A general and inherent strategy to improve the water tolerance of low temperature NH3-SCR catalysts via trace SiO2 deposition

A series of CeOx catalysts supported by commercial porous cordierite ceramics (CPCC) and synthesized porous cordierite ceramics (SPCC) from fly ash were prepared for selective catalytic reduction of NOx with ammonia (NH3-SCR). A greater than 90% NOx conversion rate was achieved by the SPCC supported catalyst at 250–300 °C when the concentration of loading precursor was 0.6 mol/L (denoted as 0.6Ce/SPCC), which is more advantageous than the CPCC supported ones. The EDS mapping results reveal the existence of evenly distributed impurities on the surface of SPCC, which hence might be able to provide more attachment sites for CeOx particles. Further measurements with temperature programmed reduction by hydrogen (H2-TPR) demonstrate more reducible species on the surface of 0.6Ce/SPCC, thus giving rise to better NH3-SCR performance at a low-temperature range. The X-ray photoelectron spectroscopy (XPS) analyses reveal that the Ce atom ratio is higher in 0.6Ce/SPCC, indicating that a higher concentration of catalytic active sites could be found on the surface of 0.6Ce/SPCC. The in situ diffused reflectance infrared fourier transform spectroscopy (DRIFTS) results indicate that the SCR reactions over 0.6Ce/SPCC follow both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. Hence, the SPCC might be a promising candidate to provide support for NH3-SCR catalysts, which also provide a valuable approach to recycling the fly ash.

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Bulk Vanadium Oxide versus Conventional V2O5/TiO2: NH3–SCR Catalysts Working at a Low Temperature Below 150 °C

ACS Catalysis ◽

10.1021/acscatal.9b02695 ◽

2019 ◽

Vol 9 (10) ◽

pp. 9327-9331 ◽

Cited By ~ 9

Author(s):

Yusuke Inomata ◽

Shinichi Hata ◽

Makoto Mino ◽

Eiji Kiyonaga ◽

Keiichiro Morita ◽

...

Keyword(s):

Low Temperature ◽

Vanadium Oxide ◽

Nh3 Scr ◽

Scr Catalysts

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Comparison of low-temperature catalytic activity and H2O/SO2 resistance of the Ce-Mn/TiO2 NH3-SCR catalysts prepared by the reverse co-precipitation, co-precipitation and impregnation method

Applied Surface Science ◽

10.1016/j.apsusc.2021.151285 ◽

2022 ◽

Vol 571 ◽

pp. 151285

Author(s):

Cheng Chen ◽

Huidong Xie ◽

Peiwen He ◽

Xiao Liu ◽

Chang Yang ◽

...

Keyword(s):

Catalytic Activity ◽

Low Temperature ◽

Impregnation Method ◽

Nh3 Scr ◽

Scr Catalysts ◽

So2 Resistance ◽

Co Precipitation

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Ferrierite and Its Delaminated and Silica-Intercalated Forms Modified with Copper as Effective Catalysts for NH3-SCR Process

Catalysts ◽

10.3390/catal10070734 ◽

2020 ◽

Vol 10 (7) ◽

pp. 734 ◽

Cited By ~ 4

Author(s):

Aneta Święs ◽

Andrzej Kowalczyk ◽

Małgorzata Rutkowska ◽

Urbano Díaz ◽

Antonio E. Palomares ◽

...

Keyword(s):

Low Temperature ◽

Ammonia Oxidation ◽

Catalytic Reduction ◽

Surface Acidity ◽

Side Reaction ◽

Copper Species ◽

Nh3 Scr ◽

Scr Catalysts ◽

Catalytically Active ◽

Fast Scr

The main goal of the study was the development of effective catalysts for the low-temperature selective catalytic reduction of NO with ammonia (NH3-SCR), based on ferrierite (FER) and its delaminated (ITQ-6) and silica-intercalated (ITQ-36) forms modified with copper. The copper exchange zeolitic samples, with the intended framework Si/Al ratio of 30 and 50, were synthetized and characterized with respect to their chemical composition (ICP-OES), structure (XRD), texture (low-temperature N2 adsorption), form and aggregation of deposited copper species (UV-vis-DRS), surface acidity (NH3-TPD) and reducibility (H2-TPR). The samples of the Cu-ITQ-6 and Cu-ITQ-36 series were found to be significantly more active NH3-SCR catalysts compared to Cu-FER. The activity of these catalysts in low-temperature NH3-SCR was assigned to the significant contribution of highly dispersed copper species (monomeric cations and small oligomeric species) catalytically active in the oxidation of NO to NO2, which is necessary for fast-SCR. The zeolitic catalysts, with the higher framework alumina content, were more effective in high-temperature NH3-SCR due to their limited catalytic activity in the side reaction of ammonia oxidation.

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A New Class of Environmental Friendly Vanadate Based NH3 SCR Catalysts Exhibiting Good Low Temperature Activity and High Temperature Stability

SAE International Journal of Engines ◽

10.4271/2011-01-1331 ◽

2011 ◽

Vol 4 (1) ◽

pp. 1839-1849 ◽

Cited By ~ 12

Author(s):

Amod Sagar ◽

Alessandro Trovarelli ◽

Marzia Casanova ◽

Karl Schermanz

Keyword(s):

High Temperature ◽

Low Temperature ◽

Temperature Stability ◽

High Temperature Stability ◽

New Class ◽

Nh3 Scr ◽

Environmental Friendly ◽

Scr Catalysts

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The H2O Effect on Cu Speciation in Cu-CHA-Catalysts for NH3-SCR Probed by NH3 Titration

Catalysts ◽

10.3390/catal11070759 ◽

2021 ◽

Vol 11 (7) ◽

pp. 759

Author(s):

Roberta Villamaina ◽

Federica Gramigni ◽

Umberto Iacobone ◽

Shaojun Liu ◽

Isabella Nova ◽

...

Keyword(s):

Low Temperature ◽

Acid Sites ◽

Lewis Acid Sites ◽

Nh3 Scr ◽

Scr Catalysts ◽

Nh3 Adsorption ◽

Dry Conditions ◽

Dry And Wet Conditions ◽

Hydrolysis Of ◽

Cu Ions

The present work is focused on the effect of water on NH3 adsorption over Cu-CHA SCR catalysts. For this purpose, samples characterized by different SAR (SiO2/Al2O3) ratios and Cu loadings were studied under both dry and wet conditions. H2O adversely affects NH3 adsorption on Lewis acid sites (Cu ions) over all the tested catalysts, as indicated by the decreased NH3 desorption at low temperature during TPD. Interestingly, the NH3/Cu ratio, herein regarded as an index for the speciation of Cu cations, fell in the range of 3–4 (in the presence of gaseous NH3) or 1–2 (no gaseous NH3) in dry conditions, in line with the formation of different NH3-solvated Cu species (e.g., [CuII(NH3)4]2+ and [CuII(OH)(NH3)3]+ with gaseous NH3, [Z2CuII(NH3)2]2+ and [ZCuII(OH)(NH3)]+ without gaseous NH3). When H2O was fed to the system, on the contrary, the NH3/Cu ratio was always close to 3 (or 1), while the Brønsted acidity was slightly increased. These results are consistent both with competition between H2O and NH3 for adsorption on Lewis sites and with the hydrolysis of a fraction of Z2CuII species into ZCuIIOH.

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