Processes and apparatus for separating treated gasoline range hydrocarbons from spent alkali solution

Abstract

Processes and apparatus are provided for treating gasoline range hydrocarbons containing mercaptans to convert the mercaptans to organic disufides. The process involves contacting treated gasoline range hydrocarbons comprising organic disulfides with a coalescing material and separating refined gasoline range hydrocarbons and organic disulfides from spent alkali using a separation device. The apparatus comprises a treatment vessel suitable for housing a catalyst therein for producing treated gasoline range hydrocarbons comprising organic disulfides, as well as a separation device and coalescing material therein for separating gasoline range hydrocarbons and organic disulfides from spent alkali.

What is claimed is: 
     
         1 . A process for treating gasoline range hydrocarbons, the process comprising the steps of:
 providing a gasoline feed stream comprising gasoline range hydrocarbons and mercaptans;   adding alkali to the gasoline feed stream to form a feed mixture;   adding an oxygen-containing gas to the feed mixture;   contacting the feed mixture with a catalyst capable of converting mercaptans to organic disulfides to produce a treated gasoline stream comprising the organic disulfides and spent alkali;   separating the gasoline range hydrocarbons from the spent alkali using a separation device to produce a refined gasoline stream comprising the gasoline range hydrocarbons and the organic disulfides; and   contacting the treated gasoline stream with a coalescing material for encouraging the spent alkali to coalesce in an aqueous phase and separate from the gasoline range hydrocarbons in an organic phase which combines with the treated gasoline stream.   
     
     
         2 . The process of  claim 1 , wherein contacting the treated gasoline stream with a coalescing material is performed immediately before or immediately after separating the gasoline range hydrocarbons from the spent alkali using the separation device. 
     
     
         3 . The process of  claim 1 , wherein adding alkali comprises adding an aqueous mixture comprising from about 0.5 to about 5 percent by weight caustic, based on the total weight of the aqueous mixture. 
     
     
         4 . The process of  claim 3 , wherein adding alkali comprises choosing the caustic from sodium hydroxide, potassium hydroxide, and mixtures thereof. 
     
     
         5 . The process of  claim 1 , wherein providing a gasoline feed stream comprises providing gasoline range hydrocarbons and mercaptans, the gasoline range hydrocarbons comprising a mixture of C 5 -C 12  hydrocarbons having a boiling point range of from about 28 to about 221° C. (about 82 to about 430° F.). 
     
     
         6 . The process of  claim 1 , wherein contacting the treated gasoline stream with a coalescing material comprises contacting the treated gasoline stream with a coalescing material that comprises a mesh material, a nonwoven fiber material, a corrugated sheet material, or a combination thereof. 
     
     
         7 . The process of  claim 6 , wherein contacting comprises contacting the treated gasoline stream with the coalescing material being coated with hydrophilic substance. 
     
     
         8 . The process of  claim 1 , wherein contacting comprises contacting the treated gasoline stream with a coalescing material comprising a hydrophilic substance coated directly on at least a portion of the separation device. 
     
     
         9 . The process of  claim 1 , further comprising distilling the refined gasoline stream to produce a light naphtha stream and a heavy naphtha stream. 
     
     
         10 . The process of  claim 9 , further comprising subjecting the heavy naphtha stream to a hydroprocessing stage for removal of unwanted constituents. 
     
     
         11 . A process for treating gasoline range hydrocarbons, the process comprising the steps of:
 providing a gasoline feed stream comprising gasoline range hydrocarbons and mercaptans;   adding alkali to the gasoline feed stream to form a feed mixture;   adding an oxygen-containing gas to the feed mixture;   contacting the feed mixture with a catalyst capable of converting mercaptans to organic disulfides to produce a treated gasoline stream comprising the organic disulfides and spent alkali;   separating the gasoline range hydrocarbons from the spent alkali using a separation device to produce a refined gasoline stream comprising the gasoline range hydrocarbons and the organic disulfides;   contacting the treated gasoline stream with a coalescing material for encouraging the spent alkali to coalesce in an aqueous phase and separate from the gasoline range hydrocarbons in an organic phase which combines with the treated gasoline stream;   distilling the refined gasoline stream to produce a light naphtha stream and a heavy naphtha stream; and   subjecting the heavy naphtha stream to a hydroprocessing stage for removal of unwanted constituents.   
     
     
         12 . An apparatus for treating gasoline range hydrocarbons comprising mercaptans, the apparatus comprising:
 a treatment vessel comprising:
 an interior suitable for housing a catalyst situated therein, wherein said catalyst is capable of converting mercaptans to organic disulfides in the presence of alkali and molecular oxygen; 
 an inlet in fluid communication with the interior for allowing a gasoline feed stream comprising gasoline range hydrocarbons, mercaptans, alkali and an oxygen-containing gas to enter the interior and contact the catalyst and produce treated gasoline range hydrocarbons; 
 a separation device situated in a bottom portion of the treatment vessel and capable of separating refined gasoline comprising organic disulfides from spent alkali in the treated gasoline range hydrocarbons, the separation device having an outlet for allowing the treated gasoline to exit the interior; 
 coalescing material situated proximate the separation device and capable of enhancing separation of the refined gasoline comprising organic disulfides from the spent alkali; and 
 an outlet located at the bottom of the vessel for allowing the spent alkali to exit the interior. 
   
     
     
         13 . The apparatus of  claim 12 , wherein the coalescing material comprises a layer of mesh, nonwoven fiber, or combinations thereof, wrapped around and overlaying at least a portion of the separating device. 
     
     
         14 . The apparatus of  claim 12 , wherein separation device comprises:
 a manifold conduit comprising a wall having a plurality of openings and forming a central interior flow path in fluid communication with each of the plurality of openings;   a plurality of lateral conduits, each being connected to the manifold conduit at a corresponding opening in the wall thereof, each having a cylindrical wall forming an interior flow path that is in fluid communication with the central interior flow path via the corresponding opening in the wall of the manifold conduit, and each having plurality of slots in the cylindrical wall thereof, wherein each of the plurality of slots is in fluid communication with the interior flow path of the lateral conduit and is sized and shaped to allow passage of refined gasoline comprising the gasoline range hydrocarbons and organic disulfides therethrough to the interior flow path of the lateral conduit, and to prevent passage therethrough of catalyst and minimize passage therethrough of spent alkali.   
     
     
         15 . The apparatus of  claim 14 , wherein the interior flow path of the manifold conduit is in fluid communication with the outlet of the separation device for allowing the refined gasoline comprising the gasoline range hydrocarbons and the organic disulfides to exit the separation device and treatment vessel. 
     
     
         16 . The apparatus of  claim 14 , wherein the coalescing material comprises a layer of mesh, nonwoven fiber, or combinations thereof, wrapped around and overlaying one or more of the plurality of lateral conduits. 
     
     
         17 . The apparatus of  claim 16 , wherein the coalescing material is coated with a hydrophilic substance. 
     
     
         18 . The apparatus of  claim 16 , wherein the coalescing material has a thickness of from about 1.27 centimeters (cm) (0.5 inch (in)) to about 15.2 cm (6 inches). 
     
     
         19 . The apparatus of  claim 12 , further comprising an inlet conduit in fluid communication with the inlet of the treatment vessel and capable of delivering a gasoline feed stream comprising the gasoline range hydrocarbons and mercaptans to the treatment vessel, wherein the inlet conduit is in fluid communication with an alkali supply line for delivering and adding alkali to the gasoline feed stream prior to delivering the gasoline feed stream to the treatment vessel. 
     
     
         20 . The apparatus of  claim 12 , further comprising a gravity phase separation vessel capable of receiving and containing the spent alkali; wherein the gravity phase separation vessel comprises a bottom outlet for allowing spent alkali to exit the gravity phase separation vessel and a top outlet for providing gasoline range hydrocarbons to a pressure equalizing conduit.