Renewable aromatics from lignocellulosic lignin
The present invention provides novel and improved processes for treating a lignocellulosic biomass or technical lignin using ionic liquids to obtain lignin breakdown products.
1. A method comprising:
(i) contacting a starting material comprising a technical lignin with an ionic liquid to generate a solubilized material for at least about 3 hours at a temperature of at least about 160° C.; and
(ii) extracting low molecular weight or monomeric aromatic lignin compounds from the solubilized material with an extractant, wherein the extractant is a nonpolar solvent; and
(iii) optionally separating the extracted low molecular weight or monomeric aromatic lignin compounds resulting from step (ii) from the extractant.
2. The method of claim 1 , wherein step (ii) comprises
(a) precipitating a fraction of the solubilized material with a polar solvent to generate a precipitated fraction and a supernatant;
(b) separating the precipitated fraction from the supernatant; and
(c) extracting the low molecular weight or monomeric aromatic lignin compounds from the supernatant via liquid-liquid extraction with the nonpolar solvent.
3. The method of claim 2 , wherein the polar solvent of step (a) is selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol, or isooctanol.
4. The method of claim 1 , wherein the extractant is selected from the group consisting of benzene, toluene, pentane, hexane, heptane, octane, and isooctane.
5. The method of claim 2 , wherein step (ii) further comprises (d) separating the non-polar solvent from the supernatant.
6. The method of claim 1 , wherein the ionic liquid is water miscible.
7. The method of claim 1 , wherein the ionic liquid is [C 2 mim][OAc].
8. The method of claim 1 , wherein the technical lignin comprises kraft lignin, a lignosulfate, alkali lignin, low sulfonate alkali lignin, or a combination thereof.
9. The method of claim 1 , which comprises step (iii).
10. The method of claim 9 , wherein step (iii) comprises distillation or column fractionation.
11. The method of claim 1 , wherein the extractant is selected from the group consisting of benzene, hexane, and pentane.
12. The method of claim 2 , wherein the extractant is selected from the group consisting of benzene, hexane, and pentane.