Field Crystallization of MEA-Dithiazine: Identifying Materials, Leveraging H–Bonding Synthons, and Opportunities for Crystallization Inhibition

Abstract The operational production of crude oil inevitably involves the co-production of unwanted materials that must be resolved, e.g., produced brine, solids, gases, hydrogen sulfide, etc. Hydrogen sulfide is a particularly noxious and hazardous gas often encountered in oil production, and various methods, including chemical, engineering, or combinations thereof, have been developed to address the challenge. Despite the longevity of the H2S scavenging problem, practical and economical solutions for treating H2S are still sought by the industry. MEA-triazine (1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine) is a routine chemical scavenging treatment for removing H2S in production operations. MEA-triazine readily reacts with H2S under field conditions to form MEA-dithiazine as a H2S scavenged product. Operationally, the resultant MEA-dithiazine is removed from the system and disposed of in an injection well. However, under certain conditions, the MEA-dithiazine is known to form crystalline masses that can result in significant fouling within piping, separators, and even static mixers. Field crystallization of MEA-dithiazine was observed, and the material was collected. The crystals were unambiguously identified as the MEA-dithiazine dimer through single-crystal x-ray crystallography (Schultheiss et al., 2022). As an alternative to solvent or hot water washes to remove the problematic crystallized MEA-dithiazine, a concept was envisaged to leverage molecules that are disruptive to the H-bonding patterns that result in the crystallization of MEA-dithiazine. A series of hydrogen-bonding donor-acceptor small molecules, along with various polymeric materials, were identified and evaluated as disruptors to aid in mitigating field crystallization. This initial study describes identifying and testing a series of small organic molecules and larger polymeric materials as network disruptors to inhibit MEA-dithiane crystallization. Identifying cost-effective molecules that can disrupt the H-bonding and prevent MEA-dithiazine crystallization holds promise to prevent MEA-dithiazine fouling in field operations. In addition, such a solution may provide a cost-effective alternative to labor-intensive solvent and hot water washes.