Six physical absorbents with the
ether groups were selected for
CO2 absorption: tetraethylene glycol dimethyl ether (TEGDME),
diethylene glycol monohexyl ether, 2-butoxyethyl ether, triethylene
glycol monobutyl ether, ethylene glycol dibutyl ether, and dipropylene
glycol dimethyl ether (DPGDME). CO2 solubilities in these
absorbents were measured at 273.15 and 283.15 K and 0–1.2 MPa.
Henry’s constants of these CO2 + ether absorbent
systems were calculated and analyzed at 273.15 K. The ether group
is found more powerful than the methylene group, and the ethyl group
is more effective than the hydroxyl group to improve the absorption
ability of the absorbents. A lower temperature tends to facilitate
the absorption process by increasing the absorption ability. Henry’s
constants and mass solubilities of the ether absorbents were compared
with those of the ionic liquids, common solvents, and other absorbents.
TEGDME and DPGDME are potential absorbents according to the evaluation
in both mole and mass fraction. The thermodynamic properties, such
as entropy, enthalpy, and Gibbs free energy of solution, for CO2 + the ether absorbent systems were calculated and discussed
for potential development of corresponding CO2 capture
processes.
The
mixtures of propylene carbonate (PC) (1) + poly(propylene glycol)
monobutyl ether with a molecular weight of 340 (PPGME340) (2) were
studied as physical absorbents for CO2 absorption with
different mass fractions (w
1 = 0.0000,
0.2501, 0.5002, 0.7495, and 1.0000). The physical properties including
densities and kinematic viscosities of these absorbents were determined
and regressed by linear equation and Vogel–Fulcher–Tammann
equation. CO2 absorption capacities of the absorbents under
pressures up to 1300 kPa and at temperatures from 298.15 to 303.15
K were determined by the isothermal synthesis device and fitted by
the extended Antoine equation. Adding PC into PPGME340 will result
in a slight increase of density, dramatic decrease of kinematic viscosity,
and moderate decrease of CO2 absorption capacity based
on per mole absorbent. Compared with common solvents in industrial
plants, PPGME340-contained absorbents show relatively high absorption
capacity and kinematic viscosity. In addition, absorbent PC + PPGME340
with a mass fraction of w
1 = 0.2501 shows
relatively high CO2 absorption capacity and moderate kinematic
viscosity, suggesting its better potential for the industrial application
than pure PPGME340.
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