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

Kodani, Satoki; Iwasaki, Shun; Favergeon, Loïc; Koga, Nobuyoshi

doi:10.1039/d0cp00446d

Cited by 38 publications

(62 citation statements)

References 98 publications

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“…Thus, the kinetic characterization of the thermal decomposition reaction should be considered as including a determination of the influence that the partial pressure of CO 2 ( p (CO 2 ) in kPa) has on it, in addition to the changes in the reaction rate as a function of reaction temperature ( T ) and the fractional reaction (α). When considering the effect of p (CO 2 ) on the kinetics, the reaction equilibrium characterized by the equilibrium CO 2 pressure ( P eq ( T ) in atm) at each temperature should also be taken into account. − ,, The generalized reaction rate (dα/d t ) is expressed by multiplying functions expressing the dependencies on T , α, and p (CO 2 ). − where A and E a are the apparent values of the Arrhenius preexponential factor and activation energy, respectively, and R is the gas constant. The function f (α) is the kinetic model function, which describes the variation of the kinetic behavior at a constant temperature as the reaction advances.…”

Section: Introductionmentioning

confidence: 99%

“…The most frequently used form of h ( p (CO 2 ), P eq ( T )) is expressed by eq ,,,, where P ° in kPa is the standard pressure introduced to normalize the pressure unit of ( p (CO 2 )/ P °) to be in atm. Equation was obtained on the basis of various theoretical considerations. ,,,, The practical application of eq accompanied by eq corrects the slope of the Arrhenius-type plots at each p (CO 2 ) value; however, the kinetics is not necessarily described successfully by a single Arrhenius-type plot over different p (CO 2 ) values. ,− Accordingly, theoretical and experimental resolutions of the universal kinetic description of the thermal decomposition of metal carbonates over different temperature and p (CO 2 ) conditions are the current challenge for gaining further insight into the kinetics of the thermal decomposition of solids. − …”

Section: Introductionmentioning

confidence: 99%

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Universal Kinetics of the Thermal Decomposition of Synthetic Smithsonite over Different Atmospheric Conditions

et al. 2021

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The thermal decomposition of smithsonite (ZnCO 3 ) was studied to obtain a universal kinetic description of the process applicable to a range of reaction conditions. A synthesized ZnCO 3 was subjected to thermoanalytical measurements under various heating and atmospheric conditions in a flow of dry N 2 gas, or N 2 −CO 2 or N 2 −H 2 O mixed gases. Systematic shifts of the reaction temperature to higher or lower values by the effects of CO 2 or H 2 O, respectively, were identified as specific characteristics of the system. With reference to the physicogeometrical kinetic behavior of the reaction in a flow of dry N 2 gas, the retardation effect of CO 2 was demonstrated in the scheme of the physicogeometrical consecutive surface reaction (SR) and phase boundary-controlled reaction (PBR). The individual kinetics of SR and PBR were universally described over different CO 2 partial pressures using an accommodation function (AF) obtained by considering the consecutive elementary steps of SR and PBR. The catalytic effect of water vapor was assumed to result from contributions of water molecules to the consecutive elementary steps of SR and to the crystal growth of the solid product of the reaction (ZnO). An alternative AF derived considering the adsorption of water molecules on solid surfaces allowed us to obtain the universal kinetic description of the thermal decomposition over different water vapor pressures.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Universal Kinetics of the Thermal Decomposition of Synthetic Smithsonite over Different Atmospheric Conditions

et al. 2021

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“…This approach can then lead to misconceptions regarding the studied reaction because, for instance, if gases are consumed or produced during a chemical transformation, their partial pressures are likely to influence the kinetics of the process. To mitigate this issue for dehydration reactions, some authors introduce a function a P " # $ , P &' T ( of the water vapor pressure of the system P " # $ and the equilibrium pressure for the reaction P &' T to accommodate the water vapor partial pressure in the reaction rate expression 21,32,33 dα dt = A exp − E RT f α a P " # $ , P &' T (…”

Section: Introductionmentioning

confidence: 99%

“…More recently, a more general accommodation function with two P " # $ components has been obtained from the classical nucleation and interface reaction theories and applied to the formal kinetics analyses for the thermal decomposition of calcium hydroxide 18 and copper hydroxide 21 . These methods were then employed to thoroughly study the thermal decomposition of lithium sulfate monohydrate 33 and magnesium hydroxide 32 .…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of the Dehydration of Calcium Sulfate Dihydrate: A Comprehensive Approach for Studying the Dehydration of Ionic Hydrates under Controlled Temperature and Water Vapor Pressure

et al. 2020

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We studied the kinetics and mechanism of the dehydration reaction of calcium sulfate dihydrate to hemihydrate under controlled temperature and water vapor partial pressure. From kinetic and reaction rate curves obtained using TGA under isothermal and isobaric conditions, we determined the overall behavior of this dehydration reaction and the effects of the system's intensive variables on its kinetics. We observed that the reactions take place with an initial induction period that decreases with increasing temperature, followed by a sigmoidal mass loss controlled by both nucleation and growth processes. Characterization of our samples at different instants of the reaction allowed us to observe and confirm a surface nucleation process followed by isotropic growth of the nuclei with inward development of the solid product. We then employed the Mampel kinetic model based on the observed experimental results considering the physical nature of the investigated transformation and the real geometry of the particles. Form this model, we obtained sets of kinetic parameters for the nucleation and growth processes and their evolution with temperature. We then proposed physicochemical mechanisms for both processes, and they were considered to interpret the kinetic parameters obtained previously. This mechanistic analysis of the system allowed determining the effects of both temperature and water vapor pressure on the kinetic behavior of the reaction, which corresponds to a novel approach for the dehydration reaction of calcium sulfate dihydrate. The use of this universal kinetic approach to treat this chemical system.The methodology used in this work can be applied for studying the dehydration of other ionic hydrates.

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“…The kinetic data for the physico-geometrical consecutive process are recorded as macroscopically averaged data using thermoanalytical (TA) techniques. Elucidating the kinetic behavior of each physico-geometrical reaction step through kinetic analysis of the TA data of the overall process is currently a challenge. − It would enable the further detailed interpretations of the mutual relationship between the component reaction steps and the changes in the overall kinetic behavior of the thermal decomposition of solids with sample and reaction conditions. − Notably, the challenge is a necessary step to reveal the kinetics of the linear advancement of the reaction interface and the physico-chemical events occurring at the reaction interface.…”

Section: Introductionmentioning

confidence: 99%

Effects of Particle Size on the Kinetics of Physico-geometrical Consecutive Reactions in Solid–Gas Systems: Thermal Decomposition of Potassium Hydrogen Carbonate

2021

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In this study, we investigated the mechanisms of variations in the overall kinetic behavior of the physico-geometrical consecutive process of the surface reaction (SR) and phase boundary-controlled reaction (PBR) in solid−gas systems with varying particle size of the reactants. Thermal decomposition of potassium hydrogen carbonate (KHCO 3 ) was selected as a suitable model reaction owing to the significant changes in its kinetic behavior with particle size and less sensitivity to experimental conditions for recording kinetic data. The reaction was characterized by an induction period (IP) accompanied by the formation of a gelatinated surface layer. The subsequent mass-loss process was indicated by the consecutive SR and PBR, which was accompanied by the nucleation and growth of solid products in the gelatinated layer and inward advancement of the reaction interface, respectively. Formal kinetic analyses of systematically recorded kinetic data revealed variations in the overall kinetic behaviors with the sample particle size, including changes in the variation trend of isoconversional activation energy values as the reaction progressed and the shape of the experimental master plot. The kinetics of each reaction step in the physico-geometrical consecutive process was investigated using an advanced kinetic approach based on an IP−SR−PBR model. The results revealed variations in the overall kinetic behaviors of the thermal decomposition of KHCO 3 with particle size, owing to changes in the reactivity of the reactant surface in IP, overlapping degree of SR and PBR, and total migration length of the reaction interface in PBR.

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

Abstract: Kinetic features of the thermal decomposition of Mg(OH)2 are revealed under different heating and water vapor pressure conditions.

Cited by 38 publications

References 98 publications

Universal Kinetics of the Thermal Decomposition of Synthetic Smithsonite over Different Atmospheric Conditions

Universal Kinetics of the Thermal Decomposition of Synthetic Smithsonite over Different Atmospheric Conditions

Kinetics and Mechanism of the Dehydration of Calcium Sulfate Dihydrate: A Comprehensive Approach for Studying the Dehydration of Ionic Hydrates under Controlled Temperature and Water Vapor Pressure

Effects of Particle Size on the Kinetics of Physico-geometrical Consecutive Reactions in Solid–Gas Systems: Thermal Decomposition of Potassium Hydrogen Carbonate

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