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2017, №3

pp. 3-19

Articles

Key words: heavy oil, supercritical water-oxygen fluid, activated carbon, oxidation, heat release

The composition of oily fractions (OFs) obtained at the heavy sulfur-rich oil conversion is studied by means of physical and chemical methods of analysis. The oil was supplied from the top into the vertical tubular reactor packed with activated carbon (AC), where supercritical water-oxygen fluid was pumped from the bottom through the AC bed. The experiment was performed at 30 MPa, temperature of upper, middle and bottom parts of the reactor equal to 673, 723 and 723 K, variable flow rate of oxygen (0—3.5 g/min) and constant flow rate of oil and water (4 and 6 g/min, respectively). Based on the temporal trends in the reactor wall temperature and the power of resistance heaters it is revealed that due to heat generation during the combustion of oil high-molecular components, accumulated in the AC bed, the conversion process occurs in autothermal mode. The movement of the combustion front along the reactor axis is detected. It is shown that isoprenoids and normal alkanes, 1-alkyl-2,3,6- trimethylbenzenes, alkyl-derivatives of benzo- and dibenzothiophenes are the main components of the crude oil OF. The yield of OFs, whose portion in the liquid products exceeds 90 %, has an extreme dependence on the oxygen flow rate. As the latter increases and the temperature of the reaction mixture rises due to a heat generation upon combustion, the relative content of bi- and tricyclic aromatic hydrocarbons alkylderivatives, as well as benzo- and dibenzothiophenes in the OFs of conversion products increases too. The content of fractions boiling at T < 493 K in the OFs of the conversion product increases by 2—3 times compared to the crude oil OF.

2017, №3

pp. 20-31

Articles

Key words: film composite, cadmium selenide, nanocrystalline silicon, diffusion implantation, luminescent properties, fiber matrix

A method to produce film composites based on the tetrafluoroethylene-vinylidene fluoride fiber copolymer using diffusion implantation of nanoparticles dispersed in a supercritical (SC) carbon dioxide CO2 medium has been developed. At the final stage of the formation of such materials, a cold or hot pressing of impregnated porous films is applied. The effect of treatment in SC-CO2 on the surface structure of pressed films is discussed. The materials containing nanoparticles of semiconductors (cadmium selenide and nanocrystalline silicon) whose radiation covers a range of 500—1000 nm are obtained. Their luminescent characteristics under the laser excitation (irradiation wavelength 405 nm) are presented.

2017, №3

pp. 32-39

Articles

Key words: aerosilica, adsorption of carbon dioxide, amino-functionalization

Mesoporous silica gel samples, including those functionalized with amino groups, were prepared using sol-gel synthesis followed by drying in supercritical carbon dioxide. Relationshi ps between the conditions of preparation and modification of the silica sample and their textural and adsorptive properties are established. The obtained porous materials are considered as promising adsorbents for the recovery of carbon dioxide from gas media.

2017, №3

pp. 40-49

Articles

Polystyrene Treatment in Sub- and Supercritical Media

D.Yu. Zalepugin, N.A. Tilkunova, I.V. Chernyshova, M.I. Vlasov.

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Key words: polymers, porosity, supercritical fluids, subcritical freons, carbon dioxide

For the first time the treatment of polystyrene in sub- and supercritical freon media in comparison with supercritical carbon dioxide was studied. Subcritical freon R22 can more efficiently saturate polystyrene than subcritical freon R410а and supercritical freon R23 and carbon dioxide. The subsequent heating of polystyrene samples saturated with R22 freon leads to the formation of the polymer with connected porous structure and average pore size up to 250 μm. The results obtained can be used in the development of technologies for porous polystyrene production.

2017, №3

pp. 50-69

Articles

Key words: supercritical fluids, micronization, polymerization, polymer microparticles, functional powder coatings, market forecast

This review analyzes the studies and developments of technologies based on the use of supercritical fluids for micronization of polymer particles and formation of efficient powder polymer coatings. Potential advantages of supercritical fluid technologies that combine different stages of powder coating formation in a unified flowsheet are considered. Possible further trends in the scientific and engineering research are identified. The growth of powder coatings global market in perspective to the year 2020 is forecasted.

2017, №3

pp. 70-81

Articles

Supercritical Fluid Treatment of Three-Dimensional Hydrogel Matrixes Synthesized from Allilchitosan Using Laser Stereolithography

A.E. Lazhko, K.N. Bardakova, B.S. Shavkuta, S.N. Churbanov, M.A. Markov, T.A. Akopova, O.O. Parenago, A.M. Grigoryev, P.S. Timashev, V.V. Lunin, V.N. Bagratashvili.

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Key words: structured hydrogels, matrixes, laser stereolithography, supercritical carbon dioxide

Hydrogel matrix structures (matrixes) based on the allyl-substituted chitosan derivatives are formed using the laser stereolithography. The effects of their processing in the supercritical carbon dioxide (SC-CO2) onto the surface polarity and mechanical characteristics are studied. It is found that such treatment of matrixes in the flow regime increases the mechanical strength due to an efficient extraction of low molecular weight components and oligomers from the material. In addition, the processing in the SC-CO2 decreases the surface polarity and, as a result, improves the biocompatibility of the material. The hydrogel matrixes treated in the SC-CO2 have no cytotoxic effect and are prospective materials for tissue engineering.