Functionalization of hierarchically porous silica monoliths with polyethyleneimine (PEI) for CO2 adsorption

A novel CO 2 sorbent was prepared by modifying polyethyleneimine (PEI) on hierarchically porous silica (HPS) monoliths with well-defined macro-mesopores through wet impregnation method. HPS monoliths before and after functionalization were characterized by scanning electron microscopy (SEM), differential thermal analysis/thermogravimetry (DTA/TG), fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption/desorption analysis (BET), and the CO 2 adsorption-regeneration properties of as-synthesized sorbents were investigated by thermogravimetric analysis (TG). The effects of loaded PEI amount as well as adsorption temperature and CO 2 partial pressure on the CO 2 adsorption performance of the as-prepared sorbents were also studied. The results showed that the porous structure of HPS-PEI sorbents was preserved after functionalization, while the specific surface area and pore volume decreased with increasing amount of amines to some extent. The use of PEI had a remarkable improvement on the CO 2 adsorption capacity. With the increasing amount of PEI loaded, the CO 2 adsorption capacity improved significantly. The highest CO 2 adsorption capacity of 2.44 mmol (g sorbent) −1 was obtained at 75 °C in the CO 2 partial pressure of 100 kPa for the HPS loaded with 60 wt% PEI. Adsorption/desorption cycles indicated that the PEI-modified HPS sorbents had a good stability and regeneration.