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A two-parameter cubic Soave−Redlich−Kwong (SRK) equation of state with modified binary interaction coefficients has been used for phase equilibrium calculations of multicomponent systems under supercritical and near-supercritical conditions. Example calculations of the phase behavior of multicomponent reaction mixtures are presented and used to illustrate the increased accuracy of the SRK equation of state with the new binary interaction coefficients. The homotopy continuation method was adapted for the solution of the model equations by using temperature and pressure as continuation parameters. The effective models and algorithms thus created are used for phase state calculations, localization of the critical point of multicomponent mixtures, studies of phase properties near the critical point, and determination of parameter regions that are of practical importance for process performance under supercritical conditions. The problems of existence and uniqueness of a solution are studied. A new method for solving equations for the critical phase is suggested. Many examples of the calculation of phase diagrams of mixtures with a supercritical solvent are presented and the results compared with the reference data. Thermodynamic and macrokinetic models of the Fischer−Tropsch (FT) reaction are developed and used for the calculation of reactor performance.

Thermodynamic data (critical parameters, enthalpy, entropy) were calculated for the monoglycerides, diglycerides, and triglycerides of fatty acids (palmitic, oleic and linoleic), free fatty acids, and methyl esters of fatty acids, which are involved in the transesterification of vegetable oils with lower alcohols. Phase diagrams of the reaction mixtures were calculated and reaction conditions providing supercritical state of the reaction mixture were selected for transesterification of triglycerides in various lower alcohols. Chemical equilibrium of the methanol transesterification of simple and mixed fatty acid triglycerides was studied in a wide range of temperatures, pressures, and ratios of initial components, including the region of supercritical state of the reaction mixture. Calculation of the phase equilibrium and equilibrium composition of the reaction products obtained by transesterification of triglycerides with lower alcohols allowed choosing the optimal reaction conditions for practical application.

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