Rationally Designed Confined Structure Ce-Mn-TNTs Catalyst for Low-Temperature NH3-SCR Reaction with Superior Activity and H2O/SO2 Tolerance

The SO2 tolerance of catalysts is often the key factor limiting their catalytic activity during practical applications for low-temperature NH3-SCR reaction. There has been no in-depth research and exploration on the confined location of active components so far. In this work, we investigated the activity and SO2 tolerance of catalysts by loading Mn into cerium-titanium nanotubes (Ce-TNTs) in three different ways. It was found that the Ce-Mn-TNT catalyst with Mn confined in a nanotube structure by the direct strong alkali hydrothermal method showed excellent catalytic activity and strong resistance to SO2 and H2O. This was mainly due to the unique nanotube structure, which provided a large specific surface area and promoted uniform dispersion of active sites. Importantly, the confinement effect of the nanotube structure accelerated the electron transfer rate among Ce, Mn, and Ti metals, which enhanced the redox performance of the catalyst and improved the resistance to SO2. In addition, it was also found that the introduction of Mn increased the amounts of weak acid sites and inhibited oxygen inhibition, enhanced the adsorption of NO on the catalyst surface, and formed more lattice defect structures. Finally, the possible reaction mechanism of the Ce-Mn-TNT catalyst was investigated by in situ DRIFTs. When the gas reaction temperature was 200 °C, it was found that the E-R and L-H reaction pathways coexisted in the NH3-SCR reaction when SO2 was present in the reaction atmosphere.