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

4-11

Authors: M.V. Ved, N.D. Sakhnenko, M.A. Glushkova, Yu.K. Hapon, M.A. Kozyar

The electrodeposition of Co-Mo-W and Co-Mo-Zr coatings from a polyligand citrate-pyrophosphate bath was investigated. The effects of both current density amplitude and pulse on/off time on the quality, composition and surface topography of the electrodeposited alloys were determined. It was established that the content of alloying components in Co-Mo-Zr coatings increases with an increase in the current density. The content of zirconium was shown to increase with the on-time. The content of molybdenum grows with the off-time. This is because the chemical reduction of their intermediate oxides by hydrogen ad-atoms. It was stated that the dependences of the refractory metals content in the Co-Mo-W coating upon both current density and on/off times have an extremal character; a maximum content of Mo and W corresponds to the current density range of 12 to 18 A•dm−2 and to the on/off-times of 5 to 10 ms. The Co-Mo-W alloys exhibit a high catalytic activity towards the hydrogen evolution reaction in acidic media, this catalytic activity is comparable to that of a platinum electrode. The electrodeposited Co-Mo-Zr alloys with a zirconium content of 1.5 to 2.0% wt show a high catalytic activity towards the reaction of carbon oxide (II) oxidation. This confirms the efficiency of such materials as catalysts for the purification of gaseous wastes and allows us to recommend them as catalysts for hydrocarbons combustion.

17-23

Authors: I.V. Kirsanova, R.D. Apostolova

The influence of temperature on the impedance spectra of electrodeposited Mo2S3 on aluminium, which was discharged in Li accumulator in contact with an electrolyte, has been analyzed in this work. The changes of such parameters as ohmic resistance (R), diffusion impedance (W), and constant phase element (CPE) were evaluated and discussed, those parameters determining the energy of the charge and mass transfer. The impedance behaviour related with the fractality of the electrode surface has been determined as a temperature function. It has been established that ensuring an effective transformation of Mo2S3 in lithium accumulator containing 1 М LiClO4, PC, and DME as electrolyte may be provided at the temperatures of 298 to 307 К.

29-34

Authors: S.A. Korniy

A quantum-chemical model is proposed to study poisoning of platinum binary nanoclusters Pt42X13 (where X is a transition metal Fe, Co, Ni) of the core–shell structure by carbon monoxide in the environment of low temperature fuel cells. The model is based on adsorption behaviors of CO molecule with the nanocluster surfaces and allows us to establish ability of these nanoclusters to form strong chemosorption bonds with CO molecules as a function of cluster core nature and adsorption sites. In frames of quantum-chemical method of density functional theory (DFT), regularities were found for the influence of binary nanocluster cores of Fe, Co, and Ni on the geometry and energy behaviors of CO adsorption. The obtained data allowed us to propose the mechanism of CO interaction with platinum binary nanoclusters. The mechanism is based either on electronic properties alteration for surface platinum atoms or on the distribution of active adsorption centers of the surface as a function of core nature. Our results confirm the perspectives of DFT use in the theoretical estimation of chemical composition and structure of effective platinum binary nanoclusters for their exploitation in catalytic reactions of low temperature fuel cells.

42-46

Authors: R.E. Khoma

The results of pH, redox and conductivity studies of sulfur dioxide chemisorption by aqueous solutions containing some N-alkylated derivatives of monoethanolamine (MEA) (N,N-dimethyl- (DMMEA), N,N-diethyl- (DEMEA) and N-aminoethylmonoetanolamine (AEMEA)) and morpholine (MP) are described. The measurements are conducted at 293 K in order to determine the composition and relative stability of the interaction products. This reaction is accompanied by a formation of a sulfite, bisulfite and pyrosulfite of monoethanolammonium and morpholinium cations. The observed deviation of the position of the extreme in the differential pH-metric titration curves (as well as the mid jump in integral ones) from the expected strict stoichiometry is due to the simultaneous formation of a few products as a result of hydrolytic transformations and changes in an ionic strength caused by reaching an equilibrium "hydrosulfite–pyrosulphite". The N,N-dialkylation of MEA or its insertion into a cyclic compound (MP) are shown to reduce the absorbency of the prepared compounds in respect to SO2. "Onium" sulfites stability correlates with the ligand (i.e. MEA derivatives) basicity. The relative stability of ethanolammonium sulphites in aqueous solutions may be ranged as follows: DEMEA > AEMEA > DMMEA > MP. This range is transformed into MP > DMMEA > DEMEA for hydrosulfites. The use of pH, redox and conductivity measurements data, which are mutually complementary, allows obtaining consistent and objective information on the "onium" compounds formed in the systems "SO2 – Am – H2O". The results obtained can be used in the development of methods for sanitary air cleaning from SO2.

52-55

Authors: V.A. Golovenko, N.L. Gurevina, L.A. Snezhko

The method of recycling of fat wastes is improved in this work by their transesterification into the fatty acid methyl esters. The fats wastes of meat-packing plants were used for the synthesis of fatty acid methyl esters. The amount of such fats arrives 20 tons a day in Dnepropetrovsk's region. The contents of moisture and free fat acids were determined in raw material, they being characterized by acid number. For the determination of fatty acid methyl esters output, the amount of fats in wastes was also determined, which is characterized by the saponification number. The production of esters from fat was studied by varying the ratio "fat:alcohol (methanol)" in the range of 1:3 to 1:27. The reaction time reached 3 hours. The effect of temperature on the reaction was studied in the range from room temperature to boiling point of the reaction mass (i.e. 27-70 0C). To accelerate the process of transesterification, a homogeneous alkaline catalyst KOH was used. The amount of potassium hydroxide was varied in the range of 0.5 to 2 wt. % on the fat weight taking into account the acid number of the fat. The synthesized fatty acid methyl esters meet the requirements of the national standard of Ukraine (DSTU 6081:2009) as concerns the characteristics under study. At the same time, they was characterised by a low content of free fatty acids and unsaturated fatty acids methyl esters. An enhanced content of water in esters may be explained by increased water content in raw material. Keywords: transesterification; waste fat; methyl esters; fatty acid.

63-71

Authors: Y.V. Kalashnykov, N.V. Nikolenko, A.S. Kachalova, A.V. Dubenko, A.M. Abramova

A possible ways to increase the leaching rate of the altered ilmenite ore by preliminary crushing and ultrasonic treatment are considered. During the grinding of initial ilmenite ore the contents of pseudorutile and ilmenite phases diminish constantly whereas the content of rutile phase increases and pseudobrookite phase appears. It is concluded that the preliminary crushing of ilmenite ore results in two effects as follows: (i) increasing the rate of ore leaching in sulfuric acid, and (ii) reducing the utilization degree of raw materials; this is because of increasing amounts of insoluble rutile phase. It is stated for the first time that ultrasound with intensity of 0.4 W/cm2 reduces the leaching degree of titanium while the corresponding kinetic curves have a convex shape passing through a maximum. The investigation of the leaching process shows that the first stage of the process (i.e. before the solidification) proceeds in kinetic mode and the second stage (i.e. after the solidification of the reaction mixture) occurs in external diffusion mode. To intensify the leaching process of the altered Malyshevsky ilmenite ore, we propose to reduce the concentration of sulfuric acid up to 85%.

75-78

Authors: А. Saley, A. Sigunov, T. Kravchenko, L. Khmarska

In the present work we investigated the effect of the dispersion of raw mix components on the construction properties of lightweight concrete. Such concrete is often used in the manufacture of gas concrete using the wastes of Pridneprovsk region companies, including granulated blast-furnace slag and flue ash of thermal power plants. The compositions of cellular concrete with different components dispersity were formed and an analysis was made to determine the rational values of the fineness of grinding of the components in the raw mix. The formation of a defined fraction of individual materials was established to occur according to an individual scheme. Thus, the specific surface area of fine fractions (less than 0.14 mm) increases in the following range: sand, cement, granulated blast furnace slag, and lime. However, for crude fractions, this sequence is as follows: sand, granulated blast furnace slag, cement, and lime. In order to optimize the characteristics of dispersed raw mix, a simplex-lattice method of experiment planning was used. The research results showed that the main construction and technical characteristics of cellular concrete are mainly associated with the values of the fineness of grinding of each component of the composition. The analysis of the results revealed that a grinding of lime and fillers to the dispersity of at least 250 m2/kg is satisfactory from the point of view of the formation of required densities and strengths for the developed heat-insulating and structural heat-insulating gas concrete products.

86-90

Authors: E.V. Smyrnova, N.D. Koshel, N.A. Gladchenko, S.V. Korpach

A simple mathematical model of processes occurring on iron-oxide electrodes at charge-discharge cycling is described. It is intended to treat and analyse experimental current-voltage characteristics. A spherical elementary fragment is considered for the description of processes in the active mass with a defined radius. The spherical solid-phase elements of four phases, namely, two forms of hydroxides, electron-conductive agent and metal, are situated in a filling electrolyte within the elementary fragment. The simulation data show that the second anodic peak in the potentials range of –0.6 V to –0.5 V is a superposition of the reaction peaks Fe0 ↔ Fe(OH)2 and Fe(OH)2 ↔ Fe(OH)3. In the course of potential sweep towards more positive values, the reaction HFeO2- + H2O ↔ Fe(OH)2 begins which consumes HFeO2-ions; this results in a decrease in their content which approached to the saturation point. This causes the appearance of a second wave of reaction Fe0 ↔ Fe(OH)2.

95-102

Authors: К.М. Sukhyy, Y.P. Gomza, E.А. Belyanovskaya, V.V. Klepko, O.A. Shilova, М.P. Sukhyy, A.V. Gavrilko

The technological principles for the process control of the sol-gel synthesis of a new class of organic-inorganic nanostructured materials on the basis of tetraethoxysilane and polyionenes doped by orthophosphoric acid are developed in this work. The chemical compositions improvement is based on the results of complex investigation of morphology, physical and chemical properties. The rate of hydrolytical polycondensation reaction of tetraethoxysilane increases with the addition of polyionenes. The gelling rate increases with polyionene molecular weight. The polyionenes in silicophosphate sols are revealed to prevent crystallization processes which occur in silicophosphate xerogels with silica phosphates and pyrophosphates; this hinders the transport processes. The hybrid organic-inorganic silicophosphates doped by polyionenes exhibit higher proton conductivity than that of the initial nanocomposites. This influence may be improved by the ultrasonic treatment of the sol.