CO₂ sorption on surface-modified carbonaceous support: Probing the influence of the carbon black microporosity and surface polarity

Graphical abstract: - Highlights: • CO₂-sorbent materials preparation by surface modification of CB. • CB functionalization (amino-groups), CB coating (Fe₃O₄), CB impregnation (ionic liquid). • Sorbents bearing basic functionalities exhibit the higher CO₂ sorption capacity. • Microporous supporting material limits the CO₂ accessibility toward the adsorbing material. - Abstract: The use of solid sorbents is a convenient option in post-combustion CO₂ capture strategies. Sorbents selection is a key point because the materials are required to be both low-cost and versatile in typical post-combustion conditions in order to guarantee an economically advantageous overall process. This work compares strategies to tailor the chemico-physical features of carbon black (CB) by surface-modification and/or coating with a CO₂-sorbent phase. The influence of the CB microporosity, enhanced by chemical/thermal treatments, is also taken into account. Three CB surface modifications are performed and compared: (i) oxidation and functionalization with amino-groups, (ii) coating with iron oxides and (iii) impregnation with an ionic liquid (IL). The CO₂ capture performance is evaluated on the basis of the breakthrough curves measured at atmospheric pressure and room temperature in a lab-scale fixed bed micro-reactor. Most of tested solids adsorb a CO₂ amount significantly higher than a 13X zeolite and DARCO FGD (Norit) activated carbon (up to 4 times more in the best case). The sorbents bearing basic functionalities (amino-groups and IL) exhibit the highest CO₂ sorption capacity. The use of a microporous carbonaceous support limits the accessibility of CO₂ toward the adsorbing phase (IL or FM) lowering the number of accessible binding sites for CO₂.