A novel blended amine functionalized porous silica adsorbent for carbon dioxide capture

In order to accomplish efficient CO2 capture, poly(ethyleneimine) (PEI) and tetraethylenepentamine (TEPA), with commonly used and inexpensive, was codispersed into the as-prepared SBA-15 (SBA-15(p)) to prepared blended amine functionalized adsorbent. The influence of the mass ratio of PEI to TEPA on the adsorption property was investigated. The promoting effects of TEPA on CO2 capture property were investigated. The adsorbents were characterized using N2 adsorption/desorption, Fourier transform infrared spectroscopy (FTIR), Transmission electron microscope (TEM) and in situ diffuse reflectance infrared fourier transform spectroscopy (in situ DRIFTS). Among the prepared adsorbents, the SBA-15(p) with 30 wt% PEI and 40 wt% TEPA has the CO2 capture capacity of 4.64 mmol/g and the optimal amine efficiency (0.359 molCO2/molN) at 75 °C with 20 vol% CO2 in N2. The addition of TEPA species could improve the CO2 adsorption amount with high amine utilization. The P123 with wheel-like distribution in SBA-15(p) promotes the CO2 capture by optimizing the accessibility of amine to the CO2. After 15 adsorption cycles, the SBA-15(p) with 40 wt% PEI and 30 wt% TEPA has better reusability and cyclic performance, the adsorption capacity can keep around 4.13 mmol/g. The result indicated that more PEI in the adsorbent would improve the adsorbent cyclic stability. Meanwhile, the in-situ DRIFTS results suggested that the reaction of CO2 molecule with the amine active sites in the adsorbent, agrees with anionic and cationic mechanisms.