Acidification Of Rare Earth Concentrates And NH₃-SCR Performance Of Loaded Metal Compounds

With the development of industrialization,the global air pollution problem is still serious,and the emission of pollutants such as NO_xand SO₂in my country is still serious,which has become an important factor affecting the harmonious development of the ecological environment and the quality of life.It is clear that the importance of NO_xelimination and treatment is increasing,and catalytic denitrification is an effective means of NO_xreduction,of which selective catalytic reduction（NH₃-SCR）with ammonia as denitrifying agent is the most widely used flue gas denitrification technology at present,with the help of catalysts to achieve NO_xdenitrification rates of more than 80-90%.At present,vanadium-based catalysts are the most commonly used commercially,but their active components,V₂O₅,are expensive and have poor water and sulfur resistance,which is easy to cause secondary pollution.Therefore,the development of a green,efficient and stable catalyst has become an urgent and urgent task.First,the modification of rare earth concentrates by ball-milling sulfuric acid leaching increases the acidity of the mineral surface and enhances the acidity.The introduction of SO₄^2-ions has a positive impact on the structure of active components,redox cycles and other properties;mechanical activation the interior of the solid can be in an unstable state,resulting in lattice distortion due to particle refinement.After proper ball milling and acid leaching treatment,the specific surface area of the minerals increased to 20.2 m²/g,the pores increased,and the active substances encapsulated in the minerals were exposed,increasing the reaction sites and active sites,and the denitrification efficiency was up to 59%.On this basis,transition metal Fe and transition metal Cu and Fe bimetals were respectively introduced to support modified minerals.It was found that the activity range of catalysts containing Fe species is generally reflected in the middle and high temperature range.With the introduction of Fe species,the ratio of catalyst samples to the surface area is increased to 30.7 m²/g,and the dispersion of metal oxides is stronger.However,the denitrification activity window of Cu species on the catalyst is generally concentrated in the middle and low temperature range,and has excellent denitrification activity and N₂selectivity,And excellent water resistance and sulfur resistance and other properties.After loading Cu and Fe bimetals by hydrothermal method,the XPS results showed that the Fe²⁺content was 55.7%and the Cu²⁺content was 53%,and it was found that the Cu species did not inhibit the oxide generation and dispersion of Fe species;the specific surface area of the mineral increased to 45.6 m²/g,but the Cu species was partially attached in the pores leading to the reduction of the pore volume;the SEM results showed that the encapsulated active The SEM results show that the encapsulated active substances in the minerals are exposed more and make the active substances dispersed more uniformly,increasing the weak acid active sites.After the acidification modification of the rare earth concentrate,the sample recorded as Cu:Fe 0.75:1 had the highest NO_xconversion efficiency,reaching 96%at 300°C,which was 77%higher than the original ore,and the denitrification activity window was shifted forward and broadened to 275-400°C.In conclusion,a new denitrification catalyst was prepared by ball milling sulfuric acid acidifying modified rare earth concentrate and supporting Cu and Fe bimetals.Compared with the pure material catalyst,the mineral catalyst has more abundant active components,and the preparation process is simple,and the catalyst preparation parameters are optimized,which provides a theoretical basis for the preparation of low-temperature and high-efficiency new denitrification catalysts from Bayan Obo rare earth minerals.