Density and Phase Behavior of the CO₂ + Methylbenzene System in Wide Ranges of Temperatures and Pressures

Abstract

Knowledge of the thermophysical properties of CO2-hydrocarbon mixtures over extended ranges of temperature and pressure is crucial in the design and operation of many carbon capture and utilization processes. In this paper, we report saturated-phase densities, compressed-liquid densities and phase behaviour of CO2 + methylbenzene at temperatures between (283 and 473) K and at pressures up to 65 MPa over the full composition range. The saturated-phase densities were correlated by a recently-developed empirical equation with an absolute average relative deviation (AARD) of about 0.5 %. The compressed-fluid densities were also correlated using an empirical equation with an AARD of 0.3 %. The new data have been compared with the predictions of two equations of state: the predictive Peng-Robinson (PPR-78) equation of state and the SAFT- Mie equation of state. In both of these models, binary parameters are estimated using functional group contributions. Both models provided satisfactory representation of the vapour-liquid equilibrium and saturated-phase-density data, but the accuracy decreased in the prediction of the compressed-liquid densities where the AARD was about 2 %. The isothermal compressibility and isobaric expansivity are also reported here, and were predicted better with SAFT-γ Mie than with PPR-78. Overall, the comparisons showed that SAFT-γ Mie performs somewhat better than PPR-78 but the results suggest that further refinement of the SAFT-γ Mie parameter table are required.

Saturated-Phase Densities of (CO2 + Methylcyclohexane) at Temperatures from 298 to 448 K and Pressures up to the Critical Pressure

“…At T < 373 K, the liquid phase densities at first increased with pressure until a maximum was reached, after which the values declined up to the critical point. This behavior, which was particularly noticeable at temperatures of 298−323 K, has been observed for other (CO 2 + hydrocarbon) binary systems 17,18 and is attributed to the influence of CO 2 dissolving a ρ c and p c represent the critical density and pressure, respectively. The values of the average absolute deviation Δ AAD and average absolute relative deviation Δ AARD between the experimental densities and those calculated by eq 2.…”

“…To assist in developing thermodynamic models, we have investigated the thermophysical properties of several (CO 2 + hydrocarbon) systems over wide pressure and temperature ranges. Specifically, our group has reported densities and vapor–liquid equilibrium (VLE) data for the systems (CO 2 + n -heptane) and (CO 2 + methylbenzene), both mixtures involving a hydrocarbon containing seven carbon atoms. − In this paper, we present the saturated-phase densities for another system of that type: (CO 2 + methylcyclohexane). Several authors have reported VLE data for this system.…”

“…Figure5. Experimental saturated-phase densities ρ versus pressures p at T = 373 K for (red circles) CO 2 + heptane;18 (green circles) CO 2 + methylcyclohexane; and (blue circles) CO 2 + methylbenzene 17. Dewpoint densities (empty symbols) and bubble-point densities (full symbols).…”

CO2 Capture and Utilization Editorial

“…Binary parameters can be obtained from empirical models that can satisfactorily describe the thermodynamics of this type of amine solutions for wide ranges of temperatures and pressures. 5 The electrochemically mediated amine regeneration (EMAR) is an alternative method to the conventional thermal regeneration of amines aimed at reducing the energy demand of the CO 2 capture process. The EMAR process does not require steam integration, because only electrical energy is used for the regeneration of the solvent.…”

“…A deep knowledge of CO 2 –hydrocarbon mixtures is essential for the design and operation of absorption systems. Binary parameters can be obtained from empirical models that can satisfactorily describe the thermodynamics of this type of amine solutions for wide ranges of temperatures and pressures …”