Green And Efficient Procedures For The Synthesis Of Biodiesel

Biodiesel has received more and more attention for its great potential as the greenrenewable energy.The novel efficient and green procedures for the synthesis of biodieselhave been carried out.As we all know,the cost of the raw material was over 70% of thetotal cost during the biodeisel production.There were numerous raw materials for thesynthesis of biodiesel including vegetable oil,animal fat,waste oil etc.The acidity andwater content were quite different for different raw materials:some raw materials ownedlow acidity and water content while others high.The acidity of the raw materials wasvery important because different catalytic procedures should be chose for the synthesis ofbiodiesel based on the acidity of the raw materials.In order to develop green and efficientprocedure for the synthesis of biodiesel from different raw materials,both acid and basecatalytic processes have been carried out.The acid-catalyzed procedures should be taken for the raw materials with highacidity and water content.The ionic liquids were used as the green acid catalysts insteadof the traditional sulfonic acid to overcome the drawbacks such as high causticity andunreusability.The traditional Lewis acid ionic liquids were synthesized to catalyze thereaction first.After optimizing the reaction conditions and the ionic liquid composition,[Et₃NH]Cl-AlCl₃(x=0.7) was chose as the most efficient catalyst for the reaction withhigh activity and reusability.But the ionic liquid was very sensitive to water,which madethe water content of the raw materials be controlled strictly.Then,the SO3H functionedionic liquids were used for the reactions.The [SO₃H-Bmim][HSO₄] was selected for thereaction with the advantages of high activity,small usage,and insensitivity to water andacidity.But the catalyst was easily dissolved in the organic phase,which caused the greatloss of the catalyst.Moreover,the loss of the catalyst made the purification of the productmore difficult.The novel multi-SO₃H functioned ionic liquids have been synthesized forthe reactions.The novel ionic liquids owned much higher acidity and could catalyze thereaction more efficiently with smaller usage and shorter reaction time.Moreover thenovel ionic liquids were insoluble in the organic phase,and could be reused directlywithout loss of activity.The catalysts owned almost equal activity to the sulfonic acid,which made the catalysts one of the best choices for the synthesis of biodiesel using raw materials with high acidity.The base catalysts owned much higher activity compared to the acid catalysts.Thesupported solid base catalysts have been synthesized for the reactions instead of thehomogeneous base catalysts.KF supported on various carriers were applied to thereaction first.KF/Al₂O₃ was very efficient for the reaction,but the catalyst was instable tothe thermal treatment.The catalyst lost the activity when treated at the temperature above400℃.KF/CaO was also efficient for the reaction,but the high activity was obtainedthrough thermal treatment at relatively high temperature.Also the catalyst was easy toabsorb the water and carbon dioxide in the air and lose its activity.KF/MgO obtained thehigh activity after treated at 400℃and the activity decreased when higher temperaturewas introduced.Then,K₂CO₃ was used as the active compound to prepare solid basecatalysts.The active sites of the catalyst K₂CO₃/Al₂O₃ was originated from K₂CO₃.TheK₂CO₃/MgO showed very high activity for the reaction with the low temperature of 400℃needed to generate the efficient active sites.The high activity remained the same whenthe catalyst was treated at higher temperature.The KOAc supported on different carrierswere also prepared for the reactions.Here the active sites were produced through thedecomposition of KOAc at high temperature.The carriers such as MgO could alsoprovide the active sites during the thermal treatment.To sum up,K₂CO₃/MgO was themost efficient catalyst for the synthesis of biodiesel using the raw materials with lowacidity.Here the catalysts with waterproof and acid proof ability were synthesized for theraw materials with low acidity and water content.The catalysts were synthesized throughthe solid-state reactions and thermal treatment.The results showed that the novel catalystowned high waterproof ability compared to the traditional catalysts,and the catalyticactivity was still very high for the raw materials with the water content of 1%.The highwaterproof ability is the basis of the acid proof ability.For the strong base sites reactedwith the free acids in the raw materials and produce the corresponding water.The catalystalso could be reused after the reactions with high acidity and water content.