改變催化劑和外在環境條件在乙醇蒸氣重組反應中的研究

Abstract

在這篇論文中，我們系統性的研究十種不同的金屬分別是Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt 和 Au)，將其附著在三種不同的金屬氧化物支撐物上來進行氧化乙醇蒸氣重組反應，這三種氧化物支撐物分別是氧化鋁(Al2O3)、氧化鈰(CeO2)和參雜了Dy的鈣鈦礦結構BaZrO3。在各種不同的外界環境條件下來進行反應，像是以不同的乙醇和水的比例、氧氣的改變，能更清楚的了解整個乙醇蒸氣重組反應中，不同催化劑的性能以及它們在反應中可以帶來什麼影響，也可以研究其反應機構。在催化劑的效用中，我們發現Cu、Ag、Au可以幫助乙醇的氧化，而Co、Ni、Pd和Pt可以幫乙醇脫水，另外Ru、Rh、Ir則有助於C-C的斷裂，並產生主要是CO和CO2的副產物，同時也可以有最高的氫氣產率。在支撐物方面，經過煮沸的氧化鋁因為有較高的比表面積和更多的孔洞跟未煮沸的氧化鋁相較起來有更好的反應性在乙重蒸氣重組反應中。CeO2和Dy參雜的BaZrO3則是有較多的氧空穴，讓它們在反應中有較好的反應性。在催化條件下，較高的氧氣和水的乙醇比例可以提高氫氣產率，由於氧氣和水可以幫作在反應中的氧化劑，幫忙乙醇的氧化幫助C-C的鍵斷裂。再者，這被當成氧化劑的兩者會因為CeO2和BZDy中的氧空穴的存在，更加強了它們的交互作用，在反應中會有更好的表現。In this thesis, we systematically examine the oxidative steam reforming of ethanol (OSRE) on 10 metals (Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt and Au) on three oxide supports (Al2O3, CeO2 and Dy-doped BaZrO3) at various operational conditions with different Ethanol to O2 and to H2O ratios to elucidate the effects from catalysts and reagents on the catalytic performance for the better understanding of reaction mechanism. In the effect of catalysts, we found that Cu, Ag and Au can help for the oxidation of ethanol, Co, Ni, Pd and Pt favor dehydration of ethanol and Ru, Rh and Ir will help C-C bond cleavage and produce mainly CO and CO2 with the highest hydrogen yield. For the supports, the boiled Al2O3 with higher surface area and more porocity shows better OSRE performance and un-boiled Al2O3. CeO2 and Dy-doped BaZrO3, on the other hand, improve the OSRE result by their oxygen vacancy. In the effect of catalytic condition, higher O2 and H2O to ethanol ratios can also enhance the hydrogen production, attributable to that these oxidants can help for the C-C bond cleavage for the full oxidation of ethanol based on the side-product analysis. Further more, this enhancement can be amplified on the CeO2 and Dy-doped BaZrO3, attributable to the interaction between these oxidants and oxygen vacancy.