NSR觸媒結合電漿技術去除NOx之研究

Combining catalysis and non-thermal plasma over a perovskite-like catalyst for NOx storage and reduction

彭瀚萱(Han-Hsuan Peng)

指導教授 ： 張木彬

國立中央大學/工學院/環境工程研究所/碩士(2015年)

摘要

柴油引擎因其高於汽油引擎的燃油效率與較低的二氧化碳排放優勢下，逐漸成為未來趨勢的車種。且柴油引擎所排放的氮氧化物佔所有移動污染源65%，而此一污染物更是柴油引擎所排放之尾氣中，最為人所重視的污染物之一，因此，世界各國無一不積極投入氮氧化物的改善技術。因此本研究擬研發一低溫、低成本、高效率之NSR (NOX Storaged Reduction)觸媒並結合非熱電漿技術針對柴油引擎中之氮氧化物去除進行討論。本研究利用以Sr2MnO4觸媒作為基底，藉鉀、鈷及BaO/Al2O3的添加進行改質，並比較改質之觸媒其活性及物性。研究結果顯示，SrKMn0.8Co0.2O4/BaO/Al2O3觸媒於NO濃度500 ppm、反應溫度300oC、空間流速48000 h-1、氧氣含量5%下具有最佳之NOx吸附能力(209 µmol/g)，但當氧氣含量提高至10%時，觸媒之NOx吸附能力有些微下降，表示觸媒在氧氣含量過多的條件下會使觸媒在短時間內將大量的NO氧化為NO2，進而使觸媒的吸附量下降。而CO2和H2O(g)的添加亦會降低觸媒吸附NOx之能力。在NOx電漿還原方面，當氣體流量 50 sccm，空間流速2000 h-1，施加電壓 6 kV，放電頻率 6 kHz時，放電時間15 sec即可將80%的NOx還原成N2；另外，分別添加H2、CO、CH4及H2O於電漿系統中，對於NOx轉化率並無顯著提升，由此結果顯示，此系統能於不添加還原劑時即可達到良好的NOx去除效率。

關鍵字

氮氧化物 ； NSR ； 非熱電漿 ； Perovskite 型觸媒

並列摘要

Lean-burn engine is a promising technology due to its high efficiency, reliability and durability. However, more nitrogen oxides (NOx) are formed under lean-burn condition. NOx not only causes various adverse effects such as acid rain, photochemical smog, deterioration of water quality and visibility, but also harms human health. Hence, how to effectively reduce NOx emissions at a reasonable cost has become an emerging issue. Several methods have been developed for NOx removal, such as direct decomposition, selective catalytic reduction (SCR), and selection non-catalytic reduction (SNCR). In this study, a new NOx storage and reduction (NSR) system is developed for NOx removal by combining catalyst and non-thermal plasma technology (DBD). In this hybrid system, catalyst is mainly used for oxidizing NO to NO2 and storing them on the surface, while non-thermal plasma is applied as a desorption/ reduction step for converting NO2 into N2. Previous study indicates that the amount of stored NOx is the rate-limiting step for the NSR system. The catalyst with a high NOx storage capacity and good reduction performance need to be developed. In this study, SrKMn0.8Co0.2O4 is supported on BaO/Al2O3 to prepare the catalyst. The adsorption experiment was conducted with the gas stream containing 500 ppm NO and 5% O2 with N2 as carrier gas. The results indicate that NOx is effectively adsorbed on the catalyst and converted to N2 at room temperature by applying non-thermal plasma catalysis (η = 80%) and adding appropriate reducing agent can improve it to 84%. The results show that this hybrid system is promising in removing NOx from gas streams.

並列關鍵字

NOx storage ； Perovskite catalyst ； Non-thermal plasma ； NSR

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