Cui R, Huang X, Zhang G, Tang Z. Engineering 3D structure Mn/YTiO
x nanotube catalyst with an efficient H
2O and SO
2 tolerance for low-temperature selective catalytic reduction of NO with NH
3.
NANOSCALE 2023;
15:7945-7961. [PMID:
37067024 DOI:
10.1039/d2nr07304h]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
TiO2 with a 3D structure is considered to be a promising support for Mn-based catalysts for the NH3-SCR reaction, but it is still insufficient to solve problems such as poor N2 selectivity and tolerance of H2O/SO2 at low temperature. In this work, a novel 3D-structured Mn/YTiOx nanotube catalyst was designed and the role of Y on the catalytic performance was investigated for the NH3-SCR reaction at low temperature. The results indicated that the Y-doped TiOx 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 MnOx and increase the concentration of surface Mn4+, Lewis acid sites and chemisorbed oxygen of catalysts, which was beneficial to the low-temperature NH3-SCR reaction, while excessive Y doping could cause a sharp decrease in specific surface area and Lewis acid sites. Therefore, Mn/YTiOx 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 N2 selectivity in a wide temperature window from 120 to 320 °C. The N2 selectivity and H2O/SO2 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 NH3 absorbed on Lewis acid sites, -NH2, monodentate nitrate and free nitrate ions were the main reactive intermediate species in the NH3-SCR reaction over an Mn/3%YTiOx catalyst. Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) reaction mechanisms co-existed in the NH3-SCR reaction, but the L-H reaction mechanism predominated.
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