Microporous phenol–formaldehyde resin-based adsorbents for pre-combustion CO2 capture

Different types of phenolic resins were used as precursor materials to prepare adsorbents for the separation of CO2 in pre-combustion processes. In order to obtain highly microporous carbons with suitable characteristics for the separation of CO2 and H2 under high pressure conditions, phenol–formaldehyde resins were synthesised under different conditions. Resol resins were obtained by using an alkaline environment while Novolac resins were synthesised in the presence of acid catalysts. In addition, two organic additives, ethylene glycol (E) and polyethylene glycol (PE) were included in the synthesis. The phenolic resins thus prepared were carbonised at different temperatures and then physically activated with CO2. The carbons produced were characterised in terms of texture, chemical composition and surface chemistry. Maximum CO2 adsorption capacities at atmospheric pressure were determined in a thermogravimetric analyser. Values of up to 10.8 wt.% were achieved. The high-pressure adsorption of CO2 at room temperature was determined in a high-pressure magnetic suspension balance. The carbons tested showed enhanced CO2 uptakes at high pressures (up to 44.7 wt.% at 25 bar). In addition, it was confirmed that capture capacities depend highly on the microporosity of the samples, the narrow micropores (pore widths of less than 0.7 nm) being the most active in CO2 adsorption at atmospheric pressure. The results presented in this work suggest that phenol–formaldehyde resin-derived activated carbons, particularly those prepared with the addition of ethylene glycol, show great potential as adsorbents for pre-combustion CO2 capture.