Membrane process for separating sulfur compounds from FCC light naphtha

Abstract

A process for the separation of sulfur compounds from a hydrocarbon mixture using a membrane is provided. Preferred hydrocarbon mixtures are oil refining fractions such as light cracked naphtha. Membranes are composed of either ionic or non-ionic materials and preferentially permeate sulfur compounds over other hydrocarbons. A single or multi-stage membrane system separates the hydrocarbon mixture into a sulfur-rich fraction and a sulfur-lean fraction. The sulfur-lean fraction may be used in fuel mixtures and the sulfur-rich fraction may be further treated for sulfur reduction.

What is claimed is:  
     
         1 . A process for separating sulfur compounds from a hydrocarbon mixture containing at least one sulfur compound and hydrocarbons comprising the steps of: 
 (a) contacting said hydrocarbon mixture with a first compartment of a membrane module, said membrane module further comprising a second compartment and a hydrophilic membrane separating said first compartment and said second compartment;    (b) selectively permeating said sulfur compounds of said hydrocarbon mixture through said membrane such that a sulfur-rich fraction collects in said second compartment and a sulfur-lean fraction is retained in said first compartment; and    (c) retrieving said sulfur-rich fraction from said second compartment and said sulfur-lean fraction from said first compartment.    
     
     
         2 . The process of  claim 1  further comprising the steps of: 
 (d) contacting said sulfur-rich fraction of step (c) with a first compartment of a further membrane module, said further membrane module comprising a second compartment and a hydrophilic membrane separating said first compartment and said second compartment;  
 (e) selectively permeating sulfur compounds of said sulfur-rich fraction of step (d) through said membrane such that a further sulfur-rich fraction accumulates in said second compartment and a further sulfur-lean fraction is retained in said first compartment; and  
 (f) retrieving said further sulfur-rich fraction and said further sulfur-lean fraction;  
 (g) repeating steps (d), (e) and (f) using said sulfur-rich fraction until a final sulfur-rich fraction of desired sulfur content is obtained; and  
 (h) retrieving said final sulfur-lean fraction.  
 
     
     
         3 . The process of  claim 1  wherein said hydrocarbon mixture is obtained from an oil refining process.  
     
     
         4 . The process of  claim 1  wherein said hydrocarbon mixture is a light cracked naphtha.  
     
     
         5 . The process of  claim 1  wherein said sulfur compound is thiophene or a derivative of thiophene.  
     
     
         6 . The process of  claim 1  wherein said hydrophilic membrane is an ionic membrane.  
     
     
         7 . The process of  claim 6  wherein said membrane is selected from the polymers of perfluorosulfonic acid and derivatives thereof.  
     
     
         8 . The process of  claim 1  wherein said hydrophilic membrane is a water-soluble membrane.  
     
     
         9 . The process of  claim 1  wherein said hydrophilic membrane is a non-ionic membrane.  
     
     
         10 . The process of  claim 10  wherein said membrane comprises polyvinylpyrrolidone.  
     
     
         11 . The process of  claim 10  wherein said membrane comprises cellulose triacetate.  
     
     
         12 . The process of  claim 1  which is performed under pervaporation conditions.  
     
     
         13 . The process of  claim 1  which is performed under perstraction conditions.  
     
     
         14 . The process of  claim 2  wherein said membrane of said further membrane module is an ionic membrane.  
     
     
         15 . The process of  claim 14  wherein said membrane is selected from the polymers of perfluorosulfonic acid and derivatives thereof.  
     
     
         16 . The process of  claim 2  wherein said hydrophilic membrane is a non-ionic membrane.  
     
     
         17 . The process of  claim 2  wherein said hydrophilic membrane is a water-soluble membrane.  
     
     
         18 . The process of  claim 16  wherein said membrane comprises polyvinylpyrrolidone.  
     
     
         19 . The process of  claim 16  wherein said membrane comprises cellulose triacetate.