Preparation And Kinetics Of Polydopamine Modified Xerogels Immobilized Enzyme

Since the beginning of the 21st century,with the increasing awareness of the green development of chemical industry,the coupling technology of biocatalysis and chemical unit operation has been widely studied.Reactive distillation,as an important technology for chemical strengthening,integrates reaction and separation in one unit operation,which can reduce equipment and operation costs,and remove the product to break the balance limit to improve product yield.Enzymatic reactive distillation integrates biocatalysis and reactive distillation,highlighting their advantages,which is a major innovation in chemical process intensification.Among them,efficient,long-term,stable immobilized enzyme catalyst plays a central role.In the above context,considering the continuous and large-scale production of butyl acetate by enzymatic catalytic reactive distillation,this research focused on silica xerogel carrier and synthesized the enzyme-carrying xerogel monolithic columns similar to fillers,and systematically studied its design,optimization and modification,and the construction of kinetic model for the synthesis of butyl acetate by catalytic transesterification.Firstly,based on the immobilization of lipase by sol–gel method,a controlled solvent evaporation assisted batch drying method was developed to prepare enzyme-carrying silica xerogels（Si O₂-CH₃-CALB）with different co-procursors contents.The pore structure,mechanical strength,hydrophobicity and enzyme stability were adjusted.The experimental results show that the appearance of Si O₂-CH₃-CALB with different precursor contents prepared by the new method shows excellent integrity.The optimal co-precursor content was obtained by performance comparison.Secondly,the mechanical properties of silica xerogel are brittle materials,and the interaction between the carrier and the enzyme is weak when used to immobilize the enzyme.In order to improve the interaction between the enzyme and the carrier and balance the mechanical properties of the carrier,polydopamine was used to modify the surface of silica xerogel,and the polydopamine modified silica xerogel immobilized enzyme（Si O₂-CH₃-CALB@PDA）was prepared,which enriched the modification method of silica xerogel.Compared with Si O₂-CH₃-CALB,the immobilized enzyme ability(45.6 mg/g_support)and the ultimate compressive strength（12.55 MPa）of Si O₂-CH₃-CALB@PDA were higher than those of Si O₂-CH₃-CALB(28.5 mg/g_support;9.00 MPa).In addition,Si O₂-CH₃-CALB@PDA showed excellent operational stability.Finally,based on the good immobilization ability and stability of Si O₂-CH₃-CALB@PDA,the kinetics of synthesis of butyl acetate by catalytic transesterification was studied.The reaction conditions such as ester-alcohol ratio,catalyst dosage and temperature were optimized,and the pseudo-homogeneous second-order kinetic model was established,which laid a theoretical foundation for the design of reaction distillation column and the amplification production of butyl acetate in the later stage.