This is an acronym for mercaptan oxidation. This is a proprietary process developed by Universal Oil Products (UOP). It is used by oil refineries and gas processing plants to remove mercaptans from the LPG, propanes, butanes, light naptha, kerosene, and jet fuel by converting then to liquid hydrogen disulfides.
The process requires an alkaline environment. In such a case the environment is generated by either sodium hydroxide or ammonia. The sodium hydroxide is the stringer of the two. Often the sodium hydroxide is referred to as caustic. I think from my observations here we use sodium hydroxide.
The catalyst used may be water soluble or impregnated in charcoal.
The reaction is an oxidizing reaction. It converts the mercaptans to disulphides.
4RSH + O2 => 2RSSH + H2O – eqn. 1
The Conventional Merox Process
This is a process lasting two steps;
The first step involves the feedstock being brought into contact with aqueous caustic solution. This tray contains UOPs propriety catalyst. The caustic solution reacts with the mercaptans and extracts them.
2RSH + 2NaOH => 2NaSR + 2H2O – eqn. 2
Where the RSH = the mercaptan
R = signifies the organic group. eg. Methyl, ethyl or propyl.
SH = the mercaptan
The second step is the regeneration step. The caustic solution leaving the extractor is heated and oxidized.
4NaSH + O2 + H2O => 2RSSR + 4NaOH – eqn. 3
The disulphates are decanted, the “lean” caustic is recirculated back into the system.
Feedstock entering the extractor must be free of H2S. It must be pre-washed, and the governing reaction is;
H2S + NaOH è NaSH + H2O
