Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

A 60 cm3 temperature-controlled pressure cell was constructed for vapor-liquid equilibria (VLE) measurements in methane-dominant mixtures at conditions representative of those found in cryogenic gas processing plants. The experimental system included a pressure transducer located in the cell s lid, temperature-controlled sampling capillaries, automated microliter sampling valves, and a gas chromatograph (GC) with two columns and multiple detectors for the simultaneous measurements of phase compositions. A gravimetrically prepared mixture of methane + 2-methylpropane (isobutane) {CH4(1) + i-C4H10(2)} with the overall mole fraction z2 = (0.0724 +- 0.0001) was loaded into the cell, and P,T,x,y data for this mixture were obtained along two isochoric pathways over the temperature range from (150 to 250) K at pressures to 9 MPa. The measured VLE data extend into a temperature range not previously studied for this system and are compared with previous literature data and with the predictions of the Groupe European de Recherche Gaziere (GERG-2004) multiparameter equation of state (EOS). Where they overlap, the new data are consistent with the existing VLE data for this binary mixture, within the estimated uncertainties of the new data. At temperatures above 190 K, the relative average absolute deviation (AAD) from the GERG-2004 EOS is about 6 % for both x2 and y2. Including the data measured below 190 K, the relative AAD for x2 increases to 9 %. Analysis of the new data also indicates a possible inconsistency in overall density predictions for the two-phase region made using the GERG-2004 EOS