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Amine blends represent the leading absorbents for post-combustion CO 2 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. CO 2 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 CO 2 capture solvents and demonstrates the viability of this diverse family of compounds for industrially relevant CO 2 capture solvents.

The chemical degradation of poly(2,5-(4,4’-(hexafluoropropylidene)diphenyl)-1,3,4-oxadiazole) (F-POD) was studied in wet acidic media using a variety of analytical techniques. It was found that in aqueous acidic solution, F-POD degradation increased with higher acidity (lower pH) and can reach levels of up to 20% in mild acidic conditions (pH 5.5). Furthermore, residual water present in chloroform was found to be capable of inducing degradation in the fluorinated polymer as well. A mechanistic explanation of the hydrolysis is proposed, which implicates the electron withdrawing effect of the hexafluoroisopropylidene group in the oxadiazole ring opening. The initially linear polymer is suggested to be transformed into a bi- or three-dimensional polymer (i.e., a branched or cross-linked structure) due to the attack of 1,3,4-oxadiazole ring by carboxylic hydrazide, causing a considerable loss of its solubility in organic solvents. Finally, we demonstrate that F-POD is susceptible to cross-link via relatively simple chemistry.

The present study has demonstrated that Electrical Impedance Spectroscopy (EIS) and Electrical Impedance Tomography (EIT) are viable measurement techniques to be used in the measurement and monitoring of carbon dioxide absorption across the scales. EIS is able to provide information regarding the absorption of carbon dioxide gas on the molecular level hence can be used to search for the optimal system by studying the kinetics of the absorption process and measuring the solubility of carbon dioxide in different solvents of interest. EIT, however, is more suited to studying the absorption on the macro-scale of the process in terms of aspects such as homogeneity of absorption thus can be used to look at the design of the absorption columns themselves. In the present study the experiments were restricted to studying the absorption of carbon dioxide in water as it was found that the conductivity of industrially relevant solvents such as monoethanolamine was too high for use with the conventional EIT hardware.