The appearance of a compensation effect in the thermal decomposition of manganese(II) carbonates, prepared in the presence of other metal ions

In this study, a compensation effect is observed for the thermal decomposition of manganese(II) carbonates, prepared in the presence of Al³⁺ and Na⁺ ions. This compensation effect is described by the equation log A = aE + b, and the parameters are showm to be a = 0.1 and b = −2.9. The mechanism of decomposition was found to follow first order kinetics.

Both A, the pre-exponential function, and E, the energy of activation, depended on the concentration and type of metal ion present in the carbonate preparation, and on the experimental method used to obtain Arrhenius parameters. In the rising temperature experiments, more than one Arrhenius plot was obtained over different temperature ranges.     

The appearance of a compensation effect in the rising temperature decomposition of a series of pure carbonates

In this study, a compensation effect is observed for the rising temperature decomposition of a series of pure carbonates. This compensation effect is described by the equation

and the parameters are shown to be a = 0.22 and b = ?4.16. The mechanism of decomposition was found to follow first order kinetics.An isokinetic point was found in the experimental region but, since one of the samples has a different decomposition mechanism, this criterion for a genuine compensation effect is obviously unsound. A model involving a distribution of active sites on a reacting solid has been discussed.     

Study of the thermal decomposition kinetics of some rare earth carbonates,fluorocarbonates and fluorooxalates

The thermal transformations of Pr and La carbonates, La, Ce, Pr, Nd, Sm, Eu and Gd fluorocarbonates, and La, Nd, Dy and Ho fluorooxalates were investigated. A Derivatograph Q-1000 (MOM, Hungary) was used for thermal analysis. The kinetics of the processes was studied in a flow reactor. The activation energies and preexponential factors for dehydration and decarbonization were calculated. Samples of Pr fluorocarbonate, Ho fluorooxalate, and Pr and La carbonates were exposed to γ-irradiation (dose from 6.2·10⁶ to 6.1·10⁷ rad). The influence of the irradiation dose upon the kinetic parameters (E _a andA) of the processes was investigated.     

The compensation effect in the kinetics of the thermal decomposition of calcium carbonate

The kinetic parameters of the Arrhenius equation for the thermal decomposition of CaCO₃ depending on the values of the sample weight and of the linear heating rate are interrelated by the compensation relationship lgA=a+bH*.     

The effect of mechanical activation on the thermal decomposition of chalcopyrite

Experimental results on the influence of preliminary mechanical activation on the thermal decomposition of chalcopyrite are presented and discussed. The following experimental facts were found:

The effect of catalysts on the thermal decomposition of sodium superoxide

Simultaneous differential thermal, thermogravimetric and differential thermogravimetric analysis have been made on samples of sodium superoxide and sodium superoxide containing l% (w/w) copper(I) oxide. Decomposition of the superoxide involving oxygen production (weight loss) does not occur at a meaningful rate until temperatures approach 250°. The effects of 12 metallic oxide catalysts and one metalloorganic catalyst on the decomposition of sodium superoxide have been studied by differentialthermal analysis. Six metallic oxides had no effect while 3 oxides, (palladium oxide, titanium oxide and cadmium oxide) caused small but distinct changes in the DTA plots. A polymeric phthalocyanine, and the oxides of vanadium(III), vanadium(V) and manganese (IV) apparently reacted with the superoxide above 250°. Pretreatment of the superoxide by brief exposure to 100% humidity resulted in the formation of peroxyhydrates of sodium peroxide which upon dissociation produced water vapor in turn causing the release of oxygen from the superoxide and peroxide at lower temperatures than those experienced with untreated superoxide samples.     

The effect of alkaline pretreatment on the thermal decomposition of hemp

The goal of this study was to clarify the effect of alkaline pretreatments on the thermal decomposition and composition of industrial hemp (Cannabis sativa L.) samples. Thermogravimetric/mass spectrometric measurements (TG/MS) have been performed, on untreated, hot water washed, and alkali-treated hemp samples. The main differences between the thermal decomposition of the samples are interpreted in terms of the different alkali ion contents which have been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. Principal component analysis (PCA) has been used to find statistical correlations between the data. Correlations have been obtained between the parameters of the thermal decomposition and the alkali ion content as well as the altered chemical structure of the samples. The differences in the thermal behavior of the samples are explained by the different K⁺ and Na⁺ contents and the changed structure of the hemicellulose component of the samples due to the pretreatments. The more alkali ions remain in the hemp samples after the alkali treatment, the more ash, char and lower molecular products are formed during thermal decomposition.     

The catalytic effect of NiO on thermal decomposition of nitrocellulose

The catalytic effect of NiO on thermal decomposition of nitrocellulose (NC) has been investigated via thermogravimetry–mass spectrometry (TG–MS) coupling technique, and the residue of NC with 20% NiO reacted in tubular furnace was analyzed by X-ray diffraction (XRD). TG–MS analysis showed that adding 2% NiO to NC accelerated the thermal decomposition process and promoted the generation of gaseous products. The catalytic mechanism was based on the accelerated generation of NO₂, which further reacted with the radical to produce other gaseous products. XRD analysis of catalyst residue showed that Ni was formed during the catalytic reaction.     

The effect of γ-irradiation on the thermal decomposition of strontium nitrate

The thermal decomposition of -irradiated strontium nitrate was studied by dynamic thermogravimetry. The reaction order, activation energy, frequency factor and entropy of activation were computed by means of the Coats-Redfern method and were compared with those for the unirradiated salt. It has been suggested that NO₂ formed under irradiation catalyzes the decomposition.     

The effect of gamma-irradiation on the thermal decomposition of anhydrous cadmium nitrate

The thermal decomposition of -irradiated anhydrous cadmium nitrate was studied by dynamic thermogravimetry. The reaction order, activation energy, frequency factor and entropy of activation were calculated by the Coats-Redfern method and were compared with those of the unirradiated salt. Irradiation enhances the decomposition and the effect increases with the irradiation dose. The activation energy decreases on irradiation. The mechanism of the decomposition of unirradiated and irradiated anhydrous cadmium nitrate follows the Mampel equation: -ln(1-) for g() and the rate-controlling process is random nucleation with the formation of a nucleus on every particle.     

The effect of γ-irradiation on the thermal decomposition of magnesium bromate

The thermal decomposition of -irradiated magnesium bromate was studied by dynamic thermogravimetry. The reaction order, activation energy, frequency factor and entropy of activation were calculated by the Coats-Redfern equation and were compared with those of the unirradiated salt. Irradiation enhances the decomposition and the effect increases with irradiation dose. The activation energy decreases on irradiation. The mechanism for the decomposition of unirradiated and irradiated magnesium bromate follows the Avrami model equation, 1-/1-/1/3=kt, and the rate-controlling, process is a phase boundary reaction assuming spherical symmetry.     

The effect of the starting material on the thermal decomposition of iron oxyhydroxides

The effect of the iron precursor on the thermal decomposition of iron oxyhydroxides was studied by DSC, DTA and TG in this work. Samples were prepared from iron nitrate, iron sulfate and iron chloride and the thermal curves obtained were analyzed by specific area measurements, X-ray diffraction and Mössbauer spectroscopy. It was found that the iron oxyhydroxide precursors affect the temperatures of the hematite formation as well as the textural properties of the final hematite producing particles with different diameters as following: iron sulfate (3.3 nm)相似文献   

The effect of pressure on the kinetics of thermal decomposition of ammonium perchlorate

Summary The kinetics of thermal decomposition of ammonium perchlorate at 230 and 260 are not changed under the influence of a pressure of 100 atm of an inert gas.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12 p. 2226–2227, December, 1964     

The effect of particle size on the thermal decomposition kinetics of potassium bromate

The thermal decomposition of potassium bromate (KBrO₃) has been studied as a function of particle size, in the range 53?C150???m, by isothermal thermogravimetry at different temperatures, viz. 668, 673, 678, and 683?K in static air atmosphere. The theoretical and experimental mass loss data are in good agreement for the thermal decomposition of all samples of KBrO₃ at all temperatures studied. The isothermal decomposition of all samples of KBrO₃ was subjected to both model fitting and model-free (isoconversional) kinetic methods of analysis. Isothermal model fitting analysis shows that the thermal decomposition kinetics of all the samples of KBrO₃ studied can be best described by the contracting square equation. Contrary to the expected increase in rate followed by a decrease with decrease in particle size, KBrO₃ shows a regular increase in rate with reduction in particle size, which, we suggest, is an impact of melting of this solid during decomposition.     

The effect of sampling conditions on the thermal decomposition of electrolytic manganese dioxide

The effect of sampling conditions on the decomposition of electrolytic manganese dioxide using thermal methods is reported. Significant differences were observed in the mechanism of the decomposition by simply changing the reaction environment from a closed pan to an open pan configuration. The purge gas atmosphere was also observed to influence the decomposition mechanism. As a product of the decomposition is oxygen, the change in the mechanism observed between the experimental conditions may be explained in terms of the ease of removal of oxygen from the reaction site. This revised version was published online in August 2006 with corrections to the Cover Date.     

The thermal decomposition of water

The reflected shock tube technique with multipass absorption spectrometric detection of OH‐radicals at 308 nm, corresponding to a total path length of 1.749 m, has been used to study the reaction H₂O + M → H + OH + M between 2196 and 2792 K using 0.3, 0.5, and 1% H₂O, diluted in Kr. As a result of the increased sensitivity for OH‐radical detection, the existing database for this reaction could be extended downward by ～500 K. Combining the present work with that of Homer and Hurle, the composite rate expression for water dissociation in either Ar or Kr bath gas is k_{1,Ar(or Kr)} = (2.43 ± 0.57) × 10^?10 exp(?47117 ± 633 K/T) cm³ molecule^?1 s^?1 over the T‐range of 2196–3290 K. Applying the Troe factorization method to data for both forward and reverse reactions, the rate behavior could be expressed to within <±18% over the T‐range, 300–3400 K, by the three‐parameter expression k_1,Ar = 1.007 × 10⁴ T^?3.322 exp(?60782 K/T) cm³ molecule^?1 s^?1 A large enhancement due to H₂O with H₂O collisional activation has been noted previously, and both absolute and relative data have been considered allowing us to suggest k₁, H₂ O = 1.671 × 10² T^?2.440 exp(?60475 K/T) cm³ molecule^?1 s^?1 for the rate constants with H₂O bath gas over the T‐range, 300–3400 K. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 211–219, 2006     

The thermal decomposition of biacetyl

The thermal decomposition of biacetyl has been studied at small percentage conversion over the temperature range 375-417°C. For these conditions, an almost quantitative mass balance was obtained by gas-chromatographic analysis. The following equation was obtained for the overall reaction Between 240° and 277°C, the decomposition of biacetyl initiated by methyl radicals has also been studied. As source of radicals, the thermolysis of azomethane was used. Moreover, the Arrhenius parameters of the following reactions were determined: where A is in sec^?1 for reaction (1) and in cm³mole^?1 sec^?1 for reactions (3) and (4); E is in kcal/mole. Evidence is provided that the displacement reaction (4) proceeds by a two step mechanism.