Pitch-based spherical activated carbons with small mesopores for CO2 capture

Abstract

A simple suspension polymerization coupling with oxidative stabilization, carbonization, and H₂O steam activation are applied to synthesize a series of hierarchical porous millimeter-sized pitch-based spherical activated carbons (PSAC). The as-obtained PSAC possess a tunable specific surface area from 975 m² g^− 1 to 1761 m² g^− 1, a pore volume of 0.44 ~ 0.82 cm³ g^− 1, and spherical morphology via regulation of H₂O activation time. The CO₂ adsorption capacity is closely related to the ultramicroporous volumes below 0.2 bar. The introduction of rich micropores has a positively influence on CO₂ adsorption capacity that can reach 2.59 mmol g^− 1 at 1.0 bar. When the pressure increasing to 5.0 bar, the micro-mesoporous PSAC shows higher CO₂ adsorption capacity of 7.23 mmol g^− 1 at 5 bar than microporous PSAC, indicating that the introduction of moderate mesopores can accelerate CO₂ diffusion rate and improve the utilization of micropores active adsorption sites. Based on the ideal adsorption solution theory (IAST), the CO₂/N₂ and CO₂/H₂O adsorption selection factors S_ads of PSAC are as high as 49.9 and 8.29, respectively. Therefore, PSAC with high adsorption/desorption rate, good selectivity for CO₂/N₂ and CO₂/H₂O, excellent renewability, and easy mass production provide potential options for industrial application of CO₂ capture.