| In recent years, indoor air pollution caused by CO and HCHO is increasing seriously. So how to effectively remove CO and HCHO in indoor air has been a challenge for environmental protection field all over the world. Supported nano-gold catalysts are well known for their high activity for CO and HCHO oxidation at low temperatures. Despite the high activity of the catalysts, one problem is that the catalysts generally exhibit a short-term durability under reaction atmosphere, limiting its practical application. Several mechanisms were proposed concerning the catalyst deactivation, such as that resulted from the nano-gold sintering, caused by accumulation of carbonate species on the catalyst surface. To address the problem of nano-gold sintering, strategies such as utilizing mesoporous materials to confine gold particles, using mixed or surface-modified oxide supports, developing new supports like metal phosphates and preparing the supported Au-M bimetallic alloy catalyst have been adopted. These strategies successfully improved the antisintering ability of the catalysts at high temperatures. On the other hand, to address the problem of carbonate accumulation that leads to the catalyst deactivation, strategies such as treating the deactivated Au/TiO2catalyst at elevated temperature to make the carbonate species decomposed so as to regenerate the deactivated catalyst, introducing H2O vapor to the CO oxidation system so as to transform the carbonate species into thermally less stable bicarbonate species have been adopted. While these strategies can make the catalyst regenarate, this will lead to the gold particle size gathering in the process, resulting in irreversible inactivation.In the reaction conditions of1%CO in air and2000ppm HCHO in air with a total flow rate of50ml/min over50mg catalyst at25℃, we inspected the influence of the preparation conditions of Au/Fe2O3on the catalytic activity of CO and HCHO oxidation. The results indicated that the best preparation conditions included the method of deposition-precipitation, while the pH of the preparation liquid was9, and the calcination temperature was250℃. In this condition we prepared the Au/Fe2O3catalyst, CO and HCHO conversion rate were68%and35.2%respectively, showing high low-temperature catalytic activity.The addition of Al to Fe2O3led to a diadochic substitution of Fe in a-Fe2O3by Al and substantial Bronsted acid and Louis acid sites on the support surface. At the same time no any diffraction peak belonging to metal Au could be observed on the XRD patterns of1%Au/Fe2O3and1%Au/Al2O3-Fe2O3, indicating that Au was highly dispersed on the support for the two sample. The CO adsorption capacity was not abviously increased after Al modified, but reduced CO2adsorption capacity.On Al modified1%Au/Fe2O3catalyst, the initial conversion of CO oxidation at room temperature slightly increased, but the stability improved obviously, and therefore we put forward a model that1%Au/Fe2O3modified by Al has a higher activity. As acid sites favor the release of CO2from the catalyst surface, the acid sites play a significant role for the catalyst resisting deactivation being caused by the carbonate species deposition. The addition of Al can inhibit the accumulation of carbonate on the catalyst surface and improve the stability of the catalyst. This approach may give further clues with respect to the design of more stable and active catalyst for the reaction of CO oxidation at lower temperature. |
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