Preparation And Performance Of Au/MO_x Catalyst For CO And HCHO Oxidation

Supported gold catalysts exhibited fine catalystic active for variety reactions, including oxidation of low temperature of carbon monoxide and volatile organic compounds, water-gas shift and some other selective oxidation reaction. So the research on gold catalyst has been the focus due to the fine application potentials of industrial and environmental protection.In this paper, the different preparation methods were used to prepare gold catalysts based on NiO and Co₃O₄ supports, then, the aqueous precipitation and deposition-precipitation method were used to prepare Au/MO_x catalysts supported on NiO,Co₃O₄,ZrO₂ and CeO₂ respectively. The effect of preparation method and the preparation condition of support on the catalyst activity was investigated. The catalytic combustion of CO (or HCHO) was taken as the probe reaction for comparing the catalyst activity. The BET, XRD, XPS, TPR and AAS were carried out to analyze the influence factor on the catalysts activity. And the influence of pre-treatment conditions on the catalysts activity was studied over Au/ ZrO₂ and Au/ CeO₂.The results indicated that:1. The catalytic activity was affected by preparation method distinctly. The catalyst prepared by deposition-precipitation method showed highest activity and the catalyst prepared by impregnation method with deions water washing showed the worst activity.2. The modification in preparation conditions of support also affected the catalyst activity. For Au/NiO,Au/Co₃O₄ and Au/CeO₂, the catalyst activity decreased with the support calcination at high temperature, which was related to the decreasing in the surface area. However, for Au/ZrO₂, the activity increased with the support calcined. XRD results showed that this was related to tetragonal phase structure of support. The catalyst activities related to the dispersant disperse. The use of microwave in the support preparation process could improve the catalytic activity.3. The result of TPR and XPS indicated that addition of gold promoted support reduction and improve catalytic activity. The catalysts contained the oxidized gold and the Au^δ+(0<δ<3 , perhaps Au¹⁺) species was catalytic activity component. The increasing of OH^- content was also beneficial for catalytic activity. 4. The pre-treatment conditions of catalysts also affected the catalyst activity, The optimal conditions for the catalyst were: calcination temperature 250℃, activation temprature 100℃in air for Au/ZrO₂, and calcination temperature 300℃, pre-treatment condition 300℃in air for lh and 4% gold loading for Au/CeO₂.