Water vapor effect on the physico-geometrical reaction pathway and kinetics of the multistep thermal dehydration of calcium chloride dihydrate.

This study investigated how water vapor influences the reaction pathway and kinetics of the multistep thermal dehydration of inorganic hydrates, focusing on CaCl·2HO (CC-DH) transforming into its anhydride (CC-AH) an intermediate of its monohydrate (CC-MH). In the presence of atmospheric water vapor, the thermal dehydration of CC-DH stoichiometrically proceeded through two distinct steps, resulting in the formation of CC-AH CC-MH under isothermal conditions and linear nonisothermal conditions at a lower heating rate (). Irrespective of atmospheric water vapor pressure ((HO)), these reaction steps were kinetically characterized by a physico-geometrical consecutive process involving the surface reaction and phase boundary-controlled reaction, which was accompanied by three-dimensional shrinkage of the reaction interface.

The physico-geometrical reaction pathway and kinetics of multistep thermal dehydration of calcium chloride dihydrate in a dry nitrogen stream.

Several inorganic hydrates exhibit reversible reactions of thermal dehydration and rehydration, which is potentially applicable to thermochemical energy storage. Detailed kinetic information on both forward and reverse reactions is essential for refining energy storage systems. In this study, factors determining the reaction pathway and kinetics of the multistep thermal dehydration of inorganic hydrates to form anhydride intermediate hydrates were investigated as exemplified by the thermal dehydration of CaCl·2HO (CC-DH) in a stream of dry N.

Efflorescence kinetics of sodium carbonate decahydrate: a universal description as a function of temperature, degree of reaction, and water vapor pressure.

The efflorescence of sodium carbonate decahydrate (SC-DH) required to form its monohydrate (SC-MH) was systematically studied under isothermal and linear nonisothermal conditions at different atmospheric water vapor pressures ((HO)) using a humidity-controlled thermogravimetry instrument equipped with a cooling circulator. The universal kinetic description at various temperatures () and (HO) values was evaluated using the extended kinetic equation with an accommodation function (AF) comprising (HO) and the equilibrium pressure of the reaction (()). By optimizing two exponents in the AF, all kinetic data were universally described in terms of the isoconversional kinetic relationship examined at individual degrees of reaction ().

Thermal dehydration of D-glucose monohydrate in solid and liquid states.

The physico-geometrical reaction pathway and kinetics of the thermal dehydration of D-glucose monohydrate (DG-MH) dramatically alter by the melting of the reactant midway through the reaction. By controlling the reaction conditions, the thermal dehydration of DG-MH was systematically traced by thermoanalytical techniques in three different reaction modes: (1) solid-state reaction, (2) switching from a solid- to liquid-state reaction, and (3) liquid-state reaction. Solid-state thermal dehydration occurred under isothermal conditions and linear nonisothermal conditions at a small heating rate ( ≤ 1 K min) in a stream of dry N.

Physico-geometrical kinetic insight into multistep thermal dehydration of calcium hydrogen phosphate dihydrate.

The origin of the multistep thermal dehydration of calcium hydrogen phosphate dihydrate (dibasic calcium phosphate dihydrate (DCPD)) to form γ-calcium diphosphate (γ-calcium pyrophosphate (γ-CPP)) calcium hydrogen phosphate anhydride (dibasic calcium phosphate anhydride (DCPA)) was investigated from a specific viewpoint of physico-geometrical constraints generated during the reaction. The overall thermal dehydration was separated into five partially overlapping steps through systematic kinetic analysis. The first three steps and the residual two steps were attributed to the thermal dehydration of DCPD to form DCPA and of DCPA to form γ-CPP, respectively.

Effect of atmospheric water vapor on independent-parallel thermal dehydration of a compacted composite of an inorganic hydrate: sodium carbonate monohydrate grains comprising crystalline particles and a matrix.

The effect of atmospheric water vapor on the thermal dehydration of sodium carbonate monohydrate (SC-MH), which was characterized as cubic grains of a compacted composite comprising columnar SC-MH crystals and a matrix, was systematically assessed using a humidity-controlled thermogravimetry system at various atmospheric water vapor pressures ((HO)). The thermal dehydration of the SC-MH compacted composite occurred an induction period (IP) and partially overlapping two-step mass loss steps due to the thermal dehydration of the SC-MH matrix and columnar crystals. All component reaction steps were retarded with an increase in the (HO) value.

Physico-geometrical kinetics of the thermal dehydration of sodium carbonate monohydrate as a compacted composite of inorganic hydrate comprising crystalline particles and matrix.

The kinetics of the thermal dehydration of compacted composite grains of NaCO·HO (SC-MH) comprising columnar SC-MH crystalline particles and an SC-MH matrix were investigated as a model system for composites of the same compound with a porphyritic texture. The presence of an induction period was confirmed as a novel finding for the thermal dehydration of SC-MH. The subsequent mass loss process was characterized as a partially overlapping two-step process attributed to the consecutive reactions of SC-MH matrix and columnar SC-MH crystalline particles.

Individual effects of atmospheric water vapor and carbon dioxide on the kinetics of the thermal decomposition of granular malachite.

This study examined the effects of atmospheric water vapor and CO on the thermal decomposition of granular malachite as a model process for the thermal decomposition of large and compact agglomerate solids. In previous studies in a dry N gas stream, the thermal decomposition of the granular malachite exhibited physico-geometrically constrained two-step mass loss behaviors accompanied by the swelling of granular particles and crack formation in the surface product layer of each granule. In the presence of atmospheric water vapor, the reaction was shifted systematically to lower temperatures with increasing atmospheric water vapor pressure ((HO)) by maintaining the two-step mass loss behavior.

An advanced kinetic approach to the multistep thermal dehydration of calcium sulfate dihydrate under different heating and water vapor conditions: kinetic deconvolution and universal isoconversional analyses.

This study aims to identify the kinetic features of individual reaction steps of the multistep thermal dehydration of calcium sulfate dihydrate (CS-DH) to anhydride a hemihydrate (CS-HH) intermediate by achieving the universal kinetic description of each reaction step under different heating and water vapor pressure ((HO)) conditions. The mass loss processes of the thermal dehydration of CS-DH were systematically traced humidity-controlled thermogravimetry under isothermal and linear nonisothermal conditions at various atmospheric (HO) values. After reconfirming the variation in the thermal dehydration pathway from a single-step dehydration to anhydride to a multistep process the CS-HH intermediate with an increase in the (HO) value, the kinetic curves for each component reaction step were obtained by separating each component process from the partially overlapping mass-loss curves by kinetic deconvolution analysis as required.

Thermally induced dehydration reactions of monosodium L-glutamate monohydrate: dehydration of solids accompanied by liquefaction.

In this study, we investigated the mechanistic features and kinetics of the thermal decomposition of solids accompanied by liquefaction as exemplified by the thermal dehydration reactions of monosodium L-glutamate monohydrate (MSG-MH). The thermal dehydration of MSG-MH occurs two mass-loss processes comprising the elimination of crystalline water and intramolecular dehydration. Multistep kinetic behaviors and the liquefaction during both thermal dehydration processes were evidenced by systematic thermoanalytical measurements and microscopic observations.

Geometrical constraints of thermal dehydration of β-calcium sulfate hemihydrate induced by self-generated water vapor.

The thermal dehydration of calcium sulfate dihydrate exhibits a complex reaction behavior, in which the reaction pathway and kinetics vary depending on water vapor pressure ((HO)) applied as the atmospheric condition and generated in the course of the reaction. Under high (HO) conditions, a crystalline hemihydrate is produced as an intermediate, which subsequently dehydrates to form anhydride. In this study, the thermal dehydration of calcium sulfate hemihydrate under different self-generated (HO) conditions was investigated to gain further insight into the reactions in the calcium sulfate-water vapor system.

Thermal decomposition of spherically granulated malachite: physico-geometrical constraints and overall kinetics.

The thermal decomposition of spherically granulated malachite particles was investigated to unveil the specific kinetic features of the reaction in samples in granular form toward the improvement of the thermal processing of malachite as a precursor of functional CuO. Granular malachite underwent thermal decomposition via a partially overlapping two-step mass loss process upon heating the sample in a stream of dry N2 gas. Morphologically, the process was characterized by swelling of the granular particles and cleavage divisions of the surface layer.

Thermally Induced Aragonite-Calcite Transformation in Freshwater Pearl: A Mutual Relation with the Thermal Dehydration of Included Water.

This study focuses on the relationship between the aragonite-calcite (A-C) transformation and the thermal dehydration of included water in the biomineralized aragonite construction using freshwater pearl. These thermally induced processes occur in the same temperature region. The thermal dehydration of included water was characterized through thermoanalytical investigations as an overlapping of three dehydration steps.

Apparent autocatalysis due to liquefaction: thermal decomposition of ammonium 3,4,5-trinitropyrazolate.

Thermal decomposition of solids is often accompanied by autocatalysis, one of the possible causes of which is the formation of a liquid phase. The kinetic model considering the liquefaction of solid reactants under isothermal conditions was proposed by Bawn in the 1950s. The present study reports the application of the Bawn model to the thermolysis of 3,4,5-trinitropyrazole ammonium salt (ATNP) under nonisothermal conditions.

Thermal dehydration of calcium sulfate dihydrate: physico-geometrical kinetic modeling and the influence of self-generated water vapor.

Complex kinetic behaviors in the thermal dehydration of CaSO4·2H2O under varying water vapor pressure (p(H2O)) conditions impel researchers in the field of solid-state kinetics to gain a more comprehensive understanding. Both self-generated and atmospheric p(H2O) are responsible for determining the reaction pathways and the overall kinetic behaviors. This study focuses on the influence of the self-generated water vapor to obtain further insights into the complexity of the kinetic behaviors.

Kinetics of contracting geometry-type reactions in the solid state: implications from the thermally induced transformation processes of α-oxalic acid dihydrate.

This study focuses on the physico-geometrical constraints of the kinetics of the thermal decomposition of solids as exemplified by the thermal dehydration of α-oxalic acid dihydrate and the subsequent thermally induced sublimation/decomposition of the as-produced anhydride using the samples of crystalline particles (CPs) and a single crystal (SC) form. The CP and SC samples possess approximately similar geometrical figures with different sizes. The shapes of the original dihydrate and the as-produced anhydride from thermal dehydration are practically congruent.

Revealing the effect of water vapor pressure on the kinetics of thermal decomposition of magnesium hydroxide.

This study aims to establish an advanced kinetic theory for reactions in solid state and solid-gas systems, achieving a universal kinetic description over a range of temperature and partial pressure of reactant or product gases. The thermal decomposition of Mg(OH)2 to MgO was selected as a model reaction system, and the effect of water vapor pressure p(H2O) on the kinetics was investigated via humidity controlled thermogravimetry. The reaction rate of the thermal decomposition process at a constant temperature was systematically decreased by increasing the p(H2O) value, accompanied by an increase in the sigmoidal feature of mass-loss curves.

Thermal Decomposition of Maya Blue: Extraction of Indigo Thermal Decomposition Steps from a Multistep Heterogeneous Reaction Using a Kinetic Deconvolution Analysis.

Examining the kinetics of solids' thermal decomposition with multiple overlapping steps is of growing interest in many fields, including materials science and engineering. Despite the difficulty of describing the kinetics for complex reaction processes constrained by physico-geometrical features, the kinetic deconvolution analysis (KDA) based on a cumulative kinetic equation is one practical method of obtaining the fundamental information needed to interpret detailed kinetic features. This article reports the application of KDA to thermal decomposition of clay minerals and indigo-clay mineral hybrid compounds, known as Maya blue, from ancient Mayan civilization.

Critical Appraisal of Kinetic Calculation Methods Applied to Overlapping Multistep Reactions.

Thermal decomposition of solids often includes simultaneous occurrence of the overlapping processes with unequal contributions in a specific physical quantity variation during the overall reaction (e.g., the opposite effects of decomposition and evaporation on the caloric signal).

Impact of atmospheric water vapor on the thermal decomposition of calcium hydroxide: a universal kinetic approach to a physico-geometrical consecutive reaction in solid-gas systems under different partial pressures of product gas.

Thermal decomposition of Ca(OH)2 under atmospheric water vapor exhibits special features, including an induction period (IP) and a subsequent sigmoidal mass-loss behavior under isothermal conditions. Atmospheric water vapor reduces the reaction rate at a specific temperature and causes a systematic shift of the mass-loss curve, which was recorded at a specific heating rate, to higher temperatures as the water vapor pressure, p(H2O), increases. The challenge in this study was to universally describe the kinetics of thermal decomposition under various p(H2O) conditions by introducing an accommodation function in the fundamental kinetic equation.

Thermally induced carbonation of Ca(OH) in a CO atmosphere: kinetic simulation of overlapping mass-loss and mass-gain processes in a solid-gas system.

Thermally induced carbonation of Ca(OH) in a CO atmosphere is a reaction exhibiting particular features, including stoichiometric completeness to form CaCO and a kinetic advantage over the carbonation of CaO particles. This study aims to gain further insight into the reaction mechanisms of CO capture by Ca(OH) and CaO. It focuses on the kinetic modeling of the carbonation of Ca(OH) as a consecutive reaction in a solid-gas system.

Multistep thermal decomposition of granular sodium perborate tetrahydrate: a kinetic approach to complex reactions in solid-gas systems.

This article demonstrates a kinetic approach to partially overlapping multistep chemical reactions in solid-gas systems as exemplified by the thermal decomposition of granular sodium perborate tetrahydrate. This reaction proceeds via successive thermal dehydration and decomposition occurring at different temperatures to form sodium metaborate. Each reaction process comprises several kinetic steps originating from different physicochemical and physico-geometric phenomena.

Kinetic analysis of overlapping multistep thermal decomposition comprising exothermic and endothermic processes: thermolysis of ammonium dinitramide.

This study focused on kinetic modeling of a specific type of multistep heterogeneous reaction comprising exothermic and endothermic reaction steps, as exemplified by the practical kinetic analysis of the experimental kinetic curves for the thermal decomposition of molten ammonium dinitramide (ADN). It is known that the thermal decomposition of ADN occurs as a consecutive two step mass-loss process comprising the decomposition of ADN and subsequent evaporation/decomposition of in situ generated ammonium nitrate. These reaction steps provide exothermic and endothermic contributions, respectively, to the overall thermal effect.

Multistep Kinetic Behavior of the Thermal Decomposition of Granular Sodium Percarbonate: Hindrance Effect of the Outer Surface Layer.

The kinetics and mechanism of the thermal decomposition of granular sodium percarbonate (SPC), which is used as a household oxygen bleach, were studied by thermoanalytical measurements under systematically changing conditions and morphological observation of the reactant solids at different reaction stages. A physico-geometrical kinetic behavior of the reaction that occurs in a core-shell structure composed of an outer surface layer and internal aggregates of SPC crystalline particles was illustrated through detailed kinetic analyses using the kinetic deconvolution method. Simultaneously, the hazardous nature of SPC as a combustion improver was evaluated on the basis of the kinetic behavior of the thermal decomposition.

Exothermic Behavior of Thermal Decomposition of Sodium Percarbonate: Kinetic Deconvolution of Successive Endothermic and Exothermic Processes.

This study focused on the kinetic modeling of the thermal decomposition of sodium percarbonate (SPC, sodium carbonate-hydrogen peroxide (2/3)). The reaction is characterized by apparently different kinetic profiles of mass-loss and exothermic behavior as recorded by thermogravimetry and differential scanning calorimetry, respectively. This phenomenon results from a combination of different kinetic features of the reaction involving two overlapping mass-loss steps controlled by the physico-geometry of the reaction and successive endothermic and exothermic processes caused by the detachment and decomposition of H2O2(g).