釩/銅金屬活性碳觸媒氮氧化物還原活性之探討

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標題:	釩/銅金屬活性碳觸媒氮氧化物還原活性之探討 Vanadium/Copper embedded activated carbon catalyst for deNOx applications
作者:	吳宗欣
貢獻者:	嘉南藥理科技大學：環境工程與科學系暨研究所陳世雄
關鍵字:	碳觸媒氮氧化物釩銅選擇性觸媒還原法非選擇性觸媒還原法 carbon catalyst NOx Vanadium Copper non-selective catalytic reduction selective catalytic reduction
日期:	2011
上傳時間:	2011-10-26 11:19:12 (UTC+8)
摘要:	本研究利用濕式含浸法將釩、銅、釩/銅單雙活化金屬吸附於農業廢棄物-椰殼纖維中，經固定式熱裂解反應器850℃高溫煅燒製備成釩、銅、釩/銅單雙金屬碳觸媒(VB、CB、NB、VC、VN)，並將碳觸媒運用於選擇性觸媒還原反應(SCR)及非選擇性觸媒還原反應(NSCR)之氮氧化物(NOx)還原。研究中以比表面積分析儀(BET)分析碳觸媒孔隙特性及比表面積大小，以環境掃描式電子顯微鏡(E-SEM)分析碳觸媒表面結構及活化金屬分佈程度，以X射線能量分散光譜儀(EDS)分析於碳觸媒上碳(C)、氮(N)、氧(O)、釩(V)、銅(Cu)元素比例，以X射線繞射儀(XRD)分析碳觸媒之釩、銅金屬氧化物的晶格型態與晶體大小，及以TPD-NO、TPD-NH3、TPD-CH4分析碳觸媒對於還原氣體吸附能力大小，進行吸附氮氧化物還原反應程序，並探討釩/銅雙金屬碳觸媒以含不同陰離子銅金屬、釩/銅含浸比例變化、還原劑比例變化、氣體流量變化、觸媒量變化及還原溫度操作條件下探討於選擇性觸媒還原反應(SCR)及非選擇性觸媒還原反應(NSCR)氮氧化物(NO)還原活性。本研究以碳觸媒進行選擇性觸媒還原法(SCR)及非選擇性觸媒還原法(NSCR)研究結果發現，在眾多碳觸媒中VN5碳觸媒最具有NO還原活性，於SCR反應中於450℃還原反應溫度達100%NO轉化率，在 NSCR反應於500℃還原反應溫度NO轉化率達58%，由SEM分析結果證實於含浸液中添加微量銅金屬確實可促使釩金屬均勻分散於碳觸媒上，促使碳觸媒在NO還原反應過程中增加氣體與還原活性金屬接觸機會，其中以VN碳觸媒最具此特徵，XRD分析結果顯示出VN系列雙金屬碳觸媒，活化金屬以V2O5、V2O3、CuO、Cu0四種晶相燒結於碳觸媒上，且受含浸劑中釩/銅比例之影響，隨含浸劑中釩金屬量增加，主要活化金屬晶相逐漸往具NO還原活性之V2O5晶相發展。且由氣體熱程控脫附(TPD)分析結果發現VN5於600℃脫附反應溫度具有明顯的NO、NH3脫附峰，顯示VN5具有較強NO、NH3吸附能力，證實提高活化金屬分散性確實有助於反應氣體與吸附官能基的接觸機會促使吸附量增加以利進行NO還原反應，BET分析結果顯示VN2碳觸媒比表面積雖達1024 m2/g，但無上述之物化特性，促使VN2碳觸媒呈現較低NO還原活性。本研究結果得知燒結於碳觸媒上活化金屬分散性、活化金屬種類及晶相結構是影響釩/銅型碳觸媒NO還原活性之主要因素，其碳觸媒比表面積並非為主要影響因子。 The coconut shell with impregnating vanadium, copper, vanadium/copper used as raw material to prepare carbon catalysts. The selective catalytic reduction (SCR) and non-selective catalytic reduction (NSCR) activity of carbon catalyst were investigated by considering the preparing conditions. The pore properties of carbon catalyst were investigated by BET analysis. SEM-EDS was used to observe the surface morphology and the distribution of active metal oxides on the surface of catalysts. XRD analysis was made to identify the size and crystal form of metal oxides on the carbon matrix. The thermal progress desorption (TPD) measurements were investigated to evaluate the influence of active metal distribution, crystal form of metal, pore properties of carbon matrix on the affinity between carbon catalyst and test gases. The impregnating metal, metal ratio, anion effect of impregnated salt, and the testing conditions of SCR and NSCR were also investigated in this study. It was found that the VN5 is the most active catalyst in SCR and NSCR tests. In the case of SCR, almost 100% NO reduction can be achieved under testing conditions at 450℃. On the other hand, 58% NO reduction was found in NSCR under testing condition at 500℃. The high conversion rate of NO reduction was due to the well V2O5 distribution on the carbon matrix which is contributed by the copper impregnating. The increase in amount of active siites and adsorption reactant enhanced the NO conversion in SCR. Based on the results of this study; it was found that VN catalysts showed the more reduction activity than VN, VB, and CB catalyst. XRD analysis indicated that impregnating metals present as V2O5, V2O3, CuO, and Cu0 forms on the carbon catalyst. The amount of metal oxides is strongly depending on the impregnating metal ratio in preparation. With increasing the vanadium ratio in preparing solution, more V2O5 was formed on the catalyst which was identified by the XRD analysis. TPD analysis showed the best affinity of NO and NH3 on the VN5 catalyst and a strong desorption peak can be observed in the profile of TPD-NO and TPD-NH3. Those results were evidenced that the active metal distribution and activity of metal plays important role on determining the SCR efficiency on carbon catalyst. In this study, VN2 catalyst showed a large surface area (1024 m2/g) but the poor metal distribution and crystal form limited the activity in SCR. It is concluded that the distribution of active sides, crystal form of active metal, and active metal dominated the SCR and NSCR activity of V/Cu catalyst. The distribution of active sides and crystal form of active metal plays the main role to dominate the efficiency of SCR and NSCR.
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