以金/二氧化鈦觸媒催化富氫氣體中一氧化碳的選擇性氧化

Selective Oxidation of CO in H2-rich Stream over Au/TiO2 Catalyst

游文岳(Wen-Yueh Yu)

指導教授 ： 萬本儒

國立臺灣大學/工學院/化學工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01630

摘要

本論文研究富氫氣體中一氧化碳的選擇性氧化(preferential oxidation of CO in H2-rich stream或PROX)觸媒─研究目的在於製備低溫(低於100 oC)下具有高一氧化碳氧化活性、選擇率，以及良好穩定性的PROX觸媒。文獻回顧的結果指出，具有上述催化表現的觸媒之中，Au/TiO2是最好的選擇之一。
本研究以沈澱沈積法(deposition-precipitation)製備Au/TiO2觸媒，探討的製備變因是在pH值調整時，NaOH(aq)的加入攪拌時間與添加量。觸媒以AA、TEM、EDS、XPS以及 UV-vis作為鑑定工具。反應測試包括了CO氧化與PROX。
反應測試的結果指出，當金溶液濃度為1.72 × 10 -3 M (230 mL)時，0.1 M NaOH(aq)的加入攪拌時間在6 ~ 24 h、添加量在19 ~ 22.5 g間所製備出的Au/TiO2觸媒具有最佳的PROX催化表現。這是因為觸媒上金顆粒粒徑小(TEM的鑑定結果)與幾乎沒有氯的殘留(EDS與XPS的鑑定結果)所造成。
NaOH(aq)加入攪拌時間為24 h的Au/TiO2觸媒，在25 oC下進行理想重組氣體PROX測試中，具有高CO氧化活性(XCO = 100 %)、選擇率(S = 0.75)及良好的穩定性(t = 23 h)。
水氣和/或二氧化碳的存在則被發現會降低上述觸媒的CO氧化活性、但會提高選擇率，而且不會影響穩定性。反應中也發現該影響在水氣和/或二氧化碳移除後便會消失，可見得其影響機制是可逆的。
此外，研究也指出，上述CO氧化活性的抑制可藉由增加觸媒的用量與提升反應溫度進行改善。

關鍵字

低溫 ； 金顆粒粒徑大小 ； 沈澱沈積法 ； 二氧化鈦 ； 氫氧化鈉水溶液加入攪拌時間與添加量 ； 富氫氣體中選擇性氧化一氧化碳 ； 金觸媒 ； 氯殘留 ； 穩定性

並列摘要

This thesis is related to the study of the catalysts for the preferential oxida- tion of CO in H2-rich stream (PROX). The purpose of this research is to pre- pare PROX catalysts with high CO oxidation activity, selectivity and good sta- bility at ambient temperature (below 100 oC). The results of literature review indicated that Au/TiO2 catalyst is one of the best choices for above-mentioned catalytic performance.
In this research, Au/TiO2 was prepared by deposition-precipitation. The preparation conditions to be investigated were the stirring time and amount of NaOH(aq) addition during pH adjustment. Catalysts were characterized with AA, TEM, EDS, XPS and UV-vis. The reaction tests included CO oxidation and PROX.
The results of reaction tests pointed out that when the gold concentration of gold solution was 1.72 × 10 -3 M (230 mL), the Au/TiO2 catalysts prepared with the proper stirring time (between 6 to 24 h) and amount (between 19 to 22.5 g) of 0.1 M NaOH(aq) addition during pH adjustment possessed best cat- alytic performance for PROX. This was attributed to the small gold particle sizes (characterized with TEM) and very few chloride residual (characterized with EDS and XPS) over catalysts.
Au/TiO2 catalyst prepared with 24 h as stirring time of NaOH(aq) addition possessed high CO oxidation activity (XCO = 100 %), selectivity (S = 0.75) and good stability (t = 23 h) in idealized reformate for PROX test at 25 oC.
The presence of H2O and/or CO2 were found to decrease the CO oxidation activity, but increase the selectivity and not influence the stability of catalysts mentioned above. The effects were also found to be vanished after the remo- val of H2O and/or CO2 in reaction. It was clear that the mechanism of effect was reversible.
Besides, research also revealed that the foregoing reduction of CO oxida- tion activity can be improved by increasing the catalysts amount and reaction temperature.

並列關鍵字

stability ； gold catalyst ； stirring time and amount of NaOH(aq) addition ； gold particle size ； chloride residual ； PROX ； TiO2 ； deposition-precipitation ； ambient temperature

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