Ce-MnO_x composite oxide catalysts with different proportions were prepared using the coprecipitation method, and the CO-removal ability of the catalysts with the tested temperature range of 60–140 °C was investigated systematically. The effect of Ce and Mn ratios on the catalytic oxidation performance of CO was investigated using X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), H₂ temperature programmed reduction (H₂-TPR), CO-temperature programmed desorption (CO-TPD), and in situ infrared spectra. The experimental results reveal that under the same test conditions, the CO conversion rate of pure Mn₃O₄ reaches 95.4% at 170 °C. Additionally, at 140 °C, the Ce-MnO_x series composite oxide catalyst converts CO at a rate of over 96%, outperforming single-phase Mn₃O₄ in terms of catalytic performance. With the decrement in Ce content, the performance of Ce-MnO_x series composite oxide catalysts first increase and then decrease. The Ce MnO_x catalyst behaves best when Ce:Mn = 1:1, with a CO conversion rate of 99.96% at 140 °C and 91.98% at 100 °C.

In this experiment, NiCo₂O_x catalysts, with different elements added (Mg, Fe, Cu, and Ce), were prepared using the co-precipitation method to investigate their catalytic performance for carbon monoxide, as well as their water resistance and sulfur resistance. Combined with the sintering flue gas environment of Baosteel Zhanjiang Iron and Steel Co., Ltd., it provides a reference for the catalytic oxidation of CO in complex environments. The results reveal that the Fe-added catalysts exhibited a better CO catalytic performance and possessed good redox properties, and the Fe metal ion-added NiCo₂O_x catalysts showed a CO catalytic efficiency of 91.72% at 100 °C. Meanwhile, the Fe-added catalysts had the strongest resistance to water, with a conversion of 98.37% to CO at 140 °C, and with 10% water vapor. The Ce-added catalyst showed a better SO₂ resistance and hybrid resistance of SO₂ and H₂O. Under the condition of sulfur addition, the CO conversion of the Ce-added catalyst was as high as 63.07% after 4 h of SO₂ introduction, and the efficiency could be restored to 100% after cutting off the supply of SO₂. Under the conditions of sulfur addition and water addition, the CO conversion of the catalyst was 98.23% after cutting off the SO₂.