Delignification of materials in deep eutectic solvents

Abstract

Embodiments of the present disclosure pertain to methods of removing lignin from a material by associating the material with a deep eutectic solvent (DES) that includes at least one hydrogen bond acceptor (HBA) and at least one hydrogen bond donor (HBD). The methods of the present disclosure may also include one or more steps of heating the solvent-associated material, separating the material from the solvent, drying the material, washing the material, and/or processing the material. Additional embodiments of the present disclosure pertain to delignified materials that are formed in accordance with the methods of the present disclosure.

What is claimed is: 
     
         1 . A method of removing lignin from a material, said method comprising:
 associating the material with a deep eutectic solvent comprising at least one hydrogen bond acceptor (HBA) and at least one hydrogen bond donor (HBD), wherein the solvent is operational to dissolve lignin associated with the material; and   heating the material.   
     
     
         2 . The method of  claim 1 , wherein the material is selected from the group consisting of lignocellulosic materials, biomass, woody biomass, untreated wood, fibers, lignocellulosic fibers, hemp, hemp bast fibers, kenaf, jute, sisal, flax, ramie, or combinations thereof. 
     
     
         3 . The method of  claim 1 , wherein the material comprises hemp. 
     
     
         4 . The method of  claim 1 , wherein the associating occurs by a method selected from the group consisting of mixing, immersing, sonicating, embedding, incubating, or combinations thereof. 
     
     
         5 . The method of  claim 1 , wherein the HBA comprises a quaternary ammonium salt selected in the group consisting of choline, betaine, proline, carnitine, acetylcholine, carnitine, ethyl ammonium chloride, diethyl ammonium chloride, a salt of a neutral compound with a positively charged cationic functional group, imidazolium, a substituted imidazolium salt, a quaternary ammonium compound, a substituted ammonium compound, pyridinium, a substituted pyridinium compound, a phosphonium compound, a morpholinium compound, or combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein the HBA comprises a neutral compound comprising a positively charged cationic functional group, wherein the positively charged cationic functional group is selected from the group consisting of choline, betaine, carnitine, imidazolium, substituted imidazolium, a quaternary ammonium, a substituted ammonium, pyridinium, a substituted pyridinium, phosphonium, morpholinium, or combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein the HBD is selected from the group consisting of urea, amide, a carboxylic acid, an amino acid, an amine, an amide, an alcohol, or combinations thereof. 
     
     
         8 . The method of  claim 1 , wherein the HBD comprises a carboxylic acid selected from the group consisting of lactic acid, oxalic acid, formic acid, glycolic acid, levulinic acid, malic acid, malonic acid, glutaric acid, succinic acid, tartaric acid, benzoic acid, itaconic acid, citric acid, isocitric acid, or combinations thereof. 
     
     
         9 . The method of  claim 1 , wherein the HBD comprises an alcohol selected from the group consisting of propylene glycol, 1,2-propanediol,1,3-propanediol, glycerol, ethylene glycol, triethylene glycol, sorbitol, xylitol, ribitol, erytritol, maltitol, mannitol, lactitol, inositol, butanediol, glycerol, or combinations thereof. 
     
     
         10 . The method of  claim 1 , wherein the HBA comprises choline chloride and the HBD comprises urea. 
     
     
         11 . The method of  claim 1 , wherein the HBA comprises choline chloride and the HBD comprises lactic acid. 
     
     
         12 . The method of  claim 1 , wherein the heating comprises thermal heating. 
     
     
         13 . The method of  claim 1 , wherein the heating comprises microwave radiation. 
     
     
         14 . The method of  claim 1 , further comprising a step of separating the material from the solvent, wherein the separating occurs after the solvent associating and heating steps. 
     
     
         15 . The method of  claim 1 , further comprising a step of drying the material, wherein the drying occurs after the solvent associating and heating steps. 
     
     
         16 . The method of  claim 1 , further comprising a step of washing the material, wherein the washing occurs after the solvent associating and heating steps. 
     
     
         17 . The method of  claim 1 , further comprising a step of processing the material. 
     
     
         18 . The method of  claim 17 , wherein the processing comprises at least one of opening the material, carding the material, blending the material with another material, yarn production from the material, fiber production from the material, or combinations thereof. 
     
     
         19 . The method of  claim 17 , wherein the processing comprises blending the material with another material. 
     
     
         20 . The method of  claim 19 , wherein the other material is selected from the group consisting of polymer fibers, cotton, polyester, wool, or combinations thereof. 
     
     
         21 . The method of  claim 17 , wherein the processing comprises yarn production from the material. 
     
     
         22 . The method of  claim 21 , wherein the processing further comprises fiber production from the yarn. 
     
     
         23 . The method of  claim 1 , further comprising a step of pre-treating the material prior to the solvent associating step. 
     
     
         24 . The method of  claim 23 , wherein the pre-treatment step comprises pre-treating the material with an alkali metal. 
     
     
         25 . The method of  claim 24 , wherein the alkali metal is selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), or combinations thereof.