Hydroquinone and Quinone-Grafted Porous Carbons for Highly Selective CO₂ Capture from Flue Gases and Natural Gas Upgrading

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. CO₂, CH₄, and N₂ adsorption isotherms were measured and correlated with the Langmuir model. An ideal adsorbed solution theory (IAST) selectivity for the CO₂/N₂ 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 CO₂/CH₄ 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 CO₂ adsorption capacity on the oxygen-doped carbon adsorbents is 3.46 mmol g^–1 at 298 K and 1 atm. In addition, transient breakthrough simulations for CO₂/CH₄/N₂ 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