摘要
nm，对这两类样品也考察了通过氧化还原处理调控它们的氧化还原状态及对CO 氧化反应性能的影响，结果显示对于Au/TiO2系列样品，氧化40min获得的催化剂活性最佳，CO完全转化的最低反应温度是80℃；而对于Au/ZrO2系列样品，随着氧化时间延长，其催化剂性能随之下降；两系列催化剂的稳定性测试显示活性随反应时间延长下降较为平缓，再次采用氧化还原处理程序也能使它们的活性恢复。这些结果进一步表明对于氧化物负载的Au催化剂，调控样品的氧化还原状态是改善其催化性能的手段，相对于目前广泛使用的纳米Au催化剂，将Au尺度控制在亚纳米尺度获得Au高度分散的金属/氧化物界面是获得高效、性能可调Au催化剂的重要途径。
关键词：多相催化；贵金属分散度；Au；金属-氧化物界面柚子皮的做法
II
Abstract
Abstract
During recent years,oxide supported Au nanoparticles,such like Au/CeO2,Au/ TiO2,Au/ZrO2,have been considered as promising heterogeneous catalysts in application.In spite of the outstanding performanc春节成都旅游攻略
e,both basic rearch and application progress have been limited by the unclear interface properties of Au nanoparticles and their influence to catalytic performance,as well as the low utilization of Au nanoparticles(lower than50%).
With the two issues,sample with Au loading of0.33wt.%was prepared on the carrier of CeO2by deposition precipitation.Demonstrated by ICP-AES,XRD and HRTEM techniques,Au/CeO2sample with Au entities under nanoscale was prepared, and metal dispersion or utilization of100%would achieve on this sample.Au/CeO2 sample was endured different redox treatments(oxidative measuring fully-reduced sample at300℃in air-flow by controlling oxidation period)to obtain a ries of Au/CeO2catalysts,which were characterized by H2-TPR measurements and tested by employing CO oxidation as indicator reaction in this work.Around20times of hydrogen-consumptions compared to the calculated consumption(by assuming all loaded Au as Au III species to consume H2)but with the peak shifts in a low temperature range of102-150℃on the catalysts were illuminated by H2-TPR measurements,disclosing the outstanding redox feature on the interface of such Au/CeO2catalysts.The redox state of such Au/oxide interfaces and corresponding activity were able to be simultaneously tuned by modulating the oxidation period. The catalyst obtained from30min oxidative measurement showed the lowest hydrogen consumption peak temperature,disclosing the
most outstanding redox feature.Accordingly,various catalysts showed different catalytic performance for CO oxidation reaction,and catalysis performance of the catalyst obtained from30min oxidative measurement was optimal,which TOF at30℃for CO oxidation by up to 10times compared to the state-of-art Au/CeO2catalyst(carrying of ca.3.0nm Au particles).In addition,the declined activity of the typical catalyst after a30h continuous reaction was able to be recovered by tuning back of its redox state,further
III
Abstract
indicated that the metal-oxide interfacial redox property could function as dominating factor and be tuned for improving catalytic performance of such supported sub-nanoscale metal entities.Au/TiO2and the Au/ZrO2catalysts were prepared with the same method,which particle size was3nm or5nm,respectively,of which only Au/ZrO2occurred gold characteristics of the diffraction peak on the XRD spectra.Under the atmosphere of the same composition,flow velocity and reduction temperature60mg Au/TiO2catalyst could be fully reducted in240min.On this basis, sample under oxidation of40min showed the best catalytic activity and the lowest reaction temperature CO complet
ely oxidation was80℃.And with the Au/ZrO2 oxidation time extended,the catalytic activity showed a linear downward trend.In stability tests，the catalyst activity of both catalysts declined gently.Of cour,the declined activity of the typical catalyst after a30h continuous reaction ware able to be recovered.The results further indicate that,for oxide supported Au catalysts,the regulation of their redox state is a facile means to improve their catalytic performance. Besides,as for the frequently ud nano-Au catalysts,to limit the scale of Au catalysts into sub-nanometer and to obtain a metal/oxide interface with highly disperd Au would be crucial to improve and tune the performance of Au catalyst.
Key Words:Heterogeneous catalysis；Precious metal dispersion；Au;Au-oxide interface
IV
目录
目录
第1章绪论 (1)
1.1金催化剂概述 (1)
1.2负载型金催化剂的应用 (2)
守岁的意义>专能干细胞
1.2.1醇醛的选择性氧化 (2)
1.2.1烯炔环氧化 (3)
1.2.1胺选择性氧化 (3)
1.3影响负载型金催化剂催化活性的因素 (4)
1.3.1金的尺寸效应 (4)
1.3.2载体效应 (7)
关于劳动的优美句子1.3.3制备方法的影响 (9)
1.4Au催化CO低温氧化机理 (10)
1.5本论文的研究思路及研究内容 (14)
第2章实验部分 (15)
退机票手续费2.1主要实验药品、仪器 (15)
2.2催化剂的合成 (16)志愿者服务精神
2.3催化剂评价条件 (16)
2.3.1催化剂活性评价 (16)
2.3.2催化剂稳定性评价 (17)
2.4催化剂的表征 (18)
2.4.1电感耦合等离子体发射光谱分析(ICP-AES） (18)
2.4.2粉末X-射线衍射(XRD) (18)
2.4.3比表面测定（N2-BET） (18)
2.4.4透射电子显微镜（TEM和HRTEM） (18)
2.4.5紫外可见吸收光谱（UV-Vis） (18)
2.4.6程序升温还原(H2-TPR) (19)
第3章Au/CeO2催化CO低温氧化的研究 (20)
V
目录
3.1催化剂制备 (21)
3.1.1载体的制备 (21)
3.1.2金催化剂的制备 (21)
3.1.3活性对比和方法选定 (22)
3.2Au/CeO2催化剂的表征及活性测试 (25)
3.2.1Au/CeO2的H2-TPR表征 (25)
3.2.2Au/CeO2的N2-BET及XRD表征 (28)
3.2.3Au/CeO2的TEM表征 (29)
3.2.4Au/CeO2催化CO低温氧化的活性 (31)
3.3Au/CeO2的稳定性测试 (33)
3.4Au/CeO2的恢复活性测试 (34)
3.5本章小结 (36)
第4章TiO2和ZrO2负载金催化剂的催化性能研究 (37)
4.1TiO2负载金催化CO低温氧化反应 (37)
4.1.1Au/TiO2催化剂的制备 (37)
4.1.2Au/TiO2催化剂的表征 (37)大葱烧海参的做法
4.1.3Au/TiO2催化剂的活性测试 (39)
4.1.4Au/TiO2催化剂的稳定性测试 (41)
4.1.5Au/TiO2催化剂的恢复活性测试 (41)
4.2ZrO2负载金催化CO低温氧化反应 (42)
4.2.1Au/ZrO2催化剂的制备 (42)
4.2.2Au/ZrO2催化剂的表征 (43)
4.2.3Au/ZrO2催化剂的活性测试 (45)
4.2.4Au/ZrO2的稳定性及恢复活性测试 (46)
4.3本章小结 (47)
第5章结论 (48)
致谢 (49)
参考文献 (50)
攻读学位期间的研究成果 (58)
VI
