Au/C觸媒製備條件對CO+O2反應催化活性的影響

Effect of Preparation on the CO Oxidation Activity of Au/C Catalysts

林彥德(Yan-De Lin)

指導教授 ： 林昇佃

共同指導教授 ： 葉君棣(Chuin T. Yeh)

元智大學/工程學院/化學工程與材料科學學系/碩士(2009年)

摘要

本研究主要目的在於探討影響Au/C催化CO氧化反應活性的因素，論文的第一部分以初濕含浸(IMP)和沉澱(DP)二種方法製備的Au/C觸媒，探討活化條件於CO+O2催化反應活性的影響，結果發現含浸法製得1% Au/C(IMPe)觸媒活性優於商業Au/C(WGC)與沉澱法製得的觸媒。HTR前處理為這些Au/C觸媒活化最有效的方式，若在HTR前處理之前先經以NaBH4室溫鹼改質，所得1% Au/C(IMPe)觸媒具有最佳的反應活性。EXAFS分析顯示1% Au/C(IMPe)、1% Au/C(DP)和0.8% Au/C(WGC)觸媒經HTR前處理後皆以Au-Au鍵為主，且配位數在8~9.6之間，其結果與XRD、TEM相對照顯示1% Au/C(IMPe) 和0.8% Au/C(WGC)觸媒金微粒粒徑同時含有1-7與24-40 nm二種大小，而1% Au/C(DP)仍以1 nm以下居多。三者活性大小則為1% Au/C(IMPe) > 0.8% Au/C(WGC) > 1% Au/C(DP)。
由於所製得Au/C觸媒的催化活性仍顯著低於氧化物擔載的金觸媒，因此論文第二部分以TiO2改質碳載體與金銀雙金屬兩種方式來嘗試提升Au/C觸媒的活性，其中TiO2改質碳載體可以有效提升觸媒活性，而以7% TiO2/C改質的效果優於3% TiO2/C改質觸媒，且1% Au/7% TiO2/C觸媒經過NaBH4室溫鹼改質再接以HTR處理後催化活性也有如1% Au/C(IMPe)觸媒反應活性的提升效益；而金銀雙金屬觸媒結果未能顯著提升Au/C觸媒催化活性。

關鍵字

Au/C ； CO氧化

並列摘要

This study examined the effect of preparation on the CO oxdation activity of Au/C catalysts. Both incipient-wetness impregnation and deposition-precipitation methods were used to prepare Au/C catalysts which were compared to a commercial 0.8 % Au/C. High-temperature reduction (HTR) pretreatment was found necessary to activate the Au/C catalysts. The activities follow the order of 1% Au/C(IMPe) > 0.8% Au/C(WGC) > 1% Au/C(DP). The Au/C (IMPe) catalyst prepared by ompregnation using ethanol as the solvent exhibited the best activity. The activity of Au/C(IMPe) can be improved further by treating with NaBH4(aq) at room temperature before HTR pretreatment. EXAFS results showed that 1% Au/C(IMPe), 1% Au/C(DP), and 0.8% Au/C(WGC) catalysts after HTR consists mainly of Au-Au with coordination number of 8~9.6. XRD and TEM indicates the co-existence of Au particles in the range of 1-7 and 24-40 nm. The Au particle size of 1% Au/C (DP) is the smallest among the three but the catalyst showed the lowest activity. It suggests that Au particle size is not the only reason affecting the activity.
The CO oxidation activity over Au/C catalysts is poor comparing to Au/TiO2. Therefore, Au/C (IMPe) was modified by the addition of either titanium dioxide or Ag. Results showed that the addition of the second metal of Ag on Au/C had no effect on enhancing CO oxidation activity. On the other ahnd, TiO2 modification of carbon supports enhanced the CO oxidation activity over Au/C catalysts. The 1%Au/ 7%TiO2/C catalyst, treated with NaBH4(aq) and a following HTR, showed higher CO oxidation activity than that of 1% Au/C (IMPe).

並列關鍵字

Au/C ； CO oxidation

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