Mixed gas sorption in glassy polymeric membranes: II. CO2/CH4 mixtures in a polymer of intrinsic microporosity (PIM-1)

Abstract

The individual solubility of CH 4 and CO 2 from binary gas mixtures was measured at 35 °C and up to 35 bar in a polymer of intrinsic microporosity (PIM-1), at different compositions of the gas phase (from 0 to 50 mol% of CO 2 ). The experiments were conducted on a pressure-decay apparatus equipped with a gas chromatograph, allowing a highly flexible measuring procedure. The gas solubility was plotted versus gas phase composition, total pressure, gas fugacity and second gas concentration. The mixed gas solubility of both species, CH 4 and CO 2 , is lower than the pure gas value at the same fugacity, but the reduction of methane solubility due to the presence of CO 2 is generally more significant. Such behavior is due to the fact that CO 2 has normally higher solubility than methane: indeed the depression of the solubility coefficient with respect to the pure gas value is similar for both gases, when reported at the same concentration of the second gas.The real, mixed gas solubility selectivity is in general higher than the ideal value calculated from pure gas behavior. The ratio between real and ideal solubility selectivity increases with CO 2 concentration in the membrane, according to a single mastercurve, reaching a maximum value of 4, and increases also with the ratio between CO 2 and CH 4 concentration in the membrane. In particular, as in the case of other glassy polymers, the real solubility selectivity of CO 2 over CH 4 is higher than the ideal value if c(CO 2 )>c(CH 4 ), and it is lower than the ideal value if the opposite condition holds true. Such behavior occurs because the competition for sorption is normally less effective on the more abundant penetrant in the polymer. A selectivity-solubility performance plot can be drawn for this system.

Effect of methanol treatment on gas sorption and transport behavior of intrinsically microporous polyimide membranes incorporating Tröger׳s base

“…In the present study, we evaluated the gas permeability, diffusivity, and solubility of PI-TB membranes for small gas molecules in order to improve the understanding of gas transport properties by applying a solution-diffusion model. Different from other studies [36,37], the gas solubility was determined by the barometric pressure decay method and thereafter, the role of methanol treatment was elucidated based on the derived solubility coefficients. We also investigated the effect of methanol treatment on the membrane plasticization phenomena by monitoring the change in CO 2 permeability at elevated pressures in feed gas mixture.…”

Tailoring molecular interactions between microporous polymers in high performance mixed matrix membranes for gas separations

“…5). Typical of dual mode sorption 36 and widely observed in polymer membranes that were not plasticised significantly by the permeating gas, 37 the CO 2 permeabilities of PIM-EA (Me 2 )-TB/PAF-1 and PIM-EA(H 2 )-TB/PAF-1 were reduced by 2% and 20%, respectively (Fig. 5a and b) as single gas CO 2 pressure increased from 2 to 20 bar.…”

Accelerating CO2 capture of highly permeable polymer through incorporating highly selective hollow zeolite imidazolate framework

“…Samples were pretreated at 110°C in a vacuum oven for 5 hr and then tested from 0.1 to 3 MPa at 30°C. A dual sorption theory is used to describe sorption isotherms of PIM‐based membranes: where C is the solubility, cm 3 (STP) cm −3 (polymer). C D and C H represent the amount of gas adsorbed in Henry and Langmuir sites, respectively.…”