摘要
利用TPD(或TP)-IR动态方法,详细研究了由Rh_4(CO)_(12)衍生的Rh_4/Al_2O_3上金属分散度、CO覆盖和表面碳对CO吸附类型的影响。结果表明,影响CO在Rh_4/Al_2O_3上的吸附类型的主要因素是Rh的分散度,而分散度可以通过适当的制备方法加以控制。CO覆盖度只影响孪生CO谱带的强度;但同时影响线式和桥式CO谱带的位置和强度。在260℃以上,CO解离所产生的表面碳可以完全覆盖Rh^I中心,导致孪生CO谱带消失;对丁线式和桥式中心,只是部分被表面碳覆盖,导致线式样和桥式CO谱带位移到低频。
Effects of dispersion of Rh, CO coverage and surface carbon on the adsorption types of CO over Rh4/Al2O3 derived from Rh4(CO)12 have been investigated in detail by using TPD (or TP)-IR dynamic method. It is found that the type of chemisorbed CO on Rh4/Al2O3 is influenced mainly by Rh dispersion,and the dispersion of Rh can be controlled by appropriate preparation method. The CO coverage affects only the intensities of twin CO bands, while the intensities and locations of linear and bridged CO bands are influenced by CO coverage. Above 260℃, Rh1 sites are easily covered fully by surface carbon, it leads to the disappearance of twin CO bands, while the linear and bridged sites are covered partially by surface carbon, and it leads to the shift of linear and bridged CO bands to low frequency.
基金
国家催化基础研究实验室基金
国家自然科学基金
