An Efficient Ionic Liquid Catalyst for the Synthesis of Biodiesel

Significance

A new acidic ionic liquid (IL) 1 was developed for the purpose of biodiesel synthesis. This new catalyst, based on hexamethylene­tetramine and 1,4-butane sulfonate bears up to four highly acidic SO₃H groups. With the catalyst in hand, rapeseed oils were methanolytically hydrolyzed into glycerol and the corresponding fatty acid methyl esters, the biodiesel equivalents. The workup proved to be easy, since excess methanol was removed under vacuum, the IL was centrifuged off and glycerol and biodiesel were simply phase-separated. The recovered catalyst could be reused ten times and still proved equally effective compared to previously known biodiesel synthesis catalysts (e.g., neat H₂SO₄ or [SO₃H-Bmim][HSO₄]).