The effects of BiO on the selective catalytic reduction of NO by propylene over CoO nanoplates.

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