Study On High Efficiency Direct Decomposition Of NO By Microwave Catalytic Over Perovskite-like Catalysts At Low Temperature

Nitrogen oxides?NO_x?are one of the main atmospheric pollutants,the main cause of the formation of photochemical smog and acid rain,and can directly combine with hemoglobin to cause respiratory diseases.Although the government controls NO_xemissions,which are still huge and pose a serious threat to ecosystems and human health.Therefore,how to remove the NO_x in the exhaust gas is an issue that cann't be ignored in the field of atmospheric environmental protection.At present,the most mature technology applied in industry is NH₃-SCR?Selective Catalytic Reduction?technology.However,this technology still has shortcomings such as the transportation and storage of reducing agent NH₃ is more difficult,secondary pollution is easy to produce,and the catalyst is easily poisoned.Therefore,many researchers are committed to developing more efficient and environmentally friendly denitrification technologies.Direct decomposition of NO does not require the addition of additional reducing agents.The resulting products are non-toxic and harmless N₂ and O₂.It is considered to be the most potential and greenest denitration method.However,the activation energy required to directly decompose NO is as high as 335 k J/mol,which is difficult to achieve.Therefore,there is a need to develop catalysts that efficiently decompose NO.Perovskite refers to a type of composite metal oxide with A₂BO₄-type structure.It has the advantages of structural stability and tunability,so it is widely used in the research of direct decomposition of NO.In the conventional reaction mode?CRM?,when using a perovskite-like catalyst to directly decompose NO,the required reaction temperature is high,and at high temperatures,oxygen suppression will occur,and the conversion rate of NO is low.Microwaves can accelerate chemical reactions and selectively interact with polar reactant molecules,and perovskite-like materials have good absorbing properties.Therefore,this paper combines the microwave catalyst of perovskite-like microwave with microwave to directly decompose NO,and studies the La-type perovskite with different A and B ion substitutions to decompose NO directly under the microwave reaction mode?MCRM?.Because the perovskite-like ions at the A and B sites are tunable,and the substitution of ions at the A and B sites may have an impact on the catalyst structure,redox capacity,etc.,thereby affecting the activity of directly decomposing NO.Therefore,under MCRM,the effect of reaction temperature,O₂ concentration,water vapor and other factors on the activity of direct decomposition of NO by La-type perovskite catalysts substituted at A and B positions was investigated.At the same time,XRD,SEM,H₂-TPR analysis to study the effect of different A and B ion substitutions on the direct decomposition of NO by the catalyst.Under MCRM,the reaction temperature is 200?,and the NO conversion and N₂ selectivity are the highest over La_0.4Ba_0.6Sr Cu O4 catalyst and both are close to100%.The coexistence of O₂ in the exhaust gas has almost no effect on the direct decomposition of NO over La_0.4Ba_0.6Sr Cu O₄.Moreover,O₂ coexists in the exhaust gas,and the catalyst La_0.4Ba_0.6Sr Cu O₄ can decompose NO directly for about 16 hours,thus achieving denitration reaction at a lower reaction temperature.Through the catalytic denitrification of perovskite under MCRM,the microwave catalytic effect and microwave selective effect are revealed.Microwave irradiation can improve the catalytic activity of the catalyst at low temperature,and at the same time can reduce the reaction temperature,thus showing the microwave catalytic effect.Under microwave irradiation,polar molecules can interact with microwaves,and non-polar molecules cann't interact with microwaves,showing the microwave selective effect.