LOW-TEMPERATURE OXIDATION OF CO OVER GOLD SUPPORTED ON TIO2, ALPHA-FE2O3, AND CO3O4
LOW-TEMPERATURE OXIDATION OF CO OVER GOLD SUPPORTED ON TIO2, ALPHA-FE2O3, AND CO3O4
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DOI：
10.1006/jcat.1993.1322
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发表时间：
1993-11-01
影响因子：
7.3
通讯作者：
DELMON, B
中科院分区：
文献类型：
--
作者：
HARUTA, M;TSUBOTA, S;DELMON, B
金可以通过共沉淀和沉积沉淀，然后在空气中煅烧高度分散在各种金属氧化物上。小的金颗粒是半球形的，并且通过外延接触、位错或与非晶氧化物层的接触而稳定。这种负载的金在催化性质上不同于未负载的金颗粒，并且对CO的低温氧化显示出高催化活性。特别地，负载在TiO 2、α-Fe 2 O 3、Co 3 O 4、NiO、Be（OH）2和Mg（OH）2上的金即使在0°C以下也非常活跃。在以TiO_2、α-Fe_2 O_3和Co_3 O_4为载体的金催化剂中，每个表面金原子的CO氧化转换频率几乎与所用载体氧化物的种类无关，并且随着金颗粒直径小于4 nm而急剧增加。小的金颗粒不仅为CO的可逆吸附提供了场所，而且还明显增加了氧在载体氧化物上的吸附量。在-10至65°C的温度范围内，CO氧化的活化能为8.2 kcal/mol（Au/TiO 2）、8.4 kcal/mol（Au/α-Fe 2 O 3）和3.9 kcal/mol（Au/Co 3 O 4）。三种催化剂的CO氧化速率均为零级，Au/TiO 2和Au/Co 3 O 4的CO氧化速率为0.2-0.3级，Au/α-Fe 2 O 3的CO氧化速率为零级。通过考虑TPD和FT-IR数据，提出了一种机制，其中CO吸附在金颗粒上迁移到周边的支持氧化物，并在那里它与吸附的氧反应，形成双齿碳酸盐物种。碳酸盐中间体的分解被认为是速率决定性的。
Gold can be highly dispersed on a variety of metal oxides by coprecipitation and deposition-precipitation followed by calcination in air. The small gold particles are hemispherical in shape and stabilized by epitaxial contact, dislocations, or contact with an amorphous oxide layer. Such supported gold differs in catalytic nature from unsupported gold particles and exhibits high catalytic activities for low-temperature oxidation of CO. Especially, gold supported on TiO2, α-Fe2O3, Co3O4, NiO, Be(OH)2, and Mg(OH)2is very active even at temperatures below 0°C. Among the gold catalysts supported on TiO2, α-Fe2O3, and Co3O4the turnover frequencies for CO oxidation per surface gold atom are almost independent of the kind of support oxides used and increase sharply with a decrease in diameter of gold particles below 4 nm. Small gold particles not only provide the sites for the reversible adsorption of CO but also appreciably increase the amount of oxygen adsorbed on the support oxides. In the temperature range −10 to 65°C, the activation energies for CO oxidation were 8.2 kcal/mol (Au/TiO2), 8.4 kcal/mol (Au/α-Fe2O3), and 3.9 kcal/mol (Au/Co3O4). The rate of CO oxidation is zero order with respect to CO for the three catalysts, and 0.2-0.3 for Au/TiO2and Au/Co3O4and zero order for Au/α-Fe2O3with respect to O2. By taking into consideration TPD and FT-IR data, a mechanism is proposed in which CO adsorbed on gold particles migrates toward the perimeter on support oxides and there it reacts with adsorbed oxygen to form bidentate carbonate species. The decomposition of the carbonate intermediate is considered to be rate-determining.