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Values of Kamlet–Taft solvatochromic parameters and Dimroth–Reichardt energy are determined via UV spectroscopy for carbon dioxide–alcohol (ethanol, isopropanol) mixtures at temperatures of 295−353 K and pressures of 100−300 atm in a wide range of component ratios.

Thermogravimetric analysis (TGA) is used to study the thermophysical properties of three ionic liquids with 1-butyl-3-methylimidazolium cation. The temperatures and enthalpies of melting and thermal decomposition are determined, and the IR spectra of gaseous products of thermal decomposition are studied. The relationship between the structure of compounds and their thermochemical characteristics is considered.

—The solubility of iodine in sub- and supercritical carbon dioxide was studied using a flow-type extraction setup. It is shown that at 20–80°C and 60–350 atm, the solubility of iodine increases at rising temperature and CO2 pressure and the mole fraction of iodine in its saturated solution ranges from 0.12 × 10–3 to 1.42 × 10–3.

—The optimum parameters of oil extraction from the processed fruit of mountain ash (Sorbus aucuparia) were determined using the second-order rotable composite design: pressure 321 atm, temperature 85°С, and extraction time 72 min. The predicted yield of oil expected under these conditions (9.06%) was confirmed experimentally (9.02%). The antioxidant activity (AOA); fatty acid composition; and acid, iodine, and saponification numbers of the oil extract were determined. For comparison, the oil obtained by extraction with n-hexane was used.

The thermal stability of 1,4-dioxane below and above its critical temperature (300–500°C) and at different fluid densities was studied. It was established that at 300–350°C dioxane is thermally stable during 80–100 min; at higher temperatures during this time, uncontrolled growth of pressure begins in the system due to the thermal cracking of dioxane. The analysis of he liquid and gas phases that remained in the reactor after heat treatment of dioxane showed the presence of a wide range of products.

—The condensation of acetone under supercritical conditions was studied at different temperatures, pressures, and densities in a static mode. The high yield of mesitylene under the given conditions and its easy isolation from the reaction mixture made it possible to propose a new method for its preparation.

Temperature dependences of density and dynamic viscosity are obtained for the ionic liquid 1-butyl-3-methylimidazolium methyl sulfate in the temperature range of 298–328 K. Absorption bands in the IR and UV regions of the spectrum are identified and the structure of ionic liquid is characterized using the gap model.

The supercritical fluid extraction of chlorophylls and carotenoids from marine algae Fucus vesiculosus and Laminaria digitata with carbon dioxide was studied. Complete extraction of carotenoids with carbon dioxide was achieved at a pressure of 250 atm and a temperature of 80°C after 20 min in the absence of a cosolvent. Extraction of chlorophylls in high contents required the use of a polar co-solvent (ethanol, 10–15 vol %) or extraction time increased to 50–90 min (at a co-solvent consumption of

Sixteen lignin related aromatic compounds formed by the thermal degradation of lignin and being potentially valuable products of the processing of renewable raw materials were studied using differential scanning calorimetry. The temperatures, enthalpies, and entropies of melting were determined. The temperature dependences of isobaric heat capacities for the studied compounds were obtained. The relationship between the structures of the lignin related compounds and their thermochemical properties is considered.

The effect of process parameters on the efficiency of carotenes extraction from carrot samples by supercritical CO2 is studied. The degree of carotenes extraction increases to approximately 35% at rising temperature (in the range between 60 and 80°C) and pressure (up to 350 atm) at a close to stable fraction of β-carotene (64–70%) in the obtained extracts.

The possibility of cellulose diacetate production by direct acetylation of sulfite pulp with acetic anhydride in supercritical carbon dioxide (SC CO2) is demonstrated. Optimum acetic anhydride to cellulose ratio and parameters of SC CO2 are selected.

Changes in the content of lignin functional groups during low-temperature delignification under the action of hydrogen peroxide in supercritical (SC) CO2 in the preparation of fibrous cellulose half-finished product were considered. The action of the oxidizer caused changes in the molecular weight characteristics of lignins. The experimental data showed the occurrence of both oxidation and substitution processes. Oxidation in SC CO2 resulted in the formation of water- and alkali-soluble medium- and low-oxidized lignins because of decreased oxidizer consumption.

The influence of pressure on the parameters of low-temperature oxidative delignification of firry wood in supercritical carbon dioxide under the action of hydrogen peroxide is described. The chemical composition of the cellulose half-finished products is characterized.

Characteristic IR and UV absorption bands, as well as oxidation half-wave potential on a platinum disc electrode in the cyclic mode were determined for the low-temperature hydrophilic ionic liquid 1-butyl-3-methylimidazolium acetate. Temperature dependences of the refractive index, density, and ansolute viscosity were determined in the temperature range 298–328 K. The activation energy of viscous flow was calculated.

It is shown that cellulose can be acetylated with acetic anhydride in supercritical carbon dioxide in the absence of traditional catalysts, toxic solvents, and dilutants. As substrates, three cellulose samples were tested: sulfite and sulfate cellulose and cellulose obtained by low-temperature delignification in a supercritical carbon dioxide medium. The chemical composition of the cellulose diacetate product is characterized.

The hydrodynamic behavior of lignin in a dimethylsulfoxide-water mixture have been studied at the temperature range of 20–60°C and at a water content from 0 to 30%. The rise of temperature was shown to deteriorate the quality of the solvent; i.e., the system under investigation belongs to systems with a lower critical solution temperature. The dimension of lignin particles in the mixed solvent decreases with an increasing proportion of water in the system.

Interaction of lignin with dimethyl formamide, dimethyl sulfoxide, and dioxane was studied by calorimetry. Concentration dependences of the enthalpy of interaction between lignin and aprotic solvents were obtained.