Hydroquinone and quinone functional
groups were grafted onto a
hierarchical porous carbon framework via the Friedel–Crafts
reaction to develop more efficient adsorbents for the selective capture
and removal of carbon dioxide from flue gases and natural gas. The
oxygen-doped porous carbons were characterized with scanning electron
microscopy, transmission electron microscopy, X-ray powder diffraction,
Fourier transform infrared spectroscopy, and Raman spectroscopy. CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub> adsorption isotherms were
measured and correlated with the Langmuir model. An ideal adsorbed
solution theory (IAST) selectivity for the CO<sub>2</sub>/N<sub>2</sub> separation of 26.5 (298 K, 1 atm) was obtained on the hydroquinone-grafted
carbon, which is 58.7% higher than that of the pristine porous carbon,
and a CO<sub>2</sub>/CH<sub>4</sub> selectivity value of 4.6 (298
K, 1 atm) was obtained on the quinone-grafted carbon (OAC-2), which
represents a 28.4% improvement over the pristine porous carbon. The
highest CO<sub>2</sub> adsorption capacity on the oxygen-doped carbon
adsorbents is 3.46 mmol g<sup>–1</sup> at 298 K and 1 atm.
In addition, transient breakthrough simulations for CO<sub>2</sub>/CH<sub>4</sub>/N<sub>2</sub> mixture separation were conducted to
demonstrate the good separation performance of the oxygen-doped carbons
in fixed bed adsorbers. Combining excellent adsorption separation
properties and low heats of adsorption, the oxygen-doped carbons developed
in this work appear to be very promising for flue gas treatment and
natural gas upgrading
