Stabilization of pyrolytic lignin
By derivatizing pyrolytic lignin with acetal and ester end-groups using a solvent-based process, the thermal instability issues of pyrolytic lignin are addressed, resulting in improved thermal stability and processability.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ALDER ENERGY LLC
- Filing Date
- 2026-01-22
- Publication Date
- 2026-07-30
AI Technical Summary
Pyrolytic lignin derived from fast pyrolysis oil exhibits poor thermal stability due to thermally reactive aldehyde, ketone, and carboxylic acid functional groups, leading to condensation and polymerization reactions that increase molecular weight and form coke during heating.
A process involving the use of a hydrophobic, aprotic solvent and an alcohol co-solvent to derivatize reactive carbonyl species in pyrolytic lignin at mild temperatures, forming acetal and ester end-groups to stabilize the lignin, followed by solvent recovery and purification.
The process enhances the thermal stability of pyrolytic lignin by preventing unwanted polymerization and improving its processability, allowing for efficient downstream use.
Smart Images
Figure US2026012165_30072026_PF_FP_ABST
Abstract
Description
Attorney Docket No.: 53826-0025WO1STABILIZATION OF PYROLYTIC LIGNINCROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Patent Application No. 63 / 748,412 filed on January 22, 2025, which is incorporated by reference herein in its entirety.TECHNICAL FIELD
[0002] This invention relates to chemically stabilizing pyrolytic lignin to improve its thermal stability.BACKGROUND
[0003] Fast pyrolysis oil (FPO) is a liquid product produced from fast pyrolysis of biomass. In the fast pyrolysis process, biomass is rapidly heated to 450-550°C in the absence of oxygen and with a short residence time, and rapidly quenched to produce FPO in the form of a condensate. Depending on the process conditions and the condensation train, FPO can either be a single phase mixture or a two-phase mixture with a heavy aromatic fraction (HAF) and a water-soluble organic fraction (WSOF).SUMMARY
[0004] This disclosure describes a process for chemically stabilizing a pyrolytic lignin derived from the fractionation of lignocellulosic biomass fast pyrolysis oil to improve its thermal stability.
[0005] In a first general aspect, treating a pyrolytic lignin isolated from fast pyrolysis oil includes combining a first solvated pyrolytic lignin and a liquid solvent including alcohol to yield a second solvated pyrolytic lignin including the liquid solvent, wherein the first solvated pyrolytic lignin includes carbonyl-containing species and heating the second solvated pyrolytic lignin to yield a stabilized pyrolytic lignin, wherein heating the second solvated pyrolytic lignin includes reacting the carbonyl-containing species with the liquid solvent in the solvated pyrolytic lignin to yield species with acetal and ester end-groups in the stabilized pyrolytic lignin.
[0006] Implementations of the first general aspect can include one or more of the following features. In some cases, the first solvated pyrolytic lignin includes 0.1 wt% to 2 wt% water, 1Attorney Docket No.: 53826-0025WO1wt% to 5 wt% acetic acid, formic acid, or a combination thereof, and 20 wt% to 50 wt% aprotic polar solvent. In some embodiments, the aprotic polar solvent includes ethyl acetate, methyl butyrate, ethyl butyrate, butyl acetate, methyl hexanoate, hexyl acetate, ethyl hexanoate, methyl isobutyl ketone, or a combination thereof. In some cases, the carbonyl-containing species include esters, ketones, and carboxylic acids.
[0007] In some embodiments, the second solvated pyrolytic lignin includes 10 wt% to 50 wt% of the liquid solvent. In some cases, the alcohol includes methanol, ethanol, 1 -propanol, 2-propanol, 1 -butanol, iso-butanol, 1 -pentanol, 2-pentanol, 3 -pentanol, 1 -hexanol, 2-hexanol, 3-hexanol, cyclohexanol, or a combination thereof.
[0008] In some cases, combining includes stirring, static in-line mixing, or counter-current flow through a column. The heating can occur at a temperature between 50°C and 80°C and in the absence of added catalyst. In some embodiments, the heating occurs in a vessel, and a pressure inside the vessel is between 10.3 kPa and 101.3 kPa. The duration of the heating can be in a range between 0.5 hours and 6 hours. In some cases, the heating occurs in a batch reactor, a continuous stirred tank reactor, or a continuous tubular reactor.
[0009] In some cases, treating the pyrolytic lignin isolated from fast pyrolysis oil further includes separating the alcohol from the stabilized pyrolytic lignin. In some embodiments, separating the alcohol from the stabilized pyrolytic lignin includes vacuum distilling the stabilized pyrolytic lignin. In some cases, vacuum distilling includes distilling at a temperature between 65°C and 80°C and pressure between 10.3 kPa and 31.0 kPa.
[0010] In some embodiments, separating the alcohol from the stabilized pyrolytic lignin includes solvent stripping. The solvent stripping can occur at a temperature between 50°C and 80°C and pressure between 10.3 kPa and 31.0 kPa.
[0011] In a second general aspect, the stabilized pyrolytic lignin includes an acetal functionalized pyrolytic lignin moiety, an ester functionalized pyrolytic lignin moiety, an unreacted pyrolytic lignin from the first solvated pyrolytic lignin, and a viscosity modifier.
[0012] Implementations of the second general aspect can include one or more of the following features. In some cases, the viscosity modifier includes an alcohol viscosity modifier, and the alcohol viscosity modifier includes methanol, ethanol, 1 -propanol, 2-propanol, 1 -butanol, iso-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, cyclohexanol, or a combination thereof.Attorney Docket No.: 53826-0025WO1
[0013] In some embodiments, the stabilized pyrolytic lignin includes about 4 wt% to about 20 wt% of the alcohol viscosity modifier. In some cases, the viscosity modifier further includes an ester viscosity modifier, and the ester viscosity modifier includes ethyl acetate, methyl butyrate, ethyl butyrate, butyl acetate, methyl hexanoate, hexyl acetate, ethyl hexanoate, methyl isobutyl ketone, or a combination thereof.
[0014] The details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a reaction scheme for chemical stabilization of pyrolytic lignin via alcohol end-group capping of reactive aldehyde, ketone, and carboxylic acid moieties.DETAILED DESCRIPTION
[0016] The fast pyrolysis of biomass produces a liquid bio-oil that is comprised of water, monomeric oxygenates, pyrolytic lignin, and pyrolytic sugar. Pyrolytic lignin is defined as the water insoluble fraction of fast pyrolysis oil, and it is a complex mixture of organic compounds comprised predominantly of aromatic oligomeric species derived from the lignin component in biomass. Pyrolytic lignin can be isolated from fast pyrolysis oil by several methods, including via liquid-liquid extraction, cold water precipitation, or solvent fractionation. The resulting pyrolytic lignin can be a highly viscous liquid to a semi-solid or solid in the absence of any solvents. Pyrolytic lignin typically contains thermally reactive aldehyde, ketone, and carboxylic acid functional groups. When heat is applied, condensation and polymerization reactions can occur at these functional groups, leading to increased molecular weight and coke formation during heating or drying.
[0017] This disclosure describes a process for chemically stabilizing pyrolytic lignin to improve its thermal stability. As described herein, pyrolytic lignin is initially suspended in a hydrophobic, aprotic, semi-polar solvent to remove any remaining water and improve the liquid flowability. This can be performed as part of a fractionation step or following cold water precipitation. An alcohol co-solvent is then added in excess (e g., in a molar excess relative toAttorney Docket No.: 53826-0025WO1carbonyl groups on the pyrolytic lignin). Mild heat (e.g., below 80 °C) is applied for a sufficient amount of time to derivatize the reactive carbonyl species, producing acetal and ester end-groups. FIG. 1 is a reaction scheme for chemical stabilization of pyrolytic lignin via alcohol end-group capping of reactive aldehyde, ketone, and carboxylic acid moieties.
[0018] The use of excess alcohol promotes the reaction at mild temperatures without the need for (e.g., in the absence of) added catalyst. Process conditions are controlled to avoid competing condensation reactions which lead to unwanted polymerization of pyrolytic lignin into high molecular mass species.
[0019] The stabilized pyrolytic lignin solution can be further purified to recover the aprotic solvent and excess alcohol for recycle. Solvent recovery can take place by distillation or solvent stripping. Solvents can be partially retained in the stabilized pyrolytic lignin product to moderate the viscosity for downstream processing. If desired, the reaction and distillation step can be performed in a single unit operation to functionalize the pyrolytic lignin and recover the solvent.
[0020] Although this disclosure contains many specific embodiment details, these should not be construed as limitations on the scope of the subject matter or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments can also be implemented, in combination, in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments, separately, or in any suitable sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.
[0021] Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results.Attorney Docket No.: 53826-0025WO1
[0022] Accordingly, the previously described example embodiments do not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.
Claims
Attorney Docket No.: 53826-0025WO1WHAT TS CLAIMED IS:
1. A process for treating a pyrolytic lignin isolated from fast pyrolysis oil, the process comprising:combining a first solvated pyrolytic lignin and a liquid solvent comprising alcohol to yield a second solvated pyrolytic lignin comprising the liquid solvent, wherein the first solvated pyrolytic lignin comprises carbonyl-containing species; andheating the second solvated pyrolytic lignin to yield a stabilized pyrolytic lignin, wherein heating the second solvated pyrolytic lignin comprises reacting the carbonyl-containing species with the liquid solvent in the solvated pyrolytic lignin to yield species with acetal and ester end-groups in the stabilized pyrolytic lignin.
2. The process of claim 1, wherein the first solvated pyrolytic lignin comprises:0.1 wt% to 2 wt% water;1 wt% to 5 wt% acetic acid, formic acid, or a combination thereof; and20 wt% to 50 wt% aprotic polar solvent.
3. The process of claim 2, wherein the aprotic polar solvent comprises ethyl acetate, methyl butyrate, ethyl butyrate, butyl acetate, methyl hexanoate, hexyl acetate, ethyl hexanoate, methyl isobutyl ketone, or a combination thereof.
4. The process of claim 1, wherein the carbonyl-containing species comprise esters, ketones, and carboxylic acids.
5. The process of claim 1, wherein the second solvated pyrolytic lignin comprises 10 wt% to 50 wt% of the liquid solvent.
6. The process of claim 1, wherein the alcohol comprises methanol, ethanol, 1 -propanol, 2-propanol, 1 -butanol, iso-butanol, 1 -pentanol, 2-pentanol, 3 -pentanol, 1 -hexanol, 2-hexanol, 3-hexanol, cyclohexanol, or a combination thereof.Attorney Docket No.: 53826-0025WO17. The process of claim 1, wherein the combining comprises stirring, static in-line mixing, or counter-current flow through a column.
8. The process of claim 1, wherein the heating occurs at a temperature between 50°C and 80°C.
9. The process of claim 1, wherein the heating occurs in the absence of added catalyst.
10. The process of claim 1, wherein the heating occurs in a vessel, and a pressure inside the vessel is between 10.3 kPa and 101.3 kPa.
11. The process of claim 1, wherein a duration of the heating is in a range between 0.5 hours and 6 hours.
12. The process of claim 1, wherein the heating occurs in a batch reactor, a continuous stirred tank reactor, or a continuous tubular reactor.
13. The process of claim 1, further comprising separating the alcohol from the stabilized pyrolytic lignin.
14. The process of claim 13, wherein separating the alcohol from the stabilized pyrolytic lignin comprises vacuum distilling the stabilized pyrolytic lignin.
15. The process of claim 14, wherein the vacuum distilling comprises distilling at a temperature between 65°C and 80°C and pressure between 10.3 kPa and 31.0 kPa.
16. The process of claim 14, wherein separating the alcohol from the stabilized pyrolytic lignin comprises solvent stripping.
17. The process of claim 16, wherein the solvent stripping occurs at a temperature between 50°C and 80°C and pressure between 10.3 kPa and 31.0 kPa.Attorney Docket No.: 53826-0025WO118. The stabilized pyrolytic lignin of claim 1, comprisingan acetal functionalized pyrolytic lignin moiety;an ester functionalized pyrolytic lignin moiety;unreacted pyrolytic lignin from the first solvated pyrolytic lignin; and a viscosity modifier.
19. The stabilized pyrolytic lignin of claim 18, wherein the viscosity modifier comprises an alcohol viscosity modifier, and the alcohol viscosity modifier comprises methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, iso-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3 -hexanol, cyclohexanol, or a combination thereof.
20. The stabilized pyrolytic lignin of claim 19, wherein the stabilized pyrolytic lignin comprises about 4 wt% to about 20 wt% of the alcohol viscosity modifier.
21. The stabilized pyrolytic lignin of claim 18, wherein the viscosity modifier further comprises an ester viscosity modifier, and the ester viscosity modifier comprises ethyl acetate, methyl butyrate, ethyl butyrate, butyl acetate, methyl hexanoate, hexyl acetate, ethyl hexanoate, methyl isobutyl ketone, or a combination thereof.