Sarcosine

Direct CO₂ capture from the atm. has received growing attention driven by the imperative of achieving global net-zero emission targets.Amino acid salt solutions are promising candidates for liquid-based direct air capture processes.Utilized as a neutralized salt by reacting initially with hydroxides, their performance may vary with the type of counter ion present in the solutionThis work investigates the influence of counter ions, potassium, sodium, and lithium, of different amino acid salt solutions on the phys. properties, the CO₂ absorption capacities, and the CO₂ absorption kinetics under atm. CO₂ concentration levels.The potassium-based amino acid solutions exhibited significantly lower viscosities and mildly elevated densities compared to sodium- and lithium-based solutionsAt 25°, the potassium-prolinate solution demonstrated the highest viscosity (8.5 mPa s), whereas potassium-glycinate exhibited the lowest viscosity (2.5 mPa s).Addnl., potassium-based solutions consistently displayed the highest CO₂ mass transfer coefficients, followed by sodium- and lithium-based solutionsThe CO₂ mass transfer coefficient was the highest for potassium-prolinate (2.99 mmol m^-2/s kPa^-1) with the lowest rate observed for potassium-β-alaninate (1.68 mmol m^-2/s kPa^-1).Interestingly, the type of counter ion had minimal impact on the CO₂ absorption capacity, with potassium-based solutions exhibiting only a slightly elevated capacity compared to sodium- and lithium-based solutionsSpecifically, potassium-lysinate displayed the highest CO₂ absorption capacity (0.7 mol CO₂ /mol amine), while potassium-β-alaninate showed the lowest (0.65 mol CO₂/mol amine).It should be noted that all lithium-based solutions of all amino acids formed precipitates at the equilibrium CO₂ absorption capacity.From a practical and operational perspective, these findings suggest that the potassium salt solution of amino acids would be the optimal choice for direct air capture applications due to their enhanced solubility and CO₂ mass transfer rates compared to the corresponding sodium and lithium counter ion salt solutions