High pressure transesterification of microalgal oil over acid resin

Transesterification is the common method used to transform triglycerides into biodiesel. Conventionally, biodiesel is produced from vegetable oils, animal fats, and waste cooking oils. Biodiesel production from microalgae oil is more promising and sustainable alternative to previously mentioned feedstocks. Compared to plants, algae do not compete with food crops and have higher energy yields per area than terrestrial crops. In this study, continuous transesterification of algae oil using high pressure and solid acid resin was investigated. The variables studied were reaction temperature (180 – 220 ºC), pressure (200 – 350 bar), and residence time (2-15 min) with ethanol-to-oil molar ratio of 30. Experiments performed changing the reaction time indicated that most of the esters were formed during the first 5 minutes, the fatty ethyl ester yield becoming constant at reaction times higher than 9 minutes. This stationary value increased when higher values of the alcohol/oil molar ratio were adopted. When the pressure was increased at 250-350 bar, the performances of the process did not present significant modification.The results revealed that at the following optimum process conditions, reaction temperature of 190ºC, reaction time of 10 minute, pressure of 250 bar and ethanol-to-oil ratio of 30, a biodiesel yield of 90 wt% can be obtained.