Low-Temperature Catalytic Elimination Of Acetone And Benzene Series On Supported Gold Catalysts

The supported Au/γ-Al₂O₃ catalysts were prepared by deposition-precipitation method for the catalytic elimination of acetone and benzene series(benzene, toluene, dimethyl -benzene).We discussed the effects of gold loadings, pretreatment temperature and pretreatment time on the activity of the catalysts. The catalysts were characterized by SEM, XRD techniques. And the reaction dynamics of the oxidation elimination of benzene series were studied.1. The results of experiment and SEM characterization indicated that the active element on the catalyst was gold. SEM and XRD results showed that the gold is dispersed highly on the surface of the Au/γ-Al₂O₃ catalysts activated by H₂.2. Experiment results showed that the preparation and pretreatment influence the activity of the supported Au/γ-Al₂O₃ catalysts. For the catalytic elimination of acetone, the gold loading of the highest active catalysts is 2.5 wt. % and pretreated under 280℃for 1h in H₂. For the catalytic elimination of benzene, toluene and dimethylbenzene the gold loading of the highest active catalysts is 2.0 wt. % and the best pretreatment temperatures are 280℃, 300℃and 250℃respectively for 1h in H₂.The experiment results showed that the complete conversion temperatures of 7.57 g·m^-3 benzene, 7.49 g·m^-3 toluene and 3.07 g·m^-3dimethylbenzene are at 295℃, 252℃and 235℃respectively over the 0.50g 2.0wt. % Au/γ-Al₂O₃ and the complete conversion temperature of 4.66 g·m^-3 acetone is 140℃over the 0.650g 2.5wt.% Au/γ-Al₂O₃, which are completely mineralized into CO₂ and H₂O .The activity of the catalyst for toluene was not decreased for 45 hours under the best reaction condition, which conversion of toluene was 100%. It shows that the catalysts have high stability. With the concentration of acetone and benzene series stream increased, the temperature of complete oxidation was increased and no new organic compounds were created.3. While the flow rate of methanol stream was within the range of 13.25-29.81 mL·min^-1 and the size of catalysts was smaller than 0.4nm, the influence of the effects of internal and external diffusion of reaction stream was excluded. Our experimental condition conforms to the requests of dynamics experiment. The elimination rate of benzene, toluene and dimethylbenzene increased linearly as the increase of original concentration of in the concentration range of 0.72-2.79×10^-4mol·L^-1 benzene, 3.25-20.30×10^-5mol·L^-1 toluene and 2.42-31.43×10^-5mol·L^-1 dimethylbenzene, respective -ly, which are all quasi-first order reaction. The apparent activation energy of benzene, toluene and dimethylbenzene is 118.47kJ·mol^-1, 101.43kJ·mol^-1 and 85.18kJ·mol^-1 respectively, which is a constant in the range of reaction temperature.