Poisoning Effects Of KCl And As₂O₃ On Selective Catalytic Reduction Of NO With NH₃ Over Mn-Ce/AC Catalysts At Low Temperature In Sintered Flue Gas

Nitrogen oxide?NO_x?is a major air pollutant.The selective catalytic reduction of NOx with NH₃ as reductant is one of the most efficient technologies abating NO_x at present.Catalysts are critical to selective catalytic reduction of NO_x,they affect the NO_x removal and economical efficiency of the whole SCR system.In recent years,according to the characteristics of low-temperature sintering flue gas,denitrification at low temperature and catalysts with carbon materials as the carrier and excessive group metal oxides?MnO_x,CeO_x,etc.?as the active components have become research hotspots.The harmful components in sintered flue gas are numerous and complex.Therefore,it is of great theoretical and practical value to study the behavior of alkali metal?K,Na?and arsenic in flue gas and the mechanism of catalyst poisoning and deactivation.In this study,single and combined effects of KCl and As₂O₃ over Mn-Ce/AC catalysts have been investigated.The effect of KCl and As₂O₃ on Mn-Ce/AC denitrification catalyst activity was studied from 100?to 250?.The prepared samples were widely detected by characterization of SEM,BET,XRD,XPS,NH₃-TPD andFTIR.The substantial changes in Mn-Ce/AC catalysts caused by KCl and As₂O₃were explored and the mechanism of their synergistic effect was revealed.The main results are shown as following:Deactivation for KCl doping catalyst was observed and stronger poisonousness was found with the increasing doping of KCl.Characterization results showed that KCl destroyed the porosity of active carbon and decreased the BET surface area,total pore volume and average pore diameter.The amount of chemisorbed oxygen and Ce³⁺also decreased.Besides,KCl could react with-OH and C=O on the surface of AC to ultimately form-O-K and Cl-C-O-K,resulting in the decrease of NH₃and NO adsorption and deactivation of Mn-Ce/AC catalysts.Strong deactivation for As₂O₃ doping catalyst was observed.As₂O₃ was oxidized to As₂O₅ in the process of denitration.Some layer was formed on the surface of catalyst.The decrease of BET surface area,total pore volume and the surface acidity of Mn-Ce/AC catalyst were the main reasons of poisoning.There is competitive adsorption against the consumption of O?a?between the denitration process and the oxidation of As³⁺.As₂O₃ also changed the Ce atomic chemical state on the surface of the catalyst,hindering the redox cycle between the active components:Mn²⁺+Mn³⁺+4Ce⁴⁺?3Mn⁴⁺+2Ce³⁺.Severe synergistic inactivation occurred with the common effect of KCl and As₂O₃on the catalyst.It could be seen from the micrograph of co-doped KCl and As₂O₃catalysts that a lot of agglomeration and collapse of pore structure were observed,leading to further reduction of BET surface area,total pore volume and chemisorbed oxygen.The presence of As₂O₃ had no obvious influence on the binding behavior of KCl with oxygen-containing functional groups,but KCl occupied the oxygen vacancy on the surface of the catalyst,leading to the reduction of chemical adsorption,thus reducing the oxidation from As³⁺to As⁵⁺,which is the interaction effect of the co-existence of KCl and As₂O₃.