High-pressure solubility of methane (CH4) and ethane (C2H6) in mixed polyethylene glycol dimethyl ethers (Genosorb 1753) and its selectivity in natural gas sweetening operations

The solubility of methane (CH4) and ethane (C2H6) in a mixture of polyethylene glycol dimethyl ethers (Genosorb 1753) was measured at (298.15, 313.15, and 333.15) K and at pressures up to 7700 kPa using a Jerguson equilibrium cell. The solubility data of CO2 and light hydrocarbons (CH4 and C2H6) in Genosorb 1753 were compared with the solubility in other physical solvents. The results were correlated with the Peng–Robinson equation of state (PR-EOS), and the interaction parameters are reported. Among the activity coefficient models, the Non-Random Two Liquid Theory (NRTL) model fitted the data well with an absolute average deviation of 6 %. Henry’s Law constants (HCH4 and HC2H6) and the excess properties (excess Gibbs free energy (GE), excess entropy (SE), and excess enthalpy (HE)) of the liquid mixture were predicted at each temperature using the NRTL activity coefficient model over the full range of composition. The enthalpy of solution and the partial molar enthalpy of mixing for all gases were determined at infinite dilution. In addition, the enthalpies of solution for all the gases were calculated using the Clausius–Clapeyron equation. The coabsorption of hydrocarbons (CH4 and C2H6) with CO2 (selectivity) was evaluated with the following function {HCO2/(HCH4·HC2H6)}. Compared to other solvents used in gas sweetening, Genosorb 1753 was found to have the highest absorption capacity for CO2 and a low capacity for CH4 but a higher capacity for C2H6.