Comparison of molecular models of carbon monoxide for calculation of vapor-liquid equilibrium

Abstract

There are a number of molecular models for carbon monoxide developed from different experimental measurements. This paper aims to compare the results that several of these models produced in the calculation of vapor-liquid equilibrium, in order to recommend which model should be used according to the property and phase to be calculated. The selected models included four non-polar models, with one or two Lennard-Jones sites, and four polar models with dipoles or partial charges to represent the polarity of carbon monoxide. Gibbs-ensemble Monte Carlo simulations in the canonical version (NVTGEMC) were used to determine the densities of the phases in equilibrium, the vapor pressure and vaporization enthalpy between 80 and 130 K with each of the selected models. It was found that the more complex molecular models, SVH, ANC and PGB, better described the density of the saturated liquid (about 7% average deviation), but these models generated deviations higher than 40% for vapor properties and 20% for vaporization enthalpy. On the other hand, the non-polar BLF model generated the lowest deviations for saturation pressure and vapor density (6.8 and 21.5%, respectively). This model, as the model HCB, produces acceptable deviations for liquid density and vaporization enthalpy (between 10 and 12%). The BLF and HCB models, being non-polar and not requiring the calculation of long-range interactions, can be considered as the molecular models presenting the most satisfactory balance between deviations of the results and calculation complexity.