Mercaptan removal from petroleum streams (law950)

Abstract

This invention relates to reducing the amount of thiols (mercaptans) in petroleum streams, specifically, mercaptans above the five carbon molecular weight range.

What is claimed is:  
     
         1 . A method for removal of mercaptans from petroleum streams comprising the steps of: 
 (a) extracting said petroleum stream, in the substantial absence of oxygen, with an aqueous medium comprising an aqueous base and a catalytically effective amount of a phase transfer catalyst or an aqueous solution of a catalytically effective amount of a basic phase transfer catalyst to remove said mercaptans from said petroleum stream;    (b) Separating and recovering an aqueous stream containing mercaptide anions and a petroleum stream having a reduced amount of mercaptans, and wherein when said phase transfer catalyst is a quaternary ammonium hydroxide, said quaternary ammonium cation has the formula:                          where q=1/w+1/x+1/y+1/z and wherein q≧1.0, and wherein Cw, Cx, Cy, and Cz represent alkyl radicals with carbon chain lengths of w, x, y and z carbon atoms respectively.    
     
     
         2 . The process of  claim 1  further comprising the step of processing said petroleum feedstream.  
     
     
         3 . The process of  claim 1  further comprising the steps of: 
 (c) subjecting said aqueous stream to oxidation to convert mercaptide anions contained therein to disulfides;  
 d) separating said disulfides and recovering an aqueous stream having disulfides removed therefrom;  
 (e) recycling said aqueous stream to said step (a) wherein said aqueous stream contains said base and said phase transfer catalyst or said basic phase transfer catalyst of said step (a).  
 
     
     
         4 . The process of  claim 1  wherein said phase transfer catalyst is selected from the group consisting essentially of onium salts, crown ethers, open chain polyethers, and mixtures thereof.  
     
     
         5 . The process of  claim 4  wherein said onium salts are selected from the group consisting of quaternary ammonium hydroxides, quaternary ammonium halides, quaternary ammonium hydrogen sulfates and mixtures thereof.  
     
     
         6 . The process of  claim 4  wherein said phase transfer catalyst is selected from polyethylene glycol, tetrabutylammonium hydroxide, cetyltrimethylammonium bromide, and tetrabutylphosphonium, tributylmethyl ammonium, methyltrioctyl ammonium and methyltricapryl ammonium salts, and mixtures thereof.  
     
     
         7 . The process of  claim 1  wherein said base is selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, and mixtures thereof.  
     
     
         8 . The process of  claim 1  wherein said PTC is supported or unsupported.  
     
     
         9 . The process of  claim 8 , wherein when said PTC is a supported PTC, said support is selected from the group consisting essentially of molecular sieves, polymers, carbonaceous supports, inorganic oxides and mixtures thereof.  
     
     
         10 . The process of  claim 9  wherein said inorganic oxides are selected from the group consisting essentially of silicas, aluminas, and mixtures thereof.  
     
     
         11 . The process of  claim 8  wherein said support is regenerated by introduction of oxygen (air) and an organic extractant into the support.  
     
     
         12 . The process of  claim 1  wherein said PTC is added in amounts of about 0.01 to about 10 wt. % of said aqueous medium.  
     
     
         13 . The process of  claim 12  wherein said base is added in amounts of up to about 50 wt % of said aqueous stream.  
     
     
         14 . The process of  claim 11  wherein said process is a swing bed process.  
     
     
         15 . The process of  claim 1  wherein prior to said step (a) said petroleum stream has been treated to remove non-mercaptan sulfur species.  
     
     
         16 . The process of  claim 1  wherein said mercaptans are ≧C 5   +  molecular weight mercaptans.  
     
     
         17 . A method for sweetening mercaptan containing petroleum streams comprising the steps of: 
 (a) mixing said petroleum stream, in the presence of a sufficient amount of oxygen to oxidize the mercaptans contained in said petroleum stream to disulfides, with a medium consisting essentially of an aqueous base and a phase transfer catalyst (PTC) or an aqueous solution of a basic phase transfer catalyst to reduce the amount of said mercaptans from said petroleum stream    (b) Separating and recovering an aqueous stream and a petroleum stream having mercaptans converted to disulfides therein.    
     
     
         18 . The process of  claim 1  wherein at least about 70% mercaptan removal is obtained.  
     
     
         19 . The process of  claim 1  wherein said process is run in the absence of any additional mercaptan oxidizing catalyst.  
     
     
         20 . The process of  claim 1  wherein said aqueous medium is used in an amount of from about 5 to about 200% by volume of said petroleum stream.