Synthesis of Brønsted dicationic basic ionic liquid and its catalytic activity for biodiesel production

A new Brønsted basic dicationic morpholine ionic liquid (IL) was synthesized with N-methyl morpholine and 1,4-dibromobutane via a two-step procedure. The structure of new dicationic IL was characterized by FT-IR, ¹H NMR spectra and elemental analysis and the thermal stability was analyzed by TGA. Meanwhile, the alkalinity and solubility of the dicationic IL were measured and its catalytic activity in the transesterification of soybean with methanol to produce biodiesel was investigated. The results show that under the optimized conditions of n(methanol)/n(soybean oil) = 14, catalyst amount of 5% based on soybean oil, 60 ℃ and 5 h, the yield of biodiesel reaches 95.6%. After recycled by drying under vacuum, the dicationic IL can be reused for more than 6 times without significant decrease in the catalytic activity.