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

利用XPS对以金属盐共浸渍制备的Rh+Co/Al2O3和Rh2Co2(CO)12为前体制备的Rh2Co2/Al2O3催化剂的金属-金属及金属-载体相互作用进行了详细研究。发现Rh+Co/Al2O3经400℃H2还原后, Rh的结合能与Rh^0的结合能接近, Co基本上以CoAl2O4状态存在, Co^0的谱峰很弱; 而Rh2Co2/Al2O3经400℃H2还原后, Rh的结合能与Rh^0接近, Co除以CoAl2O4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-Al2O3的相互作用弱, Co-Al2O3的相互作用强。Rh+Co/Al2O3上Rh-Co相互作用弱, 而Rh2Co2/Al2O3在H2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。

Study of RhCo bimetal catalysts I. Metal-metal and metal-support interactions on RhCo bimetal catalysts

Metal-metal and metal-support interaction on Rh+Co/Al2O3 prepared by co-impregnation and Rh2Co2/Al2O3 by using RhCo carbonyl cluster as the precusor have been studied in detail by X-ray Photoelectron Spectroscopy (XPS). It was found that binding energy for Rh 3d on Rh+Co/Al2O3 reduced with H2 at 400℃ is nearly identical with that of Rh^0, and Co exists essentially in CoAl2O4 state and only the very small amount of Co exists as Co^0. On Rh2CO2/Al2O3 reduced with H2 at 400℃ Rh exists as Rh^0, and a part of Co exists in CoAl2O4 state whereas another part of Co exists as Co^0. Results above indicate that Rh-Al2O3 interaction for Rh+Co/Al2O3 and Rh2Co2/Al2O3 is weak, and Co- Al2O3 interaction is strong; Rh-Co interaction on Rh+Co/Al2O3 prepared by coimpregnation of RhCl3 and Co(NO3)2 is weak, but on Rh2CO2/Al2O3 prepared by using RhCo carbonyl cluster as the precusor the strong Rh- Co interaction of RhCo carbonyl cluster is still maintained resulting in the considerable amount of Co^0.