Investigation of imidization by differential thermal analysis

The DTA method has been used to show that, in the imidization of polyamido acid in solution in dimethylformamide, there is not only dehydrocyclization but also interaction of the solvent with reactive groups of the polyamido acid.     

Investigation of catalytic degradation of high-density polyethylene by hydrocarbon group type analysis

Catalytic degradation of waste high-density polyethylene (HDPE) to hydrocarbons by ZSM-5, zeolite-Y, mordenite and amorphous silica–alumina were carried out in a batch reactor to investigate the cracking efficiency of catalysts by analyzing the oily products including paraffins, olefins, naphthenes and aromatics with gas chromatography/mass spectrometry (GC/MS). Catalytic degradation of HDPE with zeolite-Y, mordenite and amorphous silica–alumina yielded 71–82 wt.% oil fraction, which mostly consisted of C₆–C₁₂ hydrocarbons, whereas ZSM-5 yielded much lower 35% oil fraction, which mostly consisted of C₆–C₁₂ hydrocarbons. Both all zeolites and silica–alumina increased olefin content in oil products, and ZSM-5 and zeolite-Y particularly enhanced the formation of aromatics and branched hydrocarbons. ZSM-5 among zeolites showed the greatest catalytic activity on cracking waste HDPE to light hydrocarbons, whereas mordenite produced the greatest amount of coke. Amorphous silica–alumina also showed a great activity on cracking HDPE to lighter olefins in high yield, but no activity on aromatic formation.     

Investigation of the Cu-Zr-Y oxides activity in the carbon black catalytic oxidation by differential thermal analysis and temperature programmed reduction

Different copper/zirconium-yttrium catalysts have been tested in carbon black oxidation reaction. Supported mainly on differential thermal analysis and temperature programmed reduction, two different mechanisms have been proposed to explain the catalytic results. In the absence of copper, it has been shown that Zr³⁺ ions and associated anionic vacancies are responsible to the catalytic enhancement observed in the mixed oxides, oxygen species being activated on these sites. Among mixed zirconia-yttria solids, ZrO₂-5 mol%Y₂O₃ is the most active catalyst. Copper impregnation on these oxides leads to the formation of different copper species. Small particles of CuO in low interaction with the support, induce a catalytic improvement due to the highest reducibility of these species. Moreover, in order to be more efficient, CuO species should have some interactions with the support, since impregnated samples are more active than the simple mechanical mixtures.     

Camphor cryoscopy by differential thermal analysis

The determination of the freezing point depression of organic solutions with camphor as solvent was performed by means of DTA. Amounts of 50–100μg substance and 1–2 mg camphor were weighed on a platinum wire, the camphor being pressed to a pellet by a glass press. The temperature difference between the glass tubes with pure camphor and with solution was recorded versus temperature, while the samples were cooled in a previously heated aluminium block. The difference between the recorded deviations from a straight line was found to be a measure of the freezing point depression. Errors less than 5 % were computed for various samples.     

Purity determinations by differential thermal analysis

Measurement of the melting-point depression of impure samples was compared with a differential method that involved running the impure sample against a pure sample of the same material. Samples of highly purified benzophenone to which had been added known quantities of 4-methylbenzophenone were studied. The area under the curve was proportional to the difference in purity between the sample and reference material over the range studied, 0.3-2.0 mole % with a standard deviation of 0.10 mole %, an uncertainty only half as large as one obtained by the melting-point depression method with the same apparatus.     

Characterization and analysis of waxes by differential thermal analysis

The characterization of waxes by differential thermal analysis is described. An endothermic peak at 475-480 degrees is characteristic of microcrystalline and polyethylene waxes, and measurement of its area provides a method for the estimation of these waxes in mixtures.     

A study of catalysts for desulphurization process by thermal analysis

A number of catalysts were prepared for the desulphurization process of tail gases. Their carrier was alumina oxide while the active phase was manganese. The catalysts were being tested in an lab apparatus. The effect of calcination temperature and process temperature of model gas (1 vol% of SO₂+99 vol% of N₂) were studied. The increase in the desulphurization temperature up to about 500°C causes the efficiency of the desulphurizing yield to be increased, a further increase of the temperature process decreases the SO₂ conversion. The DTA curves of catalysts after the desulphurizing process display the additional peak at a temperature of about 900°C being, perhaps, responsible for deactivation of the catalysts.     

Quantitative estimation of magnesite by differential thermal analysis

A method for quantitative estimation of magnesite in magnesite-rich rocks by differential thermal analysis, using magnesium hydroxide as internal standard, is presented. The effects of variations due to particle size and impurities are discussed.     

Dielectric differential thermal analysis

Dithionates (CaS₂O₆·4H₂O, SrS₂O₆·4H₂O, BaS₂O₆·2H₂O, MnS₂O₆·4H₂O, MgS₂O₆·6H₂O, CoS₂O₆·6H₂O, NiS₂O₆·6H₂O, ZnS₂O₆·6H₂O and CuS₂O₆·4H₂O) were subjected to thermodielectric analysis. The thermoanalytical curves show low temperature effects from 60 to 350°. These are related with the dehydration and decomposition of the dithionates, which could be fully correlated with the knowledge of the thermal behavior of these compouds obtained with other thermal methods.     

Dielectric differential thermal analysis

Thermodielectric analysis has been used to test some very well-characterized kaolins from Cuban deposits. The samples were analysed by thermal analysis, X-ray diffraction, infrared spectrometry, electron microscopy and chemical analysis.The dielectrical thermograms show that the most evident effect for the hydrated versions is the water peak. The second dielectric effect, at high temperatures, is related to the cationic conductions. A relation involving the K content of the sample was observed.

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Zusammenfassung Mittels thermodielektrischer Analyse wurden einige gut charakterisierte Kaoline aus kubanischen Lagerstätten untersucht. Die Proben wurden mittels Thermoanalyse (TA), Röntgendiffraktion (XRD), Infrarotspektroskopie (IR), Elektronenmikroskopie (EM) und Elementaranalyse untersucht. Die Dielektrothermogramme zeigen, daß bei den hydratierten Versionen der augenscheinlichste Effekt der Wasserpeak ist. Der zweite dielektrische Effekt bei höheren Temperaturen wird mit der Kationenleitung in Zusammenhang gebracht, wodurch es möglich wird, Informationen über den K-Gehalt der Proben zu erlangen.

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Dielectrical differential thermal analysis

Sodium faujasites with different Si/Al ratios were studied by means of thermodielectrical method.     

Dielectric differential thermal analysis

The present paper deals with the role of guest molecules in the moleculer sieves systems.     

Studies of calcium orthosilicate polymorphism by differential thermal analysis

The polymorphic transitions of calcium orthosilicate have been studied by means of differential thermal analysis. The parameters of-Ca₂SiO₄ synthesis without stabilizers haye been established.

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Zusammenfassung Mittels DTA wurden die Polymorphieübergänge von Kalziumorthosilikat untersucht. Die Parameter zur Synthese von-Ca₂SiO₄ ohne Stabilisatoren wurden bestimmt.

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Square modulated differential thermal analysis

KMnF₃ and DKDP crystals have been studied around their phase transitions using a conduction calorimetry technique where a long periodical square thermal pulse (0.05 K in amplitude) is superposed to a heating or cooling ramp as low as 0.06 K h⁻¹. Specific heat data obtained in the dissipation and relaxation semiperiods of the square pulse become different inside the phase transition interval. The electromotive force developed by the heat fluxmeters at the end of the relaxation semiperiod (underlying signal) is compared with the DTA trace obtained in a second run with the same temperature ramp but without the modulated perturbation. The comparison between the DTA trace and specific heat data obtained in the first run allows us to determine the value of the latent heat and to obtain information about the kinetic of the phase transition.     

Topological aspects of differential thermal analysis

The most important calorimetric methods have been reviewed: the differential thermal analysis (DTA) as basic disposition and the scanning calorimetry (DSC) as well as the adiabatic rate calorimetry (ARC). The thermal circuits of these are expressed by bond diagrams as conceived by topological thermodynamics. It has been stated that the heat flux associated with the process of transformation is virtually (uncompensated) transferred in the DTA system, really transferred (compensated) in the DSC and ARC systems, between the two containers through a transfer medium assumed to be purely dissipative.

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Zusammenfassung Eine Übersicht über die wichtigsten kalorimetrischen Methoden, sowie die Differentialthermoanalyse (DTA) als Grundverfahren, die Abtastkalorimetrie (DSC) und die adiabatische Geschwindigkeitskalorimetrie (ARC) wird gegeben. Die thermischen Kreise derselben werden durch Bindungsdiagramme, wie sie an Hand der topologischen Thermodynamik erhalten werden, ausgedrückt. Es wurde festgestellt, dass die Wärmeströmung mit dem Umwandlungsprozess assoziiert scheinbar (unkompensiert) in das DTA-System, wahrhaftig (kompensiert) in die Systeme DSC und ARC übertragen wird, undzwar zwischen den zwei Behältern durch ein als rein zerstreuend angenommenes Transfermedium.

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Résumé Mise au point sur les méthodes calorimétriques les plus importantes: l'analyse thermique différentielle (ATD) comme technique de base, l'analyse calorimétrique différentielle à compensation de puissance (DSC) et la calorimétrie à vitesse adiabatique (ARC). Les circuits thermiques de ces techniques s'expriment par des diagrammes de liaisons comme ceux conçus par la thermodynamique topologique. On établit que le flux de chaleur associé au processus de la transformation est virtuellement transferré (sans compensation) en ATD et réellement transferré (avec compensation) en DSC et ARC, entre les deux conteneurs par un milieu de transfert supposé être purement dissipatif.

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