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Stefan Hiebler - One of the best experts on this subject based on the ideXlab platform.
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calorimetric and theoretical determination of the concentration dependent enthalpy change around cabr2 6h2o
Thermochimica Acta, 2015Co-Authors: Henri Schmit, Werner Pfeffer, Simon Pollinger, Stefan HieblerAbstract:Abstract In large latent heat storages based with the phase change material (PCM) being a Salt Hydrate, it is difficult to assure the stoichiometrically correct Hydrate concentration of the Salt Hydrate. In this study the impact of the concentration of CaBr2 + H2O in a concentration range of about 2.6 wt% around the congruent melting CaBr2·6H2O on the melting enthalpy and the maximum storage capacity is exemplary investigated via differential scanning calorimetry (DSC) and via a model. The melting enthalpy of CaBr2·6H2O is found to be 142.1 J g−1, which is significantly larger than the value indicated in literature (115.5 J g−1). For a CaBr2 concentration around 0.8 wt% lower than the concentration of CaBr2·6H2O, a decrease of over 17% is found for both the melting enthalpy and the maximum storage capacity. A good agreement is found for the maximum storage capacity between the experimentally determined values and the values determined by the model.
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experimental investigation of the concentration dependent maximum storage capacity of two inorganic phase change materials
Energy Procedia, 2015Co-Authors: Henri Schmit, Werner Pfeffer, Christoph Rathgeber, Stefan HieblerAbstract:Abstract In large latent heat storages with the phase change material (PCM) being a Salt Hydrate, it is difficult to assure the stoichiometrically correct Hydrate concentration of the Salt Hydrate. In this study, the influence of the composition of CaBr 2 + H 2 O around the congruent melting CaBr 2 ·6H 2 O and CaCl 2 + H 2 O around the semi-congruent melting CaCl 2 ·6H 2 O on the maximum storage capacity is investigated via differential scanning calorimetry (DSC). For a CaBr 2 concentration around 0.8 wt% lower than the concentration of CaBr 2 ·6H 2 O, a decrease of over 17% is found for the maximum storage capacity. For a CaCl 2 concentration around 0.7 wt% lower than the concentration of CaCl 2 ·6H 2 O, a decrease of over 11% is found for the maximum storage capacity. While reproducible results for the maximum storage capacity for samples of the same concentration of CaBr 2 + H 2 O are obtained via DSC, this is not the case for the CaCl 2 + H 2 O samples. Thus, the difficulty to measure representative enthalpy curves of non-congruent melting Salt Hydrates via DSC is shown.
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Thermal performance of sodium acetate triHydrate thickened with different materials as phase change energy storage material
Applied Thermal Engineering, 2003Co-Authors: Luisa F. Cabeza, Gustav Svensson, Stefan Hiebler, Harald MehlingAbstract:The use of phase change materials (PCMs) in energy storage has the advantage of high energy density and isothermal operation. Although the use of only non-segregating PCMs is a good commercial approach, some desirable PCM melting points do not seem attainable with non-segregating Salt Hydrates at a reasonable price. The addition of gellants and thickeners can avoid segregation of these materials. In this paper, sodium acetate triHydrate is successfully thickened with bentonite and starch. Cellulose gives an even better thickened PCM, but temperatures higher than 65 °C give phase separation. The mixtures would show a similar thermal behavior as the Salt Hydrate, with the same melting point and an enthalpy decrease between 20% and 35%, depending on the type and amount of thickening material used.
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middle term immersion corrosion tests on metal Salt Hydrate pairs used for latent heat storage in the 32 to 36 c temperature range
Materials and Corrosion-werkstoffe Und Korrosion, 2001Co-Authors: L F Cabeza, Stefan Hiebler, Harald Mehling, J Illa, J Roca, F Badia, F ZieglerAbstract:Efficient energy storage is one of the biggest problems facing alternative energy technologies. In whatever form the energy is stored, an alternative energy system usually requires a storage buffer between carrying energy input and the varying energy demand regime at the output end of the system. A method of energy storage is the use of the latent heat from Phase Change Materials (PCMs), for example Salt Hydrates. In this paper we tested the corrosion resistance of five commercial metals (aluminum, brass, copper, steel and stainless steel) in contact with two Salt Hydrates, commonly used as PCM, with a melting temperature in the range of 48 to 58°C (sodium acetate triHydrate and sodium thiosulfate pentaHydrate) in experiments with a duration up to 70 days. The results demonstrated that brass and copper should be avoided when sodium acetate triHydrate is used in long term applications, but aluminum, steel and stainless steel can be used without problem. When the Salt Hydrate used is sodium thiosulfate pentaHydrate, brass and copper should not be used in any case, aluminum and stainless steel can be used, and steel in contact with graphite should be monitored because corrosion could appear after some time of use.
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immersion corrosion tests on metal Salt Hydrate pairs used for latent heat storage in the 32 to 36 c temperature range
Materials and Corrosion-werkstoffe Und Korrosion, 2001Co-Authors: Luisa F. Cabeza, Stefan Hiebler, Harald Mehling, J Illa, J Roca, F Badia, F ZieglerAbstract:Efficient energy storage is one of the biggest problems facing alternative energy technologies. In whatever form the energy is stored, an alternative energy system usually requires a storage buffer between carrying energy input and the varying energy demand regime at the output end of the system. A method of energy storage is the use of the latent heat from Phase Change Materials (PCMs), for example Salt Hydrates. In this paper we tested the corrosion resistance of five commercial metals (aluminum, brass, copper, steel and stainless steel) in contact with two Salt Hydrates, commonly used as PCM, with a melting temperature in the range of 48 to 58°C (sodium acetate triHydrate and sodium thiosulfate pentaHydrate) in experiments with a duration up to 70 days. The results demonstrated that brass and copper should be avoided when sodium acetate triHydrate is used in long term applications, but aluminum, steel and stainless steel can be used without problem. When the Salt Hydrate used is sodium thiosulfate pentaHydrate, brass and copper should not be used in any case, aluminum and stainless steel can be used, and steel in contact with graphite should be monitored because corrosion could appear after some time of use.
Michiel Makkee - One of the best experts on this subject based on the ideXlab platform.
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Sorbitol dehydration in a ZnCl2 molten Salt Hydrate medium: molecular modeling
Catal. Sci. Technol. 2014 4 152, 2013Co-Authors: Wim Buijs, Jacob A. Moulijn, Rob J. Berger, Michiel MakkeeAbstract:A molecular modelling study, using standard DFT B3LYP/6-31G*, was carried out to develop a better understanding of sorbitol dehydration into isosorbide in ZnCl2 molten Salt Hydrate medium. Catalysis of sorbitol dehydration by ZnCl2 most likely starts with complexation of the sugar alcohol functions to Zn, followed by an internal SN2 mechanism of a secondary alcohol function attacking a primary alcohol function with the Zn-complex acting as a favourable leaving group. The dehydration reactions to 1,4- and 3,6-anhydrosorbitol show a very similar activation barrier in good accordance with experimental results. The same holds for the formation of isosorbide from 1,4- and 3,6-anhydrosorbitol, albeit with a slightly higher activation barrier. The relative level of the activation barriers reflects the increased strain in the sorbitol skeleton in the corresponding transition states. ZnCl2 turns the dehydration reaction from an endothermic one to an exothermic one by forming a strong complex with the released water. Finally, the ZnCl2–H2O system has been compared with HCl–H2O, which could have been an alternative; it, however, turned out not to be the case.
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sorbitol dehydration into isosorbide in a molten Salt Hydrate medium
Catalysis Science & Technology, 2013Co-Authors: Jianrong Li, Jacob A. Moulijn, Antonio Spina, Michiel MakkeeAbstract:The sorbitol conversion in a molten Salt Hydrate medium (ZnCl2; 70 wt% in water) was studied. Dehydration is the main reaction, initially 1,4- and 3,6-anhydrosorbitol are the main products that are subsequently converted into isosorbide; two other anhydrohexitols, (1,5- and 2,5-), formed are in less amounts and do not undergo further dehydration. Besides dehydration, depending on the temperature, sorbitol was partly epimerized into galactitol, which was further converted to anhydrohexitols or di-anhydrohexitols (mainly isoidide). Epimerization of galactitol into sorbitol was not observed. Temperature (150 to 220 °C) is a crucial factor; at low temperature the reaction rate is low but the selectivity is high, at elevated temperature (over 200 °C) the rate is high but extensive amounts of byproducts were produced. At the optimal temperature range, without using any co-catalysts, full conversion is achieved, and the isosorbide percent yield is above 85% on a molar basis; (1,5- and 2,5-) anhydrohexitols are the major byproducts. The sorbitol conversion reaction pathway has been investigated.
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simultaneous hydrolysis and hydrogenation of cellobiose to sorbitol in molten Salt Hydrate media
Catalysis Science & Technology, 2013Co-Authors: Helena S M P Soares, J A Moulijn, Michiel MakkeeAbstract:The hydrolysis and hydrogenation of cellobiose (4-O-b-D-glucopyranosyl-D-glucose) in ZnCl2_4H2O solvent was studied to optimize the conditions for conversion of lignocellulose (the most abundant renewable resource) into sorbitol (D-glucitol). Water at neutral pH does not allow hydrolysis of cellobiose under the conditions of the experiments (up to 125 1C, 4 h), but relatively fast hydrogenation of cellobiose into 3-b-D-glucopyranosyl-D-glucitol over a Ru/C catalyst in the presence of H2 takes place. In ZnCl2_4H2O hydrolysis does take place in the range of temperatures studied (75–125 1C) and simultaneously hydrogenation (H2, Ru/C), though at a lower rate than that in neutral water. Thus, a one-pot conversion of cellobiose into sorbitol is possible. The hydrolysis is the rate limiting reaction, but the selectivity to sorbitol is determined by the rate of hydrogenation. Under optimal conditions the yield of sorbitol is Z95%. The kinetic pathways are discussed.
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Cellulose Conversion to Isosorbide in Molten Salt Hydrate Media
ChemSusChem, 2010Co-Authors: Rafael Menegassi De Almeida, Christian Nederlof, Paul O'connor, Michiel Makkee, Jacob A. MoulijnAbstract:Effective ways to convert lignocellulosic biomass are of universal interest. 2] Such biomass contains typically around 40 wt% of cellulose, a polymer of d-glucose condensed by glycosidic bonds. Intramolecular and intermolecular hydrogen bonding networks result in a partially crystalline, non-accessible supramolecular structure, making conversion a challenge. Cellulose can be depolymerized in high severity thermochemical processes such as hydrothermal liquefaction and fast pyrolysis. In hydrothermal liquefaction, temperatures higher than 3008C are necessary to loosen the crystalline structure into amorphous cellulose that promptly hydrolyzes. In addition to energy requirements in such severe conditions, monosaccharides (such as glucose) are very reactive, leading to a multitude of products. 2,5, 6] From a practical standpoint, this process is not attractive for producing chemicals or transportation fuels. There is a need for effective chemical conversion processes at mild conditions. Acid hydrolysis of cellulose and hemicellulose to monosaccharides at lower temperatures can be enhanced in proper medium, in particular, some molten Salt Hydrates. Molten Salt Hydrates such as ZnCl2, CaCl2, and LiCl are able to solubilize cellulose due to the interaction between ionic species and hydroxyls, breaking the hydrogen-bonding network. Processing sugarcane bagasse and fast cellulose to glucose conversion of up to 98% were reported. However, the next step, separation of the polar monosaccharides, is troublesome, which requires expensive methods such as electrodialysis or chromatography. This discourages the industrial implementation of hydrolysis in a molten Salt Hydrate medium. An alternative would be the further conversion of glucose to a more easily separable compound. Some authors proposed the hydrolysis of cellulose and dehydration of glucose to 5-hydroxymethylfurfural (HMF) and derivatives using dissolution and hydrolysis media such as organic cation ionic liquids ([EMIM]Cl with CuCl2 and CrCl2) [12] , dissolution media such as LiCl in HCl (chlorinated compounds are byproducts) and DMA with LiCl. A disadvantage of these processes is that HMF is quite reactive in acidic media, leading to soluble degradation products and insoluble humins. The conversion process described in this paper aims to solve the difficulties of cellulose non-accessibility and monosaccharides reactivity by effecting hydrolysis, hydrogenation, and further conversion in the same Salt Hydrate dissolution media, resulting in a less polar, recoverable, stable compound. The proposed concept is shown in Scheme 1 for lignocellulosic bio-
Xianglin Hou - One of the best experts on this subject based on the ideXlab platform.
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nmr insights into the unexpected interaction of sncl4 with d glucosamine and its effect on 5 hmf preparation in zncl2 molten Salt Hydrate medium
ChemistrySelect, 2016Co-Authors: Yingxiong Wang, Christian Pedersen, Yan Qiao, Chunyan Chen, Lingyu Jia, Shiyu Jia, Xiaoya Guo, Xianglin HouAbstract:SnCl4, a versatile Lewis acid catalyst in the biomass conversion, plays a positive role for the cellulose biomass conversion but negative for chitin biomass conversion as realized in our previous research. In this report, the unexpected effects of SnCl4 on the conversion of d-glucosamine (GlcNH2) to 5-hydroxymethylfurfural (5-HMF) in ZnCl2 molten Salt Hydrate medium were investigated. The strong interaction between SnCl4 and GlcNH2 in ZnCl2 molten Salt Hydrate medium was examined by nuclear magnetic resonance (NMR) techniques. Additionally the d-glucose and N-acetyl-d-glucosamine were also utilized in NMR titration experiments to reveal the complexation of amino group with Sn4+ ions during the catalytic process. The observed drifts of chemical shifts and signal broadening of the C2 position of GlcNH2 in 13C NMR spectra indicates that the amino group in GlcNH2 is probably the Sn4+ ion complexation site. The correlations in the 1H-15N HSQC NMR spectra provide the direct evidence and further confirm that the amino group is the complexation site between SnCl4 and GlcNH2. This very specific complex between the amino group and the Sn4+ ion inhibit the conversion of GlcNH2 to 5-HMF in ZnCl2 molten Salt Hydrate medium.
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in situ nmr spectroscopy inulin biomass conversion in zncl2 molten Salt Hydrate medium sncl4 addition controls product distribution
Carbohydrate Polymers, 2015Co-Authors: Yingxiong Wang, Christian Pedersen, Yan Qiao, Tiansheng Deng, Jing Shi, Xianglin HouAbstract:Abstract The dehydration of inulin biomass to the platform chemicals, 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA), in ZnCl2 molten Salt Hydrate medium was investigated. The influence of the Lewis acid catalyst, SnCl4, on the product distribution was examined. An in situ 1H NMR technique was employed to follow the reaction at the molecular level. The experimental results revealed that only 5-HMF was obtained from degradation of inulin biomass in ZnCl2 molten Salt Hydrate medium, while the LA was gradually becoming the main product when the reaction temperature was increased in the presence of the Lewis acid catalyst SnCl4. In situ NMR spectroscopy could monitor the reaction and give valuable insight.
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nmr insights on the properties of zncl2 molten Salt Hydrate medium through its interaction with sncl4 and fructose
ACS Sustainable Chemistry & Engineering, 2014Co-Authors: Yan Qiao, Yingxiong Wang, Christian Pedersen, Xianglin HouAbstract:The solvent properties of ZnCl2 molten Salt medium and its synergic effect with the Lewis acid catalyst, Sn4+, for biomass conversion, were investigated by nuclear magnetic resonance. The tautomeric distribution of fructose in the ZnCl2 molten Salt medium was examined, and its effect for humins formation during the biomass conversion was evaluated. The ion complex composed by Sn4+ and Zn2+ indicated that there is a synergic catalytic effect between these two Lewis acid ions. 13C NMR spectra of fructose in different ZnCl2 molten Salt Hydrate concentrations revealed that the concentration of β-furanose and α-furanose tautomers, which lead to 5-HMF, were significantly decreased with increased Salt concentration. Meanwhile the β-pyranose tautomer, which is correlated with humins formation, was increased significantly.
Zhengguo Zhang - One of the best experts on this subject based on the ideXlab platform.
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Salt Hydrate expanded vermiculite composite as a form stable phase change material for building energy storage
Solar Energy Materials and Solar Cells, 2019Co-Authors: Zhongping Li, Zhaowen Huang, Yutang Fang, Zhengguo ZhangAbstract:Abstract An investigation on a new type of shape-stabilized phase change material (PCM) prepared by impregnating eutectic Salt Hydrate (Na2SO4·10H2O-Na2CO3·10H2O with 1:1 in mass ratio) into expanded vermiculite (EV) is carried out in this study. The maximum mass percentage of Na2SO4·10H2O-Na2CO3·10H2O eutectic within the composite is determined as 60%. The chemical composition of EV is measured by X-Ray Fluorescence Spectrometer (XRF). The specific surface area of EV and raw vermiculite (RV) is characterized by Brunauer-Aemmett-Teller (BET) method. The results from Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) tests reveal that eutectic Salt Hydrate fully filled in the multilayer structure of EV and had good compatibility among the components of the composites. The phase change temperature and the melting enthalpy of the composites are 23.98 °C and 110.3 J/g respectively, which are measured by differential scanning calorimetry (DSC). Good thermal and structural reliability are also demonstrated by thermal gravimetric analysis (TG) techniques and thermal cycling tests. Moreover, the low thermal conductivity with 0.192 W/ (m K) tested by the Hot Disk via transient plane source method certifies that the composite is very applicable for insulation. The composite PCM is then tested in a reduced-scale test chamber outfitted with four thin PCM panels as insulated wallboards. The indoor temperature variations of the PCM room is compared with another identical chamber without PCM layer for evaluating the thermal regulating performance. The results show that the composite has the function of maintaining the indoor temperature at a comfortable range for a longer period and distinctly influenced the time delay. All analysis results indicate that the low-cost Salt Hydrate/EV composite can exert a great deal of influence on insulation in building energy conservation.
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a calcium chloride hexaHydrate expanded perlite composite with good heat storage and insulation properties for building energy conservation
Renewable Energy, 2017Co-Authors: Qianhao Wang, Xiaoming Fang, Zhengguo ZhangAbstract:A porous supporting matrix, expanded perlite (EP) is composited with a Salt Hydrate mixture of CaCl2·6H2O and SrCl2·6H2O (98:2 in mass ratio), to develop a nonflammable thermal storage material for building use. The Salt Hydrate is uniformly adsorbed on sheets of EP, and a maximum absorption capacity test shows EP can contain as high as 55 wt% the Salt Hydrate and keep the stable form. It is shown that the melting temperature of the composite PCM is 27.38 °C, close to that of CaCl2·6H2O, and its latent heat is 87.44 J/g, equivalent to the calculated value based on the mass fraction of CaCl2·6H2O in the composite. EP further reduces the Salt Hydrate thermal conductivity by over 70% to enhance its thermal insulation, and suppresses the supercooling. A 1000 heating-cooling cycles test verifies the CaCl2·6H2O/EP composite possesses good thermal reliability. The CaCl2·6H2O/EP composite is then fabricated into a board for replacing the foam board employed as the core in a commercial foam insulating brick to obtain a PCM brick. It is found that, when applied as the roof of a test room, the PCM brick has the function of decreasing the indoor peak temperature and causing the hysteresis in the indoor temperature rise, compared with the foam insulation brick. The nonflammability along with good thermal storage and insulation properties makes the CaCl2·6H2O/EP composite PCM show great promises for use in building energy conservation.
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Inorganic Salt Hydrate for Thermal Energy Storage
Applied Sciences, 2017Co-Authors: Ning Xie, Zigeng Luo, Zhaowen Huang, Yutang Fang, Xuenong Gao, Zhengguo ZhangAbstract:Using phase change materials (PCMs) for thermal energy storage has always been a hot topic within the research community due to their excellent performance on energy conservation such as energy efficiency in buildings, solar domestic hot water systems, textile industry, biomedical and food agroindustry. Several literatures have reported phase change materials concerning various aspects. Among these materials, Salt Hydrates are worthy of exploring due to their high-energy storage density, rational price, multiple sources and relatively good thermal conductivity. This paper reviews the present state of Salt Hydrates PCMs targeting classification, properties, defects, possible solutions as well as their idiographic features which are suitable for applications. In addition, new trends of future research are also indicated.
Paul A Kohl - One of the best experts on this subject based on the ideXlab platform.
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the deposition characteristics of accelerated nonformaldehyde electroless copper plating
Journal of The Electrochemical Society, 2003Co-Authors: Jun Li, Paul A KohlAbstract:The deposition process of an electroless copper plating solution using sodium citrate as the main complexing agent and sodium hypophosphite as the reducing agent has been investigated. The deposit composition, structure, and catalytic activity for the oxidation of hypophosphite during the process have been investigated. Formamidine disulfide (fd) has been shown to accelerate the deposition rate of the electroless plating just as it does with electroless plating solutions using N-(2-hydroxyethyl)ethylenediaminetriacetic acid trisodium Salt Hydrate (HEDTAI as the complexing agent. For solutions with the Cu 2+ /Ni 2+ mole ratio of 42, the deposition rate decreased with time and terminated after 90 min plating because the surface catalytic activity of the deposit had decreased with thickness. A copper deposit with total thickness of 6.48-6.59 μm was obtained after 90 min plating. The decrease in the deposition rate with time was mitigated by decreasing the Cu 2+ /Ni 2+ mole ratio, holding the concentration of copper ions constant. An optimized electroless copper plating process with sustained deposition rate with time and high metal conductivity was developed. The bath was used in a fully additive high density wiring process.
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the acceleration of nonformaldehyde electroless copper plating
Journal of The Electrochemical Society, 2002Co-Authors: Jun Li, Paul A KohlAbstract:Nonformaldehyde, low pH (compared to highly alkaline bath) electroless copper plating has been investigated. Thiourea and its derivatives have been shown to increase the deposition rate of electroless copper plating solutions using HEDTA [N-(2-hydroxyethyl)ethylenediaminetriacetic acid trisodium Salt Hydrate] as the complexing agent and sodium hypophosphite as the reducing agent. A thiourea concentration of 1.0 ppm produced a fourfold increase in the deposition rate of copper from about 1 to 4 μm/h. The effect of thiourea on the electrochemical reactions, and the crystal structures and electrical properties of the copper deposits were examined. A small amount of thiourea, or its derivatives, in the electroless copper solution improves the catalytic activity of the copper surface for the oxidation of hypophosphite, resulting in a higher electroless deposition rate. The thiourea also increases the growth colony size of the copper deposits and improves its conductivity. A reaction mechanism is proposed to describe the function of the thiourea and its derivatives on the process.
