Reaction and Characterization of Low-Temperature Effect of Transition Nanostructure Metal Codoped SCR Catalyst

Hindawi Journal of Nanomaterials Volume 2017, Article ID 7901686, 10 pages https://doi.org/10.1155/2017/7901686 Research Article Reaction and Characterization of Low-Temperature Effect of Transition Nanostructure Metal Codoped SCR Catalyst Ke Yang,1 Weiwei Xiao,1 Quan Xu,1 Jiaojiao Bai,2 Yan Luo,3 Hao Guo,4 Li Cao,1 Wei Cai,1 Peng Pu,1 and Lulu Cai2 1 State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Biogas Upgrading Utilization, China University of Petroleum, Beijing 102249, China 2 Personalized Drug Therapy Key Laboratory of Sichuan Province, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial, People’s Hospital, Chengdu 610072, China 3 Department of Chemical Engineering, West Virginia University, Morgantown, WV 26505, USA 4 Chongqing Institute of Forensic Science, Chongqing 400021, China Correspondence should be addressed to Quan Xu; , Peng Pu; , and Lulu Cai; Received 24 January 2017; Accepted 28 February 2017; Published 20 September 2017 Academic Editor: Jinwei Gao Copyright © 2017 Ke Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Typical p-type semiconductor MnO𝑥 codoped with n-type semiconductors such as CeO2 and V2 O5 was reported to achieve high efficiency in catalytic NO𝑥 removal by NH3 . In this paper, we present novel Mn-Ce codoped V2 O5 /TiO2 catalyst which exhibited an excellent NO conversion efficiency of 90% at 140∘ C. By using this codoped catalyst, the best low-temperature activity was greatly decreased when compared with single Mn- or Ce-doped catalyst. According to the characterization results from BET, XRD, and XPS, the codoped catalyst was composed of both CeO2 and amorphous Mn. The electron circulation formed between doping elements is believed to promote the electron transfer, which may be one of the reasons for excellent low-temperature denitration performance. 1. Introduction NO𝑥 is mainly derived from industrial emissions, traffic emissions, and living emissions. NO𝑥 gases react to form smog and acid rain as well as being central to the formation of tropospheric ozone. It especially can form small solid particles through the secondary chemical reactions that cause serious pollutions to the environment. Therefore, it is necessary to take a denitration treatment for flue gas after combustion. Selective catalytic reduction is the most widely used and effective methods for the removal of NO𝑥 in industrial at present. The main two reactions are presented in the following: 4NO + 4NH3 + O2 󳨀→ 4N2 + 6H2 O 2NO2 + 4NH3 + O2 󳨀→ 3N2 + 6H2 O (1) NH3 and NO almost do not react in the absence of the catalyst; therefore, the catalyst is the key for the whole reaction. V2 O5 /TiO2 and V2 O5 -WO3 /TiO2 (anatase) catalysts operated at 350–400∘ C, with less than 1% V2 O5 loading, have been widely accepted as commercial catalysts [1–3]. Currently, other doped companions such as Mn, Cu, Fe, Ce, Wo, and F [4–8] and morphological changes in the supports can be used to modify the catalyst to achieve high catalytic activity [9–12]. W or Mo doped V2 O5 /TiO2 , considered as the most effective commercial catalyst, is widely used for denitration in power plants and nitric acid plants [13, 14]. However, its narrow activity temperature window forces the selective catalytic reduction (SCR) unit to be installed upstream of the desulfurizer and electrostatic precipitator where high concentrations of SO2 and particle matters can make the catalyst bed layer blocked, accelerating the deactivation of the catalyst [15]. Therefore, there is a rising interest in high 2 Journal of Nanomaterials performance catalysts that can be used at low temperature. MnO𝑥 has attracted significant attention because of its various types of labile oxygen species [16, 17]. Recently, Ce-doped catalyst has been found to reduce the reaction temperature significantly and has high catalytic activity and selectivity [18]. Mn-doped catalyst has shown excellent lowtemperature activity, lower apparent active energy, and better ion dispersion than those of most previously reported SCR catalysts [17, 19]. This research committed to the development of low-temperature catalyst based on the V2 O5 /TiO2 and V2 O5 -CeO2 /TiO2 catalyst, which is the key of the selective catalytic reduction (SCR) to remove NO𝑥 from effluent gas. Laboratory gas distribution was used to simulate the flue gas in the measurement. The feed gas mixture consisted of NH3 500 ppm, NO 500 ppm, 3% O2 (volume fraction), and N2 as the balance gas. The total flow rate was 1000 mL/min controlled by mass flow meters and the GHSV = 10,000 h−1 in each reaction. The concentrations of NO𝑥 were measured at the inlet and outlet by flue gas analyzer to calculate the conversion rate by the following: 2. Materials and Methods where [NO𝑥] = [NO] + [NO2 ] and the in and out indicated the inlet and outlet concentration at steady state, respectively. The data was measured when the reaction reached the steady state (about 20–40 min) at each temperature, which could reduce the errors caused by instability. 2.1. Materials. The low-temperature catalysts in the experiments were prepared with commercial anatase TiO2 (Tianjin Guangfu Pharmaceutical) as carriers, with a specific surface area of 7.03 m2 /g. Ammonium metavanadate (NH4 VO3 ) was used as the precursor of vanadium, cerium nitrate (Ce(NO3 )3 ⋅6H2 O) as the precursor of cerium, and oxalic acid solution as the precursor impregnation solution in the doping process. Manganese acetate (C4 H6 MnO4.4 H2 O), copper nitrate (Cu(NO3 )2.3 H2 O), cobalt nitrate (Co(NO3 )2.6 H2 O), ferric nitrate (Fe(NO3 )3.9 H2 O), and chromium nitrate (Cr(NO3 )3.9 H2 O) were selected to provide Mn, Cu, Co, Fe, and Cr, respectively. All these salts precursors were purchased from Tianjin Guangfu Technology Development Co., Ltd. and Aladdin Technology Co., Ltd. 2.2. Catalyst Preparation. The catalysts with different loadings of vanadium and cerium in the experiment were prepared by a conventional incipient-wetness impregnation method. Firstly, the oxalic acid was dissolved in deionized water and heated to dissolve completely, used as the precursor impregnation solution. Then, a certain quality of ammonium metavanadate was added to the oxalic acid solution and stirred until dissolved completely. A quantitative powder of cerium nitrate was added in the same way, finally, adding the TiO2 powder to the above solution, stirring, and impregnating for 1 hour. The water was evaporated from the solution by a rotary evaporator and dried at 80∘ C for 24 hours. The dried samples were calcined at 500∘ C under the air atmosphere for 2 hours. Then the catalysts were ground and sieved to 20–40 mesh for catalytic performance evaluation. Other metals like Mn, Fe, Cr, etc. were doped in the same way as d (...truncated)