Two-component water sorbent with mesoporous ordered matrix and calcium chloride was prepared by wet impregnation. The composite has ordered mesoporous structure with 2D-hexagonal pore arrangement and maintain its structure after the wet impregnation with calcium chloride solution. The ordered two-composite water adsorbent and the matrix reveal high water uptakes. The ordered two-component composite is rather low hydrophilic adsorbent. For significant improvement of the hydrophilic character higher amount of calcium chloride in the matrix is needed. At present the composite for the application within adsorption heat storage is still too hydrophobic, since the major water uptake occurs only at relative pressure above 0.6. However, by wet impregnation, a successful shift of the isotherm to lower relative pressure was achieved. Since the overall volume was only slightly reduced by the impregnation, this is the first promising step which shows the principle possibility towards further optimization of this two-component water sorbent material.
COBISS.SI-ID: 4977690
The authors have developed a mechanism that predicts the heat storage potential of numerous known or new microporous aluminophosphates. The utilisation of the reversible chemical and physical sorption of water on solids provides a new long-term thermal energy storage concept, also in combination with solar thermal collectors. However, up to now there have been no systematic studies of the possible mechanisms for heat storage enhancement concerning materials optimisation. Based on a comparative thermogravimetric and calorimetric study of water sorption in small-pore aluminophosphate materials (SAPO-34, AlPO4-18 and APO-Tric) the authors proposed that the formation of highly ordered water clusters in the pores is a driving force for a sudden water uptake in a narrow relative pressure range, which is a prerequisite for their use in storage systems and crucially determines their sorption efficiency. The formation of clusters is enabled by rapid and reversible changes in the framework aluminium coordination and optimal pore diameters.
COBISS.SI-ID: 4910618
A new two-component (composite) water sorbent CaCl2-FeKIL2 has been developed for sorption-based solar thermal energy storage. The matrix of the composite is FeKIL2 material with disordered mesopores, high surface area of 712 m2/g and mesopore dimensions between 4 and 29 nm. The composite, prepared by wet impregnation of FeKIL2 with CaCl2, has lower surface area (418 m2/g) and similar mesopore dimensions as the matrix. The maximum water sorption capacityof FeKIL2 is 0.21 g/g, while the composite possesses 3 times higher maximum water sorption capacity due to the presence of the salt in the matrix.Heat of adsorption of the composite is 50.4 kJ/mol. A short-term cycling test between temperatures of 150 and 40 °C at a water vapour pressure of 5.6 kPa confirms a comparatively good hydrothermal stability of the composite
COBISS.SI-ID: 5034778
Hydrothermal stability of Zn2(BTC)(OH)(H2O)•1.67H2O is its unique property, since almost all zinc carboxylates are unstable even in the presence of water in traces. We showed that the reason for high chemical stability towards water lay in the presence π-π interaction between aromatic rings and in the fact that inorganic chains are stabilized by strong hydrogen-bonds between coordinated water in ZnO4(OH)(H2O) units and free water molecules located between the vertices of octahedra. The adsorption and desorption processes were monitored by in situ NMR and IR spectroscopy.
COBISS.SI-ID: 5277722
Aluminophosphate APO-tric is a novel adsorption material for thermal energy storage. APO-tric is a microporous triclinic chabazite material with ordered microporous 3-dimensional channel structure. The framework is very flexible which increases the possibility of water adsorption into the structure. During adsorption of water molecules the chabazite structure is modified. This deformation is however completely reversible and can be eliminated by dehydration at 120°C. The material shows a very good thermal stability up to 900°C and a water adsorption capacity up to 0.32 g/g.
COBISS.SI-ID: 4507674