A heat-soaked isotropic petroleum pitch has been region of liquid-liquid equilibrium at temperatures from 600 to 640 K, pressures from 60 to 155 bar, and solvent-to-pitch (S/p) ratios of 2.0 and 3.0. The solvent compositions of both the solvent- rich top phase and the pitch-rich bottom phase were measured, along with the weight fraction of pitch extracted into the top phase (i..e., the extraction yield). A thermodynamic model that incorporates the molecular weight distribution of the feed pitch, mathematically generated pseudocomponents, and the SAnT equation of state was used to predict phase compositions and extraction yields over a range of temperatures, pressures, and S/p ratios; good agreement is obtained with subsequently measured experimental data. The model contains a total of three adjustable parameters, which are determined by fitting a limited set of experimental data (e.g., phase compositions at one temperature and Sm ratio). Because these parameters are independent of temperature and composition, they can be used to predict phase compositions and extraction yields for supercritical operating conditions that have yet to be experimentally investigated.
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