Production of Cellulose Nanocrystals From Raw Wood Via Hydrothermal Treatment

Abstract

A method comprises subjecting raw wood comprising cellulose, lignin and hemicellulose to a heat treatment at a crystallization temperature in the range of from about 150° C. to about 250° C. for a period of time sufficient to induce crystallization of cellulose in the raw wood, wherein the crystallinity of the processed raw wood as measured after delignification using 380 Raman is at least 5% greater than the crystallinity of the raw wood as measured after delignification and prior to processing using 380 Raman. The method can further comprise extracting CNCs from the processed raw wood via an acid hydrolysis procedure.

What is claimed is: 
     
         1 . A method for forming crystalline cellulose in raw wood, the method comprising subjecting raw wood comprising cellulose, lignin and hemicellulose to a heat treatment at a crystallization temperature in the range of from about 150° C. to about 250° C. for a period of time sufficient to induce crystallization of cellulose in the raw wood, wherein the crystallinity of the processed raw wood as measured after delignification using 380 Raman is at least 5% greater than the crystallinity of the raw wood as measured after delignification and prior to processing using 380 Raman. 
     
     
         2 . The method of  claim 1 , wherein the crystallinity of the processed raw wood as measured after delignification using 380 Raman is at least 12% greater than the crystallinity of the raw wood as measured after delignification and prior to processing using 380 Raman. 
     
     
         3 . The method of  claim 1 , wherein the period of time is at least 30 minutes. 
     
     
         4 . The method of  claim 1 , wherein the crystallization temperature is in the range of from about 170° C. to about 230° C. 
     
     
         5 . The method of  claim 1 , wherein the raw wood is provided as a wood blend comprising the raw wood, water and optionally, a salt, a buffer, or a combination thereof. 
     
     
         6 . The method of  claim 5 , wherein the wood blend consists essentially of the raw wood, water and optionally, the salt, the buffer, or the combination thereof. 
     
     
         7 . The method of  claim 1 , wherein the processed raw wood exhibits an accessibility to water of less than 26% as measured from the processed raw wood after delignification using 1380 Raman. 
     
     
         8 . The method of  claim 1 , wherein the processed raw wood exhibits an accessibility to water of less than 20% as measured from the processed raw wood after delignification using 1380 Raman. 
     
     
         9 . The method of  claim 1 , further comprising removing lignin from the processed raw wood via a delignification procedure. 
     
     
         10 . The method of  claim 1 , wherein the heat treatment does not convert the raw wood to pulped wood. 
     
     
         11 . A method of producing cellulose nanocrystals (CNCs) from raw wood, the method comprising:
 subjecting raw wood comprising cellulose, lignin and hemicellulose to a heat treatment at a crystallization temperature in the range of from about 150° C. to about 250° C. for a period of time sufficient to induce crystallization of cellulose in the raw wood, wherein the crystallinity of the processed raw wood as measured after delignification using 380 Raman is at least 5% greater than the crystallinity of the raw wood as measured after delignification and prior to processing using 380 Raman; and   extracting CNCs from the processed raw wood via an acid hydrolysis procedure.   
     
     
         12 . The method of  claim 11 , wherein the extracted CNCs comprise lignin. 
     
     
         13 . The method of  claim 12 , wherein the Klason lignin content of the CNCs is about 20% or greater. 
     
     
         14 . The method of  claim 11 , further comprising removing lignin from the processed raw wood via a delignification procedure prior to extraction of CNCs. 
     
     
         15 . The method of  claim 11 , wherein the CNCs are characterized by an average length in the range of from about 50 nm to about 350 nm as measured using transmission electron microscopy (TEM). 
     
     
         16 . The method of  claim 11 , wherein the CNCs are characterized by an average width in the range of from about 4 nm to about 20 nm as measured using TEM. 
     
     
         17 . The method of  claim 16 , wherein the width distribution of the CNCs is less than about 2 nm as measured using atomic force microscopy (AFM). 
     
     
         18 . The method of  claim 11 , wherein the heat treatment does not convert the raw wood to pulped wood. 
     
     
         19 . Cellulose nanocrystals comprising lignin and having a Klason lignin content of about 20% or greater.