Phase equilibria in process design for the production of polymers derived from carbon dioxide

The optimisation of an innovative process where carbon dioxide (CO2) is used as raw material for the production of polyurethane precursors relies strongly on the physical properties and phase equilibria of the mixtures involved. In this work, we present experimental results for high-pressure phase equilibria of systems involving CO2, propylene oxide, different polyether carbonate polyols (CO2-PET) and propylene carbonate, at pressures up to 8 MPa and temperatures between 373 K and 393 K. Low-pressure phase equilibria were determined for the system CO2-PET + propylene carbonate, at temperatures between 373 K and 414 K, at pressures below 30 hPa. Furthermore, the solubility of nitrogen in CO2-PET was determined at room temperature at pressures up to 0.5 MPa. Different apparatus were employed in this work, based on synthetic methods.The high-pressure experimental results were modelled with the Soave–Redlich–Kwong equation of state, with the Péneloux–Rauzy volume translation and Mathias–Klotz–Prausnitz mixing rules. The ability of the method to predict multicomponent phase equilibria using parameters fitted to binary data only was tested. Low-pressure results were modelled using the Non-Random Two Liquid (NRTL) model.

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