by allowing it to separate out. Then, the methanol was removed by rotary
evaporation before the ChCl was added to make DESs. While this approach
was successful, it was time intensive. Consequently, the possibility
of adding the ChCl to the reaction mixture immediately after the
biodiesel formation reaction was complete was investigated. Not only
was it possible to form the DES without first separating the biodiesel
and glycerol phases, but the formation of the DES in situ also removed
methanol from the biodiesel layer and as before minimized the solubility
of the biodiesel in the DES layer. In a typical 1H NMR after a biodiesel
formation reaction, the molar ratio of biodiesel to methanol is approximately
1:1. After forming the DES with ChCl in situ, the ratio increases
dramatically to 150:1. In some cases, the methanol peak in biodiesel is
not detectable by 1H NMR analysis. Thus, the in situ method of forming
the DES saves time and labor with the added benefit of removing the
methanol impurity from biodiesel. The methanol can subsequently be
removed from the DES by rotary evaporation and re-used for another
biodiesel synthesis.