G. Hakvoort

Measurement of the thermal conductivity of solid substances by DSC

Abstract The thermal conductivity of solid samples can be measured with DSC by melting experiments with a pure metal (indium or gallium) on top of cylindrical pellets. Particularly samples with a low thermal conductivity, like plastics or porous substances, can be determined

TG measurement of gas-solid reactions. The effect of the shape of the crucible on the measured rate

Abstract The effective rate of gas—solid reactions does not only depend on the chemical reaction rate, but also on the transport of the active compounds through the surrounding gas phase and through the pores of the solid sample. The gas phase transport strongly depends on the shape of the sample holder. Therefore TG measurements of gas-solid reactions show a great range in measured rate and apparent kinetic mechanism, depending on the specific sample holder used. Investigations have been made of the absorption of sulfur oxide onto spherical CaO/Al 2 O 3 pellets. A shrinking-core model was applied for the description of the reaction. So the rate constants of the separate processes can be calculated. In this way the effect of any specific type of sample holder can be quantitatively determined.

The determination of coal combustion kinetics with thermogravimetry

This investigation concerns the determination of the kinetics of coal combustion. It is not well possible to use an exact analytical formula for the rate equation. For that reason a stepwise method is proposed, giving the activation energy as function of the reaction parameter α, without assumption of any specific rate equation.ZusammenfassungDiese Arbeit beschäftigt sich mit der Kinetik der Kohleverbrennung. Für die Reaktionsgeschwindigkeit ist es jedoch nicht möglich, eine exakte analytische Gleichung anzuwenden. Aus diesem Grunde wird ein schrittweises Vorgehen vorgeschlagen, das die Aktivierungsenergie ohne Voraussetzung jeglicher spezifischer Geschwindigkeitsgleichungen als Funktion des Reaktionsparameters α liefert.РезюмеИсследование касает ся определения кинет ики горения угля. Не представилос ь возможным применит ь какое-либо точное аналитическое выраж ение уравнения скоро сти реакции. В связи с этим предложен ступе нчатый метод, дающий э нергию активации как функцию реакционног о параметра α, без пред положения какого-либо характерного уравне ния скорости реакции.

DSC calibration during cooling

A number of compounds are investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions and can be applied both for temperature and for heat calibration. A third compound, namely 4,4′-azoxyanisole, has a liquid crystal to isotropic liquid transition at 409 K. This compound can be used for temperature calibration. Heat calibration with this compound is more problematic because of the small heat effect and the construction of the baseline. Two other compounds, namely Hg and Pb, show a slight undercooling. Nevertheless they can be used for heat calibration, and possibly also for temperature calibration during cooling.

TG study of sorbent materials for desulfurization of combustion gases at high temperature

Abstract Several compounds are investigated by thermogravimetry for their possible use as regenerative sorbent material for desulfurization of combustion gases at high temperatures. It is demonstrated that pellets of α-Al2O3, impregnated with CaO, give good results, both for sulfure capture and regeneration.

Comparing regenerative SO2 sorbents using tg: The SRO test

Abstract Several synthetic sorbents for regenerative desulphurization in fluidized bed combustion of coal were investigated for their sulphation, regeneration and cyclic behaviour using the thermogravimetry

DSC calibration below 0°C

SummaryThis contribution deals with the calibration of a DSC apparatus between −100 and 0°C using compounds with well-known temperature and heat of transition. Only a few suitable substances are mentioned in literature. For that reason another compound, adamantane, is proposed with a solid-solid transition at −64.56°C and a heat of reaction being 24.78 J/g.ZusammenfassungUnter Verwendung von Substanzen mit genau bekannten Umwandlungs-temperaturen und-wärmen befaßte man sich mit der Kalibrierung von DSC-Geräten im Temperaturbereich von −100 bis 0°C. In der Literatur werden nur einige wenige geeignete solcher Substanzen erwähnt. Aus diesem Grunde wird als weitere Substanz Adamantan mit einem Feststoff-Feststoff-Umwandlungspunkt bei −64.56°C und einer Reaktionswärme von 24.78 J/g vorgeschlagen.

DSC Calibration During Cooling. A survey of possible compounds

A number of compounds is investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions and can be applied both for temperature and for heat calibrations. A third compound, namely 4,4’-azoxyanisole, has a liquid crystal to isotropic liquid transition at 409K. This compound can be used for temperature calibration. Heat calibration with this compound is more problematic because of the small heat effect and the construction of the baseline. Other compounds like NaNO3, In, Hg and Pb, show a slight supercooling. Nevertheless they can be used for heat calibration. The use of large samples of NaNO3 and In gives the possibility to construct the equilibrium onset temperatures of the cooling peaks, so these two compounds are also appropriate for temperature calibration on cooling.

Thermal analysis of Cu(II) imidazole coordination compounds

Abstract Thermal decomposition reactions of compounds Cu(LH) n X 2 , with LH  imidazole (IzH) and N -methyl imidazole (NMeIzH), n = 2, 4 and X  Cl, Br, have been studied with the acid of thermogravimetric analysis (TG), mass spectroscopy (MS), high-temperature X-ray powder diffraction and differential scanning calorimetry (DSC). Only in a few cases could simple ligand losses be studied. In most cases a simultaneous ligand loss and redox reaction occured, resulting in CuCl (or CuBr) and finally Cu metal. One of the oxidation products could be characterized by mass spectroscopy and appeared to be chlorinated imidazoles. This relative stabilization of Cu(I) by imidazole ligands corresponds with known synthetical chemistry. No accurate binding enthalpies for the imidazole ligands could be deduced.

A practical thermal analysis course

A practical Thermal Analysis Course is described, lasting one full week, in which the stuents are performing at least 10 experiments from different kinds, covering a broad range of possible applications. In combination with the elaboration of the experiments a number of lectures is given about the practice of thermal analysis. So a course is obtained, in which the students learn a lot of the possibilities (and impossibilities) of thermal analysis techniques, particularly by experiments, performed by their own.