Catalytic oxidation of dichloromethane over CrFeO mixed oxides: Improved activity and stability by sulfuric acid treatment.

A CrFeO mixed oxide with an FeCr 2 O 4 spinel structure was treated with sulfuric acid and tested for catalytic combustion of dichloromethane (DCM). The acid-treated catalysts (denoted as CrFeO-4S and CrFeO-9S) were more active than the pristine one, with the CrFeO-9S giving a 2-fold higher rate at 240 °C (35.7 versus 17.8 μmol m−2 h−1). More importantly, the acid treatment greatly enhanced the catalyst stability in long term reaction. Various characterizations revealed that the acid treatment improved the redox property and surface acidity of the CrFeO oxide, which accounted for the enhance activity. Meanwhile, the acid treatment removed weakly coordinated Cr species on the catalyst surface and thus avoided the Cr leakage during the reaction, which was responsible for the excellent stability. Moreover, kinetics and spectroscopic results revealed that the surface sulfate evolved a new reaction path to the formation of formaldehyde intermediate, which could be further oxidized to CO x. [Display omitted] • The CrFeO catalyst contained a FeCr 2 O 4 spinel structure. • The H 2 SO 4 treatment on the CrFeO removed part of Cr species in the catalyst. • The acid- treated catalysts were more active and stable for CH 2 Cl 2 oxidation. • The enhanced reducibility and surface acidity accounted for the improved performance. [ABSTRACT FROM AUTHOR]