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제108회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Porosity control and Comparative Study of Palladium-Nickel Phyllosilicate Nanocatalysts in Suzuki Coupling Reactions

2011년 8월 1일 15시 17분 30초
Ⅰ-INOR.P-167 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
목 <발표Ⅰ>
저자 및
김미종, 송현준
KAIST 화학과, Korea
The reactions on the surface of heterogeneous catalysts typically involve atom-molecule interactions and the active sites of catalyst particles are placed on or surrounded with highly porous supports where the access to the active sites are in the range of small dimension. In order to investigate such catalytic systems, we fabricated four palladium-based catalysts with branched Nickel Phyllosilicate shells (abbreviated as Niphy) which adopt the different degree of the porosity. We named each of the catalysts as Pd@SiO2, Pd@SiO2-Niphy 1, Pd@SiO2-Niphy 2 and Pd@Niphy, and applied to the Suzuki coupling reaction at room temperature to observe trends of the catalytic activities by screening each of the catalysts. We controlled the portion of nickel phyllosilicate branches stretched toward the Pd core as well as outside silica shell in the catalyst structures by the amount of nickel precursor (Ni(OAc)2?4H2O) added during the synthetic process, and especially Pd@Niphy was designed to have the hollow layer by etching the residual silica for larger porosity. We expected Pd@Niphy having hollow space and dense Niphy branches would show the best catalytic activity considering its short diffusion pathway only through the Niphy shell and the complete exposure of the active sites to the diffused reactants. As well, when Pd@SiO2 with no Niphy branches takes part in the catalytic reaction, the reactivity would be worse. Interestingly, the best catalytic activity was shown with Pd@Niphy followed by Pd@SiO2-Niphy 2, Pd@SiO2-Niphy 1 and Pd@SiO2, and the ranking trend was the same as expected. The results demonstrate that the large surface area and pore volume of heterogeneous catalysts fundamentally play a key role in the catalytic performance of materials, especially in the small systems such as hollow nanostructures.