(664e) Relationship of Solubility and Thermodynamic Parameters for Amine-Containing Non-Regenerative H2S Scavengers

Dan F. Smith Department of Chemical Engineering, Lamar University, P.O. Box 10053, Beaumont, Texas 77710, United States

Removal of H₂S from oil and gas streams has been a priority, oftentimes a necessity, for upstream crude oil/gas facilities for decades. However, the advances in production, namely horizontal drilling and hydraulic fracking, have produced oils and natural gases that contain higher concentrations of H₂S than previously seen. Crudes containing > 0.5 % sulfur are considered sour and must undergo separation and/or conversion processes to lower the H₂S content prior to entering the midstream pipelines and railcars. H₂S scavengers can be categorized into two types: regenerative and non-regenerative. Regenerative scavengers, such as alkanolamines, absorb H₂S using reversible absorption with stripping recovery processes. With non-regenerative scavengers, an irreversible reaction converts the H₂S to form sulfur-containing hydrocarbons. Non-regenerative scavengers are usually aldehydes, ethers, and amines (i.e. acrolein, glyoxal, formaldehyde, alpha-aminoethers, or triazines). Triazine-based scavengers have become the most widely used of the reactive-type scavengers. 1,3,5-hexahydrotriazine is the most frequently used; however, its byproducts equipment fouling, particularly overhead condensers within refineries.

These harmful effects have led to molecular adaptations to the basic triazine molecule whose byproducts would be benign to equipment fouling and corrosion. Varying side chains have the impact of making the triazine scavenger more (or less) soluble in aqueous (or non-polar) crudes. In addition, these side chains could be tailored to be more active for sour gas, rather than sour liquid crude streams. Side chain modifications lead to uncertainty of solubility, liquid/gas interactions, and possible byproduct complications. In this work, solubility and scavenger/ion interactions have been determined for triazines containing ethanolic, amino, bromine, and acrolein substituents, namely 1,3,5-Triacryloylhexahydro-1,3,5-triazine, cyanuric acid, and 1,3,5-Tris(2-hydroxyethyl)cyanuric acid. By adding salts to the mixture, the solubility data yields insightful information towards the ionic mediums in which these materials could be used. Moreover, Setchenow’s coefficient, the octanol/water partition coefficients, and the activity coefficients have been determined to examine the potential fate these scavengers when considering environmental factors. The experimental results and model development will be presented.