Kinetics and Oxygen Vacancy Mechanism of the Oxidation of Carbon Monoxide on Perovskite Nd1-xSrxCoO3-y Solutions as a Catalyst

摘要

The oxidation of carbon monoxide by gaseous oxygen in the presence of a powdered Nd1-xSrxCoO3-y solid solution as a catalyst has been investigated in the temperature range from 150∩ to 300∩ under various CO and O2 partial pressures. The site of Sr substitution, nonstoichiometry, structure, and microstructure were studied by means of powder X-ray diffraction and infrared spectroscopy. The electrical conductivity of the solid solution has been measured at 300∩ under various CO and O2 partial pressures. The oxidation rates have been correlated with 1.5-and 1.2-order kinetics with and without a CO2 trap, respectively; first-and 0.7 order with respect to CO and 0.5-order to O2. For the above reaction temperature range, the activation energy is in the range from 0.25 to 0.35 eV/mol. From the infrared spectroscopic, conductivity and kinetic data, CO appears essentially to be adsorbed on the lattice oxygens of the catalyst, while O2 adsorbs as ions on the oxygen vacancies formed by Sr substitution. The oxygen vacancy mechanism of the CO oxidation and the main defect of Nd1-xSrxCoO3-y solid solution are supported and suggested from the agreement between IR data, conductivities, and kinetic data.