Engineering Co3O4@3DOM LaCoO3 multistage-pore nanoreactor with superior SO2 resistance for toluene catalytic combustion

Abstract

Sulfur dioxide poisoning is a significant factor in catalyst deactivation during the catalytic combustion of volatile organic compounds. In this study, we prepared the LaCoO₃ and Co₃O₄ composite catalysts using both the Ship-in-Bottle and Building-Bottle-Around-Ship approaches. Three-dimensionally ordered macropores (3DOM LaCoO₃) were utilized as nanoreactors to protect the active sites during the catalytic combustion of toluene, preventing SO₂ poisoning. Additionally, we grew ZIF-67 confined in the nanoreactor to create a multistage-pore structure. The Co₃O₄@3DOM LaCoO₃ catalysts exhibited excellent activity in the complete catalytic oxidation of toluene. Various characterization studies confirmed the presence of a significant number of Co³⁺ species and an abundance of surface weak acid sites in the Co₃O₄@3DOM LaCoO₃ catalysts, which synergistically enhanced the conversion of VOCs at low temperatures. Notably, the multistage pore structure provided a favorable reaction environment, accelerating the adsorption and diffusion of toluene and intermediates, resulting in excellent sulfur resistance of the catalysts. Moreover, XPS analysis confirmed a strong interaction between Co₃O₄ and LaCoO₃, promoting rapid electron transfer and increasing the activation of O²⁻. In situ DRIFTS experiments verified that toluene mainly follows the MvK mechanism over Co₃O₄@3DOM LaCoO₃ catalysts, indicating the following reaction pathway: toluene adsorption → benzyl alcohol → benzaldehyde → benzoate → anhydride → CO₂ and H₂O.