Study On Chemo-Enzymatic Epoxidation Process Of Fatty Methyl Esters And Reaction Kinetic Mathematical Model

For its high activity,specificity,mild reaction conditions,lipases are widely used in food,chemical and many other areas.With aqueous hydrogen peroxide solution(30%H2O2)as oxidant,immobilized lipase Novozym 435 as catalyst,epoxidation reaction conditions of fatty acid methyl esters were optimized using single factor method and response surface method.Experimental results on the activity of the lipase in different organic solvents indicate that toluene exhibited better one than carbon tetrachloride and n-hexane.Effect of H2O2 dosage and addition modes,different oxygen carriers on the epoxidation was investigated.Experimental results indicate that different oxygen carriers did not exhibit remarkably different functions.Even in the absence of oxygen carrier,Novozym 435 can catalyze the epoxidation of fatty acid methyl esters.Oxygen carrier,fatty acids,required for the reaction system may result from the hydrolysis of fatty acid methyl esters.This is verified by GC-MS data.Optimal reaction conditions were achieved by response surface method.Under the conditions of fatty acid methyl esters 20 g,enzyme 3%(based on fatty acid methyl esters),toluene 30 mL,molar ratio of hydrogen peroxide to substrate bond 1.7:1,reaction temperature 40 ? and reaction time 5 h,product epoxy value is 4.82 g/100g,.FAMEs conversion is up to 93.18%,and epoxidation selectivity is 84.12%.In all the existing methods,formic acid self-catalytic epoxidation is considered suitable reaction system for the production of epoxided fatty acid esters.Orthogonal experiments were used to determine optimal reaction conditions.Under the conditions of fatty acid methyl esters 10 g,formic acid 1 g,molar ratio of H2O2 to substrate bond 1,4:1,reaction temperature 60 ?,stirring speed 360 rpm,and reaction time 7.0 h,the epoxy value is 4.58 g/100g.GC-MS data suggested that there is the hydrolysis of a small amount of epoxy bond in an acidic solution to form a dihydroxy compound.A biphasic reaction kinetics is studied.Distribution coefficient of H2O2,formic acid,performic acid in organic phase and aqueous phase are determined experimentally and contrasted with calculated one using ASPEN PLUS software.Using epoxy value,iodine value,utilization of H2O2,content of performic acid data,a biphasic kinetic model of the epoxidation process has been set up,and the prediction value is good consistent with experimental one.Investigation of enzymatic and chemical method indicates that enzymatic epoxidation of FAMEs is characteristic of mild reaction temperature,high epoxy value,light product color and high epoxidation selectivity.