Thermophysical properties of the liquid organic hydrogen carrier system based on benzyltoluene considering influences of isomerism and dissolved hydrogen
Manuel Kerscher, Julius H. Jander, Junwei Cui, Lukas Maurer, Patrick J. Wolf, Jonas D. Hofmann, Anil Köksal, Hannah Zachskorn, Franziska Auer, Peter S. Schulz, Peter Wasserscheid, Michael H. Rausch, Thomas M. Koller, Andreas P. Fröba
Abstract
The benzyltoluene (BT)-based liquid organic hydrogen carrier (LOHC) system currently considered for large-scale applications represents a mixture of regioisomers. To characterize this complex system, a comprehensive experimental database for various thermophysical properties of synthesized BT isomers and their mixtures without and with the presence of hydrogen (H 2 ) close to vapor-liquid equilibrium is established using optical and conventional techniques at process-relevant temperatures and pressures up to 573 K and 6 MPa. The surface tension varies by less than 4% among the dehydrogenated (H0-BT) or hydrogenated (H12-BT) isomers. The density and viscosity of mixtures of H0-BT or H12-BT isomers can be described by simple mixing rules with average absolute relative deviations of 0.022% and 0.38%. With increasing H 2 pressure, the viscosity remains nearly constant, while the interfacial tension decreases by up to 5%. The thermal and mutual diffusivity of H12-ortho-BT containing dissolved H 2 at 6 MPa decrease and increase with increasing temperature. • Synthesis of high-purity regioisomers of LOHC system based on benzyltoluene (BT). • Optical and conventional techniques applied up to 573 K and 6 MPa hydrogen (H 2 ). • Minor variation in density and surface tension among BT or its hydrogenated isomers. • Large effect of isomeric mixture composition on viscosity with variations up to 33%. • First temperature-dependent data for thermal and Fick diffusivity of BT-H 2 system.