Nanosized Au supported on three-dimensionally ordered mesoporous β-MnO2: Highly active catalysts for the low-temperature oxidation of carbon monoxide, benzene, and toluene
Nanosized Au supported on three-dimensionally ordered mesoporous β-MnO2: Highly active catalysts for the low-temperature oxidation of carbon monoxide, benzene, and toluene
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DOI：
10.1016/j.micromeso.2013.01.007
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发表时间：
2013-05
影响因子：
5.2
通讯作者：
Qing Ye;Jiansheng Zhao;Feifei Huo;DaoXin. Wang;Shuiyuan Cheng;T. Kang;H. Dai
中科院分区：
文献类型：
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作者：
Qing Ye;Jiansheng Zhao;Feifei Huo;DaoXin. Wang;Shuiyuan Cheng;T. Kang;H. Dai
分别以尿素、氢氧化钠和碳酸钠为沉淀剂，采用沉积-沉淀法制备了Au负载量为5wt.%的三维有序介孔β-MnO_2负载的Au纳米催化剂(Au/β-MnO_2(尿素)、Au/β-MnO_2(氢氧化钠)和Au/β-[式：见文本])。通过多种分析手段对材料的物化性能进行了表征，并对其对CO、苯和甲苯完全氧化的催化活性进行了评价。结果表明，沉淀剂的性质对β-MnO2载体、Au纳米粒子和Au/β-MnO2催化剂的物化性能有重要影响。在三种Au/β-MnO2样品中，Au/β-MnO2(氢氧化钠)具有最高的表面原子比：Mn3+/Mn4+、OADS/Olatt和Au3+/Au0。金的负载量通过金与β-MnO_2载体之间的强相互作用大大改善了Au/β-MnO_2的还原性能，其中Au/β-MnO_2的低温还原性能最好。负载金使β-MnO_2的催化活性显著提高。3种Au/β-MnO2催化剂的催化性能均优于不含Au的β-MnO2催化剂，其中Au/β-MnO2催化剂的催化活性最好(CO氧化的T50%和T100%分别为48℃和70℃，苯氧化的T50%和T100%分别为48℃和70℃，甲苯氧化的T50%和T100%分别为170℃和220℃)。结果表明，较好的金分散性、较高的表面Au~(3+)和氧浓度、较好的低温还原性能、较强的金与载体的协同作用以及载体的高质量三维有序介孔结构可能是Au/β-MnO_2(氢氧化钠)具有优异催化性能的原因。
Three-dimensionally (3D) ordered mesoporous β-MnO2-supported Au nanocatalysts (Au/β-MnO2(urea), Au/β-MnO2(NaOH), and Au/β- [Formula: see text] ) with an Au loading of 5wt.% were prepared by the deposition–precipitation method using urea, NaOH and Na2CO3as precipitating agent, respectively. The physicochemical properties of the materials were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the complete oxidation of CO, benzene, and toluene. It is shown that the nature of precipitating agent had an important influence on the physicochemical properties of the β-MnO2support, Au nanoparticles, and Au/β-MnO2catalysts. Among the three Au/β-MnO2samples, the Au/β-MnO2(NaOH)showed the highest surface atomic ratios of Mn3+/Mn4+, Oads/Olatt, and Au3+/Au0. The loading of gold could greatly modify the reducibility of Au/β-MnO2via the strong interaction between the gold and the β-MnO2support, and the Au/β-MnO2(NaOH)sample possessed the best low-temperature reducibility. Gold loading resulted in a significant enhancement in catalytic activity of β-MnO2. The three Au/β-MnO2catalysts outperformed the Au-free β-MnO2catalyst, among which the Au/β-MnO2(NaOH)one showed the best catalytic activity (T50%and T100%=48 and 70°C for CO oxidation, 200 and 250°C for benzene oxidation, and 170 and 220°C for toluene oxidation, respectively). It is concluded that factors, such as the better gold dispersion, higher surface Au3+and oxygen adspecies concentrations, better low-temperature reducibility, stronger synergistic action between the gold and the support as well as the high-quality 3D ordered mesoporous structure of the support, might be responsible for the excellent catalytic performance of Au/β-MnO2(NaOH).