Prospect of SCR denitrification catalyst: nitrogen oxides (NOx) are one of the main pollutants in the atmosphere, which are a great danger to human health and ecological environment.NOx comes from the flue gas produced by fuel combustion, and mainly exists in the form of N2O, NO, N2O3, NO2, N2O4, N2O5, etc. [1], of which NO is the main one, accounting for more than 90% of the total NOx, by In the atmosphere, NO is oxidized to NO2, and NO2 reacts with CHx in the smoke under the condition of ultraviolet radiation to produce a kind of photochemical smog, which is 4-5 times more toxic than NO and is extremely harmful to most human organs, animals and plants. In 2003, China emitted more than 16 million tons of NOx, and in 2012, it reached 21.94 million tons, making it the world's top NOx emitter. Therefore, NOx emission control has become an important task for air pollution control.

The current denitrification technology for industrial application is mainly selective catalytic reduction (SCR) denitrification technology with NH3 as the reducing agent. At present, the commercialized denitrification catalyst is V2O5+WO3(MoO3)/TiO2(anatase) as the active component, the active temperature window of the denitrification catalyst is 300~400℃, which is vulnerable to the influence of SO2 and ash in the flue gas and reduces the life of the denitrification catalyst in the high temperature area, so the high efficiency and low temperature SCR denitrification catalyst has become a hot research topic in recent years. has become a hot research topic in recent years.

Non-carrier manganese (MnOx)-based denitrification catalysts 1) Non-loaded manganese denitrification catalysts consist of only the active component - MnOx or composite denitrification catalysts with MnOx as the main active component with other metal oxides. For the single active component MnOx denitration catalysts, Kapteijn et al [8-9] did a more detailed study on the single component MnOx for the polyvalent and multivalent of Mn, prepared pure MnOx in different valence states and evaluated the catalytic activity of Mn denitration catalysts with different valence states for NH3-SCR reaction. The results showed that MnO2 had the highest catalytic activity and MnO had the lowest catalytic activity; the reaction on Mn2O3 denitration catalyst had the highest N2 selectivity, and the catalytic activity and selectivity of non-carrier type denitration catalysts were closely related to the oxidation state and the degree of crystallization of denitration catalysts.Tang et al [10] studied three different types of carrier-free MnOx denitration catalysts, and the results showed that the denitration The key factors for the high low-temperature activity of the catalysts were the amorphous crystalline state of MnOx and the large specific surface area. The main preparation method of unloaded MnOx denitrification catalysts is co-precipitation (which can obtain a high specific surface area), therefore, the choice of precipitating agent also becomes a factor affecting the performance of denitrification catalysts.