Molten Carboxylate Electrolytes for Electrochemical Decarboxylation Processes

Abstract

Molten salt electrolytes are described for use in electrochemical synthesis of hydrocarbons from carboxylic acids. The molten salt electrolyte can be used to synthesize a wide variety of hydrocarbons with and without functional groups that have a broad range of applications. The molten salt can be used to synthesize saturated hydrocarbons, diols, alkylated aromatic compounds, as well as other types of hydrocarbons. The molten salt electrolyte increases the selectivity, yield, the energy efficiency and Coulombic efficiency of the electrochemical conversion of carboxylic acids to hydrocarbons while reducing the cell potential required to perform the oxidation.

1 . An electrochemical cell comprising:
 an electrolyte compartment with a quantity of electrolyte, the electrolyte comprising a quantity of an inorganic salt of a carboxylic acid dissolved in a molten salt electrolyte;   an anode in communication with the electrolyte;   a cathode in communication with the electrolyte; and   a voltage source that decarboxylates the metal salt of the carboxylic acid into radicals that react to form at least one radical coupling product.   
     
     
         2 . The cell of  claim 1 , wherein the cation of the electrolyte inorganic salt is selected from an alkaline metal, an alkaline earth metal, and mixtures of the same. 
     
     
         3 . The cell of  claim 1 , wherein the cation of the electrolyte inorganic salt is selected from ammonium, lithium, sodium, potassium, magnesium, calcium, and mixtures of the same. 
     
     
         4 . The cell of  claim 2 , wherein the electrolyte contains a mixture of inorganic cations. 
     
     
         5 . The cell of  claim 2 , wherein the electrolyte contains a mixture of at least three inorganic cations. 
     
     
         6 . The cell of  claim 2 , wherein the oxidation potential of an anion in the molten electrolyte is higher than the oxidation potential of the carboxylate anion. 
     
     
         7 . The cell of  claim 2 , wherein a carboxylate portion of the carboxylate inorganic salt is selected from: acetate, propionate, lactate, butyrate, pentanoate, hexanoate, heptanoate, octanoate, laurate, oleate, stearate, linoleate, palmitate, myristrate, levulinate, valerate, benzoate, naphthenate and naphthoate. 
     
     
         8 . The cell of  claim 2 , wherein the electrolyte is a eutectic mixture with a lower melting point than the melting point of the individual components of the electrolyte mixture. 
     
     
         9 . The cell of  claim 2 , wherein the cell is operated at a temperature above the melting point of the molten salt electrolyte, but below the melting point of the products of the reduction and oxidation reactions. 
     
     
         10 . An electrochemical cell comprising:
 an anolyte compartment housing an anolyte comprising a inorganic salt of a carboxylic acid dissolved in a molten salt electrolyte;   an anode in communication with the anolyte;   a catholyte compartment capable of housing a quantity of catholyte;   a cathode in communication with the catholyte;   a membrane separating the anolyte and catholyte compartments; and   a voltage source.   
     
     
         11 . The cell of  claim 10 , wherein the cation of the electrolyte inorganic salt is selected from an alkaline metal, an alkaline earth metal and mixtures of the same. 
     
     
         12 . The cell of  claim 11 , wherein the cation of the electrolyte inorganic salt is selected from lithium, sodium, potassium, magnesium, calcium, and mixtures of the same. 
     
     
         13 . The cell of  claim 12 , wherein the electrolyte contains a mixture of inorganic cations. 
     
     
         14 . The cell of  claim 12 , wherein the electrolyte contains a mixture of at least three inorganic cations. 
     
     
         15 . The cell of  claim 12 , wherein the oxidation potential of an anion in the molten electrolyte is higher than the oxidation potential of the carboxylate anion. 
     
     
         16 . The cell of  claim 12 , wherein a carboxylate portion of the inorganic carboxylate salt is selected from: acetate, propionate, lactate, butyrate, pentanoate, hexanoate, heptanoate, octanoate, laurate, oleate, stearate, linoleate, palmitate, myristrate, levulinate, valerate, benzoate, naphthenate and naphthoate. 
     
     
         17 . The cell of  claim 12 , wherein the electrolyte is a eutectic mixture with a lower melting point than the melting point of the individual components of the electrolyte mixture. 
     
     
         18 . The cell of  claim 12 , wherein the cell is operated at a temperature above the melting point of the molten salt electrolyte, but below the melting point of the products of the reduction and oxidation reactions. 
     
     
         19 . A method for producing a coupled radical product, comprising:
 providing a inorganic salt of a carboxylic acid;   contacting the salt of a carboxylic acid with a molten salt electrolyte   applying a voltage to the electrolyte and carboxylate salt.   
     
     
         20 . The method of  claim 19 , wherein the electrolyte is a eutectic mixture with a lower melting point than the melting point of the individual components of the electrolyte mixture.