N- and S-Doped Carbons Derived from Polyacrylonitrile for Gases Separation

The CO2 capture using adsorption can reduce the carbon footprint, increasing the sustainability of the process without the production of wastes present in commonly used industrial operations. The present research work analyses the effect of the doping-agents incorporation in carbon materials upon adsorption and separation of gases, specifically for carbon dioxide and nitrogen. The carbons precursor was polyacrylonitrile (PAN), which enabled the incorporation of nitrogen atoms in the structure, whereas sulphur doping was reached using pure sulphur after the carbonisation step. The influence of several variables (such as temperature or pressure) and characteristics of synthesised materials (mainly corresponding to surface characteristics) on carbon dioxide separation has been evaluated. Adsorption isotherms were determined for each gas (CO2 and N-2) at different temperatures and pressures. Different adsorption models were evaluated to fit the experimental data. In general, the Toth isotherm described better the adsorption for both gases. Important parameters such as CO2/N-2 selectivity and heat of adsorption were determined using the IAS theory and the experimental isotherms at different temperatures, respectively. Non-activated carbons generated from PAN carbonisation without sulphur addition showed the highest values of selectivity (up to 400) and adsorption heat (up to 40 kJ mol(-1)), mainly at low pressures and at low carbon dioxide uptakes, respectively. Furthermore, thanks to their high adsorption capacity, these carbons can be applied for carbon dioxide separation from mixtures with nitrogen.

Automated summary

This study analyzes the effect of doping agents in carbon materials on the adsorption and separation of carbon dioxide. The results show that non-activated carbons doped with sulfur exhibit high selectivity and adsorption heat values, making them suitable for carbon dioxide separation from nitrogen mixtures.