Preparation, Characterization, and Kinetic Study of a Core-Shell Mn3O4@SiO2 Nanostructure Catalyst for CO Oxidation

Mn3O4@SiO2 prepared via a Stober route showed a steady reaction rate for CO oxidation at 250 degrees C after 12 h. The reaction orders, with respect to CO (0.490.12) and O2 (0.40.6), were obtained for a Mn3O4@SiO2 catalyst (dMn(3)O(4) = 7.6 nm) in the temperature range of 220-280 degrees C. Via Operando Raman spectroscopy, a COad-induced change in the symmetric stretch of MnOMn (from 636 cm1 to 642 cm1) was observed for Mn3O4@SiO2, indicating a tiny structure modification of core Mn3O4 by the adsorption of CO. With the combination of the catalyst structure and the kinetics of CO oxidation, we assume that this reaction proceeds mainly through the LangmuirHinshelwood mechanism at or below 280 degrees C. In comparison with the reference alpha-Mn2O3 catalyst, the presence of shell SiO2 does not change the reaction behavior but improves the catalyst stability.