Study On The Elimination Of Formaldehyde At Low Temperatures

Elimination of formaldehyde at ambient temperature had been regarded as an important scientific subject in purification of indoor air.In this study,supported nano-gold catalyst was applied in formaldehyde detoxification based on the previous study in this lab.Two catalytic activity measurement systems,Acetylacetone Spectrophotometric method and GC method,which also can generate formaldehyde gas in proper concentration were designed and established. A series of supported nano-gold catalysts were prepaired using deposition-precipitation method.Important variables in catalysts preparation including gold loading,support effect and calcination conditions were investigated.The optimum preparation condition was identified with respect to the catalytic performance for the oxidation of formaldehyde at ambient temperature.A 4.85%Au/CeO₂ catalyst prepared using deposition-precipitation method,calcined at 500℃for 2h in O₂ atmosphre could convert 450ppm formaldehyde gas by over 85%in ambient temperature.Catalytic activity mechanism of formaldehyde oxidation was investigated using XRD,STEM and XPS and was compared with that of carbon monoxide oxidation.The investigation revealed that the catalytic activity mechanism varied in the two systems. In the CO oxidation system,the activity increace when the gold particle size gets smaller and the active species was constituted by Au^δ+and Au⁰ together,while in the HCHO oxidation system,the activity increase at first and then decrease when the gold particle size gets bigger and Au⁰ was recognized as the main active species.Comparation of fresh and deactivated catalysts using former characterization methods indicated that in the CO oxidation system,deactivation might caused by agglomeration of gold particles and carbonates/formats,while in the HCHO oxidation system,deactivation might caused by agglomeration and formation of C₃H₃CeO₆ which was clearly evidenced in the XRD pattern.