Compressed liquid density and thermodynamic modeling for the promising liquid organic hydrogen carrier Benzyltoluene/Dibenzyltoluene

Benzyltoluene (BT) and dibenzyltoluene (DBT) mixtures are promising liquid organic hydrogen carriers (LOHCs) due to their high hydrogen storage capacity, excellent thermal stability and safety of storage and transportation. This study investigates the thermodynamic properties of BT + DBT mixtures to develop an accurate prediction model for hybrid LOHCs. Experimental measurements of liquid density were performed over a wide temperature range (293.15-433.15 K) and pressures up to 20 MPa, revealing the effects of temperature, pressure, and composition on thermodynamic properties. An empirical model using the Tait equation achieved an average absolute deviation of 0.027%. Drawing on experimental data, the model parameters of perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) were optimized separately for low-pressure and highpressure regions, improving prediction accuracy and enabling the evaluation of bubble-point pressure and saturated densities. Additionally, simulations were conducted to analyze the variation of hydrogen mole fraction with pressure and temperature in both the dehydrogenation reactor and the condenser. Derived thermodynamic properties, including excess molar volume, isothermal compressibility, thermal expansion coefficient, and heat capacity, were calculated to support LOHC system design. This work provides foundational data and a reliable theoretical model to optimize hydrogen storage and dehydrogenation processes for BT + DBT mixtures. The results offer valuable insights for future applications of LOHC technology in energy-efficient hydrogen storage and transport systems.