Synthesis and optimization of biobased carbon adsorbent monoliths from chitosan-polybenzoxazine for efficient CO2 capture

Abstract

The present study introduces a novel method for the preparation of a CO₂ carbon adsorbent derived from biobased precursors. Porous carbon adsorbents were synthesized through the carbonization and thermal activation of biobased chitosan-polybenzoxazine. First, the study explored the influence of varying amounts of the key polymer precursors, lysine (0.05–0.1 g) and chitosan (0.6–0.12 g), on the surface and adsorption characteristics of the obtained carbons. This aimed to identify the most favourable amounts of these precursors that resulted in the highest CO₂ adsorption performance. In the subsequent stage, the study investigated the impact of different activation times (1–7 h) to enhance the surface characteristics and CO₂ adsorption capacity of the activated carbon. Both carbonization and activation processes were conducted in a tubular furnace at 900 °C under N₂ and CO₂ atmospheres, respectively. After carbonization, the resulting carbon monoliths exhibited a char yield of approximately 49 wt%, with a BET surface area of up to 541 m² g⁻¹ and a CO₂ uptake of 4.0 mmol g⁻¹ at 0 °C and 1 bar. After activation, the obtained samples displayed a surface area in the range of 650–1000 m² g⁻¹, with CO₂ adsorption capacities at 1 bar ranging from 4.5 to 5.6 mmol g⁻¹ at 0 °C and 3.2 to 4 mmol g⁻¹ at 25 °C. The activated carbons also demonstrated excellent selectivities for CO₂/N₂ and CO₂/CH₄ mixtures, along with a stable CO₂ adsorption–desorption performance after 10 cycles.