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.