Post-combustion carbon capture using amine-based solvents faces challenges like oxidative degradation. O₂ is a ubiquitous component in flue gases and induces irreversible oxidation reactions in the amines, reducing CO₂ capture efficiency and increasing corrosion and maintenance costs. This study proposes monitoring dissolved O₂ (DO) to estimate the solvent oxidation behaviour, avoiding complex chromatographic methods. The approach assumes that oxygen is exclusively consumed by the initial amine during the oxidation process, linking the oxygen depletion kinetics with the amine-oxidation kinetics. DO measurements in monoethanolamine (MEA) reveal significant insights into the kinetics of the oxidative degradation process. CO₂ presence, investigated across different temperatures, accelerates O₂ depletion compared to unloaded samples, though there is no clear correlation between the amount of CO₂ loading and O₂ depletion rates. Making MEA more acidic accelerates oxygen depletion rates; still, the change in pH alone is unable to reproduce the DO rates observed in CO₂-loaded MEA. Higher temperatures accelerate the MEA oxidation. Metal contamination through iron sulphate and iron nitrate accelerates O₂ consumption rates, with the amount of iron being more relevant than the oxidation state of the iron in the original salt or the salt counterion. The influence of viscosity and chelators was studied by adding glycerol and chelating agents as additives, but the results were challenging to interpret. Initial measurements of MEA-Water-glycerol and MEA-Fe-chelating agent mixtures unexpectedly accelerate O₂ consumption, challenging assumptions about the glycerol's role as a non-reactive solvent and chelating agents as oxidation inhibitors. It is revealed through blank experiments that glycerol also oxidises in MEA mixtures, breaking the link between DO decay and MEA consumption, while the tested iron complexes act rather as oxidation catalysts. ... Read more

Correction for ‘Experimental investigation and thermodynamic modelling assessment of the AECl2–NdCl3 (AE = Sr, Ba) systems’ by D. C. Alders et al., Phys. Chem. Chem. Phys., 2024, 26, 24041–24057, https://doi.org/10.1039/D4CP01784F.

The reference list in the originating article was incorrect. The correct list of references is shown here.

The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. ... Read more

The thermodynamic and thermo-physical properties of the binary salt systems AECl₂–NdCl₃ (AE = Sr, Ba) have been investigated using an experimental and modelling approach. The binary salt systems both include a single intermediate salt, i.e. Sr₉Nd₅Cl₃₃ and Ba₃Nd₂Cl₁₂, respectively. The structure of these intermediates has been investigated with X-ray diffraction (XRD). Furthermore, these systems exhibit mutual solubility of NdCl₃ in BaCl₂ and SrCl₂. The investigation of these solid solutions has been performed using quenching experiments and subsequent post-characterisation by XRD. Phase diagram equilibria have also been investigated using differential scanning calorimetry (DSC). Using the aforementioned information on phase transitions, intermediate compound formation, and solid solubility, thermodynamic assessment of the systems has been performed using the CALPHAD method. The model for the Gibbs energy of the liquid solution is the quasi-chemical formalism in the quadruplet approximation, while the model for the Gibbs energy of the solid solutions is the two-sublattice polynomial model. ... Read more