Co-doping a metal (Cr, Fe, Co, Ni, Cu, Zn, Ce, and Zr) on Mn/TiO₂ catalyst and its effect on the selective reduction of NO with NH₃ at low-temperatures

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• 作者：Boningari  ; Thirupathi ; Panagiotis G.  ; Smirniotis  ; ;   ; ^{panagiotis.smirniotis@uc.edu}
• 关键词：Low-temperature NH₃-SCR ; Manganese oxide (MnO_x) ; NO ; XPS ; In situ FTIR ; Optimization for NO reduction
• 刊名：Applied Catalysis B: Environmental
• 出版年：2011
• 出版时间：2 November 2011
• 年：2011
• 卷：110
• 期：Complete
• 页码：195-206
• 全文大小：1104 K

文摘

A series of Mn¨CM?TiO₂ (M?= Cr, Fe, Co, Ni, Cu, Zn, Ce, and Zr) catalysts were prepared using incipient wetness technique and investigated for the low-temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen. A combination of various physico-chemical techniques was used to investigate the influence of co-doped metals on the characteristics of Mn/TiO₂ catalyst. The catalytic performance of these materials was compared with respect to the M?Mn atomic ratio in order to examine the correlation between physicochemical characteristics and reactivity of optimized materials. XRD results suggest that metal oxide species exist in a highly dispersed state at a certain level called two-dimensional monolayer coverage. Our XPS results illustrated that the MnO₂ phase is extremely dominant over the Mn₂O₃ phase (Mn⁴⁺/Mn³⁺ = 22.31, 96 % ) in the Mn¨CNi(0.4)/TiO₂ anatase catalyst, whereas Mn₂O₃ phase is in competition with MnO₂ in other catalysts (Mn⁴⁺/Mn³⁺ = 1.34?2.67). H₂-TPR data results are in good accordance with XPS results that the absence of the high-temperature (736 K) peak indicates that the dominant phase is MnO₂ in Mn¨CNi(0.4)/TiO₂ catalyst. This increase in reducibility of manganese and dominant MnO₂ phase seems to be the reason for the superior activity and time on stream patterns of our best catalyst. BET and pore volume measurements revealed high surface area and pore volume of the Mn¨CNi/TiO₂ catalyst. The in situ NH₃-FTIR results suggest that the manganese (Mn/TiO₂) and manganese¨Cnickel (Mn¨CNi/TiO₂) surface sites have only Lewis acidity, with no apparent Br?nsted acidity. The catalytic performance of various Mn¨CM?TiO₂ (M?Mn = 0, 0.2, 0.4, 0.6, 0.8) catalysts was studied for the low-temperature SCR reaction at a range of temperatures (160?40 ¡ãC) under industrial conditions using GHSV = 50,000 h^?. The intrinsic activity of Mn¨CNi/TiO₂ catalyst with M?Mn = 0.4 atomic ratio measured under differential reaction conditions, was found to be highly active, selective and broadening the temperature window for this reaction.