Molecular Simulation of Phase and Reaction Equilibria: Software and Algorithm Development

    Research output: ThesisDissertation (TU Delft)

    5 Downloads (Pure)

    Abstract

    In the past decades, molecular simulation has become an important tool for studying phase and reaction equilibria. In this dissertation, we work on improvements of the Continuous Fractional Component (CFC) method in Monte Carlo simulations. We also develop a software package for molecular simulations that uses this method. In Chapter 2, we briefly introduce partial molar properties that we want to compute from molecular simulations. The CFC method is introduced and we explain how it can be modified to calculate properties in the NPT ensemble. After that, we focus on the Reaction Ensemble and modify the CFC method such that it becomes suitable for the calculation of chemical potentials and fugacity coefficients. We shortly point out the applicability of the CFC method in the Gibbs Ensemble and the software, BrickCFCMC, that was developed and used for this research. In Chapter 3, we study the vaporliquid equilibria of hydrogen sulfide, methanol and carbon dioxide. We use the CFC method for simulations in the Gibbs Ensemble and the Wolf method for calculations of the electrostatic interactions. The Wolf method is a computationally cheaper method than the commonly used Ewald method but has the same accuracy, provided that it is parametrized correctly. In Chapter 4, we test our new formulation of the CFC method in the Reaction Ensemble. For different systems of LennardJones particles, we compare the efficiency with the previous variant of the CFC method and the conventional method. Our formulation of the CFC method is more efficient and can directly check if the system has reached equilibrium. We continue our study by using this method for simulations of the HaberBosch process for the production of ammonia from nitrogen and hydrogen. In Chapter 5, we use the CFC method for computation of partial molar enthalpies and partial molar volumes. We start with simple systems of LennardJones particles and compare with a different method (similar to Widom’s method for obtaining chemical potentials). We calculate partial molar properties of nitrogen, hydrogen and ammonia in the stoichiometric compositions that were obtained in Chapter 4. From these results, we obtain the enthalpy of reaction. In Chapter 6, we combine the Gibbs Ensemble with the Reaction Ensemble for simulations of the esterification of methanol with acetic acid. We obtain a clear phase separation and calculate equilibrium compositions, chemical potentials, activity coefficients, and equilibrium constants. We distinguish two cases: one where the molecules are treated as rigid objects, and one where the molecules are flexible. No significant difference is observed between the results for the different cases. The simulations in Chapter 3 till Chapter 6 were performed with the software that was written as part of this research. This has lead to the software package BrickCFCMC and is available (open source) from: https://gitlab.com/ETh_TU_Delft/BrickCFCMC.
    Original languageEnglish
    Awarding Institution
    • Delft University of Technology
    Supervisors/Advisors
    • Vlugt, T.J.H., Supervisor
    Award date20 Oct 2020
    Print ISBNs978-94-6366-303-8
    DOIs
    Publication statusPublished - 2020

    Keywords

    • Molecular Simulation
    • Monte Carlo Simulation
    • Phase Equilibrium
    • Reaction Equilibrium

    Fingerprint Dive into the research topics of 'Molecular Simulation of Phase and Reaction Equilibria: Software and Algorithm Development'. Together they form a unique fingerprint.

    Cite this