Design of meso-TiO2@MnOx–CeOx/CNTs with a core–shell structure as DeNOx catalysts: promotion of activity, stability and SO2-tolerance

Abstract

Developing low-temperature deNOx catalysts with high catalytic activity, SO2-tolerance and stability is highly desirable but remains challenging. Herein, by coating the mesoporous TiO2 layers on carbon nanotubes (CNTs)-supported MnOx and CeOx nanoparticles (NPs), we obtained a core-shell structural deNOx catalyst with high catalytic activity, good SO2-tolerance and enhanced stability. Transmission electron microscopy, X-ray diffraction, N2 sorption, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction and NH3 temperature-programmed desorption have been used to elucidate the structure and surface properties of the obtained catalysts. Both the specific surface area and chemisorbed oxygen species are enhanced by the coating of meso-TiO2 sheaths. The meso-TiO2 sheaths not only enhance the acid strength but also raise acid amounts. Moreover, there is a strong interaction among the manganese oxide, cerium oxide and meso-TiO2 sheaths. Based on these favorable properties, the meso-TiO2 coated catalyst exhibits a higher activity and more extensive operating-temperature window, compared to the uncoated catalyst. In addition, the meso-TiO2 sheaths can serve as an effective barrier to prevent the aggregation of metal oxide NPs during stability testing. As a result, the meso-TiO2 overcoated catalyst exhibits a much better stability than the uncoated one. More importantly, the meso-TiO2 sheaths can not only prevent the generation of ammonium sulfate species from blocking the active sites but also inhibit the formation of manganese sulfate, resulting in a higher SO2-tolerance. These results indicate that the design of a core-shell structure is effective to promote the performance of deNOx catalysts.

Fe‐Beta@CeO2 core‐shell catalyst with tunable shell thickness for selective catalytic reduction of NOx with NH3

“…Zhang et al 23 synthesized Pd@CeO 2 CSCs by a combination of sol-gel and hydrothermal reaction, which showed high activity toward the reduction of aromatic nitro compounds attributed to CeO 2 shell preventing the migration and aggregation of Pd nanoparticles (NPs) in the catalytic reaction. Zhang et al 24 presented TiO 2 @MnCe/carbon-nanotubes (CNTs) CSCs to be employed in NH 3 -SCR reaction. TiO 2 shells not only inhibited the generation of manganese sulfate, but also suppressed the formation of ammonium sulfate species covering the active sites.…”

Enhanced Oxygen Vacancies in a Two-Dimensional MnAl-Layered Double Oxide Prepared via Flash Nanoprecipitation Offers High Selective Catalytic Reduction of NOx with NH3

“…Previous reports have shown that in low-temperature SCR reactions, free NH 3 is absorbed on the lattice oxygen and then activated into an amino group. This generates intermediate products [34,35]. Therefore, the increased lattice oxygen content could enhance the oxidation capacity on the surface of the catalyst and promote a “fast SCR” reaction.…”

Low-temperature selective catalytic reduction of NO with NH3 over ordered mesoporous MnxCo3−xO4 catalyst

“…Cr 2 O 3 , Co 3 O 4 , CuO, or MnO 2 ) show good activity for LT-SCR reaction [5][6][7]. Among all metal oxides studied, manganese and cobalt containing catalysts are low cost, environmentally friendly and relatively highly active for NO reduction.…”