Removal of glycerol from palm oil-based biodiesel using new ionic liquids analogues

Upon the completion of the transesterification reaction, the produced biodiesel has to be purified from the by-product glycerol before being employed as a potential diesel substitute. The glycerol content must meet the limit set by the international biodiesel standards; namely EN 14214 and ASTM D6751. The conventional purification methods such as water washing, dry washing and membrane separation are prone to significant product loss, environmental pollution and increased production cost. In this work, seven new ternary deep eutectic solvents (DESs) were synthesised from choline chloride (ChCl) salt and two glycols-based hydrogen bond donors, namely glycerol and ethylene glycol. These DESs were employed as extraction solvents to remove total glycerol from palm oil-based biodiesel. The results revealed that the synthesised DESs have a higher total glycerol removal efficiency than that of free glycerol. Complete removal of free and total glycerol was attained by DES 3 at a molar ratio of 0.5:1 (DES 3: biodiesel).