Catalyst and method for fractionating lignocellulosic material
Various embodiments disclosed relate to solid catalysts that convert lignocellulosic material to monomer sugars that are suitable for fermentation. The solid catalysts include a transition metal complex attached to a magnetic bead, and can be physically separated from a fermentation mixture and reused several times.
1. A method of fractionation of a lignocellulosic feedstock, comprising:
treating the lignocellulosic feedstock with an amount of a catalyst immobilized on a solid magnetic metal-containing support via a linker group comprising a silane on one terminal end, wherein the catalyst comprises a nickel coordinated to a cyclooctadiene ligand and an n-heterocyclic carbene and the amount of catalyst is 0.0001 wt % to 2 wt % relative to the weight of the lignocellulosic feedstock; and
heating the treated lignocellulosic feedstock under pressure.
2. The method of claim 1 , wherein the catalyst has the structure of Formula I:
wherein
X is a counterion;
L is a linker group comprising a silane on one terminal end;
MB is a solid magnetic metal-containing bead support; and
R 1 and R 2 is each independently C 1-10 alkyl, C 7-10 aralkyl, C 6 -C 12 aryl, or C 2-8 heterocyclyl, each of which may be optionally substituted.
3. The method of claim 2 , wherein the treating comprises mechanical and chemical degradation of the lignocellulosic feedstock.
4. The method of claim 3 , wherein the chemical degradation comprises selective cleavage of the β-1, 4 glycosidic bonds of cellulose by the catalyst.
5. The method of claim 3 , wherein the mechanical degradation is due to mechanical abrasion of the lignocellulosic feedstock by the catalyst.
6. The method of claim 2 , wherein the solid magnetic metal-containing bead support comprises iron oxide.
7. The method of claim 2 , wherein the solid magnetic metal-containing bead support has an average size of 0.001 micrometer to 100 micrometer.
8. The method of claim 2 , wherein 10% to 100% of the surface of the bead is coated by amorphous silica.
9. The method of claim 8 , wherein the linker covalently binds to the silica surface of the metal-containing bead.
10. The method of claim 2 , wherein the linker comprises a silane on one terminal end attached to a silica surface of the solid magnetic metal-containing solid bead support, and the linker further comprises a carbamate, urea, thiocarbamate, thiourea, amide or ester on another terminal end which covalently binds to the remainder of the catalyst.
11. The method of claim 10 , wherein the silane is a siloxane.
12. The method of claim 2 , wherein the linker is attached according to the structure:
13. The method of claim 2 , wherein R 1 and R 2 are each independently
and R 3 , R 4 , R 5 , R 6 and R 7 are each independently H,
C 1 -C 10 alkyl, wherein at 10% to 100% of the surface of the bead is uniformly coated with amorphous silica.
14. The method of claim 2 , wherein R 1 and R 2 are
15. The method of claim 2 , wherein R 1 and R 2 are
16. The method of claim 1 , further comprising magnetically separating the catalyst from the treated lignocellulosic feedstock.
17. The method of claim 1 , wherein fractionation is performed directly on the lignocellulosic feedstock without a separate step to separate lignin.
18. The method of claim 1 , wherein the fractionation produces a fractionated composition having a liquid phase comprising monosaccharides and a solid phase.
19. The method of claim 1 , wherein the fractionation is performed at a temperature of 300° C. to 400° C., at a pressure between 1 and 10 bar, for 10 minutes to 5 hours.