Water-Enhanced CO2 Capture with Molecular Salt Sodium Guanidinate

Published

June 4, 2024

Author(s)

Hayden Evans, Marcus Carter, Wei Zhou, Taner N. Yildirim, Craig Brown, Hui Wu

Abstract

Solid-state amine absorbent materials, including those containing guanidine derivatives, have received tremendous attention as the world combats the challenges of climate change. Although these materials are attractive for their selective CO2 capture capacity and fast absorption kinetics, the CO2 absorption mechanism with such materials can be unclear and differs when H2O is present. In this work, we present a detailed study on a model guanidine-based crystalline salt, sodium guanidinate (NaCN3H4), and examine the CO2 absorption with and without humidity. The simple composition and high crystallinity of NaCN3H4 and its carbonate capture products allow us to perform ex-situ and in-situ PXRD to identify possible reaction pathways. These results are complemented by detailed thermogravimetric analysis and gas studies and are used to derive holistic mechanistic insight. We determine that NaCN3H4 exhibits a kinetically controlled CO2 absorption profile with an absorption capacity of ≈ 12.3 mmol CO2/g, assuming a 1:1:1 reaction between CO2, H¬2O, and NaCN3H4. Importantly, humidity is found to significantly lower the activation energy and increase absorption kinetics of CO2 absorption as the products Na2CO3 and (CN3H6)2CO3 form. Our study demonstrates the advantages and drawbacks of using guanidinate materials for CO2 capture under flue gas conditions and provides clarity about how CO2 capture with similar compounds can be enhanced by humidity.

Citation

Chemistry of Materials

Pub Type

Journals

Keywords

CO2 capture, powder diffraction

Citation

Evans, H. , Carter, M. , Zhou, W. , Yildirim, T. , Brown, C. and Wu, H. (2024), Water-Enhanced CO2 Capture with Molecular Salt Sodium Guanidinate, Chemistry of Materials (Accessed June 30, 2024)