Simultaneous catalytic oxidation of NO and Hg0 over LaBO3 (B = Co, Mn, Ni, and Cu) perovskites

Perovskite catalysts have emerged as potential candidates for simultaneous catalytic oxidation of NO and Hg-0 present within the coal-derived flue gas. LaBO3 (B = Co, Mn, Ni, and Cu) perovskites were synthesized by sol-gel method. LaMnO3 and LaCoO3 exhibited better simultaneous oxidation activities among LaBO3 (B = Co, Mn, Ni, and Cu) perovskites (LaMnO3 > LaCoO3 > LaNiO3 > LaCuO3). The experimental results revealed that the simultaneous oxidation conversions of LaCoO3 and LaMnO 3 for NO and Hg-0 oxidation were all around 80% at 285 degrees C. The oxidation conversions of NO and Hg-0 by LaNiO 3 were less than 70%, and for LaCuO 3 , the NO conversion rate was up to 50%, while Hg-0 was less than 20%. The excellent simultaneous oxidation activities of LaBO3 (B = Co, Mn, Ni, and Cu) pemvskites originated from the B-site ion activities in the order of Mn 4+ > Co3+ > Ni2+ > Cu2+ . And surface area, O L /O A ratio and reducibility showed the following trends: LaMnO3 > LaCoO3> LaNiO3 > LaCuO3 . Furthermore, as typical LaMnO3 and LaCoO3 pemvskites, the Hg-0 would compete with NO for adsorption on the surface, resulting in a decrease in NO oxidation. However, the NO increased the Hg-0 conversion, which was related to NO2 oxidized from NO. The reaction mechanisms of LaMnO3 and LaCoO3 were obtained from the characterizations of XPS, NO-TPD, in situ DRIFTS and Hg-TPD. Hg-0 was oxidized to HgO, not Hg(NO3)(2). NO was converted into free nitrate species and gradually enriched on the pemvskite surface; consequently, it turned into NO2.

Automated summary

Perovskite catalysts LaBO3 (B = Co, Mn, Ni, and Cu) show promising simultaneous oxidation activity for NO and Hg-0 in coal-derived flue gas, with LaMnO3 and LaCoO3 exhibiting the best performance among the studied perovskites.