臭氧催化氧化降解低濃度甲醛之研究;Degradation of Low-concentration Formaldehyde via Ozone Catalytic Oxidation

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Title:	臭氧催化氧化降解低濃度甲醛之研究;Degradation of Low-concentration Formaldehyde via Ozone Catalytic Oxidation
Authors:	劉潤雨;Liu, Run-Yu
Contributors:	環境工程研究所
Keywords:	臭氧;甲醛;揮發性有機物;臭氧催化氧化;ozone;formaldehyde;volatile organic compounds;ozone catalytic oxidation
Date:	2021-10-29
Issue Date:	2021-12-07 13:41:56 (UTC+8)
Publisher:	國立中央大學
Abstract:	甲醛為常見的室內污染物，其來源十分廣泛。長期接觸甲醛會造成致敏、致畸、致癌效應，嚴重威脅人們的生命安全，因此通過高效無毒的方式去除甲醛成為亟待解決的問題。在許多脫除甲醛的方法中，臭氧催化氧化法是一種經濟、高效的方法，可通過臭氧在觸媒表面被分解帶來的強氧化性自由基將甲醛氧化為無毒的二氧化碳及水。然而，臭氧同樣作為一種空氣污染物，即使低濃度臭氧也會與空氣中有機物反應產生化學作用，嚴重危害人體及健康環境。因此，在臭氧催化氧化甲醛的研究重難點在於如何開發可在低溫下，將臭氧及甲醛完全氧化的觸媒。其中，錳基氧化物觸媒，由於其相對低廉的價格和優異的性能受到研究人員的廣泛關注。本研究針對錳基觸媒進行改性研究，通過於溶膠-凝膠法合成過程中摻雜過渡金屬(Ce，Ni)製備MnCeNiOx觸媒。通過優化摻雜比例發現，當Mn:Ce:Ni比例為1時觸媒活性最佳。並利用共沉澱法製備的FeOx對觸媒進行改質，進一步提升對甲醛的催化活性。結果顯示FeOx-MnCeNiOx在室溫下，相對濕度90%時，對1,000 ppm的臭氧具有100%的轉化效率。在100℃時可將15 ppm 甲醛完全氧化為二氧化碳和水。同時，在室溫下添加45 ppm的臭氧，對甲醛的轉化率達95%，並且在72 hr的長週期測試中保證其催化效果的穩定性。同時， BET結果顯示添加FeOx導致觸媒比表面積顯著增加。XPS 結果顯示，經由FeOx改質後觸媒中Mn3+,Ce3+及表面吸附氧濃度明顯提升，進而提升觸媒之氧空位數量。同時XRD結果表明，FeOx的添加增強了金屬之間的協同作用，因此對臭氧催化氧化甲醛轉換的正面影響，根據反應前後特性分析結果，提出了可能的臭氧催化氧化甲醛的反應機理。綜上所述，本研究製備了一種在室溫下，對於低濃度甲醛具高催化活性、穩定性的新型觸媒，在未來室內空氣空氣品質治理中，該觸媒具有良好的實際應用前景。;Formaldehyde (HCHO) is a common indoor air pollutant. Long-term exposure to HCHO causes allergic, teratogenic, and carcinogenic effects. Among the methods for removing HCHO, ozone catalytic oxidation (OZCO) is an economical and efficient method, which oxidizes HCHO to CO2 and H2O through the strong oxidizing radical when the ozone is decomposed on catalysts. However, ozone is also an air pollutant, even low concentrations of ozone will react with organic matter in the air to produce adverse effects, which will seriously harm the human body and the environment. Therefore, the key issues in the research of OZCO of HCHO are identified and development of catalyst that completely decompose ozone and HCHO at room temperatures is essential. Among them, the manganese-based oxide catalyst has received extensive attention from researchers due to its relatively low price and excellent performance. In this study, modification of manganese-based catalysts was carried out and MnCeNiOx was prepared by doping transition metals (Ce, Ni) during the sol-gel synthesis process. By optimizing the doping ratio, it is found that the catalyst activity is the best when the ratio of Mn:Ce:Ni is 1. The FeOx prepared by the co-precipitation method is used to modify the catalyst to further enhance the catalytic activity for HCHO removal. The results show that FeOx-MnCeNiOx has a 100% conversion efficiency for 1,000 ppm ozone at room temperature and a relative humidity of 90%. Complete oxidation of 15 ppm HCHO to CO2 and H2O(g) is achieved at 100℃. As 45 ppm of ozone is added at room temperature, the HCHO conversion rate reached 95%, and the stability of its catalytic effect is ensured in the 72 hr long-period test. At the same time, BET, XRD, XPS and other characterization methods proved the beneficial effect of the synergy among various metals in the FeOx-MnCeNiOx catalyst on the conversion of ozone-catalyzed oxidation of HCHO. Meanwhile, the reaction mechanism of ozone-catalyzed oxidation of HCHO is proposed. In summary, this study prepared a new type of catalyst with high catalytic activity and stability for low-concentration HCHO removal at room temperature, and this catalyst has good practical application prospects.
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