Solute-enhanced production of gamma-valerolactone (GVL) from aqueous solutions of levulinic acid
A method to produce levulinic acid (LA) and gamma-valerolactone (GVL) from biomass-derived cellulose or lignocellulose by selective extraction of LA using GVL and optionally converting the LA so isolated into GVL, with no purifications steps required to yield the GVL.
1. A method to isolate levulinic acid (LA), the method comprising:
(a) producing an aqueous solution comprising LA by deconstructing cellulose, hemicellulose, glucose, xylose, oligomers thereof or combinations thereof, in an aqueous, acidic reaction solution, to yield the aqueous solution comprising LA or an aqueous solution comprising LA and fufural; and then
(b) adding a sufficient concentration of a water-soluble solute to the aqueous solution of step (a) to yield an aqueous solution that is substantially immiscible with gamma-valerolactone (GVL); and then
(c) extracting LA from the aqueous solution of step (b) using an extraction solvent comprising GVL;
wherein the aqueous solution comprising LA of step (a) is produced in a biphasic system having a first phase and a second phase, wherein the first phase comprises the aqueous, acidic reaction solution and the second phase comprises GVL, and wherein the first and second phases are substantially immiscible.
2. The method of claim 1 , wherein the aqueous, acidic reaction solution of step (a) comprises an acid selected from the group consisting of solid acids, hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, trifluoroacetic acid, hydrobromic acid, acetic acid, oxalic acid, toluenesulfonic acid, and Lewis acids.
3. The method of claim 1 , wherein the water-soluble solute of step (b) is a water-soluble salt, monosaccharide, disaccharide, or trisaccharide.
4. The method of claim 3 , wherein the water-soluble solute is sodium chloride or fructose.
5. The method of claim 3 , wherein the waters-soluble salt is sodium chloride.
6. The method of claim 5 , wherein the sodium chloride is present in a concentration of from about 6 wt % to about 35 wt % (saturation), based on the weight of the water in the aqueous solution.
7. The method of claim 1 , further comprising, after step (c):
(d) converting all or a portion of the extracted LA into GVL.
8. The method of claim 7 , wherein step (d) comprises converting the LA into GVL in the presence of a catalyst comprising one or more metals from Groups 6-14 of the periodic chart.
9. The method of claim 7 , wherein step (d) comprises converting the LA into GVL in the presence of a catalyst comprising ruthenium, nickel, platinum, rhodium, tin, copper, and combinations thereof.
10. The method of claim 9 , wherein the catalyst comprises ruthenium and tin.