Preparation optimization of carbon nanotube/carbon fiber incorporated carbon composite monoliths for high CO2 adsorption capacity

Carbon nanotube (CNT) /carbon fiber (CF) incorporated carbon composite monolith adsorbents have been recently reported exhibiting superior CO2 adsorption properties for post-combustion capture (PCC) of CO2. Here we conducted a detailed study on optimization of preparation of CNT/CF composites for high CO2 adsorption capacities. A well-developed narrow microporous (<1 nm) structure is the key to achieving the high CO2 uptake of composite adsorbents at 298K and under ambient and low CO2 pressures. Using water as the solvent for composite mixing is more favorable for enhanced narrow microporosity and CO2 adsorption capacity. The addition of CF lowers the CO2 uptake of CNT composites and the CNT alone incorporation with a CNT/resin ratio of 1 wt% was found preferable. The burn-off as an indicator of degree of CO2 activation was optimized to be 20–30 wt% for the highest CO2 uptake at ambient pressure, whereas the lower burn-off at 10–20 wt% resulted in the largest amount of CO2 adsorbed at 114mmHg (corresponding to 15% of CO2) relevant to the flue gas condition for PCC. The CO2 adsorption capacity is significantly influenced by the narrow micropore size distribution and closely related to the pore volume of effective narrow micropores responsible for different adsorption pressures. The results obtained from this study are valuable to the development of other microporous carbons for CO2 capture.