형태가 조절된 고분자 마이크로 입자의 합성과 마이크로 리액터로의 응용 연구

Abstract

Noble metal nanoparticles (Au, Ag, Pt, Pd, etc.) are of great significance for their potential application as catalysts based on various properties, such as chemical, optical, electrical characteristics. Especially, because they have high surface energy, resulting from their small size, numerous noble metal nanoparticles can serve as an effective surface on which the actual reaction occurs. However, these nanocatalysts tend to aggregate easily to minimize their surface areas, as a consequence of their small size, therefore, easy to lose catalytic activity. Furthermore, the small size makes them difficult to separate from the reaction system. To solve these problems, metal nanocatalysts synthesized in solution have been suitably deposited onto the surface of support material to obtain heterogeneous catalysts. The supported nanocatalysts are able to retain high stability and catalytic activity. Moreover, these have the advantages of easy and complete separation from the reaction system and excellent recyclability. In the supported nanocatalysts, structures of support and nanocrystal play a key role in achieving high catalytic performance. The open pore on the surface and porous structure can serve as more reaction sites and make reactants faster diffuse from the bulk to their surface. In this study, we investigated the effect of this structure of supports and nanocatalyst on the catalytic performance. we synthesized the catalytic supports, such as hollow polystyrene (PS) microparticles with a single hole on their surface and highly porous PS microparticles with interconnected open pores, through swelling and evaporation process in the emulsion system. In addition to catalytic support with unique shapes, we transformed solid monometallic nanocatalysts on the surface of heterogeneous catalyst into hollow and porous bimetallic nanocatalysts. To evaluate catalytic performance, when the synthesized heterogeneous catalysts were used as a microreactor for the 4-nitrophenol (4-NP) reduction reaction by sodium borohydride (NaBH4), they exhibited extremely high catalytic activity and excellent recyclability. These results demonstrated that the structures of the support and nanocatalyst were an important factor to improve catalytic performance.