Synthesis of sulphur enriched carbon monoliths for dynamic CO2 capture

Abstract

Advanced and effective adsorbents synthesized via cost-effective methods are needed for CO2 capture applications. Heteroatom doping is regarded as one of the major factor of the porous carbons for efficient CO2 adsorption. In the present study, oxygen and sulfur enriched carbon monoliths were prepared using nanocasting technique followed by chemical activation method. Low-cost phenol-formaldehyde (PF) resin and sodium thiosulphate were chosen as the carbon and sulfur source, respectively. The surface area of the monolithic carbons varied from 390 to 510 m2 g−1 and sulfur content was 2.89 wt% in the S-doped monolith. The effect of different adsorptive operating conditions i.e. adsorption temperatures and CO2 concentrations on the CO2 capture capacities were evaluated. The nanocasted monoliths exhibited excellent dynamic adsorption capacities (1.35–2.10 mmol g−1), which are much greater than in the case of direct carbonized PF sample (0.97 mmol g−1). This is ascribed to the fact that the surface area gets enhanced by implementing nanocasting method whereas the incorporation of oxygen and sulfur functionalities increases the basic character of the monoliths. The as-prepared monolith shows the stable and excellent regenerability over subsequent adsorption and desorption cycles. Moreover, the Temkin isotherm model best fitting with adsorption data indicates the heterogeneous surface of the monoliths. Combined with the effective synthesis of the monoliths, high CO2 uptake, and easy regenerability could make it a most suitable material for CO2 adsorption in the practical applications.