臺灣博碩士論文加值系統

甲醇不但是生產氫氣的重要原料，也可以經過分解後得到經濟價值高的一氧化碳。本論文主要的目的在探討Cu/Cr/Mn觸媒應用於甲醇分解的動力學及反應機制之研究，並了解中間產物甲酸甲酯的生成與分解對甲醇分解的影響；而以此反應機制為基礎，進行Cu/Cr/Mn觸媒的改質。在觸媒中添加入促進鹼性的金屬La及Ce，與加入易氫吸附的金屬Pt，期望可以有效改善Cu/Cr/Mn觸媒在甲醇分解反應中的活性及選擇性。另外，在甲醇分解實驗中通入固定的微量氧氣進行甲醇部分氧化，觀察氧氣在反應中之選擇性，藉此討論控制H2/CO比例的可行性。
實驗發現，甲酸甲酯為甲醇分解反應中的重要中間產物，其分解之活化能為14.75Kcal/mol，雖然高於甲醇分解的活化能10.23Kcal/mol，但由於甲酸甲酯分解的k0大於甲醇分解近190倍，使甲酸甲酯分解還是有較快的反應速度。但因為甲酸甲酯有高活化能，使其對溫度效應相當敏感，因而升溫有利於甲酸甲酯的快速分解並助於甲醇進一步的反應。
另外，以此反應機制為基礎，在Cu/Cr/Mn中添加入促進鹼性的金屬La及Ce，發現在含浸上述二者金屬後，對Cu/Cr/Mn觸媒於甲醇分解反應中的活性表現有相當的助益，且在反應溫度為225℃時便有90%以上的氫氣選擇率；但在Cu/Cr/Mn觸媒中加入容易氫吸附的金屬Pt後，其掩蓋了大部分的銅表面積並促使銅的晶粒變大，因此抑制了甲醇分解反應的進行。
而在甲醇分解實驗中通入微量氧氣進行甲醇部分氧化， O2/MeOH的進料莫耳比為0.19 : 1，發現在通入氧氣反應後，由於氧氣會先吸附於活性銅上，使甲醇更容易吸附於銅上，因而對甲醇的轉化率有明顯的增加。且在反應溫度為225℃時，甲醇部分氧化便有高達95%以上的氫氣選擇率；且發現加入的氧氣在Cu/Cr/Mn觸媒上，與甲醇分解所得到產物中之一氧化碳反應的選擇相當高，因此有效的消耗了一氧化碳的產量，並提供約一半的反應熱。若可以在進料的氧氣量加以調整，便能有效的控制產物中H2/CO的比例，進而使二氧化碳量有所增加。

Methanol is a raw material for the production of hydrogen and carbon monoxide from its direct decomposition reaction. Decomposition of methanol at 200 to 300OC yields two moles of hydrogen, one mole of carbon monoxide and small amount of carbon dioxide, methane and methyl formate. The objective of this research is to study the kinetics and the mechanisms of methanol decomposition reaction using Cu/Cr/Mn as the catalyst. In the course of this study, we modified the parent catalyst with 1% of and the promoters, La, Ce and Pt to improve catalystic reactivity and selectivity. Furthermore, a fixed amount of oxygen was co-fed with methanol to adjust H2/CO ratio and to reduce energy requirement of the endothermic reaction by converting carbon monoxide into carbon dioxide. The amount of oxygen was fixed to be 20% of the methanol feed.
Methyl formate is the key intermediate of the methanol decomposition reaction. In the decomposition of methyl formate under the same reaction conditions, we found that it had a higher activation energy than that of methanol decomposition reaction (14.75 Kcal/mol for methyl formate; 10.23 Kcal/mol for methanol) and a 190 time larger frequency factor, ko than that of methanol.
It was found that addition of 1% La and Ce promoters to the parent Cu/Cr/Mn catalyst increased the reactivity of the parent catalyst. However, addition of Pt to the parent catalyst gave poor reactivity against our original expectation of its ability to promote hydrogen spillover. Part of the reason was attributed to the growth of copper crystal size and the reduction of copper surface area by the incorporation of Pt metal onto the parent catalyst. The exact course of this de-activation by Pt metal, however, was not clear yet at this moment.
All three catalysts, Cu/Cr/Mn, La/Cu/Cr/Mn, Ce/Cu/Cr/Mn were found to the selective catalysts for the hybrid reaction of partial oxidation and decomposition reaction of methanol; carbon monoxide was selectively oxidized into carbon dioxide with these three catalysts. Therefore, partial oxidation with these catalysts can be used as a mean to help adjust H2/CO ratio and to supply reaction heat to the endothermic reaction of methanol decomposition.

誌 謝 i
中文摘要 ii
Abstract iv
目 錄 vi
圖目錄 ix
表目錄 xi
第一章 緒 論 1
1.1 研究背景 1
1.1.1 高效率之機動車燃料 2
1.1.2 提供工廠直接之H2及CO作為化工製程原料所需 3
1.2 研究方向 5
第二章 文獻回顧 7
2.1 甲醇分解之反應機構 7
2.2 甲醇分解用之觸媒 10
2.3 添加劑對催化反應之影響 12
2.4 觸媒穩定性之探討 14
2.5 膜對甲醇分解之影響 16
2.6 甲醇的部分氧化 17
第三章 實驗方法與步驟 19
3.1 實驗藥品與氣體 19
3.1.1 藥品 19
3.1.2 氣體 19
3.2 觸媒的改質 20
3.2.1 觸媒改質方法 20
3.3.2 觸媒改質步驟 20
3.3 觸媒之特性鑑定 21
3.3.1 BET表面積與孔徑大小分析儀 21
3.3.2 程溫還原系統（Temperature Programmed Reduction） 22
3.3.3 銅表面積測定（N2O化學吸附） 25
3.4 觸媒反應裝置與反應步驟 26
3.4.1 反應裝置 26
3.4.2 反應步驟 27
3.4.3 產物分析 28
3.5 觸媒反應操作步驟與計算 28
3.5.1 操作步驟 28
3.5.2 觸媒活性計算 29
第四章 結果與討論 31
4.1 空白實驗 31
4.2 觸媒物性分析 32
4.2.1 BET總表面積測定 32
4.2.2 N2O/H2滴定法之銅表面積測定 33
4.3 觸媒之活化能計算 34
4.3.1甲醇分解於Cu/Cr/Mn之活化能計算 34
4.3.2 甲酸甲酯分解於Cu/Cr/Mn之活化能計算 46
4.4添加劑對觸媒活性之影響 54
4.4.1 溫度對Cu/Cr/Mn觸媒活性之影響 54
4.4.2 添加劑對Cu/Cr/Mn觸媒活性之影響 57
4.5 甲醇的部分氧化 65
4.5.1 觸媒在甲醇部分氧化之活性表現 66
4.5.2 氧氣對產物選擇率之影響 68
4.5.3 G89/La觸媒於甲醇部分氧化之穩定性 77
第五章 結 論 78
參考文獻 80

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