Thermal decomposition of heavy lanthanide 3-hydroxybenzoates in air and nitrogen atmospheres

The conditions of thermal decomposition of heavy lathanide complexes with 3-hydroxybenzoic acid in air and nitrogen atmospheres have been studied. On heating, the complexes of Gd, Dy, Ho, Yb and Lu decompose in three stages. First, the hydrated complexes lose crystallization water and the anhydrous salts heated in air are then transformed to Ln₂O₃, or in a nitrogen atmosphere to Ln₂O₃ and C. Complexes of Tb(III), Ho and Er are dehydrated in two stages during heating, and the anhydrous complexes are converted in air to Ln₂O₃ and Tb₄O₇, and in a nitrogen atmosphere to a mixture of oxides and C. The carbon content in the decomposition product ranges between 9.7% for Gd and 19.6% for Ho.The dehydration of the complexes is accompanied by endothermic effects. The decomposition of 3-hydroxybenzoates is exothermic in air and endothermic in nitrogen.

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Zusammenfassung Die Bedingungen der thermischen Zersetzung von Komplexen der schweren Lanthanide mit 3-Hydroxybensoesäure in Luft und Stickstoffatmosphäre wurden untersucht. Beim Erhitzen zersetzen sich die Komplexe von Gd, Dy, Ho, Yb und Li in drei Schritten. Zuerst verlieren die hydratisierten Komplexe Kristallwasser, die wasserfreien Salze ergeben dann in Luft Ln₂O₃ und in Stickstoffatmosphäre Ln₂O₃ und C als festen Rückstand. Komplexe von Tb(III), Ho und Er werden während des Erhitzens in zwei Stufen dehydratisiert und ergeben bei höheren Temperaturen in Luft Ln₂O₃ bzw. Tb₄O₇ und in Stickstoffatmosphäre eine Mischung der Oxide mit Kohlenstoff als festen Rückstand. Der Kohlenstoffgehalt des Zersetzungsproduktes liegt zwischen 9.7% für Gd und 19.6% für Ho. Die Dehydratisierung der Komplexe geht mit endothermen Effekten einher. Die Zersetzung von 3-Hydroxybenzoaten ist exotherm in Luft und endotherm in Stickstoffatmosphäre.

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3- . , , , , . , , — . , , — . , 9.7 19.6%. . 3- , — .

     

Thermal decompositions of Y,La and light lanthanide thiodiglycolates

The conditions of thermal decomposition of the thiodiglycolates of Y, La and light lanthanides from Ce to Gd have been studied. On heating, these complexes decompose in various ways. Hydrated thiodiglycolates of La,Ce(III), Pr(III) and Gd lose crystallization water in one step, while those of Y, Nd, Sm and Eu(III) do so in two steps. The anhydrous complexes subsequently decompose in several steps to the oxysulfates Ln₂O_3–x((SO₄)_x.

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Zusammenfassung Bedingungen der thermischen Zersetzung der Thiodiglycolate von Y, La und den leichten Lanthaniden von Ce bis Gd wurden untersucht. Beim Erhitzen zersetzen sich diese Komplexe auf verschiedene Weise. Hydratisierte Thiodiglycolate von La, Ce(III), Pr(III) und Gd verlieren das Kristallwasser in einem Schritt, die von Y, Nd, Sm, und Eu(III) dagegen in zwei Schritten. Die wasserfreien Komplexe zersetzen sich in mehreren Schritten zu den Oxysulfaten Ln₂O_3–x(SO₄)_x.

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. . . , , , , , . Ln₂O_3–x(SO₄)_x.

     

Thermal decomposition of Y,La and lanthanide benzene-1,2-dioxyacetates in an air atmosphere

The thermal decompositions of Y, La and lanthanide (from Ce(III) to Lu(III) benzene-1,2-dioxyacetates with general formula Ln₂(C₁₀H₈O₆)₃·nH₂O were studied. The hydrated complexes first lose water of crystallization in one or two steps to yield anhydrous compounds or hydrates containing coordination water molecules, and then decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ with formation of intermediates, carbonates and oxycarbonates (La, Pr-Eu), oxycarbonates (Y, Tb-Lu) or carbonate (Gd) only. Anhydrous cerium(III) benzene-1,2-dioxyacetate decomposes on heating directly to CeO₂.     

Thermal decomposition of Y,La and light lanthanide ferulates

The conditions of thermal decomposition of Y, La and light lanthanide ferulates have been studied. On heating, these complexes decomposed in various ways; lanthanum ferulate in four stages, Ce(III) ferulate in three stages, and the ferulates of Y, Pr(III), Nd, Sm, Eu(III) and Gd in two stages, the oxides finally being formed. The complexes lose crystallization water to form anhydrous or hydrated salts, and are then decomposed directly to oxides. Only lanthanum ferulate decomposes to the oxide with intermediate formation of La₂O₂CO₃. The temperatures of oxide formation change periodically with the decrease in the ionic potential in the lanthanide series.

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Zusammenfassung Es wurden die Bedingungen der Zersetzung der Y-, La- und leichten Lanthanidferulate untersucht. Die erhaltenen Komplexe werden beim Erhitzen auf verschiedene Weise zersetzt. Lanthanferulat wird über vier, Ce(III)-Ferulat über drei und die Ferulate von Y, Pr(III), Nd, Sm, Eu(III) und Gd über zwei Zwischenstufen in das entsprechende Oxid überführt. Aus den Komplexen entstehen zunächst unter Verlust von Kristallwasser wasserfreie oder hydratisierte Salze, die dann direkt zu den Oxiden abgebaut werden. Nur Lanthanferulat wird über eine intermediäre Verbindung des Typs M₂O₂CO₃ zum Oxid abgebaut. Die Bildungstemperaturen der Oxide ändern sich periodisch mit abnehmenden Ionenpotential in der Lanthanidenreihe.

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Y, La . . , — , Y, (III) Nd, Sm,Eu(III) Gd — . , , . L₂₂₃. .

     

Thermal decomposition of Y,La and light lanthanide complexes of hippuric acid

The conditions of thermal decomposition of the hippurates of Y, La and the light lanthanides from Ce(III) to Gd have been studied. When heated, the Y, Ce(III), Pr and Gd complexes decomposed in two stages, those of La, Sm and Eu in three stages, and that of Nd in four stages, the oxides finally being formed. The complexes lost crystallization water to form anhydrous (Nd) or hydrated salts, and then decomposed to oxides directly (Y, Ce(III), Pr(III) and Gd) or with intermediate formation of Ln₂O₂CO₃ (La, Nd, Sm and Eu). The temperature of oxide formation varied periodically with the ionic potential in the lanthanide series.

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Zusammenfassung Die Bedingungen der thermischen Zersetzung der Hippurate von Y, La und der leichten Lanthanide von Ce(III) bis Gd wurden untersucht. Beim Aufheizen zersetzen sich die Komplexe von Y, Ce(III), Pr und Gd in zwei Schritten, die von Sm und Eu in drei Schritten und der von Nd in vier Schritten zu den Oxiden. Die Komplexe verlieren Kristallwasser unter Bildung wasserfreier (Nd) oder hydratisierter Salze und zersetzen sich dann direkt (Y, Ce(III), Pr(III), Gd) oder über Ln₂O₂CO₃ (Ln, Nd, Sm, Eu) zu den Oxiden. Die Temperatur der Oxidbildung verändert sich periodisch mit abnehmenden Ionenpotential in der Lanthanidenreihe.

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

     

Thermal decompositions of heavy lanthanide aconitates

The conditions of thermal decomposition of Tb(III), Dy, Ho, Er, Tm, Yb and Lu aconitates have been studied. On heating, the aconitates of heavy lanthanides lose crystallization water to yield anhydrous salts, which are then transformed into oxides. The aconitate of Tb(III) decomposes in two stages. First, the complex undergoes dehydration to form the anhydrous salt, which next decomposes directly to Tb₄O₇. The aconitates of Dy, Ho, Er, Tm, Yb and Lu decompose in three stages. On heating, the hydrated complexes lose crystallization water, yielding the anhydrous complexes; these subsequently decompose to Ln₂O₃ with intermediate formation of Ln₂O₂CO₃.     

Thermal decompositions of light lanthanide aconitates

The conditions of thermal decomposition of Y, La, Ce(III), Pr, Nd, Sm, and Gd aconitates have been studied. On heating, the aconitate of Ce(III) loses crystallization water to yield anhydrous salt, which then is transformed in to oxide CeO₂. The aconitates of Y, Pr, Nd, Sm, Eu and Gd decompose in three stages. First, aconitates undergo dehydration to form the anhydrous salts, which next decompose to Ln₂O₂CO₃. In the last one the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ is accompanied by endothermic effect. Dehydration of aconitate of La undergoes in two stages. The anhydrous complex decomposes to La₂O₂CO₃; this subsequently decomposes to La₂O₃.     

Thermal decomposition of scandium(III) benzenetricarboxylates in air and nitrogen atmospheres

The conditions of thermal decomposition of scandium(III) hemimellitate, trimellitate and trimezinate in air and nitrogen atmospheres have been studied. On heating, the benzene-tricarboxylates of Sc(III) decompose in two stages. First, the hydrated complexes lose crystallization water; heating in air finally yields Sc₂O₃, and heating in a nitrogen atmosphere Sc₂O₃ and C. The dehydration of the complexes is associated with strong endothermic effects. The decomposition of benzenetricarboxylates in air is accompanied by an exothermic effect and in nitrogen by an endothermic effect. The activation energies of the dehydration and decomposition reactions have been calculated for the Sc(III) benzenetricarboxylates.     

Thermal decompositions of lanthanum and lanthanide salts of sebacic acid

The conditions of thermal decomposition of La, Ce(III), Pr(III), Nd, Sm(III), Eu, Gd, Tb(III), Dy, Ho, Er, Tm, Yb and Lu sebacates have been studied. When heated in air atmosphere, the sebacates of La and lanthanides with general formula Ln₂(C₁₀H₁₆O₄)₃·nH₂O, wheren=6?24, lose some crystallization water molecules in one or two steps at 323–343 K and are then dehydrated and decomposed simultaneously to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The oxides are formed over the range of temperature 783 K (CeO₂)?1073 K (Nd₂O₃).     

Thermal kinetic studies on the decompositions of cefuroxime lysine in different atmospheres and heating rates

The thermal decomposition of a new antibiotic agent, cefuroxime lysine, was investigated by thermogravimetry analysis/derivative thermogravimetry and differential scanning calorimetry (DSC) methods in anoxic and oxidative environments. The influence of heating rates (including 5, 10, 15, and 20 °C/min) on the thermal behavior of cefuroxime lysine was revealed. By the methods of Kissinger and Flynn–Wall–Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.     

Thermal decompositions of scandium(III) m-nitrobenzoate,m-chlorobenzoate,m-hydroxybenzoate and m-aminobenzoate in air atmosphere

The conditions of thermal decomposition of scandium(III) m-nitrobenzoate, m-chlorobenzoate, m-hydroxybenzoate and m-aminobenzoate were studied. On heating, most of these carboxylates decompose in two steps; only scandium(III) 3-aminobenzoate decomposes in one step. The hydrated complexes first lose crystallization water and are then transformed to Sc₂O₃. The hydration of the complexes is accompanied by an endothermic effect, and the decomposition of the anhydrous complexes by a strong exothermic effect. Scandium(III) 3-nitrobenzoate decomposes explosively.     

Thermal decomposition of yttrium,lanthanum and lanthanide complexes of square acid in air atmosphere

The conditions of thermal decomposition of the Y, La and lanthanide complexes of square acid in air atmosphere have been studied. On heating, the complexes of Y, La, Ce(III), Pr(III), Nd, Sm, Eu(III), Gd, Tb(III) and Ho decompose in two steps. First, the hydrated complexes lose crystallization water to form anhydrous salts. The complexes of Dy and Er decompose in three steps; they are dehydrated in two steps to form anhydrous salts. The complexes of Tm, Yb and Lu are dehydrated in three steps; in two steps they lose water molecules to form octahydrates, which in the third step are dehydrated during decomposition. On heating, the anhydrous complexes of Y, Ce(III), Pr(III), Eu(III), Gd, Tb(III), Dy, Ho and Er and the octahydrated salts of Tm, Yb and Lu decompose directly to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The anhydrous complexes of La, Nd and Sm decompose to Ln₂O₃ with intermediate formation of Ln₂O₂CO₃.

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Zusammenfassung Die thermische Zersetzung von Komplexen von Y, La und Lanthaniden mit Squaresäure in Luft wurde untersucht. Beim Erhitzen zerfallen die Komplexe von Y, La, Ce(III), Pr(III), Nd, Sm, Eu(III), Gd, Tb(III) und Ho in zwei Schritten. Die hydrierten Komplexe geben zuerst Wasser ab und bilden wasserfreie Salze. Die Komplexe von Dy und Er zerfallen in drei Schritten, wobei sie in zwei Schritten zu wasserfreien Salzen dehydriert werden. Die Komplexe von Tm, Yb und Lu werden in drei Schritten dehydriert. Sie geben in zwei Schritten einige Wassermoleküle ab, um Octahydrate zu bilden, die dann während des Zerfalles dehydriert werden. Die wasserfreien Komplexe von Y, Ce(III), Pr(III), Eu(III), Gd, Tb(III), Dy, Ho und Er sowie die Octahydratsalze von Tm, Yb, und Lu zerfallen beim Erhitzen direkt zu den Oxiden Ln₂O₃, CeO₂, Pr₆O₁₁ und Tb₄O₇. Die wasserfreien Komplexe von La, Nd und Sm zerfallen über das Zwischenprodukt Ln₂O₂CO₃ zu Ln₂O₃.

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, . , , , , , , , . , . . . , . , , . , , , , , , , , , , Ln₂O₃, CeO₂, Pr₆O₁₁ Tb₄O₇. , Ln₂O₃ Ln₂O₂CO₃.

     

Thermal destruction of rice hull in air and nitrogen

In this study, we ashed rice hull in air and nitrogen, respectively, and systematically investigated the effects of ashing temperature and atmosphere on the structures, morphologies, and pore characteristics of rice hull ash (RHA). All RHA samples are amorphous materials with porous structures. IR spectra revealed that RHA that ashed in air (WRHA) exhibit more polar groups on the surface than that of ashed in nitrogen (BRHA). The silica and carbon contents, BET surface area, and pore volume of BRHA increase with ashing temperature. When ashed in air, however, the silica content of WRHA increases and carbon content decreases with temperature. The BET surface area and pore volume of WRHA increase with temperature firstly and decline subsequently due to the closure of pores. Compared with WRHA, BRHA shows higher surface areas, micropore volumes, carbon contents, and lower mesopore fractions and silica contents. This study provides essential information for choosing a suitable thermal treatment of rice hull for a given adsorbate.     

Thermal degradation of cereal straws in air and nitrogen

Multigram quantities (2.5-10 g) of highly purified IgG were obtained within 4 h from serum by using Avid AL packed in a radial-flow column. Avid AL is an affinity gel containing a synthetic, low-mol-wt ligand capable of selectively binding IgG from serum of all animal species tested. By packing the gel in a radial-flow column up to 500 mL, a high flow rate of 50 mL/min can be achieved without adversely affecting the performance of the gel and the purity of the isolated antibody.     

Thermal degradation and their kinetics of biodegradable poly(butylene succinate-co-butylene terephthate)s under nitrogen and air atmospheres

In this study, thermal degradation and their related kinetics have been investigated mainly by means of thermal gravimetrical analyzer (TGA) under the dynamic nitrogen and air atmospheres for the chemically prepared biodegradable aliphatic-aromatic copolyesters of poly(butylene succinate-co-butylene terephthalate) (PBST). To further shed new lights on the comonomer molar composition and experimental condition dependences of thermal degradation kinetics, the as-known Friedman model was at first applied to quantitatively evaluate the kinetic parameters in terms of activation energy (E), degradation reaction order (n) and the frequency factor (Z). The results clearly demonstrated that thermal stabilities of these PBST copolyesters were substantially enhanced with the incorporation of more rigid butylene terephthalate comonomer, and tended to be much better in nitrogen than in air. Furthermore, the Friedman, Freeman-Carroll and Chang models were concurrently employed to quantitatively evaluate the thermal degradation kinetic parameters of the PBST copolyesters in nitrogen at different heating rates of 1, 2 and 5 K/min. It was found that the thermal degradation kinetic parameters for the PBST copolyesters were strongly dependent on the heating rate and calculating models. In addition, life-time parameters of the biodegradable PBST copolyesters were first calculated to predict the maximum usable temperatures, and this would be useful for practical application of these new bio-based green plastics.     

Thermal decomposition of lanthanum selenate pentahydrate in air and nitrogen

Thermogravimetric studies, supported by IR and X-ray diffraction measurements, were carried out for La₂(SeO₄)₃ · 5H₂O in order to establish its decomposition scheme under various experimental conditions. Several analytical methods were tested for the simultaneous determination of (Se(IV) and Se(VI) in the quenched samples. TG weight losses and analyses of the solid intermediates indicated that after dehydration La₂(SeO₄)₃ decomposes in nitrogen mainly to oxyselenite(IV) compoundsvia the normal selenite(IV) but in air the oxyselenate La₂O₂SeO₄ was detected as one of the intermediates. The final product of the thermal degradation is La₂O₃. TG curves of La₂(SeO₄)₃ · 5H₂O were also compared with those obtained for the isostructural neodymium compound.     

Isoconversional kinetic analysis of thermal decomposition of 1-butyl-3-methylimidazolium hexafluorophosphate under inert nitrogen and oxidative air atmospheres

Journal of Thermal Analysis and Calorimetry - Non-isothermal decomposition of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) in inert nitrogen and air atmospheres was investigated by...     

Comparative study on thermal degradation of some new diazoaminoderivatives under air and nitrogen atmospheres

The article is devoted to a comparative study on the thermal degradation of some new diazoaminoderivatives under both air and nitrogen atmosphere by TG-FTIR analysis. The TG–DTG–DTA curves show the thermal degradation in air to present two temperature domains: an endothermic one identical to the case of the degradation under nitrogen and an exothermic one which is not to be found under nitrogen atmosphere. The identification of the gaseous species released by degradation in air within the endothermic domain made evident the presence of the same components of the degradation in nitrogen atmosphere. In the exothermic domain of the sample degradation in air, the CO₂, H₂O, SO₂ species result by the burning of the molecular residues of the first domain. The obtained results afforded a degradation mechanism to be advanced that coincide for the endothermic domain with that of degradation under nitrogen atmosphere. Due to the importance of these compounds as possible reaction initiators and also as potentially bioactive substances (herbicides, acaricides, fungicides), the study on their thermal degradation could give useful information on the environmental impact of the degradation products resulting by the thermal processing of the plants which could possible retain these compounds, when the initial degradation temperature is exceeded.     

Thermal analysis of lanthanide(III) and Y(III) complexes with 4-hydroxy-3-methoxybenzoic acid

Summary A procedure for the extrapolation of accelerated thermo-oxidative ageing tests to lower temperatures is proposed. The procedure involves a deconvolution of the global process into high- and low-temperature components where the extrapolation to low temperatures is carried out using the low-temperature component. The method was tested on stabilized and unstabilized polyisoprene rubber and was found to produce realistic estimations of the length of the induction period of oxidation so giving a more accurate estimation of the service life. However, to obtain the low-temperature values of the adjustable kinetic parameters, very low heating rates are required (0.04 K min^-1, 0.1 K min^-1) making the measurement process time consuming. Using this method, more realistic estimates of the durability of a material are obtained.