High-pressure phase equilibria and thermodynamic modeling for binary systems of light paraffins and aluminum alkyls

A continuous-flow apparatus was used to measure vapor–liquid equilibrium data at 398 K for the propane–triethylaluminum (TEA) and propane–tributylaluminum (TBA) systems. The pressures ranged from 31.0 to 55.2 bar for the propane–TEA system and 44.8 to 58.3 bar for the propane–TBA system. Equilibrium vapor- and liquid-phase compositions were obtained at selected pressures by a gravimetric method. A thermodynamic model was developed to correlate the vapor–liquid equilibrium data for the ethane–TEA, ethane–TBA, and ethane–trihexylaluminum (THA) systems that were previously measured and the propane–TEA and propane–TBA systems. Each system consists of the light paraffin and an equilibrium mixture of the aluminum alkyl monomer and dimer species. The Peng–Robinson cubic equation of state was used to calculate the equilibrium phase compositions. The necessary parameters for the equation of state were obtained from thermodynamic data of other investigators coupled with a group contribution method.