载体对Rh基催化剂上甲烷解离活性的影响

采用脉冲反应技术、原位CO吸附和吡啶吸附红外光谱,考察了Al2O3和SiO2负载的Rh基催化剂上Rh-CeO2相互作用和CH4解离活性.结果表明,载体酸性对Rh-CeO2相互作用有显著影响.Rh/Al2O3催化剂中添加CeO2增加了载体Al2O3的Lewis酸位,使Al2O3接受电子的能力增强,从而降低Rh的电子密度,有利于CH4解离活化.相反,Rh/SiO2催化剂中添加CeO2减少了载体SiO2的Lewis酸位和酸强度,使SiO2难于接受电子,导致Rh的电子密度增加,不利于CH4解离活化.

The Effect of Supports on the Activity of Methane Dissociation over Rh Catalysts

The Rh-CeO2 interaction and the activity of CH4 dissociation were investigated on Al2O3-and SiO2-supported Rh catalysts by using the pulse reaction technique,infrared spectroscopy of CO adsorbed,and infrared spectroscopy of pyridine adsorbed.The Rh-CeO2 interaction was strongly influenced by the acidity of support.Addition of CeO2 to Rh/Al2O3 increased the number of Lewis acid sites on Al2O3,which in turn enhanced the ability of Al2O3 to accept electrons.This decreased the electron density of Rh and consequently facilitated the activation and dissociation of CH4 on Rh.On the contrary,the addition of CeO2 to Rh/SiO2 decreased both the number and the strength of Lewis acid sites on SiO2,which weakened the electron-accepting ability of SiO2.As a result,it brought out an increase in the electron density of Rh and inhibited CH4 dissociation on Rh.