摘要
This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.
随着人们环保意识的增强,氮氧化物(NO_x)的危害引起广泛关注.NO_x作为首要的大气污染物之一,主要来源于以燃煤电厂为代表的固定源和以机动车为代表的移动源.它不仅能够导致酸雨和光化学烟雾,而且还是PM_(2.5)的重要前驱体,严重危害人类健康和植物生长.因此,NO_x的治理迫在眉睫.研究表明,氨选择性催化还原(NH_3-SCR)技术是控制固定源NO_x排放最经济有效的方法.商业化V_2O_5-WO_3/TiO_2和V_2O_5-MoO_3/TiO_2脱硝催化剂的最佳工作温度窗口为300–400℃.因此,NH_3-SCR脱硝设施通常安装在除尘器和脱硫装置之前以满足最佳工作温度需要.然而,在这种情况下,脱硝催化剂容易因烟气中的飞灰和含硫化合物堵塞、中毒而失活.此外,对于老电厂增加脱硝设施的改造工程,在除尘器和脱硫装置之前没有足够的空间用于安装脱硝设施.因此,开发环境友好型低温NH_3-SCR脱硝催化剂显得尤为重要,因为它可以直接安装在除尘器和脱硫装置之后,从而有效减缓脱硝催化剂失活,有利于改造工程的施工.研究表明,锰基催化剂由于其优异的氧化还原性能和氧迁移能力有利于氧化NO为NO_2,促进反应沿着'快速NH_3-SCR'途径进行,从而表现出优异的低温脱硝性能.然而,其N2选择性、抗水性能和工作温度窗口还有待改善.因此,开发既具有高催化活性又具有宽工作温度窗口、优异抗水性能以及理想N2选择性的低温脱硝催化剂仍是一个富有挑战性的课题.二氧化铈(CeO_2)由于具有优异的氧化还原性能、良好的储/释氧能力、丰富的氧空位以及Ce^(4+)/Ce^(3+)的轻易切换而被广泛用于NH_3-SCR反应.因此,将锰氧化物(MnO_x)与CeO_2相结合而制备的MnO_x-CeO_2催化剂可能会表现出优异的低温脱硝性能.而催化剂的理化性质和催化性能还强烈地依赖于其制备方法.因此,本文采用不同方法(机械混合法、浸渍法、水热法、共沉淀法以
作者
Xiaojiang Yao
Kaili Ma
Weixin Zou
Shenggui He
Jibin An
Fumo Yang
Lin Dong
姚小江;马凯莉;邹伟欣;何圣贵;安继斌;杨复沫;董林(中国科学院重庆绿色智能技术研究院,中国科学院水库水环境重点实验室,重庆400714;南京大学化学化工学院,介观化学教育部重点实验室,江苏南京210093;中国科学院化学研究所,北京分子科学国家实验室,北京100190;重庆文理学院,环境材料与修复技术重庆市重点实验室,重庆402160;中国科学院城市环境研究所,中国科学院区域大气环境研究卓越创新中心,福建厦门361021)
基金
supported by the National Natural Science Foundation of China (No. 21507130)
the Open Project Program of Beijing National Laboratory for Molecular Sciences (No. 20140142)
the Open Project Program of Chongqing Key Laboratory of Environmental Materials and Remediation Technology from Chongqing University of Arts and Sciences (No. CEK1405)
the Open Project Program of Jiangsu Key Laboratory of Vehicle Emissions Control (No. OVEC001)
the Open Project Program of Chongqing Key Laboratory of Catalysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029)
the Chongqing Science & Technology Commission (Nos. cstc2016jcyj A0070, cstc2014pt-gc20002, cstckjcxljrc13)~~
