Temperature- and pH-Dependent Kinetics of the Aqueous Phase Hydrogen Sulfide Scavenging Reactions with MEA-Triazine

A novel kinetic model for the aqueous phase hydrogen sulfide scavenging reactions using MEA-triazine (HET) is proposed. The assumptions of the model are based on experimental observations obtained by NMR spectroscopy, supporting the existence of 3,5-bis(2-hydroxyethyl)hexahydro-1,3,5-thiadiazine (TDZ) as a quantitative reaction intermediate and showing the protonation behavior of HET and the lack of protonation of 5-(2-hydroxyethyl)hexahydro-1,3,5-dithiazine (DTZ). Experimental kinetic data were obtained with a new in situ Raman spectroscopy setup, which enabled monitoring the time-variation of bisulfide concentrations in a batch stirred reacting system at temperatures of up to 75 °C for HET/HS⁻ initial t ti ti f 0 5 t 5 Th ti l d l t were regressed from the experimental data using a brute force optimization method. The rate constants of the first and second scavenging reactions were estimated to be 0.435 and 0.004 L mol⁻¹ s⁻¹ at 25 °C, and the activation energies were 68 and 57 kJ mol⁻¹, respectively (Figure Presented).