PNNL

Abstract

Water-lean solvents are considered as a promising solution for carbon dioxide (CO2) capture. Candidate CO2 capture molecules include N-(2-ethoxyethyl)-3-morpholinopropan-1-amine (2-EEMPA), 3-methoxy-N-(pyridine-2-ylemthyl)propan-1-amine (MPMPA), and 1-((1,3-Dimethylimidazolidin-2-ylidene)amino)propan-2-ol (1-IPADM-2-BOL). When integrating the water-lean solvents with the separation membrane to form a hybrid system, it would have a higher driving force to pull CO2 through a membrane. In addition, including a membrane in the direct air capture (DAC) system would be able to reduce the evaporation of capture solvents. Therefore, it is important to understand the chemical compatibility of the solvents with the separation membranes to better integrate them into the process for DAC of CO2. Characteristic peaks of water-lean solvents and separation membrane were observed in the static time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra. For example, m/z+ 217.190 C11H25N2O2+, m/z+ 181.132 C10H17N2O+, and m/z+ 172.146 C8H18N3O+, are the protonated 2-EEMPA, protonated MPMPA, and protonated 1-IPADM-2-BOL, respectively. Similarly, the fragment of CO2 separation membrane, m/z+ 263.086 C16H11N2O2+, a synthesized PEEK-ionene, was observed, showing molecular detection of ToF-SIMS. In addition, SIMS analysis was performed to study the solvent and membrane compatibility, indicating new species formed as a result of the interactions. These findings show that the interface between the CO2 separation membrane and water-lean solvents should be studied at the molecular level, because they provide insights into how we could design hybrid systems comprised of CO2 separation membranes and capture solvents. A revised membrane structure would be helpful to improve the compatibility with the existing CO2 capture solvents and facilitate the design of DAC devices in the future.