Study On Preparation Of Biodiesel Using Ionic Liquid/Base As Catalyst System By Transesterification From Soybean Oil

This paper focused on the synthesis process of biodiesel, which was catalyzed by alkali immobilized in ionic liquids. Soybean oil and methanol were catalyzed by sodium methoxide(NaOMe) in phosphonium based and imidazolium based ionic liquids to prepare biodiesel. The influence factors such as the types of ionic liquids on the yields of fatty acid methyl esters and the reusability of the catalyst system were discussed.[thtd-Ph][N(CN)2]/NaOMe was chose as the reaction catalyst system to investigate the reaction condition by the orthogonal design of experiment. The optimum reaction condition was determined as followed: at room temperature, the MeOH: SBO ratio was 30:1; the load of NaOMe was 20mol%; reaction time was 45min. With this reaction condition, the fatty acid methyl esters yield of more than 97.8% was gained. Most importantly, the catalyst system can be recycled and reused for six runs without any significant loss of catalytic activity.Under this optimum reaction condition, [thtd-Ph]Cl/NaOMe, [thtd-Ph][N(Tf)2]/ NaOMe, [Bmim]BF4/NaOMe, [Bmim]PF6/NaOMe, [Bmim]OH/ NaOMe were also applied as the reaction catalyst systems. And then from the point of efficiency and reusability, these catalytic systems were contrasted.From the results, it was noted that in these three phosphonium based ionic liquids, the yield of fatty acid methyl esters was highest (97.8%) with [thtd-Ph][N(CN)2]/ Na -OMe as the catalyst system. And this catalyst system can be reused for six runs. It was also noted that in these three imidazolium based ionic liquids, the yield of fatty acid methyl esters was highest (97.2%) with [Bmim]OH/NaOMe as the catalyst system. However, the reusability of this catalyst system can not be achieved. As a whole, from the point of the yield of fatty acid methyl esters and the reusability of the catalyst system, the phosphonium based ionic liquids are better than imidazolium based ionic liquids as reaction solvent.Finally, the novel basic ionic liquid [Bmim]OH was used as catalyst in synthesis of biodiesel for facilitation. However, the results illustrated that this basic ionic liquid has no catalytic activity in this reaction.