High efficiency in liquid-liquid extraction operations, such as extracting mercaptans from hydrocarbons with caustic, is obtained over a wide range of flow rates through a single extraction column by the provision of an intermediate product drawoff means located between a downstream section of extraction trays having greatest efficiency at low throughputs and an upstream section of trays having peak efficiency at high throughputs. A second product stream is removed after passing through the low flow rate trays and is blended with the stream from the intermediate drawoff means.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of my copending application Ser. No. 627,989 which was filed Nov. 3, 1975 now U.S. Pat. No. 4,039,389.
A method for treating sulfur-containing lubricating oil, by contacting the oil with iodine in the presence of an aqueous solution of alkali and thereafter separating the treated oil from the contacting solution. A lubricating oil having increased resistance to oxidation produced by this method.
A process is disclosed for treating hydrocarbon streams for the purpose of removing mercaptans and also converting the remaining mercaptans to disulfides which remain in the hydrocarbon stream being treated. The hydrocarbons rise through a contacting column countercurrently to a descending stream of an aqueous alkaline solution. A limited amount of an oxygen-containing gas is passed into an intermediate point in the column thereby dividing it into an upper sweetening section and a lower extraction section. The flow rate of the oxygen-containing stream is preferably low enough that any gas not consumed in the catalytic oxidation of mercaptans becomes dissolved in the hydrocarbon product stream, and preferably remains dissolved at atmospheric pressure.
A caustic wash process to remove mercaptans from a mixture of hydrocarbons, an improvement comprising washing the regenerated caustic with a fraction of said hydrocarbon to remove residual disulfides to improve the overall removal of sulfur from the hydrocarbon feed stream.
A process is disclosed for treating hydrocarbon streams such as naphtha by the oxidation of mercaptans into disulfide compounds which remain in the hydrocarbon stream. The conversion is effected during passage of the hydrocarbon and an aqueous stream downward through a cylindrical mass of liquid-liquid contact material. The liquids then flow through a cylindrical screen into an annular separation zone which surrounds a lower part of the contact material. After decantation in the separation zone, the aqueous material, which preferably contains the oxidation catalyst, is recycled.
A process is directed to the removal of impurities such as sulfur compounds, oxygenates, and/or olefins from a light paraffin hydrocarbon feedstock such as a C.sub.4 -C.sub.6 fraction, which may be used subsequently in an isomerization process in an integrated complex for the production of ethers such as MTBE and TAME. The hydrocarbon feedstream is passed to a removal zone wherein the hydrocarbon feedstream is contacted with a selective solvent for the removal of the impurities comprising at least one of sulfur compounds, oxygenates and olefins to provide a rich solvent stream and a treated hydrocarbon stream. The rich solvent comprising the trace impurities is contacted with a stripping medium stream to regenerate the selective solvent in a stripping zone. The removal zone may be a liquid-liquid extraction zone or a gas absorption zone. The selective solvent comprises a water miscible organic liquid having a low molecular weight preferably less than about 400 and more preferably having a molecular weight of less than about 200. The process is particularly useful in removing impurities such as sulfur, oxygenates and/or olefins which are harmful to the isomerization catalyst. The process replaces separate olefins, oxygenate, and sulfur removal processes resulting in simplified processing schemes.
