Study On Sulfur Resistance Of NH₃-SCR Catalyst For Rare Earth Concentrate

With the increasing awareness of environmental protection,NO_X emission control has attracte worldwide attention.Selective Catalytic Reduction?SCR?with NH₃ as reducing agent is the most widely use and highly efficient flue gas denitrification technology,and the development of efficient catalysts is the core of NH₃-SCR technology.The catalysts for NO removal by catalytic reduction of rare earth metals are one of the promising catalysts for NO removal.In recent years,a large number of studies have found that modified rare earth concentrate as temperature window of SCR catalyst at 300?3505? has better denitrification performance.However,there are more dust particles and high concentration of SO₂ in boiler flue gas,which can easily cause catalyst deactivation.The poisoning of catalyst will make SCR system replace catalyst prematurely,thus increasing investment cost.Therefore,the study of SO₂ tolerance of catalysts is of great significance to the industrial application of catalysts.In view of the high catalytic activity of rare earth concentrate catalyst,this paper aims at the roasted rare earth concentrate catalyst.The effects of SO₂ concentration and reaction temperature on the denitrification performance of the catalyst were studied.The structure and crystalline phase characteristics of the catalyst before and after reaction in SO₂atmosphere were compared and analyzed,and the effect of SO₂ on the catalyst was explained in detail,in order to provide a strong theoretical basis for the industrial utilization of rare earth concentrate catalyst.In this paper,the harm of NO_X to the environment,the poisoning mechanism of SO₂ to SCR catalyst,the progress of sulfur resistance of SCR catalyst at home and abroad and the comprehensive application of rare earth resources are described.The basis for selecting this topic is determined,and the sulfur resistance of rare earth concentrate catalyst is put forward and further studied.Then,the preparation of catalyst,the equipment involved in the experiment,the experimental device,the gas analysis system and the main characterization and analysis methods are briefly introduced.In this paper,the effects of SO₂ concentration and reaction temperature on the denitrification performance of NH₃-SCR catalyst for rare earth concentrate were studied.The adsorption characteristics of gases in the process of SCR reaction were analyzed by in situ infrared spectroscopy.The results showed that NH₃-SCR catalyst for rare earth concentrate had good sulfur resistance.SO₂ had a significant effect on the denitrification performance of rare earth concentrate catalyst in the temperature range of 300?350?The conversion of NO increased from 29% to 50% at 300? and from 42% to 75% at 350?.In situ FT-IR results showed that the adsorption of SO₂ increased the B acid sites on the surface of the catalyst and enhanced the adsorption capacity of NH₃,which was conducive to improving the activity of the catalyst.SEM,BET,XRD,NH₃-TPD,XRF and XPS were used to characterize the physical structure and chemical properties of the catalyst samples before and after SCR reaction in the presence of SO₂.The results of SEM and BET showed that the surface structure of the catalyst did not change significantly after reaction in the atmosphere of SO₂,and the surface area and pore size decreased slightly,but it was not enough to affect the activity of the catalyst.XRD and XPS results show that SO₂ has no effect on the crystal phase and grain size of the catalyst,and does not affect the crystal structure of the catalyst.The effect of SO₂ on the catalyst has no effect on the formation of metal sulfate or the change of the valence state of the active metal.No new substance has been formed in the catalyst,and the active center atoms have not been sulfated.Finally,it summarizes the full text,and provides guidance for others to study relevant content in the future.