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 N-2. Results indicate that essentially all the CO2 could be desorbed under mild vacuum levels (12-56 kPa abs) and temperatures (70-100 degrees C). The fastest average desorption rate (3.75 mmol/g/h) was observed at 12 kPa abs/100 degrees 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).