The effects of Bi2O3 on the selective catalytic reduction of NO by propylene over Co3O4 nanoplates

Abstract

Bi₂O₃/Co₃O₄ catalysts prepared by the impregnation method were investigated for the selective catalytic reduction of NO by C₃H₆ (C₃H₆-SCR) in the presence of O₂. Their physicochemical properties were analyzed with SEM, XRD, H₂-TPR, XPS, PL and IR measurements. It was found that the deposition of Bi₂O₃ on Co₃O₄ nanoplates enhanced the catalytic activity, especially at low reaction temperature. The SO₂ tolerance of Co₃O₄ in C₃H₆-SCR activity was also improved with the addition of Bi₂O₃. Among all catalysts tested, 10.0 wt% Bi₂O₃/Co₃O₄ achieved a 90% NO conversion at 200 °C with the total flow rate of 200 mL min⁻¹ (GHSV 30 000 h⁻¹). No loss in its C₃H₆-SCR activity was observed at different temperatures after the addition of 100 ppm of SO₂ to the reaction mixture. These enhanced catalytic behaviors may be associated with the improved oxidizing characteristics of 10.0 wt% Bi₂O₃/Co₃O₂. XRD results showed that Bi₂O₃ entered the lattice of Co₃O₄, resulting in the formation of lattice distortion and structural defects. H₂-TPR results showed that the reduction of Co₃O₄ was promoted and the diffusion of oxygen was accelerated with the addition of Bi₂O₃. XPS measurements implied that more Co³⁺ formed on the 10.0% Bi₂O₃/Co₃O₂ catalysts. The improved oxidizing characteristics of the catalyst with the addition of Bi₂O₃ due to the synergistic effect of the nanostructure hybrid, thus enhanced the C₃H₆-SCR reaction and hindered the oxidization of SO₂. Therefore, the 10.0% Bi₂O₃/Co₃O₄ catalyst exhibited the highest NO conversion and strongest SO₂ tolerance ability.