| 摘要: | PFCs為半導體業及光電業製程所需氣體，由於其全球暖化潛勢(GWP)高且生命週期長，致使其排放問題備受關注。燃燒與觸媒轉化為現行PFCs處理技術中最常被使用者，但燃燒法耗能高且有發生工安意外疑慮；而觸媒轉化法則因觸媒毒化限制其應用。非熱電漿破壞已被證實可有效去除NOx、SOx、VOCs和PFCs，最近更發展出電漿和觸媒之整合技術，不論於污染物去除或潔淨能量生成均有更優異之效能，為極具應用前景之新興技術。 本研究利用介電質放電(DBD)和電漿結合銅鋅觸媒(CPC)處理含SF6或CF4之氣流，旨在探討電漿與觸媒之交互作用機制，以及經電漿處理後之觸媒表面變化。此外，許多研究顯示於電漿添加含O和H之氣體將有助於污染物之去除，有鑑於H2O(g)對於電漿處理PFCs的影響尚未釐清，此部份亦為本研究之另一重點。 實驗結果顯示，觸媒經電漿處理後表面粗糙度增加，該結果有助於催化作用之進行，於相同溫度下，其對於SF6之轉化率較未經電漿處理之觸媒為佳。推論其原因為提升表面粗糙度可增加觸媒之活性位置。另一方面，電漿觸媒系統處理SF6時，將於觸媒表面生成硫化物，若將此觸媒再進行催化作用所得之去除效率較新鮮觸媒為差，證實S對於觸媒產生毒化作用。處理SF6之觸媒經鑑定後，表面生成CuS2、ZnSO4、AlF3、MgF2…等化合物；觸媒與CF4反應後生成C和F等化合物。 於本研究中，DBD對於SF6和CF4之轉化效率分別為93%和32%；CPC系統對於SF6轉化率為85%，CF4則為59%。一般而言，於相同比能量密度下，CPC可獲致較佳之轉化率，然CF4卻呈現相反之趨勢。針對該現象本研究進行如下之實驗：利用含浸法使觸媒表面含有10 wt%之S，將其置入CPC系統並通入CF4（作為F之來源）進行放電，尾氣中可監測出SF6，證實觸媒表面之S於CPC系統中可引發逆反應，導致SF6去除效率下降，然該逆反應於CPC系統中之重要性需更多實驗方能證實。 Due to the extremely high global warming potential (GWP). Emissions of perfluorinated compounds (PFCs) have coused attracted more and more public concern due to their high global warming potential (GWP). Since Kyoto Protocol has come into effect, more efforts need to be made to develop abatement technologies with better performance to effectively reduce PFC emissions. Among the various strategies for PFC removal, destruction is still the most available one. Combustion and catalytic oxidation are commonly used approaches for reducing PFC emissions. However, relatively high fuel cost and potential poisoning of catalyst limit their further application. Non-thermal plasma (NTP) technologies have been successfully demonstrated to be effective in removing a variety of gaseous pollutants, such as NOx, SOx, VOCs, and PFCs. More recently, a promising technology referred to as combined plasma catalysis (CPC) has been developed. The better performance for synthesis gas production and pollutant destruction has been proved in relevant literature. However, the interaction between plasma and catalysis is not fully understood. This study aims at investigating the difference in the destruction mechanisms as well as the change of catalyst surface properties after plasma treatment of SF6 and CF4 in DBD and CPC, respectively. The experimental results indicate that the rougher surface of catalyst after plasma treatment could enhance catalysis, which might result from the catalyst activity due to the increment of active sites on the edges and corners. On the other hand, after treating gas stream containing SF6 with CPC, formation of S on the catalyst surface has been confirmed. In terms of catalysis, such phenomenon will cause negative effect because some active sites are covered with S. Moreover, substances such as CuS2, ZnSO4, AlF3 and MgF2 are also identified on the catalyst surface after plasma treatment. The highest removal efficiencies for SF6 and CF4 obtained with DBD are 93% and 32%, while those achieved with are CPC are 85% and 59%, respectively. It is interesting to find that the removal efficiency for SF6 obtained with DBD is higher that with CPC under the same specific energy density is found in this study. Based on the experimental results of this study, it might stem from the reverse reaction taking place on the surface of catalyst. As for the by-product analysis, the results indicate that SO2F2 and SOF4 are the major products after plasma treatment of SF6. |
