Study On Preparation Of Biodiesel With Deep Eutectic Solvent

As one of the alternatives for renewable energy source, biodiesel has gainedsignificant attention in recent years. Biodiesel is commonly produced withhomogeneous base catalysts and solid base catalysts. However, homogeneous basecatalysts can induce equipment corrosion, environment pollution and side reaction,and there are still some challenges ahead before the industrialization with solid basecatalysts such as low activity, stability and so on.Aiming to these above problems during the industrialization of biodiesel production,we try to introduce a novel nontoxic, biodegradable and low-cost deep eutecticsolvent (DES) into the reaction solvent system in order to develop a new reactionsolvent system and improve the reaction and simplify the products separation. In thisstudy, a deep eutectic solvent (DES) consisting of choline chloride and glycerol (1:2molar ratio) was prepared for the transesterification of rapeseed oil to producebiodiesel catalyzed by NaOH and CaO respectively.Firstly, GC analysis of the products was established. Then Response SurfaceMethodology (RSM) and Box-Behnken Design (BBD) were employed to optimize thereaction conditions. Our results suggest that up to98.05%FAME yields could beobtained at optimum conditions of6.95methanol/oil molar ratio,1.34wt%NaOHconcentration and9.27wt%DES concentration, which is higher than that of thereaction without DES (81.48%); up to94.85%at the optimum conditions of14.46methanol/oil molar ratio,8.08wt%CaO concentration and10.41wt%DESconcentration, which is higher than that of the reaction without DES (87.33%). Dataanalysis and verification results confirmed the suitability of BBD and RSM methodsfor optimizing the biodiesel synthesis. The addition of DES can change the phasedistribution of the reactants, inhibit side reaction, and thus improve FAME yield andsimplify products separation.Furthermore, commercial CaO was directly used to catalyze the transesterificationfor biodiesel preparaction by the aid of DES. The result shows that DES can makecommercial CaO activated directly, which is more simple, more efficient and energyconserving compared with other activation methods such as calcination. XRD andFTIR determination indicate the apprearance of calcium diglyceroxide. SEM and EDSanalysis results indicate that the morphologies and the surface chemical elementsamounts of CaO have changed, which is in accord with the appearing of calcium diglyceroxide. This study will provide a novel idea and essential fundmental data forthe industrialization of biodiesel production and DES application.