RgCo双金属催化剂的研究IV. Rh2Co2/Al2O3上的吸附中心类型及吸附性能

利用CO和NO作为双探针分子对Rh2Co2/Al2O3的吸附中心类型和吸附性能进行了详细的研究。结果表明Rh2Co2/Al2O3上存在Rh上的孪生和桥式CO吸附中心以及Co上的线式CO吸附中心。其中Rh上的孪生和桥式CO吸附中心对CO和NO的吸附性能与Rh4/Al2O3上的孪生和桥式CO中心相似。Co上的线式CO吸附中心以预吸附的CO能被NO取代, 预吸附的NO不能被CO取代而区别于Rh4/Al2O3上的Rh的线式CO吸附中心; 又以既能吸附CO又能吸附NO而不同于Co2/Al2O3和Rh+Co/Al2O3上的Co中心。与母体簇的结构相关联, 表明H2还原后的Rh2Co2/Al2O3上Rh2Co2(CO)12簇结构仍保持, 且Rh-Co相互作用强。

Study of RhCo bimetal catalysts IV. Forms and properties of adsorption sites on Rh2Co2/Al2O3

The forms and properties of adsorption sites on Rh2Co2/Al2O3 have been studied in detail by using CO and NO as double probes. The results indicate that there are Rh^I sites and bridged sites on Rh and linear sites on Co over Rh4/Al2O3. The chemisorption properties of Rh^I sites and briged sites on Rh over Rh2Co2/Al2O3 for CO and NO are similar to that over Rh4Al2O3. While the chemisorption propertties of the linear sites on Co over Rh2Co2/Al2O3 on which preadsorbed CO can be replaced by NO and preadsorbed NO can not be replaced by CO are different from that of linear sites on Rh4/Al2O3 and that of Co sites on Co2/Al2O3 and Rh+Co/Al2O3. To relate above results with the structure of original Rh2Co2(CO)12, it indicate that Rh2Co2(CO)12 impregnated on Al2O3 retain its structure after reduction with H2 at 400℃. The interaction between Rh and Co is strong.