焙烧条件对Ru/AC催化剂去除溴酸盐的影响

考察了以RuCl₃·3H₂O为前驱物,以AC(颗粒活性炭)为载体制备Ru/AC时,焙烧氛围、焙烧温度、焙烧时间对Ru/AC催化活性的影响,并利用XPS(X-ray photoelectron spectra,X射线光电子能谱分析)、BET(brunner-emmet-teller method,比表面积测定)和SEM(scanning electronic microscopy,扫描电镜)等手段对样品进行了表征. 结果表明,不同焙烧氛围中制备的Ru/AC活性有较大差异:在N₂焙烧氛围中,容易形成去除BrO₃-的有效活性组分(RuO₂)；而在真空焙烧氛围中,几乎没有活性组分的产生；在H₂-N₂〔φ(H₂)为1.5%,φ(N₂)为98.5%〕氛围中焙烧,负载在AC上的活性组分有Ru₀(单质钌)和RuO₂. 焙烧温度对Ru/AC去除BrO₃-的性能有着较为显著的影响,高温有利于AC的石墨化进程,载体性能得到优化；但焙烧温度过高(1 000 ℃)时,会产生金属颗粒团聚现象；最适宜的焙烧温度为900 ℃. Ru/AC的活性随着焙烧时间的延长呈先增后降的趋势；焙烧时间为3 h时,载体的比表面积和孔容积得到提高且有效活性组分能够均匀地分散在AC载体上. 综上,Ru/AC催化剂的最优焙烧条件:焙烧氛围为N₂,焙烧温度为900 ℃,焙烧时间为3 h. 在该条件下制备的Ru/AC利于形成去除BrO₃-的活性物质RuO₂,并且其能够均匀地分布在AC载体上,使催化反应进行得更为彻底,可在2 h内将BrO₃-全部去除. 

Effect of Calcination Conditions on the Activity of Activated Carbon Supported with Ruthenium Catalyst for Bromate Reduction

To obtain an activated carbon supported with ruthenium catalyst (Ru/AC) with high catalytic properties for bromate reduction, the effects of calcination conditions on the activity of Ru/AC were investigated. The catalyst was prepared by iso-volumetric impregnation method, in which RuCl₃·3H₂O was used as a precursor and AC as a support. The properties of the catalyst were characterized by XPS (X-ray photoelectron spectra), BET (brunner-emmet-teller method) and SEM (scanning electronic microscopy). The results revealed that the activities of Ru/AC prepared in different calcination atmospheres were obviously different. Ru/AC calcinated in N₂ atmosphere showed the highest activity, because it was easy to form RuO₂, which is the effective component for removing bromate. Vacuum atmosphere was apparently not beneficial for the active components formation. However, in the atmosphere of H₂-N₂(φ(H₂) 1.5% and φ(N₂) 98.5%), two active components were observed:metallic Ru and RuO₂. The calcination temperature greatly affected the activity of the catalyst. The AC support was enhanced under the carbon graphitization at a high temperature, but agglomeration of particles occurred after the temperature increased to 1000 ℃. Thus the optimal calcination temperature was around 900 ℃. The calcination time affected the structure of the support AC and the particle size and dispersion of RuO₂. When calcination time was 3 h, both the BET surface area and pore volume of Ru/AC was increased, and RuO₂ particles were well distributed on/within AC surface or internal pores. Therefore, the optimal calcination condition of Ru/AC catalyst is that the calcination atmosphere is N₂, the calcination temperature is 900 ℃ and calcination time is 3 h. Under this optimal condition, all the bromate could be removed by the Ru/AC in 2 h.