The influence of pore size and pore structure of silica-based material on the amine-modified adsorbent for CO2 capture

Silica impregnated with amines has attracted much attention as a promising alternative to amine scrubbing. This study selected SBA-15, MCM-41, and MCM-48 as support materials and set amine types (PEI and DETA), amine loadings (20-45 %), and temperatures (40-120 degrees C) as parameters, systematically exploring the influence of pore size and pore structure on the adsorption performance. The pore size and pore structure had little impact on the type of chemical functional group and thermal stability, but played an important role in the CO2 adsorption capacity as well as the response of adsorption performance to temperature and amine. By comparison, the silica with large pore sizes was more suitable for PEI, while the silica with small pore sizes was more suitable for DETA. The hexagonal mesoporous structure was congenial to DETA and low PEI loading, while the cubic mesoporous structure was congenial to high PEI loading. The small pore size and the cubic mesoporous structure were proven to maintain the promotion effect of the adsorption temperature, while the hexagonal mesoporous structure could relieve the amine volatilization during the adsorption-desorption cycles. The cubic mesoporous structure could inhibit the generation of urea. By comparison, SBA-15 modified with 45 % had excellent performance, reaching a CO2 uptake of 160.55 mg/g and an amine efficiency of 0.360. This product could also control the total percentage of CO2 uptake lost after 30 cycles within 2.0 %, demonstrating the potential for practical application.