Time-Saving and Cheap Strategy To Prepare Large Mesoporous Materials for Efficient CO₂ Adsorption

Abstract

Compared with other types of adsorbents, solid adsorbents prepared from amine-modified porous materials have good industrial application prospects. The current problem is that the adsorption capacity is low, and its cycle stability is poor. In this paper, LS support was synthesized using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (P123) as a template and sodium silicate (Na2SiO3) as the silicon source via the partitioned collaborative self-assembly process (PCSA) and then compared to three other materials prepared by the traditional method (TS, SS, and SBA-15). CO2 solid adsorbents were prepared by loading tetraethylenepentamine (TEPA). The structure and performance of the samples were investigated using N2 adsorption and desorption, XRD, TEM, TG, SEM, and in-situ FTIR. Compared with the supports prepared by the traditional method, the LS prepared by the PCSA method has a larger pore size. When loaded with the same mass fraction of TEPA, LS has a higher real loading of TEPA and a better CO2 capture performance. The effect of adsorption temperature and amine loading on the CO2 capture performance of the adsorbent was studied. In a mixed gas (N2/CO2 = 85/15) at 90 °C, the maximum CO2 adsorption capacity of LS-TEPA70% reached 5.59 mmol/g. Furthermore, after 10 cycles of adsorption–desorption, the adsorption capacity of LS-TEPA70% was still as high as 4.87 mmol/g, which satisfies the requirements of industrial application. According to the results of in-situ infrared diffuse reflection of the CO2 adsorption process, the TEPA loading mechanism was obtained. By analyzing the relationship between the changes in the strength of the functional groups during the reaction, a CO2 adsorption mechanism with active sites was proposed. Under anhydrous conditions, CO2 first combines with RNH2 or R1R2NH, forming zwitterions. Next, the zwitterion was deprotonated, eventually forming protonated products and carbamate. This study provides a rapid method for the synthesis of large mesoporous materials and high-efficiency carbon dioxide adsorbents.