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O Captain! Mercaptan! - As Crude Oil Exports Grow, the Mercaptans Issue Can't Be Ignored

Crude oil quality has been a hot topic lately. With the increase in waterborne activity along the Gulf Coast, a high-quality barrel is desired now more than ever. Permian WTI exports have continued to increase as production rises and refining capacity remains relatively stagnant (outside of ExxonMobil’s recent Beaumont expansion). This has resulted in more scrutiny on Permian quality and more concerns rising to the surface — both from the pockets of lower-quality WTI produced at the wellhead and from blending by market participants, as many midstream providers and traders have become efficient at capturing arbitrage opportunities. Recent WTI quality concerns have primarily been around metal content, hydrogen sulfide (H2S) and mercaptans, while nitrogen has become a major issue in the natural gas market. In today’s RBN blog, we look at the issue of mercaptans in WTI.

Let’s start with the basics. Mercaptans are naturally occurring contaminants in crude oil and natural gas — also called thiols, mercaptans are organic compounds bonded to sulfur. Their presence can range from a few parts per million (ppm) to several thousand ppm. While mercaptans are undesirable in crude oil (for reasons we’ll get to in a moment), they do have some commercial applications. Some non-corrosive mercaptans are injected into natural gas to provide a distinctive “rotten-egg” odor to help detect leaks, and another type of mercaptan is used to produce methionine, which serves as an intermediate in the production of pesticides, fungicides and animal feed additives.

Mercaptans are problematic in crude oil because they can be corrosive, which can have negative implications for pipelines and refining equipment. For refiners, high mercaptan content presents significant risk for loss of catalyst activity, and negating the catalyst lowers the overall quality of the fuel and decreases the yield. Further, the presence of mercaptans can decrease the life of the catalyst, creating unplanned downtime and costs for the refiner. Lastly, the tendency for mercaptans to create very pungent odors during refining is also an issue, especially for refiners near residential and commercial areas.

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