Fabrication Of Complex Microcapsules Through A Pickering Emulsion Strategy And Their Catalytic Reactions

Microcapsules,developed for the entrapment and transport of active ingredients,have attracted widespread attention in applications such as agriculture,food industry,microreactors,drug delivery and catalysis.However,the internal structure of traditional microcapsules lacks effective control method,which hinders the application of microcapsules in industrial catalysis.Therefore,developing effective methods to prepare microcapsules with complex structures is a key scientific issue in this field.Pickering emulsion provide a direction for solving the above problems.when using Pickering emulsion as a template to prepare microcapsules,the permeability and mechanical strength of microcapsules can be easily controlled by changing parameters such as emulsifiers,crosslinkers,p H,etc.In this work,silica-based microcapsules are constructed by using Pickering emulsion as a template,and their characterization and catalytic applications are also studied.The major work of this thesis is showed below:Based on reports in the literature,the solid emulsifier and molecular surfactant were assembled together,and different mesoporous silica microcapsules were prepared by changing the concentration of hydrochloric acid.The morphology and structure of the microcapsules were characterized by scanning electron microscope and other characterization methods,and mechanical strength tests were performed on the microcapsules thought a stirring test.when fixed the amount of TEOS and increased the concentration of hydrochloric acid,the hydrolysis rate of the cross-linking agent accelerated,and the pore channels and specific surface area of the prepared solid mesoporous microcapsules also increased.In-situ encapsulating enzyme catalyst technique can reduce the operation process and the loss of the enzyme catalyst.Although microcapsules prepared by the above method can immobilize enzyme through physical adsorption,it is not suitable for encapsulating enzyme catalysts in situ.A gradual loss of enzyme activity was unavoidable since hydrochloric acid will affect the activity.Therefore,in order to prepare a multi-compartmentalized microcapsule in situ encapsulation of CALB enzyme,two kinds of silica particles with different surface wettability are used as emulsifiers to confine the enzyme in Pickering droplets by one?step emulsification,and a water-in-oil-in-water(W/O/W)Pickering double emulsion was prepared by double emulsification.Afterwards,the multicompartmentalized microcapsule with enzyme catalyst prepared via onestep cross-linking,the double emulsion as a template and hyperbranched polyethoxysilane(PEOS)as a cross-linking agent.The continuous-flow method was used to evaluate the catalytic performance of the microcapsules in a fixed-bed.As an example of transesterification reaction,the results showed that the reaction system has high conversion rate and robust stability,which proves that the multi-chamber microcapsules are suitable for practical industrial production.