Processes and apparatus for producing nanocellulose, and compositions and products produced therefrom
Processes disclosed are capable of converting biomass into high-crystallinity nanocellulose with surprisingly low mechanical energy input. In some variations, the process includes fractionating biomass with an acid (such as sulfur dioxide), a solvent (such as ethanol), and water, to generate cellulose-rich solids and a liquid containing hemicellulose and lignin; and mechanically treating the cellulose-rich solids to form nanofibrils and/or nanocrystals. The crystallinity of the nanocellulose material may be 80% or higher, translating into good reinforcing properties for composites. The nanocellulose material may include nanofibrillated cellulose, nanocrystalline cellulose, or both. In some embodiments, the nanocellulose material is hydrophobic via deposition of some lignin onto the cellulose surface. Optionally, sugars derived from amorphous cellulose and hemicellulose may be separately fermented, such as to monomers for various polymers. These polymers may be combined with the nanocellulose to form completely renewable composites.
1. A nanocellulose composition comprising nanocrystalline cellulose with a cellulose crystallinity of about 80% or greater, wherein said nanocellulose composition contains nanocellulose particles having a surface concentration of lignin that is greater than a bulk concentration of lignin, and wherein said nanocrystalline cellulose is characterized by a nanometer-sized average nanocrystal particle width.
2. The nanocellulose composition of claim 1 , wherein said cellulose crystallinity is about 85% or greater.
3. The nanocellulose composition of claim 1 , wherein said nanocellulose composition is characterized by an average cellulose degree of polymerization from about 100 to about 1000.
4. The nanocellulose composition of claim 1 , wherein said nanocellulose composition is characterized by a cellulose degree of polymerization distribution having a single peak.
5. The nanocellulose composition of claim 1 , wherein said nanocrystalline cellulose is characterized by a nanometer-sized average nanocrystal particle length.
6. The nanocellulose composition of claim 1 , wherein said nanocellulose composition is not derived from tunicates.
7. The nanocellulose composition of claim 1 , wherein said nanocellulose composition is not derived from bacterial cellulose.
8. The nanocellulose composition of claim 1 , wherein said nanocellulose composition is free of enzymes.
9. The nanocellulose composition of claim 1 , wherein said nanocellulose composition contains sulfur.
10. The nanocellulose composition of claim 1 , wherein said nanocellulose composition further comprises nanofibrillated cellulose.