Study On Preparation Of Biodiesel Catalyzed By L-aspartic Acid Ionic Liquid Combined With Lipase

Biodiesel is a long-chain fatty acid monoester prepared from animal and vegetable oils.Its excellent properties make it a green substitute for petrochemical diesel.The acid-base catalysts for biodiesel production in industry are insufficient,and the main disadvantage is that they will pollute the environment.Although the reaction conditions are mild,there are also some disadvantages,such as shortened enzyme life,slow reaction speed and so on.In addition,organic solvents are commonly used as the medium in the preparation of biodiesel by enzymatic method,which are flammable and explosive and will pollute the environment.At present,ionic liquids have been widely concerned as a new type of catalyst.Ionic liquids can not only play the role of organic solvents,but also have catalytic properties,which provides a new possibility for the use of ionic liquids and lipase in the production of biodiesel.In view of the defects and shortcomings of enzyme catalyzed biodiesel production,amino acid ionic liquid combined with porcine pancreatic lipase(free/immobilized)was selected as the catalyst with low price and in line with the concept of"green chemistry"in the preparation process.The single factor of biodiesel production from oleic acid,lauric acid,Jatropha curcas seed oil and soybean oil was studied The main contents and conclusions are as follows.(1)Using[Asp]HSO₄ and free lipase to catalyze oleic acid and lauric acid,the optimal conditions were obtained as follows:reaction time 21 h,alcohol oil ratio 4.5:1,dosage of[Asp]HSO₄ was 4 wt%,dosage of free lipase was 3 wt%,temperature was45?.Under these conditions,the maximum conversion of oleic acid was 89.96%,and the average conversion was 87.93%;The optimum conditions of lauric acid catalysis were as follows:the dosage of[Asp]HSO₄ was 6 wt%,the molar ratio of alcohol to oil was 7.5:1,the dosage of free enzyme was 3 wt%and the reaction time was 6 h.The average conversion rate was 97.30%after repeated validation test.(2)Using[Asp]HSO₄ and different treatment of porcine pancreatic lipase to catalyze the esterification of oleic acid,the optimal conditions for the esterification of oleic acid were obtained as follows:the reaction time was 9 h,the ratio of alcohol to oil was 5.5:1,the dosage of[Asp]HSO₄ was 10 wt%,the dosage of immobilized lipase was2 wt%,and the temperature was 45?,Under these conditions,the highest conversion can reach 84.85%.The average conversion was 83.31%.(3)Compared with free lipase,although the ratio of alcohol to oil and the amount of ionic liquid increased after immobilization,the conversion rate of fatty acid methyl ester was still low in the case of short reaction time.Although immobilized lipase can improve the stability of the enzyme,and can tolerate more[Asp]HSO₄ and methanol than free lipase,it also has some problems,such as incomplete fixation and poor catalytic effect.Therefore,free lipase can still be used in actual industrial production,although experiments show that the optimal time of using free porcine pancreatic lipase is longer,But it can lead to better conversion.(4)The orthogonal experiment was used to optimize the synthesis of methyl oleate catalyzed by[Asp]HSO₄ and free porcine pancreatic lipase.The optimal reaction conditions were as follows:the amount of[Asp]HSO₄ was 6 wt%,the ratio of alcohol to oil was 5.5:1,the amount of free enzyme was 4 wt%,the reaction time was 21 h,and the reaction temperature was 45?.Under these conditions,the highest conversion could reach 92.14%,The average conversion was 91.91%.Response surface methodology was used to verify that the optimal reaction conditions were obtained when[Asp]HSO₄ and immobilized enzyme were used as catalysts for oleic acid esterification reaction.Under these conditions,the amount of[Asp]HSO₄ was 13.15wt%,the ratio of alcohol to oil was 6.73:1,the amount of immobilized enzyme was2.05 wt%,and the reaction time was 9.43 h.under these conditions,the predicted conversion of the model was 88.13%.The average conversion rate was 87.97%after repeated validation test,which further showed that the regression model analyzed by the software was reasonable and could be used to predict Biodiesel Catalyzed by[Asp]HSO₄ ionic liquid combined with immobilized lipase.(5)The optimal conditions for biodiesel production from Jatropha curcas oil catalyzed by[Asp]HSO₄ and free porcine pancreatic lipase were as follows:the amount of[Asp]HSO₄ was 6 wt%,the ratio of alcohol to oil was 15:1,the amount of free enzyme was 3 wt%,the reaction time was 10 h and the reaction temperature was 45?.Under these conditions,the highest conversion was 43.61,and the average conversion was 43.05%.The optimum conditions for the transesterification of Jatropha curcas oil catalyzed by[Asp]HSO₄ combined with immobilized enzyme were as follows:the dosage of[Asp]HSO₄ was 6 wt%,the ratio of alcohol to oil was 9:1,the dosage of immobilized enzyme was 4 wt%,the reaction time was 8 h and the reaction temperature was 45?.Under these conditions,the highest conversion was 47.07%,and the average conversion was 45.84%.The transesterification of soybean oil was catalyzed by[Asp]HSO₄ and free porcine pancreatic lipase.Under the optimum conditions of[Asp]HSO₄ dosage of 10 wt%,alcohol oil ratio of 5:1,free enzyme dosage of 4 wt%,reaction time of 6 h and reaction temperature of 45?,the highest conversion rate was47.30%,and the average conversion rate was 45.70%.From the three single factor transesterification experiments,it can be concluded that the conversion rates of the optimal reaction conditions of[Asp]HSO₄ combined with porcine pancreatic lipase in different treatment groups are less than 50%,which indicates that the catalytic effect of[Asp]HSO₄ combined with porcine pancreatic lipase on transesterification is not ideal,and it is not suitable for transesterification.