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Vol 13, No 4 (2018)
View or download the full issue PDF (Russian)
https://doi.org/10.32362/2410-6593-2018-13-4

ANALYTICAL METHODS IN CHEMISTRY AND CHEMICAL TECHNOLOGY

5-16 190
Abstract
Voltammetric responses associated with the simple reaction of perrhenate anions transfer across polarized micro-interfaces between two immiscible electrolyte solutions (micro-ITIES) was investigated, and their sensing applications were demonstrated. The micro-ITIES array was formed at polyethylene terephthalate membranes containing a 196 microhole array of radius 10.0±0.1 μm using a femtosecond laser. The characteristics of perrhenate ions transfer at the water/2-nitrophenyloctyl ether interface were first investigated using cyclic voltammetry (CV). CV was used in the estimation of some of the perrhenate anions thermodynamic parameters, such as the formal transfer potential and the Gibbs transfer energy. The technique of alternating current stripping voltammetry (ACSV) was also utilized to improve the sensitivity of the perrhenate anion detection. Under optimized preconcentration and detection conditions, a limit of detection of 0.3 μM with a wide linear dynamic range extending from 1.0 to 100 μM was achieved. The effect of various potential interfering anions on the perrhenate sensor was also investigated and an excellent selectivity over SCN-, I-, NO3-, NO2-, CO32-, SO42-, MoO42-, WO42- and CH3COO- ions was also achieved. This enabled quantitative measurements of rhenium in some mineral raw samples and the data was also validated by comparing with inductively coupled plasma atomic emission spectroscopy.

THEORETICAL BASES OF CHEMICAL TECHNOLOGY

17-25 241
Abstract
In this paper the finite element method (FEM) is used to solve three problems that are of the paramount importance in Chemical Engineering. The first problem is related with the bidimensional flow of an ideal fluid around a cylindrical body, and the objective is to determine the velocity distribution of the flow. To model the flow, the potential formulation is used to obtain an analytical solution, and then, the approximated solution obtained by using FEM is compared with the analytical solution. From this comparison, it is deduced that both solutions have a good agreement. The second problem is the calculation of the temperature profile in a two-dimensional body with specified boundary conditions. This problem is modeled by the two-dimensional Laplace equation, and from the problem data and using variables separation, an analytical solution was obtained. Then, FEM was used to obtain an approximate solution and compared with analytical ones. Besides, from this comparison, it is concluded that both solutions agree. Finally, in the third problem the temperature distribution in a bidimensional body with internal heat generation is studied. This problem is modeled by Poisson equation in two dimensions, but due to the boundary conditions and the complications that arise by adding some heat sources in the final FEM discretization, the problem does not have an analytical solution. However, the analysis of FEM solution indicates that this solution is correct.
26-38 513
Abstract
Polychloroprene is widely used as a special-purpose rubber in such industries as automotive, construction, textile industry. Chloroprene rubber takes a significant share in the market of elastomers due to its properties. In recent years, a gradual increase in demand for chloroprene rubbers is expected. This trend is most clearly seen in regions with a developed automotive industry. World leaders in the production of chloroprene rubbers and latex demonstrate their interest in increasing production capacity. In Russia, chloroprene rubber is not produced, the demand is completely met by import. In this paper, the main industrial methods for the production of chloroprene monomer, based on various feedstocks: acetylene and butadiene-1,3, exist in the world practice. Advantages and disadvantages of each of the above methods for producing chloroprene monomer are given. Technical solutions for the improvement of the chloroprene-monomer preparation technology for the steps of chlorination of butadiene-1,3 and dehydrochlorination of 3,4-dichlorobutene-1 in a column apparatus are proposed. An improved process for the preparation of chloroprene rubber from butadiene-1,3 is described. The development of a modern technology for the production of chloroprene rubber based on domestic raw materials will make it possible to obtain a high-quality target product, which will lead to the exclusion of its imports.

CHEMISTRY AND TECHNOLOGY OF ORGANIC SUBSTANCES

39-49 243
Abstract
The results of studies on chemical transformations of organic and organosilicon isocyanates in their interaction with hydrazine derivatives have been summarized in this review. It is shown that hydrazine and its derivatives including organosilicon compounds reacting with organic isocyanates form corresponding semicarbazides readily enough. The reaction conditions that effect the composition, structure and yield of the resulting target products are presented. A significant difference in the interaction of trimethylsilyl isocyanate with organic and organosilicon derivatives of hydrazine is demonstrated. It is demonstrated that the reason for the impossibility to isolate trimethylsilyl derivatives of semicarbazide is their low hydrolytic stability, as well as high silylating ability. Peculiarities of the reaction of trimethylsilyl isocyanate and dimethylchloromethyl isocyanate silane with 1,1-dimethylhydrazine, its trimethylsilyl analog and isoniazid are given. Possible schemes for the formation of a previously unknown O-trimethylsilyl-1,1-dimethylhydrazinecarboximidoate are presented. The results of using carbofunctional organosilicon isocyanates in these processes are discussed. Basic trends in practical use of the prepared compounds as physiologically active preparations in polymer chemistry and agriculture are shown.
50-57 245
Abstract
Liquid-phase oxidation of cyclohexane to cyclohexanol and cyclohexanone was studied in the absence of solvents under an air pressure of 0.5-5 MPa, in the temperature range 115-150 °C, catalyzed by N-hydroxyphthalimide (N-HPI). It was established for the first time that the use of N-HPI as a catalyst in place of the conventionally used metal salts of variable valence allowed a 2-3-fold increase in the conversion of the initial hydrocarbon and selectivity from 70-75 to 90%. The combined use of N-HPI with cobalt(II) acetate results in an additional increase in the conversion of cyclohexane by 30-40%, the selectivity of cyclohexanol and cyclohexanone formation to 94-97%, which seems to be due to the synergistic effect between the two components of the catalyst. The mechanism of catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone is discussed. It has been suggested that N-HPI plays a dual role in the oxidation of cyclohexane: it catalyzes the conversion of cyclohexane to cyclohexanol and cyclohexanone and, on the other hand, promotes the conversion of cyclohexanol to cyclohexanone, thereby substantially reducing the formation of adipic acid and its esters, by-products of the reaction, and increases selectivity of oxidation. This also explains the unusually high (1.3-1.5 : 1) ketone: alcohol ratio in the oxidation products of cyclohexane in the presence of N-HPI. The high selectivity of the formation of the desired products, the conversion of cyclohexane, the moderate temperature, the available catalyst, suggest that this method of oxidizing cyclohexane to cyclohexanol and cyclohexanone may be of interest for further practical use.

CHEMISTRY AND TECHNOLOGY OF INORGANIC MATERIALS

58-66 113
Abstract
It was investigated the influence of technological parameters of laser cladding on the thickness of the carbide composite coatings with similar composition and properties of matrix and different types of reinforcing inclusions (spherical tungsten carbides (WC) and recycled carbides). Special attention is paid to physical-mechanical and service properties of the composites such as hardness and resistance to abrasive wear. It is established that the thickness of the carbide composite coatings increases with increasing laser power and flow rate of the carrier gas, and with decreasing speed of the laser and the step of cladding. The study showed that at the addition of 50 wt.% WC matrix has smaller hardness values 540-560 HV, which allows to obtain the structure of the carbide composite coatings without cracks. At the same time, at addition of 80 wt.% WC matrix has higher hardness 670 HV, which does not provide the structure without cracks. Resistance of composites NiCrBSiC-WC to cracking, as well as their wear resistance, increases with increasing content of tungsten carbide. The wear resistance of the coatings received from powder Technicord 655-SL, with a reinforcement by recycled carbide, comparable to that for coatings from spherical tungsten carbide Tekmat WC-125. Coatings NiCrBSiCWC, obtained by laser cladding, are used to increase the service life of the equipment telemetering systems, in particular, it is possible to prevent of abrasion and provide of increasing the service life of the contact pads of the equipment for measurement while drilling.

SYNTHESIS AND PROCESSING OF POLYMERS AND POLYMERIC COMPOSITES

67-73 172
Abstract
Synthetic surfactants have a wide application in various areas from medicine to agriculture, with biodegradable surfactants holding the greatest promise. Promising compounds for the synthesis of such surfactants are polyethylene oxide and polymers are the poly(α-hydroxyacid)s: polylactide (i.e. PLA), polyglycolide (i.e. PGA), poly-ε-caprolactone (PCL), polyhydroxybutyrate (PHB) and their copolymers. Because the biodegradation of polymeric surfactants yields natural metabolites, their medical and biotechnological applications are most attractive. A number of studies shows advantages of branched polymer surfactants compared linear surfactants, however, systematic studies of the correlation between the branched structures of amphiphilic copolymers and their surface activities are absent. Hyperbranched polyester polyol based on 2,2-bis(methylol)propionic acid are widely used as modifiers of polymeric materials (for example, in the manufacture of paintwork materials), additives for polymers to improve extrusion and also as nanocontainers for targeted drug delivery. In the present study the colloidal chemical properties of the polyether polyol 2,2-bis (methylol) propionic acid of the fourth pseudo generation (trade name Boltorn H40) were studied and it was shown that they reduce the interfacial tension at the hydrocarbon solution of surfactant/water to low.

MATHEMATICAL METHODS AND INFORMATION SYSTEMS IN CHEMICAL TECHNOLOGY

74-80 114
Abstract
Development of information-analytical system of radiation control is based on existing methods and hardware-software measuring instruments for the purpose of systematizing, storing and processing the results of analysis of samples of various composition and origin. Studying a large flow of environmental and technological samples includes the most difficult task to ensure the required accuracy of calculation of activities and errors, especially at low activities levels at the threshold of detectable area. The information system hardware includes a set of devices designed to measure the activity of the samples, and a local computer network. The server part of the software package includes a client-server database management system and a web application for database administration. In addition to the standard programs included in the delivery of radiometric equipment the client part of the software package includes the program "ODRA", developed using object-oriented language C# in Microsoft Visual Studio. The program "ODRA" includes modules for calculating the specific (volumetric) activity of radionuclides in low-active samples of materials and environmental objects, as well as for calculating the relative and absolute error of activity determination. The program has a convenient graphical user interface for database communication. The information system of the radiation testing laboratory of the enterprise that conducts work with radioactive materials has undergone a four-year approbation in the experimental production mode at VNIIHT in 2014-2017 and can significantly reduce the processing time of the results of determining the radioactivity of technological and environmental samples and reduce the operator error factor.


ISSN 2410-6593 (Print)
ISSN 2686-7575 (Online)