Preparation Of Zeolite Conficed FeO_x@SSZ-13 Catalyst And Performance Of Catalyst For Selective Catalytic Reduction Of NO_x With NH₃

Nitrogen oxides(NOx)is one of the main pollutants of air pollution in China,and it is an important precursor for acid rain,photochemical smog and near-surface ozone pollution.Selective catalytic reduction of NOx with NH3(NH3-SCR)is the most effective technology for removing NOx in the world.For this process,the most widely used catalyst is V2O5-WO3(MoO3)/TiO2,which has shown some problems in the practice application,such as the toxicity of vanadium,narrow operation temperature and the high conversion of SO2 to SO2 et al.Therefore,Many researchers have focused on the design and development of new catalysts in order to obtain excellent green catalysts for denitrification activity and high efficiency against sulfur poisoning.In this paper,SSZ-13 was used as the carrier,and the active component was confined to the molecular sieve pores by coprecipitation method.A new type of FeOx@SSZ-13 catalyst was prepared,and its activity and sulfur resistance were systematically studied.Firstly,the effects of seed crystal,crystallization time and crystallization temperature on the properties of SSZ-13 were studied.The cheap green choline chloride was selected as the template and the SSZ-13 was synthesized by hydrothermal synthesis.According to the XRD characterization results,the optimum process parameters for the synthesis of SSZ-13 were obtained by stirring for 6h under the conditions of seeding and crystallization at 130? for 4 days.Secondly,the effect of the difference of the active components on the internal and external surface positions of SSZ-13 on the denitration activity of the catalyst was investigated.The co-precipitation method was used to prepare the confinced FeOx@SSZ-13 catalyst.Compared to the FeOx@SSZ-13 catalyst prepared by mechanical mixing.(dispersing FeOx on the outer surface of the SSZ-13 support)The confinced FeOx@SSZ-13 catalyst has superior SCR activity,and the conversion rate of NOx can be stabilized at 90%or more in the temperature range of 275? to 400?.XRD,TEM,XPS and other characterization methods were used to study the effect of the confinement effect on the dispersion of active components and the physical and chemical properties of FeOx@SSZ-13 catalyst.The results show that the catalyst prepared by the coprecipitation method can introduce the FeOx active component into the pores of the SSZ-13 molecular sieve with good dispersibility.Iron mainly exists in the form of Fe2+and Fe3+.Moreover,the content of Fe2+is large,the number of oxygen holes is large,and the activation reaction is more intense.Meanwhile,the surface atom and chemical adsorption oxygen Oa content of Fe species is less than that prepared by mechanical mixing method,indicating that FeOx active component enters the channel of SSZ-13.Finally,the effects of the different internal and external surface positions of the active components on the sulfur resistance of the catalyst were investigated.The results showed that about 9%and 11%of NOx loss was observed on the catalyst prepared by the coprecipitation method and the mechanical mixing method in the presence of 200 ppm SO2 at 300?,even in the presence of SO2,the confinced FeOx@SSZ-13 catalyst can also slowly recover from NOx conversion and stabilizes around 97%after 3 hours.The confinement effect enhances the stability and sulfur resistance of the catalyst in the SCR reaction.