Separation of Rapeseed Oil Transesterification Reaction Product Obtained Under Supercritical Fluid Conditions Using Heterogeneous Catalysts

Rapeseed oil transesterification reaction with ethanol under supercritical fluid conditions was performed either in the presence of catalysts or without them. The catalysts were Al2O3 and AlOOH, obtained after Al2O3 hydrothermal processing, and CaO/Al2O3 and CaO/AlOOH, obtained after permeation. The obtained product was measured for dynamic viscosity and density. Based on these data, kinematic viscosity was calculated. Biodiesel fuel was separated via centrifugation to extract more viscous ethyl esters of saturated fatty acids and unreacted triglycerides in order to comply with the standards for biodiesel fuel. Analyses have found that the maximum content of obtained ethyl esters of fatty acids in a reaction product before separation is reached, in the case of using the CaO/AlOOH catalyst, is in the amount of 93.34% by mass; and none of the samples’ kinematic viscosity values comply with the standards for biodiesel fuel. Performing centrifugation allowed us to reduce viscosity and increase biodiesel fuel concentration to reach the EN14214 standard requirements. Also, a significant deterioration of the initial catalysts’ strength after the singular experiment has been observed: Al2O3 by 22.4%, AlOOH by 13.89%, CaO/Al2O3 by 25.13%, and CaO/AlOOH by 17.27%.