Technology

The term Merox™ is an abbreviation of ” Mercaptan Oxidation”. It is a specialized catalytic chemical process created by UOP (Universal Oil Products) applied for the chemical treatment of petroleum distillates to remove mercaptans. In the Merox process, the mercaptans (Sulfur compounds) are removed or converted to a less objectionable form. The process is based on a special UOP catalyst to accelerate the oxidation of mercaptans to disulfides at optimum operating conditions in an alkaline environment.

LPG Merox Process Description

• The LPG feedstock after treating with Amine in the Amine Absorption Tower enters the prewash vessel and flows upward through a caustic batch, eliminating any undesirable remaining H₂S from the feed stream.
• The H₂S free feedstock enters the mercaptan extractor and goes upward through the contact trays, where the mercaptans are extracted from LPG by countercurrent contact with the downflowing caustic.
• After leaving the tower, the sweetened LPG passes through three vessels; any entrained caustic is removed in a caustic settler vessel, any residual caustic is further removed in a water wash vessel, and any water is removed in a vessel with a bed of rock salt. The dry-sweetened LPG product leaves the unit for storage. In some cases, Sodium traces present in LPG are removed by a sand filter.
• The mercaptan-rich caustic solution from the extractor bottom passes to the regeneration section. The rich stream is heated and contacted with the compressed air before entering the Oxidizer. In the Oxidizer Mercaptans are oxidized and converted to disulfide oils.
• From the Oxidizer the caustic-disulfide mixture and spent air proceeds to the Disulfide Separator. It is then allowed to produce an upper layer of disulfide and a lower layer of “lean” Merox caustic in the separator vessel. The vertical column of the separator, used to exhaust spent air, has a Rasching rings section to stop any disulfides from being drawn into the vented air. The disulfides are removed from the separator and sent to a hydrotreater unit or fuel storage. After regeneration, the lean Merox caustic is pumped back up to the top of the extractor for further use. The spent air is sent to the Incinerator for safe disposal in the Sulfur Recovery Unit. 

Source: The Petrosolutions > LPG Merox Process in the Petroleum Refinery