Preparation And Performance Of Co₃O₄ Catalysts For Formaldehyde Oxidation At Room Temperature

As one of the most serious indoor air pollutants,formaldehyde has great harm to human's health,and effective removal of indoor formaldehyde has attracted our high attention.Compared with other technologies,catalytic oxidation technology is considered to be the most promising method because of its environmental friendliness,low equipment cost and less secondary pollutants.In this paper,Co₃O₄-based catalysts were studied on the catalytic oxidation of formaldehyde at room temperature.Firstly,Co₃O₄'s catalytic activity was improved by optimizing the preparation conditions of the precipitation method.Secondly,Au/Co₃O₄ catalysts were prepared by co-precipitation method and achieved high efficient removal of formaldehyde at indoor ambient temperature and humidity.Thirdly,the effect of moisture on the catalytic oxidation of formaldehyde was discussed.Finally,Au/Co₃O₄ catalysts were coated on cordierite honeycomb ceramics,and its catalytic performance was tested in a sealed chamber and in a wind tunnel platform.The results showed:?1?By optimizing the preparation conditions of Co₃O₄,100%formaldehyde removal(RH 0%,GHSV 80000 h^-1)and 100%CO₂selectivity were achieved at 70?.The results showed K⁺on Co₃O₄ can promote its catalytic activity.The Co₃O₄ prepared at 25?and calcined at200?showed the best catalytic activity,with the precipitation temperature and the calcination temperature increased,the grain size grew,the specific surface area reduced,and the catalytic activity decreased.?2?In the case of moisture absent,Au-loading significantly reduced the temperature of formaldehyde oxidation,and 60%of formaldehyde were removed at room temperature(25?,RH 0%,GHSV 80000 h^-1)with 100%CO₂ selectivity.When moisture was introduced,over 95%of formaldehyde were oxidized with 100%CO₂ selectivity(25?,RH 70%,GHSV 80000 h^-1),and no activity decrease was observed for more than20 h.XPS results revealed that Au loaded on Co₃O₄ was mainly metallic,and the high catalytic activity of 1.5 wt.%Au/Co₃O₄-300 could be attributed to enhanced O_ads/O_latt ratio,large specific surface area,improved O_adsds capacity and promotion of surface basicity.?3?The results obtained by regulating the reaction conditions revealed that indoor ambient humidity?RH 40%⁷0%?significantly enhanced the catalytic activity of Au/Co₃O₄ and the introduction of moisture promoted the dissociation and desorption of CO₂.In situ DRIFTS indicated that dioxymethylene?DOM?and formate were the main intermediate species,the introduction of moisture promoted the generation and further oxidation of the intermediates.?4?The performance test of the honeycomb ceramics supported Au/Co₃O₄ catalyst showed that 49.2%of formaldehyde was removed in 4h in the sealed chamber.In the wind tunnel,the removal efficiency of formaldehyde was 16%under an airflow velocity at 1.0 m/s.