Modulating NH oxidation and inhibiting sulfate deposition to improve NH-SCR denitration performance by controlling Mn/Nb ratio over MnNbTiO (a = 0.6-0.9) catalysts.

The MnNbTiO (a = 0.6-0.9) catalysts for NH selective catalytic reduction denitration were prepared using the co-precipitation method. Among them, MnNbTiO exhibits well low-temperature catalytic performance, wide activity temperature range (180-480 ℃), and worthy resistance to SO even with HO. XRD was used to investigate the structure of MnNbTiO, in which Mn and Nb oxides highly dispersed in the MnNbTiO catalysts and Nb can dope into the crystal lattice of TiO. XRF and XPS results show Nb can affect the transfer of electrons to Mn, and changing the Mn/Nb ratio can regulate the Mn content on the MnNbTiO catalysts. H-TPR, NH and NO oxidation results verify that Nb inhibits the oxidation capacity of MnNbTiO, and altering the Mn/Nb ratio can get appropriate oxidation property, which facilitates low-temperature NH activation and limit non-selective oxidation for NH. In-situ DRIFTS results show Nb-OH bonds can provide new Brønsted acid sites, and both Lewis and Brønsted acid sites are active. Furthermore, Nb addition prevents sulphate deposition on the catalyst. The effect of Mn/Nb on catalytic performance, NO formation and inhibition, SO poisoning, SO effect on NH-SCR, and the enhancement of SO tolerance are also analyzed.