Enzyamatic Synthesis Of Bio-based Fatty Acid Ester Plasticizers

Fatty Acid Methyl Ester (FAME) like methyl oleate, methyl palmitate, m ethyl stearate, and epoxy ester like epoxidized soybean oil are main componen ts of environmental plasticizer. Lipase, as a natural catalyst, has the ability of c atalyzing synthesis of fatty acid methyl ester(FAME) and Epoxy ester, and als o has the advantage of being gentle and environmentally friendly. Therefore, t his paper aimed at synthesis of FAME and Epoxy ester using Candida sp.99-1 25 lipase.Plasticizer, the most widely used in food package, children's toys, and medical products, should be strictly controlled its source and safety, and should not be prepared by waste oil like drainage oil. Therefore, this paper aimed at synthesis of FAME using fatty acid through esterification. Compared with the tranesterification used by the production of biodiesel, esterification catalyzed by Candida sp.99-125 lipase has faster reaction rate. In addition, during the reaction process, no glycerol is generated, thus reducing the difficulty of separating FAME and decreasing the viscosity of the system, which are beneficial to reusing lipase.There are two main problems in the enzymatic esterification:?In traditional process, organic solvent with high volatility is used, which leads to low substrate concentration and pure safety. ?In the late stage of the reaction, lipase will absorb water and aggregate because of the accumulation of water, thus its dispersibility and activity will be decreased. To resolve these two problems, this paper use the solubility of oleic acid to realize solvent-free production, and also modify lipase using hydrophobic carrier like diatomite to increase the dispersibility of lipase, preventing the aggregation of lipase. Furthermore, this paper decreased the loss of enzyme activity by feeding methanol and aerating to remove water between the gap of methanol addition, decreasing water content and preventing lipase from aggregating. When methanol flow velocity being 35.5mL·h-1, temperature being 35?, rotate speed being 250rpm, the conversion of oleic acid can reach 90%. The lipase can be used continuously in 5L reactor for 240h, lipase amount of each batch being 47U of each gram of substrate.During the research, it is also been found that Candida sp.99-125 lipase fermented broth has the ability of catalyzing esterification reaction. Besides, the hydrolysis rate of methyl oleate is slow when using lipase fermented broth as catalyst. Therefore, in this paper, first stage reaction catalyzed by lipase fermented broth and second stage reaction of esterification catalyzed by diatomite immobilized lipase are developed. Because the lipase in the fermented broth do not aggregate, it is not required to control the water generated in the primary reactor, eliminating the ventilation dehydration step. After dehydration of the reaction liquid in first stage reaction, the water content which immobilized lipase need to bear in second stage reaction is also reduced, which is more suitable for the production. When the mole ratio of oleic acid to methanol being 1:1.2, lipase fermented broth being 100U of each gram of substrate, the total fermented broth and water being 10% of substrate, 35?,250rpm, conversion of fatty acid can reach 75% in 7h in 30L reaction system. After the natural sedimentation of reaction liquid, the upper liquid is used in the second reaction, and the conversion of fatty acid can reach 97% in 4h.The feasibility of epoxidation reaction catalyzed by Candida sp.99-125 lipase is verified and solvent-free enzymatic epoxidation process is developed. The catalytic efficiency of lipase on epoxidation of soybean oil, oleic acid and methyl oleate are compared, and methyl oleate is choosen to be the substrate of mixed plasticizer eposy easter. When the diatomite immobilized lipase being 3500U of each gram of substrate, fungus powder being 3.5%(w/w), arboxyl donor oleic acid being 2.5%(w/w), mole ratio of methyl oleate and H2O2 being 1:1.2, addition rate of H2O2 being 5%·h-1, H2O2 is added for 20 times,35?,180rpm, the content of epoxy methyl oleate can reach 85% in 24h.