Molecular dynamics study on thermal dehydration process of epsomite (MgSO<sub>4</sub>·7H<sub>2</sub>O)

Zhang, H Huaichen; Iype, Eldhose; Nedea, SV Silvia; Rindt, Ccm Camilo

doi:10.1080/08927022.2013.854891

Cited by 19 publications

(18 citation statements)

References 28 publications

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“…The H 2 O transport through MgCl 2 ÁH 2 O and MgCl 2 Á2H 2 O is investigated using ReaxFF-MD simulations. The diffusion coefficient (DC) of H 2 O through MgCl 2 hydrates are reported from Green-Kubo method at various temperature ranging from 300-500 K. The DC of H 2 O in the present study is of the same order of magnitude as the DC of H 2 O in MgSO 4 Á7H 2 O obtained both from MD simulations 49 and experiments. 50 The DC increases with temperature and follows the Arrhenius law for MgCl 2 ÁH 2 O and MgCl 2 Á2H 2 O.…”

Section: Reaxff-md Simulations Of Mgcl 2 Hydratessupporting

confidence: 68%

“…The hydrolysis 48 In the lack of experimental study for the diffusion of H 2 O through MgCl 2 hydrates, we compared with the H 2 O diffusivity through other TCM epsomite (MgSO 4 Á7H 2 O). 49 Zhang et al 49 has reported the same order of magnitude for the diffusivity of H 2 O in the center of the MgSO 4 .7H 2 O. Donkers et al 50 has measured the DC of water in epsomite using NMR. They reported the DC in range of 10 À10 to 10 À9 m 2 s À1 in the temperature range of 293 to 413 K. In the light of their experimental and simulation results of water diffusion in other heat storage material (MgSO 4 Á7H 2 O), we can conclude that the present ReaxFF-MD simulations could mimic the water transport in MgCl 2 hydrates.…”

Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 92%

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Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Pathak¹,

Nedea²,

Duin

et al. 2016

Phys. Chem. Chem. Phys.

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MgCl2 hydrates are considered as high-potential candidates for seasonal heat storage materials. These materials have high storage capacity and fast dehydration kinetics. However, as a side reaction to dehydration, hydrolysis may occur. Hydrolysis is an irreversible reaction, which produces HCl gas thus affecting the durability of heat storage systems. In this study, we present the parameterization of a reactive force field (ReaxFF) for MgCl2 hydrates to study the dehydration and hydrolysis kinetics of MgCl2·H2O and MgCl2·2H2O. The ReaxFF parameters have been derived by training against quantum mechanics data obtained from Density Functional Theory (DFT) calculations consisting of bond dissociation curves, angle bending curves, reaction enthalpies, and equation of state. A single-parameter search algorithm in combination with a Metropolis Monte Carlo algorithm is successfully used for this ReaxFF parameterization. The newly developed force field is validated by examining the elastic properties of MgCl2 hydrates and the proton transfer reaction barrier, which is important for the hydrolysis reaction. The bulk moduli of MgCl2·H2O and MgCl2·2H2O obtained from ReaxFF are in close agreement with the bulk moduli obtained from DFT. A barrier of 20.24 kcal mol(-1) for the proton transfer in MgCl2·2H2O is obtained, which is in good agreement with the barrier (19.55 kcal mol(-1)) obtained from DFT. Molecular dynamics simulations using the newly developed ReaxFF on 2D-periodic slabs of MgCl2·H2O and MgCl2·2H2O show that the dehydration rate increases more rapidly with temperature in MgCl2·H2O than in MgCl2·2H2O, in the temperature range 300-500 K. The onset temperature of HCl formation, a crucial design parameter in seasonal heat storage systems, is observed at 340 K for MgCl2·H2O, which is in agreement with experiments. The HCl formation is not observed for MgCl2·2H2O. The diffusion coefficient of H2O through MgCl2·H2O is lower than through MgCl2·2H2O, and can become a rate-limiting step. The diffusion coefficient increases with temperature and follows the Arrhenius law both for MgCl2·H2O and MgCl2·2H2O. These results indicate the validity of the ReaxFF approach for studying MgCl2 hydrates and provide important atomistic-scale insight of reaction kinetics and H2O transport in these materials.

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Section: Reaxff-md Simulations Of Mgcl 2 Hydratessupporting

confidence: 68%

Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 92%

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Pathak¹,

Nedea²,

Duin

et al. 2016

Phys. Chem. Chem. Phys.

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“…Due to the lack of information of Li 2 SO 4 ÁH 2 O, the diffusivity of water diffusion in solid MgSO 4 Á7H 2 O is used for comparison. It was calculated by using molecular dynamic simulations that the diffusion coefficients in the center are in the order of 10 À10 m 2 s À1 , while those near the surface are in the order of 10 À9 m 2 s À1 [33]. Generally, it is recognized that diffusion in the solid crystal is a function of crystal structure and temperature.…”

Section: Comparison With Experimental Resultsmentioning

confidence: 99%

An experimentally validated numerical model of interface advance of the lithium sulfate monohydrate dehydration reaction

Lan

Steenhoven

Rindt

2016

J Therm Anal Calorim

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Interface advance plays an essential role in understanding the kinetics and mechanisms of thermal decomposition reactions such as the dehydration reaction of lithium sulfate monocrystals. However, many fundamental processes including mass transfer during interface advance are still not clear. In this work, the dynamics of interface advance, involving interaction between interfacial reaction and mass diffusion, is investigated numerically together with microscopy observations. A mathematical model is developed for interface advance with a moving boundary and then solved by using a conservative scheme. To examine the significance between the intrinsic chemical reaction and mass diffusion, a Damköhler number is defined as Da ¼ k r L=ðD e c 0 Þ. Numerical results at various Da values are discussed to distinguish the limiting step of the dehydration reaction of lithium sulfate monocrystals. Moreover, experiments are carried out with a hot-stage microscopy system where the propagation of the reaction interface into the crystal bulk is followed in situ. By fitting the experimental results with the numerical results, the effective diffusivity of water through the dehydrated crystal is estimated to be in the order of 10 À8 m 2 s À1 . According to the corresponding Da values, it is found that, within the reaction temperature ranging from 110 to 130°C and a partial water vapor pressure of 13 mbar, the rate of dehydration interface advance in the bulk of large crystals (typically in the order of millimeters) is not constant, but shows a small decrease over time due to the influence of mass diffusion.

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“…47 As long as the sorption dynamics is not affected by the gas transfer or the diffusion in the pore of porous adsorbent, the sorption equilibrium can be quickly established. 56 In simulation and experiment, the pore structure of porous materials is studied by physical adsorption.…”

Section: Revealing Sorption Mechanism By Microscale Simulationmentioning

confidence: 99%

Study on the sorption mechanism of middle‐low temperature sorption thermal storage materials from the microscale simulation: A review

2021

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Middle-low temperature sorption thermal storage materials (STSMs), which are widely applied in the waste heat utilization, can overcome the mismatch of thermal energy between supply and consumption. Many researchers have paid more attention to its complicated mechanism, particularly in the chemisorption process. Unlike the scientific experiment, microscale simulation has an immerse advantage of its low costs, high security, and high precision, which exploring the sorption mechanism at a molecular level. In this review, the microscale simulation method and its application in researching the sorption mechanism are summarized. We mainly stuck in three commonly microscale simulation methods: density functional theory, molecular dynamics, and Monte Carlo method. The diffusion, sorption isotherm and sorption heat, sorption dynamics, chemical reaction pathways, and structural stability are comprehensively examined, which illustrating how the interaction between adsorbate and adsorbent influences the properties of kinetics, thermodynamics, chemistry, and structure.Updating the algorithm, developing the multiscale simulation, establishing a database is promising to extend its application range of design the novel STSMs. Furthermore, as a smart bottom-up method for designing materials, combing with experiment, theoretical calculation, and other burgeoning technology will shorten the time cycle from development to market.

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Molecular dynamics study on thermal dehydration process of epsomite (MgSO₄·7H₂O)

Cited by 19 publications

References 28 publications

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

An experimentally validated numerical model of interface advance of the lithium sulfate monohydrate dehydration reaction

Study on the sorption mechanism of middle‐low temperature sorption thermal storage materials from the microscale simulation: A review

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Molecular dynamics study on thermal dehydration process of epsomite (MgSO4·7H2O)

Cited by 19 publications

References 28 publications

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

An experimentally validated numerical model of interface advance of the lithium sulfate monohydrate dehydration reaction

Study on the sorption mechanism of middle‐low temperature sorption thermal storage materials from the microscale simulation: A review

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Molecular dynamics study on thermal dehydration process of epsomite (MgSO₄·7H₂O)