This study examines the rate of oxidative degradation of MEA under conditions typical of a CO 2 capture process. Experiments examined the effects of amine concentration, CO 2 loading, O 2 concentration, and agitation rate at 55 °C. Degradation rates were quantified by measuring the rate of NH 3 evolution from the amine solutions using FT-IR analysis. Results show that degradation rates are controlled by the rate of physical absorption of O 2 and NH 3 evolution rates ranged from 0.2 to 8.0 mM/h. Previous studies were re-examined and compared to the current study and appear to have been performed under conditions that were mass transfer limited. This would indicate the previous literature values for degradation kinetics were actually O 2 absorption rates. An estimate of the degradation rate for a CO 2 absorber was made assuming the degradation was controlled by the rate of O 2 absorption and was shown to be equal to or less than values reported in the literature.

This study examines the effect of a number of additives on the oxidative degradation of monoethanolamine (MEA) in the presence of dissolved Cu. Additives were selected from three categories: O 2 scavengers and reaction inhibitors, chelating agents, and stable salts. Three proprietary inhibitors have been identified that significantly inhibit the rate of degradation at concentrations below 100 mM. Inhibitor A is a stable compound, while Scavengers B and C are stoichiometrically degraded to products that must be removed in an industrial application. Hydroquinone, ascorbic acid, manganese sulfate, and potassium permanganate all increased the rate of oxidative degradation. EDTA (ethylene-diamine-tetraacetic acid) was an effective chelating agent but lost inhibiting capacity over time. Phosphate was a weak chelating agent. Heat stable salts, including potassium chloride, potassium bromide, and potassium formate, were also ineffective oxidation inhibitors. Potassium formate was the strongest of the stable salts tested and decreased degradation by 15% at 0.55 M.

Room-temperature ionic liquids (RTILs) are regarded as green solvents due to their low volatility, low flammability, and thermal stability. RTILs exhibit wide electrochemical windows, making them prime candidates as media for electrochemically driven reactions such as electro-catalysis and electro-plating for separations applications. Therefore, understanding the factors determining edges of the electrochemical window, the electrochemical stability of the RTILs, and the degradation products is crucial to improve the efficiency and applicability of these systems. We present here computational investigations of the electrochemical properties of a variety of RTILs covering a wide range of electrochemical windows. We proposed four different approaches with different degrees of approximation and computational cost from gas-phase calculations to full explicit solvation models. It was found that, whereas the simplest model has significant flaws in accuracy, implicit and explicit solvent models can be used to reliably predict experimental data. The general trend of electrochemical windows of the RTILs studied is well reproduced, showing that it increases in the order of imidazolium < ammonium < pyrrolidinium < phosphonium giving confidence to the methodology presented to use it in screening studies of ionic liquids.

Intra- and intermolecular force field parameters for the interaction of actinyl ions (AnO2(n+), where, An = U, Np, Pu, Am and n = 1, 2) with water have been developed using quantum mechanical calculations. Water was modeled with the extended simple point charge potential (SPC/E). The resulting force field consists of a simple form in which intermolecular interactions are modeled with pairwise Lennard-Jones functions plus partial charge terms. Intramolecular bond stretching and angle bending are treated with harmonic functions. The new potentials were used to carry out extensive molecular dynamics simulations for each hydrated ion. Computed bond lengths, bond angles and coordination numbers agree well with known values and previous simulations. Hydration free energies, computed from molecular dynamics simulations as well as from quantum simulations with a solvation model, were in reasonable agreement with estimated experimental values.

In alkaline carbonate solutions, hydrogen peroxide can selectively replace one of the carbonate ligands in UO2(CO3)3(4-) to form the ternary mixed U(VI) peroxo-carbonato species UO2(O2)(CO3)2(4-). Orange rectangular plates of K4[UO2(CO3)2(O2)].H2O were isolated and characterized by single crystal X-ray diffraction studies. Crystallographic data: monoclinic, space group P2(1)/ n, a = 6.9670(14) A, b = 9.2158(10) A, c = 18.052(4) A, Z = 4. Spectrophotometric titrations with H 2O 2 were performed in 0.5 M K 2CO 3, with UO2(O2)(CO3)2(4-) concentrations ranging from 0.1 to 0.55 mM. The molar absorptivities (M(-1) cm(-1)) for UO2(CO3)3(4-) and UO2(O2)(CO3)2(4-) were determined to be 23.3 +/- 0.3 at 448.5 nm and 1022.7 +/- 19.0 at 347.5 nm, respectively. Stoichiometric analyses coupled with spectroscopic comparisons between solution and solid state indicate that the stable solution species is UO2(O2)(CO3)2(4-), which has an apparent formation constant of log K' = 4.70 +/- 0.02 relative to the tris-carbonato complex.