Effects of the Incorporation of Distinct Cations in Titanate Nanotubes on the Catalytic Activity in NO x Conversion.

Effects of the incorporation of Cr, Ni, Co, Ag, Al, Ni and Pt cations in titanate nanotubes (NTs) were examined on the NO _x conversion. The structural and morphological characterizations evidenced that the ion-exchange reaction of Cr, Co, Ni and Al ions with the NTs produced catalysts with metals included in the interlayer regions of the trititanate NTs whereas an assembly of Ag and Pt nanoparticles were either on the nanotubes surface or inner diameters through an impregnation process. Understanding the role of the different metal cations intercalated or supported on the nanotubes, the optimal selective catalytic reduction of NO _x by CO reaction (SCR) conditions was investigated by carrying out variations in the reaction temperature, SO ₂ and H ₂ O poisoning and long-term stability runs. Pt nanoparticles on the NTs exhibited superior activity compared to the Cr, Co and Al intercalated in the nanotubes and even to the Ag and Ni counterparts. Resistance against SO ₂ poisoning was low on NiNT due to the trititanate phase transformation into TiO ₂ and also to sulfur deposits on Ni sites. However, the interaction between Pt ²⁺ from PtO _x and Ti ⁴⁺ in the NTs favored the adsorption of both NO _x and CO enhancing the catalytic performance.