Polyethyleneimine-nano silica composites: a low-cost and promising adsorbent for CO2 capture

Adsorbents for CO2 captured with nano silica as support were synthesized by impregnating polyethyleneimine (PEI) into nano silica. For impregnation of PEI into nano silica, the 2-40 nm pore of silica support plays an important role in the synthesis process of adsorbents. The PEI loading content, adsorption temperature and CO2 partial pressure influenced CO2 adsorption capacity and PEI utilization efficiency. At 105 degrees C and under 1 atm CO2 partial pressure, the adsorbent with 60% PEI loading content obtained a CO2 adsorption capacity of 186 mg g(-1) adsorbent and a PEI utilization efficiency of 304 mg g(-1) PEI. The CO2 cycling adsorption-desorption was tested under the condition as follows: adsorption at 90 or 105 degrees C under pure CO(2)and desorption at 120 degrees C under pure N-2 showed relatively good adsorption-desorption stability, and no evident deactivation of amines was observed under this condition. However, for adsorption at 90 or 105 degrees C under pure CO2 and desorption at 135 or 150 degrees C under pure CO2, evident deactivation of amines occurred, and the formation of linear or cyclic urea is one reason which led to the decrease of CO2 adsorption capacity.