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Fine Chemical Technologies

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Vol 14, No 2 (2019)
View or download the full issue PDF (Russian)
https://doi.org/10.32362/2410-6593-2019-14-2

CHEMISTRY AND TECHNOLOGY OF ORGANIC SUBSTANCES

5-14 3427
Abstract

In recent years, the class of polymethine (cyanine) dyes has attracted increasing attention of researchers in the field of nanotechnology due to the structural features of their chromophore system and their tendency to form polymolecular states – dye aggregates. The processes of the formation of aggregates with new optical and electronic properties in aqueous solutions were studied as exemplified by anionic thyatrimethinecyanine dyes. It was shown that the aggregates are formed by a “block” mechanism from dimers. The nanoarchitecture of the aggregates is determined by the type of the alkyl substituent in the meso position of the polymethine chain of the dye. The C2H5 group promotes the formation of long-wavelength J-aggregates with the “brickwork” packing of molecules. The CH3 group promotes the formation of short-wave H-units with the “stepladder” packing of molecules. The formation of spatial isomers – J- and H-aggregates from cis and trans conformations of dye molecules – was established. Inorganic and organic cations, which stabilize highly organized aggregate structures, have a significant effect on the formation of aggregated forms of anionic dyes. Thus, the work presents the author's ideas about a new scientific direction – the nanoarchitecture of aggregates of polymethine dyes.

THEORETICAL BASES OF CHEMICAL TECHNOLOGY

15-22 235
Abstract

The aim of the work is to consider the mechanism of clogging the pores of the filter unit by small particles from the flow of filtrate inside them. Theoretical ideas about the process of filtering with the deposition of small particles from the filtrate on the pore walls and attribution of its fundamentals to restructuring from the original structure to the final structure allow to describe the process of clogging the pores using well studied concepts of known processes with phase transformations (in particular, crystallization). Based on this analogy and the approach to the description of the transformation of the "old" structure into a "new" one in time, using experimental data and their processing we calculated the rate of nucleation of the sediment centers (ωnucl), the linear (υlin) and volumetric rates of sediment plaques growth in the pores of the filter unit at different values of the process driving force, at different pressure difference in the system, and at different concentrations of solid particles in the suspension. Interpolation and extrapolation dependences were obtained for analyzing the mechanisms of sediments formation and growth for determining and calculating these (ωnucl, υlin) rates. Using the concepts of nonequilibrium thermodynamics to assess the influence of the driving forces we studied their influence (changes in the concentration of solid particles in the filtrate suspension and pressure drop across the filtering layer) on the dynamics of the filtration process. Using the data obtained it is possible to find the degree of clogging of through pores, which determines the filtration conditions, the filter septum type, and the filter overall dimensions.

23-32 230
Abstract

Using the results of an earlier study of the physicochemical properties of the reaction system of the process of producing mesityl oxide, an analysis of the statics of the combined variant of the organization of this process was carried out. It is shown that of practical interest are the modes of the process corresponding to the first specified separation. In this case, the limiting stationary states, characterized by the maximum acetone conversion, selectivity, and the yield of the target product — mesityl oxide, are distinguished. The possibility of practical implementation of the limiting stationary state of the reactive distillation process for producing mesityl oxide, which provides almost complete conversion of acetone with a yield of mesityl oxide approaching 100%, has been proved. The limit stationary state corresponds to the reaction-distillation process with the selection of a single product stream. For the mode of carrying out the combined process that corresponds to the selected limiting stationary state, a schematic flow chart for the production of the target product has been proposed. By means of computational research, it has been established that the most rational option for organizing a reaction hub is to use a single apparatus in it — the reaction-distillation column. In the Aspen Plus® software package, a process model was constructed that corresponded to the proposed technological scheme and through a computational experiment, its structural and parametric optimization was carried out. As a result, the static parameters of the technological system were established, as well as the characteristics of the apparatuses, allowing to obtain the required quality product in the reactiondistillation column. output, approaching 100%. It has been shown that when modeling a chemicaltechnological system, it is necessary to use different sets of parameters of the basic equation used to describe phase equilibrium. Thus, for calculating reactive distillation and distillation columns, the liquid – vapor phase equilibrium parameters for the mesityl oxide–water system should be used, and when calculating the Florentine vessel for this mixture, it is necessary to use the parameters corresponding to the liquid – liquid equilibrium. The use of a single set of parameters of the basic equation leads to significant errors and inadequate description of the process of producing mesityl oxide by condensation of acetone.

CHEMISTRY AND TECHNOLOGY OF MEDICINAL COMPOUNDS AND BIOLOGICALLY ACTIVE SUBSTANCES

33-40 3644
Abstract

The aim of this work was to study the possibility of perfluoroorganic solvents use for extraction of main compounds of essential oil from Anethum graveolens L. fruits. We used Anethum graveolens L. fruits with particle size of 0.1–0.5 mm for extraction. We used the method of simple maceration for 24 hours, with raw material to solvent ratio of 1:10 w/v at 24±1°С. Besides, we used the method of circulation extraction in the Soxhlet extractor with raw material to solvent ratio of 1:5 w/v for 1 to 4 hours. The qualitative analysis of extracts was carried out by the method of GC-MS. The quantitative analysis of carvone was carried out by the method of RP HPLC at 240 nm analytical wavelength. The use of simple maceration method provided the following yields of carvone into all types of solvents: 95±4 % for n-hexane, 95±4 % for Novec 7100, and 69±3 % for Novec 1230. The use of the circulation method of extraction for 60 min of solvent circulation provided the following yields of carvone: 93±4 % for Novec 1230 and 92±4 % for Novec 7100. It was noted that the extract obtained with solvent Novec 7100 was contaminated by fatty oil and required an addition stage of purification. The results obtained suggest that perfluoro organic solvents have good prospects and applicability in the phytotechnology for the extraction of some types of biologically active compounds and essential oils from the plant raw material.

SYNTHESIS AND PROCESSING OF POLYMERS AND POLYMERIC COMPOSITES

41-50 3381
Abstract

Organic–inorganic hybrid cryogels of poly(vinyl alcohol) (PVA) containing silica inclusions (SiO2) were obtained and studied. Such inclusions were formed in the course of hydrolytic polycondensation (sol-gel process) of tetramethoxysilane (TMOS) introduced into concentrated polymer solutions in dimethyl sulfoxide (DMSO). PVA concentration in these solutions was 60, 80 or 100 g/L; while the concentration of TMOS was varied in a range of 0.15–0.61 mol/L. The polymer solutions were subjected to the cryogenic treatment at temperatures by 40 °С lower than DMSO crystallization temperature (+18.4°C). The frozen samples were thawed out at a heating rate of 0.03°/min. It is shown that moderate freezing at −21.6 °C, then frozen storage and subsequent thawing of the initial reaction mixture PVA/DMSO/TMOS/acid catalyst resulted in the formation of strong macroporous PVA/SiO2 cryogels. Such cryogel materials are hybrid systems, because the gel-forming polymer and the silica containing moieties belong to the content of the gel phase. The basis of this intermolecular interaction is hydrogen bonding between OH groups of the adjacent chains. This leads to the formation of modified microcrystallinity zones that perform as the nodes of the three-dimensional network of cryogels. The effects of significant increase in their rigidity and heat-resistance with increasing PVA and TMOS concentration in the initial feed were also observed. It was shown that the success of the synthesis of transparent elastic and heat-resistant PVA/SiO2 cryogels depends on the choice of the optimal ratio between the precursors and the combined effect of the liquid (methanol and water) and silicon-containing components on the formation of multiple hydrogen bonds and microcrystallites.

51-59 243
Abstract

The dispersion composition of polymer suspensions and molecular weights of polymers obtained by suspension polymerization of MMA in the presence of polymer surfactants – methylmethacrylate and methacrylic acid copolymers – were studied. It is shown that a highly dispersed fraction of particles with diameters of 0.02–2.0 µm and a fraction of particles with large diameters (up to 1000 µm) are always present in the polymer suspension. After fractionation of polymer suspensions 3 fractions of particles with different diameters were obtained. For each particle fraction the molecular masses of polymers were determined by viscometry. A significant difference in the values of the molecular masses of polymers obtained as particles of small and large diameters – 105 and 106 Da, respectively – is shown. The presence of a highly dispersed fraction of particles in which a polymer of high molecular weight is formed has a noticeable effect on the average molecular weight of the polymer. In particles of small diameter polymerization takes place according to a mechanism close to the emulsion, due to the fact that the volume of such particles contains a small amount of radicals. The high rate of polymerization leads to the formation of a polymer of high molecular weight, the appearance of a gel effect and a decrease in the termination constant. In most particles, polymerization proceeds by a mechanism close to the solution polymerization, and polymers of low molecular weight are formed. This makes it possible to synthesize polymers of a given molecular weight in drops of certain dispersity.

60-69 197
Abstract

Electrically conductive composites based on high density polyethylene (HDPE) / ultrahigh molecular weight polyethylene (UHMWPE) blends filled with carbon black were studied. The work is a part of the research of electrically conductive materials for the manufacture of self-regulating polymer heaters. In this work, the authors investigated composites based on HDPE/UHMWPE (molecular mass of ~ 7 million) blends filled with carbon black (average particle size ~ 20 nm). The goal of the work was to obtain a self-regulating electrically conductive polymer material with optimal thermoelectric characteristics and high heat resistance. It was shown that the effect of adding UHMWPE to the HDPE/carbon black composites on the thermoelectric behavior of the resulting material was similar to cross-linking. This reduced the undesirable effect of the negative thermal coefficient (NTC) of the electrical resistance. In addition, the heat resistance of the material at elevated temperatures was increased. This makes it possible to exclude the radiation or chemical cross-linking in the manufacture of self-regulating polymer heating elements. The rheological, mechanical and thermoelectric properties of HDPE/carbon black composites modified with UHMWPE were also studied. It was found that a diffusion interphase layer with a reduced fluidity in the melt of HDPE/UHMWPE blends was formed. It was established that self-regulating composites containing 30–40% of UHMWPE had the best operational properties. We can recommend the methods of extrusion and injection molding for the processing of HDPE/carbon black composites mixed with 30% UHMWPE, and the pressing method in case of UHMWPE content of 40%. The ability of the composites to be molded is sharply reduced at higher contents of UHMWPE.

CHEMISTRY AND TECHNOLOGY OF INORGANIC MATERIALS

70-77 238
Abstract

Currently, various amino bisphosphonates are widely used in the treatment of many bone diseases. One of the most well-known complex compounds of neridronic acid (6-amino-1-hydroxyhexylidene-1,1- bisphosphonic acid) is sodium neridronate – a bisphosphonate, which is used to treat osteogenesis and Paget's disease. However, there is no data on compounds of neridronic acid with rare earth elements. A new complex of lanthanum with 6-amino-1-hydroxyhexylidene-1,1-bisphosphonic acid (I) was obtained and characterized by various physicochemical methods (chemical analysis, IR spectroscopy, solid-phase 31P NMR spectroscopy, optical microscopy, PCA, DTA). According to the research data the complex I has the composition {La[(H3N-(CH2)5-C(OH)(PO2(OH))2]2(H2O)2}[OH]·H2O and represents the coordination 1D-polymer due to two bridged phosphonic groups with lanthanum atoms in a tetragonal-antiprismatic environment. In a crystal, polymer chains form a 3D-frame porous structure by means of strong hydrogen bonds O─H ··· O and N─H ··· O with endless channels, available to include a variety of inorganic anions or small organic molecules. A study under the microscope showed that the sample is needle crystals (thin rods) of different lengths. The particle size distribution was obtained by laser diffraction, and the average particle size was determined: 50 µm in length and 2.5 µm in thickness.

ANALYTICAL METHODS IN CHEMISTRY AND CHEMICAL TECHNOLOGY

78-86 196
Abstract

A method for copper(II) determination based on copper(II) ions interaction with the organic reagent picramine-ε, concentrating the formed complex on a solid-phase matrix and recording diffuse reflectance spectroscopy spectra by a portable combined LED miniphotometer was developed. Poly-ε-caproamide membranes were investigated as solid-phase matrixes. It was found that the diffuse reflectance coefficient of the studied membranes in the visible spectrum region does not depend on wavelength. So, the signal from membranes does not distort the results of the analysis. Factors controlling the process of sorption of the copper(II) complex with picramine-ε were studied. It was shown that the poly-ε-caproamide membranes are effective sorbents which provide the possibility of concentrating the analyte at a level higher than 105. The dependences of analytical signal on the acidity of the solution, the time of keeping the complex in the solution and the initial volume of the solution passed through the membrane were studied. Based on the obtained data, the optimal conditions of the analysis were found. Calibration dependence of the analytical signal on the concentration of copper(II) in model solutions was estimated. The method was tested for the determination of copper(II) ions in white wine. The method of additives was used for the analysis. It was found that the concentration of copper(II) ions in “Vagrus” wine is 0.0016 mkg/ml.



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