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

Abstract

Mn3O4@SiO2 prepared via a Stober route showed a steady reaction rate for CO oxidation at 250 °C after 12 h. The reaction orders, with respect to CO (0.49–0.12) and O2 (0.4–0.6), were obtained for a Mn3O4@SiO2 catalyst (dMn3O4 = 7.6 nm) in the temperature range of 220–280 °C. Via Operando Raman spectroscopy, a COad-induced change in the symmetric stretch of Mn–O–Mn (from 636 cm–1 to 642 cm–1) 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 Langmuir–Hinshelwood mechanism at or below 280 °C. In comparison with the reference α-Mn2O3 catalyst, the presence of shell SiO2 does not change the reaction behavior but improves the catalyst stability.