Influence of dissolved hydrogen on the thermophysical properties of organic liquids

• Applicant: Professor Dr.-Ing. Andreas Paul Fröba
• Subject Area: Technical Thermodynamics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524349465

Hydrogen (H2) is a promising energy carrier for the future energy supply. In many H2-based technologies considered nowadays, H2 is in contact with organic liquids at vapor-liquid equilibrium (VLE) conditions. To obtain a fundamental understanding of the fluid behavior of mixtures of organic liquids with dissolved H2, detailed knowledge on their thermophysical properties as a function of temperature T, pressure p, and composition is required, yet often lacking or insufficient. The main objective of the proposed research project is to identify the influence of dissolved H2 on various thermophysical properties of organic liquids, where the properties are mainly relevant for the characterization of the transport of heat, mass, and momentum. For this, the H2 solubility and interfacial tension as well as the density, dynamic viscosity, thermal diffusivity, and Fick diffusion coefficients in the liquid phase of binary and ternary mixtures of organic liquids containing H2 at VLE should be determined via experimental and theoretical studies. The proposed representatives of different organic liquid classes complement the few already examined systems and allow to analyze the transferability of findings between the classes. Linear and branched alkanes, their oxygenated derivates given by polyvalent alcohols and poly(oxymethylene) dimethyl ethers as well as mono- or bicyclic hydrogenated and dehydrogenated hydrocarbons enable to cover wide ranges of the physicochemical features in terms of size, structure, and polarity and, thus, also of the absolute property values. Conventional methods as well as dynamic light scattering (DLS), the latter applied to the liquid bulk of fluids and at their phase boundaries within the same sample cell, should provide an accurate experimental database of the thermophysical properties for T and p up to 473 K and 10 MPa. Moreover, the DLS measurements promise to shed light on relations between the experimental results and the theory of diffusion in ternary mixtures involving H2. The macroscopic properties should be connected with the molecular characteristics of the organic solvents and the H2-influenced fluid structure studied by Raman spectroscopy and equilibrium molecular dynamics (EMD) simulations. The latter are planned to be used for selected representatives of each class, where corresponding force fields should be optimized mainly with respect to the T-dependent liquid density of the pure solvents and the H2 solubility. The focus of the EMD simulations lies on the analysis of the molecular H2 and solvent arrangement in the liquid phase and at the interface. The correspondingly developed picture and the available data should lead to the description of the impact of H2 on the thermophysical properties of interest in its mixtures with organic liquids as a function of temperature, pressure, and solvent composition in form of suitable correlations.

• DFG Programme: Research Grants