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以3种层板组成的层状双羟基金属氢氧化物(layered double hydroxides,LDHs)为载体,制备了负载型金催化剂样品(Au/MgAl-LDHs,Au/ZnAl-LDHs和Au/MgFe-LDHs),借助X射线衍射、透射电子显微镜和光电子能谱,表征了金催化剂样品的物性,研究了催化剂样品在CO常温催化氧化反应中的活性及稳定性。结果显示,LDHs载体表面的金以金属态存在,其粒径1~5 nm,在常温下,金催化剂对CO的转化率达100%。另外,金催化剂在使用过程中失活的主要原因是载体晶体结构不稳定:晶体结构的坍塌使载体表面的纳米金颗粒被覆盖,导致表面金含量降低而失活。此外,LDHs的层状结构坍塌也削弱了载体与纳米金颗粒之间的相互作用,使得纳米金颗粒因迁移、聚集、长大而失活。催化剂的稳定性顺序由大到小依次为Au/MgAl-LDHs,Au/ZnAl-LDHs和Au/MgFe-LDHs,稳定性的差异与LDHs层板的电荷密度有关,电荷密度最大的MgAl-LDHs负载的金催化剂稳定性最高,连续使用69 h后,CO的常温转化率仍能保持100%。
Supported gold catalyst samples (Au / MgAl-LDHs, Au / ZnAl-LDHs and Au / MgFe-LDHs) were prepared from layered double hydroxides (LDHs) ). The properties of the gold catalyst samples were characterized by X-ray diffraction, transmission electron microscopy and photoelectron spectroscopy. The catalytic activity and stability of the catalyst samples in the catalytic oxidation of CO at normal temperature were studied. The results showed that gold on the surface of LDHs carrier was present in the metallic state with particle size of 1 ~ 5 nm. The conversion rate of gold catalyst to CO was 100% at room temperature. In addition, the gold catalyst inactivation during the use of the main reason is the carrier crystal structure is unstable: the collapse of the crystal structure of the carrier surface of gold nanoparticles are covered, resulting in reduced surface gold content and inactivation. In addition, the collapse of the layered structure of LDHs also weakens the interaction between the support and the AuNPs, rendering the AuNPs inactivated by migration, aggregation and growth. The order of stability of the catalysts is Au / MgAl-LDHs, Au / ZnAl-LDHs and Au / MgFe-LDHs in descending order of their stability. The difference in stability is related to the charge density of LDHs laminates. The stability of the gold catalyst is the highest. After 69 hours of continuous use, the CO conversion at room temperature can still maintain 100%.