Infrared spectroscopic study of CO and CO2 adsorption on Rh–ZrO2, Rh–Al2O3 and Rh–MgO

Abstract

The adsorption states of CO and CO₂ on Rh catalysts supported on ZrO₂, Al₂O₃ and MgO were studied using i.r. spectroscopy. Upon adsorption of CO on reduced Rh–ZrO₂, the carbonate bands due to the reaction 2CO →C + CO₂, together with the bands of twin, linear and bridge CO species were observed at moderate temperatures, whereas Rh–MgO gave no appreciable formation of CO₂ even at higher temperatures (> 100 °C) and Rh–Al₂O₃ showed intermediate behaviour. On the adsorption of CO₂, the linear CO band was formed at lower frequency than that on CO adsorption. The linear CO species formed from CO₂ showed higher reactivity toward hydrogen compared with that from CO adsorption.