- 學位論文
鑭系波洛斯凱特觸媒於乙醇與丁醇部分氧化之動力學研究
Kinetics of ethanol and n-butanol partial oxidation over lanthanum-transition metal-based perovskites
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摘要
本論文著眼於波洛斯凱特觸媒於乙醇與丁醇部分氧化之動力學研究。本研究使用物理與化學方法鑑定觸媒的表面和本體。包括結晶構造判定( XRD )、程溫還原分析( H2-TPR )和程溫氧化分析( TPO )。從TPR及TPO發現，LaMnO3為三種不同B-site波洛斯凱特觸媒(LaMnO3、LaCoO3、LaFeO3)中擁有最好氧化還原特性，而LaMn0.95Pd0.05O3具有比LaMnO3更好的還原與再氧化特性。本實驗利用Mars van Krevelen redox cycle機制建立動力學模型，發現表面反應( surface reaction )為此次實驗的速率決定步驟。由動力學分析發現，LaMnO3為三種不同B-site波洛斯凱特觸媒中擁有最低的活化能這是因為LaMnO3擁有較好氧化還原特性並發現LaMn0.95Pd0.05O3與LaMnO3具有相似的活化能(activation energy);而主要差異在於前因子( preexponential factor )。這是因LaMn0.95Pd0.05O3與LaMnO3有相似之組成與結構。而置換少量Pd所提高的氧化還原特性為前因子差異的主因。
並列摘要
The objective of this study is to investigate the kinetics of ethanol and n-butanol partial oxidation over lanthanum transition metal based perovskites, i.e., LaBO3(B= Mn, Co, and Fe) and LaMn0.95Pd0.05O3. Appropriate physicochemical characterizations were used, including x-ray diffraction ( XRD ), temperature-programmed reduction ( TPR ), and temperature-programmed oxidation ( TPO ). The results of TPR and TPO indicate that LaMnO3 shows better redox cycle than LaCoO3 and LaFeO3. LaMn0.95Pd0.05O3 possessed better redox properties than LaMnO3. The kinetic model built on the Mars van Krevelen redox cycle showed that surface reaction is the rate-determining step. LaMnO3 shows lower activation energies than LaCoO3 and LaFeO3 because LaMnO3 have better redox cycle. Similar activation energies were discovered on LaMnO3 and LaMn0.95Pd0.05O3. However, the latter showed greater pre-exponential factor than the former. This can be attributed to the similar chemical composition of structure between LaMnO3 and LaMn0.95Pd0.05O3. The improved redox properties of LaMn0.95Pd0.05O3 is proposed to enhance the pre-exponential factor substantially, and to increase the reactivity.
參考文獻
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