Lean oxidation of ternary CO/CH4/C3H8 over a Co-Fe spinel/ZSM-5 catalyst: interfacial redox synergy and operando DRIFTS insight

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Lean oxidation of CO and light hydrocarbons is important for controlling fuel-derived and combustion-related emissions, yet simultaneous oxidation remains challenging because pollutants with different reactivities compete for active sites and oxygen species. Herein, a Co-Fe spinel/ZSM-5 catalyst was developed for total oxidation of a ternary CO/CH 4 /C 3 H 8 feed under fuel-lean conditions. The Co-Fe oxide phase was synthesized onto ZSM-5 by wet impregnation to tailored a redox-active spinel/zeolite interface. Structural and surface analyses show that ZSM-5 preserves its MFI framework, improves Co-Fe oxide dispersion, retains high accessible surface area, and modulates the surface oxygen and Co/Fe redox environment. Compared with pristine ZSM-5 and unsupported Co-Fe oxide, Co-Fe/ZSM-5 exhibits superior mixed-feed oxidation activity, achieving complete CO conversion at ∼ 150 °C and high CH 4 /C 3 H 8 conversion near 400 °C, with stable CO 2 formation during short-term operation at 450 °C. Operando DRIFTS reveals temperature-dependent formation and consumption of formate- and carbonate-related intermediates, whose depletion coincides with increased CO 2 production. Together with XPS evidence for Co 2+ /Co 3+ and Fe 2+ /Fe 3+ redox couples and enriched lattice oxygen, these results support a Mars-van Krevelen-type oxidation pathway over the Co-Fe spinel/ZSM-5 interface. This work provides mechanistic insight into simultaneous CO, CH 4 , and C 3 H 8 oxidation and offers a strategy for designing non-noble-metal zeolite-supported catalysts for lean exhaust abatement.

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