Kinetics of carbon dioxide absorption into aqueous amine amino acid salt: 3-(methylamino)propylamine/sarcosine solution

A string of discs contactor apparatus was used to measure the CO₂ absorption kinetics into an unloaded aqueous amine amino acid salt, 3-(methylamino)propylamine/sarcosine, SARMAPA solution. The solution was prepared by mixing equinormal proportions of sarcosine, SAR and 3-(methylamino)propylamine, MAPA. Experiments were carried out for the concentration range 1.0–5.0 kmol m⁻³ and for temperatures 25–62 °C. The termolecular mechanism was applied to interpret the experimental data after correcting for non-idealities from the ionic strength using an ionic correction factor. A model correlation without the ionic strength correction was found not to give a good fit to the experimental data. The reaction rate constant for aqueous SARMAPA was determined and found to be comparable to values for amines. It increases significantly with temperature and concentration. The reaction rate constant for water is higher in the SARMAPA system than in amine systems indicating that water contributes significantly to the overall absorption rate and more than in amine systems. The reaction order with respect to the amino acid salt, SARMAPA, concentration varies from 1.06 to 1.43 with an average value of 1.21. A simplified approach applied to the complex speciation chemistry of the amine amino acid salt, AAAS, system gave a good representation of the experimentally observed kinetic rate constant.