Enhanced La0.875Ce0.125CoO3 catalyst for Hg0 removal from low-temperature flue gas: H2O and SO2 resistance performance and mechanism

Abstract

The catalysts utilized for low-temperature catalytic oxidation of Hg⁰ from flue gas typically suffer from issues related to H₂O and SO₂ poisoning. This study focused on doping modification of La_0.875Ce_0.125CoO₃ perovskite with promoters and conducted a thorough investigation on the H₂O and SO₂ resistance through characterization and DFT methods. Experimental results demonstrated that the LCeCO/30 wt% ZrO₂ possessed optimal H₂O and SO₂ resistance. Under high sulfur (1500 ppm SO₂) and high humidity (10 % H₂O(g)) conditions, it maintained approximately 91 % Hg⁰ removal efficiency after thermal regeneration cycles. Characterization results indicated that ZrO₂ doping facilitated the formation of three-dimensional macroporous structure and protected active Co³⁺ sites on the surface. Based on DFT calculations, the H₂O poisoning is attributed to competitive adsorption between H₂O(g) and Hg⁰ on the active sites. Also, the SO₂ poisoning occurs due to competitive adsorption of SO₂ and the toxicity of sulfates to the surface active sites. Meanwhile, ZrO₂ doping can lower the adsorption energies of H₂O(g) and SO₂ by modifying their adsorption configuration, thus weakening the competitive adsorption of H₂O(g) and SO₂ with Hg⁰. Overall, LCeCO/ZrO₂ is a promising Hg⁰ removal catalyst with superior H₂O and SO₂ resistance.