Amphilic Water‐Lean Carbon Capture Solvent Wetting Behavior through Decomposition by Stainless‐Steel Interfaces

Abstract

A combined experimental and theoretical study has been carried out on the wetting and reactivity of water-lean carbon capture solvents on the surface of common column packing materials. Paradoxically, these solvents are found to be equally able to wet hydrophobic and hydrophilic surfaces. The solvents are amphiphilic and can adapt to any interfacial environment, owing to their inherent heterogeneous (nonionic/ionic) molecular structure. Ab initio molecular dynamics indicates that these structures enable the formation of a strong adlayer on the surface of hydrophilic surfaces like oxidized steel which promotes solvent decomposition akin to hydrolysis from surface oxides and hydroxides. This decomposition passivates the surface, making it effectively hydrophobic, and the decomposed solvent promotes leaching of the iron into the bulk fluid. This study links the wetting behavior to the observed corrosion of the steels by decomposition of solvent at steel interfaces. The overall affect is strongly dependent on the chemical composition of the solvent in that amines are stable, whereas imines and alcohols are not. Moreover, plastic packing shows little to no solvent degradation, but an equal degree of wetting.

Advanced Theory and Simulation to Guide the Development of CO2 Capture Solvents

“…This amounts to selecting a solvent with low contact angles and surface tension and a packing material with reduced degradation effects. Due to lower water content, water-lean solvents exhibit lower surface tension and consequently lower contact angles than aqueous solvents . Water-lean solvents also display comparable wetting behavior on hydrophilic (e.g., steel) and hydrophobic (e.g., plastic) surfaces, as illustrated in Figure .…”

“…Removing or passivating the metal interface has been shown to reduce degradation activation energies, e.g., thermal, oxidation, or hydrolysis, and increase solvent lifetime up to 50%. AIMD simulations have demonstrated that replacing the metal with plastic reduces the strength of solvent–interface interactions, which consequently reduces intermolecular and molecule–surface proton transfer processes that could promote degradation …”

“…Reprinted with permission from Nguyen, M.-T.; Grubel, K.; Zhang, D.; Koech, P. K.; Malhotra, D.; Allec, S. I.; Rousseau, R.; Glezakou, V.-A. ; Heldebrant, D. J. Amphilic Water-Lean Carbon Capture Solvent Wetting Behavior through Decomposition by Stainless-Steel Interfaces, ChemSusChem 2021 , 14 (23), 5283–5292 (ref ). Copyright 2021 Wiley-VCH GmbH.…”

“…Due to lower water content, water-lean solvents exhibit lower surface tension and consequently lower contact angles than aqueous solvents. 145 Water-lean solvents also display comparable wetting behavior on hydrophilic (e.g., steel) and hydrophobic (e.g., plastic) surfaces, as illustrated in Figure 6. Removing or passivating the metal interface has been shown to reduce degradation activation energies, e.g., thermal, oxidation, or hydrolysis, and increase solvent lifetime up to 50%.…”

“…AIMD simulations have demonstrated that replacing the metal with plastic reduces the strength of solvent−interface interactions, which consequently reduces intermolecular and molecule−surface proton transfer processes that could promote degradation. 145 Structural Heterogeneity. Structural heterogeneity is an intriguing property observed in many CCSs.…”