Supercritical ethanol technology for the production of biodiesel: Process optimization studies

Biodiesel is currently produced from transesterification reaction of various types of edible oil with methanol. However, the requirement of methanol makes the current biodiesel produce not totally 100% renewable as methanol is derived from fossil based products. Ethanol, on the other hand, can be produced from agricultural biomass via fermentation technology and is already easily available in the market at a high purity. Thus, in this work, possible 100% renewable biodiesel fuel was prepared from refined palm oil by using non-catalytic transesterification reaction in supercritical ethanol. The effect of various process parameters on the yield of biodiesel was studied using design of experiments (DOE). The process parameters studied are: reaction temperature (300–400 °C), reaction period (2–30 min) and ethanol-to-oil ratio (5–50). The optimum process conditions were then obtained using response surface methodology (RSM) coupled with center composite design (CCD). The results revealed that at the following optimum process conditions; reaction temperature of 349 °C, reaction period of 30 min and ethanol-to-oil ratio of 33, a biodiesel yield of 79.2 wt.% can be obtained.

This study has successfully optimized the conversion of ethanol and palm oil into biodiesel via non-catalytic supercritical ethanol technology using design of experiment (DOE) approach. Using DOE approach over conventional strategy, the significant interaction between process parameters such as in the graph shown below was successfully identified. It was then used to obtain the optimum process parameters that can give the maximum yield of FAEE. At the following conditions; reaction temperature of 349 °C, molar ratio of ethanol-to-oil of 33.2 and reaction time of 29 min, an optimum yield of 79.2 wt.% was obtained indicating the feasibility of using supercritical technology to produce biodiesel without the usage of catalyst.Figure optionsDownload as PowerPoint slide