Effect of the degree of hydrogenation on the viscosity, surface tension, and density of the liquid organic hydrogen carrier system based on diphenylmethane

Schmidt, Patrick S.; Kerscher, Manuel; Klein, Tobias; Jander, Julius H.; Bioucas, Francisco E. Berger; Rüde, Timo; Shao, Li; Stadelmaier, Monika; Hanyon, Samantha; Fathalla, Ramy R.; Bösmann, Andreas; Preuster, Patrick; Wasserscheid, Peter; Koller, Thomas M.; Rausch, Michael H.; Fröba, Andreas P.

doi:10.1016/j.ijhydene.2021.11.198

Cited by 26 publications

(27 citation statements)

References 76 publications

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“…In contrast, significant discrepancies are found for the surface tension of the dehydrogenated H0-F, where the relative deviations of the SLS results from σ calc are quite constant between −(16 and 19)% and clearly outside combined uncertainties. Lower surface tension values obtained by SLS relative to the PD data were also partially observed in our previous studies on bicyclic LOHCs and their derivatives, ,,, especially for the oxygenated compounds and at low T . Although still speculative, this behavior may be caused to some extent by possible self-induced orientation effects of the molecules at the vapor–liquid phase boundary, which can induce an electrostatic potential across the interface and influence the dynamics of the probed surface fluctuations. , Such effects are not considered in the applied classical hydrodynamic theory ,, and would cause by trend too low values for σ, while η L as a bulk property is apparently unaffected and can still be determined accurately; see refs , , , .…”

Section: Resultssupporting

confidence: 82%

“…To develop structure-property relationships for LOHC systems containing process-relevant impurities, which can enable the establishment of corresponding prediction models, accurate information about the thermophysical properties of the pure LOHC materials and the associated impurities is necessary. Regarding the DPM-based system, there is already an extended database for the thermophysical properties, viscosity, surface tension, and density, 10,13,14 while such information is very scarce for the relevant impurities H0-F and H12-F. For both the liquid density and liquid viscosity, only a single correlation based on measurements over a limited temperature range is available for H0-F 15 and H12-F. 16 Knowledge about the surface tension of both compounds does not exist so far. The limited experimental database may be connected to the relatively large melting point of H0-F of about 386 K 15 and the presence of stereoisomerism for H12-F. 17 Depending on the conditions during the hydrogenation from H0-F to H12-F, the six stereoisomers of the latter can be found in the product mixture with varying share.…”

Section: ■ Introductionmentioning

confidence: 99%

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Viscosity and Surface Tension of Fluorene and Perhydrofluorene Close to 0.1 MPa up to 573 K

et al. 2022

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In the present study, the liquid viscosity and surface tension of fluorene (H0-F) and its fully hydrogenated counterpart perhydrofluorene (H12-F), representing process-relevant byproducts of the liquid organic hydrogen carrier (LOHC) system based on diphenylmethane and dicyclohexylmethane and potentially interesting LOHC compounds by themselves, were determined close to 0.1 MPa using different experimental methods. Besides surface light scattering (SLS) allowing for a simultaneous access to both properties up to 573 K, conventional methods in the form of capillary viscometry and pendant-drop tensiometry were applied up to (473 and 523) K, respectively. Furthermore, the liquid density of H12-F was measured by vibrating-tube densimetry from (283 to 473) K. While agreement of the viscosity and surface tension results obtained by SLS and the conventional methods is found in the case of H12-F, this is not given for H0-F, especially with respect to its surface tension, which seems to be caused by SLS-specific effects. H0-F exhibiting a melting point of about 384 K shows larger values for density, surface tension, and viscosity compared to H12-F being liquid at 283 K. The latter compound features stereoisomerism which appears to have a pronounced effect on the thermophysical properties. This could be deduced by comparison with the very limited amount of experimental data for the fluorene-based substances that are available in the literature so far. The extension of the thermophysical property database for H0-F and H12-F under process-relevant conditions can be useful for future studies, particularly in the field of chemical hydrogen storage.

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Section: Resultssupporting

confidence: 82%

Section: ■ Introductionmentioning

confidence: 99%

Viscosity and Surface Tension of Fluorene and Perhydrofluorene Close to 0.1 MPa up to 573 K

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“…In line with our previous investigations, , a relative expanded ( k = 2) uncertainty of U r (σ) = 0.02 can be specified for the present surface tension data of TOTM between 273 and 473 K. This uncertainty accounts for the uncertainties in the calibration procedure, the edge detection, and the liquid density data ρ′, while the uncertainty of the gas density ρ″ with an estimated value of 10% has a negligible influence. At temperatures of 523 and 573 K, the expanded uncertainty of the surface tension is estimated to be U r (σ) = 0.03, which is mainly related to the extrapolation of the liquid density correlation developed up to 473 K toward larger temperatures.…”

Section: Methodssupporting

confidence: 62%

“…These effects appear to change the dynamics of the surface fluctuations in fluids with a preferred surface orientation in such a way that the application of the classical hydrodynamic theory , which does not account for these effects causes underestimated apparent surface tensions, whereas the viscosity as bulk property is unaffected. As a result, for several LOHC systems featuring two nearby benzyl or cyclohexyl rings, the surface tensions obtained by SLS were systematically lower than those determined by the PD method, especially at lower temperatures. − For simple fluids such as alkanes ,, and alcohols as well as the reference fluids toluene and benzene with a single aromatic ring, the agreement of the surface tensions from SLS with literature data obtained by other techniques does not imply surface orientation effects. By the choice of TOTM having a single aromatic ring in the center and three branched alkyl side chains attached to the ring via ester functionalities, it is possible to probe surface orientation effects over a broad range of viscosity and surface tension, where the surface fluctuations change from an overdamped to an oscillatory behavior with the increase in temperature.…”

Section: Introductionmentioning

confidence: 71%

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Viscosity and Surface Tension of High-Viscosity Standard Tris(2-ethylhexyl) Trimellitate Close to 0.1 MPa between 273 and 523 K by Surface Light Scattering

et al. 2022

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In the present work, the liquid viscosity and surface tension of tris(2-ethylhexyl) trimellitate (TOTM) was determined close to 0.1 MPa over a temperature range between 273 and 523 K by surface light scattering (SLS). Such investigations were stimulated by the fact that TOTM is suggested as a potential viscosity standard of moderately high viscosity for temperatures up to 473 K and pressures up to 200 MPa. Based on the SLS experiments at macroscopic thermodynamic equilibrium, a simultaneous determination of liquid viscosity from 273 to 523 K and surface tension from 398 to 523 K with relative expanded uncertainties typically below 0.03 (coverage factor k = 2) was possible. To evaluate the results from SLS and to check possible surface orientation effects found in our previous SLS studies on liquid organic hydrogen carriers, conventional methods in the form of the pendant-drop method and capillary viscometry were used to determine the surface tension and viscosity from 273 to 573 K and from 293 to 353 K, respectively. For evaluating all experimental methods applied, the liquid density was obtained with the help of a vibrating-tube densimeter between 283 and 473 K. From a long-time SLS study at 573 K and subsequent density and nuclear magnetic resonance measurements, a clear sample degradation of TOTM was observed, which may hinder its application as an industrial viscosity standard above 523 K. For both the surface tension and the viscosity which covers a range between about 1500 and 0.9 mPa s at temperatures between 273 and 523 K, agreement between the results from SLS and the conventional methods within combined uncertainties was found, which is also valid by comparison with the literature. In summary, the experimental results from this work could not only contribute to an improved data situation for viscosity and surface tension of TOTM over a broad temperature range but also reveal that TOTM does not show pronounced molecular orientation effects at the vapor–liquid interface which would influence the dynamics of the surface fluctuations probed by SLS.

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Viscosity and Interfacial Tension of Binary Mixtures Consisting of Linear, Branched, Cyclic, or Oxygenated Hydrocarbons with Dissolved Gases Using Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

et al. 2022

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In the present study, the influence of the molecular characteristics of the solvent and solute on the dynamic viscosity and interfacial tension of binary mixtures consisting of a liquid with a dissolved gas is investigated using surface light scattering (SLS) and equilibrium molecular dynamics (EMD) simulations. In detail, binary mixtures consisting of linear, branched, cyclic, or oxygenated hydrocarbons and the solutes hydrogen, helium, methane, water, carbon monoxide, or carbon dioxide are studied in the temperature range between (298 and 573) K and for solute mole fractions up to 0.2. With SLS, the liquid dynamic viscosity and interfacial tension of the binary mixtures could be accessed in macroscopic thermodynamic equilibrium with average expanded uncertainties (coverage factor k = 2) of (2.4 and 2.3)%, respectively. While EMD simulations were able to predict the influence of the dissolved gases on the interfacial tension of the binary mixtures, the simulations fail to represent the influence of the dissolved gas on the viscosity. Due to the systematic variation of the solvent and solute molecules, the influence of the molecular characteristics, e.g., in the form of size, shape, or polarity, on the thermophysical properties of the mixtures is discussed. Dissolving carbon dioxide, e.g., leads to a reduction of both properties by up to 60% compared to the properties of the pure solvent. Dissolved helium, on the other hand, has only a small influence on the properties of the pure solvent. The influence of dissolved water was found to be negligible in mixtures with an alkane but strongly increases both properties when dissolved in an alcohol, which may be explained by the formation of hydrogen bonds.

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Effect of the degree of hydrogenation on the viscosity, surface tension, and density of the liquid organic hydrogen carrier system based on diphenylmethane

Cited by 26 publications

References 76 publications

Viscosity and Surface Tension of Fluorene and Perhydrofluorene Close to 0.1 MPa up to 573 K

Viscosity and Surface Tension of Fluorene and Perhydrofluorene Close to 0.1 MPa up to 573 K

Viscosity and Surface Tension of High-Viscosity Standard Tris(2-ethylhexyl) Trimellitate Close to 0.1 MPa between 273 and 523 K by Surface Light Scattering

Viscosity and Interfacial Tension of Binary Mixtures Consisting of Linear, Branched, Cyclic, or Oxygenated Hydrocarbons with Dissolved Gases Using Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

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