The Study Of Pva Composite Enzymatic Membrane Reactor On Synthesis Of Dodecyl Stearic Acid Ester

PVA enzymatic membrane is a kind of composite membrane with bothcatalytic and separation functions. Enzyme and membrane become joined（immobilized enzyme） together in preparation process，without changingany natural characteristics. With the assistance of the pervaporationmembrane reactor （EMR）, the enzymatic reaction and membraneseparation process has been achieved in a single membrane. By removingby-products or inhibited product online, the occurrence of side effectswas reduced and the reaction conversion rate and yield was improved. Onthe basis of preliminary exploration of our lab, the preparation of PVAenzyme membrane was carried out and used them for the synthesis oflauryl stearate coupled with EMR in this study. The major achievementsare as follows:The best conditions of PVA composite enzymatic membrane weredefinited. The best conditions of separated layer （PVA/PES membrane）was that using the PES membrane as a support, the molar ratio ofcrosslinking agent maleic acid and PVA was1:10,2wt%PVA of castingsolution dip-coat three times, then heated at100℃for1h. The catalytic layer of PVA composite enzymatic membrane was prepared byimmersion precipitation phase inversion method on the basis of PVA/PESmembrane. When PVA concentration of casting solution was5wt.%,candida lipase concentration was2wt.%, glutaraldehyde concentrationwas0.1wt%, saturated ammonium sulfate as a coagulant, dextran foradditives, the enzymatic membrane performs best.The properties results of enzymatic membrane show that the afterenzyme molecules immobilized by membrane, its thermal stability, pHstability, operational stability and storage stability has been improvedcompared to the free lipase. The relative activity of free lipase was only8%when heated60min at50℃, while enzymatic membrane remained ashigh as90%; the activity of the enzyme membrane increased nearly20%more than the free enzyme at the same pH conditions; In addition, aftereight batches hydrolysis of olive oil by enzymatic membrane, the relativeactivity remained at about88%; the relative activity is still maintained at80%after stored14days, storage time was improved obviously. Theresults of separation performance of PVA enzymatic membrane testshowed that the flux and separation factor decreased to some extent afterenzymatic layer loading, but still possess good separative performance.The synthsis of lauryl stearate was studied by EMR. First of all, Thebest synthesis conditions by batch reactor was that n-hexane as a reactionmedium, the lipase dosage45U, the molar ratio of alcohol to acid1:1, the substrate concentration0.1mol L^-1, the reaction temperature at35-50℃,the conversion was61%. The results of synthesis of lauryl stearatestudied by EMR show that the conversion rate of tearic acid was83%at12h at the same condition, increasing by22%compared with theequilibrium conversion. The results showed that the online removal ofbyproduct water through by PV process, broke the original limit ofreaction equilibrium and significantly improved the conversion rate oftarget product.