Fick Diffusivity, Thermal Diffusivity, Thermal Conductivity, Density, and Mixture Composition of Binary Mixtures of γ-Butyrolactone and 1,4-Butanediol by Light Scattering Techniques and Conventional Methods

Abstract γ -Butyrolactone (GBL) and 1,4-butanediol (BDO) represent a promising liquid organic hydrogen carrier (LOHC) system, for which a lack of thermophysical property data at process-relevant conditions exists. For this LOHC system, the Fick diffusivity D 11 , thermal diffusivity a , thermal conductivity λ , and density ρ were investigated at about 0.1 MPa as a function of temperature T and mixture composition at GBL amount fractions x GBL = (0.00, 0.25, 0.50, 0.75, and 1.00) using light scattering and conventional techniques. Vibrating U-tube densimetry and a guarded parallel-plate instrument were employed to determine ρ between T = (283 and 473) K and λ between T = (283 and 363) K. Dynamic light scattering allowed simultaneous access to a and D 11 between T = (298 and 473) K in macroscopic thermodynamic equilibrium, while polarization-difference Raman spectroscopy was applied after calibration to monitor the composition. The onset of a certain decomposition or structural rearrangement was observed above about T = 398 K, depending on the sample composition and experimental boundary conditions. When such effects are small, the data for ρ , a, and D 11 increase with increasing x GBL at a given T , whereas λ has the opposite trend. With the help of the results for ρ , a , and λ , values for the specific isobaric heat capacity c p could be derived. The present measurement results agree with the few experimental data for ρ and λ available in the literature for the pure mixture components and contribute to a significant extension of the thermophysical property database for this highly promising LOHC system.