Study On The Performance Of Composite Catalyst Prepared Based On MnO_x For Catalytic Oxidation Of Formaldehyde At Room Temperatur

Formaldehyde（HCHO）has been globally recognized as the most common hydrocarbon in indoor polluted air,Long-term exposure to HCHO may impose detrimental effect on human health,even at very low ppm levels（0.1～0.4 ppm）.Catalytic oxidation of formaldehyde（HCHO）at ambient temperature is one of the most feasible ways to eliminate indoor HCHO pollution.In this paper,MnCeO_x/attapulgite,Cu MnCeO_x and MnO_x/Mg₄Al₁ catalysts were mainly synthesized with Mn metal elements as the core.The purpose was to realize the adsorption and catalytic degradation of indoor gaseous HCHO under unpowered and ambient temperature conditions.By continuously adjusting the preparation method,molar ratio,calcination temperature,carrier,loading amount and other factors of the catalyst,the catalytic oxidation performance of the catalyst at ambient temperature is improved.These samples were also characterized by XRD,SEM,TEM,BET,EPR,H₂-TPR,XPS and IR techniques to explain the improved activity.The following conclusions were obtained:（1）With MnCeO_x as the active component,an integrated MnCeO_x-attapulgite catalyst（Recipe 4）was prepared by solution mixing.When the loading amount of MnCeO_x is 30 wt%,n（Mn）/n（Ce）=1:4 and the calcination temperature is 550℃,the catalytic oxidation performance of the catalyst at ambient temperature is the best,and the conversion of formaldehyde in 48 h is 95.4%.It also exhibits good compressive strength.（2）Based on CuMnCeO_x catalyst active powder,a series of Cu MnCeO_x catalysts were prepared by complex method with citric acid and hydrothermal method.The results demonstrated that the preparation methods and supports had a significant impact on the surface structure,morphology,oxidation performance of these catalysts.Among them,Cu MnCeO_x-C was synthesized by complex method with citric acid exhibited the highest activity,and the HCHO removal rate reached 98.6%after 48 h.The medium mesoporous structure of Cu MnCeO_x-C catalyst,small crystal size,good reductivity and large specific surface area are conducive to the formation of a large number of oxygen vacancies,oxygen vacancies are the key to catalytic oxidation of formaldehyde.（3）Prepared supported MnO_x/Mg₄Al₁ catalyst with MnO_x as the active component.When the loading amount of MnO_x is 40 wt%,n（Mg）/n（Al）=4:1 and the calcination temperature is 200℃,the catalytic oxidation performance of the catalyst at ambient temperature is the best,and the conversion of formaldehyde in 48 h is 98.5%.The prepared MnO_x/Mg₄Al₁ catalyst has hierarchically structure and high specific surface area.In addition,abundant surface hydroxyl groups of MnO_x/Mg₄Al₁catalyst can act as adsorption centres of HCHO molecules,and the catalyst shows excellent catalytic oxidation performance and good stability.