Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/3345
標題: Oxidation of Propane over Transition Metallic Oxide Catalysts Supported on Multi-Wall Carbon Nanotubes
過渡金屬氧化物擔持於多壁奈米碳管之丙烷氧化反應研究
作者: 吳健偉
Wu, Cheng-Wei
關鍵字: Carbon nanotubes;奈米碳管;Propane oxidation reaction;丙烷氧化反應
出版社: 化學工程學系
摘要: 
奈米碳管由於具有較小的質量密度、大的比表面積、獨特的電子、孔洞結構和吸附性等性質,受到研究人員廣泛的注意與應用。由文獻得知,將奈米碳管作為載體於催化反應中,皆有不錯的催化性能。
研究中將奈米碳管作為載體,配合含浸法製備觸媒,進行丙烷氧化反應初步研究。本研究發現對奈米碳管進行表面處理時,能有效除去奈米碳管殘留之觸媒及不定形碳而提高奈米碳管之純度、比表面積、改善奈米碳管孔洞結構、使其表面產生含氧基團以增加親水性。分析擔持釩、鉻、鉬等不同含量金屬氧化物對被擔持金屬氧化物觸媒結構特性之影響,經由表面積與孔洞分佈儀(BET)、熱重量分析儀(TGA) 、X光繞射儀(XRD)及拉曼光譜儀(Raman)之測試結果顯示,被擔持金屬氧化物觸媒孔徑分佈範圍很大;擔持金屬氧化物的奈米碳管熱穩定性降低;金屬氧化物可能是以V2O5、Cr2O3、MoO3之結晶態及其形成之各金屬表面氧化物層同時存在於奈米碳管表面。
以特性分析結果對被擔持金屬氧化物觸媒進行評估,並進行丙烷氧化反應,利用氣相層析儀分析產物濃度。反應結果主產物為丙烯,副產物為一氧化碳、二氧化碳、甲烷、乙烷、乙烯。歸納反應結果,被擔持氧化鉻觸媒對此反應系統有較高的丙烷轉化率及丙烯產率,從丙烯選擇率來看,則以被擔持氧化鉬觸媒表現較佳。隨著反應溫度增加,觸媒轉化率愈高,而高氧氣進料比時丙烷轉化率也會比低氧氣進料比時高。而丙烯選擇率則隨著反應溫度的上升有下降的趨勢,低氧氣進料比的丙烯選擇率則會較高氧氣進料比的高。隨著氧氣進料比越大丙烷容易過度氧化,而副產物一氧化碳、二氧化碳則增多。此外在每一系列之被擔持金屬氧化物觸媒中,丙烷轉化率隨著擔持之金屬氧化物含量增加而上升或至一極大值,可見擔持金屬金屬氧化物含量和催化能力有密切的關係。
在丙烷氧化反應實驗中發現,奈米碳管為載體的觸媒較以活性碳為載體的觸媒結構穩定,熱穩定性也較高,在高溫下進行反應,有較佳的催化性能。

Owing to the properties of lower density, larger specific surface area, unique structure and adsorption, carbon nanotubes (CNTs) has become attractive and extensively applied in many researcher groups. In recent literatures, it has an excellent application in catalysis to use CNTs as a support in different catalytic reactions.
In this study, CNTs are used as a support, and the supported metal oxide catalysts are prepared by impregnation method to perform with the propane oxidation reaction. Upon the surface treatment on CNTs, the original catalysts and the amorphous carbon on CNTs can be removed efficiently and the purity of CNTs can be improved, specific surface area of CNTs and carboxyl groups can be increased and produced to make CNTs more hydrophilic. To analyze the effect of different contents of supported metal (vanadium, molybdenum and chromium) oxide on the CNTs, BET surface area, TGA, XRD and Raman will be used to characterize the structural information of CNTs. From the results, the surface metal oxides may be formed as V2O5, Cr2O3 and MoO3 crystallites, and metal oxide layers on CNTs surface can be coexisted on the CNTs surface.
The concentration of reaction products was detected by GC analysis and determine that the products are propene and by-products, such as CO, CO2, CH4, C2H6 etc. In the catalytic results, the supported chromium oxide catalysts possess a higher conversion and yields among the supported metal oxide catalysts. However, the supported molybdenum oxide catalysts possess a higher selectivity. By increasing temperature, the reaction conversion increases and selectivity goes lower. With the increase of the oxygen feed ratio, the by-products CO and CO2 become increasing. In addition, the propane conversion increases with increasing surface metal oxide concentration in the catalysts and drop off with further increasing the coverage of surface metal oxide. Thus, the catalyst properties are related to the concentrations of metal oxide additive.
In the propane oxidation reaction, the thermal stability of CNTs used as a support is higher than those on active carbon support, and furthermore, it possesses higher catalytic effect at higher temperature condition.
URI: http://hdl.handle.net/11455/3345
Appears in Collections:化學工程學系所

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