Method for producing biodiesel

Abstract

A method for producing biodiesel includes feeding methanol into a tank and heating methanol to a temperature above a critical temperature of methanol to obtain a supercritical methanol. A reactive matrix is fed into the tank. The reactive matrix includes acetic acid and a material oil. A molar ratio of acetic acid to the material oil is in a range from 1:1 to 5:1. A molar ratio of methanol to the material oil is in a range from 20:1 to 90:1. A supercritical carbon dioxide is fed into the tank. A total pressure of the supercritical methanol and the supercritical carbon dioxide is higher than 10 MPa. The supercritical methanol, the material oil, acetic acid, and the supercritical carbon dioxide react with each other in the tank at 240-500° C. and 8.1-50 MPa for 0.1-1.5 hours to obtain biodiesel.

What is claimed is: 
     
         1 . A method for producing biodiesel comprising:
 feeding methanol into a tank and heating methanol to a temperature above a critical temperature of methanol to obtain a supercritical methanol;   feeding a reactive matrix into the tank, with the reactive matrix including acetic acid and a material oil, with a molar ratio of acetic acid to the material oil being in a range from 1:1 to 5:1, with a molar ratio of methanol to the material oil being in a range from 20:1 to 90:1; and   adding a supercritical carbon dioxide into the tank, with a total pressure of the supercritical methanol and the supercritical carbon dioxide being higher than 10 MPa,   wherein the supercritical methanol, the material oil, acetic acid, and the supercritical carbon dioxide react with each other in the tank at 240-500° C. and 8.1-50 MPa for 0.1-1.5 hours to obtain biodiesel.   
     
     
         2 . The method as claimed in  claim 1 , wherein the molar ratio of methanol to the material oil is 60:1. 
     
     
         3 . The method as claimed in  claim 1 , wherein the molar ratio of acetic acid to the material oil is 3:1. 
     
     
         4 . The method as claimed in  claim 2 , wherein a volumetric ratio of methanol to the material oil is 2.5:1. 
     
     
         5 . The method as claimed in  claim 3 , wherein a volumetric ratio of acetic acid to the material oil is 1:6.4. 
     
     
         6 . The method as claimed in  claim 1 , wherein methanol is heated to a temperature in a range of 240-500° C. to obtain the supercritical methanol. 
     
     
         7 . The method as claimed in  claim 1 , wherein the material oil is selected from the group consisting of plant oils, animal oils, waste cooking oils, and oils or fats containing glycerol ester and fatty acids and combinations thereof. 
     
     
         8 . The method as claimed in  claim 7 , wherein the material oil is soybean oil. 
     
     
         9 . The method as claimed in  claim 1 , wherein supercritical methanol, the material oil, acetic acid, and the supercritical carbon dioxide react with each other in the tank at 280° C. and 20 MPa. 
     
     
         10 . The method as claimed in  claim 1 , wherein supercritical methanol, the material oil, acetic acid, and the supercritical carbon dioxide react with each other in the tank for 90 minutes.