Voprosy khimii i khimicheskoi tekhnologii (Issues of Chemistry and Chemical Technology)

10-18

Authors: A.I. Gladii, F.I. Tsiupko, Y.Y. Yatchyshyn, I.P. Polyuzhyn, M.M. Laruk

Polycarboxylates based on maleic monomers with a distant carboxylic group are applied as hyper plasticizers for concrete and demulsifiers for oil-water emulsions; they have rust-resisting properties too. These maleic monomers have two unsaturated bonds with different reactivity in addition to the distant carboxylic group. In the present communication, the kinetics of the non-catalytic and catalytic acylation of hydroxyethylmethacrylate and hydroxyhexapropylenoxyacrylate by maleic anhydride has been studied by means of acid number determination using conductometric titration. The experimental data are well described by the kinetic model of irreversible second-order reaction. The studies were conducted without solvents at a 10% molar excess of hydroxypolyalkylenoxy(meth)acrylate and at a concentration of triethylamine as a catalyst within the range from 0 to 4 mol. % of the initial concentration of maleic anhydride that is suitable for the implementation of an industrial process. The optimal conditions for the synthesis of two monomers are as follows: the temperature is 363 К or 353 К, the reaction time is 0.5 or 2 hours at catalyst concentration of 4 mol. % of the initial concentration of maleic anhydride. A kinetic compensation effect was observed for the activation energies and pre-exponential factors calculated by the Arrhenius equation. The structures of the purified synthesized monomers have been confirmed by refractometric method and IR spectroscopy.

23-37

Authors: T.V. Luk'yanenko, O.В. Shmychkova, A.B. Velichenko

The presence of ionic dopants in the electrolyte inhibits the process of PbO2 electrodeposition in the kinetic region due to adsorption of ionic additives on the growing oxide surface. In this case, the addition of fluoride ions increases the deposition current in the diffusion region by increasing the contribution of migration component. The ion-doped oxide forms in the presence of additives in the electrolyte. The content of additives in the deposit varies between 0.2 to 4.2% (wt.) depending on the additive nature, its concentration and deposition conditions. Lead dioxide deposited from methanesulfonate electrolytes at room temperature is a mixture of α- and β-phases, and the content of the latter does not exceed 4.2% wt. Temperature growth and the addition of doping ions in the electrolytes lead to an increase in the β-phase content in the coating. Increasing the deposition potential and decreasing the electrolyte's pH lead to the growth of crystals size and the appearance of priorities in the crystallographic orientation. The content of crystals with orthorhombic lattice is proportional to the charge consumed in the formation of two-dimensional nuclei.

45-49

Authors: T.P. Rebrova, V.L. Cherginets

Europium dihalides are used as dopants in optical luminescent crystals grown from molten media. Oxygen-containing admixtures existing in the melt react with Eu2+ cation that can result in oxide precipitation and loss of the activator. To estimate the possibility of running similar processes the data on solubility and dissociation of EuO in halide melts are necessary. It is of interest to trace the effect of halide melt composition on oxide solubilities. Solubility product (6.3∙10-9 mol2∙kg-2) and dissociation constant (6.0∙10-6 mol∙kg-1) of EuO in molten NaBr-NaI (0.8:0.2) mixture are determined by a potentiometric titration method with the use of membrane oxygen electrode. Total concentration of ionic (Eu2++O2 ) and undissociated (EuO) forms in the saturated solution is equal to 1.15∙10-3 mol∙kg-1. In comparison with NaI melt, the concentrations of Eu2+ and O2 in the saturated solution increase by 25 per cent whereas the concentration of undissociated EuO and the total content of europium in the saturated solution of EuO decrease by 30 per cent. An increase in the dissociation degree of europium monoxide in bromide-iodide melt as compared with the iodide can be explained by the presence of harder base (bromide) in the former melt. The reduction of EuO concentration in the mixed melt is explained by a decrease in the melt of a number of holes appropriate for EuO by size as compared with the pure iodide.

55-62

Authors: V.D. Barsky, G.A.Vlasov, А.А. Pivovarov, A.V. Kravchenko

With the use of the model of metamorphism dynamics, the authors theoretically and experimentally show the "leaps" of metamorphic restructuring of fuel, and determine the character of changes in the ratio between chemical bonds of different nature. The report provides, on this basis, generalized concept according to which the dynamics of intermolecular binding in solid fuel is determined by outrunning reduction of the role of EDA-interactions and hydrogen bonds. Minimum strength of supramolecular structure arising in connection with it falls on the stage of coking coals. Models of averaged "molecules" of solid fuel are offered which characterize its chemical composition during the periods of revealed "leaps" of metamorphism. Adequacy of these models is confirmed by stoichiometric equations of reactions behavior, material balances of stages and compatibility of combustion values of model substances and coals of close elemental composition. Basic provisions of the developed theory on chemistry of the process of metamorphism were used in estimation of the chemical potential of coals, as well as during comparative assessment of primary reserves of coal, oil and gas: 87.05%, 4.92% and 8.03% (mass percent), accordingly, which differs significantly from data published earlier (95% of coal and 5% of oil and gas).

66-72

Authors: T.L. Rakitskaya, T.A. Kiose, K.O. Goludchik, L.P. Oleksenko, R.M. Dlubovskii

Natural clinoptilolite (Sokirnitsa, Transcarpathian region, Ukraine, hereinafter called as N-CLI) was thermally (by heating at 300 C, hereinafter called as 300-CLI) and hydrothermally (by boiling in distilled water, hereinafter called as H2O-CLI) activated. The modified and natural samples of clinoptilolite were further used as supports (S) for obtaining K2PdCl4-Cu(NO3)2-KBrS systems by impregnation of each support with the mixed aqueous solution of these compounds at their certain ratio followed by drying at 110 C till constant weight. The systems anchored were tested as catalysts for the reaction of low-temperature carbon monoxide oxidation. The comparison of the catalytic activities of these systems with the supporst properties characterized by X-ray phase analysis, IR spectroscopy, thermogravimetric analysis, and ad/desorption of water vapor showed that the modification of clinoptilolite was resulted in slight changes in its structure without any damage of its framework. Evidently, a dramatic improvement in the catalytic behavior of K2PdCl4-Cu(NO3)2-KBr300-CLI system was due to the significant increment (actually, twice) in 300-CLI surface area compared with N-CLI and H2O-CLI as a result of the complete zeolite water removal. It was accompanied by the heightening in a number of accessible Al(ОН)Si and Si-O-Al structural fragments which were the sites of formation of catalytically active surface palladium-copper complexes.

79-85

Authors: U.V. Khromyak

In this work, we synthesized copolymers of polyvinylpyrrolidone with methyl methacrylate by means of emulsion polymerization. The formation of graft copolymers of polyvinylpyrrolidone is confirmed on the basis of IR-spectroscopic studies. The nature of monomer, concentration and temperature significantly affect the effectiveness and the degree of grafting. The synthesized copolymers have been used as polyvinylpyrrolidone polymer matrixes to produce methyl methacrylate–copolymer compositions which are cured by the block polymerization. The polymerization of methyl methacrylate occurs with at a high speed, and the degree of monomer conversion reaches 65 to 95% for 10 to 15 minutes depending on the ratio of the components. The highest rate of polymerization and the maximum degree of conversion are observed if the ratio between the polymer matrix and methyl methacrylate is equal to 2:1. The obtained materials are distinguished by enhanced performance properties such as hardness, heat resistance, adhesion to various substrates, water absorption, and chemical resistance in acidic and alkaline media.