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Merox is an acronym for mercaptan oxidation. It is a proprietary catalytic chemical process developed by UOP used in oil refineries and natural gas processing plants to remove mercaptans from LPG, propane, butanes, light naphthas, kerosene and jet fuel by converting them to liquid hydrocarbon disulfides.

The Merox process requires an alkaline environment which, in some process versions, is provided by an aqueous solution of sodium hydroxide (NaOH), a strong base, commonly referred to as caustic. In other versions of the process, the alkalinity is provided by ammonia, which is a weak base.

The catalyst in some versions of the process is a water-soluble liquid. In other versions, the catalyst is impregnated onto charcoal granules.

Processes within oil refineries or natural gas processing plants that remove mercaptans and/or hydrogen sulfide (HS) are commonly referred to as sweetening processes because they results in products which no longer have the sour, foul odors of mercaptans and hydrogen sulfide. The liquid hydrocarbon disulfides may remain in the sweetened products, they may be used as part of the refinery or natural gas processing plant fuel, or they may be processed further.

Especially when dealing with kerosene, the Merox process is usually more economical than using a catalytic hydrodesulfurization process for much the same purpose. Indeed, it is rarely (if ever) required to reduce the sulphur content of a straight-run kerosene to respect the sulphur specification of jet fuel as the specification is 3000 ppm and very few crude oils have a kerosene cut with a higher content of sulphur than this limit.