Deep eutectic solvents for purification of waste cooking oil and crude biodiesel

The goal of this work was to explore the applicability of deep eutectic solvents in biodiesel production process. Biodiesel was produced from waste cooking oil via base-catalysed transesterification. The efficacy of two base catalysts KOH and NaOH on the conversion of triglycerides into biodiesel was tested. Eutectic mixtures DES 1 (K₂CO₃  : C₂H₆O₂  = 1 : 10) and DES 2 (C₅H₁₄ClNO  : C₂H₆O₂ = 1 : 2) were prepared. DES 1 was used for feedstock deacidification and DES 2 for biodiesel purification via extraction. Effects of DES 2 to biodiesel ratio and the extraction duration on free glycerol removal were tested. Samples were analysed using FTIR and ¹H NMR spectroscopy. Synthesis of biodiesel was carried out for 3 h at 60 ° C with mass ratio KOH : methanol : oil = 1 : 40 : 100. DES 2 was effective for purification of biodiesel. Mass ratios 0.5:1 and 1:1 proved best and 45 minutes of extraction was enough to reduce free glycerol and increase the content of fatty acid methyl esters.