Fluids under High Pressure Insighted by Operando Neutron Imaging and Molecular Dynamics Simulations

ABSTRACT

Properties of fluids in fuel gas systems (high pressure) and catalytic reactors (high temperature and pressure) are essential for their modeling but scarcely available. Liquid toluene and methylcyclohexane have been operando observed upon pressurization with hydrogen, methane, or ethane using Neutron Imaging (NI). Studied systems mimic phase separation in fuel gases, for which interfacial tension, Henry's law volatility constant, apparent molar volume, diffusion coefficient of dissolved methane and ethane are experimentally provided, interfacial tension is measured for systems with hydrogen. This uniquely extensive basis of coupled experimental quantities has been compared with their Molecular Dynamics (MD) model predictions. Moreover, predictions of quantities inaccessible using NI, such as self‐diffusion coefficients, partial molar volumes, enthalpies and entropies of dissolution, or parameters of the Lennard‐Jones potential shed light on liquids exposed to fuel gases at high pressures. The MD model generally predicts system properties emerging from intermolecular interactions and can thus be used beyond the temperature and pressure limitations of the validation experiment. Following this concept, previously inaccessible diffusion coefficients in model bulk fluids mimicking the catalytic (de)hydrogenation of toluene are provided. This paves the way to detailed modeling of catalytic conversions in this Liquid Organic Hydrogen Carrier system.