A study on non-isothermal kinetics of the thermal decompositions of β-manganese dioxide

Lei, Lin; He, Ming; Zhang, Aihua; Zhou, Jia Liang

doi:10.1016/j.tca.2011.05.026

Cited by 21 publications

(9 citation statements)

References 36 publications

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“…Whereas the formation of Mn 3 O 4 may occur in the temperature range used to collect the residue, the contribution of Mn 2 O 3 or even a formulation considering the residue as a mixture of Mn oxides cannot be completely ruled out at this point as vibrational data on Mn oxides are markedly dependent on polymorphism composition and the grain size of the material [33-35], which are properties that were not investigated in this work. The formulation of the residue as Mn 3 O 4 , Mn 2 O 3 , or a mixture of both is consistent with the well established temperature-dependent stability of the various Mn oxides [36-38]. …”

Section: Resultssupporting

confidence: 74%

Thermal stability of the prototypical Mn porphyrin-based superoxide dismutase mimic and potent oxidative-stress redox modulator Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride, MnTE-2-PyP5+

Pinto

CarvalhoDa-Silva

Santos

et al. 2013

Journal of Pharmaceutical and Biomedical Analysis

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Cationic Mn porphyrins are among the most potent catalytic antioxidants and/or cellular redox modulators. Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride (MnTE-2-PyPCl5) is the Mn porphyrin most studied in vivo and has successfully rescued animal models of a variety of oxidative stress-related diseases. The stability of an authentic MnTE-2-PyPCl5 sample was investigated hereon by thermogravimetric, derivative thermogravimetric, and differential thermal analyses (TG/DTG/DTA), under dynamic air, followed by studies at selected temperatures to evaluate the decomposition path and appropriate conditions for storage and handling of these materials. All residues were analyzed by thin-layer chromatography (TLC) and UV-vis spectroscopy. Three thermal processes were observed by TG/DTG. The first event (endothermic) corresponded to dehydration, and did not alter the MnTE-2-PyPCl5 moiety. The second event (endothermic) corresponded to the loss of EtCl (dealkylation), which was characterized by gas chromatography-mass spectrometry. The residue at 279 °C had UV-vis and TLC data consistent with those of the authentic, completely dealkylated analogue, MnT-2-PyPCl. The final, multi-step event corresponded to the loss of the remaining organic matter to yield Mn3O4 which was characterized by IR spectroscopy. Isothermal treatment at 188 °C under static air for 3 h yielded a mixture of partially dealkylated MnPs and traces of the free-base, dealkylated ligand, H2T-2-PyP, which reveals that dealkylation is accompanied by thermal demetallation under static air conditions. Dealkylation was not observed if the sample was heated as a solid or in aqueous solution up to ∼100 °C. Whereas moderate heating changes sample composition by loss of H2O, the dehydrated sample is indistinguishable from the original sample upon dissolution in water, which indicates that catalytic activity (on Mn basis) remains unaltered. Evidently, dealkylation at high temperature compromises sample activity.

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Section: Resultssupporting

confidence: 74%

Thermal stability of the prototypical Mn porphyrin-based superoxide dismutase mimic and potent oxidative-stress redox modulator Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride, MnTE-2-PyP5+

Pinto

CarvalhoDa-Silva

Santos

et al. 2013

Journal of Pharmaceutical and Biomedical Analysis

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“…3 and Supplementary Information 2 ). Based on the infra-red thermal imaging data, the transformation of the manganese dioxide to hausmannite, Mn 3 O 4 in the combustion experiments, occurred at unexpectedly low temperatures compared with the temperatures normally required for this process 35 36 (see also Supplementary Information 4 ).…”

Section: Resultsmentioning

confidence: 99%

Selection and Use of Manganese Dioxide by Neanderthals

Heyes

Anastasakis

Jong

et al. 2016

Sci Rep

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Several Mousterian sites in France have yielded large numbers of small black blocs. The usual interpretation is that these ‘manganese oxides’ were collected for their colouring properties and used in body decoration, potentially for symbolic expression. Neanderthals habitually used fire and if they needed black material for decoration, soot and charcoal were readily available, whereas obtaining manganese oxides would have incurred considerably higher costs. Compositional analyses lead us to infer that late Neanderthals at Pech-de-l’Azé I were deliberately selecting manganese dioxide. Combustion experiments and thermo-gravimetric measurements demonstrate that manganese dioxide reduces wood’s auto-ignition temperature and substantially increases the rate of char combustion, leading us to conclude that the most beneficial use for manganese dioxide was in fire-making. With archaeological evidence for fire places and the conversion of the manganese dioxide to powder, we argue that Neanderthals at Pech-de-l’Azé I used manganese dioxide in fire-making and produced fire on demand.

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“…Due to the complexity of the thermal decomposition reaction system, the calculation models of activation energy are deduced on the basis of certain assumptions and approximations . The most basic assumption is based on two basic theorems of classical chemical dynamics—the law of mass action and the Arrhenius theorem, both of which are represented by Equations and , respectively:

\frac{normald α}{normald t} = f ((), α) \cdot K ((), T),

k = A \cdot \exp ((), - E / italicRT),

where α is the conversion ratio, %, and can also be called the reaction progress or the conversion rate of the solid reaction; t is time, s; K ( T ) represents the relationship between the rate constant and the temperature; f ( α ) is the mechanism function of the reaction; A is the preexponential factor, and T is the reaction temperature, K.…”

Section: Methodsmentioning

confidence: 99%

Thermal conversion mechanism and thermodynamics of mixed oil in coal‐based needle coke production

Cheng

Xin

Gao

et al. 2019

Asia-Pacific J Chem Eng

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In this work, the kinetic and thermodynamic parameters of mixed oil during the process of thermal conversion are analyzed using a kinetic model and thermodynamic calculations combined with thermogravimetric analysis. On the basis of the Flynn-Wall-Ozawa kinetic model, the calculated activation energies change in the reaction progress of mixed oil. Additionally, the thermal conversion process can be divided into three stages. The reaction mechanism is the exponential law mode in the first phase, and the latter two stages belong to the random nucleation and subsequent growth model, but they have completely different ways of nucleation and crystal growth. During the whole thermal conversion of mixed oil, △H ≠ > 0, and it does not show that the thermal conversion of mixed oil is a completely endothermic process; △G ≠ > 0 and represents a nonspontaneous reaction; and the change of the △S ≠ value is the most complicated.

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A study on non-isothermal kinetics of the thermal decompositions of β-manganese dioxide

Cited by 21 publications

References 36 publications

Thermal stability of the prototypical Mn porphyrin-based superoxide dismutase mimic and potent oxidative-stress redox modulator Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride, MnTE-2-PyP5+

Thermal stability of the prototypical Mn porphyrin-based superoxide dismutase mimic and potent oxidative-stress redox modulator Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride, MnTE-2-PyP5+

Selection and Use of Manganese Dioxide by Neanderthals

Thermal conversion mechanism and thermodynamics of mixed oil in coal‐based needle coke production

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