The Reduction and Oxidation of Co Species in CoZSM-5 Zeolites Studied by IR Spectroscopy

Góra‐Marek, Kinga

doi:10.1007/s11244-009-9260-y

Cited by 8 publications

(8 citation statements)

References 20 publications

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“…Briefly, it was attributed either to Co 2+ -mononitrosyl [6,7], or to Co 3+ -mononitrosyl in Co-ZSM-5 [44,48]. It was emphasized, however, that latter species must carry an oxygen ligand that lowers the charge on the cobalt [49,50]. It was argued that it is highly improbable that bare Co 3+ ions could neutralize three distant negative charges of the zeolite having high framework Si to Al ratio (>15).…”

Section: Catalytic Resultsmentioning

confidence: 99%

Mechanism of NO-SCR by methane over Co,H-ZSM-5 and Co,H-mordenite catalysts

Lónyi

Solt

Pászti

et al. 2014

Applied Catalysis B: Environmental

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Section: Catalytic Resultsmentioning

confidence: 99%

Mechanism of NO-SCR by methane over Co,H-ZSM-5 and Co,H-mordenite catalysts

Lónyi

Solt

Pászti

et al. 2014

Applied Catalysis B: Environmental

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“…A suitable method for characterizing the nature of Co species is adsorption of CO at low temperatures [12,13,[42][43][44]. Thus, one can distinguish Co 2+ located at exchange positions from Co 2+ being part of oxide-like clusters because the respective νCo 2+ −CO bands appear at different positions, namely at 2204 cm −1 for Co 2+ in exchange positions and at 2194 cm −1 for Co 2+ in oxide-like clusters.…”

Section: Ftir Studies: Pyridine and Co Adsorptionmentioning

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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“…The bands at 2133 and 2141 cm −1 are correlated with physically adsorbed CO molecules 34 . The bands at 2160 cm −1 are assigned to CO adsorbed on SiOH species, 35 which is only observed in Co‐acac@S‐1 catalyst. Thus, we infer that the defect SiOH species in Co‐edta@S‐1 were consumed to coordinate with framework Co species, which is in line with CO‐FTIR spectra in OH group region as discussed below.…”

Section: Resultsmentioning

confidence: 97%

“…Thus, we infer that the defect SiOH species in Co‐edta@S‐1 were consumed to coordinate with framework Co species, which is in line with CO‐FTIR spectra in OH group region as discussed below. Importantly, the bands at 2176 cm −1 are ascribed to CO adsorbed on CoO clusters, 34–36 which was only detected in Co‐acac@S‐1 catalyst. Besides, this band at 2176 cm −1 in Co‐acac@S‐1 is slightly blue shifted with the increasing of CO pressure, which is explained by the coupling of CO molecules adsorbed on adjacent Co atoms in clusters 37 .…”

Section: Resultsmentioning

confidence: 99%

In situ encapsulated subnanometric CoO clusters within silicalite‐1 zeolite for efficient propane dehydrogenation

Song

et al. 2021

AIChE Journal

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Cobalt‐based catalysts are promising alternatives to replace Pt‐ and Cr‐based catalysts for propane dehydrogenation (PDH). However, the sintering and reduction of unstable Co sites cause fast deactivation. Herein, the ultrasmall cobalt oxide clusters encapsulated within silicalite‐1 zeolites (CoO@S‐1) has been obtained via a ligand assistance in situ crystallization method. This CoO@S‐1 catalyst exhibits an attractive propylene formation rate of 13.66 mmolC3H6·gcat−1·h−1 with selectivity of >92% and is durable during 120‐h PDH reaction with five successive regeneration cycles. The high PDH activity of CoO@S‐1 is assigned to the encapsulated CoO clusters are favorable for propane adsorption and can better stabilize the detached H* species from propane, leading to the lower dehydrogenation barriers than framework Co2+ cations and Co3O4 nanoparticles. Additionally, the π‐binding propylene on CoO clusters can prevent the over‐dehydrogenation reaction compared with the di‐σ binding propylene on metallic Co, leading to the superior propylene selectivity and catalytic stability.

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The Reduction and Oxidation of Co Species in CoZSM-5 Zeolites Studied by IR Spectroscopy

Abstract: The process of reducing Co ions in zeolite CoZSM-5 by NO, H 2 and CO, as well as of oxidizing them by O 2 was studied by IR spectroscopy with CO as the probe molecule for Co 2? and NO as the probe for Co 3? .

Cited by 8 publications

References 20 publications

Mechanism of NO-SCR by methane over Co,H-ZSM-5 and Co,H-mordenite catalysts

Mechanism of NO-SCR by methane over Co,H-ZSM-5 and Co,H-mordenite catalysts

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

In situ encapsulated subnanometric CoO clusters within silicalite‐1 zeolite for efficient propane dehydrogenation

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