過渡金屬催化劑對乙醇蒸氣重組與氧化蒸氣重組反應之研究

The study of ethanol steam reforming and oxidative steam reforming on transition-metal catalysts

張亦甫(Yi-Fu Chang)

指導教授 ： 王禎翰

國立臺灣師範大學/理學院/化學系/碩士(2010年)

摘要

本研究以 Polyvinylpyrrolidone (PVP)法，來製備以Al2O3為支撐物的Co、Ni、Cu、Ru、Rh、Pd、Ag、Ir、Pt、Au金屬觸媒並利用X-ray 繞射儀(XRD)、能量散射光譜儀(EDS)來分析觸媒特性，應用在乙醇的蒸氣重組反應(Steam reforming)與氧化蒸氣重組(Oxidative steam reforming)的催化，而催化反應在常壓及設定溫度(400℃-600℃)的實驗條件中於石英固定反應床進行。反應產物利用in situ之方式，有系統的以氣相層析儀(Gas Chromatography)進行分析。
實驗結果發現氧化蒸氣重組反應的乙醇轉換效率與氫氣產率在所有實驗設定的溫度範圍中都比蒸氣重組反應來得高，而改變Gas hourly space velocity (GHSV)對反應的影響很小。在催化觸媒中Ru、Rh、Ir有最好的乙醇轉氫能力及最高的氫氣產率，而Cu、Ag、Au 則是有最佳的乙醇氧化能力。
　　另外可以發現Co、Ni、Pd、Pt 在乙醇催化過程中擁有最高的乙烯選擇率可推斷是走乙醇脫水的催化路徑。將實驗配合之前所做的電腦理論計算的結果可以歸納出Ru、Rh、Ir之所以有最高的氫氣產率是因為它們擁有最好的碳-碳鍵結斷裂能力讓乙醇能完全分解；Cu、Ag、Au 有最佳的乙醇氧化能力是歸因於它們的氧化過程中鍵形成的能障最低，Co、Ni、Pd、Pt則是在其表面上有相對較低的碳氧鍵解離能障。

關鍵字

乙醇重組 ； 過渡金屬催化劑 ； 蒸氣重組 ； 氧化蒸氣重組 ； 氫能

並列摘要

In the current research,catalysts of Co、Ni、Cu、Ru、Rh、Pd、Ag、Ir、Pt、Au supported on Al2O3 have been prepared by the Polyvinylpyrrolidone (PVP) method and characterized by XRD,EDS. The experiments of ethanol steam reforming (SRE) and oxidative steam reforming (OSRE) of the catalysts have been carried out in the quartz fixed-bed reactor at the temperature range of 400℃- 600℃ in the ambient pressure. The products have been systematically analyzed by in situ Gas Chromatography (GC) to elucidate the mechanism.
　　The result shows that OSRE has a better conversion efficiency and hydrogen yield than SR in all the temperature range, while Gas hourly space velocity (GHSV) had limited effect on the reaction. Comparing the activity of the catalysts, Ru, Rh and Ir show the best performance with the highest H2 yield; on the other hand, Cu, Ag and Au are good for ethanol oxidation.
　　Furthermore, the other metal catalysts of Co, Ni, Pd and Pt show higher selectivity of C2H4 and might follow the dehydration process. Comparison with previous computational work,the higher H2 yield of Ru, Rh and Ir can 4 be attributed to their lower C-C bond breaking step and results fully decomposition of ethanol. The excellent oxidative ability of Cu, Ag and Au corresponds to the lower bond formation barrier in the oxidation process. Finally, the dehydration process on Co, Ni, Pd and Pt are related to the lower C-O dissociation barriers on these surfaces.

並列關鍵字

ethanol reforming ； transition-metal catalysts ； steam reforming ； oxidative steam reforming ； hydrogen fuel

參考文獻

1. Denis, A.; Grzegorczyk, W.; Gac, W.; Machocki, A., Steam reforming of ethanol over Ni/support catalysts for generation of hydrogen for fuel cell applications. Catalysis Today 2008, 137, 453–459.

2. Assabumrungrata, S.; Pavarajarna, V.; Charojrochkulb, S.; Laosiripojanac, N., Thermodynamic analysis for a solid oxide fuel cell with direct internal reforming fueled by ethanol. Chemical Engineering Science 2004, 59, 6015 – 6020.

3. Vaidya, P. D.; Rodrigues, A. E., Glycerol Reforming for Hydrogen Production:

A Review. Chem. Eng. Technol. 2009, 32, 1463–1469.

4. Zhang, B.; Tang, X.; Li, Y.; Xu, Y.; Shen, W., Hydrogen production from steam reforming of ethanol and glycerol over ceria-supported metal catalysts. International Journal of Hydrogen Energy 2007, 32, 2367 – 2373.