Abstract
汽機車廢氣的排放嚴重影響都市的空氣品質及人體健康。處理汽車廢氣的三元觸媒主要活性成份為稀有且昂貴的鉑、鈀、銠金屬。最近幾年，由於貴金屬可用量的限制，基本金屬觸媒已被重新評估應用於汽車廢氣處理。含銅的觸媒似乎是最有效的基本金屬觸媒之一。本論文的研究主題包含二行程機車排放的粒狀污染物質之催化氧化；熱處理條件對銅-鉻觸媒行一氧化碳及丙烯反應活性的影響；含氧空洞擔體對氧化銅觸媒行CO-NO- O2反應活性提昇的影響。主要目的是希望能獲得更多有關含銅觸媒的基本知識。本實驗中所使用的觸媒都由含浸法製備，觸媒的特性經由X光繞射儀、程溫還原技術、BET表面積測量、銅表面積測量及反應活性測試鑑定。機車粒狀污染物質的特性經由元素分析儀及碳氫化合物的程溫脫附來鑑定之。秤取適量的觸媒放置在一個流動式的石英反應管中，進行程溫氧化或程溫反應。反應後的氣體經由連線的一氧化碳分析儀、一氧化氮分析儀及兩部氣相層析儀分析之。結果顯示Pt-Pd-CuO觸媒對粒狀污染物質的氧化是有效的。在觸媒外表面上CuO和Pt-Pd之間密切的結合會造成協合效應呈現並增加粒狀污染物質的轉化率。具有良好活性的氧化銅觸媒可以由還原氧化循環機構及誘導式顆粒移動機構合理的解釋。於5.0wt.%氧化銅含量以下，較高的銅含量增加氧化銅的還原性並導致較高的催化燃燒活性，證實了還原氧化循環機構。反應後氧化銅觸媒的重新分佈現象，印證了誘導式顆粒移動機構。銅 -鉻/氧化鋁觸媒在氧化氣氛下，經700 ~ 900℃熱處理，結果顯現出不僅對一氧化碳亦對丙烯氧化有活性提昇作用，而這些活性的提昇來自於Cu2- Cr2O4尖晶石相的形成。相對的，在還原氣氛下經700 ~ 900℃熱處理，導致燒結的銅表面但誘導強金屬-擔體作用效應，導致唯有一氧化碳氧化的活性提昇。另外，在氧化鉻物種與氧化銅物種密切結合的條件之下，配位的協合效應出現在一氧化碳的氧化反應。對於CO-NO-O2反應而言，導氧離子材料(YSZ)所擔載的CuO觸媒比起傳統材料(Al2O3)所擔載的觸媒擁有較高的活性。CuO/YSZ觸媒上界面的Cu2O生成是造成在CO-O2或CO-NO2反應中具有優良的催化活性的因素之一。另外，經由YSZ擔體中氧空洞達到氧離子傳送的機構，也被認為是跟CuO/YSZ觸媒在CO-NO2反應中具有優良的催化活性有關。因此CuO/YSZ觸媒被認為具有取代傳統Rh/Al2O3觸媒的潛力。The objective of this work is to investigate the catalyticoxidation of the soot particulates from a two-stroke motorcycleand the effect of the heat-treatment condition on Cu-Crcatalysts for the activity behavior of CO and C3H6 oxidation aswell as the effect of oxygen vacancy on the activityenhancement of CO-NO-O2 reaction over YSZ supported CuOcatalysts. The purpose of this study was to gain furtherknowledge on the copper-containing catalysts. The Pt-Pd-CuOcatalyst was indicated by the results to possibly be effective,for the combustion of motorcycle soot. The high activity of theCuO catalyst could be illustrated by a redox mechanism and aninduced particle-motion mechanism. A redispersion phenomenonof the CuO species was observed and is consistent with theinduced particle-motion mechanism. For the effect of the heat-treatment conditions on Cu-Cr catalysts, calcined at 700 ~900℃ under an oxidizing atmosphere, the formation of Cu2Cr2O4spinel structure resulted in an enhanced activity not only forCO oxidation but also for C3H6 oxidation. On the other hand,treatment in a reducing atmosphere at 700~900℃ produced asintered copper surface but induced a strong metal-supportinteraction that led to an enhancement in activity, but onlyfor CO oxidation. For the CO-NO-O2 reaction, copper oxidesupported on YSZ gives a higher catalytic activity than that onAl2O3. The enhanced activity resulted from the formation ofthe interfacial Cu2O. Additionally, the effect of oxygenvacancy has been elucidated by a mechanism of oxygen-iontransfer via surface oxygen vacancies of YSZ which are locatedat the interface between CuO and YSZ support to promote the CO-O2 or CO-NO2 reaction. Hence, it is suggested that the CuO/YSZcatalyst is a promising substitute for the conventional Rhcatalyst.