Calorimetric study on NH3 insertion reaction into microporous manganese oxides with (2×2) tunnel and (2×∞) layered structures

Wang, Z.-M.; Kanoh, Hirofumi

doi:10.1016/s0040-6031(01)00596-2

Cited by 9 publications

(10 citation statements)

References 26 publications

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“…The MnOx aerogel also retains a relatively high NH 3 capacity of 2.3 mol kg −1 when the NH 3 feed stream is mixed with H 2 O vapor to 80% relative humidity, a critical performance characteristic for practical filtration applications. For both aerogel and xerogel MnOx, capture is facilitated in part by intercalation of NH 3 between the layers of the birnessite structure, as previously shown for non-aerogel birnessite-type MnOx (Wang and Kanoh, 2001). In the case of these MnOx nanoarchitectures, the walls of the networked solid have built-in sites for the specific capture/ sieving of NH 3 , which readily diffuses to these active sites via the through-connected pore network.…”

Section: Optimization Of Oxide/hydroxide Phases In Zirconium-and Manganese-based Aerogelssupporting

confidence: 59%

Designing Oxide Aerogels With Enhanced Sorptive and Degradative Activity for Acute Chemical Threats

et al. 2021

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Oxide aerogels are pore–solid networks notable for their low density, large pore volume, and high surface area. This three-dimensional arrangement of pore and solid provides critical properties: the high surface area required to maximize the number of active sites and a through-connected porosity that plumbs reactants to the active interior. In decontamination applications where reactivity beyond adsorption is desired to degrade deleterious molecules, oxide aerogels offer multiple avenues to add oxidative power to this unique arrangement of pore and solid. For protection against chemical warfare agents or toxic industrial chemicals, metal-oxide aerogels with their oxide/hydroxide surfaces afford stability under ambient conditions against competing sorbents such as water and oxygen. In this review, strategies to maximize sorptive capacity and degradation rate by modifying surface functionality, compositing with dissimilar oxides, or adding metallic nanoparticles and the subsequent impact on decontamination performance will be summarized and expected directions for future research will be discussed based on the observed trends.

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Section: Optimization Of Oxide/hydroxide Phases In Zirconium-and Manganese-based Aerogelssupporting

confidence: 59%

Designing Oxide Aerogels With Enhanced Sorptive and Degradative Activity for Acute Chemical Threats

et al. 2021

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“…Manganese oxides (MnO x ) comprise a large family of naturally occurring and synthetic materials that are of interest for applications ranging from electrochemical energy storage − to catalysis. − Many crystalline polymorphs of MnO x are constructed of MnO 6 octahedra that assemble into inherently microporous forms of either tunnel (e.g., hollandite) or layered (e.g., birnessite) structures, a characteristic that enables their use as molecule- and ion-sieving sorbents . Hollandite- and birnessite-type MnO x structures readily incorporate gas-phase NH 3 within their microporous structures − to provide filtration activity for a toxic industrial chemical (TIC) that is ordinarily difficult to capture due to its high vapor pressure. In addition to physical capture, many forms of manganese oxides are catalytically active for oxidation reactions, enabled by facile interconversion of Mn oxidation state (e.g., between +3 and +4) and the rich defect chemistry that is available in nonstoichiometric MnO x compositions. , For example, MnO x substrates effectively promote the oxidation of formaldehyde, − another TIC for which abatement strategies are desired.…”

Section: Introductionmentioning

confidence: 99%

Manganese Oxide Nanoarchitectures as Broad-Spectrum Sorbents for Toxic Gases

Long

Wallace

Peterson

et al. 2016

ACS Appl. Mater. Interfaces

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We demonstrate that sol-gel-derived manganese oxide (MnOx) nanoarchitectures exhibit broad-spectrum filtration activity for three chemically diverse toxic gases: NH3, SO2, and H2S. Manganese oxides are synthesized via the reaction of NaMnO4 and fumaric acid to form monolithic gels of disordered, mixed-valent Na-MnOx; incorporated Na(+) is readily exchanged for H(+) by subsequent acid rinsing to form a more crystalline H-MnOx phase. For both Na-MnOx and H-MnOx forms, controlled pore-fluid removal yields either densified, yet still mesoporous, xerogels or low-density aerogels (prepared by drying from supercritical CO2). The performance of these MnOx nanoarchitectures as filtration media is assessed using dynamic-challenge microbreakthrough protocols. We observe technologically relevant sorption capacities under both dry conditions and wet (80% relative humidity) for each of the three toxic industrial chemicals investigated. The Na-MnOx xerogels and aerogels provide optimal performance with the aerogel exhibiting maximum sorption capacities of 39, 200, and 680 mg g(-1) for NH3, SO2, and H2S, respectively. Postbreakthrough characterization using X-ray photoelectron spectroscopy (XPS) and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) confirms that NH3 is captured and partially protonated within the MnOx structure, while SO2 undergoes oxidation by the redox-active oxide to form adsorbed sulfate at the MnOx surface. Hydrogen sulfide is also oxidized to form a combination of sulfate and sulfur/polysulfide products, concomitant with a decrease in the average Mn oxidation state from 3.43 to 2.94 and generation of a MnOOH phase.

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“…The birnessite-type (Na 4 Mn 14 O 27 $9H 2 O) or (d-MnO 2 ) is one of the most active and common forms of mineralised manganese in soil, sediments, and water. It is a strong adsorbent of mineral ions and acts as a scavenger in marine and freshwater environments (James and Stahl, 1991;Renuka and Ramamurthy, 2000;Wang and Kanoh, 2001).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite

Al-Ghouti

Al‐Degs

Khraisheh

et al. 2009

Journal of Environmental Management

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Calorimetric study on NH3 insertion reaction into microporous manganese oxides with (2×2) tunnel and (2×∞) layered structures

Cited by 9 publications

References 26 publications

Designing Oxide Aerogels With Enhanced Sorptive and Degradative Activity for Acute Chemical Threats

Designing Oxide Aerogels With Enhanced Sorptive and Degradative Activity for Acute Chemical Threats

Manganese Oxide Nanoarchitectures as Broad-Spectrum Sorbents for Toxic Gases

Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite

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