Desorption process for capturing CO₂ from air with supported amine sorbent

A polyethylenimine impregnated silica sorbent was evaluated for steam-assisted temperature vacuum swing desorption (TVSD) of CO₂, adsorbed from 420 ppm of CO₂ in N₂. Results indicate that essentially all the CO₂ could be desorbed under mild vacuum levels (12-56 kPa abs) and temperatures (70-100 °C). The fastest average desorption rate (3.75 mmol/g/h) was observed at 12 kPa abs/100 °C at a steam flow rate of 6.2 g/h. In comparison, conventional TVSD under the same conditions only produced an average desorption rate of 0.23 mmol/g/h, confirming the superior kinetics of the steam-assisted process. When adsorption was carried out under humid conditions (1 and 2% mol-H₂O), the co-adsorbed water on the sorbent was observed to slow down the desorption of CO₂, due to the additional energy consumed for the desorption of water. The sorbent displayed excellent stability under the conditions studied, losing only 8% of its capacity after 50 cycles (>1500 h).