Raman and DFT Study of the H₂S Scavenger Reaction of HET-TRZ under Simulated Contactor Tower Conditions

Abstract

Raman spectroscopy is a rapid and noninvasive analytical technique used for the analysis of complex materials in complex matrices. Herein, we report for the first time a combined Raman-DFT study to assign all the vibrational modes associated with the most important species involved in the H 2 S scavenger reaction of HET-triazine under simulated contactor tower conditions. In doing so, we have defined specific peaks or Raman identifier bands (RIBs) to get a complete reaction profile of the H 2 S removal process. Our methodology was able to identify the presence of the elusive 2,2′-(1,3,5-thiadiazine-3,5-diyl)di(ethan-1-ol) (TDZ) intermediate and also provided evidence supporting the formation of the sulfur polymeric deposit from the 2-(1,3,5-dithiazinan-5yl)ethan-1-ol (DTZ) byproduct.

Experimental Study of the Aqueous Phase Reaction of Hydrogen Sulfide with MEA-Triazine Using In Situ Raman Spectroscopy

“…The acquired spectra are shown in Figure S7 in the Supporting Information. As a result of the analysis, the peaks used as indicators of HET, DTZ, and MEA are, respectively, 923, 675, and 840 cm –1 , which are consistent with the information available in the literature. ,, …”

“…The development of the peak at 634 cm –1 is also noted, which shows a maximum point followed by a decrease with the advancement of the scavenging reaction, suggesting to be related to an intermediate product of the series of reactions. This peak may be representative of TDZ, in line with the Raman band associated with TDZ by Perez Pineiro et al . Moreover, Figure shows the relative intensity (with respect to the height of the IS peak) of the selected peaks as a function of time and the fractional conversion of HS – ( X ) corresponding to reactions at pH 0 = 9 and four levels of HET/HS – initial concentration ratios.…”

“…As a result of the analysis, the peaks used as indicators of HET, DTZ, and MEA are, respectively, 923, 675, and 840 cm −1 , which are consistent with the information available in the literature. 15,16,18 Figure 6 shows the evolution of the spectra over time in one of the reaction runs for pH 0 = 9 and an HET/HS − initial concentration ratio of 0.5 in the period between 3 and 6 h of reaction. The selected peaks for HET, DTZ, and MEA are clearly observable in the reaction spectra.…”

“…A few studies recently reported in the literature proposed the use of Raman spectroscopy as a tool for monitoring H 2 S scavenging reactions with HET. − More specifically, Perez Pineiro et al reported the use of Raman spectroscopy for quantitation of HET and DTZ in spent scavenger samples. Furthermore, OndaVia has made available cartridges and instrumentation for the assay of HET and DTZ by Raman spectroscopy .…”

Quantitative Analysis of Triazine-Based H2S Scavengers via Raman Spectroscopy

“…cm −1 peak (asymmetric N−C + C−C stretching + CH 2 rocking), as it is specific to the triazine species. 19 The resulting predictive model is univariate on the 921 rel. cm −1 peak.…”