Vol 12, No 7 (2018)

The composition of oil fractions (OFs) obtained via the conversion of heavy sulfur-rich petroleum is studied with physicochemical methods. Petroleum is supplied to the upper part of a vertical tubular reactor packed with activated carbon (AC), through which a supercritical water-oxygen fluid is pumped. The experiment is carried out under the following conditions: pressure 30 MPa; temperatures in the upper, middle, and lower parts of the reactor of 673, 723, and 723 K, respectively; and the flow rates of oxygen, petroleum, and water of 0–3.5, 4, and 6 g/min, respectively. Time dependences between the wall temperature of the reactor and power of ohmic heaters show that the autothermal conversion regime is achieved due to heat release during the combustion of high-molecular petroleum components accumulated in the AC bed. The movement of a combustion front along the reactor axis is found. Isoprenoid and normal alkanes, 1-alkyl-2,3,6-trimethylbenzenes, and alkyl derivatives of benzothiophenes and dibenzothiophenes are the main components of OFs of the initial petroleum. A yield of OFs, whose content in the liquid products exceeds 90%, has an extreme dependence on the oxygen flow rate. An increase in the oxygen flow rate (and, consequently, an increase in temperature of the reaction mixture due to heat release during combustion) leads to an increase in the content of alkyl derivatives of bicyclic and tricyclic aromatic hydrocarbons, as well as benzothiophenes and dibenzothiophenes in OFs of the products. The content of components boiling at T < 493 K in OFs of the products increases 2–3-fold in comparison with those of the initial petroleum.

Mesoporous silicagels, including samples functionalized with amino groups, have been synthesized by the sol–gel method with drying in supercritical carbon dioxide. The textural and adsorption properties of SiO₂ are established to depend on synthesis and modification conditions. The synthesized porous materials are considered promising adsorbents for the recovery of carbon dioxide from gas media.

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

An experimental strategy for determining the coil–globule transition parameters of a polymer chain in supercritical carbon dioxide has been developed on the basis of a gas-dynamic model of the expansion of a pulse jet of a van der Waals gas [1]. Taking into account the behavior of CO₂ in the near-critical region and isentropic conditions of the jet expansion process, starting conditions that arise in the nozzle and correspond to the proposed model are determined. The design of the experiment (geometrical and size parameters of the key components of the equipment, pulse valve duration, etc.) is developed. Possible options for carrying out the experiment and processing the experimental data are discussed. Calculation procedures for the case corresponding to the experimental conditions described in [2, 3] are given as an example.

Three chiral chromatography stationary phases based on amylose and cellulose were tested for the supercritical fluid chromatography separation of antiasthmatic drug salbutamol enantiomers. A cellulose tris- 3-chloro-4-methylphenylcarbamate stationary phase provided the highest selectivity for this separation. The optimization of mobile phase composition allowed us to maximize the selectivity coefficient and to minimize the peak asymmetry factors. A successful salbutamol enantiomer separation is achieved at moderate modifier fraction (10–15 vol %) in the mobile phase on this column. Amine additives are necessary to suppress peak tailing. Among three tested amines isopropylamine gives the most symmetrical peaks along with the highest enantioselectivity.

Taking into consideration the fact that the variance of the density of critical CO₂ is small, a molecular model of critical CO₂ is formulated for the first time. Based on it, the intensity of Rayleigh light scattering is calculated. The expression for the Rayleigh scattering intensity differs from the Ornstein–Zernike formula by a more complex dependence on the scattering angle and on the diffraction parameter. The scattering process shows the features necessary for the critical opalescence. For the first time, the contribution of thermal motion of molecules to Rayleigh light scattering on a critical medium is explicitly reckoned.