Influence of CO2 adsorption temperature using cross-linked polyamine adsorbents

https://doi.org/10.1039/D1MA01072G

” In a similar trend as for E200-FZ, the resulting adsorbent – which had a surface area of 246 m² g⁻¹ – reached its optimum CO₂ capacity of 2.30 mmol g⁻¹ at 30 °C, in 1 atm CO₂. Adsorption at 60 °C resulted in reduced uptake at all CO₂ partial pressures to 1 atm.⁴⁷ Huang et al. reported nanoporous crosslinked divinylbenzene-maleic anhydride copolymers functionalised with covalently bonded ‘bridging’ amines which exhibited an improved adsorption performance with lower temperature.⁴⁸ The diethylenetriamine (DETA) grafted-copolymer, HCP-D, displayed both micro- and meso-porosity and a surface area of 343 m² g⁻¹. Its uptake under pure CO₂ at 1 bar was 1.30 mmol g⁻¹ at 25 °C, increasing to 1.53 mmol g⁻¹ at 0 °C. Sun and co-workers also utilised small amine molecules, producing polyamine adsorbents from cross-linking diamines with 2,4,6-tris(chloromethyl)-mesitylene (TCM). NUT-1, synthesised from ethylene diamine (ED), adsorbed 1.43 mmol g⁻¹ at 25 °C, raising to 1.87 mmol g⁻¹ at 0 °C, under 1 bar CO₂.⁴⁹ From the same group, Mane et al. also observed CO₂ adsorption increase inversely with temperature, in the performance of NUT-11, again synthesised using TCM, except this time to cross-link PEI (M_w 1800).⁵⁰ This microporous adsorbent had a surface area of 598 m² g⁻¹. Its CO₂ uptake at 25 °C was 2.23 mmol g⁻¹, and 4.52 mmol g⁻¹ at 0 °C. Its Q_st value was between 46–49 kJ mol⁻¹, more strongly indicative of physisorption rather than chemisorption – or it may be accessing both phenomena.”