Application Of Free Or Immobilized Penicillium Expansum Lipase In The Synthesis Of Carbonate And Its Derivative

Since the1st industrial revolution, different kind of catalyst systems were designed to make added value chemicals in order to meet the improving requirement in people's life, which, more or less, leads to some environmental problems, especially for metal component involvement for catalyst design. Nowadays, as the universal awareness of environmental protection, eliminating metal component involvement for catalyst design is more pressing and promising for our future. Hence, there is a need to identify "green" catalyst systems.One of the most promising strategies to achieve these goals is the utilization of enzymes which exhibit a number of features that make their use advantageous as compared to conventional chemical catalysts. Except for a high level of catalytic efficiency, lipases generally operate at mild conditions of temperature, pressure and pH with reaction rates of the order of those achieved by chemical catalysts at more extreme conditions. Lipase, as the potential candidates for "environmental-friendly" reactions, has been applied in various synthesis routes such as transesterification, hydrolysis, esterification, amidation, polyester synthesis, oxidation-reduction reaction, methyl like group transfer reaction. In this paper, we extended the application of lipase as catalyst to another two synthesis:the synthesis of dimethyl carbonate(DMC) from ethylene carbonate(EC) with methanol, the synthesis of1,3-dibutylurea from ethylene carbonate with butylamine.The use of a relatively expensive catalyst as an enzyme requires, in many instances, its recovery and reuse to make an economically feasible process. However, the idea of enzyme reuse implicitly means that the stability of the final enzyme preparation should be high enough to permit this reuse. Therefore, the enzyme needs to be very stable or to become highly stabilized during the immobilization process to be a suitable process. Thus, although there are hundreds of immobilization protocols, the design of new protocols that may permit to improve the enzyme properties during immobilization is still a exciting goal. Moreover, as industrial catalyst, the ideal immobilization processes should limit the use of toxic or highly unstable reagents, be very simple. What's more important is to improve the efficiency of separation, the magnetic property is a pinpoint protocol to solve this problem. Our research interests focus on the immobilization protocols and their application on the synthesis of dimethyl carbonate and1,3-dibutylurea, this thesis could be divided into six parts: Chapter one: the concept, origin, characters and development of lipase and immobilized lipase are reviewed. We systematically analyze the lipase immobilization protocols, especially for the magnetic supporting materials.Chapter two: the enzyme catalysts are firstly introduced into the synthesis of DMC with EC and methanol. The biocatalyst of Penicillium expansum lipase revealed high catalytic performance even under ambient pressure and low temperature. With the optimization of the reaction conditions(reaction temperature:60?, reaction time:96h, the addition of PEL:4.45%(based on EC weight ratio), the molar ratio of EC/methanol:1:16), the conversion rate of EC reached90%, while the yield of DMC can also reach87%.Chapter three:Penicillium expansum lipase was fixed on the natural polymeric materials by embedding method with selection of composite carrier of carboxymethyl cellulose and polyvinyl alcohol(CMC-PVA) as the supporting film. Compared with free lipase catalyzed transesterification from EC and methanol, immobilized enzyme exhibited higher catalytic efficiency and catalytic activity: the reaction time was shortened to48h; the conversion rate of EC increased to94%; the yield of DMC increased to93%; the selectivity of DMC improved to99%. Moreover, immobilized enzyme significantly increased the enzyme stability and reusability.Chapter four: the cellulose microspheres was successfully prepared by sol-gel phase transition at room temperature; magnetic cellulose microspheres was successfully prepared by situ synthesis method of Fe3O4nanoparticles; magnetic cellulose microspheres were functionalized successfully by using epoxy chloropropane; Penicillium expansum lipase was successfully loaded on the magnetic cellulose microspheres. porous structure in cellulose microspheres and multiple covalent bonding between the supporting and the enzyme molecular greatly improved the stability of the immobilized enzyme which exhibited good catalytic activity in the synthesis of DMC with EC and methanol. After the completion of the reaction, catalyst could be easily separated with the external magnetic field,Chapter five: amino epoxy matrix composite functional groups were novelty applied to the magnetic nanoparticles to load enzyme, which greatly improve the speed of enzyme adsorption; Meanwhile, supported hollow structure and abundant surface epoxy groups have greatly improved the stability of immobilized enzyme; The prepared immobilized enzyme exhibited higher catalytic efficiency and catalytic activity in the synthesis of1,3-dibutylurea from EC with butylamine, which was not commonly catalyzed by enzymes before. After the completion of the reaction, catalyst could be easily separated with by an external conventional magnet and recycled up to ten cycles without significant loss in the catalytic activity(94.8%).Chapter six:cellulose nanocrystals were prepared by sulfuric acid treatment; magnetic cellulose nanocrystals was successfully prepared by situ synthesis method of Fe304nanoparticles; magnetic cellulose nanocrystals were functionalized successfully by using epoxy chloropropane, which maked the surface of cellulose nanocrystals full of functional groups(epoxy group); and then some covalent linking could take place between activated groups of the enzyme (amino, thiol, and hydroxyl) and the epoxy groups on the support surface, which leaded to the immobilization of lipase.