Effect of MnO2 Crystalline Structure on the Catalytic Oxidation of Formaldehyde

Lin, Huiqi; Chen, Dong; Li, Haibo; Zou, Xuehua; Chen, Tianhu

doi:10.4209/aaqr.2017.01.0013

Cited by 55 publications

(26 citation statements)

References 42 publications

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“…This comparison allows us to verify if MnO 2 is active, as hypothesized, in the iron oxide reduction or if it only works as iron in the oxidation reactions. According to the literature data, under the adopted operating conditions, MnO 2 can be reduced to MnO during the reduction step and subsequently re‐oxidized to Mn 2 O 3 in the oxidation phase 43 . Assuming that the whole amount of MnO 2 is reduced to MnO and then totally oxidized to Mn 2 O 3 , the hydrogen produced by this reaction should be equal to 0.021 L and 0.082 L for 10 wt% MnO 2 and 40 wt% of MnO 2 , respectively.…”

Section: Resultsmentioning

confidence: 99%

“…According to the literature data, under the adopted operating conditions, MnO 2 can be reduced to MnO during the reduction step and subsequently re-oxidized to Mn 2 O 3 in the oxidation phase. 43 Assuming that the whole amount of MnO 2 is reduced to MnO and then totally oxidized to Mn 2 O 3 , the hydrogen produced by this reaction should be equal to 0.021 L and 0.082 L for 10 wt% MnO 2 and 40 wt% of MnO 2 , respectively. The difference between the H 2 produced with and without the addition of MnO 2 was calculated according to Equation (23).…”

Section: Influence Of Manganese Dioxide Addition In the Process Effmentioning

confidence: 99%

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Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃

et al. 2020

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Summary In the energy transition from fossil to clean fuels, hydrogen plays a key role. Proton‐exchange membrane fuel cells (PEMFCs) represent the most promising hydrogen application, but they require a pure hydrogen stream (CO < 10 ppm). The steam iron process represents a technology for the production of pure H2, exploiting iron redox cycles. If renewable reducing agents are used, the process can be considered completely green. In this context, bio‐ethanol can be an interesting solution that is still not thoroughly explored. In this work, the use of ethanol as a reducing agent in the steam iron process will be investigated. Ethanol, at high temperature, decomposes mainly in syngas but can also form coke, which can compromise the process effectiveness, reacting with water and producing CO together with H2. In this work, the deposition of coke is avoided by controlling the duration of the reduction step; in fact, the data demonstrated that coke deposition is significantly dependent on reduction time. Tests were carried out in a fixed bed reactor using hematite (Fe2O3) as raw iron oxide adopting several reduction times (7 minutes‐25 minutes), which correspond to different amount of ethanol fed (5 mmolC2H5OH/gFe2O3‐17,95 mmolC2H5OH/gFe2O3). The effect of the addition of MnO2 to increase the reduction degree of iron oxides was explored using different amount of MnO2 (10 wt% and 40 wt% with respect to Fe2O3). The tests were performed at fixed temperatures of 675°C and atmospheric pressure. The optimization of the reduction time, in the chosen operating condition, performed only with Fe2O3, shows that, feeding an amount of 5 mmolC2H5OH/gFe2O3, coke deposition is avoided and, therefore, a pure H2 stream in oxidation is obtained. The addition of MnO2 leads to increased H2 yield and process efficiency, confirming its positive effect on the reduction degree of the solid bed. A reaction pathway to demonstrate the synergic effect of Fe2O3 and MnO2 in the reduction step was proposed in this article.

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Section: Resultsmentioning

confidence: 99%

Section: Influence Of Manganese Dioxide Addition In the Process Effmentioning

confidence: 99%

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃

et al. 2020

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“…It was deduced that the sample was in a weakly crystalline state with α-MnO 2 crystallographic forms. 68 This material was characterized by a crystalline structure as K 2 Mn 4 O 9 (Table 1).…”

Section: Xrd Of Mno 2 Lamellar and Nanostructuresmentioning

confidence: 99%

Elaboration of Lamellar and Nanostructured Materials Based on Manganese: Efficient Adsorbents for Removing Heavy Metals

Amarray¹,

Ghachtouli

Himi³

et al. 2020

ACSi

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The lamellar and nanostructured manganese oxide materials were chemically synthesized by soft and non-toxic methods. The materials showed a monophasic character, symptomatic morphologies, as well as the predominance of a mesoporous structure. The removal of heavy metals Cd(II) and Pb(II) by the synthesized materials Na-MnO2, Urchin-MnO2 and Cocoon-MnO2 according to the mineral structure and nature of the sites were also studied. Kinetically, the lamellar manganese oxide material Na-MnO2 was the most efficient of the three materials which had more vacancies in the MnO6 layers as well as in the space between the layers. The nanomaterials Urchin-MnO2 and Cocoon-MnO2 could exchange with the metal cations in their tunnels and cavities, respectively. The maximum adsorbed quantities followed the order (Pb(II): Na-MnO2 (297 mg/g)>Urchin-MnO2 (264 mg/g)>Cocoon-MnO2 (209 mg/g), Cd(II): Na-MnO2 (199 mg/g)>Urchin-MnO2 (191 mg/g)>Cocoon-MnO2 (172 mg/g)). Na-MnO2 material exhibited the best stability among the different structures, Na-MnO2 presented a very low amount of the manganese released. The results obtained showed the potential of lamellar manganese oxides (Na-MnO2) and nanostructures (Urchin-MnO2 and Cocoon-MnO2) as selective, economical, and stable materials for the removal of toxic metals in an aqueous medium.

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“…The peak at 529.4 eV corresponds to lattice oxygen (O 2− ) (denoted as O β ) whereas another shoulder peaks at 530.8 eV and 532.5 eV corresponds to the surface adsorbed oxygen (denoted as O α ) such as O 2 2− or O − belonging to defect-oxide or a hydroxyl-like group (Holgado et al, 2000;. O α species have higher mobility than lattice oxygen, actively take part in the oxidation process and greatly contribute to the catalytic activity (Liu et al, 2014;Lin et al, 2017). It can be seen that the intensity of the O α peaks has an obvious increase in catalysts prepared by plasma, which is quantified by the relative concentration ratio of O α /(O α + O β ).…”

Section: Characterization Of the Catalystsmentioning

confidence: 99%

Non-thermal Plasma Assisted Preparation of MnCeOx, MnOx and CeO2 Catalysts for Enhancement of Surface Active Oxygen and NO Oxidation Activity

Liu

Zheng

et al. 2019

Aerosol Air Qual. Res.

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Non-thermal plasma was used to enhance the synthesis of nanostructured manganese oxide, cerium oxides and MnCeO x composite oxide catalysts via the decomposition of organics and nitrates in an integrated network gel. Pure oxides prepared with plasma formed larger crystallites and exhibited more crystallization. The active oxygen species in the plasma were adsorbed through interaction with ions on the catalyst surface; compared to calcined catalysts, the percentage of active oxygen was 33%, 7% and 20% higher for the plasma-treated MnO x , CeO 2 and MnCeO x , respectively. The percentage of unsaturated Ce 3+ was also 10% higher on the plasma-treated MnCeO x . Furthermore, the NO oxidation efficiency at 275°C for plasma-treated MnO x and MnCeO x was 28% and 21% higher, respectively, than for their calcined counterparts. Due to the lack of significant thermal effects during preparation, the plasma-treated catalysts better retained the structures of their precursors, the even mixtures of manganese oxides and ceria in gel. Additionally, the plasma-treated MnO x and MnCeO x displayed higher formation and decomposition rates for nitrates. The continuous and rapid transformation of NO into nitrates and of nitrates into NO 2 contributes to the excellent oxidation efficiency of these catalysts.

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Effect of MnO2 Crystalline Structure on the Catalytic Oxidation of Formaldehyde

Cited by 55 publications

References 42 publications

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃

Elaboration of Lamellar and Nanostructured Materials Based on Manganese: Efficient Adsorbents for Removing Heavy Metals

Non-thermal Plasma Assisted Preparation of MnCeOx, MnOx and CeO2 Catalysts for Enhancement of Surface Active Oxygen and NO Oxidation Activity

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Effect of MnO2 Crystalline Structure on the Catalytic Oxidation of Formaldehyde

Cited by 55 publications

References 42 publications

Pure hydrogen production by steam‐iron process: The synergic effect of MnO 2 and Fe 2 O 3

Pure hydrogen production by steam‐iron process: The synergic effect of MnO 2 and Fe 2 O 3

Elaboration of Lamellar and Nanostructured Materials Based on Manganese: Efficient Adsorbents for Removing Heavy Metals

Non-thermal Plasma Assisted Preparation of MnCeOx, MnOx and CeO2 Catalysts for Enhancement of Surface Active Oxygen and NO Oxidation Activity

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Product

Resources

About

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃