Method for Purifying Biodiesel Fuel

Abstract

A method for purifying a biodiesel fuel includes the use of subjecting a biodiesel fuel to an electric field. The electric field forms a precipitate in the fuel that removes the impurities of excess catalysts and soap that are byproducts of the reaction that forms the biodiesel. This electric field assisted washing process can be applied to a biodiesel fuel in a batch process or, alternatively, in a continuous process.

1 . A method for purifying a biodiesel fuel comprising the steps of:
 providing a triglyceride, methanol, and homogeneous catalyst;   reacting a mixture of the triglyceride, methanol and catalyst to form a reaction product comprising a glycerol fraction and a crude biodiesel fuel fraction;   separating the glycerol and crude biodiesel fuel fractions;   subjecting the biodiesel fuel fraction to an electric field to form a precipitate in the crude biodiesel fuel fraction; and   removing the precipitate from the remaining biodiesel fuel fraction;   whereby the remaining biodiesel fuel fraction after removal of the precipitate is more purified than the crude fraction.   
   
   
       2 . A method for purifying a biodiesel fuel as described in  claim 1 , wherein the triglyceride is selected from the group consisting of triglycerides with long chain carbon and hydrogen atoms consisting of 11 to 18 carbon atoms, vegetable oil, soybean oil, corn oil, rapeseed oil, canola oil, peanut oil, cottonseed oil, safflower oil, linseed oil, coconut oil, animal fat, lard, tallow and mixtures thereof. 
   
   
       3 . A method for purifying a biodiesel fuel as described in  claim 1 , wherein the homogeneous catalyst is selected from the group consisting of sodium hydroxide, potassium hydroxide, and sodium methoxide. 
   
   
       4 . A method for purifying a biodiesel fuel as described in  claim 1 , wherein the crude biodiesel fuel fraction comprises methyl esters. 
   
   
       5 . A method for purifying a biodiesel fuel as described in  claim 1 , wherein the step of subjecting the crude biodiesel fraction to an electric field is performed in a batch process. 
   
   
       6 . A method for purifying a biodiesel fuel as described in  claim 1 , wherein the step of subjecting the crude biodiesel fraction to an electric field is performed in a continuous process. 
   
   
       7 . A method for purifying a biodiesel fuel as described in  claim 1 , wherein the electric field has a strength of at least about 20 V/cm. 
   
   
       8 . A method for purifying a biodiesel fuel as described in  claim 1 , wherein the electric field has a strength in the range of about 10 to 200 V/cm. 
   
   
       9 . A method of purifying a crude biodiesel fuel comprising the steps of providing a crude biodiesel fuel formed by a process comprising homogeneous catalysis;
 placing the crude biodiesel fuel in an electric field to form a precipitate;   removing the precipitate from the crude biodiesel fuel.   
   
   
       10 . A method for purifying a biodiesel fuel as described in  claim 9 , wherein the crude biodiesel fuel fraction comprises methyl esters. 
   
   
       11 . A method for purifying a biodiesel fuel as described in  claim 9 , wherein the step of subjecting the crude biodiesel fraction to an electric field is performed in a batch process. 
   
   
       12 . A method for purifying a biodiesel fuel as described in  claim 9 , wherein the step of subjecting the crude biodiesel fraction to an electric field is performed in a continuous process. 
   
   
       13 . A method for purifying a biodiesel fuel as described in  claim 9 , wherein the electric field has a strength of at least about 20 V/cm. 
   
   
       14 . A method for purifying a biodiesel fuel as described in  claim 9 , wherein the electric field has a strength in the range of about 10 and 200 V/cm.