Effect of Pr/Zr atomic ratio on the activity of catalytic oxidation denitration of Pr_xZr_1−xO_2–δ

The Pr_xZr_1−xO_2–δ catalyst with different atom ratio of Pr/Zr was prepared by the sol-gel to catalytic oxidation denitration. Results showed that the efficiency of catalytic oxidation denitration increased initially and decreased afterward with the ratio of Pr atom increased. And the optimum denitration activity could achieve 94.62% at 250 °C when the atom ratio of Pr/Zr was 5∶5. The catalysts were characterized by SEM, N₂ adsorption-desorption, XRD, XPS, H₂-TPR, and FT-IR. The results illustrated that the catalyst (Pr_0.5Zr_0.5O_2−δ) with the best activity has a “layered” morphology, many pores on the surface, and it has a large specific surface area and pore volume of 77.74 m²/g and 0.66 cm³/g, respectively. Furthermore, the crystalline phase transforms from c-ZrO₂ to Pr₂Zr₂O₇ with the increasing of Pr atom. XPS and H₂-TPR results showed that the surface chemosorption oxygen and surface Pr^{4 +} oxides increased, and the rising of Pr atom ratio was beneficial to produce oxygen vacancy (Vӧ) site which advantageous to improve the efficiency of catalytic oxidation denitration. FT-IR characterization results indicated that Pr_0.5Zr_0.5O_2−δ solid solution had better NO selectivity, which was conducive to the catalytic oxidation of NO. The anti-SO₂ and H₂O toxicity experiments showed that Pr/Zr atomic ratio at 5∶5 had better anti-toxicity than other ratios. In addition, using IC to analysis absorption products, the result showed that \rmNO^-_2 and \rmNO^-_3 were the main products in the absorption solution.