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A quantum-chemical study of the mechanism of transesterification reaction carried out in the traditional and supercritical fluid (SCF) conditions has been performed. Samples of biodiesel fuel have been derived from rapeseed oil in the environment of supercritical ethanol using a flow type unit, both in the absence and in the presence of heterogeneous catalysts-metal oxides. Experimental studies of kinematic viscosity of a large array of samples of derived biodiesel have been performed. The viscous correlation allowing determining the content of the desired product-fatty acid ethyl esters (FAEE)-in biodiesel samples, has been made based on the obtained experimental data on the kinematic viscosity of biodiesel samples. The influence of change of the dielectric permittivity of working environments on the rate of reaction of transesterification in the supercritical fluid conditions has been revealed.

In Europe, rapeseed is a renewable raw material which has been widely used for the production of biodiesel by various processes. The transesterification reaction of rapeseed oil with ethanol to biodiesel in supercritical fluid conditions was investigated using several heterogeneous catalysts and preliminary ultrasonic emulsification of the reaction mixture, to run the reaction at mild conditions. Phase equilibrium of fatty acids in supercritical ethanol was study to determine the operating condition in supercritical states. Transesterification experiments were carried out under a pressure of 30 MPa, with ethanol to oil molar ratio (in the range of 12:1⿿20:1), temperature (623 K to 653 K), and the catalyst loading level and type were the main parameters. The most important characteristics of Al 2 O 3 support catalyst and the impregnation method with aqueous solution of metal nitrates are also described. Yields of Fatty Acids Ethyl Ester (FAEE) are reported for different ZnO/Al 2 O 3 , MgO/Al 2 O 3 , SrO/Al 2 O 3 catalysts in different experimental conditions. The higher yield of 97.46% was obtained under the optimal conditions 623 K, 30 MPa, 12:1 ethanol/FAEE molar ratio, with SrO/Al 2 O 3 (2 wt.% SrO) impregnated catalyst.

Several biodiesel fuel samples produced from rapeseed oil by the noncatalyzed transesterification reaction with supercritical ethanol at various temperatures from (593 to 653) K and molar ethanol to rapeseed oil ratios from (6:1 to 20:1) were used to measure kinematic viscosity. Measurements were made using the capillary viscometer (VPZ-2, Labtex Com., Moscow). The combined expanded uncertainty of the kinematic viscosity measurements at the 95 % confidence level with a coverage factor of k = 2 is estimated to be 0.35 %. All measurements were made at temperature of 313.5 K (ASTM D445) and at atmospheric pressure. The effect of fatty acid ethyl esters (FAEEs) content on the kinematic viscosity of biodiesel fuel samples at 313.15 K was studied. The correlation between the FAEEs concentration in biodiesel fuel samples and their measured kinematic viscosity at 313.15 K was found. The derived correlation between the kinematic viscosity and the FAEEs contents allows controlling the progress of the rapeseed oil t...