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 degrees C by 38.6% (36.8-50.7 kPa.min(-1)) and improves the equilibrium CO2 absorption capacity (15 kPa; 40 degrees 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. (C) 2020 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company.