Engineering 3D structure Mn/YTiO x nanotube catalyst with an efficient H 2 O and SO 2 tolerance for low-temperature selective catalytic reduction of NO with NH 3 .

TiO 2 with a 3D structure is considered to be a promising support for Mn-based catalysts for the NH 3 -SCR reaction, but it is still insufficient to solve problems such as poor N 2 selectivity and tolerance of H 2 O/SO 2 at low temperature. In this work, a novel 3D-structured Mn/YTiO x nanotube catalyst was designed and the role of Y on the catalytic performance was investigated for the NH 3 -SCR reaction at low temperature. The results indicated that the Y-doped TiO x gradually transformed from nanotubes to nanosheets with the increase in Y doping, leading to a reduction in specific surface area and Brønsted acid sites. An appropriate amount of Y doping could distinctly improve the dispersion of MnO x and increase the concentration of surface Mn 4+ , Lewis acid sites and chemisorbed oxygen of catalysts, which was beneficial to the low-temperature NH 3 -SCR reaction, while excessive Y doping could cause a sharp decrease in specific surface area and Lewis acid sites. Therefore, Mn/YTiO x catalysts exhibited a volcano-type tendency in NO conversion with an increase in Y doping, and the highest activity was obtained at 3% doping, showing more than 90% NO conversion and N 2 selectivity in a wide temperature window from 120 to 320 °C. The N 2 selectivity and H 2 O/SO 2 resistance of the catalysts was also enhanced with the increase in Y doping mainly due to the increased chemisorbed oxygen and electron transfer between Y and Mn. An in situ DRIFTS study demonstrated that Lewis acid sites played a more important role in the reaction than Brønsted acid sites, and the coordinated NH 3 absorbed on Lewis acid sites, -NH 2 , monodentate nitrate and free nitrate ions were the main reactive intermediate species in the NH 3 -SCR reaction over an Mn/3%YTiO x catalyst. Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) reaction mechanisms co-existed in the NH 3 -SCR reaction, but the L-H reaction mechanism predominated.