Thermal dissociation of basic aluminium ammonium sulfate in vacuum

Investigations were carried out on the kinetics of thermal decomposition of basic aluminium ammonium sulfate in vacuum. The kinetic model of dissociation of the compound was identified. The results of the kinetic studies and the mechanism of the process are discussed.

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Zusammenfassung Es wurde die Kinetik der thermischen Zersetzung von basischem Ammoniumaluminiumsulfat im Vakuum untersucht. Die Parameter für das kinetische Modell der Dissoziation von der Verbindung wurden identifiziert und die Ergebnisse der kinetischen Untersuchungen im Zusammenhang mit dem Verfahrensmechanismus besprochen.

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Résumé La cinétique de la décomposition thermique sous vide du sulfate basique d'aluminium et d'ammonium a été étudiée. On a identifié les paramètres du modèle cinétique de la dissociation de ce composé. Les résultats des études cinétiques et le mécanisme du processus de décomposition sont discutés.

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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 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 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.     

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 analysis for identification of E-Beam nanosize ammonium sulfate

Summary Thermal decomposition of nanosize ammonium sulfate obtained as a by-product in a new electron-beam technology cleaning up waste gases from thermal power stations was studied. DTA-TG-DTG curves were used to characterize thermal properties of the new products obtained under different technological conditions. High quality of ammonium sulfate from Merck was used as a reference material. Ammonium sulfate was the main component in all the products and their thermal behavior was similar to that of the reference. Only the solid product obtained with the highest norm of ammonia contained about 3.2% ammonium nitrate. Thermoanalytical methods can successfully be applied for control the quality of the by-products from E-beam desulfurization technology. It was found that the thermal stability of the nanosize ammonium sulfate was the same as that of the reference ammonium sulfate.     

Investigation of rate of thermal dissociation of basic aluminium potassium sulphate in hydrogen atmosphere

The rate of release of sulphur oxides from basic aluminium potassium sulphate was studied in a hydrogen atmosphere under isothermal-isobaric conditions, and the kinetic parameters of the process were determined by the statistical criteria method.

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Zusammenfassung Es wurde in Wasserstoff unter isothermen-isobaren Bedingungen die Geschwindigkeit der Freisetzung von in basischem Aluminium-kaliumsulfat in Form von Aluminiumsulfat gebundenen Schwefeloxiden untersucht und die kinetischen Größen dieses Prozesses bestimmt.

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The author would like to express her thanks to Professor J. Pysiak for valuable discussions.     

Thermal analysis of mechanoactivated mixtures of tunisia phosphorite and ammonium sulfate

The thermal behavior of Tunisia phosphorite and ammonium sulfate mixtures are examined by non-isothermal thermogravimetry in air atmosphere. It has been shown that the thermal stability of mixtures have different behavior after mechano-chemical treatment due to phase changes in the mixtures. New solid phases are confirmed by the stages and rate of mass changes and also by the heat effects observed. New phases are also confirmed by using X-ray diffraction method. Based on the data obtained by the mechanism of chemical transformations is proposed. The kinetics of mechano-activated mixtures decomposition is significantly influenced by the time of treatment and proceeds in few stages. Stage I is attributed to the effect of partially ammonia releasing, when the next stages are associated with the decomposition of apatite structures. Because of the interfacial interactions during mechano-chemical treatment insoluble phosphorous forms from apatite structures are transformed to the soluble forms suitable for plants nutrition. The results have shown that the soluble form can be controlled by the initial components ratio and conditions of treatment on the way to obtain slow releasing nutrition products. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of basic aluminium-ammonium sulfate (BAAS) in hydrogen atmosphere

The stages of thermal decomposition of basic aluminium-ammonium sulfate (BAAS) in hydrogen atmosphere were studied with use of differential thermal analysis (DTA), thermogravimetric (TG), X-ray diffraction phase analysis (XRD), and chemical analyses. It has been found that hydrogen greatly influences the process of the desulfurization of the investigated compound: this process occurs at lower temperatures as compared to the desulfurization process in air. The final decomposition product of the basic salt at 1223 K is-Al₂O₃. The experimental part is preceded by the thermodynamic analysis of the desulfurization process of BAAS in hydrogen atmosphere, and its results have been correlated with experimental tests.

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Zusammenfassung Die Stufen der thermischen Zersetzung von basischem Aluminium Ammonium Sulfat (BAAS) in WasserstoffatmosphÄre wurden unter Verwendung von Differenzthermoanalyse (DTA), Thermogravimetrie (TG), röntgenographischer Phasenanalytik (XRD) und chemischer Analytik untersucht. Es wurde festgestellt, dass Wasserstoff den Desulfurierungsprozess der untersuchten Verbindung stark beeinflusst, indem dieser bei tieferer Temperatur ablÄuft als die Desulfurierung in Luft. Das Endprodukt der Zersetzung des basischen Salzes bei 1223 K ist-Al₂O₃. Die experimentellen Resultate wurden mit den Ergebnissen einer vorgÄngig durchgeführten thermodynamischen Betrachtung der Desulfurierung von BAAS in WasserstoffatmosphÄre korreliert.

     

Thermal and FTIR spectral studies of various proportions of zinc magnesium ammonium sulfate

Mixed crystals of various proportions of zinc magnesium ammonium sulfate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized through thermal (TG–DTA) and FTIR spectral analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. DTA curve shows exothermic peaks in this temperature range supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulfate mixed crystals. Detailed structural analysis of the compound is under progress.     

Influence of carbon and water vapour on the thermal dissociation of a basic aluminium-potassium sulfate

The process of obtaining a special aluminium oxide by means of the thermal dissociation of a basic aluminium-potassium sulfate in the presence of carbon (soot) and water vapour was studied. Under these conditions, the dissociation of the basic salt occurs at a lower temperature than in presence of air. K₂O-Al₂O₃ and/or Al₂O₃ are formed as fine-grained reaction residues, depending on the final temperature. The technologically useful range of temperatures for the process was established.

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Zusammenfassung Der Herstellungsprozess eines speziellen Aluminiumoxids durch thermische Zersetzung von basischem Kalium-aluminium-sulfat in Gegenwart von Kohlenstoff (Russ) und Wasserdampf wurde untersucht. Unter diesen Bedingungen verläuft die Zersetzung bei tieferer Temperatur als in Gegenwart von Luft, und K₂O.Al₂O₃ und/oder Al₂O₃ werden als feinkörnige Endprodukte (abhängig von der Endtempeatur) erhalten. Der technologisch günstigste Temperaturbereich für den Prozess wurde ermittelt.

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- () . , . , , ₂l₂₃ l₂₃ . .

     

Thermal decomposition of basic aluminium potassium sulphate. Part I. Stages of decomposition

The stages of thermal decomposition of basic aluminium potassium sulphate were studied with the use of differential thermal analysis (DTA), thermogravimetry (TG), mass spectrometry (MS), IR spectroscopy (IR), and X-ray diffraction phase analysis (XRD). The individual stages of the decomposition were determined and both solid and gaseous products of the dissociation were identified. On the basis of spectrometric data and thermodynamic calculations the possibility of the occurrence of the SO in the gaseous reaction products is discussed.     

Properties of aluminium oxides obtained by calcination of the products of reductive roasting of basic aluminium-potassium sulfate

The influence of calcination conditions on changes in phase composition and porous structure was studied for hydrous aluminium oxide, obtained by leaching out potassium salts from the products of roasting basic aluminium-potassium sulfate in hydrogen atmosphere at 600°C. The product of calcination at 350°C in vacuum has the most developed porous structure with most pores of internal radius within 10–60 Å. Calcination in air atmosphere at temperatures 700, 800, 900, or 1000°C resulted in decrease of specific surface of aluminium oxide and increase of the share of pores with internal radius above 60 Å in the overall porosity of the samples. The reconstruction of the porous structure proceeds mainly as a result of coalescent sintering.     

The thermal decomposition of aluminium sulfate

The mechanism of thermal decomposition of aluminum sulfate has been investigated in the 500–700°C temperature range using a flow reactor system with the emitted gaseous sulfur oxides collected in a Goksøyr—Ross coil and a hydrogen peroxide impinger. Sulfur trioxide (SO₃) was found to be the primary sulfur oxide released during thermal decomposition (1).

Less than 3% of the released sulfur oxides were sulfur dioxide (SO₂), indicating that the SO₃ dissociation reaction (2) is slow relative to the residence time of the SO₃ in the reactor (～ 1 sec).

The experimental technique should be readily adaptable to the study of the thermal decomposition of other metal sulfates.     

Reaction of ammonium sulphate with aluminium oxide

The reaction between ammonium sulphate with aluminium oxide was studied. It was confirmed by X-ray diffraction and chemical analysis that three intermediate reaction products, (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃, are formed. The thermal decompositions of these three compounds were carried out. It has been shown that the same rate law is valid for them. The activation energies for (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃ are 95.9, 177.9 and 291.0 kj/mol, respectively.

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Zusammenfassung Die Reaktion von Ammoniumsulfat mit Aluminiumoxid wurde untersucht. Durch Röntgendiffraktion und chemische Analyse wurde bestätigt, daß drei Zwischenprodukte (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ und Al₂(SO₄)₃ gebildet werden. Die thermische Zersetzung der drei Verbindungen wurde durchgeführt. Es wurde gezeigt, daß für alle drei dasselbe Geschwindigkeitsgesetz Gültigkeit hat. Die Aktivierungsenergien für (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ und Al₂(SO₄)₃ sind 95.9, 177.9 und 291.0 kJ/Mol.

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. - : (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ Al₂(SO₄)₃. , , . (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ Al₂(SO₄)₃, , 95.9; 177.9 291.0 . ^–1.

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The authors are grateful to Dr. H. Osada and Mr. H. Nakamura, Department of Environmental Engineering, Kyushu Institute of Technology, for their helpful discussions.     

Thermal dissociation of SmMnO3

The phase equilibria for the reduction of SmMnO₃ with hydrogen were studied by the static method using a circulation vacuum setup in conjunction with XRD analysis of quenched solid phases. It was established that, over a temperature range of 973–1123 K and a pressure range of 10^?10–10^?16 Pa, SmMnO₃ dissociates by the reaction (1/2)Sm₂O₃ + MnO + (1/4)O₂; in this case, the temperature dependence of the equilibrium oxygen pressure and the Gibbs energy change can be described by the equations log $p_{O_2 } $ [Pa] = 25.35 ? 39150/T ± 0.1, ΔG°_T, kJ/mol = 187.62 ? 0.09T ± 1.62, respectively. Based on the experimental data, the standard thermodynamic functions of formation of SmMnO₃ from elements were calculated: ΔH°_T = ?1485.706 kJ/mol and ΔS°_T = 244.39 J/(mol K).     

Electron detachment dissociation of dermatan sulfate oligosaccharides

The structural characterization of glycosaminoglycans (GAG) oligosaccharides has been a long-standing challenge in the field of mass spectrometry. In this work, we present the application of electron detachment dissociation (EDD) Fourier transform mass spectrometry to the analysis of dermatan sulfate (DS) oligosaccharides up to 10 residues long. The EDD mass spectra of DS oligosaccharides were compared with their infrared multiphoton dissociation (IRMPD) mass spectra. EDD produces more abundant fragmentation than IRMPD with far less loss of SO3 from labile sulfate modifications. EDD cleaves all glycosidic bonds, yielding both conventional glycosidic bond fragmentation as well as satellite peaks resulting from the additional loss of 1 or 2 hydrogen atoms. EDD also yields more cross-ring fragmentation than IRMPD. For EDD, abundant cross-ring fragmentation in the form of A- and X-ions is observed, with 1,5Xn cleavages occurring for all IdoA residues and many of the GalNAc4S residues, except at the reducing and nonreducing ends. In contrast, IRMPD produces only A-type cross-ring fragmentation for long oligosaccharides (dp6-dp10). As all the structurally informative fragment ions observed by IRMPD appear as a subset of the peaks found in the EDD mass spectrum, EDD shows great potential for the characterization of GAG oligosaccharides using a single tandem mass spectrometry experiment.     

Thermal dissociation of crystalline substances

Processing of the reference data shows that the temperature dependences of the equilibrium dissociation pressure of crystalline substances of different classes under the studied and unstudied conditions can be described by equations of similar form. Similar semiempirical temperature dependences of the heat of formation of 1 mol of gaseous products were obtained after bringing the thermal dissociation constants of crystalline substances to consistency.     

Thermal dissociation of diatomic molecules

The establishment of equilibrium in the chemical reaction X₂+M 2X+M is examined. All possible transitions between the vibrational levels and the continuous spectrum are considered. Taking account of two relaxation times, an expression is obtained for the concentration of the X atoms and the chemical reaction rate as a function of time. The conditions under which the dependence of the chemical reaction rate on time acquires an exponential nature are determined. An expression free from the requirement that the initial concentrations of X-atoms and X₂ molecules should be close to their equilibrium values is obtained for the rate constant.In conclusion, the authors thank Prof. N. D. Sokolov for discussion of the work.