A novel method of the synthesis of molybdovanadophosphoric heteropoly acid solutions

A novel eco-friendly method of the synthesis of aqueous solutions of the Keggintype Mo-V-P heteropoly acids H_3+x PV _x Mo_12−x O₄₀ (HPA-x) is proposed. At the first stage, V₂O₅ is dissolved in cooled H₂O₂ to form peroxyvanadic compounds, which spontaneously decompose to yield a H₆V₁₀O₂₈ solution. The latter is stabilized by the addition of H₃PO₄ to yield a H₉PV₁₄O₄₂ solution that is added to a boiling aqueous suspension of (H₃PO₄ + MoO₃). This suspension is gradually evaporated producing the HPA-x solution. This safe and practically wasteless method holds much promise for the preparation of HPA-x solutions with x = 2–6.     

Synthesis of N-substituted amides by the Ritter reaction with heteropoly acids as catalysts

Reactions of a number of nitriles with camphene in the presence of the heteropoly acids H₃PW₁₂O₄₀, H₇PMo₁₂O₄₂, and H₄SiW₁₂O₄₀ as catalysts were studied. In all cases, N-substituted amides were obtained in sufficiently high yields. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 374–376, February, 2006.     

Stability of palladium in homogeneous chloride-free catalysts Pd + heteropoly acid for oxidation of C2-C4 alkenes by dioxygen

A possibility of the use of polycarboxylic acids as stabilizers of Pd in homogeneous catalysts for the oxidation of C₂–C₄ alkenes is studied. Pyromellitic acid is shown to have the stabilizing properties.     

Epoxidation of cycloolefins with hydrogen peroxide in the presence of heteropoly acids combined with phase transfer catalyst

Oxidation of cycloolefins (cyclohexene, cyclooctene, and cyclododecene) with a 30% solution of hydrogen peroxide at 65 °C in the presence of heteropoly acids (HPA) H₃PW_12–x Mo _x O₄₀ (x = 0—12), which are precursors of active peroxo complexes, and phase transfer catalysts Q⁺Cl^–, where Q⁺ is the quaternary ammonium cation containing C₄—C₁₈ alkyl groups or [C₅H₅NC₁₆H₃₃]⁺, was studied. The catalytic activity decreases in the HPA series: H₃PW₁₂O₄₀ > H₃PW₉Mo₃O₄₀ > H₃PW₆Mo₆O₄₀ > H₃PW₃Mo₉O₄₀ > H₃PMo₁₂O₄₀. The state of the H₃PW₁₂O₄₀—I₂I₂ system was studied using UV, IR, and ³¹P NMR spectroscopies with variation of the [H₂O₂] : [HPA] ratio from 2 to 200 during cyclohexene epoxidation. Despite different catalytic precursors, the reaction proceeds through the same peroxo complex.     

Acidity of heteropoly acids with various structures and compositions studied by IR spectroscopy of the pyridinium salts

The acidity on the proton affinity scale was determined by IR spectroscopy of the pyridinium salts for nineteen heteropoly acids of nine structural types (including two with the previously unknown structure) and one isopoly acid. All heteropoly acids exhibited a high acidity at the level of CF₃SO₃H and HClO₄. H₃PW₁₂O₄₀ was the strongest acid.     

Thermodynamic parameters for the protonation of carboxylic acids in aqueous tetraethylammonium iodide solutions

The protonation constants of 21 carboxylic acids (formic, acetic, propionic, benzoic, phenoxyacetic, salicylic, oxalic, malonic, succinic, itaconic, malic, tartaric, oxydiacetic, thiodiacetic, thiodipropionic, phthalic, maleic, citric, 1,2,3-tricarboxylic, 1,2,4-tricarboxylic and 1,2,4,5-tetracarboxylic), have been determined potentiometrically, by pH-metric measurements, at several temperatures and ionic strengths, 5T55°C, 0<11 mol-dm^–3, using tetraethylammonium iodide as background salt. General equations for the dependence on ionic strength of thermodynamic parameters have been found. The statistical significance of results and the possibility of using a simple model for the thermodynamics of carboxylic acids protonation, is discussed.     

Complexation properties of phosphonocarboxylic acids in aqueous solutions

The concentration formation constants of phosphonoacetic acid (PAA) complexes with the Ca²⁺ and Mg²⁺ ions were determined in aqueous solution at 25°C by potentiometric and coulometric titrations at different ionic strengths and were extrapolated to I=0 in order to obtain thermodynamic values of the formation constants. Complexes were formed by the completely deprotonated K _f (ML) and monoprotonated K _f (MHL) forms of the PAA anion. The respective values for the complexes are: log K _f (CaL)=4.68±0.03, log K _f (CaHL)=2.61±0.08; log K _f (MgL)=5.58±0.09, log K _f (MgHL)=3.0±0.3. The enthalpy and entropy of complexation for the deprotonated Ca²⁺ and Mg²⁺ PAA species, determined from the temperature dependence of the log K _f (ML), are: H⁰(Ca) =0.6±0.2 kcal-mol^–1, S⁰(Ca)=21.4±0.6 cal-mol^–1-K^–1, H⁰(Mg)=3.0±0.7 kcal-mol^–1, and S⁰(Mg)=35±2 cal-mol^–1-K^–1. It is seen there-fore, that the complexes are entropy stabilized but enthalpy destabilized. Formation constants were also determined for Ca²⁺ and Mg²⁺ complexes with PAA analogs, phosphonoformic and 3-phosphonopropionic acids and the complexation of PAA was also studied at a single ionic strength, with Na⁺, Ag⁺, Tl⁺, Sr²⁺, Ba²⁺, Cd²⁺, Cu²⁺, and Pb²⁺ ions.     

Association of carboxylic acids in aqueous solutions from conductivity data

Using precision conductivity data for aqueous carboxylic acid systems at 25 and 30°C, accurate thermodynamic ion association and dimerization equilibrium constants were determined. The data for formic, acetic, propionic and butyric acids are analyzed with the Fuoss-Hsia conductance equation as modified by Justice and Barthel. The treatment requires that triple ion formation is negligible.     

Structural properties of dilute aqueous solutions of dimethylformamide and acetone based on computer simulation

The Monte Carlo simulation of molecular configurations for aqueous solutions ofN,N-dimethylformamide and acetone was carried out. The atom-atom radial distribution functions were determined. The topological properties of the H-bond system were investigated. The concentrations of closed H-bond cycles and the radial distribution functions of their geometric centers were found. It was shown that the local arrangement of molecules and supermolecular assemblies typical of the H-bond network in neat water is retained in the solutions studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 592–599, April, 1998.     

Enthalpic interactions of -alanine and -serine in aqueous urea solutions

The enthalpies of dilution of -alanine and -serine in various aqueous urea solutions have been determined by flow microcalorimetry at 298.15 K. The homogeneous enthalpic interaction coefficients over the whole range of aqueous urea solutions have been calculated according to the excess enthalpy concept. The results were interpreted from the point of view of solute–solute interactions moderated by solvent effects.     

Kinetics of oxidation of butene-1 to butanone in aqueous solution in the presence of ions Pd2+ and Mo-V-phosphoric heteropoly acid

Oxidation of butene-1 to butanone in the presence of homogeneous catalysts (PdSO₄ + HPA-x), where HPA-x = H_3+xPV_xMo_12-xO₄₀, 1 ￡ x ￡ 4, was investigated. This reaction is found to be of the 1st order with respect to C₄H₈, and of the 0.64th order with respect to Pd. The reaction rate does not depend on the HPA-x concentration and pH of the solution. The activation energy of the reaction is variable. A kinetic expression of the reaction is obtained for 303-343 K. This revised version was published online in June 2006 with corrections to the Cover Date.     

On the properties of surfactant aqueous solutions

Summary From studies of aqueous solutions of dodecylammoniumnitrate an association mechanism has been proposed involving multiequilibrium. In the concentration range considered we can differentiate between two aspects: ranges of marked qualitative and quantitative changes and formation of differently structured surfactant species.

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Zusammenfassung Aus der Untersuchung wäßriger Lösungen von Dodecylammoniumnitrat würde ein Assoziationsmechanismus abgeleitet, welcher ein Multiequilibrium beinhaltet. Im untersuchten Konzentrationsbereich können zwei Bereiche unterschieden werden: Bereiche mit ausgeprägten qualitativen und quantitativen Änderungen und Bereiche mit der Bildung von verschieden strukturierten oberflächenaktiven Spezies.

     

Transport properties of alkyltrimethylammonium bromide surfactants in aqueous solutions

Differential mutual diffusion coefficients of n-alkyltrimethylammonium bromides [CH₃(CH₂)_n–1N(CH₃)₃Br, C_nTAB] (n=10, 12, 14, 16) have been measured in aqueous solutions at 298.15 K using a conductimetric cell and an automatic apparatus to follow diffusion. The cell is based on an open-ended capillary, and the technique follows the diffusion process by measuring the resistance of a solution inside the capillaries at various times. The electrical conductances of those solutions have also been measured to calculate the critical micellar concentration (cmc). Thermodynamic analysis of the data suggests that the free ion concentration decreases at concentrations above the cmc, in agreement with theoretical predictions. The obtained values of the micellization parameters were used to model the mutual diffusion coefficients of C_nTAB aqueous solutions.     

Enthalpic interaction between α-amino acids and pyridine and methylpyridine in aqueous solutions

Enthalpies of dilution of aqueous L-serine, pyridine and methylpyridine solutions and their enthalpies of mixing have been determined by a mixing-flow microcalorimeter at 298.15 K. The data have been analyzed in terms of McMillan-Mayer formalism to fit to virial polynomials from which the heterotactic enthalpic pairwise interaction coefficients, h _xy, betweenL-serine and pyridine and methylpyridine isomers have been evaluated. The results obtained in the present paper are compared with those reported in the earlier paper about glycine and L-alanine in the same organic solvent aqueous solutions, giving a global insight of the interaction mechanism between the a-amino acids and pyridine and methylpyridine from the point of view of solute-solute interactions and substituent effects of methyl groups introduced into the pyridine ring. This revised version was published online in July 2006 with corrections to the Cover Date.     

钨、钼、镍含量的改变对体相催化剂物化性质、加氢活性影响

制备不同活性金属原子比的体相催化剂,通过BET、XRD、SEM、TEM、强度测定、堆积密度测定及小型活性评价手段,考察了活性金属钨、钼、镍含量的变化对体相催化剂物化性质和活性的影响。结果表明,保持W/Mo原子比不变,随着(W+Mo)/Ni的原子比减小,孔体积、比表面积、孔径增大,超深度加氢脱硫活性增强,在精制油硫含量小于10μg/g,反应温度降低8℃。在(W+Mo)/Ni的原子比不变的条件下,W/Mo的原子比在0.28-1.85,随着原子比增大,孔体积、比表面积、超深度加氢脱硫活性没有明显变化。     

杂多酸催化剂及其在精细化学品合成中的应用

详细介绍了环境友好的杂多化合物的结构、性能、制备、表征及其在精细化学品合成中的应用最新进展,并对负载型杂多酸和新颖的混合型杂多酸及其盐催化剂的合成及应用进行综述.认为杂多化合物的深入研究具有十分重要的理论价值和现实意义.杂多酸及盐作为绿色催化剂在精细化学品合成中具有广阔的应用前景.     

Thermodynamic parameters of solvation of nonelectrolytes in aqueous solutions of amides of carboxylic acids

Interaction and reorganization contributions to solvation enthalpies of nonelectrolytes in aqueous solutions of amides of carboxylic acids with different degree of N-substitution and N-methylpyrrolidone are calculated. The data are discussed using structurally thermodynamic characteristics of water-amide systems obtained by us previously. It is found that the type of concentration dependence of the solvation enthalpy of nonelectrolytes in all solutions investigated is determined by the type of reorganization component. It is shown that the highest solvation exothermicity of nonelectrolytes in water is due to the lowest value of the reorganization contribution in spite of that nonelectrolytes interact weaker with water than with non aqueous components.     

The aromatic amino acid behaviour in aqueous amide solutions

The enthalpies of solution of L-phenylalanine in the mixtures of water with the protein denaturant urea have been measured in the temperature range of 288.15–318.15 K. Using the results of the present research and literature data of free energies, the standard thermodynamic functions of the solute transfer from water to aqueous urea solutions have been estimated in a wide temperature range. The enthalpic, heat capacity, entropic and free energy parameters of the solute-urea pair and triplet interactions have been computed. The amino acid — amide pair interaction was found to be attractive in the temperature range studied due to the favourable enthalpic term. The triplet interaction being slightly repulsive reveals the enthalpic origin also. The examination of the Savage and Wood additivity-of-groups approach does indicate the inapplicability of this scheme to enthalpies and entropies of interaction. It has been found for the first time that the heat capacity of interaction changes its sign at 303 K, i.e. the temperature dependence of enthalpic and entropic parameters passes through the pronounced extrema near the temperature of the minimum of the heat capacity of pure water.     

均相催化剂催化合成碳酸亚丙酯

分别就单组为催化剂和双组分催化剂对二氧化碳与环氧丙烷合成碳酸亚丙酯的催化活性进行了研究。实验结果表明，在单组分催化体系中，相转移催化剂，如十六烷基三甲基漠化按、四丁基演化铵对上述酯化反应具有较高的催化活性此外，盐酸羟胺、三苯基磷也有一定的催化活性；在双组分催化体系中，KI／PEG（聚乙二醇）体系具有很高的催化活性，能在较短时间内、较低的压力下高产率地得到碳酸亚丙酯，而某些金属盐、有机碱、季接盐的适当红合，也能有效地催化该反应。