The CO adsorption on a Fe 2O 3–Ce 0.5Zr 0.5O 2 catalyst studied by TPD, isotope exchange and FTIR spectroscopy

Abstract

The interaction of carbon monoxide with Fe 2O 3–Ce 0.5Zr 0.5O 2 was investigated by the adsorption investigation under isothermal CO/H 2 exposure and temperature-programmed desorption (TPD), as well as by in-situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), in order to understand the carbon monoxide formation during the cyclic water gas shift reaction. When the Fe 2O 3–Ce 0.5Zr 0.5O 2 catalyst was exposed to a mixture of CO and H 2, the majority of the surface species depicted by the DRIFT analysis were associated with carbonates. The carbonates were essentially stable in a He atmosphere at temperatures ranging from 60 to 450 °C. An increase in the temperature leads to the conversion of the carbonates, where the oxygen comes from the catalyst lattice. Investigations carried out using a H 2O/He mixture showed that carbon oxides were produced during the interconversion of carbonate species on the catalyst surface with steam. The main gas component produced during the TPD of an Fe 2O 3–Ce 0.5Zr 0.5O 2 catalyst in the temperature interval of 60–500 °C was carbon dioxide. The amount of carbon oxides produced decreased at elevated temperatures. The steady-state isotopic C 18O experiments revealed that the Boudouard reaction occurred at temperatures higher than 350 °C. The carbon deposits which were formed on the catalyst surface during the reduction step through the Boudouard reaction led to CO formation during the successive re-oxidation step.