Amino Acid Salts for Carbon Dioxide Capture: Evaluating l‑Prolinate at Desorber Conditions

Vapor–liquid equilibrium (VLE) measurements for unloaded and CO₂-saturated aqueous potassium salt solutions of l-proline have been performed using a high-pressure equilibrium cell. The solubility of CO₂ has been determined at temperatures of 363, 393, and 403 K in 3 and 4 mol dm^–3 aqueous solutions. The CO₂ partial pressures ranged from 3.0 to 358 kPa. In addition, the VLE data for CO₂-free and CO₂-saturated 3 mol dm^–3 aqueous potassium sarcosinate solutions are presented for the same range of temperatures. The vapor pressures of the considered compounds have been determined at temperatures from 353 to 403 K. The reboiler duty required for stripping CO₂ from potassium l-prolinate solutions has been computed by the summation of the desorption enthalpy of CO₂, sensible heat, and evaporation heat associated with co-produced regenerator overhead water vapor. A new approach to calculate the latter contribution is presented. The calculated energy requirements for l-prolinate are in the range reported in the literature for other amino acid salts

Precipitation regime for selected amino acid salts for CO2 capture from flue gases

The tendency of alkaline (sodium, potassium and lithium) salts of taurine, β-alanine, sarcosine and L-proline to form precipitates under varying operational conditions of CO2 absorption has been investigated. CO2 absorption experiments have been performed at 293.15 and 313.15 K, at partial pressures relevant for capturing CO2 from flue gas conditions and amino acid salt concentrations up to the saturation concentration. In addition to this ‘window of operation’ for the (non-) precipitation regime, the identity of precipitates formed was revealed and relevant properties like density of the saturated aqueous amino acid salt solutions at 293.15 K have been determined

Reactive Absorption of Carbon Dioxide in l‑Prolinate Salt Solutions

Aqueous amino acid salt solutions are seen as more sustainable alternative CO₂ solvents compared to conventional alkanolamines. The absorption of CO₂ into aqueous solutions of potassium l-prolinate, over the temperature range of 290–303 K, was studied using a stirred cell. To compare the effect of potassium versus sodium as counterion, the absorption rates of CO₂ in sodium l-prolinate solutions were also determined. The amino acid salt concentration was varied between 0.5 and 3 mol dm^–3. Physicochemical properties such as density, viscosity, and physical solubility of N₂O, required in the interpretation of absorption rate experiments, were determined separately. The obtained experimental reactive absorption fluxes were interpreted, using the pseudo-first-order approach, into intrinsic reaction kinetics. The potassium-based solvent showed, on average, a 32% higher reactivity toward CO₂ than the sodium equivalent. The kinetic data were correlated in a power-law reaction rate expression. The reaction order with respect to the amino acid was found to be between 1.40 and 1.44 for both l-prolinate salts, and the second order kinetic rate constant, <i>k</i>₂, was calculated for the potassium salt to be 93.7 × 10³ dm³·mol^–1·s^–1 at 298 K with an activation energy of 43.3 kJ·mol^–1. l-Prolinate salts show higher chemical reactivity toward CO₂ than most of the amino-alcohols and amino acid salts