Thermal dissociation of basic aluminium-ammonium sulfate in an atmosphere of hydrogen and carbon monoxide

A study was made of the effect of an atmosphere of H₂+CO (a 3∶1 molar mixture) on the mechanism and the kinetics of desulfuration of basic aluminium-ammonium sulfate under variable pressures of hydrogen and carbon monoxide. The temperature region of the process, the nature of almost all the solid intermediates, and the equations and kinetic parameters relating to the rate of desulfurization of the compound for α<0.6 were determined. Despite the complexity of the process, the results permitted determination of the temperature and the composition of the gas phase necessary for the process of desulfuration to occur and for aluminium oxides with the required properties to be obtained.     

Physicochemical properties of the products of basic aluminium-potassium sulfate decomposition in hydrogen atmosphere

Low-temperature modifications of aluminium oxide were obtained by thermal decomposition of basic aluminium-potassium sulfate at temperatures 550, 600, and 650°C. Physicochemical properties of the obtained oxides were studied with particular consideration to phase composition and porous structure. It has been shown how the decomposition parameters of the basic salt used determine the porous structure of the obtained oxides.

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Zusammenfassung Durch thermische Zersetzung von basischem Aluminiumkaliumsulfat bei Temperaturen von 550, 600 und 650°C wurden Niedrigtemperaturmodifizierungen von Aluminiumoxid hergestellt. Die physikochemischen Eigenschaften der erhaltenen Oxide wurden in besonderer Hinsicht auf Phasenzusammensetzung und Porenstruktur untersucht. Es wurde gezeigt, wie die Parameter der Zersetzung des eingesetzten basischen Salzes die Porenstruktur der erhaltenen Oxide beeinflussen.

     

Thermal decomposition of basic zinc carbonate in nitrogen atmosphere

Dynamic kinetic analyses were performed on basic zinc carbonate using TG and DTA measurements in N₂. The thermal behavior and the kinetics of decomposition were studied. The effect of procedural variables on the kinetics was investigated. In this work, the procedural variables included heating rate and sample size. To estimate the activation energy of decomposition, the Friedman isoconversional method was applied. The activation energy (E_a) was calculated as a function of conversion (a).     

Thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere

The conditions of thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere at heating rates of 10 and 5 deg·min^–1 were studied. At 10 deg · min^–1, the hemimellitate and trimesinate of copper(II) lose crystallization water and then decompose directly to CuO, whereas at 5 deg·min^–1 they decompose to CuO through Cu₂O. The trimellitate of copper(II) heated at various rates decomposes in the same way: it loses 1 water molecule and then decomposes directly to CuO.     

Thermal decomposition of thorium(IV) benzenedicarboxylates in air atmosphere

The conditions of thermal decomposition of Th(IV) benzenedicarboxylates have been studied. On heating, thorium(IV) phthalate and isophthalate are dehydrated and the anhydrous complexes decompose to ThO₂ with intermediate formation of a mixture of ThOCO₃ and carbon.Th(IV) terephthalate obtained at room temperature loses crystal water and then decomposes directly to ThO₂, while the complex isolated from a hot solution on heating is first dehydrated, and the anhydrous complex is decarboxylated and then decomposed to ThO₂ with the intermediate formation of ThOCO₃.The activation energies of dehydration have been calculated for the Th(IV) benzenedicarboxylates.

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Zusammenfassung Die Bedingungen der thermischen Zersetzung von Th(IV)-benzendicarboxylaten wurde untersucht. Thorium(IV)-phthalat und- isophthalat werden beim Erhitzen zunÄchst dehydratisiert, danach zersetzen sich die wasserfreien Komplexe über ein intermediÄr auftretendes Gemisch von ThOCO₃ und Kohlenstoff zu ThO₂. Bei Raumtemperatur erhaltenes Th(IV)-terephthalat verliert Wasser und zersetzt sich dann direkt zu ThO₂, wÄhrend der aus einer hei\en Lösung isolierte Komplex nach der als erster Schritt verlaufenden Dehydratisierung zunÄchst decarboxyliert wird und sich dann über ThOCO₃ als Zwischenprodukt zu ThO₂ zersetzt. Die Aktivierungsenergien der Dehydratisierung der Th(IV)-benzendicarboxylate wurden berechnet.

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. , ThO₂ ThOCO₃ . , , , ThO₂. , , , , H₂ ThOCO₃ . .

     

Kinetics of thermal dissociation of basic aluminium ammonium sulfate in a hydrogen atmosphere

The rate of release of sulfur oxides from basic aluminium ammonium sulfate (BAAS) under isothermal, isobaric conditions in a hydrogen atmosphere was studied.Twomethods of selection of theg() function which best describes the isothermal experimental data are discussed.The first method is based on statistical criteria and the second one on the the use of a reduced-time scale. Kinetic parameters for the thermal decomposition of BAAS in a hydrogen atmosphere are reported.

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Zusammenfassung Unter isothermen, isobaren Bedingungen wurde die Geschwindigkeit der Freisetzung von Schwefeloxiden aus basischem Aluminiumammoniumsulfat (BAAS) untersucht.Es werden zwei Verfahren zur Auswahl derjenigeng()-Funktion diskutiert, die die isothermen Ergebnisse am besten wiedergibt.Das erste Verfahren beruht auf statistischen Kriterien, dem zweiten lag eine reduzierte-Zeitskala zugrunde. Kinetische Parameter für die thermische Zersetzung von BAAS in Wasserstoff werden beschrieben.

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Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60^th birthday     

Thermal decomposition of oxalates. Part 17. Thermal decomposition of manganese(II) oxalate in a nitrogen atmosphere

Comparative studies of the kinetics of the isothermal and nonisothermal dehydration and decomposition of manganese(II) oxalate in an atmosphere of nitrogen are reported. Agreement between the values of the energy of activation for the isothermal and the nonisothermal dehydration at high heating rates was obtained. At low heating rate, the value obtained for the energy of activation is comparable with the enthalpy of dehydration. Values of 143 and 242 kJ mole^?1 were obtained for the energy of activation of the isothermal and nonisothermal decomposition, respectively. The difference is attributed to the condition of the anhydrous salt used in both cases. The theory of absolute reaction rate is applied and the parameters obtained are discussed.     

Thermal decomposition of some silver(I) carboxylates under nitrogen atmosphere

The thermal decomposition reactions of CH₃CH₂C(CH₃)₂COOAg (1), (CH₃)₃SiCH₂COOAg (2), CF₃COOAg (3), (CH₃)₃CCOOAg (4), C₂H₅COOAg (5), C₃F₇COOAg (6), C₆F₁₃COOAg (7) and (CF₂)₃(COOAg)₂ (8) were studied in N₂ atmosphere using thermogravimetry (TG), derivative thermogravimetry and differential thermal analysis. Characterized compounds decomposed in one- or multi-step processes with metallic silver formation in the range 215–465 °C. TG-IR studies of gases evolved during thermolysis revealed products of decomposition, such as carboxylic acids, CO₂ and recombination reactions.     

Thermal decomposition of thorium(IV) complexes with benzenecarboxylic acids in air atmosphere

The conditions and products of thermal decomposition of thorium(IV) complexes with general formula Th(R-C₆H₄COO)₄ (whereR=2-CH₃, 3-CH₃, 4-CH₃), Th(OH)₂(4-CH₃C₆H₄COO)₂. H₂O and Th(OH)₂(R-C₆H₄COO)₂·nH₂O (whereR=2-COO, 3-COO,n=2;R=4-COO,n=1) were studied. Anhydrous thorium(IV) complexes decompose in two steps. On heating, tetra(2-methylbenzoato)-thorium(IV) decomposes to yield ThO₂ through the intermediate ThOCO₃ whereas tetra(3-methylbenzoato)thorium(IV) and tetra(4-methylbenzoato)thorium(IV) decompose to ThO₂ through oxocomplexes. Hydrated thorium(IV) complexes are dehydrated in one step and then anhydrous complexes decompose to ThO₂. Di [1,2-(benzene)dicarboxylato]dihydroxythorium(IV) decomposes directly to ThO₂, whereas the 1,3- and 1,4-isomers through the intermediate thorium(IV) oxocarbonates.     

Thermal decomposition of thorium(IV) salts of benzene carboxylic acids in air atmosphere

The thermal stabilities of thorium(IV) salts of ortho-, meta- and para-hydroxy- and aminobenzoic acids were studied. The salts were prepared as hydrated compounds with general formula Th(OH)₂(R-C₆H₄COO)₂·nH₂O, wereR = OH or NH₂, andn = 2, 3 or 4, while the salt of 3-aminobenzoic acid was anhydrous. On heating, the salts undergo dehydration in two or three steps and di(R-benzoato)dihydroxothorium(IV) or di(2-hyroxybenzoato)oxothorium(IV) is then transformed directly to ThO₂.The temperatures of beginning of decomposition and ThO₂ formation decrease with decreasing values of the Hammett constant and von Bakkum constant ⁿ.

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Zusammenfassung Es wurde die Thermostabilität der Thorium(IV)-salze von ortho-, meta- und para-Hydroxy- und Aminobenzoylsäure untersucht.Die Salze wurden als hydratierte Verbindungen der allgemeinen Formel Th(OH)₂(R-C₆H₄COO)₂·nH₂O mitR=OH oder NH₂ undn=2,3 oder 4 gefertigt, während das Salz der 3-Aminobenzoylsäure unhydratiert war. Beim Erhitzen zeigen die Salze eine Dehydratation in zwei oder drei Stufen und anschließend werden Di(R-benzoato)dihydroxothorium(IV) oder Di(2-hydroxybenzoato)oxothorium(IV) direkt in ThO₂ umgewandelt.Die Temperaturen für das Einsetzen der Zersetzung und der ThO₂-Bildung sinken mit abnehmenden Werten für die Hammet-Konstante und die Bakkum-Konstante

     

Thermal decomposition of rare earthp-aminosalicylates in air atmosphere

The conditions of thermal decomposition of thep-aminosalicylates of Y, La and the lanthanides from Ce(III) to Lu have been studied. On heating, the hydrated complexes of La and the light lanthanides decompose to the oxides with the intermediate formation of Ln₂[H₂N·C₆H₃(O)COO]₃. Only the complex of La decomposes to La₂O₃ through La₂[H₂N·C₆H₃(O)COO]₃ and La₂O₂CO₃. The anhydrous complexes of the heavy lanthanides decompose directly to the oxides, whereas the anhydrous complex of Y decomposes to Y₂O₃ via Y₂[H₂N·C₆H₃(O)COO]₃ formation. During heating, the hydrated complexes lose crystallization water and decompose simultaneously, and the endothermic effect of dehydration is masked by the strong exothermic effect of burning of the organic ligand.

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Zusammenfassung Es wurden die Bedingungen für die thermische Zersetzung derp-Aminosalicylate von Y, La und der Lanthanoide von Ce(III) bis Lu untersucht. Beim Erhitzen zersetzen sich die hydratierten Komplexe von La und der leichteren Lanthanoide unter Bildung des Zwischenproduktes Ln₂[H₂NC₆H₃(O)COO]₃ in ihre Oxide. Nur der Komplex mit La zersetzt sich zu La₂O₃ über die Zwischenstufen La₂[H₂NC₆H₃(O)COO]₃ und La₂O₂CO₃. Die wasserfreien Komplexe der schweren Lanthanoide zersetzen sich direkt in die Oxide, wÄhrend sich der wasserfreie Komplex von Y über die Bildung von y₂[H₂NC₆H₃(O)COO]₃ in y₂O₃ zersetzt. Beim Erhitzen verlieren die hydratierten Komplexe ihr Kristallwasser und zersetzen sich gleichzeitig, der endotherme Effekt der Dehydratation wird durch den starken exothermen Effekt der Verbrennung der organischen Liganden überdeckt.

     

Thermal decomposition of basic lead carbonate

TG and DTA curves of the thermal decomposition of basic lead carbonate, 2PbCO₃ Pb(OH)₂, are presented and compared with the thermogram of normal lead carbonate PbCO₃. The appearance of different intermediate compounds at identical experimental conditions is ascribed to the degree of perfection of the carbonate crystals. Poorly developed basic lead carbonate crystals, formed in the presence of polyglutamic acid, give no recognizable intermediate compounds.     

Thermal decomposition of basic aluminium potassium sulfate. Part II. Kinetics of the reaction

The kinetics of individual stages of thermal dissociation of basic aluminium potassium sulfate (BAPS) were studied thermogravimetrically under isobaric and isothermal conditions at a reduced pressure of the order of 10^?3 hPa and in the atmosphere of gaseous products of the reaction (H₂O, SO₂).The kinetic parameters of all the reaction stages have been identified and the nature of the stages and the effect of changes of the reaction of conditions on the course of the processes have been determined.     

Thermal decomposition kinetics of aluminum sulfate hydrate

The kinetics of individual stages of thermal decomposition of Al₂(SO₄)₃·18H₂O were studied by TG method. It is found that Al₂(SO₄)₃·18H₂O decomposes to Al₂O₃ in four major stages, all of endothermic. Some of these major stages are formed by sub-stages. The first three major stages are dehydration reactions in which two, ten and six moles water are lost, respectively. The last major stage is sulfate decomposition. In this study the kinetic parameter values of these major and sub-stages were calculated by integral and differential methods. The alterations of activation energies with respect to the decomposition ratio and to the method were investigated.     

Thermal decomposition of hydroxylammonium neodymium sulfate dihydrate

The thermal decomposition of hydroxylammonium neodymium sulfate dihydrate has been investigated by simultaneous thermogravimetry and differential thermal analysis. Chemical analysis, X-ray powder spectra and infrared spectroscopy have been employed to characterize the intermediates and the final product. The thermal decomposition can be described by the sequence (NH₃OH)Nd(SO₄)₂·2H₂O(NH₃OH)Nd(SO₄)₂ NH₄Nd₃(SO₄)₅Nd₂(SO₄)3. The first and the second reactions overlap, but the last one is well separated from the first two.     

Thermal decomposition of rare earth salicylates in air atmosphere

The conditions of decomposition of Y, La and lanthanide (from Ce(III) to Lu) salicylates have been studied. On heating, the hydrated salicylates of Y and lanthanides from Nd to Lu lose crystallization water in one step to yield the anhydrous salts. The anhydrous complexes of Y, La, Ce(III), Pr, Nd, Sm, Eu(III), Gd and Tb subsequently decompose in several steps to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The anhydrous complexes of the remaining lanthanides decompose directly to the oxides Ln₂O₃.

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Zusammenfassung Die Zersetzungsreaktionsbedingungen von Y-, La- und Lanthanid-(Ce(III) bis Lu) salizylaten wurden untersucht. Beim Erhitzen geben hydrierte Salizylate von Y und der Lanthanide Nd bis Lu Kristallwasser in einem Schritt ab und bilden wasserfreie Salze. Die wasserfreien Komplexe von Y, La, Ce(III), Pr, Nd, Sm, Eu(III), Gd und Tb zersetzen sich in mehreren Schritten und bilden die Oxide Ln₂O₃, CeO₂, Pr₆O₁₁ und Tb₄O₇. Die wasserfreien Komplexe der übrigen Lanthaniden zerfallen direkt in Ln₂O₃ Oxide.

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, . , . , , , , , , , , Ln₂O₃, CeO₂, Pr₆O_{11 47}. Ln₂O₃.

     

Thermal decomposition of rare earth pyromucates in air atmosphere

The conditions of thermal decomposition of Y, La and lanthanide (from Ce(III) to Lu) pyromucates have been studied. On heating, these complexes decompose in various ways: La, Pr, Nd and Sm pyromucates in four stages, Ce, Eu, Gd, Dy, Ho and Er pyromucates in three stages, and Tm, Yb, Lu and Y pyromucates in two stages, the oxides finally being formed. The hydrated complexes (from La to Er) lose crystallization water to form anhydrous salts. The anhydrous complexes of La, Pr, Nd and Sm decompose to oxides through the intermediate formation of unstable oxypyromucates and Ln₂O₂CO₃, whereas the anhydrous complexes of Ce(III), Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu decompose to the oxides through the intermediate formation of oxypyromucates. The temperatures of dehydration and oxide formation change periodically with increasing atomic number in the lanthanide series.

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Zusammenfassung Die Bedingungen der thermischen Zersetzung der Pyromucate von Y, La und den Lanthaniden (Ce(III) bis Lu) wurden untersucht. Beim Erhitzen zersetzen sich die Komplexe auf verschiedene Weise: die Pyromucate von La, Pr, Nd und Sm in 4 Schritten, die von Ce, Eu, Gd, Dy, Hod Er in 3 Schritten und die von Tm, Yb, Lu und Y in nur 2 Schritten. Endprodukte der Zersetzung sind die Oxide, Die hydratisierten Komplexe von La bis Er verlieren Kristallwasser unter Bildung der wasserfreien Salze. Die wasserfreien Komplexe von La, Pr, Nd und Sm zersetzen sich zu Oxiden über instabile Oxypyromucate und Ln₂O₂CO₃ als Zwischenprodukte, bei der Zersetzung der wasserfreien Komplexe von Ce(III), Eu, Gd, Dy, Ho, Er, Tm, Yb und Lu werden Oxypyromucate als Zwischenprodukte gebildet. Die Temperaturen der Dehydratisierung und Oxidbildung schwanken periodisch mit ansteigender Atomzahl in der Lanthanidenreihe.

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, ( ) . : , , , , , , , — , , , — . , . , , Ln₂O₂CO₃. . .

     

Thermal decomposition of basic aluminium potassium sulfate. Part III. General regularities of thermal dissociation

Using the method of Bolles and Drago (1) the thermodynamic properties of drug - aromatic amino acid complexes were determined calorimetrically. The comparison of K_c evaluated from vapour pressure osmometry. ORD, partition and calorimetry shows a considerable agreement, whereas the data calculated from solubility measurements differ widely from our results. Qualitatively the relationship between solubilisation through different salts and ΔG⁰ for the complexation with the same salts could be demonstrated. Methylxanthines form complexes with anions and cations, the complex formation in H₂O and D₂O, determined calorimetrically, shows the greater stability of the complexes in D₂O.     

Thermal decomposition of Prussian blue under inert atmosphere

The thermal decomposition of Prussian blue (iron(III) hexacyanoferrate) under inert atmosphere of argon was monitored by thermal analysis from room temperature up to 1000?°C. X-ray powder diffraction and ⁵⁷Fe M?ssbauer spectroscopy were the techniques used for phase identification before and after sample heating. The decomposition reaction is based on a successive release of cyanide groups from the Prussian blue structure. Three principal stages were observed including dehydration, change of crystal structure of Prussian blue, and its decomposition. At 400?°C, a monoclinic Prussian blue analogue was identified, while at higher temperatures the formation of various polymorphs of iron carbides was observed, including an orthorhombic Fe₂C. Increase in the temperature above 700?°C induced decomposition of primarily formed Fe₇C₃ and Fe₂C iron carbides into cementite, metallic iron, and graphite. The overall decomposition reaction can be expressed as follows: Fe₄[Fe(CN)₆]₃·4H₂O????4Fe?+?Fe₃C?+?7C?+?5(CN)₂?+?4N₂?+?4H₂O.