V. I. Anikeev

The thermal isomerization of terpene compounds in supercritical alcohols

The experimental data obtained were used to construct a kinetic model of the isomerization of α-pinene in supercritical ethanol. The model took into account the influence of both temperature and pressure on the rate and selectivity of the reaction.

Calculations of phase equilibria for mixtures of triglycerides, fatty acids, and their esters in lower alcohols

The objects of study were mixtures containing triglycerides and lower alcohols and also the products of the transesterification of triglycerides, glycerol and fatty acid esters. The Redlich-Kwong-Soave equation of state was used as a thermodynamic model for the phase state of the selected mixtures over wide temperature, pressure, and composition ranges. Group methods were applied to determine the critical parameters of pure substances and their acentric factors. The parameters obtained were used to calculate the phase diagrams and critical parameters of mixtures containing triglycerides and lower alcohols and the products of the transesterification of triglycerides, glycerol and fatty acid esters, at various alcohol/oil ratios. The conditions of triglyceride transesterification in various lower alcohols providing the supercritical state of reaction mixtures were selected.

Modeling of the Oxidation of Organic Compounds in Supercritical Water

A system for oxidation of organic impurities in supercritical water is proposed. Models are formulated and calculations are performed to determine the characteristics of the main apparatuses of the system, namely, heat exchangers, a chemical reactor, and a separator. The models take into account specific features of processes under supercritical conditions, specifically, the changes in the thermodynamic properties (enthalpy, specific heat, critical parameters) of the reaction mixtures with changes in pressure and temperature, and also the variations of the compositions of the mixtures along the lengths of the apparatuses. The thermodynamic properties are calculated by methods of nonequilibrium thermodynamics. A numerical analysis is performed of one of the variants of a system for acetic acid oxidation by oxygen in supercritical water, which can be a prototype of a pilot plant. The fuel is chosen to be an aqueous methanol solution, and the oxidant is taken to be hydrogen peroxide. Replacement of the reactant, the fuel, or the oxidant does not fundamentally change the methods for calculating the characteristics of the apparatuses and the entire system.

The thermolysis of α-pinene and verbenone epoxides in supercritical solvents

Thermal transformations of α-pinene and verbenone epoxides were studied in supercritical solvents with complex compositions, including CO2, lower alcohols (ethanol and isopropanol), and water, over the temperature and pressure ranges 387–575 K and 135–215 atm. The main product from α-pinene epoxide in a supercritical solvent containing water was campholenic aldehyde and pinocamphone; the total content of these products in the reaction mixture was 80%. Suggestions concerning the mechanism of the thermal isomerization of α-pinene epoxide depending on the acidity of supercritical solvents were made. The direction of verbenone epoxide transformations was independent of the presence of water in the mixture. The main identified products were ketoalcohols with para-menthane and camphane frameworks.

Phenol oxidation in supercritical water in a well-stirred continuous reactor

A well-stirred reactor for phenol and acetic acid oxidation in supercritical water is considered. A mathematical model of an adiabatic reactor is formulated. A numerical algorithm for solving the model equations using the homotopy method is developed. The model takes into account specific features of processes under supercritical conditions, namely, the changes in the thermodynamic properties (enthalpy, heat capacity, and critical parameters) of mixtures with a change in pressure and temperature. The thermodynamic properties are calculated by methods of nonideal thermodynamics. It is shown that there is a multiplicity of steady-state solutions at various reactor performances. The results of numerical analysis of the effect of the inlet flow temperature, the amount of methanol (fuel) fed, and the total pressure on the reactor performance are presented.

Calculating the thermodynamic characteristics of the stepwise transesterification of simple triglycerides

Thermodynamic data for mono- and diglycerides of palmitic, oleic, and linoleic fatty acids participating in the stepwise transesterification reaction of the corresponding simple triglycerides in methanol are calculated. The obtained thermodynamic parameters allow us to calculate the chemical equilibrium and the equilibrium composition of the products of the stepwise transesterification reaction of fatty acid triglycerides with supercritical methanol.

Hydrothermal synthesis of metal oxide nano- and microparticles in supercritical water

Hydrothermal syntheses of nano- and microparticles of metal oxides of two types, LiMOn (LiCoO2, LiNiO2, LiZnO2, and LiCuO2) and MOn (Ga2O3, CeO2) were performed under continuous conditions in a tubular reactor with the use of supercritical water. An important role in the synthesis of nanoparticles and the reproducibility of the results was played by the conditions of mixing of supercritical water and precursor solution flows. The morphology and composition of synthesized compounds were studied by scanning electron microscopy and X-ray diffraction. The syntheses of LiCoO2, LiNiO2, LiZnO2, LiCuO2, Ga2O3, and CeO2 were most successful.

Calculation of spinodal line and critical point of a mixture

A simple form of two equations that describe the spinodal line on theT-P plane and the critical point of a multicomponent mixture is suggested. This form is easy to implement numerically. An effective solution algorithm for model equations that is based on the parameter continuation method is proposed. Results of computation are compared with the literature data obtained from other models, as well as with experiments. An example of parameter calculation for benzene hydrogénation in supercritical CO2 is given.

Transesterification of Rapeseed Oil in Supercritical Methanol in a Flow Reactor

Transesterification reactions of rapeseed oil in supercritical methanol in a flow reactor over a wide range of variation of the methanol/oil ratio, pressure, and contact time are studied. Conditions ensuring selectivity and a high degree of rapeseed oil conversion are found. Experiments to study this reaction in the presence of zeolite heterogeneous catalyst are performed.

Oxidation of α-pinene by atmospheric oxygen in the supercritical CO2—ethyl acetate system in the presence of Co(II) complexes

The reactivity of monoterpene α-pinene in a flow reactor in the presence of cobalt catalyst in a complex supercritical solvent consisting of CO2 and ethyl acetate is studied over the temperature range of 190–320°C and a pressure range of 110–125 atm. It was found that the main isomerization products include compounds with bicyclo[2.2.1]heptane and p-menthane backbones; the reaction is accompanied by partial racemization. The formation of oxidation products is observed in the presence of air, with epoxydation rather than allylic oxidation being the predominant process at the first stage. The oxidized products (campholenic aldehyde, verbenone, pinocamphone) are shown to be formed with a high enantioselectivity; the formation of acetoxylation products is observed at temperatures above 200°C.