Year of issue

Issue number

Article language

Sorting

2015, №1

pp. 3-8

Articles

Synthesis of Glycyrrhetinic Acid Monoglycoside by Hydrolysis of Glycyrrhizic Acid in Subcritical Water

O.V. Filonova, A.V. Lekar, S.N. Borisenko, E.V. Maksimenko, E.V. Vetrova, N.I. Borisenko, V.I. Minkin.

Quote

Key words: ammonium glycyrrhizinate, glycyram, glycyrrhizic acid, glycyrrhetinic acid, monoglycoside of glycyrrhetinic acid, electrospray ionization mass spectrometry, HPLC-MS, subcritical water

A method for synthesis of glycyrrhetinic acid monoglycoside by hydrolysis of glycyrrhizic acid in subcritical water at temperatures between 100 and 300 °C is developed. The maximum yield of the target product is obtained at 160 °C.

2015, №1

pp. 9-18

Articles

Luminescence of Nanocomposites Obtained Using SCF Impregnation of Polymer Powders by CdSe Quantum Dots

A.O. Rybaltovskii, Yu.S. Zavorotny, N.V. Minaev, V.K. Popov, D.S. Rubashnaya, P.S. Timashev.

Quote

Key words: polymer nanocomposite, supercritical carbon dioxide, quantum dots, photoluminescence, polytetrafluoroethylene, low-density polyethylene, diffusion embedding

Luminescence of composites based on quantum dots CdSe embedded into low-density polyethylene (LDPE) and polytetrafluoroethylene (PTFE) powders using supercritical carbon dioxide is studied. It is shown that thermal treatment of the resulting powders in air in the case of LDPE causes the CdSe photoluminescence band shift to shorter wavelengths, but in the case of PTFE — to longer wavelengths with simultaneous decrease of integral luminescence intensity. The behavior of photoluminescence bands under near UV radiation in both cases is determined by photo-oxidation processes on the CdSe nuclei.

2015, №1

pp. 19-34

Articles

Key words: statistical physics, critical phenomena, molecular spectra theory

Careful analysis of CARS-spectroscopy data for carbon dioxide Fermi-dyad shows that critical density variance must not exceed 0.4 and the lifetime of critical density fluctuations is not less than 10 ns. To comprehend the experimental data, the contribution of critical fluctuations to the spectral line width is evaluated taking into consideration their lifetime.

2015, №1

pp. 35-60

Articles

Key words: temperature, pressure, density, concentration, phase, fluid, equation of state, compressibility factor, reduced parameters

The results of thermal and thermodynamic properties (diagrams of state) calculation of water-aliphatic alcohol (methanol, ethanol, n-propanol) systems in liquid and vapor phases, as well as in the state of supercritical fluid are presented. They are based on the equation of state that represents the compressibility factor as power series of reduced density (ω = ρ/ρcr) and temperature(t = T/Tcr)
\(Z=\frac{\rho}{RT\rho_m}=1+\sum_{i=1}^{m}\sum_{j=0}^{n_i}\frac{a_{ij}\omega^i}{\tau^j}\)
and describes the experimental р, ρ, Т, х-relations with an average relative error 1.2%.

2015, №1

pp. 61-69

Articles

Key words: ethanol, fuels, hydrolysis, gasification, saccharification, supercritical fluids

Publications devoted to the application of supercritical fluids to deep biorefinery of vegetable raw materials for production of wide range of products, such as ethanol, liquid and gaseous fuels, sugars, organic acids, and oils are reviewed and analyzed. The specific features of the supercritical fluid technologies and their advantages in comparison with the existing traditional methods of biorefinery of vegetable raw materials are demonstrated.

2015, №1

pp. 70-77

Articles

Manufacturing of Porous Ultrahigh Density Polyethylene Using Subcritical Water

D.Yu. Zalepugin, A.V. Maksimkin, N.A. Tilkunova, I.V. Chernyshova, F.S. Senatov, M.I. Vlasov.

Quote

Key words: ultrahigh density polyethylene, subcritical water, porosity, implant

The method of subcritical water extraction of NaCl from ultrahigh density polyethylene (UHDPE) samples is developed as a stage in the manufacturing of porous polymer — a promising material for implant production. Optimal process parameters were determined as follows: pressure 250 atm, temperature 120 °С, water flow rate 3 g/min. This method provides with a tenfold reduction of salt extraction time (from 10 to 1 h). The main pore diameter of UHDPE determined by scanning electronic microscopy ranges from 80 to 700 µm.

2015, №1

pp. 78-85

Articles

Key words: phase diagrams, solubility, liquid-liquid immiscibility, critical phenomena

The system LiOH—H2O is characterized by the immiscibility phenomena both in equilibrium with vapor and solid saturated solutions or without solid phase. Solubility of LiOH increases as a result of immiscibility phenomena at ∼355 °С and further increases above this temperature up to the melting point. The immiscibility region (g - l1 - l2) is terminated by the critical phenomena (g = l1 - l2) at ∼390 °С. A separation of liquid phases is observed at elevated pressures (at ∼39 MPa) and temperatures up to 425 °C.

2015, №2

pp. 4-16

Articles

Improvement of Functionality of Carbonate Macadam via Supercritical Fluid Impregnation with Bituminous Compounds

F.M. Gumerov, M.I. Farakhov, V.F. Khairutdinov, R.F. Gabitov, Z.I. Zaripov, I.Sh. Khabriev, T.R. Akhmetzyanov.

Quote

Key words: propane-butane mixture, supercritical fluid state, deasphaltizate, solubility, carbonate macadam, impregnation

A comprehensive process for deasphaltizing of heavy oil residue and subsequent treatment (impregnation using a solvent in supercritical fluid state) of a carbonate macadam by bituminous compounds (deasphaltizate) is developed. The purpose is to improve its functionality of the material and, above all, to reduce its water absorption capacity. The process parameters are specified based on the newly obtained data on thermal capacity of heavy oil residue and deasphaltizate. The results of the process experimental realization and characteristics of impregnated macadam, including the water absorption capacity decreased from 3.6 to 0.54 %, are presented.

2015, №2

pp. 17-30

Articles

Determination of Natural Aromatic Acids Using Supercritical Fluid Chromatography

D.V. Ovchinnikov, D.S. Kosyakov, N.V. Ul’yanovskii, K.G. Bogolitsyn, D.I. Falev, O.I. Pokrovskiy.

Quote

Key words: supercritical fluid chromatography, SFC, natural aromatic acids

Derivatives of benzoic and cinnamic acids are secondary metabolites of plants, widely spread in nature and possessing biological activity. It is shown that supercritical fluid chromatography (SFC) provides a high performance separation of nine most important representatives of this class of compounds with selectivity, which is dramatically different from the reversed-phase high-performance liquid chromatography. The retention and separation parameters of analytes for four chromatographic stationary phases of different nature are compared and the effect of supercritical fluid parameters and the composition of the mobile phase onto the chromatographic separation are analyzed. The optimum separation can be achieved using a silica-based sorbent with 2-ethylpyridinium linked groups. The proposed approach to determine the above mentioned compounds is based on the combination of chromatographic separation with multiwavelength spectrophotometric detection. It provides the detection limits in the range of 13.0—51.3 mg/L and the duration of analysis about 2.5 min. The developed approach is successfully tested on the analysis of real objects — three different kinds of wine.

2015, №2

pp. 31-39

Articles

Hydrolysis of Aralosides from Aralia Manchurian in Subcritical Water to Oleanolic Acid and its Derivatives

O.V. Filonova, A.V. Lekar, S.N. Borisenko, E.V. Vetrova, E.V. Maksimenko, N.I. Borisenko, V.I. Minkin.

Quote

Key words: subcritical water, aralosides, aralia manchurian, saponins, saparal, oleanolic acid, HPLC-MS

A method to obtain oleanolic acid (OA) and its derivatives by hydrolysis of aralia manchurian in subcritical water is developed. It is carried out on an example of pharmaceutical preparation «Saparal» at 120—240 °C in static regime. A maximal yield of OA is obtained at 210 °C.

2015, №2

pp. 40-50

Articles

Key words: supercritical fluid extraction, microwave radiation, rare earth elements, thorium, uranium, carbon dioxide, monazite concentrate, phosphogypsum, tributyl phosphate, di-(2-ethylhexyl)phosphoric acid

Supercritical fluid extraction (SCFE) using carbon dioxide containing tributyl phosphate (TBP) and di-(2-ethylhexyl)phosphoric acid (D2EHPA) or their adducts with HNO3 is proposed as a method to extract rare earth elements (REE), Th and U from monazite concentrate (MC) and phosphogypsum (PG). On the first stage, the product of baking the MC with Na2CO3 (MCS) is obtained in the presence of coal under microwave irradiation, in which phosphates of REE, Th and U present in the MC are converted into their oxides. Up to 50 % of REE can be recovered from the powdered MCS by the adducts of TBP and D2EHPA with HNO3 in SCFE conditions, whereas Th and U remain in the solid phase. After a complete dissolution of the MCS residue in the mixture of 4 M HCl and 0.05 M HF, Th and U are quantitatively extracted using supercritical carbon dioxide containing D2EHPA and thus separated from the REE that remain in an acidic solution. The conditions of quantitative isolation of REE, Th and U from PG are determined and the schemes for complex processing of MC and PG targeted to the recovery of REE separated from Th and U are suggested.

2015, №2

pp. 51-59

Articles

Key words: supercritical carbon dioxide, SCF-micronization, supercritical antisolvent precipitation, arbidol, bioavailability

The possibility to obtain microparticles of arbidol using supercritical antisolvent (SAS) precipitation method is demonstrated. Non-monotonic dependence of average particle size on arbidol concentration in methanol and DMSO is observed. The position of its minimum depends on the type of used solvent. SAS technique allows one to vary the size (1.8—500 μm) and morphology of arbidol particles which can be operated by process parameters.

2015, №2

pp. 60-70

Articles

Key words: ammonium palmitate, supercritical carbon dioxide, solubility, dynamic regime

The solubility of ammonium palmitate in supercritical carbon dioxide is studied in the dynamic regime at 308.15—333.15 K and 10.0—35.0 MPa. Experimental data are described in the framework of the Peng—Robinson equation of state.

2015, №2

pp. 71-83

Articles

Biodiesel Production in Supercritical Fluid State Using Heterogeneous Catalysts

S.V. Mazanov, A.R. Gabitova, L.H. Miftahova, R.A. Usmanov, F.M. Gumerov, Z.I. Zaripov, V.A. Vasil’ev, E.A. Karalyn.

Quote

Key words: transesterification, heterogeneous catalysts, fatty acids ethyl esters, thermal decomposition, kinematic viscosity

Catalytic and non-catalytic transesterification of rapeseed oil in ethanol at supercritical fluid conditions with exposure to ultrasonic reactive environment are studied at 623— 653 K, 30 MPa and molar «alcohol-to-oil» ratios 12 : 1 and 18 : 1. The effect of heterogeneous catalysts on the reaction rate us revealed. Correlation between the fatty acids ethyl esters content in biodiesel and kinematic viscosity of the reaction product is established.

2015, №3

pp. 4-15

Articles

Key words: solubility, IR-spectroscopy, supercritical fluids

A self-consistent approach to the measurement of solubility of biologically active compounds in supercritical (SC) media based on the infrared spectroscopy is exemplified by paracetamol in supercritical CO2. According to this approach, the integrated extinction coefficient for a chosen analytical spectral band is determined from additional spectroscopic measurement of the compound under study dissolved in an inert solvent at known concentrations in the considered range of the parameters of state (pressure and temperature — p, T ). The values of solubility of the compound under study in the SC medium are calculated based on the above obtained values of the extinction coefficient and the analytical values of the integral intensity of the chosen spectral band for saturated solutions in the p,T-range of interest. The method allows one to determine the solubility with a high accuracy even if the measured values are as low as 10-4—10-1 mol.%.

2015, №3

pp. 16-25

Articles

Cellulose Convertion to Polyols in Subcritical Water

O.V. Manaenkov, O.V. Kislitza, A.E. Filatova, V.Yu. Doluda, E.M. Sulman, A.I. Sidorov, V.G. Matveeva.

Quote

Key words: subcritical water, cellulose, polyols, hydrolytic hydrogenation, hypercrosslinked polystyrene, heterogeneous catalysis

It is demonstrated that subcritical water is efficient as a medium for the cellulose conversion process to produce polyols. A novel type of Ru-containing catalysts supported on hypercrosslinked polystyrene (HPS) is suggested. In the presence of the catalyst containing 1% Ru the total yield of sorbitol and mannitol reaches 50 %; this is comparable with the results obtained in the presence of more complex and, therefore, more expensive catalytic systems. The influence of both the process conditions and the catalyst properties on the target product yield is studied. The hydrolytic hydrogenation of cellulose in subcritical water using Ru-containing catalysts can be considered as a basis for novel technologies of cellulose-containing biomass conversion and production of raw materials for chemical synthesis and industrial production of second generation biofuels.

2015, №3

pp. 26-38

Articles

Supercritical Fluid Fabrication of the Components for Risperidon Sustained Release Injectable Formulation

V.N. Bagratashvili, S.E. Bogorodski, A.M. Egorov, L.I. Krotova, V.K. Popov, V.I. Sevastyanov.

Quote

Key words: polymer microparticles, encapsulation of bioactive components, sustained release dosage forms, supercritical carbon dioxide

The process of supercritical fluid encapsulation of pharmaceutical grade risperidon into bioresorbable D,L-polylactide microparticles by PGSS (Particles from Gas Saturated Solutions) method is studied. Micronization and change of morphology of risperidon crystals during its encapsulation into polymer plasticized by supercritical carbon dioxide is experimentally observed. This finding enabled fabrication of polymer structures of various dispersion (10—100 μm) and morphologies comprising up to 40 wt.% of risperidon without any use of organic solvent. The kinetics of risperidon release from the polymer microparticles into physiological solution is studied by UV-spectrophotometry. It is shown that the use of different molecular weight D,L-polylactides enables one to extend the risperidon release time from bioresorbable polymer particles fabricated by PGSS up to 10 days in a controllable manner.

2015, №3

pp. 39-48

Articles

Key words: alkylbenzenes, partial oxidation, H-ZSM-5

Reactions of substituted benzenes — toluene, p-xylene, fluorobenzene, phenol, cumene and styrene — with nitrous oxide as an oxidant on H-ZSM-5 catalyst under supercritical conditions at 345—420°C and 70—150 atm was investigated.

It is shown that the products of disproportionation, isomerization and condensation that do not contain oxygen form predominantly. Only in the oxidation of toluene the selectivity to oxidation product (cresols) reaches up to 35 %. The yield of corresponding phenols in oxidation of alkyl-, hydroxy- and fluorobenzenes is negligible. Double bond conjugated with π-system of benzene rings (styrene), as well as the presence of branched alkyl substituents (in cumene) and hydroxyl-group (in phenol) hinder the formation of benzene ring oxidation products.

2015, №3

pp. 49-62

Articles

Key words: ibuprofen, supercritical CO2, polymorphism, quantum chemistry, molecular dynamics simulation

The conformational equilibria of ibuprofen in vacuum and in supercritical carbon dioxide are studied using methods of quantum chemistry and classical molecular dynamics. In supercritical carbon dioxide ibuprofen forms 12 different conformations, two of them correspond to the structures of the molecule in the crystal lattice of the first and second polymorph. It is shown that the GAFF force field allows one to obtain the characteristics of conformers, almost coinciding with those obtained by quantum-chemical calculations in the B3LYP/cc-pVTZ level of theory.

2015, №3

pp. 63-70

Articles

Key words: molecular association, solubility, supercritical fluid, methylxanthine

Experimental data on solubility of methylxanthines (theophylline and theobromine) in the system «supercritical (SC) CO2-methanol» at various concentrations of methanol is analyzed in the framework of the ASL (Associated Solution + Lattice) model based on the molecular association theory and the simple lattice concept. 1H NMR spectroscopy is applied to investigate hetero-association of methylxanthines with methanol at 313 K. The contribution of molecular association to the solubility of methylxanthines in a mixed SC CO2-methanol solvent is discussed. It is shown that the presence of NH groups in methylxanthine molecule (i.e. theobromine and theophylline vs. caffeine) leads to the increasing contribution of solubility component related to the molecular association.