Continuous production of biodiesel from vegetable oil using supercritical ethanol/carbon dioxide mixtures

Biodiesel production is worthy of continued study and optimization of production procedures because of itsenvironmentally beneficial attributes and its renewable nature. Transesterification of triglycerides using supercritical ethanol on ion-exchange resin catalyst was investigated to study the ethyl ester conversion process. The reaction parameters investigated were the reaction time, pressure, temperature and molar ratio(alcohol to triglycerides), and their effect on the biodiesel formation. Addition of a co-solvent, supercriticalcarbon dioxide (critical point at 31 °C and 7.3 MPa), decreased the operating conditions maintaining a highreaction rate. The mixture ethanol/carbon dioxide used in this work was 1:3 molar ratio. The experimentswere conducted at temperatures of 150-200 °C, pressure from 150 to 250 bar and reaction times from 2 to10 min, and molar ratios of ethanol to vegetable oil from 20 to 45. The evolution of the process was followedby gas chromatography, determining the concentration of the ethyl esters at different reaction times. Resultsshowed that ethyl esters obtained in the continuous fixed bed reactor under supercritical conditions canachieve 80% yield of biodiesel at reaction time of 4 min