| 摘要: | 溫室效應氣體（包括CO2、CH4、N2O、CFCs、PFCs…等。）之大量排放導致全球暖化持續加劇。其中，全氟化物(Perfluorinated compounds, PFCs) 被廣泛使用於半導體與光電產業，其全球暖化潛勢(Global warming potential, GWP)高出二氧化碳數千至數萬倍，在PFCs中，C3F8於近年來已逐漸取代CF4及C2F6成為高科技產業CVD腔體清洗之主要製程氣體。在全球環保意識與溫室氣體減排壓力下，製程最佳化、替代化學品、回收再利用及破壞削減等四方向為現階段因應全氟化物減量策略，其中相較於替代化學品的開發不易、回收再利用的高成本，破壞削減為目前較易著手之方向。本研究以電漿結合觸媒進行C3F8氣流之破壞處理，探討放電反應器之內電極與介電材質對C3F8轉化之影響以及非熱電漿結合觸媒反應器去除C3F8之交互作用及反應機制探討。 結果顯示氣流中添加O2有助於轉化C3F8，C3F8轉化效率隨內電極尺寸增大而上升，而螺紋(screw)內電極之放電效果也較平滑表面形式(tube)的管狀(tube)內電極為佳。此外，陶瓷材質介電質之C3F8轉化效率較石英為高，操作於1/2” (screw)內電極與陶瓷材質反應器之情況下，系統最佳的C3F8轉化效率為52 %。於放電產物方面，氣流中添加O2其放電後FT-IR測得主要副產物為CF4；而添加O2與Ar者，可有助於C3F8轉化生成之CF4繼續進行反應，其主要副產物為CF4、COF2、CO與CO2等。此外，本研究結果亦顯示本系統可用於C3F8之去除，放電後氣流對全球暖化的衝擊可獲得改善。 電漿結合觸媒反應器(PCR)去除C3F8在能量效率或CO2選擇率方面均優於填充床反應器(PBR)，且由於上述兩反應之最顯著差異乃在於反應器中之填充顆粒是否具觸媒活性，因此可研判觸媒對於電漿結合觸媒之效能提升具決定性之影響。根據電漿物理、觸媒熱催化與電漿/觸媒之間交互作用等三種觀點，透過模式分析及相關實驗之探討，其結果發現能量效率以及CO2選擇率之改善乃藉由兩種不同之機制，前者乃因電漿所生成的活性物種（如激發態物種、自由基和離子）即使於低溫下亦可誘發觸媒之催化反應；後者則為O3經觸媒分解後所產生之活性物種可進一步將CO氧化成CO2。 Perfluorinated compounds (PFCs) are one greenhouse gases that Kyoto Protocol aimed to reduce to prevent global warming from anthropogenic emissions of various greenhouse gases. Due to the high global warming potential, emissions of PFCs have caused much public concern. PFCs are widely used in the semiconductor and photonic industry for plasma etching and chamber clean. Since Kyoto Protocol has come into effect, more efforts are made to develop more efficient strategies for abating PFCs. Among the various strategies for PFCs abatements, destruction is still the better choices. Non-thermal plasma technologies have been demonstrated to be effective in removing a variety of gaseous pollutants. However, the performance of the plasma system still has some room for improvement. The energy efficiency and product selectivity are the drawbacks which have to be modified. Hence, this study applies nonthermal plasma discharge to remove C¬3F8¬ and investigates the system performance in the various inner electrodes and dielectric material of the reactor for dielectric barrier discharge (DBD), and the interaction of the plasma and catalyst in combined plasma catalysis (CPC). In this study, it is indicated the addition of O2 could enhance the removal efficiency for C3F8. The removal efficiency for C3F8 increases with the size of the inner electrode, and the “screw” shape of the inner electrode could have better performance. As for the dielectric material, ceramic may be better than quartz. The highest removal efficiency for C3F8 is 52 % with the 1/2”(screw) inner electrode, and ceramic, and the major by-product is CF4. Furthermore, the addition of Ar could improve the byproduct, and CF4, COF2, CO, CO2, NO are the major components. It could reduce the impact of global warming caused by PFCs emissions through the treatment of plasma discharge. For C3F8 abatement, the plasma combined with γ-Al2O3 (with catalytic activity, PCR) have a better performance than that with α-Al2O3 (without catalytic activity, PBR). It is interesting to find that the enhancement of the energy efficiency and CO2 selectivity are from different mechanisms. The former is caused by the active species from plasma reaction, and the latter is mainly attributed to the active species from the decomposition of O3 on the surface of the catalyst so that CO could be oxidized to CO2. |
