Mechanism and kinetics of the selective NO reduction over Co-ZSM-5 studied by the SSITKA technique

Sadovskaya, E. M.; Suknev, A.P.; Пинаева, Л. Г.; Goncharov, V. B.; Бальжинимаев, Б. С.; Chupin, C; Pérez‐Ramírez, Javier; Mirodatos, C.

doi:10.1016/j.jcat.2004.03.032

Cited by 46 publications

(14 citation statements)

References 23 publications

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“…With further increasing the cobalt loading ratio, excess cobalt coexisting in small Co x O y clusters (CoO, Co 2 O 3 , Co 3 O 4 , etc.) constitute the majority of the species in overexchanged catalysts ,− and are potentially a good candidate for performing SCR activity at the HT-peak (Figure ), resulting in the HT-peak shifting toward lower temperatures. With increasing cobalt content, the P NO at the HT-peak shows a declining trend after an initial ascent.…”

Section: Resultsmentioning

confidence: 99%

Structural Characterization and Selective Catalytic Reduction of Nitrogen Oxides with Ammonia: A Comparison between Co/ZSM-5 and Co/SBA-15

Bin

Chen

et al. 2012

J. Phys. Chem. C

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Cobalt-containing catalysts supported on ZSM-5 zeolite and mesoporous siliceous SBA-15 were prepared and characterized by nitrogen sorption, X-ray diffraction, scanning electron and transmission electron microscopies, energydispersive X-ray, Fourier transform infrared, ultraviolet−visible diffuse reflectance, X-ray photoelectron spectroscopies, and temperature-programmed desorption of ammonia measurement. The effect of cobalt loading ratio on the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia was investigated. The existing Brønsted acid sites contributed to the cobalt species finely dispersed within the ZSM-5 zeolite, either as isolated cobalt ions anchored at α, β, and γ sites, or as amorphous cobalt oxides enriched on the ZSM-5 surface. NO x conversion profiles of Co/ZSM-5 exhibited two peaks. The low-temperature peak (<300 °C) was induced by cobalt ions at β and γ sites, while the high-temperature peak (>300 °C) was assigned to the amorphous and crystalline cobalt oxides. With increasing cobalt content, the intensity of lowtemperature peak was enhanced monotonously, and the peak position remained constant. Increasing cobalt content promoted the high-temperature peak to shift toward lower temperatures. NO x conversion profiles of Co/SBA-15 only exhibited a hightemperature peak. For Co/SBA-15, the poor dispersion of cobalt species was derived from the absence of Brønsted acid sites. The activity of Co/SBA-15 catalysts was lower than that of the Co/ZSM-5 catalysts due to inactive cobalt ions anchored on isolated Si−OH groups, and agglomerated cobalt oxides within the SBA-15 channels blocking the reactant pathway to active sites.

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Section: Resultsmentioning

confidence: 99%

Structural Characterization and Selective Catalytic Reduction of Nitrogen Oxides with Ammonia: A Comparison between Co/ZSM-5 and Co/SBA-15

Bin

Chen

et al. 2012

J. Phys. Chem. C

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“…Cobalt zeolites are important catalysts for the selective catalytic reduction (SCR) of nitrogen oxides by hydrocarbons, especially by methane [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. It is widely accepted that depending on the used zeolite, its Si/Al ratio, Co content, and preparation method, different Co species are formed comprising: (i) Co 2+ cations located in the zeolite channels, (ii) CoO x microaggregates, and (iii) CoO, Co 3 O 4 , as well as Co silicate mainly in the case of over-exchanged zeolites.…”

Section: Introductionmentioning

confidence: 99%

Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

et al. 2020

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UV–Vis spectroscopy as well as in situ FTIR spectroscopy of pyridine and CO adsorption were applied to determine the nature of Co species in microporous, mesoporous, and mixed oxide materials like Co–ZSM-5, Co/Na–ZSM-5, Co/Al–SBA-15, and Co/Al2O3–SiO2. Because all sample types show comparable UV–Vis spectra with a characteristic band triplet, the former described UV–Vis band deconvolution method for determination and quantification of individual cationic sites in the zeolite appears doubtful. This is also confirmed by results of pyridine and CO adsorption revealing that all Co–zeolite samples contain two types of Co2+ species located at exchange positions as well as in oxide-like clusters independent of the Co content, while in Co/Al–SBA-15 and Co/Al2O3–SiO2 only Co2+ species in oxide-like clusters occur. Consequently, the measured UV–Vis spectra represent not exclusively isolated Co2+ species, and the characteristic triplet band is not only related to γ-, β-, and α-type Co2+ sites in the zeolite but also to those dispersed on the surface of different oxide supports. The study demonstrates that for proper characterization of the formed Co species, the use of complementary methods is required.

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“…In the oxidized form cobalt-containing zeolites, such as Co-FER, Co-MFI and Co-MOR, are active catalysts for reducing NO with methane in oxidizing atmosphere, so allowing the denitrification (DeNOxing) of waste gases. Co 2+ ions exchanging the protons of the protonic zeolites are considered to be the active sites in the reaction, while other authors suggested the presence of “extraframework” CoOx oxide clusters to represent the catalytically active species . In a series of recent papers the UV–vis spectra of Co-FER, Co-MFI and Co-MOR have been studied in detail and assigned to Co 2+ ions in different locations in the zeolite cavities. − The possible cooperation of residual protonic sites and Co cationic sites in partially exchanged Co-zeolites for the CH 4 –SCR reaction has also been discussed .…”

Section: Introductionmentioning

confidence: 99%

Solid-State NMR Characterization of the Insertion of Cobalt into Aluminosilicate Materials

et al. 2011

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The location of cobalt in two porous metalsubstituted zeolites, mordenite and ZSM5, and in a reference amorphous silicoalumina material, was investigated by solidstate NMR spectroscopy. The hyperfine shift and pseudoshift effects due to the paramagnetic metal on the NMR spectra of silicon and aluminum were used to estimate the number of aluminum and silicon framework sites in proximity of the cobalt. It was possible to confirm previous IR findings that only a fraction of the SiOHAl sites were involved directly in the bonding of the metal. A semiquantitative solid-state NMR analysis proved that siloxane bridges, and preferentially those close to aluminum locations, played a concurrent marked binding role in zeolites. It was found that for both zeolites the metal penetrates deeply into the structure. Furthermore, analysis of the NMR spectra implies that the cobalt position must be crystallographically well determined.

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Mechanism and kinetics of the selective NO reduction over Co-ZSM-5 studied by the SSITKA technique

Cited by 46 publications

References 23 publications

Structural Characterization and Selective Catalytic Reduction of Nitrogen Oxides with Ammonia: A Comparison between Co/ZSM-5 and Co/SBA-15

Structural Characterization and Selective Catalytic Reduction of Nitrogen Oxides with Ammonia: A Comparison between Co/ZSM-5 and Co/SBA-15

Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

Solid-State NMR Characterization of the Insertion of Cobalt into Aluminosilicate Materials

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