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Fine Chemical Technologies

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Vol 17, No 3 (2022)
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189-200 111
Abstract

Objectives. To apply an analytical method for the calculation of a distillation column for the production of D2O at a two-column Kuhn installation operating under vacuum: to simulate the Kuhn installation in the Hysys software; and to compare experimental and calculated data.

Methods. Analytical method for the calculation of distillation columns “from stage to stage,” from the lower theoretical separation stage (TSS) to the upper stage. This method is based on phase equilibrium at the TSS with known data of input flows and component concentrations in the column bottoms. Hysys was used as modeling software.

Results. Comparison of the calculation results with Kuhn’s experimental data testified to the high calculation accuracy of the vapor–liquid phase equilibrium for the H2O–D2O mixture at the TSS. The convergence of the D2O material balance for the entire installation was 0.005%. The identification parameter was the number of the column feed plate. Simulation of the Kuhn installation in the Hysys software showed a qualitative agreement of D2O concentrations in material flows. The UNIQUAC (UNIversal QUAsiChemical) model was used to calculate activity coefficients. The found values of the number of theoretical separation stages (NTSS) in both columns, were 88 and 153 taking into account the reboiler and condenser. This is less than the experimental 295 and 400, respectively. The discrepancy can be explained by the increased phase equilibrium H2O constant in the UNIQUAC model. However, the convergence of the material balance in terms of D2O was high and amounted to 1.38·10−6 %. The absolute error of the found concentrations in material flows did not exceed 0.12 mol %.

Conclusions. The results obtained indicated the possible use of the Hysys modeling software when searching for and optimizing the operating mode of the block diagram of a cascade of distillation columns with direct and recycle flows to separate a mixture of water into light and heavy water. The final results obtained with regard to the operating mode, inlet and outlet material flows (flow rate, composition, temperature, and pressure drop across the column) are recommended for use in the analytical program for the calculation of the distillation column to refine the NTSS and distribution profile of the concentrations of the H2O and D2O components along the height of the column.

201-209 108
Abstract

Objectives. To study the hydrogenation of substituted 5-acyl-1,3-dioxanes in the presence of metal-containing catalysts (Pt/Re, Pd/C, Ni/kieselguhr, and Ni/Mo).

Methods. In order to determine the qualitative and quantitative composition of the reaction masses, the following analysis methods were used: gas-liquid chromatography (using the Kristall 2000 hardware complex); mass-spectroscopy (using Chromatec-Kristall 5000M device with NIST 2012); nuclear magnetic resonance (NMR) spectrometry (using Bruker AM-500 device with operating frequencies of 500 and 125 MHz).

Results. Hydrogenation of substituted 5-acyl-1,3-dioxanes obtained by condensation of carbonyl compounds with paraformaldehyde and sulfuric acid was used to synthesize heterocyclic alcohols in the presence of metal-containing catalysts with a conversion of the initial ketones of 60–90% and a formation selectivity of target products of 70–90%. Substances were analyzed and confirmed by gas-liquid chromatography, mass spectrometry and NMR spectroscopy.

Conclusions. The best catalyst for the reduction of substituted 5-acyl-1,3-dioxanes is Pd/C. By using this catalyst, it is possible to achieve a high selectivity for the formation of the corresponding heterocyclic alcohols at a conversion rate of the initial ketones of 60–90%.

210-230 108
Abstract

Objectives. With the growing resistance of pathogenic microorganisms to antibiotics, the development of new antimicrobial drugs offering specific mechanisms of action becomes an urgent task. Only few antimicrobials offer a broad spectrum of activity against gram-positive and gram-negative bacteria, molds, and yeasts. In this regard, the purpose of the work was to develop methods for synthesizing biologically active derivatives of alkyl-substituted phenols (reactions at the hydroxy group) to study their biological effect.

Methods. The synthesis of imidazole acetates of substituted phenols was carried out in two stages. At the first stage, the chloroacetyl derivative of the selected compounds was obtained, to which imidazole was then added. O-acylation reactions at the first stage of the synthesis were carried out under varying conditions. The first version of the synthesis was carried out using chloroacetyl chloride as an acylating agent together with a high-boiling solvent. In the second variant, chloroacetic anhydride was used, along with an attempt to replace the solvent with a low-boiling one. A thymol methoxy derivative was additionally synthesized by a known method using methyl iodide and varying the reaction parameters.

Results. The parameters of chloroacetylation and methoxylation of aromatic alcohols were optimized with rational selection of solvents and the ratio of reagents in the reactions. Synthesized thymol (2-isopropyl-5-methylphenol) and propofol (2,6-isopropylphenol) derivatives contained imidazole as an additional pharmacophore with affinity for microorganism cell membrane proteins. A thymol methoxy derivative comprising an aromatic ether exhibiting increased hydrophobicity was also obtained. The synthesized compounds were characterized by NMR spectroscopy.

Conclusions. Chloroacetyl derivatives of aromatic alcohols can be effectively synthesized by cooling the reaction mixture using an excess quantity of an acylating agent and increasing the reaction time (compared to literature data). The yield of thymol chloroacetate was 75%, while that of propofol chloroacetate was 30%. This can be explained by the sterically hindered reaction of the propofol alcohol group, which has isopropyl substituents at the second and sixth positions of the benzene ring.

231-241 119
Abstract

Objectives. To investigate the production and biological degradation of biodegradable hybrid compositions (BHCs), dispersed-filled with starch-containing products of various origins and distilled monoglycerides, along with the biodegradation of compositions based on low density polyethylene and thermoplastic starch (TPS) of various origins: corn, pea, and rice.

Methods. Thermoplastic starch was obtained based on native starches of several types, which were processed in Brabender and MashkPlast (Russia) laboratory extruders. BHCs in the form of strands, granules, and films were obtained by mixing thermoplastic starches with polyethylene in extruders. Structural BHC parameters were studied by optical and electron scanning microscopy. The biodegradability of the composite films was evaluated by placing them in biohumus for six months; during storage, the change in water absorption of the films was determined. Before and after the biodegradation process, tensile fracture stress and elongation at rupture were determined to evaluate BHC performance (physical and mechanical characteristics of films). Changes in the chemical structure during biodegradation were determined by Fourier infrared spectroscopy.

Results. The positive effect (acceleration of the biodegradation process) of using a novel type of starch plasticizer—monoglycerides distilled in TPS–polyethylene compositions—was confirmed. After six months, intensive sporulation of active microorganisms was observed on the surface of the samples. At the same time, water absorption by the samples reached 30%. The observed 60% decrease in strength and deformation properties indicates an intensive process of biodegradation.

Conclusions. The biodegradation rate was shown to depend on the concentration and even distribution of the natural biodegradable filler in the synthetic polymer composition.

 

242-252 113
Abstract

Objects. To synthesize monodisperse biodegradable hyperbranched polymers based on D,L-lactide in the presence of Boltorn™ H30 polyester polyol as a macroinitiator.

Methods. 1H and 13C nuclear magnetic resonance (NMR) spectroscopy was used to study the chemical structure of the Boltorn™ H30 polyester polyol and (Boltorn™ H30)-PDLA hyperbranched copolymers. The molecular weight distribution of the polymers was studied by gel permeation chromatography (GPC). In order to study the thermal stability of Boltorn™ H30 polyester polyol, thermogravimetric analysis (TGA) was used. Polymerization of D,L-lactide was carried out in a block in the presence of Boltorn™ H30 polyester polyol.

Results. The degree of branching of Boltorn™ H30 polyester polyol was calculated from NMR data, while the TGA method was used to determine the upper operational temperature range. The polymerization of D,L-lactide in the presence of Boltorn™ H30 polyester polyol used as a macroinitiator was studied. The molecular weight characteristics of the obtained copolymers were studied by NMR and GPC.

Conclusions. Optimum conditions were determined for the polymerization of D,L-lactide when using Boltorn™ H30 polyester polyol as a macroinitiator. The possibility of synthesizing narrowly dispersed hyperbranched polymers (Boltorn™ H30)-PDLA under the described conditions was demonstrated.

253-267 95
Abstract

Objectives. To validate a new method for the quantitative determination of 31 potent and narcotic substances and their metabolites in urine that meets the requirements of ISO/IEC 17025 using a fast and highly sensitive method of chromato-mass spectrometry with a view to introducing such a method into the routine practice of the National Anti-Doping Laboratory of the Lomonosov Moscow State University (NADL MSU).

Methods. Urine samples soldered with standard solutions were analyzed using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS).

Results. Diagnostic precursor/ion-product pairs and collision energies were established to allow unambiguous identification of the analyzed substances. During sample preparation, hydrolysis conditions were optimized. Selectivity, linearity, limits of qualitative determination, limit of quantitative determination (established under the contract with the customer firm), matrix effect, and measurement uncertainty were defined. Systematized data grouped by classes of analytes are given in the final table.

Conclusions. The important advantages of the presented technique are the absence of complex and lengthy sample preparation, as well as the short time of the analysis method (about 10 min), which can significantly reduce duration along with labor and analysis costs. The addition of new analytes will ensure the versatility of the technique, as well as expanding its scope.

 



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