The merox unit is a proprietary UOP technology that selectively sweetens petroleum products by oxidizing the foul smelling mercaptans into the sweeter disulphides which remain in the product, leaving the total sulfur content the same. The process is sometimes known as a sweetening process and is much cheaper to install than a hydrotreater which actually lowers the sulphur content.

Merox is primarily used to sweeten mercaptans from jet fuel or from LPG.

In the merox process, the mercaptan is oxidized by means of a proprietary UOP catalyst, in an alkaline environment.

The merox process is preferred for jet fuel sweetening over hydrotreating because it is less expensive and jet fuel's high sulfur limit (3000 ppm) does not require the removal of the other sulfur compounds that hydrotreating provides.