首页|基于MnCeTiOx催化剂的烧结烟气低温脱硝机理

基于MnCeTiOx催化剂的烧结烟气低温脱硝机理

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铁矿烧结工艺是钢铁生产过程中排放氮氧化物的最大源头.由于氮氧化物危害生态环境和影响人类生活,钢铁行业超低排放要求烧结机头NOx排放质量浓度小时均值不高于50 mg/m3.以氨气选择性催化还原法为代表的末端治理技术是目前减少工业烟气中NO,排放的主流技术,其核心是催化剂.综合催化剂性能、成本和使用寿命,过渡金属催化剂成为研究热点.其中,Mn、Ce、Ti的氧化物均具备较强的氧化还原能力,通过共沉淀法制备了一系列MnCeTiOx复合金属氧化物催化剂,研究了不同元素配比对其脱硝活性的影响,并通过对催化剂的物理化学性质分析,揭示了其获得优良低温活性的机理.结果表明,金属元素物质的量比为1∶1∶1的MnCeTiOx催化剂在175~250 ℃区间脱硝率超过90%,随着Ti和Ce含量增加,催化剂活性下降,而随着Mn含量增加,催化剂脱硝活性提高.Mn、Ce和Ti的物质的量比为8∶1∶1时,催化剂在125~250 ℃脱硝率达到99%,同时具有良好的抗水性能.随着Mn含量增加,催化剂中出现了高价态的氧化锰结晶,催化剂表面孔径减小而孔体积和比表面积增大,催化剂表面Mn4+和吸附氧含量升高,并且氧化还原性能以及表面酸性提升,因此催化剂的低温脱硝活性得到显著提升.催化剂结构中MnO2物相增多和表面酸性变强是M8C1T1催化剂获得优良抗水性的主要原因.NO在MnCe-TiOx复合金属氧化物催化剂表面的反应路径符合Langmuir-Hinshelwood(L-H)和Eley-Rideal(E-R)机理.
Low-temperature denitrification mechanism for sintering flue gas on MnCeTiOx catalyst
The sintering process of iron ore is the biggest source of nitrogen oxide emission in the process of iron and steel production.Because nitrogen oxides harm the environment and affect life and production,the Ministry of Eco-logical Environment limits the average hourly NOx emission concentration of the sintering head to no more than 50 mg/m3.At present,the end treatment technology represented by ammonia selective catalytic reduction is the mainstream technology to reduce NOx emissions in flue gas,and its core is the catalyst.Considering the perfor-mance,cost and service life of catalysts,transition metals have become the focus of research.Among them,the oxides of Mn,Ce and Ti all have strong REDOX capacity,but the catalytic denitrification performance of metal oxides composed of Mn,Ce and Ti has not been systematically studied.Therefore,a string of MnCeTiOx composite metal oxide catalysts were prepared by means of co precipitation,and the impact of different element ratios on their denitrification activity were studied.The mechanism by which the catalysts achieved excellent low-temperature activity was revealed through physicochemical analysis.The results show that the denitrification rate of MnCeTiOx catalyst with a molar ratio of metal elements of 1∶1∶1 exceeds 90%in the range of 175 to 250 ℃.The catalyst activ-ity decreases with increasing Ti and Ce content,while the catalyst denitrification activity increases with increasing Mn content.When the molar ratio of Mn,Ce,and Ti is 8:1∶1,the catalyst exhibits a denitrification rate of 99%at 125-250 ℃ and excellent water resistance.With the increase of Mn content,high valence manganese oxide crystals appeared in the catalyst,the pore size of the catalyst surface decreased while the pore volume and specific surface area increased,the Mn4+and adsorbed oxygen content on the surface of the catalyst increased,and the redox proper-ties as well as the surface acidity were enhanced,so that the low-temperature denitrification activity of the catalysts was significantly improved.The reaction pathways of NO on the surface of MnCeTiOx composite metal oxide cata-lyst conform to the Langmuir Hinshelwood(L-H)and Eley Rideal(E-R)mechanisms.

sintering flue gasMnCeTiOxSCRlow-temperature denitrationwater resistance

赵贺喜、李婕、丁龙、钱立新、龙红明

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安徽工业大学冶金工程学院,安徽马鞍山 243032

冶金工程与资源综合利用安徽省重点实验室,安徽马鞍山 243002

烧结烟气 MnCeTiO 选择性催化还原 低温脱硝 抗水性能

国家自然科学基金资助项目国家自然科学基金资助项目

5220433252174290

2024

钢铁
中国金属学会钢铁研究总院

钢铁

CSTPCD北大核心
影响因子:1.204
ISSN:0449-749X
年,卷(期):2024.59(7)