以水熱法/含浸法合成之V2O5/MCM-41觸媒轉化氣流中戴奧辛、NO及汞之研究; Conversion of Dioxin, NO and Mercury from Gas Streams via V2O5/MCM-41 Catalysts Prepared with Hydrothermal Method / Incipient Wetness Technique

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Title:	以水熱法/含浸法合成之V2O5/MCM-41觸媒轉化氣流中戴奧辛、NO及汞之研究;Conversion of Dioxin, NO and Mercury from Gas Streams via V2O5/MCM-41 Catalysts Prepared with Hydrothermal Method / Incipient Wetness Technique
Authors:	林辰峯;Lin,Chen-Feng
Contributors:	環境工程研究所
Keywords:	戴奧辛;選擇性觸媒還原法;NOx;多重污染物控制;PCDD/F;SCR;multipollutant
Date:	2013-08-23
Issue Date:	2013-10-08 15:36:05 (UTC+8)
Publisher:	國立中央大學
Abstract:	選擇性觸媒還原法是?用NH3為還原劑，將NOx還原為N2以及H2O，目前觸媒技術也應用在戴奧辛之去除與汞的氧化。本研究以MCM-41作為觸媒載體，利用不同合成方法製備觸媒轉化戴奧辛、NO以及汞，藉由MCM-41之高比表面積及高分散性以提升觸媒對污染物之轉化催化效率，達多重污染物控制之目標。研究結果指出在NO去除方面，空間流速、氧含量及觸媒之活性相配比皆會影響NO去除效率，以含浸法合成之5 wt%V2O5/MCM-41 (5VMIWT)觸媒於400oC對NO去除效率達70.7%。副產物測量顯示，操作溫度由250oC上升至400oC時，開始有N2O之生成；當空間流速從10000 hr-1增加至20000 hr-1時，N2O生成量由37.6 ppm下降至34.9 ppm，並進一步發現N2O生成可能由NH3氧化生成。而觸媒之V2O5含量越高也會增加N2O之生成趨勢。以MCM-41為載體之觸媒其N2O之生成潛勢與先前研究相比有減少之趨勢 (Kim et al., 2010)。在元素汞氧化測試方面，以水熱法合成之5 wt%V2O5/MCM-41 (5VMHM)及含浸法合成之5 wt%V2O5/MCM-41 (5VMIWT)觸媒於150oC對元素汞皆有良好之氧化效率，分別達73.9%及87.8%。在戴奧辛去除方面分成實驗室及實廠進行探討，實驗室系統於300oC下對戴奧辛之去除效率測試結果顯示由含浸法合成之5 wt%V2O5/MCM-41 (5VMIWT)觸媒其去除效率高於水熱法合成之5 wt%V2O5/MCM-41 (5VMHM)分別為66.9%及40.1%；實廠戴奧辛去除測試方面，5 wt%V2O5/MCM-41 (5VMHM)於150oC達92.7%，5 wt%V2O5/MCM-41 (5VMIWT) 於300oC達96.5%。實驗室與實廠之戴奧辛去除測試其趨勢相同，以水熱法合成之5 wt%V2O5/MCM-41 (5VMHM)觸媒對戴奧辛去除以吸附為主，而以含浸法合成之5 wt%V2O5/MCM-41 (5VMIWT)觸媒則以破壞為主。本研究指出在轉化氣流中NO、戴奧辛及汞方面皆以含浸法合成之V2O5/MCM-41觸媒較水熱法合成之V2O5/MCM-41觸媒之效果為佳。 Selective catalytic reduction (SCR) with NH3 is regarded as one of the most effective technologies for the abatement of NOx on-board. SCR was mainly applied to remove NOx as initially developed and now it has been used to reduce dioxin emissions and oxidize elemental mercury as well. Presently, using catalysis to abate multipollutants has become one of the mainstream technologies. This study is divided into three parts, including NO conversion, mercury oxidation and dioxin removal. The study investigates the effectiveness of the SCR catalysts (V2O5/MCM-41) prepared with two synthesis methods (incipient wetness technique and hydrothermal method) for converting those three pollutants. The NO conversions achieved with 5wt%V2O5/MCM-41 (5VMIWT) is 70.7% at 400oC. The results indicate that N2O formation is reduced as MCM-41 is applied as the carrier, while the efficiencies of PCDD/Fs removal and elemental mercury oxidation in field tests are relatively high. The best PCDD/F removal efficiencies in field tests achieved with 5wt%V2O5/MCM-41 (5VMHM) is 92.7% at 150oC, and 5wt%V2O5/MCM-41 (5VMIWT) is 96.5% at 300oC. The trends of field and pilot-scale tests are consistent. Removal of dioxins with the catalyst prepared by incipient wetness technique is predominantly based on destruction, while the catalyst prepared by hydrothermal method is predominantly via adsorption. The results indicate that the catalysts prepared by incipient wetness technique is more effective than that of hydrothermal method for conversion of dioxin, NO and mercury from gas streams.
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