can be synthesized from one feedstock by one catalytic system. The underlying reason for exquisite selectivity of the LP catalytic system toward dimerization and polymerization was explored mechanistically.     

Lewis‐Pair‐Mediated Selective Dimerization and Polymerization of Lignocellulose‐Based β‐Angelica Lactone into Biofuel and Acrylic Bioplastic

This contribution reports an unprecedentedly efficient dimerization and the first successful polymerization of lignocellulose‐based β‐angelica lactone (β‐AL) by utilizing a selective Lewis pair (LP) catalytic system, thereby establishing a versatile bio‐refinery platform wherein two products, including a dimer for high‐quality gasoline‐like biofuel (C₈–C₉ branched alkanes, yield=87 %) and a heat‐ and solvent‐resistant acrylic bioplastic (M_n up to 26.0 kg mol^?1), can be synthesized from one feedstock by one catalytic system. The underlying reason for exquisite selectivity of the LP catalytic system toward dimerization and polymerization was explored mechanistically.     

Kinetic determination of traces of copper(ii) by its catalytic effect on the oxidation of 4,4'-dihydroxy-benzophenone thiosemicarbazone by hydrogen peroxide

The kinetic method is based on the catalytic effect of copper(II) on the oxidation of 4,4'-dihydroxybenzophenone thiosemicarbazone by hydrogen peroxide. The reaction is followed spectrophotometrically at 415 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. Three methods of rate measurement are compared. The calibration graphs are linear in the range 10–90 ng Cu ml^-1. There are few interferences. The method is applied to the determination of copper in waters.     

催化动力学光度法测定痕量铜的研究进展

综述了近年来国内外催化动力学光度法测定痕量铜的进展情况。对催化氧化动力学光度法、催化还原动力学光度法、催化荧光光度法、阻抑动力学光度法等几个类别，从反应介质、灵敏度、线性范围等方面介绍了对不同反应体系的研究情况，并对催化动力学光度法测定痕量铜的发展趋势做出预测。     

Reaktionskinetische Untersuchungen der Hydratisierung von Acetylen zu Acetaldehyd an Molekularsieben,die mit katalytisch wirksamen Metall-Ionen beladen sind

The kinetics of the catalytic hydration of acetylene to acetaldehyde in the gas-phase by incorporation of catalytic metal ions on molecular sieves has been studied in a differential reactor. The main product was acetaldehyde besides of small amounts of crotonaldehyde and acetic acid. The catalysts [cadmium(II)-, zinc(II)-, copper(II)- and silver(I)-13 X-molecular sieves] were deactivated at a rate proportional to the square of the hydration rate. The initial hydration rate calculated on the basis of this relation was first order in the acetylene concentration. Starting rate of hydration and rate of deactivation increase with increasing concentration of metal ions on the sieve. The temperature dependence of the rate follows the law of Arrhenius The activation energies of hydration and deactivation, respectively, were calculated. Pore diffusion is a limiting factor. The poison is homogeneously deposited on the catalyst and weakly adsorbed, as it is shown by the criterion of Wheeler. The rate of deactivation decreases with increasing water/acetylene ratio. The deactivation rate which is due to deposition of polymerised acetylene and/or acetaldehyde, is slow with zinc and cadmium catalysts, and more rapid with copper and silver catalysts.     

单原子Cr、Fe和Ni催化乙炔环三聚反应机理研究

应用密度泛函理论(DFT)研究了 Cr、Fe和Ni 3种金属原子催化乙炔环三聚生成苯的反应机理.结果表明,Cr、Fe和Ni催化体系均表现出自旋翻转现象,Cr原子催化乙炔环三聚过程在自旋七重态和五重态势能面上进行,速率控制步骤为形成铬金属七元环;Fe和Ni催化体系的速率控制步骤为两分子乙炔耦合过程.Cr催化体系表现出远高...     

Kinetics of propylene dimerization in the presence of a phosphite-modified, nickel based catalytic system

Propylene dimerization by a catalytic system consisting of nickel(II)acetylacetonate, triphenylphosphite and diethylaluminium chloride has been studied. A kinetic analysis shows a first order dependence on catalyst and a second order dependence on propylene. This revised version was published online in June 2006 with corrections to the Cover Date.     

双功能催化剂体系作用下乙烯二聚和共聚合的研究

用乙烯为原料在双功能催化剂体系的作用下通过二聚和共聚合反应，直接合成线性低密度聚乙烯，所用二聚反应催化剂为钛酸正丁酯，共聚催化剂为ＴｉＣｌ４／ＭｇＣｌ２（ＺＭ－１催化剂）。研究了二聚反应动力学行为及影响双功能催化剂体系动力学过程的一些因素。结果表明利用这两种催化剂组成双功能催化剂体系能够方便地制得密度范围在０．９０－０．９３，Ｅｔ／１０００Ｃ在１０－４０的ＬＬＤＰＥ。     

The Submicrodetermination of Carbon and Hydrogen in organic Compounds by A Gas-Chromatographic Method

Abstract

Preliminary studies on the development of a method for the determination of carbon and hydrogen in 50–100 μg samples of organic compounds are described. The sample is burned over copper oxide in a helium stream and the water formed is converted to acetylene. Separation of CO₂ and acetylene on a silica gel column is followed by combustion of acetylene to carbon dioxide; the two peaks remain separate and are measured by a highly sensitive katharometer.     

Kinetic determination of copper(II) by its catalytic effect on the atmospheric oxidation of 1,3-cyclopentanedione bis(4-methylthiosemicarbazone) monohydrochloride

The kinetic method is based on the catalytic effect of copper(II) on the atmospheric oxidation of 1,3-cyclopentanedione bis(4-methylthiosemicarbazone) monohydrochloride. The reaction is followed spectrophotometrically at 390 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. The calibration graphs are linear in the range 0.05–0.5 μg Cu ml^?1. Interference by other ions is studied.     

双波长双指示剂催化动力学光度法测定食品中的痕量铜

在pH=9.65的NH3-NH4Cl缓冲溶液中,利用Cu2+对H2O2氧化中性红和溴甲酚紫褪色反应具有较强的催化作用,通过测量460nm和590nm波长下催化体系和非催化体系的吸光度,建立了双指示剂、双波长催化动力学光度法测定痕量Cu2+的新方法。方法的线性范围为0.0060～0.072μg/mL,检出限为8.0×10-12g/mL。对Cu2+进行11次平行测定的相对标准偏差为2.9%。方法用于面粉和大米中痕量铜的测定,结果令人满意。