Method for removing phospholipids from vegetable oil miscella, method for conditioning a polymeric microfiltration membrane, and membrane

Abstract

A method for removing phospholipids from vegetable oil miscella is provided. The method includes steps of feeding vegetable oil miscella to a conditioned polymeric microfiltration membrane, and recovering a permeate stream having a decreased weight percent of phospholipids compared with the weight percent of phospholipids provided in the miscella. The polymeric microfiltration membrane can be conditioned for the selective separation of phospholipids in the miscella. A method for conditioning a membrane for selective separation of phospholipids from vegetable oil miscella, and the resulting membrane, are provided. The membrane which can be conditioned can be characterized as having an average pore size of between about 0.1μ and about 2μ.

We claim:  
     
         1 . A method for removing phospholipids from vegetable oil miscella, the method comprising steps of: 
 (a) feeding vegetable oil miscella to a membrane for recovery of a permeate stream and a retentate stream, wherein said miscella comprises extraction solvent and crude vegetable oil containing phospholipids, and said membrane comprises a polymeric microfiltration membrane conditioned for selective separation of phospholipids from said miscella to provide a permeate stream having decreased weight percent of phospholipids compared with the weight percent of phospholipids provided in said miscella;    (b) recovering said permeate stream having decreased weight percent of phospholipids compared with the weight percent of phospholipids provided in said miscella.    
     
     
         2 . A method for removing phospholipids from vegetable oil miscella according to    claim 1   , wherein the microfiltration membrane comprises a membrane provided on a backing, the membrane characterized as having an average pore size in the range of about 0.1μ to about 2μ.  
     
     
         3 . A method for removing phospholipids from vegetable oil miscella according to    claim 2   , wherein the polymeric microfiltration membrane is conditioned by a three step conditioning sequence comprising: 
 (i) treating the microfilter with an intermediate solvent; and    (ii) treating the microfilter with a mixture of intermediate solvent and extraction solvent; and    (iii) treating the microfilter with an extraction solvent.    
     
     
         4 . A method for removing phospholipids from vegetable oil miscella according to    claim 1   , wherein said miscella comprises between about 45 and about 90 weight percent extraction solvent.  
     
     
         5 . A method for removing phospholipids from vegetable oil miscella according to    claim 1   , wherein the extraction solvent comprises hexane.  
     
     
         6 . A method for removing phospholipids from vegetable oil miscella according to    claim 1   , wherein said permeate stream comprises less than about 0.6 weight percent phospholipids.  
     
     
         7 . A method for removing phospholipids from vegetable oil miscella according to    claim 1   , wherein said permeate stream comprises less than about 0.15 weight percent phospholipids.  
     
     
         8 . A method for removing phospholipids from vegetable oil miscella according to    claim 1   , wherein said permeate stream comprises less than 0.015 weight percent phospholipids.  
     
     
         9 . A method for removing phospholipids from vegetable oil miscella according to    claim 1   , wherein the microfiltration membrane comprises polyacrylonitrile, polysulfone, polyamide, or polyimide.  
     
     
         10 . A method for conditioning a polymeric microfiltration membrane for selective separation of phospholipids from vegetable oil miscella, the method comprising steps of: 
 (a) providing a polymeric microfiltration membrane characterized as having an average pore size in the range of about 0.1μ to about 2μ;    (b) treating the membrane with an intermediate solvent; and    (c) treating the membrane with an extraction solvent.    
     
     
         11 . A method for conditioning a polymeric microfiltration membrane according to    claim 10   , wherein the membrane comprises a polyacrylonitrile membrane.  
     
     
         12 . A method for conditioning a polymeric microfiltration membrane according to    claim 10   , wherein the membrane comprises a polysulfone membrane.  
     
     
         13 . A method for conditioning a polymeric microfiltration membrane according to    claim 10   , wherein said step of treating the membrane with an intermediate solvent comprises soaking in said intermediate solvent for at least about one-half hour.  
     
     
         14 . A method for conditioning a polymeric microfiltration membrane according to    claim 10   , wherein said step of treating the membrane with an extraction solvent comprises soaking in said extraction solvent for at least about one-half hour.  
     
     
         15 . A method for conditioning a polymeric microfiltration membrane according to    claim 10   , further comprising a step of treating the membrane with a mixture of intermediate solvent and extraction solvent.  
     
     
         16 . A method for conditioning a polymeric microfiltration membrane according to    claim 10   , wherein the intermediate solvent comprises ethanol, propanol, or mixture of ethanol and propanol.  
     
     
         17 . A method for conditioning a polymeric microfiltration membrane according to    claim 10   , wherein the extraction solvent comprises hexane.  
     
     
         18 . A membrane prepared by the method of    claim 10   .  
     
     
         19 . A membrane for selective separation of phospholipids from vegetable oil miscella, comprising: 
 (a) a conditioned polymeric microfiltration membrane which, when subjected to a soybean oil miscella containing 25 percent by weight crude soybean oil and 75 percent by weight hexane and a phosphorous level of about 5,000 ppm at a transmembrane pressure of 150 psi, will provide a steady state permeate at greater than about 65 l/hr m 2  having a phosphorous level of less than about 50 ppm.    
     
     
         20 . A membrane according to    claim 19   , wherein the membrane comprises polyacrylonitrile.  
     
     
         21 . A membrane according to    claim 19   , wherein the membrane comprises polysulfone.  
     
     
         22 . A membrane according to    claim 19   , wherein the steady state permeate is provided at greater than about 80 l/hr m 2 .  
     
     
         23 . A membrane according to    claim 19   , wherein the steady state permeate is provided with a phosphorous level of less than about 25 ppm.  
     
     
         24 . A method for cleaning a conditioned polymeric microfiltration membrane, the method comprising steps of: 
 (a) providing a conditioned microfiltration membrane which has been used for separation of phospholipids from vegetable oil miscella; and    (b) flushing the membrane with extraction solvent for a time sufficient to remove phospholipids from said membrane.