The objective of the work presented here is to develop a nanoporous solid adsorbent which can serve as a "molecular basket" for CO 2 in the condensed form. Polyethylenimine (PEI)-modified mesoporous molecular sieve of MCM-41 type (MCM-41-PEI) has been prepared and tested as a CO 2 adsorbent. The physical properties of the adsorbents were characterized by X-ray powder diffraction (XRD), N 2 adsorption/desorption, and thermogravimetric analysis (TGA). The characterizations indicated that the structure of the MCM-41 was preserved after loading the PEI, and the PEI was uniformly dispersed into the channels of the molecular sieve. The CO 2 adsorption/desorption performance was tested in a flow system using a microbalance to track the weight change. The mesoporous molecular sieve had a synergetic effect on the adsorption of CO 2 by PEI. A CO 2 adsorption capacity as high as 215 mg-CO 2 /g-PEI was obtained with MCM-41-PEI-50 at 75 °C, which is 24 times higher than that of the MCM-41 and is even 2 times that of the pure PEI. With an increase in the CO 2 concentration in the CO 2 /N 2 gas mixture, the CO 2 adsorption capacity increased. The cyclic adsorption/desorption operation indicated that the performance of the adsorbent was stable.

No abstract

Adsorption separation of CO2 from simulated flue gas containing CO2, O2, and N2 with and without moisture was investigated using a novel nanoporous adsorbent based on polyethylenimine (PEI)-modified mesoporous molecular sieve MCM-41 in a flow system. The CO2 adsorption capacity and CO2 separation selectivity of MCM-41 were greatly improved by loading PEI into its nanosized pore channels, which made the resulting adsorbent operating like a “molecular basket” for CO2. CO2 adsorption capacity of the MCM-41-PEI adsorbent for the simulated moist flue gas was higher than that for the simulated dry flue gas. CO2 separation selectivity of the MCM-41-PEI adsorbent was also improved in the presence of moisture when compared with those in the dry gas condition. The influence of moisture concentrations in the simulated flue gas on the CO2 adsorption separation performance was also examined. The results of adsorption/desorption separation cycles showed that the MCM-41-PEI adsorbent was stable over 10 cycles of adsorption/desorption operations. The hydrothermal stability of the “molecular basket” adsorbent was better than that of the MCM-41 support alone.

No abstract