Processes for producing nanocellulose, and nanocellulose compositions produced therefrom

1. A process for producing a nanocellulose material, said process comprising:

(a) providing a lignocellulosic biomass feedstock;

(b) digesting said feedstock with a reaction solution consisting essentially of steam and/or hot water in a digestor under effective reaction conditions to produce a digested stream containing cellulose-rich solids, hemicellulose oligomers, and lignin, wherein said effective reaction conditions include a digestion temperature selected from above 140° ° C. to 210° C.;

(c) optionally washing said cellulose-rich solids to remove at least a portion of said hemicellulose oligomers and at least a portion but not all of said lignin from said cellulose-rich solids;

(d) mechanically treating said cellulose-rich solids to form a nanocellulose material containing cellulose nanofibrils and/or cellulose nanocrystals, wherein said mechanically treating utilizes disk refining followed by homogenization of said cellulose-rich solids, wherein step (d) utilizes a mechanical-treatment power of about 20 to 200 kW/ton of solids; and

(e) recovering said nanocellulose material, wherein said nanocellulose material is hydrophobic due to the presence of lignin, and wherein said nanocellulose material is characterized by (i) an average particle effective diameter from about 5 nanometers to about 500 nanometers and (ii) an average particle effective length from about 100 nanometers to about 1000 nanometers,

and wherein process steps (a), (b), (c), (d), and (e) do not employ any enzymes, externally added acids, or combinations thereof.

2. The process of claim 1 , wherein step (d) is conducted at a solids consistency of at least 10 wt %.

3. The process of claim 1 , said process further comprising exploding cellulose fibers contained in said cellulose-rich solids.

4. The process of claim 1 , wherein step (d) utilizes a blow-line refiner, optionally with pressure reduction.

5. The process of claim 1 , wherein step (c) is conducted.

6. The process of claim 1 , said process further comprising bleaching said cellulose-rich solids and/or said nanocellulose material.

7. The process of claim 1 , wherein said nanocellulose material comprises said cellulose nanofibrils.

8. The process of claim 1 , wherein said nanocellulose material comprises a mixture of said cellulose nanofibrils and said cellulose nanocrystals.

9. The process of claim 1 , said process further comprising recovering, fermenting, or further treating hemicellulosic sugars derived from said hemicellulose oligomers.

10. The process of claim 1 , said process further comprising hydrolyzing a portion of said cellulose-rich solids into glucose, recovering said glucose, and optionally fermenting said glucose to a fermentation product.

11. The process of claim 1 , said process further comprising recovering, combusting, or further treating said lignin.

12. The process of claim 1 , said process further comprising chemically converting said nanocellulose material to one or more nanocellulose derivatives selected from the group consisting of nanocellulose esters, nanocellulose ethers, nanocellulose ether esters, alkylated nanocellulose compounds, cross-linked nanocellulose compounds, acid-functionalized nanocellulose compounds, base-functionalized nanocellulose compounds, and combinations thereof.

13. The process of claim 1 , wherein said digestion temperature is selected from 175° C. to 210° C.

14. The process of claim 1 , wherein said digestion temperature is selected from 175° C. to 195° C.