(60d) Controlled Synthesis of Novel Interweaved Titanium Oxide Nanotubes Confined Metal Oxide Catalytic Formulations: Effect of Morphology on Selective Catalytic Reduction (SCR) of NOx By NH3

The textural properties of various metal oxide confined titania nanotubes and their influence on surface activesites for NH₃−SCR were studied. Remarkably, the surface texture and tubular morphology of Me/TNT-H catalysts greatly promoted the NO_x conversions and temperature window compared to their nanoparticles. It can be ascribed to the preferentially located active species in the tubular framework. The impregnation of MnO_x over TNT-SA catalyst occur bare minimum because of the low specific surface area and low porevolume compared to other titania natotube supports, and this leads to poor deNO_x activity and narrow temperature window. Raman and X-ray diffraction patterns indicated that tubular structure in Mn/TNT samples significantly increases the concentration of oxygen vacancies and thus facilitate NO oxidation to NO₂. The relative atomic percentage value of Mn⁴⁺/Mn³⁺ characterized by deconvoluted XPS spectra was considerably high for the Mn(0.25)/TNT-H catalyst (Mn⁴⁺/Mn³⁺ = 2.15) whereas, surface Mn³⁺ species are in equivalence with MnO₂ phase in other catalysts (Mn⁴⁺/Mn³⁺ = 0.36-1.34). In H₂-TPR, the disappearance of high-temperature reduction peak at 482 ^oC suggests that the Mn⁴⁺ species are dominant in Mn/TNT-H sample compared to Mn/TiO₂ nanoparticles. Our Raman results illustrate the redshift of 14 cm^-1 from 640 cm^-1 (TiO₂-Hombikat) to 626 cm^-1 in Mn/TNTs-H sample which indicates the formation of a new phase or structural difference. In comparison with the Mn supported on TiO₂ (Hombikat) nanoparticles, the Mn species on the developed tubular Mn/TNT-H were less pronounced to coagulate under the reaction temperatures (100-300 ^oC) and demonstrated an impressive promotion in the deNO_x performance and SCR activity window. The intrinsic activity of the prepared catalysts measured under differential reaction conditions and the effect of morphological features will be discussed in the presentation.