Raman Spectroscopy for Monitoring Aqueous Phase Hydrogen Sul-phide Scavenging Reactions with 1,3,5-tri-(2-hydroxyethyl)-hexahydro-s-triazine
Authors
Johansen, Leah Nygaard ; Kloster, Lykke
Term
4. term
Education
Publication year
2019
Submitted on
2019-06-07
Pages
120
Abstract
I offshore olie- og gasindustrien bruges vandige triazinopløsninger som scavengers til at fjerne den giftige gas svovlbrinte (H2S). Selvom triazin har været brugt i årtier, findes der kun begrænsede data om reaktionskinetikken. Dette projekt havde til formål at udvikle en metode og en forsøgsopstilling til at indsamle kinetiske data ved hjælp af Raman-spektroskopi og at vurdere, om metoden kan bruges til online (real-time) overvågning af vandfasereaktionen mellem 1,3,5-tri-(2-hydroxyethyl)-hexahydro-s-triazin (HET) og hydrosulfid (HS−). Raman-spektroskopi viste udvikling af specifikke toppe i spektrene, som indikerede, at reaktionen forløb. Ved at koble toppeintensitet til koncentrationerne af HET og HS− var det muligt at kvantificere forbruget af reaktanter over tid. Forsøg ved pH 10,3–8,5 viste, at reaktionen er pH-afhængig og hurtigere ved lavere pH; ved pH 11 blev der ikke observeret nogen reaktion inden for to timer. HS−/HET-konverteringsforhold mellem 1 og 2 tyder på, at en sekundær scavenger-reaktion finder sted, identificeret som reaktionen mellem thiadiazin og HS−. Fire forskellige opstillinger med forskellig syretilsætning blev testet; ingen var tilstrækkelige, da de alle havde uoverstigelige ulemper. På baggrund af de eksperimentelle data foreslås et kinetisk udtryk, der afhænger af koncentrationerne af H+ og HET.
In the offshore oil and gas industry, aqueous triazine solutions are commonly used as scavengers to remove the toxic gas hydrogen sulfide (H2S). Although triazines have been used for decades, there is limited kinetic data for the scavenging reaction. This project aimed to develop a method and experimental setup to obtain kinetic data using Raman spectroscopy and to assess whether it can be used for online (real-time) monitoring of the aqueous-phase reaction between 1,3,5-tri-(2-hydroxyethyl)-hexahydro-s-triazine (HET) and hydrosulfide (HS−). Raman spectroscopy showed the emergence of specific spectral peaks indicating the reaction. By relating peak intensities to the concentrations of HET and HS−, it was possible to quantify reactant consumption over time. Experiments at pH 10.3–8.5 indicated that the reaction is pH dependent and proceeds faster at lower pH; at pH 11 no reaction was observed within two hours. HS−/HET conversion ratios between 1 and 2 indicate a second scavenging reaction, identified as the reaction between thiadiazine and HS−. Four setups that differed in how acid was added were tested; none proved adequate because each had major drawbacks. Based on the experimental data, a kinetic expression dependent on the concentrations of H+ and HET is proposed.
[This summary has been rewritten with the help of AI based on the project's original abstract]
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