Electrochemical process for conversion of biodiesel to aviation fuels

Abstract

Methods for the conversion of a biofuel such as biodiesel into an alkane composition such as an aviation fuel, kerosine, or liquified petroleum gas product involve a series of electrochemical reactions. The reactions include oxidation of methanol to carbon dioxide, reduction of fatty acid esters, and cleavage of fatty acid chains at C═C double bonds. The methods are carried out by systems of two or more electrochemical reactors.

1 . A system for the chemical conversion of a biodiesel to an alkane composition, the system comprising:
 a first electrochemical reactor that reduces excess MeOH in a biodiesel source material to yield a first composition comprising methyl esters of aliphatic carboxylic acids;   a second electrochemical reactor that fragments the methyl esters of aliphatic carboxylic acids of said first composition by carbon-carbon double bond cleavage to yield a second composition comprising short chain methyl esters of aliphatic carboxylic acids; and   a third electrochemical reactor that hydrogenates the methyl esters of said second composition to yield a third composition comprising alkanes.   
     
     
         2 . A system for the chemical conversion of a biodiesel to an alkane composition, the system comprising:
 a first electrochemical reactor that fragments aliphatic chains of a biodiesel source material by carbon-carbon double bond cleavage to yield a first composition comprising short chain methyl esters of aliphatic carboxylic acids; and   a second electrochemical reactor that performs a Kolbe reaction, whereby the aliphatic carboxylic acids of said first composition are decarboxylated to yield a second composition comprising alkanes.   
     
     
         3 . A system for the chemical conversion of a biodiesel to an alkane composition, the system comprising:
 a first electrochemical reactor that fragments aliphatic chains of a biodiesel source material by carbon-carbon double bond cleavage to yield a first composition comprising short chain methyl esters of aliphatic carboxylic acids; and   a second electrochemical reactor that hydrogenates the methyl esters of said first composition to yield a second composition comprising alkanes.   
     
     
         4 . The system of any one of  claims 1 - 3 , wherein the carbon-carbon double bond fragmentation process is performed with the aid of a Cu 2+ /Cu +  redox couple. 
     
     
         5 . The system of any one of  claims 1 - 3 , wherein the electrochemical reactor that performs the carbon-carbon double bond fragmentation process comprises a cation exchange membrane. 
     
     
         6 . The system of any one of  claim 1  or  claim 3 , wherein the electrochemical reactor that performs the hydrogenation process comprises a solid polymer electrolyte. 
     
     
         7 . The system of  claim 1  or  claim 3 , wherein the hydrogenation process is performed in two sequential reactions by two solid polymer electrolyte reactors working in sequence, the first reaction converting esters or aldehydes to primary alcohols and the second reaction converting the primary alcohols to alkanes. 
     
     
         8 . The system of  claim 1  or  claim 3 , wherein the electrochemical reactor that performs the hydrogenation process comprises a cation exchange membrane. 
     
     
         9 . A method for the chemical conversion of a biodiesel to an alkane composition, the method comprising the steps of:
 providing a crude biodiesel composition, the biodiesel composition comprising fatty acid esters and methanol;   reducing the amount of methanol in the biodiesel composition by electrochemical oxidation of methanol to carbon dioxide in a first electrochemical reactor;   fragmenting fatty acid chains of the biodiesel composition in a second electrochemical reactor that cleaves the fatty acid chains at carbon-carbon double bonds to yield short chain fatty acids and aldehydes; and   hydrogenating the short chain fatty acids and aldehydes in a third electrochemical reactor to yield a composition comprising alkanes.   
     
     
         10 . A method for the chemical conversion of a biodiesel to an alkane composition, the method comprising the steps of:
 providing a crude biodiesel composition, the biodiesel composition comprising fatty acid esters and methanol;   fragmenting fatty acid chains in the biodiesel composition in a first electrochemical reactor that cleaves the fatty acid chains at carbon-carbon double bonds to yield short chain fatty acids and aldehydes;   oxidizing the short chain aldehydes to short chain fatty acids; and   performing a Kolbe reaction in a second electrochemical reactor, whereby the short chain fatty acids are decarboxylated to form alkanes.   
     
     
         11 . A method for the chemical conversion of a biodiesel to an alkane composition, the method comprising the steps of:
 providing a crude biodiesel composition, the biodiesel composition comprising fatty acid esters and methanol;   fragmenting fatty acid chains in the biodiesel composition in a first electrochemical reactor that cleaves the fatty acid chains at carbon-carbon double bonds to yield short chain fatty acids and aldehydes; and   hydrogenating the short chain fatty acids and aldehydes in a second electrochemical reactor to form alkanes.   
     
     
         12 . The method of  claim 11 , wherein the step of hydrogenating comprises first the step of hydrogenating fatty acids to alcohols and subsequently the step of hydrogenating the alcohols to alkanes. 
     
     
         13 . The method of any one of  claims 9 - 12 , wherein the biodiesel source material comprises aliphatic chains of about 16 to about 22 carbon atoms in length. 
     
     
         14 . The method of any one of  claims 9 - 12 , wherein the final alkane composition comprises aliphatic chains of about 8 to about 11 carbon atoms in length. 
     
     
         15 . The method of any one of  claims 10 - 12 , further comprising the step of reducing the amount of methanol in the biodiesel composition by electrochemical oxidation of methanol to carbon dioxide.