Mn3O4-Au/3DOM La0.6Sr0.4CoO3: High-performance catalysts for toluene oxidation

Abstract

Three-dimensionally ordered macroporous La0.6Sr0.4CoO3 (3DOM LSCO) and its supported gold and manganese oxide (yMn3O4-zAu/3DOM LSCO; y=0.75–2.50wt%, z=ca. 2.0wt%) nanoparticles (NPs) were prepared using the polymethyl methacrylate-templating, polyvinyl alcohol-protected reduction, and physical adsorption methods, respectively. Physicochemical properties of the samples were characterized by means of numerous techniques, and their catalytic activities were evaluated for the oxidation of toluene. It is shown that the 3DOM LSCO in yMn3O4-zAu/3DOM LSCO with a surface area of 20–24m2/g displayed a rhombohedral crystal structure, and Mn3O4 (size: 5–12nm) and Au (size: 3–4nm) NPs were highly dispersed on the surface of 3DOM LSCO. There were good correlations of adsorbed oxygen species concentration and low-temperature reducibility with catalytic activity of the sample. The 1.67Mn3O4-2Au/3DOM LSCO sample performed the best, giving the T50% and T90% (temperatures required for achieving toluene conversions of 50 and 90%) of 214 and 230°C at a space velocity of 20,000mL/(gh), respectively. The introduction of water vapor to the reaction system caused a partial deactivation of the 1.67Mn3O4-2Au/3DOM LSCO sample, and such a deactivation was reversible. The apparent activation energies (41.7–47.4kJ/mol) obtained over yMn3O4-2Au/3DOM LSCO were lower than those (49.2–56.8kJ/mol) obtained over 3DOM LSCO, 2Au/3DOM LSCO, and 1.56Mn3O4-2Au/Bulk LSCO. It is concluded that the large surface area, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Au or Mn3O4 NPs and 3DOM LSCO were responsible for the good catalytic performance of 1.67Mn3O4-2Au/3DOM LSCO.