Some experimental aspects of DSC determination of kinetic parameters in thermal decompositions of solids

Guarini, G. G. T.; Spinicci, R.; Carlini, F.M.; Donati, Donato

doi:10.1007/bf01950378

Cited by 30 publications

(17 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Plots of u/time vs. time were made for the isothermal weight loss data (Figure 2) since this plot can give an indication of the type of mechanism of the decomposition (Guarini and Spinicci, 1972). Significantly, the shape of the curve is not consistent with an AvramiErofeev expression for the process, which requires a maximum in the c~/time vs. time curve, usually at a 0.6 or 0.7.…”

Section: Resultsmentioning

confidence: 99%

Thermal Decomposition of a Kaolinite:Dimethyl Sulfoxide Intercalate

Adams

Waltl

1980

Clays and clay miner.

View full text Add to dashboard Cite

Abstract--The thermal decomposition of a kaolinite:dimethyl sulfoxide intercalate has been studied by thermogravimetry. The decomposition is complete by 175~ and has a AH of 58 • 5 kJ/mole of dimethyl sulfoxide. For the first 70-80% of the reaction a plot of log(1 -a) vs. time is linear, where c~ is the reaction fraction complete. A two-dimensional, contracting-circle type of mechanism is consistent with this linearity, provided that the nucleation process is considered to be exponential rather than instantaneous. An activation energy of 105 • 8 k J/mole of dimethyl sulfoxide has been derived. This value is inconsistent with the simple assumption that the rate-determining step is the freeing of single organic molecules from their bonding to the clay layers. The mechanism of this decomposition is different from that found for kaolinite: N-methyl formamide, and the activation energy is considerably greater than that found for that material (30 • 3 kJ/mole).

show abstract

Section: Resultsmentioning

confidence: 99%

Thermal Decomposition of a Kaolinite:Dimethyl Sulfoxide Intercalate

Adams

Waltl

1980

Clays and clay miner.

View full text Add to dashboard Cite

show abstract

“…( 1 972) and Guarini et al (1973) indicated that the decomposition was first-order in mass of NaHCO,. Since the reaction is not expected to be a surface phenomenon, this finding is logical.…”

Section: Calculation Of Rate Constantsmentioning

confidence: 98%

“…Also, rates of decomposition and of reaction with SO, have been measured separately on different samples (Subramanian et al, 1972; Guarini et al, 1973; Bares et al, 1970; Marecek et al, 1970).…”

Section: Scopementioning

confidence: 99%

See 1 more Smart Citation

Kinetics of sodium bicarbonate decomposition

et al. 1986

View full text Add to dashboard Cite

A thermal gravimetric method was used to measure rates of decomposition of NAHCO, particles. Such decomposition produces a highly porous Na,Co, that reacts with SO, rapidly and completely at moderate temperatures. Hence, NaHCO, decomposition provides a reactant with attractive features for SO, removal. The rapid rate of decomposition combined with the high heat effect prevented determining intrinsic rates by constant temperature runs when the temperature level was above 400 K. However, rising-temperature runs, which allowed time for heat transfer to equilibrate temperatures of the thermocouple and particles, gave reliable results at high temperatures. The activation energy was 102 kJ/mol. Porosimeter data verified the large increase in pore volume (from 0.03 to 0.39 x lo-, m3/kg) on converting the NaHCO, particles to Na,CO,.First-order kinetics were observed up to high conversions, after which the apparent order decreased. However, the sodium bicarbonate could be completely converted to Na,CO,. SCOPEIt has been well established that thermal decomposition of NaHCO, particles can produce a highly porous Na,CO, product that reacts rapidly with SO, in waste gases (Bares et at., 1970; Marecek et al., 1970 Our objective was to determine the rate of decomposition of a sample of NaHCO, particles at temperatures from 373 to 473 K over the complete range of conversion. A TGA apparatus was employed since this allowed very small sample masses to be used (leading to accurate rates) and the effect of heat and mass of transfer processes could usually be eliminated. Porevolume data also were obtained on NaHCO, and Na,CO, particles. CONCLUSIONS AND SIGNIFICANCEThe rapid rate of decomposition of NaHCO, combined with a large, endothermic heat effect required careful choice of operating conditions to obtain rates unaffected by heat transfer. At temperatures above 400 K this required the TGA experiments to be conducted by the rising-temperature method. The results showed that intrinsic kinetics were first-order in mass of NaHCO, up to high conversions. The retardation of the rate beyond this point may be due to changes in the AIChE JournalSeptember 1986 nature of the remaining Na,CO,, or the structure of the Na,CO, product surrounding the unreacted Na,HCO,. However, the rate remained high at high conversions so that the NaHCO, was completely converted to the carbonate. The data also showed that the rate decreased when the decomposition temperature was reduced from 473 to 373 K. Corresponding pore-volume data indicated that the surface area was greater for particles decomposed at 373 K.

show abstract

“…The kinetic analysis of the thermal curves was performed as reported in previous papers [8,9]. From an examination of the Arrhenius plots of a number of laws usually applied to the kinetics of decomposition of solids [10], some evidence emerged:…”

Section: Calorimetric Measurementsmentioning

confidence: 99%

Kinetics of thermal dehydration of Ba(ClO3)2 · H2O

Guarini

Spinicci

Virgili

1978

Journal of Thermal Analysis

Self Cite

View full text Add to dashboard Cite

The kinetics of thermal dehydration of microcrystalline powders and single-crystals of barium chlorate monohydrate were studied by differential scanning calorimetry. The computer elaboration of thermal data showed that a single kinetic law could not account for the whole decomposition; moreover, different laws had to be used for powders than for single-crystals, whose reaction appeared diffusion-limited towards the end of the dehydration. Optical microscopy was extensively used as an independent source of information to clarify some of the thermal results and to gain a deeper insigth into the possible reaction mechanism.The use of thermal methods to study the reactivities of solids has become more and more popular because of the relatively easy experimentation. Parallel to this growth, a deep improvement of the underlying theory has taken place [1 ]. However, the deduction of meaningful kinetic parameters is not always as straightforward as it might appear and a careful analysis of the thermal data, usually performed by computer techniques, is necessary. Nevertheless, this is sometimes not enough and an independent source of information is required.Optical microscopy is particularly useful when reactions of the type Asoli a Bsoli a + Cgas , in which nucleation takes place on external surfaces, are considered; in fact, nucleation and growth rates are easily obtained. Moreover, if correspondence of nuclei and sites of emergence of dislocations is evidenced, some insight into the reaction mechanism may be gained by a determination of the possible dislocation systems in the parent crystal, using the etching technique.In a study on the kinetics of thermal dehydration of a number of crystal hydrates and hydroxides, planned to compare structure, defects and reactivity in order to seek possible correlations, barium chlorate monohydrate (BCM) was taken into consideration because a) its structure is known; b) crystalline powders and single-crystals are easily obtained; c) the water molecule is lost stoichiometrically in a single step; d) its crystals are easily cleaved.Moreover, preliminary thermal runs had evidenced some discrepancies in the behaviour of powders and single-crystals which were not amenable to the effects of the parameters which usually influence the thermal curves (e.g. sample mass, nitrogen flow, scan speed) [2]. BCM therefore appeared particularly suitable to check the complementarity of thermal methods and optical microscopy.

show abstract

Some experimental aspects of DSC determination of kinetic parameters in thermal decompositions of solids

Cited by 30 publications

References 5 publications

Thermal Decomposition of a Kaolinite:Dimethyl Sulfoxide Intercalate

Thermal Decomposition of a Kaolinite:Dimethyl Sulfoxide Intercalate

Kinetics of sodium bicarbonate decomposition

Kinetics of thermal dehydration of Ba(ClO3)2 · H2O

Contact Info

Product

Resources

About