| Summary: | 碩士 === 中原大學 === 化學研究所 === 98 === Developing recyclable and efficient metal catalysts, particularly nanoparticle catalysts, for chemical reactions is an active research area then and now. The goal of this research is to investigate preparation of palladium and platinum metals deposited in the pores of mesoporous materials such as Santa Barbara 15 (SBA-15) by an incipient wetness impregnation (IWI) method and to study catalytic properties of this Pd+Pt/SBA-15 template by investigating the recyclability of the template and the hydrodechlorination efficiency of some polychlorinated biphenyl (PCB) congeners and mixtures in the presence of hydrogen gas.
Hydrodechlorination of a PCB congener, BZ#3 (4-monochlorobiphenyl), on a 4% Pt-1% Pd/SBA15 template was performed at 30℃、50 ℃ and 100 ℃. The results showed that even at 30 ℃, BZ#3 can be completely reduced to bicyclohexyl, suggesting that this mixed metal catalyst very effectively lowers the activation energy of the reduction reaction, a phenomenon which has yet been reported so far. Hydrodechlorination of other homologs in the PCB family showed similar results, all reaching 100% with reduction efficiency with mass balance equal or better than 90%.
The catalytic reaction pathway of this mixed metal catalyst was studied by performing experiments for various durations using BZ#3. After shorter reaction times (30 to 90 minutes), biphenyl, cyclohexylbenzene, and bicyclohexyl were all present as the products, whereas after 120 minutes of reduction, only bicyclohexyl is present. This observation suggests that the hydrogenation pathway is a stepwise process, which proceeds by forming stable intermediate products such as biphenyl and cyclohexylbenzene.
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