Suppressing coke accumulation via dynamic oxygen regeneration in chlorobenzene oxidation over K-Mn-Al

Abstract

In this study, The K-Mn-Al and K-Al catalysts were prepared by a coprecipitation method and applied to the catalytic oxidation of chlorobenzene (CB). The results showed that K-Mn-Al exhibited better catalytic performance, higher CO 2 selectivity, excellent cyclic stability, and superior water resistance. K-Mn-Al formed a mixed-valence MnO x structure dominated by Mn 2 O 3 , together with a larger specific surface area and a well-developed mesoporous structure. K-Mn-Al exhibited a high Mn 3+ /Mn 4+ ratio (4.02), abundant active lattice oxygen, superior redox properties and moderate surface acidity which established a self-sustaining oxidation cycle that enabled continuous deep oxidation of CB along the pathway: CB → phenol/monochlorophenol → benzoquinone → maleic acid/carboxylic acids → carbonate → CO 2 . The stable Mn 3+ /Mn 4+ dynamic cycle ensured continuous lattice oxygen regeneration and effective intermediate conversion, thereby preventing carbon accumulation. In contrast, for K-Al the irreversible structural transformation and disrupted oxygen cycling during prolonged reaction resulted in progressive Mn 4+ depletion, insufficient deep oxidation of intermediates and severe carbon accumulation, ultimately leading to the deactivation cycle that accounted for the poor long-term stability.