Preparation of Nanoporous Carbonaceous Promoters for Enhanced CO2 Absorption in Tertiary Amines

Aqueous solutions of tertiary amines are promising absorbents for CO2 capture, as they are typically characterized by a high absorption capacity, low heat of reaction, and low corrosivity. However, tertiary amines also exhibit very low kinetics of CO2 absorption, which has made them unattractive options for large-scale utilization. Here, a series of novel nanoporous carbonaceous promoters (NCPs) with different properties were synthesized, characterized, and used as rate promoters for CO2 absorption in aqueous N, N-diethylethanolamine (DEEA) solutions. To prepare a DEEA–NCP nanofluid, NCPs were dispersed into aqueous 3 mol·L−1 DEEA solution using ultrasonication. The results revealed that among microporous (GC) and mesoporous (GS) carbonaceous structures functionalized with ethylenediamine (EDA) and polyethyleneimine (PEI) molecules, the GC–EDA promoter exhibited the best performance. A comparison between DEEA–GC–EDA nanofluid and typical aqueous DEEA solutions highlighted that the GC-EDA promoter enhances the rate of CO2 absorption at 40 °C by 38.6% (36.8–50.7 kPa·min−1) and improves the equilibrium CO2 absorption capacity (15 kPa; 40 °C) by 13.2% (0.69–0.78 mol of CO2 per mole of DEEA). Moreover, the recyclability of DEEA–GC–EDA nanofluid was determined and a promotion mechanism is suggested. The outcomes demonstrate that NCP–GC–EDA in tertiary amines is a promising strategy to enhance the rate of CO2 absorption and facilitate their large-scale deployment.