Effect of Cr doping in promoting the catalytic oxidation of dichloromethane (CH2Cl2) over Cr-Co@Z catalysts

Highlights: • Core-shell Cr-Co@Z catalysts are synthesized by microwave hydrothermal method. • Cr-Co@Z exhibits high performance and durability in CH₂Cl₂ catalytic oxidation. • HCl/Cl₂ removal from the catalyst surface are promoted in Cr-Co@Z. • A synergistic effect exists between Cr₂O₃ and Co₃O₄. • The degradation pathways of dichloromethane on Cr-Co@Z are clarified. A core–shell catalyst which consists of a Co₃O₄ core and ZSM-5 shell, was prepared by microwave hydrothermal method and subjected for dichloromethane (DCM) oxidation. Chromium, cerium, niobium, and manganese species were separately introduced into the core-shell catalyst using the wet precipitation method and denoted as M-Co@Z (M = Cr, Ce, Nb, Mn). The catalytic activity of the Cr-Co@Z catalyst was significantly increased due to the interaction between Cr₂O₃ and Co₃O₄. The results of Raman spectra indicated the incorporation of chromium into the Co₃O₄ lattice and revealed the existence of the interaction between Cr₂O₃ and Co₃O₄. The synergistic effect between Cr₂O₃ and Co₃O₄ might be conducive to the generation of highly defective structure and increase the ratio of Co³⁺/Co²⁺ of the sample, leading to its better oxygen mobility. The dechlorination ability of Cr-Co@Z was also promoted due to the enhanced mobility of lattice oxygen. Based on in situ DRIFT studies, a possible reaction route of CH₂Cl₂ oxidation over Cr-Co@Z catalyst was proposed.