Abstract
Experimental determination of solubility and diffusion coefficients of CO~2~ and N~2~ in poly(dimethyl, methylphenyl siloxane) (PMPS) for the pressure range 0β150 kPa and the temperature range of β10Β°C to 45Β°C is discussed. The absorption isotherms were measured by pressure decay equilibrium. Diffusion coefficients were determined by modeling the transient absorption data by Fickian diffusion. The value of solubility coefficient for CO~2~ at 35Β°C was 1.21 Β± 0.02 cm^3^ CO~2~ (STP)/(cm^3^ polymer.atm) and it increased to 2.07 Β± 0.01 cm^3^ CO~2~ (STP)/(cm^3^ polymer.atm) at 1Β°C. The absorption isotherms of CO~2~ obtained were linear for the pressure range 0β200 kPa and the enthalpy of sorption value was β10.82 kJ/mole for CO~2~. However, the diffusion coefficients of CO~2~ changed with feed pressure. The diffusion coefficient of CO~2~ in PMPS at 22Β°C and 128.6 kPa equilibrium pressure was 7.22 Γ 10^β6^ cm^2^/s and thus the permeability value at these conditions was 1392 Barrers. The diffusion coefficients of CO~2~ at 0Β°C and equilibrium pressures of 125.8 kPa and 10.5 kPa were 5.72 Γ 10^β6^ cm^2^/s and 4.31 Γ 10^β6^ cm^2^/s, respectively. Consequently, the CO~2~ permeability in PMPS decreases by about 20% when the pressure is reduced from 125.8 to 10.5 kPa at 0Β°C. Β© 2007 American Institute of Chemical Engineers AIChE J, 2008