Mericat Process
In the refining and midstream sectors of the oil and gas industry, mercaptans (thiols, RSH) are among the most troublesome sulfur compounds. They cause objectionable odors, promote corrosion in equipment and pipelines, fail copper strip corrosion tests, and frequently lead to off-spec product rejections. The Mericat™ process, licensed by Merichem Technologies, has become one of the most widely adopted technologies for mercaptan sweetening in liquid hydrocarbon streams since its introduction in the late 1970s.With more than 70 licensed units operating worldwide, Mericat converts corrosive and odorous mercaptans into non-volatile, oil-soluble disulfides (RSSR) through a mild, catalytic oxidation in caustic medium. This article provides a comprehensive overview of the process chemistry, mechanical design, variants, operating parameters, advantages, limitations, and real-world performance.

Core Chemistry

Mericat is an oxidative sweetening process. Mercaptans are first deprotonated in caustic to form mercaptide ions, which are then catalytically oxidized by dissolved oxygen to disulfides:

2 RSH + ½ O₂ → RSSR + H₂O

(overall balanced reaction)

Step-by-step mechanism:

  1. Extraction / deprotonation: RSH + NaOH → RSNa + H₂O
  2. Catalytic oxidation: 4 RSNa + O₂ + 2 H₂O → 2 RSSR + 4 NaOH

The catalyst—typically a water-soluble metal phthalocyanine sulfonate (cobalt or vanadium)—cycles between oxidized and reduced states, enabling efficient oxygen utilization and low caustic consumption (typically 0.1–0.5 lb/bbl treated hydrocarbon).

Mericat mercaptan sweetening process diagram
Mericat™ mercaptan sweetening schematic (single-stage for gasoline/naphtha)

Process Flow and Equipment

The heart of the Mericat unit is the FIBER FILM® Contactor, a bundle of hydrophilic fibers that create an extremely high surface-area film of caustic while the hydrocarbon flows counter-currently. This non-dispersive contact avoids emulsions and allows very efficient mass transfer in a compact vessel.

FIBER FILM Contactor mechanism illustration
FIBER FILM® Contactor: How the thin caustic film forms on fibers for superior mass transfer
Mericat kerosene treatment unit for jet fuel
Kerosene treatment unit integrating NAPFINING™ + MERICAT™ II + AQUAFINING™ for jet fuel production
Mericat J kerosene jet fuel treating unit diagram
MERICAT™ J variant: Kerosene/jet fuel sweetening with integrated acid neutralization and dehydration

Variants and Application Range

Conclusion

The Mericat process remains a workhorse technology for mercaptan sweetening in liquid hydrocarbons due to its balance of capital efficiency, operating simplicity, and proven performance. For refiners, blenders, and condensate processors in regions like the U.S. Gulf Coast—including facilities near Sugar Land, Texas—Mericat offers a robust, low-maintenance solution to meet odor, corrosion, and specification requirements without the complexity of full hydrodesulfurization.

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