摘要
白云鄂博稀土尾矿含有Fe、Ce等利于催化脱硝的活性元素,作为天然矿物对环境友好且成本低,是作脱硝催化剂的天然原料,但稀土尾矿催化剂温度窗口较窄(350~450℃)。为拓宽稀土尾矿催化剂的温度窗口,用Ce、Nb、Co改性稀土尾矿,采用水热法制备了一系列Ce-M(Nb,Co)改性稀土尾矿催化剂,探究元素比例及元素种类对脱硝性能的影响。通过BET、XRD、XPS、H_(2)-TPR和NH_(3)-TPD对改性稀土尾矿进行表征分析,并利用原位红外技术对Ce-Co改性稀土尾矿的NH_(3)-SCR机理进行了探究。结果显示,Ce-Nb(2:1)改性稀土尾矿在300~400℃脱硝效率最高为85%,Ce-Co(2:1)改性稀土尾矿在250~400℃脱硝效率能够达到90%。Nb和Co的加入提高了催化剂表面CeCO_(3)F的分散度,暴露更多活性吸附位点。同时,元素之间的相互作用促进了电子的转移,Nb^(5+)的形成阻碍了Ce^(4+)的还原,调节了氧化还原性能,使得Ce-Nb改性稀土尾矿具有优异的N_(2)选择性。而Co的加入提高了催化剂氧化还原能力,使得Co^(3+)增加,进而提高BrΦnsted酸性位的吸附强度,NH^(4+)及Co^(3+)-NH_(2)能够首先与NO反应,形成NH_(3)HNO及NH_(2)NO等中间产物,催化剂表面NH_(3)-SCR同时遵循E-R机理和L-H机理,E-R机理占主导。
Bayan Obo rare earth tailing contains Fe,Ce and other active elements conducive to catalytic denitration.As a natural mineral,it is environment-friendly and low-cost.It is a natural raw material for denitration catalyst,but the temperature window of rare earth tailings catalyst is narrow(350-450℃).In order to broaden the temperature window,a series of Ce-M(Nb,Co) modified rare earth tailings catalysts were prepared by hydrothermal method,the effect of element ratio and element types on denitrification performance is investigated.The modified rare earth tailings were characterized and analyzed by BET,XRD,XPS,H_(2)-TPR and NH_(3)-TPD.Finally,the NH_(3)-SCR mechanism of Ce-Co modified rare earth tailings was explored by in situ DRIFTS technology.The steady-state reaction was carried out at 350℃ and the transient reaction was carried out at 50-400℃,which can analyze the existing forms of adsorbed NH_(3) and NO_(x) species in the catalytic process and their changes with temperature.The results show that the maximum denitration efficiency of Ce-Nb(2:1) modified rare earth tailings is 85%at 300-400℃,and the denitration efficiency of Ce-Co(2:1) modified rare earth tailings can reach 90%at 250-400℃.The addition of Nb and Co improves the dispersion of CeCO_(3F) on the catalyst surface and leads more active adsorption sites exposed.At the same time,the interaction between elements promotes the transfer of electrons.The existence of Nb^(5+) hinders the reduction of Ce^(4+),regulates the redox performance,and makes the Ce-Nb modified rare earth tailings have excellent N_(2) selectivity.The addition of Co improves the redox capacity of the catalyst and increases Co^(3+).Further,the adsorption intensity of BrΦnsted acid sites is improved.NH^(4+) and Co^(3+)-NH_(2) can react with NO first,forming intermediate products such as NH_(3)HNO and NH_(2)NO.NH_(3)-SCR on the catalyst surface follows both E-R mechanism and L-H mechanism,and E-R mechanism is dominant.
作者
侯丽敏
王甜甜
许杰
高红敏
武文斐
Hou Limin;Wang Tiantian;Xu Jie;Gao Hongmin;Wu Wenfei(Key laboratory of Efficient and Clean Combustion,School of Energy and Environment,Inner Mongolia University of Science and Technology,Baotou 014010,China;Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources,Inner Mongolia University of Science and Technology,Baotou 014010,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2023年第7期2588-2598,共11页
Rare Metal Materials and Engineering
基金
国家重点研发计划(2020YFC1909102)
内蒙古自然科学基金(2019ZD13,2020BS05030)
国家自然科学基金(51866013)
内蒙古自治区本级事业单位引进人才科研启动支持经费。
