Investigation of SO₂ Resistance on Novel Cr_0.8Zr_0.2O_x Catalysts for Marine Low-Temperature SCR of NO Removal

Novel Cr0.8Zr0.2Ox catalysts were synthesized by the co-precipitation method for selective catalytic reduction (SCR) of NOx removal with NH3 (NH3-SCR) and reacted under different conditions. Experimental results indicated that the combination of Cr and Zr oxides exhibited excellent performance of SO2 resistance. It was verified that the solid solution structure was formed in the Cr0.8Zr0.2Ox catalyst. The fresh Cr0.8Zr0.2Ox-F possessed an excellent SO2 resistance, and maintained around ∼94% NO removal efficiency with 100 ppm SO2 at 230 °C, which would be beneficial to marine applications. Fresh Cr0.8Zr0.2Ox catalysts followed both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms. In addition, there was almost no effect on the adsorption of NH3 but an adverse effect on the adsorption of NOx species after the addition of SO2. Thus, the E–R mechanism played a crucial role, with gaseous NOx acting as intermediate species when SO2 existed. The major impact reason of SO2 tolerance of the Cr0.8Zr0.2Ox catalyst was the increase of Oa and reacted Cr6+.