Thermodynamics of Phase and Chemical Equilibrium in the Processes of Biodiesel Fuel Synthesis in Subcritical and Supercritical Methanol

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.