Co-modified rod-like α-MnO2 with elevated activity, CO2 yield and stability for efficient oxidation of chlorobenzene

Abstract

The catalytic oxidation of chlorobenzene by α-MnO₂ has received much attention due to its excellent redox capacity. However, the differences in the catalytic activities of α-MnO₂ with different morphologies in chlorobenzene and how to improve their chlorine resistance have not been fully explored. In this paper, a variety of α-MnO₂ with different morphologies were prepared by hydrothermal and co-precipitation methods and examined for their catalytic performance in chlorobenzene oxidation, from which rod-like α-MnO₂ was selected as a matrix candidate and modified with different contents of Co to further enhance its catalytic performance. The loading of Co elevated the activity and CO₂ yield of α-MnO₂ and retarded its deactivation process in durability tests. In addition, the Co-modified α-MnO₂ nanorods exhibited better resistance to SO₂, NO, toluene, and H₂O at high temperatures, with versatile applicability to actual complex flue gas conditions. Characterization of the physicochemical properties showed that the introduction of Co increased the reduction capacity, the content and mobility of surface reactive oxygen species, and the acidity of α-MnO₂ (especially the medium-strong acidic sites), which synergistically contributed to the enhancement of the catalytic performance. It was concluded that the deactivation of the catalyst was associated with adsorption of Cl-containing species and coke deposition on its surface. Possible degradation pathways of CB on the prepared catalysts were explored through in situ DRIFTS technology. This paper presents the loading of Co on α-MnO₂ nanorods is a promising strategy for the design of cost-effective and high-performance Mn-based catalysts for the catalytic oxidation of CVOCs.