Mercaptan extraction

The principle of using NaOH for demercaptanization is that the mercaptans in the oil first react with NaOH to generate sodium mercaptide, which is decomposed into thiol anions. Molecular oxygen and the catalyst (sulfonated titanium cobalt cyanocobalt) form an unstable active complex, which completes single electron transfer with the thiol anions to generate thiol radicals. The two thiol radicals combine to form a relatively stable disulfide RSSR to achieve the purpose of desulfurization. It should be pointed out that in the early fixed-bed desulfurization process, the sulfur was not completely removed from the oil, but only existed in another form, and the effect only achieved the purpose of deodorization. As for UOP's desulfurization extraction, I don't know much about it. If the disulfide is extracted during the process, the purpose of desulfurization can also be achieved. Regardless of the process, sulfonated titanium cobalt cyanide plays the role of a catalyst, through which the formation of active complexes is achieved.

This step does not require a catalyst. This reaction is used to demercaptanize liquefied gas. However, this catalyst is needed in the gasoline deodorization (catalytic oxidation process, which also requires air blowing to convert the mercaptans in the gasoline into disulfides) or the alkali regeneration process (sodium mercaptide undergoes catalytic oxidation under the action of the catalyst to generate sodium hydroxide and disulfide). The role of catalysts has been mentioned above. For detailed information, please refer to books on "Petroleum Non-Hydrocarbon Chemistry".