Processes for the esterification of free fatty acids and the production of biodiesel

Abstract

The effluent from an acid esterification of free fatty acid with alkanol to produce alkyl ester of fatty acid is contacted with glycerin to remove water and alkanol. The alkanol separated with the glycerin can be recycled to the acid esterification by contacting the glycerin with fatty acid-containing feed being passed to the acid esterification.

1 . A process for the esterification of feed containing free fatty acid comprising:
 a. contacting the feed with a stoichiometric excess of alkanol under acidic esterification conditions including the presence of acid catalyst at elevated temperature, for a time sufficient to provide an esterification effluent comprising alkyl ester of the free fatty acid, water and unreacted alkanol;   b. contacting at least a portion of the esterification effluent with sufficient glycerin to form a glycerin-containing phase and an oil phase comprising alkyl ester, said contacting being for a time and under conditions sufficient that said oil phase has a lower water and a lower alkanol concentration than the esterification effluent and said glycerin phase contains water and alkanol; and   c. phase separating the oil phase and the glycerin phase.   
     
     
         2 . The process of  claim 1  wherein the feed comprises glyceride containing free fatty acid. 
     
     
         3 . The process of  claim 1  wherein the glycerin phase contains at least about 60 percent of the water contained in the esterification effluent. 
     
     
         4 . The process of  claim 3  wherein the glycerin phase contains at least about 30 mass percent of the alkanol contained in the esterification effluent. 
     
     
         5 . The process of  claim 1  wherein the alkanol comprises methanol. 
     
     
         6 . The process of  claim 1  wherein the catalyst comprises sulfuric acid. 
     
     
         7 . The process of  claim 1  wherein at least a portion of the glycerin phase of step (c) is contacted with the feed prior to step (a) under conditions sufficient to provide a feed phase containing an increased concentration of alkanol and a spent glycerin phase having a decreased concentration of alkanol; phase separating the feed phase and the spent glycerin phase; and providing the feed phase to step (a). 
     
     
         8 . A process for the esterification of feed containing free fatty acid comprising:
 a. contacting the feed with a glycerin solution containing alkanol under conditions sufficient to provide a feed phase containing an increased concentration of alkanol and a spent glycerin phase having a decreased concentration of alkanol;   b. phase separating the feed phase and the spent glycerin phase; and   c. contacting the feed phase with a stoichiometric excess of alkanol under acidic esterification conditions including the presence of acid catalyst at elevated temperature, for a time sufficient to provide an esterification effluent comprising alkyl ester of the free fatty acid, water and unreacted alkanol.   
     
     
         9 . The process of  claim 8  wherein alkyl ester is added to the feed prior to step (a) to increase the solubility of alkanol in the feed. 
     
     
         10 . The process of  claim 8  wherein the alkanol comprises methanol. 
     
     
         11 . A process for the esterification of feed containing free fatty acid comprising:
 a. contacting the feed with a stoichiometric excess of alkanol under acidic esterification conditions including the presence of glycerin-soluble, acid catalyst at elevated temperature, for a time sufficient to provide an esterification effluent comprising alkyl ester of the free fatty acid, water, acid catalyst and unreacted alkanol;   b. contacting at least a portion of the esterification effluent with glycerin whereby a glycerin-containing phase and an oil phase comprising alkyl ester are formed, said contacting being for a time and under conditions sufficient that the oil phase has a lower acid catalyst concentration than the esterification effluent and a lower water concentration than the esterification effluent and said glycerin phase contains acid catalyst, water and alkanol;   c. phase separating the oil phase and the glycerin phase;   d. contacting the glycerin phase with soaps of free fatty acids to generate free fatty acids;   e. separating free fatty acids from said glycerin phase; and   f. recycling the free fatty acids to step (a).   
     
     
         12 . A process for the esterification of feed containing free fatty acid comprising:
 a. contacting the feed with a stoichiometric excess of alkanol under acidic esterification conditions including the presence of an oil-soluble, acid catalyst at elevated temperature, for a time sufficient to provide an esterification effluent comprising alkyl ester of the free fatty acid, acid catalyst, water and unreacted alkanol;   b. providing sufficient alkanol in said esterification effluent to enable to form an alkanol phase containing alkanol, water and oil-soluble acid catalyst and an oil phase containing alkyl ester and unreacted free fatty acid;   c. phase separating the alkanol phase and the oil phase; and   d. passing at least a portion of the alkanol phase to step (a).   
     
     
         13 . The process of  claim 12  wherein the oil-soluble, acid catalyst comprises an organosulfonic acid. 
     
     
         14 . The process of  claim 12  wherein water is separated from at least a portion of the alkanol phase of step (c) to provide a higher boiling catalyst fraction. 
     
     
         15 . The process of  claim 14  wherein at least one of free fatty acid, glyceride and glycerin is provided during distillation in an amount sufficient to maintain the oil-soluble, acid catalyst in a liquid phase. 
     
     
         16 . A process for the esterification of feed containing at least about 5 mass percent free fatty acid comprising:
 a. contacting the feed with a stoichiometric excess of alkanol under acidic esterification conditions including the presence of acid catalyst at elevated temperature below about 120° C., for a time sufficient to convert between about 50 and 95 mass percent of the free fatty acids to alkyl esters and provide an esterification effluent comprising alkyl ester of the free fatty acid, free fatty acid, water and unreacted alkanol;   b. contacting at least a portion of the esterification effluent with sufficient basic glycerin to saponify free fatty acid to form soaps of said free fatty acid and provide an oil phase comprising alkyl ester and a glycerin phase comprising glycerin and soaps; and   c. phase separating the oil phase and glycerin phase.   
     
     
         17 . The process of  claim 16  wherein the acidic esterification conditions comprise a temperature below about 120° C. 
     
     
         18 . A process for esterification of feed containing free fatty acid comprising:
 a. contacting the feed with a stoichiometric excess of alkanol, under acidic esterification conditions including the presence of acid catalyst that is soluble in alkanol and substantially insoluble in alkyl ester of fatty acid to provide an esterification effluent comprising an alkanol and acid catalyst-containing phase and a first oil phase containing alkyl ester of the free fatty acid, water and unreacted alkanol;   b. phase separating the alkanol and acid catalyst-containing phase and the first oil phase;   c. contacting the first oil phase with glycerin to provide a second oil phase having a reduced concentration of water and alkanol and a glycerin-containing phase containing water and alkanol;   d. admixing at least a portion of the glycerin-containing phase with the alkanol and catalyst-containing phase to provide an admixture; and   e. recovering alkanol from the admixture by vapor fractionation.   
     
     
         19 . The process of  claim 18  wherein the alkanol comprises methanol. 
     
     
         20 . The process of  claim 19  wherein the catalyst comprises sulfuric acid.