Carbon nanotube silica composite hollow fibers impregnated with polyethylenimine for CO2 capture

The capture of carbon dioxide from flue gases or air using sorption technologies is an adequate means to stop the increase in CO2 emissions that are the main contributor to climate change. Hollow fibers for sorption processes are a promising approach with several improved characteristics such as a decreased pressure drop, lower energy consumption as well as higher CO2 recovery and purity compared to conventional packed-beds. To overcome thermal and chemical limitations of a polymeric matrix we propose carbon nanotube (CNT) based hollow fiber sorbents. Silica particles are dispersed in the CNT network and polyethylenimine is immobilized within the hollow fibers to enhance the sorption performance. Polymeric amines exhibit high CO2 adsorption capacities even at very low partial pressures. The incorporation of silica particles improves the specific surface area of the so-called microtubes from 203.6 m(2) g(-1) to 283.2 m(2) g(-1) and yields a CO2 uptake of 1.92 mmol g(-1) at 0.15 bar CO2 partial pressure. A gas tight polymer layer coated on the shell side allows the use of a thermal moderator for isothermal operation. Adsorption isotherms and kinetics are presented, discussed and fitted applying appropriate models. The results presented here prove the adaptiveness of the carbon nanotube based hollow fibers and emphasize the possibilities they open up as a platform for different sorption tasks that extend beyond carbon capture.