Dew-point densities of fluid mixtures – Linkage of experiment and molecular simulation

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The goal of the proposed research project is the accurate determination of dew-point densities of fluid mixtures. Since precision density measurements near the dew line are affected by sorption effects and capillary condensation, a methodology will be developed, which links highly accurate gravimetric densimetry with molecular dynamics simulation (MDS). This methodology will contribute to a full description of a mixture’s dew line (including pressure, temperature, composition and density) with unprecedented accuracy. Based on this, the current state-of-the-art of existing equations of state describing the phase equilibrium of mixtures can be advanced. Accurately knowing the phase behavior of mixtures is essential, e.g., in the areas of natural gas transport and in carbon capture and utilization. This requires equations of state, which in turn involves accurate experimental vapor-liquid equilibrium (VLE) data as the most important input. Such data rarely comprise bubble-point and dew-point densities, however, exactly these densities are needed to fully describe the phase equilibrium. While, accurate measurements of bubble-point densities are possible, the accurate measurement of dew-point densities is affected by disturbing surface phenomena (i.e., adsorption and capillary condensation), which need to be understood and taken into account. Therefore, gravimetric precision densimetry was developed and set up within the Emmy Noether group of the applicant. Despite this measurement technology, no direct measurement of dew-point densities is possible, and even the presently most accurate measurements do not exactly reveal the location of the „true“ dew point. Here, molecular dynamics simulation can provide a better understanding on an atomistic level and, therewith, significantly contribute to the interpretation of the experimental data. Moreover, MDS is expected to support the development of correction models for density measurements in the vicinity of the dew line.