Thermal Decomposition Of Potassium Permanganate Research Articles

Catalytically active composite materials with porous aluminum oxide matrix modified by γ-MnO2 nanoparticles

Manganese dioxide has been deposited on the surface of an aluminum foil anodized in 3% solution of oxalic acid using the methods of thermal decomposition of manganese nitrate and potassium permanganate, as well as chemical synthesis, in the same solutions with intermediate drying and subsequent annealing. It has been demonstrated that the method of thermal decomposition of potassium permanganate is the most suitable for producing thermally stable “ultradispersed γ-MnO2/nanostructured Al2O3/Al” composites. The produced composites are active in the reaction of oxidation of CO into CO2 at temperatures above 180°C. Studies by means of the methods of scanning electron and atomic force microscopies have shown that the concentration and surface distribution of γ-MnO2 particles depend on the morphological structure of aluminum oxide that is determined by conditions of the metal surface pretreatment and application of the pore broadening operation.

Problems and faulty uses with the Prout–Tompkins description of autocatalytic reactions and the solutions

The investigation of materials containing higher energy, such as peroxides, highly oxidized salts, nitrated organic compounds, leads very quickly to the need for autocatalytic description of decomposition data. The autocatalytic behaviour shows generally a sigmoid change of the conversion. There are several types of autocatalytic equations—one is the Prout–Tompkins (PT) equation. The PT equation is a reaction kinetic model belonging to a series of models with a single reaction rate constant, which are favourably used in the field of reaction kinetic-based thermal analyses. The PT equation was developed and published in the 1940s by E.G. Prout and F.C. Tompkins, which tried to describe reaction kinetically their observations on the thermal decomposition of potassium permanganate. They recognized the autocatalytical behaviour of this decomposition and developed step by step the full autocatalytic description. But, in spite of using the full description with two reaction rate constants, they simplified the expression and kept only the autocatalytic part of the complete reaction scheme and of the rate equation by arguing that this part is much faster than the primary or intrinsic part and determines nearly totally the conversion of the substance. This can be right, depending on the system considered. But this simplification has resulted in a lot of application problems and also in problems to formulate the model in a correct way. In this paper, the problem is analysed and the viable solution will be given, which is called the improved PT model. Further, a lot of papers and applications can be found in the literature, which are a commingling of several concepts. The corresponding equations have an appearance as the PT equation, but in reaction kinetic terms, they are applied in a faulty way. This point is discussed also to dissolve the commingling and to foster the proper application of an autocatalytic description. For completion of the discussed equations and their usefulness in understanding the equations, the characteristic quantities ‘time to reach a certain degree of degradation’, ‘time to maximum rate’ and ‘conversion at maximum rate’ are presented. Finally, some other equations are discussed, which are able to describe autocatalytic behaviour in that they are transformed to the PT equation by choosing the appropriate reaction orders. However, not every sigmoid change in conversion is caused by autocatalysis, and in spite of this fact autocatalytic descriptions are used for such cases and one example of such a faulty use is discussed.

Alumina-Supported Manganese Catalysts for Soot Combustion Prepared by Thermal Decomposition of KMnO4

Alumina-supported manganese catalysts with cryptomelane and/or birnessite structure have been prepared using a simple method based on the thermal decomposition of potassium permanganate. The samples have been characterized by XRD, FTIR, TGA, DSC, N2 adsorption at −196 °C, SEM, H2-TPR and XPS, and their catalytic activity for soot combustion has been tested and compared to that of a reference Pt/alumina catalyst. The thermal decomposition of alumina-supported KMnO4 yields a mixture of supported birnessite and potassium manganate which is the most effective, among those prepared, to lower the soot combustion temperature. However, this material is not useful for soot combustion because the accelerating effect is not based on a catalytic process but on the oxidation of soot by potassium manganate. A suitable soot combustion catalyst is obtained after potassium manganate is removed by water washing, yielding only the birnessite phase on the γ-Al2O3 support. This birnessite phase can be transformed into cryptomelane by calcination at 600 °C. These two samples, γ-Al2O3-supported birnessite and cryptomelane are suitable catalysts for soot combustion in NOx/O2 mixtures, as their catalytic activity is based on the NO2-assited mechanism, that is, both catalysts accelerate the oxidation of NO to NO2 and NO2 promotes soot oxidation. The soot combustion temperatures obtained with these birnessite/cryptomelane alumina-supported catalysts are similar to that obtained with the reference Pt/alumina catalyst.

Soot combustion manganese catalysts prepared by thermal decomposition of KMnO4

Manganese oxides with cryptomelane and/or birnessite structure have been successfully prepared by thermal decomposition of potassium permanganate. The samples have been characterized by XRD, FTIR, TGA, N2 adsortion at −196°C, H2-TPR and XPS, and have been evaluated as catalysts for soot combustion in a NOx/O2 gas mixture. KMnO4 decomposition at 400°C yields birnessite and potassium manganate, and the latter can be removed by water washing. Further calcination at 600°C of the washed birnessite leads to the increase of the birnessite crystallinity and to the partial transformation into cryptomelane. For the unwashed sample, the catalytic effect of potassium, which forms low melting temperature compounds upon NOx chemisorption, controls the catalytic combustion of soot in a NOx/O2 gas mixture. On the contrary, the combustion of soot assisted by these birnessite and cryptomelane catalysts (once manganese salts have been removed) occurs by the NO2 mechanism, and these catalysts seem promising candidates for practical application in the regeneration of DPF filters.

Old and new studies of the thermal decomposition of potassium permanganate

The overall chemical equation representing the thermal decomposition of potassium permanganate up to ≈300°C is given approximately by: 10 KMnO4→2.65 K2MnO4+[2.35 K2O·7.35·MnO2.05]+6O2, the bracketed material being δ-MnO2. The experimental mass loss in air is ≈12% and the enthalpy of decomposition is ≈10 kJ/mol of KMnO4. Analysis of published kinetic studies of the decomposition show that most of the results can be represented by the Prout-Tompkins equation ln (x/(1−x))=k T t+constant, and insertion of the rate constants into the Arrhenius equation gives an activation energy for decomposition of ≈150 kJ/mol of KMnO4. Although the kinetic studies have always been interpreted in terms of a single type of chemical decomposition, with the different rates encountered during the course of the decomposition ascribed to physical effects, X-ray diffraction studies by Boldyrev and co-workers have shown that the reaction actually occurs in two stages, with essentially all the KMnO4 transformed into K3(MnO4)2, δ-MnO2 and O2 in the first stage, and the K3(MnO4)2 then decomposing into K2MnO4 and more δ-MnO2 and O2 in the second stage. We have confirmed the Boldyrev diffraction results and extended them by measuring the kinetics of the appearance and disappearance of K3(MnO4)2 by an X-ray diffraction method. Our earlier isotopes studies have shown that the oxygen molecules come from oxygen atoms produced by breaking Mn−O bonds in different permanganate ions i.e. the decomposition mechanism is interionic. We conclude by summarising what is, and is not, currently known about the thermal decomposition of potassium permanganate up to ≈300°C.

The Triple Point of Oxygen In Sealed Transportable Cells.

The triple points of oxygen samples sealed in miniature pressure cells were investigated by means of adiabatic calorimetry. The triple point of a 99.999 percent pure commercial oxygen sample was found to be 0.940 mK higher than that of an "ultra-pure" sample prepared by thermal decomposition of potassium permanganate (KMnO4). The higher value is attributed principally to argon impurity in the commercial oxygen. The results of eight sets of observations using six thermometers, calibrated on the International Practical Temperature Scale of 1968 as maintained at the National Bureau of Standards, and two sealed cells of the ultra-pure oxygen show a range of 0.178 mK. The capsule-type platinum resistance thermometers that have been used are shown to have outstanding stability and the multiple calibrations made on them at the National Bureau of Standards extending over six years are shown to be consistent to within 0.15 mK at 54.361 K. The results of measurements on an internationally circulated sealed cell of commercial oxygen show its temperature to be 0.581 mK higher than those of the ultra-pure oxygen.

ChemInform Abstract: Isothermal DSC Study of the Thermal Decomposition of Potassium Permanganate

Chemischer InformationsdienstVolume 16, Issue 44 Physical Inorganic Chemistry ChemInform Abstract: Isothermal DSC Study of the Thermal Decomposition of Potassium Permanganate M. E. BROWN, M. E. BROWNSearch for more papers by this authorK. C. SOLE, K. C. SOLESearch for more papers by this authorM. W. BECK, M. W. BECKSearch for more papers by this author M. E. BROWN, M. E. BROWNSearch for more papers by this authorK. C. SOLE, K. C. SOLESearch for more papers by this authorM. W. BECK, M. W. BECKSearch for more papers by this author First published: November 5, 1985 https://doi.org/10.1002/chin.198544031Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume16, Issue44November 5, 1985 RelatedInformation

Thermal decomposition of potassium permanganate: Thermogravimetry, differential scanning calorimetry and hot-stage microscopy studies

Thermogravimetry (TG), differential scanning calorimetry (d.s.c.), and hot-stage microscopy (HSM) techniques have been applied in a study of the thermal decomposition of potassium permanganate. Single crystals of potassium permanganate and ground samples are studied at heating rates from 0.62 to 10 °C min −1, and results compared with previous isothermal studies. Comparison of theoretical and experimental weight loss is made, for both forms of potassium permangante, and a possible mechanism based on diffusion chain theory and nucleation suggested.

The catalytic effect of additions on the rate of thermal decomposition of permanganates

The catalytic effect of additions on the rate of thermal decomposition of potassium permanganate (KMnO 4) were investigated using TG in an atmosphere of air. The additives used were potassium manganate (K 2MnO 4), potassium hypomanganate (K 3MnO 4), the phase “K 4Mn 7O 16”, manganese dioxide (MnO 2), zinc oxide (ZnO) and cuprous oxide (Cu 2O). The crystals of KMnO 4 were found to produce an S-type α— t plot, capable of analysis using a Prout and Tompkins type equation, with an initial acceleratory period being replaced by a deceleratory period over half of the decomposition. The addition of MnO 2 to the system is simply to eliminate the acceleration period and produce a process whereby the rate is deceleratory throughout. The phase “K 4Mn 7O 16” had a similar effect. The manganate and manganate—permanganate compounds are clearly demonstrated to have a negative catalytic effect upon the acceleratory period. The introduction of a solid phase oxide to the system was to decrease the effect of the initial slow acceleratory reaction with an increase in the overall importance of the deceleratory process. These oxides do not eliminate the initial slow acceleratory periods, but all produce their catalytic effect on the deceleratory rate process. An additional study regarded the effect of UV light on the decomposition of AgMnO 4 and KMnO 4. The Prout and Tompkins and Avrami—Erofeev equations were applied to the AgMnO 4 α— t data. The change in the values of the rate constants were observed to be fractionally increased in the decay region. However, the difference in the rate constants seemed to be insufficient to suggest that the UV had any effect on the kinetics. In the case of KMnO 4, however, irradiation with UV almost doubled the rate. At 110°C photodecomposition proceeds by successive absorption of two photons by a permanganate ion followed by thermal ionization. Above 200°C there is appreciable ionization of MnO − 4 in the absence of UV, however, when UV is incident some MnO − 4 ions are optically excited, resulting in an internal electronic transition promoting an electron to a level below that of the conduction band. From this level it is promoted thermally into the conduction band.

Effect of metal oxide additives on the thermal decomposition of KMnO 4

The study of the thermal decomposition of potassium permanganate in air has been studied using DTA, TG and isothermal decomposition between 150 and 400°C. Rate constants were evaluated and found to be affected by the presence of foreign ions. Oxides such as Fe 2O 3 and Cr 2O 3 resulted in a lowering of the decomposition temperature. The modified catalytic mechanisms were proposed by considering the electron transfer and the oxygen-abstraction models.

On the question of the existence of K 3(MnO 4) 2 as an intermediate phase in the thermal decomposition of potassium permanganate

On the question of the existence of K 3(MnO 4) 2 as an intermediate phase in the thermal decomposition of potassium permanganate

Mechanism of thermal decomposition of potassium permanganate in the solid phase

This study of the mechanism of thermal decomposition of potassium permanganate illustrates the possibility of applying the methods and conceptions of solid-state physics in solving problems related to the investigation of chemical reactions in solids. It was found that the elementary stages of the thermal decomposition of permanganate, which is a semiconductor of the n-type, are associated with electron transition from one anion site to another. This viewpoint provides an explanation for the mechanism of the action of catalysic additives and the influence of the solid products formed in the course of the reaction of thermal decomposition, as well as for the mechanism whereby the rate of thermal decomposition of permanganate is affected by preliminary irradiation. The latter is interpreted as the result of the concurrent catalytic action of manganese dioxide and inhibiting action of manganate formed on thermolysis and radiolysis of permanganate. The physical processes occurring during the chemical reactions under investigation are discussed.

A constant temperature reaction vessel for the thermal decomposition of solids

Describes an apparatus suitable for studying the thermal decomposition of potassium permanganate in high vacuum.

Effects of recrystallization and storage on the thermal decomposition of potassium permanganate

Effects of recrystallization and storage on the thermal decomposition of potassium permanganate

Studies on the Reaction in Solid States. XII. Kinetics of the Thermal Decomposition of Potassium Permanganate

前報の相変化の理論を検討するために,種々の粒度の過マンガン酸カリウムの熱分解を定容および定圧で研究した。分解率(α)-時間(t)曲線は,試料粒度により異なり,大粒子試料ではS字形をなすが,小粒子試料ではこのような形を示さない。酸素の圧力は反応に対してなんら影響しないが,分解生成物である二酸化マンガンは反応を促進する。α-t の関係式は試料粒子の粒度により異なり,大粒子および小粒子ではα/1-cr-Pitlriおよび-log(1-α)-Pitl'i,粉末試料では,1-(1-α)1/L'…2pitlriであった。この結果から分解核の数の時間的変化を表わす1,核の成長次元および分解物質と未分解物質との相互作用を示すパラメーターmと試料粒度との間に相関性のあることを認め,さらに実験から得られる核の成長次元は外見的のものであって,核成長の真の状態を小していないものと結論した。活性化エネルギーは試料粒度に関係なく約60kcal/moleであった。