Synthesis of biodiesel from soybean oil catalyzed by ionic liquids

An ionic liquid stable in water,1-(3-sulfonic acid) propyl-imidazole hydrosulfate with an alkane sulfonic acid group, was prepared.Synthesis of biodiesel from soybean oil catalyzed by the ionic liquid was studied.Effects of ionic liquid dosage,molar ratio between methanol and soybean oil,reaction temperature and reaction time on the transesterification reaction and stability of the ionic liquid were investigated.Optimal transesterification condition was obtained as follows: n(methanol) ∶n(soybean oil) =12 ∶1,reaction temperature 120 ℃,reaction time 8 h,dosage of ionic liquid=4.0% of the oil weight.Mass fraction of fatty acid methyl ester of 96.5% was obtained in the product under the optimal condition.The ionic liquid was stable and could be repeatedly used.