摘要
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NO_(x)排放质量浓度小时均值不高于50 mg/m^(3)。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_(x)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MnCeTiO_(x)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MnCeTiO_(x)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Mn^(4+)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MnO_(2)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MnCeTiO_(x)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。
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 Ecological Environment limits the average hourly NO_(x) emission concentration of the sintering head to no more than 50 mg/m^(3).At present,the end treatment technology represented by ammonia selective catalytic reduction is the mainstream technology to reduce NO_(x) emissions in flue gas,and its core is the catalyst.Considering the performance,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 MnCeTiO_(x) 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 MnCeTiO_(x) catalyst with a molar ratio of metal elements of 1∶1∶1 exceeds 90% in the range of 175 to 250℃.The catalyst activity 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 Mn^(4+)and adsorbed oxygen content on the surface of the catalyst increased,and the redox properties 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 MnCeTiO_(x) composite metal oxide catalyst conform to the Langmuir Hinshelwood(L-H)and Eley Rideal(E-R)mechanisms.
作者
赵贺喜
李婕
丁龙
钱立新
龙红明
ZHAO Hexi;LI Jie;DING Long;QIAN Lixin;LONG Hongming(School of Metallurgical Engineering,Anhui University of Technology,Maanshan 243032,Anhui,China;Anhui Province Key Laboratory of Metallurgy Engineering and Resources Recycling,Maanshan 243002,Anhui,China)
出处
《钢铁》
CAS
CSCD
北大核心
2024年第7期169-178,187,共11页
Iron and Steel
基金
国家自然科学基金资助项目(52204332,52174290)。
