Study On Activated Carbon Supported Low-temperature Selective Reduction Denitrification Catalyst

Nitrogen oxide?NOx?is one of the main atmospheric pollutants,which seriously harms the ecological environment and human health.Selective catalytic reduction?SCR?technology is one of the most effective methods for the removal of NOx from stationary sources.At present,high-temperature SCR technology was well developed,but low-temperature SCR technology has not yet been put into industrialized application in large scale,because of the low catalyst activity and poor resistance to water and sulfur based compounds.Further study is needed in developing low-temperature SCR denitrification catalyst.In this paper,the activated carbon?AC?modified by different methods is used as the support,while Mn is the main active component.The denitrification catalyst operated in the low temperature range of 100 ? to 140 is prepared by the impregnation method.The e? ffects of support modification,the metal active sites as well as reaction conditions on the performance of the denitrification catalyst were studied.The detailed work carried out is as follows:A series of Fe-Mn/AC catalysts were prepared by impregnation method with AC modified by nitric acid,citric acid and oxygen plasma and unmodified AC as the support.The obtained catalysts were characterized by N₂-physical adsorption,Fourier transform infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?.The effect of modification method on the denitrification performance of Fe-Mn/AC catalyst was studied.The results show that the modification on the support enhanced the NH₃ adsorption by regulating the number of C=O functional groups on the surface of AC,thereby improves the reaction rate of low-temperature SCR denitrification;but has no significant effort on physical property of Mn and Fe.The Fe-Mn/AC catalyst treated with nitric acid and citric acid both have an enhanced denitrification rate of ⁹5% at 120 and 8000 h?-1 space velocity.Citric acid is a better choice for support modification for industrial applications.Bimetallic Fe-Mn/AC,Ce-Mn/AC and Co-Mn/AC and Mn/AC catalysts were prepared,and the obtained catalysts were characterized by XRD and H₂-temperature programmed reduction?H₂-TPR?.The denitrification performance of the obtained catalysts were investigated.The results showed that at 120 ? and 8000 h-1 space velocity,all three bimetallic catalysts showed good denitrification performance in comparison with Mn/AC catalyst. Meanwhile,the loading of Fe-Mn/AC was investigated.The catalyst has the best denitrification performance when the loading is 7%.The effects of reaction conditions such as temperature,space velocity,oxygen concentration and SO₂ concentration on the Fe-Mn/AC catalyst modified by nitric acid were studied.The results showed that the denitrification performance of the Fe-Mn/AC increased with temperature,but decreases with the increasement of space velocity.The oxygen content in the flue gas will affect the denitrification performance of the Fe-Mn/AC.The best oxygen content is 5% to10%.Lower O₂ content would result in a significant reduction in the denitrification rate,while higher O₂ content will consume extra NH₃.Fe-Mn/AC catalyst has certain resistance to SO₂,low concentration SO₂ has ignorable effect on the catalytic performance,however,high concentration SO₂ causing irreversible poisoning of the catalyst.