Catalytic transesterification of rapeseed oil under supercritical fluid conditions and physical properties of the reaction product

This research examines the transesterification reaction of rapeseed oil with ethanol in the presence of heterogeneous catalysts - Al2O3 and CaO/Al2O3 with 2% mass impregnation of CaO. The experiments were carried out at a molar ratio of ethanol: rapeseed oil of 18:1 (volume ratio ≈ 1:1) at temperatures of 608, 623 K, and a pressure of 20 MPa for up to 30 minutes in a flow-type unit. The state’s selected pressure and temperature parameters correspond to the supercritical fluid conditions. The results are presented for kinematic viscosity (T=313 K, P=0.1 MPa), density (T=288÷323 K, P=0.1 MPa), refractive index (T=298 K, P=0.1 MPa) of the transesterification reaction product. A quantitative assessment of the target product was carried out using chromatographic analysis. We have established the influence of temperature and duration of the reaction process on its efficiency. We present the strength characteristics of the catalysts used before and after the experiments. During attrition, the initial Al2O3 catalyst lost weight by 0.4 ± 0.1%. The mechanical crushing strength along the generatrix was 7.1 ± 0.3 N/mm. The strength of catalysts after carrying out the transesterification reaction under supercritical fluid conditions decreases, on average, by 24-28%. The use of heterogeneous catalysts Al2O3 and CaO/Al2O3 with 2%wt. impregnation of CaO showed an increase in the fatty acid ethyl esters concentration in the transesterification reaction product compared to the reaction carried out without the use of catalysts.