RhCo双金属催化剂的研究 Ⅰ.RhCo双金属催化剂的金属-金属及金属-载体相互作用

Study of RhCo Bimetal Catalysts I. Metal-Metal and Metal-Support Interactions on RhCo Bimetal Catalysts

利用XPS对以金属盐共浸渍制备的PH+CO/AL_2O_3和RH_2Co_2(CO)_12为前体制备的Rh_2Co_2/Al_2O_3催化剂的金属-金属及金属-载体相互作用进行了详细的研究.发现Rh+Co/Al_2O_3经400℃ H_2还原后RH的结合能与Rh^0的结合能接近,Co基本上以CoAL_2O_4状态存在,Co_0的谱峰很弱;而Rh_2Co_2/Al_2O_3经400℃H_2还原后Rh的结合能与Rh^0接近,Co除以CoAl_2O_4状态存在外,还有相当一部分以Co^0状态存在.上述结果揭示出两个样品的RH-Al_2O_3的相互作用弱,Co-Al_2O_3的相互作用强.Rh+Co/Al_2O_3上Rh-Co相互作用弱,而Rh_2Co_2/Al_2O_3在H_2还原后仍保持RhCo簇合物的强的Rh-Co相互作用,导致显著量的Co^0存在.

The forms of adsorption sites, dynamic behavior of chemisorbed CO and CO disproportionate have been investigated by using CO and NO as double probes and TP - IR dynamic method. The results indicate that there are a large amount of adsorption sites for gem -dicarbonyl CO and a very small amount of adsorption sites for linear CO on Rh, and Co sites for adsorbed NO over Rh + Co/Al2O3. The bands of gem - dicarbonyl CO gradually decreased in intensity and fully desorbed at 300℃ during TPD(in vacuum) dynamic process. The temperature fully desorbed for gem - dicarbonyl CO on Rh + Co/Al2O3 is lower than that for gem - dicarbonyl CO on Rh4/Al2O3 indicating that addition of Co weaken CO adsorption strength on RhI sites over Rh + Co/Al2O3. The results obtained from TP (in CO) dynamic process indicate that CO disproportionation take place above 250℃ and the rate of CO disproportionation on RhI sites is higher than that on linear sites CO over Rh +Co/Al2O3.