Key words: мелкокристаллический корунд, до- и сверхкритическая водная среда, твердофазная подвижность, формирование кристаллов, распределение по размерам микрокристаллов, логнормальная функция, коалесценция, поверхностное растекание, рекристаллизация
A mechanism of the fine-crystalline corundum synthesis from aluminum hydroxide in
the conditions of induced nucleation in the supercritical water fluid at 400°C, an
initial pressure of 26.4 MPa, and subsequent exposure in a synthesis medium is considered.
The size distribution of the crystals was based on the analysis of electron microscopic
images. The use of the lognormal function to describe the crystal size distribution of
the synthesized corundum particles is substantiated. The possibility of using the
lognormal particle size distribution function and the time dependence of its parameters
to reveal the formation routes of the product crystals is analyzed. It is found that the
dimensional spectrum of microcrystals has four components, the appearance of which
is associated with different routes of the product formation. The number of distribution
components remains unchanged during the prolonged exposure, but their average
characteristics have different time dependences. The redistribution of the mass during
recrystallization, which leads, on the whole, to a decrease in the average crystal size, is
explained by differences in the mobility of the crystal structure of different components.
It is concluded that the states of corundum in the newly formed crystals and in the
buildup layer on the particles of the inducing additive are different.
doi:10.34984/SCFTP.2018.13.1.001
Key words: цветки ромашки аптечной, экстракция, субкритическая вода, 7-метоксикумарин, лютеолин, апигенин, дериватизация
UV-spectroscopy, gas chromatography / mass spectrometry, high efficiency liquid
chromatography and gravimetry methods were employed to study the extracts of
biologically active substances (BAS) from the flowers of chamomile growing in the
Samara region. The extracts were obtained using the subcritical water and aqueous
solutions of ethanol at 150 and 200 °C and 5 MPa. The BAS in the extracts were identified
using a reactive gas chromatography.
doi:10.34984/SCFTP.2018.13.1.002
Key words: 1,4-диоксан, термическая устойчивость
Thermal stability of 1,4-dioxane below and above its critical temperature (at 300—
500 °C) and at different fluid densities is studied. In the temperature range of 300—
350 °C dioxane is thermally stable during 80—100 minutes; at higher temperatures
during the same time the uncontrolled pressure growth starts due to the thermal
cracking of dioxane. The analysis of liquid and gas phases after the dioxane thermal
treatment shows the formation of a wide range of products.
doi:10.34984/SCFTP.2018.13.1.003
Key words: сверхкритический диоксид углерода, дифениламин, растворимость, динамический режим, СК-CO<sub>2</sub>-экстракция
The results of experimental studies of solubility of diphenylamine in supercritical
carbon dioxide (SC-CO<sub>2</sub>) are presented. Research was carried out at temperature
323.15 K in the pressure range from 10 to 35 MPa on the experimental plant implementing
a dynamic research method, produced by «Reaction Engineering, Ink.» (South Korea).
Experimental solubility data are described using the Peng — Robinson equation of
state. The results of SC-CO<sub>2</sub>-extraction process of ether-ethanol mixture from the
samples of «Sunar 308WIN» brand gunpowder are presented, and process parameters
corresponding to the maximum preservation of diphenylamine in the powder are
defined, the efficiency of this process is shown.
doi:10.34984/SCFTP.2018.13.1.004
Key words: сополимер этилена с винилацетатом, сверхкритический CO<sub>2</sub>, фазовое равновесие, растворимость, диспергирование, метод SEDS, кристаллизация
The results of an experimental study of the characteristics of phase equilibria for the
systems consisting of toluene, supercritical carbon dioxide and ethylene-vinyl acetate
copolymers (EVAC) are presented. The joint dispersing of different EVAC's and
polyethylene using the SEDS method is performed at 8.0—25 MPa and 313, 323 and 333
K. A comparison of melting and crystallization processes in the mixtures of copolymers
shows that those obtained by the SEDS method have higher degree of crystallinity as
compared with the mixtures of the same compositions, but obtained by melt mixing.
doi:10.34984/SCFTP.2018.13.1.005
Key words: сверхкритическое антисольвентное осаждение, сальбутамол, микронизация, морфология, степень пересыщения
The applicability of the method of supercritical antisolvent preci pitation (SAS) to
obtain microparticles of an anti-asthmatic salbutamol sulfate preparation suitable for
the production of an inhalable dosage form is studied. Depending on the concentration
of salbutamol in the starting solution, its flow rate and the pressure, spherical or needle
shaped particles of 0.7 to 8.5 microns can be obtained. The dependence of the average
particle size on the concentration of salbutamol in the initial solution is nonmonotonic.
The conditions for the production of particles suitable in shape and size for the
inhalation dosage form are determined.
doi:10.34984/SCFTP.2018.13.1.006
Key words: сверхкритический диоксид углерода, микрокапсулирование, импульсная сверхзвуковая струя, наночастицы TiO<sub>2</sub>
The process of microencapsulation of titanium dioxide nanoparticles in polyethylene
glycol PEG 8000 at pulse expanding of the jets of polymer solution in supercritical
carbon dioxide in vacuum and in a background gas (helium) is experimentally studied.
In both cases, at given initial temperature and cosolvent (ethanol) concentration the
distance from the nozzle exit to the point of «coil—globule» transition on the jet axis
is determined using the electron microscopy data. The dependence of the transition
point position on the initial temperature and the concentration of ethanol in the
reactor is obtained.
doi:10.34984/SCFTP.2018.13.1.007
Key words: импрегнация, сверхкритический диоксид углерода, ЭПР, метод спиновых зондов, матриксы для тканевой инженерии.
The spin probe technique as a version of the electron paramagnetic resonance (EPR)
spectroscopy was used to reveal the regularities of the formation of porous matrixes
based on D,L-polylactide in a supercritical CO<sub>2</sub> medium with the simultaneous
impregnation by paramagnetic biologically active test molecule 4-Hydroxy-2,2,6,6-tetramethylpiperidine
1-oxyl (TEMPOL). The dependences of the average and local dopant
concentration on impregnation conditions were estimated. It was concluded that EPR
spectroscopy is a promising method for studying porous polymeric materials formed
in supercritical conditions. Impregnation of the polymer with a paramagnetic compound
allows one to estimate the uniformity of the dopant distribution in a sample on both
macroscopic and microscopic levels, and also to judge the structure of the polymer
matrix. The data obtained by EPR and optical spectroscopy showed that the resulting
matrixes meet the important requirements for porous materials for tissue engineering.
doi:10.34984/SCFTP.2018.13.1.008
Key words: синтез титаната бария, докритический водный флюид, нанокристаллы титаната бария
The structure and morphology of fine-crystalline barium titanate synthesized in a
subcritical water fluid at 230 °C and 2.9 MPa were studied. Barium oxide, barium hydroxide
octahydrate Ba(OH)<sub>2</sub> ⋅ 8H<sub>2</sub>O and two modifications of titanium dioxide (rutile and
anatase) were used as starting reactants. Relationships between the composition and
properties of the reactants and the characteristics of the product (barium titanate)
were revealed. They indicate that the product structure in the subcritical water is
formed via a solid-phase mechanism.
doi:10.34984/SCFTP.2018.13.2.001
Key words: субкритическая вода, антиоксидант, кверцетин, рутин, гидролиз, бутоны, софора японская, <i>Sophora japonica</i> L.
The possibility of obtaining quercetin (a natural antioxidant) from buds of <i>Sophora
japonica</i> L. using subcritical water, which acts as a solvent and a reagent simultaneously
was studied. The suggested approach avoids the use of expensive and toxic organic
solvents, does not require separate extraction and hydrolysis steps and simplifies the
purification of the product. A 13-fold reduction in treatment time was achieved compared
with the traditional procedure to obtain high yield of quercetin. The loss of the target
product in the production of the dried extract was reduced.
doi:10.34984/SCFTP.2018.13.2.002
Key words: гидроксибензойные кислоты, гидроксикоричные кислоты, сверхкритический диоксид углерода, молекулярная динамика, водородная связь
Selective solvation of hydroxybenzoic (ortho-, meta- and para-hydroxybenzoic,
protocatechuic, gallic, syringic) acids and hydroxycinnamic (para-coumaric, caffeic)
acids by polar cosolvent (methanol) in supercritical carbon dioxide at temperature
318 K, solvent density 0.7 g/cm<sup>3</sup> and methanol concentration 3.5 mol.% is studied
using molecular dynamics method. The subject of the study is the formation of cosolvent
clusters around solute, the solute — cosolvent hydrogen bonding, the structural features
of hydrogen-bonded complexes associated with the molecular structure of solute (the
number and location of hydroxyl groups, the substitution of hydroxyl hydrogens by
methyl groups, and the presence of ethylene group between carboxyl group and
benzene ring).
doi:10.34984/SCFTP.2018.13.2.003
Key words: палладиевый катализатор, импрегнация, сверхкритический диоксид углерода, гидрирование
The synthesis of palladium and palladium-silver catalysts using supercritical fluid
CO<sub>2</sub>-impregnation process (static mode) was investigated. It is shown that the maximum
amount of metal is impregnated to the carrier in the temperature range 318—323 K
and pressure range 19.0—23.0 MPa. The activity of palladium catalysts prepared according
to the proposed method is comparable with the activity of industrial samples currently
produced.
doi:10.34984/SCFTP.2018.13.2.004
Key words: полимеры, сверхкритические флюиды, субкритические фреоны, диоксид углерода
Process of saturation of ultra high density polyethylene with sub- and supercritical
freons and supercritical carbon dioxide was investigated for the first time. It was
shown that subcritical freon R22 can be absorbed in much larger amounts by these
polymers than subcritical freon R410а, as well as supercritical R23 and carbon dioxide,
which makes it promising for use in the processes of impregnation and sterilization
of polymers.
doi:10.34984/SCFTP.2018.13.2.005
Key words: сверхкритическая флюидная импрегнация, флуоресцентная микроскопия, фотоактивные соединения
Fluorescence microscopy was used to study the distribution of photoactive compounds
(PAC) in polymer matrixes impregnated in supercritical carbon dioxide (SC-CO<sub>2</sub>). It
is shown that the character of the PAC distribution in polymers depends on the
nature of the matrix, the degree of interaction of the introduced compounds with
polymer fragments, and the sizes of the photoactive compounds corresponding diffusion
coefficients. Such information may be in demand for the development of functionally
oriented polymer systems impregnated with РAС (heterogeneous catalysis,
photochromic materials, medicine).
doi:10.34984/SCFTP.2018.13.2.006
Key words: циклонный сепаратор, сверхкритическая флюидная экстракция, улавливание экстракта
A low-volume cyclone separator with changeable extract collection reservoirs for the
supercritical fluid extraction is designed. A method for manufacturing the designed
separator by 3D-printing from an available polymer is proposed. It is shown that the
designed small volume separator allows for a greater extract recovery compared to a
standard large volume cyclone separator in the supercritical fluid extraction.
doi:10.34984/SCFTP.2018.13.2.007
Key words: лигнин, сульфатный щелок, сверхкритическая вода, газификация, коррозия, осаждение солей
The works devoted to the processing of the pulp and paper industry wastes via environmentally
benign supercritical water conversion are analyzed. The high efficiency of production
of combustible gases above 873 K is demonstrated. Mechanisms of the conjugate
conversion of organic and mineral components of wastes are considered. The main obstacles
to the industrial implementation of the processes under consideration, such as plugging
of pi pelines, salt deposition and corrosion of structural materials, are discussed.
doi:10.34984/SCFTP.2018.13.3.002
Key words: сверхкритический диоксид углерода, биоматериалы, стерилизация, децеллюляризация, импрегнация, тканевая инженерия
In the review, the key aspects to the modification of biocompatible materials are
described based on treatment in supercritical carbon dioxide medium. Main trends in
the area include the fabrication of three-dimensional scaffolds, sterilization of medical
devices, mammalian tissue decellularization and material impregnation with bio-active
molecules. Due to non-destructive action of the supercritical carbon dioxide medium
towards extracellular matrix’s architecture, preservation of inherent biomechanical
properties and structure of treated biomaterials, avoidance of purification and postprocessing
steps, the technique is considered as a powerful tool to solve the urgent
issues of biomaterials science.
doi:10.34984/SCFTP.2018.13.3.003
Spin Probe Method for Diagnostics of Polyster Porous Matrixes Formed in Supercritical Carbon Dioxide
Key words: пористые полимерные материалы, алифатические полиэфиры, нитроксильные радикалы, электронный парамагнитный резонанс
The review is devoted to the electron paramagnetic resonance (EPR) studies of porous
polymer materials (matrixes) obtained from aliphatic polyesters and doped with
paramagnetic biologically active substances by means of supercritical fluid technologies.
Particular attention is paid to the possibilities of the EPR-spectroscopy for establishing
the regularities of the formation of the matrixes, the subsequent characterization of
the materials obtained, and also the features of the dopant release to aqueous solutions
<i>in vitro</i>.
doi:10.34984/SCFTP.2018.13.3.004
Key words: сверхкритическая флюидная хроматография, препаративное разделение, 1,2-аминоспирты, фармацевтические субстанции
Preparative separation of enantiomers is one of the most common applications of
supercritical fluid technologies in modern production practice. In this review, methods
for the preparative separation of enantiomers of pharmaceutical substances in which
a 1,2-amino alcohol moiety is present are provided, using supercritical fluid
chromatography. The types of chiral phases used in supercritical fluid chromatography
are also briefly considered.
doi:10.34984/SCFTP.2018.13.3.005