Preparation of nano-gold in zeolites for CO oxidation : Effects of structures and number of ion exchange sites of zeolites
Preparation of nano-gold in zeolites for CO oxidation : Effects of structures and number of ion exchange sites of zeolites
复制标题
DOI：
10.1016/j.apcata.2005.02.038
复制
发表时间：
2005-09
影响因子：
5.5
通讯作者：
Jen-Ho Chen;Jiunn-Nan Lin;Yih-Ming Kang;Wen-Yueh Yu;C. Kuo;B. Wan
中科院分区：
文献类型：
--
作者：
Jen-Ho Chen;Jiunn-Nan Lin;Yih-Ming Kang;Wen-Yueh Yu;C. Kuo;B. Wan
在pH调节的氯金酸溶液中，在不同类型的沸石(Y、β和丝光沸石)中制备了纳米金。考察了孔结构和铝含量对金的负载量和0℃下CO氧化反应活性的影响。每种沸石的载金量与铝含量密切相关，同时也受沸石结构的影响。HRTEM结果表明，铝负载量较少(1.8wt.%)的Y型分子筛在笼内形成了少量直径约为1 nm的金粒子，金物种在分子筛的外表面有聚集现象，而铝负载量较高(12.4wt.%)的Y型分子筛则形成了较多的1 nm左右的金粒子，没有观察到金粒子的聚集.氢气程序升温还原的结果表明，只有在较低的温度下，金物种才会在较小的孔(β和丝光沸石)中被还原。然而，在CO氧化过程中，金容易在β和丝光沸石的通道中烧结，导致活性严重降低。铝负载量为12.4wt.%的Y型分子筛的笼状孔阻碍了金的烧结，其亲水表面有利于金物种的活化，因此该催化剂对CO氧化具有较高的催化活性和稳定性。
Nano-gold was prepared in different types of zeolite (Y, β and mordenite) in pH-adjusted chloroauric acid solution. The effects of the pore structures and the aluminum content on the loading of gold and on the reaction activity for CO oxidation at 0°C were investigated. The gold loading in each zeolite was strongly related to the aluminum content; it was also affected by the structure of the zeolite. HRTEM results revealed that a few particles of gold around 1nm in diameter were formed in the cage of Y-type zeolite with less aluminum loading (1.8wt.%), and there was aggregation of gold species on the exterior surface of the zeolite; in contrast, more particles of gold around 1nm were formed in Y-type zeolite with more aluminum loading (12.4wt.%), no aggregation was observed. The results from the temperature-programmed reduction in hydrogen indicated that the gold species were reduced in the smaller pores (in β and mordenite) only at lower temperatures. Nevertheless, gold was easily sintered in the channels of β and mordenite during CO oxidation, causing severely reducing the activity. The cage-like pore in Y-type zeolite with 12.4wt.% aluminum loading prevented the sintering of gold, and its hydrophilic surface favored the activation of gold species; therefore, this Au/Y catalyst exhibited high catalytic activity and stability for CO oxidation.