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Thermal stability, hydrolysis and thermodynamic properties of molten KCl-CuCl

Niazi, Sepideh and Bonk, Alexander and Hanke, Andrea and to Baben, Moritz and Reis, Bruno and Olsen, Espen and Nygard, Heidi S. (2021) Thermal stability, hydrolysis and thermodynamic properties of molten KCl-CuCl. Materialia (21), p. 101296. Elsevier. doi: 10.1016/j.mtla.2021.101296. ISSN 2589-1529.

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Official URL: https://www.sciencedirect.com/science/article/pii/S2589152921002982


KCl-CuCl is known as an inorganic salt mixture with a particularly low melting point, below 200 °C. There are very few studies published investigating this binary system. In this study KCl-CuCl is considered as a candidate for liquifying biomass as a pre-step before a high pressure and temperature (40-50 bar, 450-500 °C) hydro-pyrolysis process. Its low melting point makes it a good candidate to liquify biomass at mild conditions (low temperature and pressure) and avoid producing char and ash. Thermal stability and stability against hydrolysis have been measured for compositions close to the eutectic composition up to 500 °C. The results show that KCl-CuCl is thermally stable, and no mass loss was observed up to 500 °C. Moreover, it is chemically stable in contact with water and no HCl was detected in hydrolysis experiments. In addition, the modelling of the system was studied. Although there is a phase diagram for this system in the literature based on the experimental data, no thermodynamic parameters have been calculated for this system and no database was found for KCl-CuCl solution. Therefore, Calphad modelling of the binary KCl-CuCl molten salt is performed in this study and FactSage is employed to assess the thermodynamic parameters and generate the phase diagram. For this purpose, a series of experiments have been carried out to investigate transition points and thermodynamic properties of mixtures between 40 and 80 mol% of CuCl by cooling curve and differential scanning calorimetry. The intermediate compound K2CuCl3 is considered stoichiometric, and its Gibbs energy modelling relies on ab initio calculated enthalpy of reaction from the base salts and optimization of the standard entropy. The liquid solution is modelled with a subregular solution model using Redlich-Kister polynomials. The phase diagram of the system is generated based on thermodynamic data and experimental results. The results show that the predicted eutectic point of the binary system is located at T = 145.9 °C and 64.9 CuCl mol%. The calculated results are in excellent agreement with the measured values. The high thermal stability and stability against hydrolysis qualify eutectic KCl-CuCl mixtures as promising molten salt for biomass liquefaction. However, corrosion limits the choice of possible reactor materials.

Item URL in elib:https://elib.dlr.de/148151/
Document Type:Article
Title:Thermal stability, hydrolysis and thermodynamic properties of molten KCl-CuCl
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Bonk, AlexanderAlexander.Bonk (at) dlr.dehttps://orcid.org/0000-0002-0676-7267
Hanke, AndreaAndrea.Hanke (at) dlr.dehttps://orcid.org/0000-0002-4137-7985
Date:8 December 2021
Journal or Publication Title:Materialia
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.mtla.2021.101296
Page Range:p. 101296
Keywords:Molten salts KCl-CuCl Modelling Phase diagram Calphad
HGF - Research field:Energy
HGF - Program:Materials and Technologies for the Energy Transition
HGF - Program Themes:High-Temperature Thermal Technologies
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Thermochemical Processes
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Thermal Process Technology
Deposited By: Bonk, Alexander
Deposited On:11 Jan 2022 09:50
Last Modified:11 Jan 2022 09:50

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