Preparation And Performance Of Fe₂O₃/ZrTiO₄ Catalyst For NH₃-SCR Denitration Reaction

Since the 21st century,the gross national economy has been rising all the way,and the corresponding environmental pollution is also increasing.The NO_xemissions from mobile and fixed pollution sources have become a difficult problem in China’s environmental issues.Selective catalytic reduction（SCR）technology has become the most commonly used NO_xremoval technology.Due to the shortcomings of commercial V-based catalysts such as narrow operating temperature windows and natural toxicity,they are prone to secondary pollution.In order to overcome this shortcoming,a new type of Fe₂O₃/ZrTiO₄catalyst was prepared by coprecipitate method and impregnation method using Fe₂O₃as the active component and ZrTiO₄as the catalyst support.The green environmental protection NH₃-SCR catalyst with excellent catalytic performance at middle temperature was developed.The catalysts were characterized by SEM,XRD,N₂adsorption analysis,XPS,H₂-TPR,and NH₃-TPD experiments.Finally,the high-temperature reaction mechanism ofα%Fe₂O₃/ZrTiO₄catalyst was deeply investigated.The specific content of this article is as follows:（1）In this paper,ZrTiO₄-T（T=500,600,700,800℃）catalyst carriers were prepared by coprecipitation method.The four samples showed a fluffy and porous morphology,with a large number of pores on the surface.XRD test shows that when T=500℃,the crystallinity of ZrTiO₄-500 sample is low,and the content of free species on the surface of the sample is high.In addition,the BET results show that the ZrTiO₄-500 sample has the largest specific surface area and pore volume at T=500℃,which are 166.493 m²/g and 0.386 cm³/g,respectively,and their size determines the denitrification performance of the SCR catalyst.（2）The catalytic performance of the ZrTiO₄-500 sample was obtained through SCR activity testing.The NO_xconversion rate of the sample increased with the increase of temperature between 100-500℃,reaching 86%at 500℃,and the N₂selectivity was greater than 80%between 100-500℃.The NH₃conversion rate increased with the increase of temperature,and the N₂O emissions also increased with the increase of temperature.（3）α%Fe₂O₃/ZrTiO₄（α=8,12,15）catalyst was prepared by impregnation method using ZrTiO₄-500 as the catalyst carrier.All samples showed a fluffy and porous morphology,with a large number of pores on the surface.The NO_xconversion rate ofα%Fe₂O₃/ZrTiO₄catalyst is greater than 80%between 300-400℃,among which 12%Fe₂O₃/ZrTiO₄catalyst has the optimal SCR activity,with a NO_xconversion rate greater than 80%between 250-400℃,and a N₂selectivity greater than 90%over the entire temperature range.（4）The corresponding physicochemical properties of ZrTiO₄-500 andα%Fe₂O₃/ZrTiO₄（8,12,15）catalysts were characterized.Through N₂adsorption and desorption experiments,the results show thatα%Fe₂O₃/ZrTiO₄catalyst is a typical mesoporous structure,and 12%Fe₂O₃/ZrTiO₄catalyst has the largest specific surface area and pore volume,respectively,of 139.6 m²/g and 0.769 cm³/g.In addition,the redox performance and surface acidity ofα%Fe₂O₃/ZrTiO₄catalyst were effectively enhanced due to the electron transfer between the active component Fe₂O₃and the support ZrTiO₄.（5）Through the steady-state adsorption experiment of NH₃at elevated temperature,it was determined that the adsorbed NH₃species on the surface of 12%Fe₂O₃/ZrTiO₄catalyst can stably exist between 50-300℃;Through the steady state adsorption experiment of NO_xat elevated temperature,it is determined that some adsorbed NO_xspecies on the surface of 12%Fe₂O₃/ZrTiO₄catalyst will undergo desorption phenomenon due to the increase in temperature at 50-300℃,and cannot exist stably.Through the transient SCR reaction of DRIFTS,it was determined that the12%Fe₂O₃/ZrTiO₄catalyst followed the Eley-Rideal（E-R）reaction mechanism at300℃,that is,adsorbed NH₃species directly react with gaseous NO_x.