結合活性碳及鈣鈦礦型觸媒去除氣流中NO及N2O之可行性探討;Removal of NO and N2O by combining activated carbon with perovskite-type catalyst

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題名:	結合活性碳及鈣鈦礦型觸媒去除氣流中NO及N2O之可行性探討;Removal of NO and N2O by combining activated carbon with perovskite-type catalyst
作者:	蔡謹蓮;Tsai, Chin-Lien
貢獻者:	環境工程研究所
關鍵詞:	氮氧化物;一氧化二氮;Perovskite-type觸媒;活性碳;NO直接分解;Nitrogen oxides (NOx);nitrous oxide (N2O);Perovskite-type catalyst;activated carbon;NO decomposition
日期:	2018-08-23
上傳時間:	2018-08-31 15:09:29 (UTC+8)
出版者:	國立中央大學
摘要:	氮氧化物(NOx) 不僅對人體造成健康危害，亦對環境造成不利影響。此外，N2O具有較高的全球暖化潛勢(GWP = 310)和較長的生命週期(150年)，被列為重要的溫室氣體之一。因此，開發有效技術以去除NO及N2O為一大重要議題。本研究以溶膠凝膠法製備三種不同之鈣鈦礦型觸媒，包括一種鈣鈦礦型觸媒La0.7Ce0.3SrNiO4和兩種雙鈣鈦礦型觸媒LaSrFeNiO6和LaBaFeNiO6，並研究了此三種觸媒在氣流中對於NO及N2O之分解效率。結果表明，三種觸媒皆對於NO和N2O的直接分解具有良好的活性。尤其是應用雙鈣鈦礦型觸媒(LaSrFeNiO6或LaBaFeNiO6)時，可在500℃可以達到100％的NO分解效率；在400℃亦可以對N2O的分解效率達到100％。然而，氧氣總是存在在固定污染源的排放煙氣中，氧氣可能佔據觸媒之活性位置並進一步降低觸媒對NO和N2O之分解效率。為了克服氧氣對於觸媒活性所產生之負面影響，本研究結合活性碳及鈣鈦礦型觸媒形成兩段式系統，並用於NO的去除。活性碳具有對NOx分解和吸附的良好性能，且活性碳在加溫情況下與氧氣反應形成一氧化碳，一氧化碳可以作為還原NOx的良好還原劑，並進一步降低氧氣對於鈣鈦礦型觸媒的負面影響。單階段式與兩段式的催化系統分別在不同參數條件下進行活性測試實驗，結果顯示兩段式系統即使在6％O2，5％H2O（g）和50 ppm SO2存在下，此兩段式系統操作於300℃可達100％之NO去除效率。總氣體流量控制在1300 mL / min，相當於10,000 hr-1的空間流速(GHSV)。整體而言，本研究所開發之雙鈣鈦礦型觸媒展現對NO和N2O的高去除效率。總體而言，在兩段式系統中，氧氣毒化觸媒之問題能被有效控制且高NO及N2O之去除效率可以被實現。;Various perovskite-type catalysts including single-type La0.7Ce0.3SrNiO4, and double-type LaSrFeNiO6 and LaBaFeNiO6 have been prepared and investigated for the effectiveness in removing NO and N2O from gas stream. The results indicate that three catalysts developed are of good activity for decomposition of NO and N2O. Especially, 100% NO decomposition efficiency could be achieved at 500℃ as double-type perovskite (LaSrFeNiO6 or LaBaFeNiO6) is applied. Also, N2O decomposition efficiency achieved with double perovskites reaches 100%. However, oxygen always exists in the flue gas of stationary sources to occupy active sites of catalyst and decrease the conversions of NO and N2O. In order to overcome the negative effect of O2 on catalyst activity, activated carbon and double perovskite-type catalysts are combined to form a two-staged system for simultaneous removal of NO. Activated carbon is considered as good material for the treatment of NOx due to its good catalytic property toward removal and adsorption of NOx. More importantly, O2 could react with activated carbon to form CO which can serve as good reducing agent for effective removal of NOx. Decomposition tests of NO and N2O are performed with perovskite-alone and two-staged system (perovskite + activated carbon), respectively. The results obtained indicate that 100% NO removal efficiencies can be achieved at 300oC even in the presence of 6% O2, 5% H2O(g), and 50 ppm SO2. Total gas flow rate is controlled at 1300 mL/min, corresponding to a gas hourly space velocity (GHSV) of 10,000 hr−1. Overall, double perovskite-type catalysts developed show high efficiencies for NO and N2O removal, and they are characterized with XRD, BET, SEM, XPS and H2-TPR. Overall, the results indicate that high NO and N2O removal efficiencies can be achieved with the two-staged system.
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