Synthesis of MnOx/Oxidized-MWNTs for Abatement of Nitrogen Oxides Mahnaz Pourkhalil • Abdolsamad Zarringhalam Moghaddam • Alimorad Rashidi • Jafar Towfighi • Kheirollah Jafari Jozani • Hamidreza Bozorgzadeh Received: 17 May 2012 / Accepted: 8 November 2012 / Published online: 27 November 2012 Ó Springer Science+Business Media New York 2012 Abstract A series of manganese oxide catalysts sup- ported on oxidized multi-walled carbon nanotubes for low temperature selective catalytic reduction of nitrogen oxides (NOx) with NH 3 in the presence of excess O 2 was prepared by a simple impregnation method. These catalysts were characterized by N 2 adsorption, TEM, XRD and H 2 -TPR methods. The effects of reaction temperature, MnOx loading, and calcination temperature were investigated. Under the reaction conditions of 483 K, 1 bar, NO = NH 3 = 900 ppm, 5 vol% O 2 , GHSV = 30,000 h -1 , and 12 wt% MnOx, NOx conversion and N 2 selectivity of 91 and 99 %, respectively, were obtained. The LTSCR activity was suppressed in the presence of 100 ppm SO 2 and 2.5 vol% H 2 O at reaction temperatures below 573 K, but it was reversible to its initial level after heating and sweeping the catalyst at 573 K for 2 h in Helium. Keywords Low-temperature SCR  OMWNTs  MnOx  Impregnation  NOx 1 Introduction Nitrogen oxides (NO, NO 2 ) from the exhaust gases of stationary plants and combustion engines remain one of the most serious pollutants. They can contribute to photo- chemical smog, acid rain, the greenhouse effect, and ozone depletion [1–3]. A well-proven method for NOx abatement is selective catalytic reduction (SCR) of NO X with NH 3 in the presence of excess oxygen [4, 5]. The general chem- istry involves the following reactions: 4NH 3 þ 4NO 2 +O 2 ! 4N 2 þ 6H 2 O Standard  SCR ð1Þ 2NH 3 þ NO þ NO 2 ! 2N 2 þ 3H 2 O Fast  SCR ð2Þ V 2 O 5 /TiO 2 or V 2 O 5 –WO 3 /TiO 2 commercial catalysts have been used for NH 3 -SCR at temperatures between 573 and 673 K [6, 7]. The SCR unit must therefore be located upstream of the de-sulfurizer and/or particle removal equipment to avoid reheating of the flue gas. Due to the high concentration of SO 2 and ash dust in this location, the performance and life of the catalyst are significantly reduced. There is great interest in developing new SCR catalysts that are active at temperatures well below 623 K, thereby allowing the SCR unit to be located downstream of the de- sulfurizer and electrostatic precipitators [8, 9]. Various catalysts have been known for low-temperature SCR (LTSCR), including noble metal promoted Fe-ZSM-5 catalysts [2], Mn–V–Ce/AC/C monoliths [10], CuOx/car- bonaceous materials [11], Fe–Ce–Mn/ZSM-5 [12], Iron- based catalysts [13], Mn–Ce/TiO 2 [14], MnOx/Al 2 O 3 [15], MnOx/NaY [16], V 2 O 5 /AC [17], copper-on-carbon cata- lysts [18], MnOx/CeO 2 –TiO 2 [19], and V 2 O 5 /carbon nanotubes [20] with 92 % conversion at 463 K. It is known that V 2 O 5 has high activity for NH 3 -SCR, but also is active for both the undesired oxidation of SO 2 [21] and N 2 O formation [22, 23] therefore, it is preferred to use an alternative metal oxide with high activity and selectivity for N 2 as the desired product. MnOx is known for having various types of labile oxygens, which is necessary for the completion of a catalytic cycle. [24–27]. M. Pourkhalil  A. Zarringhalam Moghaddam (&)  J. Towfighi Chemical Engineering Faculty, Tarbiat Modares University, 14115-143, Tehran, Iran e-mail: zarrin@modares.ac.ir A. Rashidi  K. Jafari Jozani  H. Bozorgzadeh Research Institute of the Petroleum Industry (RIPI), 18745-4163, Tehran, Iran 123 Catal Lett (2013) 143:184–192 DOI 10.1007/s10562-012-0938-6