Characterization of products from the chemical removal of thiol in hydrocarbon streams using DART-MS and NMR spectroscopy

Abstract

Removing sulfide species in the oil and gas industry is a fundamental factor in guaranteeing safety and efficiency in up-stream and downstream operations. Among these, hydrogen sulfide is considered one of the most important sulfur contami-nants hence its removal from production fluids has had a wide coverage in scientific literature. This has not been the case for the less abundant thiols, commonly referred as mercaptans. In this case, the studies reported on the reaction of thiol removal, and the characterization of their final products have been scarce. To delve deeper into this topic, we have carried out a study aimed at the identification and structural characterization of the main products of the reaction between ethanethiol and several commercial compounds known for acting as non-regenerative scavengers of sulfide species in oil and gas applications. To achieve this goal, we have combined for the first time the use of direct analysis in real time-mass spectrometry (DART-MS) with 1D and 2D nuclear magnetic resonance (NMR) experiments for the rapid detection and complete structural characterization of the products generated during the chemical removal of thiols. The results obtained shed new light on the reaction mechanism of thiol scavengers, particularly MBO and those having the hexahydro-1,3,5-triazine moiety as the central core. In addition, the advantages of using DART-MS for a rapid mass spectral analysis of this type of reaction are also highlighted.