本科学位论文-油气储运专业设计文献翻译（附原文）原油的加工工艺.doc

Petroleum Refining Processes Desulphurisation Sulphur occurs in crude oils combined in a variety of ways, from the simplest compound H2S to complex ring structures. H2S is produced during distillation of the crude oil by decomposition of higher boiling sulphur compounds and appears in the LPG from which it must be removed because of its poisonous and corrosive nature. This is done by counter current washing with an amine (e.g.diethanolamine), the H2S being removed for sulphur recovery by heating the amine solution in a separate vessel thus regenerating the amine for recycle to the washing stage . Mercaptans can be considered derivatives of H2S, in which one hydrogen atom is replace by a carbon /hydrogen group, and share some of its unpleasant properties of bad smell and corrosivity . Those mercaptans boiling below about 80℃ are readily dissolved in alkaline solutions but the solubility decreases rapidly above that temperature .For LPG and light gasolines therefore the mercaptans can be removed by counter current washing with caustic soda solution. The UOP Merox process uses caustic soda to extract the mercaptans which are then oxidised with air to disulphides and the caustic soda regenerated for further use. The oxidation step is assisted by a metal complex catalyst dissolved in the caustic soda. The process can be represented as follow: 4C2H5SH+4NaOH= 4C2H5SNa+2H2O +2H2O +O2 2C2H5S桽C2H5+4NaOH The disulphides are not soluble in caustic soda and form an oil layer which can be removed. Mercaptans in fraction boiling between80℃ and 250℃ cannot be oxidised to disulphides in the Merox solution with air. The disulphides,which are non-corrosive and have little smell, remain dissolved in the oil so that no actual desulphurisation has been achived but the products have been “sweetened”. Another process for the oxidation of mercaptans uses copper chloride as a catalyst. Both processes can be used in the production of aviation jet fuels.