Key words: нанокомпозиты, однослойные углеродные нанотрубки, суспензии, сверхкритическая импрегнация, полиметилметакрилат, сверхкритический диоксид углерода, спектроскопия комбинационного рассеяния, термогравиметрия, дифференциальная сканирующая калориметрия
A technique is described for dispersing single-walled carbon nanotubes to obtain stable
suspensions with a high concentration of individual nanotubes in 2-pyrrolidone. The
resulting suspensions were investigated using Raman spectroscopy and were used to
modify poly(methylmethacrylate) samples with average molecular weights 15000 and
996000 g/mol by impregnation in supercritical carbon dioxide. The thermal properties of
the obtained composite materials are studied. It is shown that the glass transition
temperatures of the samples are increased with comparison with the initial polymers.
Glass transition temperatures of composites increased by 26°С and 32°С for PMMA
with an average molecular weight of 15000 and 996000 g/mol accordingly.
doi:10.34984/SCFTP.2021.16.1.001
Key words: оксид цинка, холодное спекание, рекристаллизация, твердофазная подвижность в водной среде, распределение кристаллов по размерам, коалесценция, поверхностное растекание, компоненты распределения кристаллов по размерам
An effect of mechanical pressure on the crystal size distribution during the treatment of
zinc oxide in an aqueous medium in the presence of zinc acetate or ammonium chloride as
activating additives was studied by analyzing scanning electron microscopy images. The
results of ZnO cold sintering at 220—296 °C and its thermovaporous treatment (TVT)
without applying mechanical pressure in an autoclave under similar conditions were
compared. It was concluded that due to the presence of the additives in an aqueous
medium, the hydration of the structure increased and the solid-phase mobility was activated,
leading to the redistribution of the mass of crystals. Mechanical pressure during the cold
sintering enhanced the effect of solid-phase mobility activation and led to the predominance
of crystal coalescence in mass transfer. During the TVT with no mechanical pressure
applied, surface spreading as the mass transfer mechanism prevailed. A scheme illustrating
the effect of the aqueous medium on the mass transfer during the recrystallization of
ZnO was proposed.
doi:10.34984/SCFTP.2021.16.1.002
Key words: сверхкритический диоксид углерода, спектроскопия электронного парамагнитного резонанса, оптическая спектроскопия, PDLLA, спиновый зонд 2,2,5,5-тетраметил-4-фенил-3-имидазолин-1-оксил-3-оксид
The optical spectroscopy and EPR spectroscopy methods were used together for the first
time to quantitatively describe the release of a nitroxyl probe from poly-D,L-lactide (PDLLA)
films into a phosphate buffer solution. The bifunctional probe 2,2,5,5-tetramethyl-4-phenyl-
3-imidazoline-1-oxyl-3-oxide (IMNO) contains a paramagnetic nitroxyl fragment and has
a high extinction coefficient in the UV spectrum. Polymer films were obtained from porous
matrices based on PDLLA, formed and doped with IMNO in a supercritical CO<sub>2</sub> environment.
It has been established that the combined use of spectrophotometry and EPR spectroscopy
is promising for obtaining more detailed information on the processes of the release of
probes from PDLLA films, the duration of which does not exceed three weeks.
doi:10.34984/SCFTP.2021.16.1.003
Key words: водорастворимые полимеры, сверхкритический диоксид углерода, экстракция, степень извлечения, бензойная кислота, кофеин, тиофен
This work presents the experimental study results of the benzoic acid, caffeine, and thiophene
recovery from polymer phases by supercritical fluid extraction. The extraction efficiency
dependences of the studied compounds on the conditions of fluid existence — temperature, and
pressure were obtained. It has been shown that benzoic acid, caffeine, and thiophene are extracted
in one step into supercritical CO<sup>2</sup> with the extraction degree of 43, 48.5, and 84 % respectively.
doi:10.34984/SCFTP.2021.16.1.004
Key words: биомасса, отходы АПК, сверхкритические условия, реактор идеального смешения, экология, энергия
The efficiency of processing organic liquid and solid wastes of the agro-industrial complex
in supercritical conditions is shown. The conversion is at least 99,7 %. The dependence of
the volume of a continuous reactor on the content of organic substances has been
established. High rates of oxidation of waste in supercritical conditions make it possible
to reduce the volume of the reactor (up to 100—140 l) with a capacity of up to 100 kg
of waste per hour. The heat density of the reactor can reach 730 kW/m<sup>3</sup>.
doi:10.34984/SCFTP.2021.16.1.005
Key words: статистическая физика, критические явления, релеевское рассеяние света
For the first time, the temperature dependence of the density variance and the correlation
length of critical density fluctuations is determined from the experimental data on small-angle
light scattering by critical CO<sub>2</sub>. It is found that at critical density of CO<sub>2</sub> in the temperature
range 10<sup>-8</sup> <i>T<sub>c</sub></i> < |<i>T - T<sub>c</sub></i>| < 10<sup>-4</sup> <i>T<sub>c</sub></i> (where <i>T<sub>c</sub></i> is the critical temperature) the correlation
length of density fluctuations decreases by 20 % as the critical point is approached. The
value of density variance shows no power-law-type divergence: it remains practically constant
in the temperature ranges <i>T > T<sub>c</sub></i> and <i>T < T<sub>c</sub></i>, but undergoes a 25 % stepwise change when
passing through the critical point, likely due to the peculiarities of the experiment setting up.
doi:10.34984/SCFTP.2021.16.1.006
Key words: суб- и сверхкритическая флюидная экстракция, этанол, трутовый гриб, Fomes fomentarius, полифенолы, антирадикальная активность
The process of sub- and supercritical fluid extraction with ethanol of the fruiting body
biomass of the tinder fungus <i>F. fomentarius</i> was studied. The evaluation of the extraction
conditions (temperature, pressure and duration) for the yield of the solid extract, phenolic
compounds and steroids was carried out. It was found that sub- and supercritical extraction
was more efficient in comparison with traditional methods of biologically active substances
isolation (maceration and percolation). The yield of the solid extract reaches 43 wt.%.
The content of phenolic compounds in the extract was up to 50 wt. %. It was shown that
the extracts have high antiradical activity (up to 350 μmol trolox-equiv/g). The positive
correlation between the antiradical activity of the extracts and the content of phenolic
compounds in them was established.
doi:10.34984/SCFTP.2021.16.2.002
Key words: левофлоксацин, растворимость, сверхкритический диоксид углерода, сверхкритический трифторметан
The solubility of levofloxacin (LFC) in supercritical carbon dioxide and trifluoromethane
was measured in the pressure range 10—30 MPa at temperatures of 323 K and 373 K.
Solubility was determined by changing the weight of the LFC powder held in the
supercritical fluid (SC) at given temperature and pressure. The obtained solubility value
of LFC in SC-trifluoromethane reaches a value (8.3 ± 0.3) · 10<sup>-5</sup>
mole fractions at 30 MPa and 373 K.
Solubility of LFC in SC-trifluoromethane at a pressure of 30 MPa and a
temperature of 323 K ((55.7 ± 0.3) · 10<sup>-6</sup> mole fractions), almost by an order of magnitude
exceeds the solubility in SC carbon dioxide ((5.9 ± 0.3) · 10<sup>-6</sup> under the same conditions.
The obtained results are the basis for further development and optimization of processes
of supercritical fluid micronization of LFC and other antibiotics of fluoroquinolone
group without partici pation of liquid co-solvent.
doi:10.34984/SCFTP.2021.16.2.003
Key words: субкритическая вода, экстракция, листья оливы (<i>Olea europaea</i> L.), полифенолы, анти-ацетилхолинэстеразная активность, метод Эллмана, болезнь Альцгеймера
The content of secondary plant metabolites (the sum of polyphenolic compounds and
flavonoids) obtained by subcritical water (SubCW) and traditional extraction by wateralcoholic
mixture from olive (<i>Olea europaea</i>) leaves was studied, and their
acetylcholinesterase (anti-AChE) activity was determined and characterized by the IC<sub>50</sub>
value — the concentration of olive leaf extracts, which leads to 50 % inhibition of the
activity of the acetylcholinesterase (AChE) enzyme. It was shown that the content of
polyphenolic compounds and anti-AChE activity of extracts depend on the used
extraction method. The SubCW extract obtained at 220 °C contains the maximum
amount of polyphenolic compounds and demonstrates the highest anti-AChE activity
(IC<sub>50</sub> = 0.4 mg/ml). The least active in relation to the inhibition of the AChE enzyme
was found to be the extract obtained by traditional aqueous-alcoholic extraction
(IC<sub>50</sub> = 3.6 mg/ml). The results obtained show the promise of using subcritical water
to obtain extracts with a high content of polyphenols for the development of
pharmaceutical products and food additives for the prevention and treatment of various
neurodegenerative diseases, such as Alzheimer’s disease, from the waste of olive oil
production (olive leaves).
doi:10.34984/SCFTP.2021.16.2.004
Key words: конифериловый спирт, водные растворы, нормальные и сверхкритические условия, молекулярно-динамическое моделирование, агломерация
The method of classical molecular dynamics was used to model the structure of aqueous
solutions of coniferyl alcohol (CA) in the NVT-ensemble at a solute concentration of
2 wt. %, at densities corresponding to normal (<i>T</i> = 298 K, <i>P</i> = 0.1 MPa) and supercritical
(<i>T</i> = 673 K, <i>P</i> = 23 MPa) conditions of the solvent. It was found that under normal
conditions in the system under consideration, all CA molecules are united into one
agglomerate. Under supercritical conditions, single CA molecules predominate in the
structure of an aqueous-organic solution.
doi:10.34984/SCFTP.2021.16.2.005
Key words: асфальтосмолопарафиновые отложения, нефтяные скважины, экстракция, пропан, бутан, фазовое равновесие, сверхкритический флюид
The results of an experimental study of the characteristics of phase equilibria for the
systems «hexadecane — propane/butane» and «sulfur — propane/butane» are presented.
The data on the kinetics of extraction of hydrocarbons from asphalt-resin-paraffin
deposits are presented. It has been established that it is preferable to use the SCFextraction
process (as opposed to the liquid one) in relation to the process of cleaning
the wellhead of oil wells from asphalt-resin-paraffin deposits.
doi:10.34984/SCFTP.2021.16.2.006
Key words: ацетон, альдольная конденсация, станнат стронция, SrSnO<sub>3</sub>, сверхкритические условия
Aldol condensation of acetone on strontium stannate isstudied at a temperature of 250—
400 °C and a pressure of 2.5 and 12.5 MPa. The main reaction products are mesityl oxide
and isophorone. It is shown that the SrSnO<sub>3</sub> catalyst is stable under supercritical conditions
and its productivity with respect to mesityl oxide isomers at 350 °C and 12.5 MPa equals
9 g · h<sup>-1</sup>· g<sub>cat</sub><sup>-1</sup>,
which is higher than in the gas phase.
doi:10.34984/SCFTP.2021.16.2.007
Key words: ЯМР с контролем давления, лидокаин, 2D NOESY, малые молекулы, DFT, пространственная структура
The main goal of our research was to obtain information on the spatial structure of
lidocaine in SC-CO<sub>2</sub>. The preferred conformations of this compound in SC-CO<sub>2</sub> (at
70 °C, 20.0 MPa) were determined by two dimensional technique nuclear Overhauser
effect spectroscopy (2D NOESY) and quantum chemistry calculation (DFT). This data
can be used to calculation of parameters of state for micronization processing by RESS.
doi:10.34984/SCFTP.2021.16.2.008
Key words: сверхкритический CO<sub>2</sub>, фазовое равновесие, растворимость, диспергирование по методу SEDS, кристаллизация
The paper presents the results of joint dispersion of a mixture of low-pressure polyethylene
(HDPE) and synthetic ethylene-propylene ternary rubber (EPDM) in the pressure range of
8.0—25 MPa at temperatures of 313 and 333 K using the SEDS method (Solution Enhanced
Dispersion by Supercritical Fluids). The influence of thermodynamic parameters on the morphology
of the obtained particles is established. Thermogravimetric studies and comparative analysis
of polymers obtained by mixing in a melt and using the SEDS method were carried out.
doi:10.34984/SCFTP.2021.16.2.009
Key words: быстрое расширение сверхкритических суспензий, углеродные нанотрубки, диспергирование
The influence of temperature, pressure, dispersion medium, type of single-walled carbon
nanotubes (CNTs) on the degree of CNTs deagglomeration after rapid expansion of
supercritical suspensions (RESS) treatment was studied. It is shown by Raman
spectroscopy and scanning electron microscopy that the highest degree of dispersion in
the RESS process is provided by the use of nitrogen.
doi:10.34984/SCFTP.2021.16.2.010
Key words: сверхкритическая флюидная экстракция, модель сжимающегося ядра, полидисперсный зернистый слой, байесовский метод, метод МонтеКарло для марковских цепей
The apparent process parameters (diffusion coefficient, saturation concentration of oil in
the solvent, initial oil content in the raw material) were inferred using the Bayesian
approach and the Monte-Carlo method for Markov chains for the process of supercritical
fluid extraction (SFE) of oil from ground plant material with high initial oil content.
The shrinking core approach was used for data interpretation. The accuracy of parameter
inference is substantially increased when at least two experiments corresponding to fine
and coarse grinding are included in the design of experiment
doi:10.34984/SCFTP.2021.16.2.011
Key words: аморфный полилактид, диоксид углерода, вспенивание, нуклеация
The features of the formation, development and stabilization of the structure of foamed
amorphous D,L-polylactide during slow (quasi-isothermal) and fast (quasi-adiabatic)
pressure relief of supercritical carbon dioxide used as a plasticizing/foaming agent have
been investigated. The following regularities have been established: 1) the values of the
foam expansion factor during quasi-adiabatic depressurization are significantly lower
than in the quasi-isothermal regime due to significant dissi pation of the internal energy
of the «polymer—foaming agent» system due to internal friction in the system; 2) an
expansion-collapse effect is observed with quasi-isothermal foaming; 3) at an intermediate
stage between nucleation and intensive development of foam, the growth of pore nuclei
in the plasticized polymer has a self-similar character. The results obtained are significant
for the selection of foaming modes that provide the required structural characteristics of
the synthesized highly porous matrices intended for use in regenerative medicine and
tissue engineering.
doi:10.34984/SCFTP.2021.16.2.012
Key words: арктические бурые водоросли, целлюлоза, сверхкритическая сушка, лиофилизация, структура, пористость
The article presents a study of the influence of three methods of drying cellulose of
Arctic brown algae (vacuum drying, freeze drying and supercritical drying) on the
physicochemical properties of the target product. Freeze-died and supercritically dried
algal celluloses have lower thermal stability due predominance of the metastable Iб
phase, degree of crystallinity of 48—69% and fibrillar surface. Freeze-dried celluloses,
and especially supercritically dried, have a larger specific surface area (up to 186 m<sup>2</sup>/g), a
developed mesoporous structure with an average pore diameter of 13,81—14,81 nm.
doi:10.34984/SCFTP.2021.16.2.013
Key words: ЯМР с контролем давления, СК-CO<sub>2</sub>, мефенамовая кислота, 2D NOESY, малые молекулы, пространственная структура
The spatial structure of mefenamic acid molecule was investigated by the 2D NOESY in
SC-CO<sub>2</sub> with DMSO (25% and 10 %). The results will be used to determine the optimal
parameters of state for the micronization processing by GAS technique.
doi:10.34984/SCFTP.2021.16.3.001