|
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.〔(Treating Technology Solutions )〕 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 (H2S) 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. ==Types of Merox process units== UOP has developed many versions of the Merox process for various applications: * Conventional Merox for extraction of mercaptans from LPG, propane, butanes or light naphthas.〔(Merox Process for Mercaptan Extraction ) 〕 * Conventional Merox for sweetening jet fuels and kerosenes.〔(Merox Process for Kerosene/Jet Fuel Sweetening ) 〕 * Merox for extraction of mercaptans from refinery and natural gases.〔(Merox Process for Gas Extraction ) 〕 * Minalk Merox for sweetening of naphthas.〔(Minalk Process for Fixed-Bed Naphtha Sweetening ) 〕 This process continuously injects just a few ppm of caustic into the feed naphtha. * Caustic-free Merox for sweetening jet fuels and kerosenes.〔(Caustic-free Merox Process for Kerosene/Jet Fuel Sweetening ) 〕 This process injects small amounts of ammonia and water (rather than caustic) into the feed naphtha to provide the required alkalinity. *Caustic-free Merox for sweetening of naphthas.〔(Caustic-Free Merox Process for Fixed-Bed Naphtha Sweetening ) 〕 This process also injects small amounts of ammonia and water (rather than caustic) into the feed naphtha to provide the required alkalinity. In all of the above Merox versions, the overall oxidation reaction that takes place in converting mercaptans to disulfides is: :4 RSH + O2 → 2RSSR + 2H2O The most common mercaptans removed are: * Methanethiol - CH3SH () * Ethanethiol - C2H5SH (mercaptan ) * 1-Propanethiol - C3H7SH (mercaptan ) * 2-Propanethiol - CH3CH(SH)CH3 (mercaptan ) * Butanethiol - C4H9SH (mercaptan ) * ''tert''-Butyl mercaptan - C(CH3)3SH (mercaptan ) * Pentanethiol - C5H11SH (mercaptan ) In some of the above Merox process versions, the catalyst is a liquid. In others, the catalyst is in the form of impregnated charcoal granules. Process flow diagrams and descriptions of the two conventional versions of the Merox process are presented in the following sections. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「merox」の詳細全文を読む スポンサード リンク
|