Comparison of characteristics and performance between PEI and DETA impregnated on SBA-15 for CO2 capture

Solid amine adsorbents have attracted much attention as a promising alternative to amine scrubbing. However, there have been few studies systematically comparing the differences between adsorbents modified with macromolecular amines and small molecular amines. This study selected polyethyleneimine (PEI) and diethylenetriamine (DETA) to impregnate into SBA-15 and set amine types (PEI and DETA), amine loadings (0%-50%), and temperatures (20-120 degrees C) as parameters, trying to provide advice for amine selection and practical application. The adsorbents modified with DETA had higher amine dispersion, while the adsorbents modified with PEI performed better at thermal stability, adsorption capacity, and adsorption kinetics. SBA-15 modified with 50% PEI could reach a CO2 uptake of 182.11 mg/g and an amine efficiency of 0.353. It also presented superior adsorption kinetics with a peak adsorption rate of 350 mg/(g . min) and could reach 90% CO2 adsorption capacity in 5 min, which controlled the activation energy below 7 kJ/mol. What's more, the modified adsorbent had excellent cyclic stability, showing only 6.14% decay after 30 cycles. The double-exponential model was also investigated to explain the inherent properties. The 50%-PEI-modified SBA-15 proved to be a promising and efficient solid adsorbent for CO2 capture.