Thermodynamic Characterization of Gas Mixtures for Non-Thermal Plasma CO2 Conversion Applications with Soft-SAFT

Carbon dioxide (CO2) transformation into added-valueproducts through non-thermal plasma (NTP) represents a novel technologyof interest. The process involves, apart from CO2, mixturesof different gases such as carbon monoxide (CO), oxygen (O-2), nitrogen (N-2), argon (Ar), and hydrogen (H-2) for subsequent CO2 methanation. In this work, a preliminarystudy of the thermodynamic representation of the mixtures relevantin the context of carbon capture, utilization, and storage (CCUS)processes, but focused on the NTP conversion, is presented. The thermodynamiccharacterization is achieved through the application of the polarsoft-statistical associating fluid theory (SAFT) equation of state(EoS), which allows molecular parameterization of pure compounds andthe description of mixtures at different conditions of temperatureand pressure. An accurate parametrization of all gases is carriedout by explicitly considering the quadrupolar nature of CO2, CO, and N-2. The characterization is then used to describeseveral single-phase densities, derivative properties, second virialcoefficients, and the vapor-liquid equilibrium (VLE) of CO2 binary mixtures with Ar, O-2, CO, N-2, and H-2, as well as combinations between some of thesegases. A parametric analysis of the impact of the binary parameterson the equilibria description is carried out to assess the temperaturedependency. The results have overall shown good agreement to experimentaldata in most conditions using one or two binary parameters. Finally,ternary systems involving CO2, O-2, Ar, and N-2 have been predicted in good agreement with the experimentaldata, demonstrating the capacity of the model to evaluate the behaviorof multicomponent gas mixtures.