Elimination of All Free Glycerol and Reduction of Total Glycerol from Palm Oil-Based Biodiesel Using Non-Glycerol Based Deep Eutectic Solvents

Purification of biodiesel prior to utilizing it as an alternative fuel is an essential industrial practice. Low glycerol content is one of the important pointers needed for passing the EN 14214 and ASTM D6751 international biodiesel standards. In this study, choline chloride (ChCl) as salt and ethylene glycol and 2,2,2-Trifluoroacetamide as hydrogen bond donors (HBDs) were employed to synthesize two ammonium salt-non glycerol based Deep Eutectic Solvents (DES). The physical properties of the synthesized DESs were measured and analyzed. These DESs were utilized to remove all the free glycerol from the palm oil-based biodiesel. The results indicated that all the tested DESs were able to remove all free glycerol successfully. The Central Composite Design (CCD) of the Response Surface Methodology (RSM) was used to to experiment design and optimization of total glycerol removal using ethylene glycol-based DESs and 2,2,2-Trifluoroacetamide-based DESs. The maximum total glycerol removal by ethylene glycol-based DESs was obtained at 0.66 ethylene glycol mole fraction and at DES/biodiesel molar ratio of 3 with removal efficiency of 23.85% as well as by 2,2,2-Trifluoroacetamide-based DESs at 0.60 2,2,2-Trifluoroacetamide mole fraction and at DES/biodiesel molar ratio of 2.93 with removal efficiency of 29.29%. The reusability of these DESs for removing free glycerol and total glycerol content from palm oil-based biodiesel was also investigated. This study proves that both ammonium salt-non glycerol based DESs can be successfully employed to remove the glycerol from palm oil-based biodiesel.