CO₂ Capture using phenoxide salts; alternatives to amine-based capture agents, and comparative speciation studies as components in solvent blends

Amine blends represent the leading absorbents for post-combustion CO₂ capture, yet they still have considerable issues associated with their use, such as high energy requirements, corrosivity, cost and toxicity. At least one amine component is usually considered to operate as base, and on this hypothesis phenol (pKa 9.95), as its conjugate base, can potentially act as an amine-free alternative in such blends. We report the first detailed study using phenoxide based capture reagents, including different blends of ethanolamine and potassium phenoxide. CO₂ absorption rate and speciation of these solutions was compared with that of comparable amine blends, and whilst potassium phenolate alone showed poor kinetics, its use in combination with monoethanolamine (MEA) showed interesting and potentially beneficial properties. This work is the first to use phenoxides as a base in CO₂ capture solvents and demonstrates the viability of this diverse family of compounds for industrially relevant CO₂ capture solvents.