Fractionation of a lignocellulosic material
A method for fractionating a lignocellulosic material, the method comprising; contacting ( 2 ) the lignocellulosic material with an ionic liquid ( 3 ) and dissolving the lignocellulosic material therein, providing a second liquid ( 7 ) which is immiscible with the ionic liquid and is also a non-solvent for cellulose, adding the second liquid to the ionic liquid so as to form a biphasic system ( 6 ) which comprises an ionic liquid phase essentially free of lignocellulose and a second liquid phase comprising lignin in solution and cellulose as a precipitate, separating the two phases and recovering ( 8 ) the precipitated cellulose from the separated second liquid phase.
1. A method for fractionating a lignocellulosic material, the method comprising:
contacting the lignocellulosic material with an ionic liquid and dissolving the lignocellulosic material therein;
providing a second liquid which is immiscible with the ionic liquid and is also a non-solvent for cellulose, wherein the second liquid is an aqueous hydroxide solution;
adding the second liquid to the ionic liquid so as to form a biphasic system which comprises an ionic liquid phase essentially free of lignocellulose and a second liquid phase comprising lignin in solution and cellulose as a precipitate;
separating the two phases;
recovering the precipitated cellulose from the separated second liquid phase;
decreasing the pH of the separated second liquid phase until the lignin precipitates therefrom; and
recovering the precipitated lignin.
2. The method of claim 1 , wherein the hydroxide is sodium hydroxide.
3. The method of claim 1 , wherein the ionic liquid is heated to a temperature between 120 to about 190° C.
4. The method of claim 1 , further comprising the step of recovering hemicellulose from the separated second liquid phase after recovery of the lignin.
5. The method of claim 1 , wherein the lignocellulosic material comprises at least some water.
6. The method of claim 5 , wherein the lignocellulosic material comprises up to about 70% water.
7. The method of claim 1 , wherein the lignocellulosic material comprises bagasse.
8. The method of claim 1 , further comprising recycling the ionic liquid phase after separating the two phases; and contacting fresh lignocellulosic material with the recycled ionic liquid phase.
9. The method of claim 1 , wherein the aqueous hydroxide solution is an aqueous sodium hydroxide solution between about 10 to about 25 w/v%.
10. A method for producing ethanol, the method comprising:
contacting a lignocellulosic material with an ionic liquid and dissolving the lignocellulosic material therein;
providing a second liquid which is immiscible with the ionic liquid and is also a non-solvent for cellulose;
adding the second liquid to the ionic liquid so as to form a biphasic system which comprises an ionic liquid phase essentially free of lignocellulose and a second liquid phase comprising lignin in solution and cellulose as a precipitate, wherein the second liquid is an aqueous hydroxide solution
separating the two phases;
recovering the precipitated cellulose from the separated second liquid phase;
subjecting the recovered cellulose to hydrolysis and fermentation,
decreasing the pH of the separated second liquid phase until the lignin precipitates therefrom; and
recovering the precipitated lignin.