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Self-sustained catalytic combustion is a promising strategy to remove CO from the off-gas produced during steelmaking, where the potential catalysts are bulk copper-cerium-zirconium mixed oxides or those supported on TiO 2 or ZSM-5 substrates. In this study, the effects of the catalyst support on the CO catalytic ignition performance and reaction pathways were investigated by FTIR coupled with a novel in-situ cell, together with the state-of-the-art characterization techniques. The Infrared (IR) transmission cell equipped with a magnetically driven system, could effectively prevent overlaps between active intermediate peaks (Cu+-CO and Cu+(CO) 2) and gaseous CO peaks. The Cu+ cations located at the phase interface are the main active sites. The Cu and Ce interactions lead to the formation of solid solutions of CuCe 0.75 Zr 0.25 O δ (CuCeZr). The monocarbonyls [Cu+-CO] are the dominant species during CO oxidation, and the vacancies in the solid solutions are occupied by oxygen, accelerating the oxygen cycle. The TiO 2 or ZSM-5 supports promote copper dispersion over CuCe 0.75 Zr 0.25 O δ /TiO 2 (CuCeZr/T) and CuCe 0.75 Zr 0.25 O δ /ZSM-5 (CuCeZr/Z) catalysts, which can be attributed to their high surface areas (168.2 and 346.3 m2/g, respectively), while the Cu-Ce interactions are less relevant. Hence, CO oxidation mainly occurs at the phase interface between copper oxide and TiO 2 /ZSM-5. Dicarbonyls [Cu+(CO) 2 ] are the main intermediates for the CuCeZr/T and CuCeZr/Z catalysts, and the Cu2+ species are reduced to form dicarbonyls that also take part in the oxidation process. Although a well copper dispersion enhances the activity of individual copper sites on the CuCeZr/T and CuCeZr/Z catalysts, considering the redshift of the carbonyl bands and the increase in CO adsorption, the close interactions and high contents of Cu and Ce favor the local accumulation of heat and mass transfer over bulk CuCeZr, leading to the ignition of CO at low temperatures. [Display omitted] • CuCe 0.75 Zr 0.25 O δ and CuCe 0.75 Zr 0.25 O δ /TiO 2 and CuCe 0.75 Zr 0.25 O δ /ZSM-5 catalysts were designed. • The structure-activity relationship was obtained. • The self-sustained combustion and stability limit of CO were carried out. • The in-situ IR with a novel magnetically driven IR cell was designed and performed. • The intermediate species and reaction pathways over different catalysts were evidenced. [ABSTRACT FROM AUTHOR]

The CuMn/ZSM-5 (CM/Z), CuMn/Beta (CM/B), and CuMn/SSZ-13 (CM/S) catalyst samples were prepared via an excess impregnation method to investigate the metal-support effect. The results show that the activity at 550 °C for NO direct decomposition follows the order of CM/Z (53.4%) > CM/B (49.2%) > CM/S (7.9%). The good activity and stability of CM/Z are attributed to a strong support effect including forming more active copper sites of the (Cu2+-O2--Cu2+)2+ and (Cu+-□-Cu+)2+ dimers, which have higher redox activity, capacity of oxygen mobility, and NO sorption capability. The competitive adsorption between NO and O 2 on the oxygen vacancy of dimers over CM/Z results in the activity decrease from 53.4% to 40.3% at 550 °C after adding 1 vol% O 2. The reaction mechanism over CM/Z was discussed based on the in situ DRIFT and isotopic (18O 2) experiments. Two NO adsorbs firstly on (Cu+-□-Cu+)2+ to form N 2 O, and N 2 O is activated to produce N 2 , followed by the NO adsorption on (Cu2+-O2--Cu2+)2+ to form nitrite and nitrate species and decomposition to NO and O 2. [Display omitted] ● The support effect of ZSM-5, Beta, and SSZ-13 supported CuMn is examined. ● CuMn/ZSM-5 exhibits a high NO to N 2 conversion of 53.4% at 550 °C. ● The intermediate species and competitive adsorption of NO and O 2 are discussed. ● The reaction pathways for NO direct decomposition are proposed. [ABSTRACT FROM AUTHOR]