| Summary: | 碩士 === 元智大學 === 化學工程學系 === 91 === In this study, Au/TiO2 catalysts were prepared by either a chemical vapor deposition (CVD) or an impregnation method from one of the Au precursors of AuCl3, AuClP(C2H5)3 and Me2Au(acac). The results showed that Me2Au(acac) is the best precursor for CVD preparation , the AuClP(C2H5)3 next, and AuCl3 is considered inappropriate for CVD. The difference is mainly due to the volatility of different precursors.
The preparation temperature of the Me2Au/TiO2 (CVD) catalysts showed insignificant effect on the CO oxidation. On the other hand, when using AuClP(C2H5)3 as the precursor, a lower operation temperature, eg. 120℃ a more active Au/TiO2 higher catalytic activity for CO oxidation. In addition, the pretreatment condition was found to affect the activity of both AuP/TiO2 and Me2Au/TiO2 catalysts in this investigation. A HTR/C resulted in the must active CO oxidation catalysts comparing to HTR or C pretreatment.
The catalysts prepared by an impregnation method had comparable activity as those by CVD. The catalysis activity after a HTR/C pretreatment followed a sequence as Me2Au/TiO2(IMP)≒AuCl3/TiO2 (IMP)＞Me2Au/TiO2(CVD)＞＞AuP/TiO2(CVD)＞＞AuP/TiO2 (IMP) at 323K. These catalysts were found to have two of Au particles, one observable by XRD analysis and one around 3-5nm as observed by TEM. In DRS UV-Visible analysis, it was found that the catalysts with a Au plasmon resonance peak at higher wavelength showed a better activity. It is suggested that Au electron density can affect the reaction activity, and it can be changed by different precursor, different preparation method and different pretreatment.
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