Sulfur-Doped Millimeter-Sized Microporous Activated Carbon Spheres Derived from Sulfonated Poly(styrene-divinylbenzene) for CO2 Capture

Millimeter-sized activated carbon spheres are potential candidates for industrial-scale CO2 capture. Millimeter sized sulfur-doped microporous activated carbon spheres were synthesized from poly(styrene-divinylbenzene), a very cheap and easily operated resin product, in the present work and studied for. CO2 uptake. A series of sulfur-doped spherical carbon materials were yielded through the sulfonation, oxidation, carbonization, and KOH activation of the polymer precursors. In addition to promoting the cross-linking of the polymer molecules, the sulfonic substituents directly introduced sulfur-functional groups into the carbon materials after pyrolysis. The SCS-700 sample showed the best CO2 adsorption performance, whose sulfur content reached 0.69 wt %, and exhibited a high surface area of 1526 m(2) g(-1) and a large pore volume of 0.726 cm(3) g(-1). The adsorbent showed high CO2 uptake at both 25 degrees C (4.21 mmol g(-1)) and 50 degrees C (2.54 mmol g(-1)) under ambient pressure due to its abundant ultramicropores and a high proportion of oxidized sulfur functional groups. Thanks to its high microporous volume of 0.617 cm(3) g(-1), the CO2 performance at 8 bar was 10.66 mmol g(-1) at 25 degrees C. The thermodynamics indicated the exothermic and spontaneous nature of the adsorption process, which was dominated by a physisor,ption mechanism. Furthermore, the CO2 uptake curves on a TGA analyzer were fitted with different kinetic models, and the fractional order model showed the best agreement with the experimental data. The recycling curve of SCS-700 exhibited excellent cyclic adsorption performance with no significant capacity loss even after ten adsorption-desorption cycles. It is suggested that this excellent CO2 uptake was due to the synergistic effect of the well-developed microporous structure and the oxidized sulfur-containing functional groups.