Catalytic lignin extraction and depolymerization from biomass

Abstract

The present disclosure relates to methods for using biomass for the extraction and depolymerization of lignin into phenolic monomers.

Description

CATALYTIC LIGNIN EXTRACTION AND DEPOLYMERIZATION FROM BIOMASSCROSS REFERENCE TO RE ATED APPLICATIONS

[0001] This application claim priority to U.S. Provisional Application No. 63 / 670,091, filed on July 11, 2024, the entirety of which is herein incorporated by reference.FIELD

[0002] The present disclosure relates to methods for the depolymerization of lignin into phenolic monomers.BACKGROUND

[0003] Lignin, a crucial component of plant cell walls, is the second most abundant biopolymer, constituting 10%-30% of biomass. The structure of lignin is a complex network of cross-links including C-O-C ether linkages (67%-75%) and p-Coumaryl (H), Coniferyl (G), and Sinapyl (S) units. These units form a highly branched, three-dimensional structure and functionally provide mechanical strength and protection for plant cell walls. Additionally, lignin acts as a natural adhesive binding cellulose and hemicellulose fibers within plants.

[0004] Lignin, composed of monomeric aromatic compounds, holds significant promise as a feedstock for producing value-added products such as plastics, hydrogels, adhesives, chemicals, and fuels. Despite its potential, lignin's utilization has been limited due to its recalcitrance and lignin derived from biomass has been regarded as a mere waste byproduct, often utilized solely for its calorific value through combustion in various applications. Current biorefinery processes using lignin combustion is also plagued by air pollutant emissions such as benzene and styrene; making a process that harnesses the value-added products increase profits and reduce environmental impacts in a synergistic manner, namely by increasing the biorefinery product portfolio and reducing the size of the boiler (see Corona et. al. Green Chemistry, (2018), 20(16), 3857 incorporated herein by reference with regard to such teaching).SUMMARY OF THE DISCLOSURE

[0005] The present disclosure provides a method for efficient and ecologically sustainable extraction and depolymerization of lignan from biomass. The resulting lignan output may be customized for particular end use.

[0006] In one embodiment, the present disclosure relates to a method of depolymerizing lignin from biomass, the method comprising: providing biomass from saw dust or com stover; extracting the lignin from the biomass in solvent phase; depolymerizing the lignin by catalytic fractionation utilizing a catalyst and solvent under supercritical conditions to form phenolic monomers dissolved in the solvent: isolating the phenolic monomers; and recovering the solvent for reutilization.

[0007] In one embodiment, the method further comprises recovering the catalyst for reutilization.

[0008] In one aspect, the catalyst is nickel on activated carbon. In another aspect, the solvent is MeOH. In yet another aspect, the supercritical conditions comprise a temperature of about 160°C to about 300°C and a pressure of about 30 bar to about 200 bar. In another aspect, the temperature is about 240°C to about 300°C. In another aspect, the temperature is about 300°C.

[0009] In one embodiment, the present disclosure relates to a method of depolymerizing lignin from biomass comprising: catalytically fractioning the lignin from biomass using a reaction containing a catalyst and solvent at a defined reaction temperature over a defined amount of time.

[0010] In one aspect, the biomass is saw dust or com stover. In another aspect, the catalyst is nickel on activated carbon. In yet another aspect, the solvent is MeOH.

[0011] In one aspect, the defined reaction temperature provides sufficient energy' to overcome a calculated activation energy' barrier of the depolymerization reaction. In another aspect, the calculated activation energy barrier is between about 50 kJ / mol and about 65 kJ / mol. In yet another aspect, when the biomass is saw dust, the calculated activation energy barrier is about 54 kJ / mol. In another aspect, when the biomass is com stover, the calculated activation energy barrier is about 62 kJ / mol. In yet another aspect, when the biomass is saw dust, the calculated activation energy barrier is about 54 kJ / mol and the defined reaction temperature is 300°C. In another aspect, when the biomass is com stover, the calculated activation energy barrier is about 62 kJ / mol and the defined reaction temperature is 300°C.

[0012] In another aspect, the defined amount of time is 3 hours.

[0013] In one embodiment, the present disclosure relates to a method of producing phenolic monomers comprising:providing a biomass from saw dust or com stover; extracting lignin from the biomass in solvent phase; depolymerizing the lignin by catalytic fractionation utilizing a catalyst and solvent under supercritical conditions to form phenolic monomers dissolved in the solvent; isolating the phenolic monomers; and recovering the solvent for reutilization.

[0014] In one aspect, the method further comprises recovering the catalyst for reutilization.

[0015] In one aspect, the catalyst is nickel on activated carbon. In another aspect, the solvent is MeOH. In another aspect, the supercritical conditions comprise a temperature of about 160°C to about 300°C and a pressure of about 30 bar to about 200 bar. In yet another aspect, the temperature is 300°C.

[0016] In one aspect, the depolymerizing of lignin produces at least 30 unique phenolic monomers. In yet another aspect, the phenolic monomers are selected from propanoic acid, phenol, o-cresol, m-cresol, guaniacol, 2-ethylphenol, 1,2-dimethoxy benzene, 2 -methoxy - 6methylphenol, catetchol, 2-methoxy-4methylphenol, 3,4-dimethoxytoluene, 3- methylcathecol, 2-methoxyresorcinol. 4-ethyl-2-methoxyphenol. 2-(2-methoxyethyl) phenol. 1,2,3-trimethoxybenzene, 2,6-dimethoxy phenol, hydroethidine (DHE), 2,5-dimethoxy-4- methyl phenol, 4,5-dimethylbenzene-I,2-diol, vanillin, cis-isoeugenol, trans-isoeugenol, acetovanillon, methyl isoeugenol, homovanillyl alcohol, syringaldehyde, 3-(4-Hydroxy-3- methoxyphenyl)-! -propanol,, homovanillic acid, coniferyl alcohol, 2.4 dimethoxy-6-methyl benzoic acid, or a combination thereof.

[0017] In one embodiment, the present disclosure relates to a method of depolymerizing the lignin from biomass, the method comprising: providing biomass from saw dust or com stover; subjecting the biomass to catalytic fractionation reactions utilizing a solvent under supercritical conditions leading to the fragmentation of native lignin from the biomass into phenolic monomers dissolved in the solvent forming a solution of fragmented native lignin in the solvent; separating the fragmented lignin from the solution; and recovering the solvent for reutilization.

[0018] One hinderance to the efficient utilization and valorization of lignin is that the phenolic monomers in depolymerized lignin are not fully identified, and there are not enoughkinetic models that explain the lignin depolymerization reaction. A need exists for a clean method of catalytically converting sawdust and com stover lignin into phenolic monomers.

[0019] The present disclosure includes the identification of phenolic monomers for use in value-added products and conditions for temperature dependent yields of lignin and sugar. Methodologies for the enhancement phenolic monomer production using lignin extraction and depolymerization under supercritical conditions are also disclosed.

[0020] Each embodiment and aspect may be combined into new embodiments or aspects. Combinations of features that are suggested or implied in the disclosure should be considered additional embodiments or aspects.BRIEF DESCRIPTION OF THE FIGURES

[0021] Figure 1 is a schematic showing the process for lignin depolymerization (Figure 1 A) and a schematic showing the process for the mass balance analysis (Figure 1 B).

[0022] Figure 2 are plots showing the total lignin yield from saw dust (Figure 2A) and com stover (Figure 2B) over temperatures ranging from 160°C - 300°C.

[0023] Figure 3 shows the extracted lignin phase composition of saw dust (Figure 3A) and com stover (Figure 3B) over temperatures ranging from 160°C - 300°C.

[0024] Figure 4 are plots showing the total lignin yield from saw dust (Figure 2A) and com stover (Figure 2B) over temperatures ranging from 160°C - 300°C using GC-FID analysis.

[0025] Figure 5 shows the phenolic monomers in the lignin phase of saw dust (Figure 5A) and com stover (Figure 5B) over temperatures ranging from 160°C - 300°C using GC-FID analysis.

[0026] Figure 6 shows the kinetic parameter calculations for saw dust (Figure 6A) and com stover (Figure 6B).

[0027] Figure 7 shows the grouped yield plots for saw dust (Figure 7A) and com stover (Figure 7B).

[0028] Figure 8 shows the Delplot for the first rank grouped monomers (Figure 8A) and the second rank grouped monomers (Figure 8B).

[0029] Figure 9 is the reaction rate model and equations (Figure 9A) with the calculated and experimental results and model fit for saw dust lignin (Figure 9B) and the calculated and experimental results and model fit for com stover lignin (Figure 9C).DETAILED DESCRIPTION OF THE DISCLOSURE

[0030] Described herein are methodologies for the catalytic conversion of lignin derived from sawdust and com stover biomass into phenolic monomers and the temperature dependency on the total yield of lignin and sugars and followed by calculation of reaction kinetic parameters.Definitions

[0031] The following definitions are meant to clarify, but not limit, the terms defined. If a particular term used herein is not specifically defined, such term should not be considered indefinite. Rather, terms are used within their accepted meanings.

[0032] As used herein, the term “about” includes a variation of reasonable degree to allow flexibility around a numerical value or range. In one aspect, the term “about” may provide a number that is below or above based on the significant digit of the stated value or range. In one aspect, the term “about” may provide a number that is below or above based on the accepted limitation of accuracy for the instrument used to measure the stated value or range.

[0033] As used herein, the term "biomass" includes but is not limited to, plant processing waste, soft wood chips, hard wood chips, wheat straw, com stover, rice straw, hay. sugar cane bagasse or other suitable agricultural material containing a significant amount of lignin.

[0034] In some embodiments, the biomass is com stover. Com stover has a higher percentage of [3-0-4 linkages, which makes it more prone to depolymerization. In some embodiments, the biomass is sawdust, which is richer in guaiacyl (G) units that add to its resistance to depolymerization.

[0035] As used herein, the term “supercritical” refers to conditions at which a chemical reaction is in a supercritical fluid (SCF) state meaning that a substance is at a temperature and pressure above its critical point, where it has properties of both a liquid and a gas.

[0036] The term “value-added products” as used herein refers to products that have a commercial, scientific, nutritional and / or economical purpose. Value-added products are compounds or compositions that have been modified or enhanced through processing or other means to increase its market value, often exceeding the cost of its constituent components.Depolymerization of Lignin

[0037] The present disclosure relates to a method of depolymerizing lignin from biomass, the method comprising:(i) providing biomass from saw dust or com stover;(ii) extracting the lignin from the biomass in solvent phase;(iii) depolymerizing the lignin by catalytic fractionation utilizing a catalyst and solvent under supercritical conditions to form phenolic monomers dissolved in the solvent;(iv) isolating the phenolic monomers; and(v) recovering the solvent for reutilization.

[0038] The disclosed methods improve the economic gain and ecological impact of the depolymerization of lignin by recovering the solvent used without need for further purification. The solvent can be reutihzed in repeated depolymerization reactions. In some embodiments, the solvent recovery is greater than 80%, greater than 90%, greater than 95%, greater than 98%, greater than 99%.

[0039] Organic solvents like methanol act as both a solvent and a hydrogen donor, making a solvent significant to the depolymerization reaction. In some embodiments, the solvent is selected from ethylene glycol, acetone, toluene, ethanol (EtOH), methanol (MeOH), or a combination thereof. In some embodiments, the solvent is ethylene glycol. In some embodiments, the solvent is ethanol (EtOH). In some embodiments, the solvent is methanol (MeOH). The solvent used in the present disclosure may be anhydrous. In some embodiments, the solvent is substantially pure, which is intended to describe a solvent substantially free from contaminants or impurities. A minimum purity may be 95%. The solvent used in the process of the present disclosure may be recycled and reused, without substantial impact to purity.

[0040] The methods disclosed herein use the supercritical point of the solvent to depolymerize lignin. The critical point of a substance or composition is dependent on both temperature and pressure. Moreover, higher temperatures have been shown to improve yield. The solvent used in the methods disclosed herein, are selected with the economic and financial considerations related to energy consumption such that the supercritical point may be achieved without high energy input. In some embodiments, the supercritical conditions comprise a temperature of about 160°C to about 300°C and a pressure of about 30 bar to about 200 bar. In some embodiments, the supercritical conditions comprise a temperature of about 160°C, about 170°C, about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C, about 260°C, about 270°C, about 280°C, about 290°C, or about 300°C and a pressure of about 30 bar. about 40 bar, about 50 bar, about 60 bar, about 70 bar. about 80 bar, about 90 bar, about 100 bar, about 110 bar, about 120 bar, about 130 bar, about 140 bar, about 150 bar, about 160 bar, about 170 bar, about 180 bar, about 190 bar, or about 200 bar. In some embodiments, the temperature is 200°C and the pressure is 200 bar. In some embodiments, the temperature is 240°C and the pressure is 200 bar. In some embodiments, thetemperature is 260°C and the pressure is 200 bar. In some embodiments, the temperature is 280°C and the pressure is 200 bar. In some embodiments, the temperature is 300°C and the pressure is 200 bar.

[0041] Additionally, the disclosed methods improve the economic gain and ecological impact of the depolymerization of lignin by recovering the catalyst used. In some embodiments, the method further comprises recovering the catalyst for reutilization.

[0042] Metal-supported catalysts — such as cobalt, nickel, and molybdenum — have shown enhanced depolymerized rates and increased phenolic monomer yields. The catalyst of the present disclosure may be any suitable metal on a carbon support, including but not limited to nickel, palladium, platinum, ruthenium, gold, cobalt, iron, molybdenum, and any other suitable material. In some embodiments, the catalyst is platinum on activated carbon. In some embodiments, the catalyst is palladium on activated carbon. In some embodiments, the catalyst is nickel on activated carbon. In some embodiments, the catalyst is substantially pure, which is intended to describe a catalyst substantially free from contaminants or impurities. A minimum purity may be 95%. The catalyst used in the process of the present disclosure may be recycled and reused, without substantial impact to purity.

[0043] In some embodiments, the present disclosure relates to a method of depolymerizing lignin from biomass comprising: catalytically fractioning the lignin from biomass using a reaction containing a catalyst and solvent at a defined reaction temperature over a defined amount of time.

[0044] In some embodiments, the biomass is saw dust or com stover. In some embodiments, the biomass is saw dust. In some embodiments, the biomass is com stover.

[0045] In some embodiments, the catalyst is selected from platinum on activated carbon, palladium on activated carbon, or nickel on activated carbon. In some embodiments, the catalyst is platinum on activated carbon. In some embodiments, the catalyst is palladium on activated carbon. In some embodiments, the catalyst is nickel on activated carbon.

[0046] In some embodiments, the solvent is selected from ethylene glycol, ethanol (EtOH), methanol (MeOH), or a combination thereof. In some embodiments, the solvent is ethylene glycol. In some embodiments, the solvent is ethanol (EtOH). In some embodiments, the solvent is methanol (MeOH). The solvent used in the present disclosure may be anhydrous.

[0047] One enhancement to the process of depolymerizing lignin is to defined reaction conditions to yield the highest product with the lowest input through the use of the reaction kinetics in development of the methodology. Kinetic analysis has shown that activationenergies can vary' widely, indicating that the efficiency of depolymerization depends heavily on the biomass ty pe and method used. In some embodiments, the defined reaction temperature provides sufficient energy to overcome a calculated activation energy’ barrier of the depolymerization reaction. In some embodiments, the calculated activation energy barrier is between about 50 kJ / mol and about 65 kJ / mol. In some embodiments, the calculated activation energy barrier is about 50 kJ / mol, about 51 kJ / mol, about 52 kJ / mol, about 53 kJ / mol, about 54 kJ / mol. about 55 kJ / mol, about 56 kJ / mol, about 57 kJ / mol, about 58 kJ / mol, about 59 kJ / mol, about 60 kJ / mol, about 61 kJ / mol, about 62 kJ / mol, about 63 kJ / mol, about 64 kJ / mol and about 65 kJ / mol. In some embodiments, the calculated activation energy barrier is 53 kJ / mol. In some embodiments, the calculated activation energy barrier is about 54 kJ / mol. In some embodiments, the calculated activation energy barrier is about 61 kJ / mol. In some embodiments, the calculated activation energy barrier is about 62 kJ / mol. In some embodiments, the calculated activation energy barrier is about 63 kJ / mol.

[0048] In some embodiments, when the biomass is saw dust, the calculated activation energy barrier is about 54 kJ / mol. In some embodiments, when the biomass is com stover, the calculated activation energy barrier is about 62 kJ / mol.

[0049] In some embodiments, when the biomass is saw dust, the calculated activation energy barrier is about 54 kJ / mol and the defined reaction temperature is 300°C. In some embodiments, when the biomass is com stover, the calculated activation energy barrier is about 62 kJ / mol and the defined reaction temperature is 300°C.

[0050] In some embodiments, the defined amount of time is about 0.5 to about 3 hours. In some embodiments, the defined amount of time is about 0.5, about 0.75, about 1.0, about 1.25, about 1.5, about 1.75, about 2.0 about 2.25. about 2.5, about 2.75, or about 3 hours. In some embodiments, the defined amount of time is about 3 hours.

[0051] The present disclosure also relates to a method of producing phenolic monomers comprising: providing a biomass from saw dust or com stover; extracting lignin from the biomass; depolymerizing the lignin by catalytic fractionation utilizing a catalyst and solvent under supercritical conditions to form phenolic monomers dissolved in the solvent; isolating the phenolic monomers; and recovering the solvent for reutilization.

[0052] In some embodiments, the method further comprises recovering the catalyst for reuse.

[0053] In some embodiments, the catalyst is selected from platinum on activated carbon, palladium on activated carbon, or nickel on activated carbon. In some embodiments, the catalyst is platinum on activated carbon. In some embodiments, the catalyst is palladium on activated carbon. In some embodiments, the catalyst is nickel on activated carbon.

[0054] In some embodiments, the solvent is selected from ethylene glycol, ethanol (EtOH). methanol (MeOH), or a combination thereof. In some embodiments, the solvent is ethylene glycol. In some embodiments, the solvent is ethanol (EtOH). In some embodiments, the solvent is methanol (MeOH). The solvent used in the present disclosure may be anhydrous.

[0055] In some embodiments, the supercritical conditions comprise a temperature of about 160°C to about 300°C and a pressure of about 30 bar to about 200 bar. In some embodiments, the supercritical conditions comprise a temperature of about 160°C, about 170°C, about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C, about 260°C. about 270°C, about 280°C, about 290°C, or about 300°C and a pressure of about 30 bar, about 40 bar, about 50 bar, about 60 bar. about 70 bar. about 80 bar. about 90 bar, about 100 bar, about 110 bar, about 120 bar, about 130 bar, about 140 bar, about 150 bar, about 160 bar, about 170 bar, about 180 bar, about 190 bar, or about 200 bar. In some embodiments, the temperature is 200°C and the pressure is 200 bar. In some embodiments, the temperature is 240°C and the pressure is 200 bar. In some embodiments, the temperature is 260°C and the pressure is 200 bar. In some embodiments, the temperature is 280°C and the pressure is 200 bar. In some embodiments, the temperature is 300°C and the pressure is 200 bar.

[0056] The present disclosure provides methods to produce phenolic monomers. Furthermore, the production of specific monomers can be tailored based on the depolymerization reactions conditions, such as temperature. In some embodiments, the depolymerization of lignin produces between at least 5 phenolic monomers and at least 50 phenolic monomers. In some embodiments, the depolymerization of lignin produces at least 5, at least 10. at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, or at least 50 phenolic monomers. In some embodiments, at least 30 unique phenolic monomers are produced. In some embodiments, at least 31 unique phenolic monomers are produced. In some embodiments, at least 40 unique phenolic monomers are produced. In some embodiments, at least 41 unique phenolic monomers are produced.

[0057] In some embodiments, the phenolic monomers are selected from propanoic acid, phenol, o-cresol, m-cresol, guaniacol, 2-ethylphenol, 1,2-dimethoxy benzene. 2 -methoxy - 6methylphenol, catetchol, 2-methoxy-4methylphenol, 3,4-dimethoxytoluene, 3- methylcathecol, 2-methoxyresorcinol, 4-ethyl-2-methoxyphenol, 2-(2-methoxyethyl) phenol, 1,2,3-trimethoxybenzene, 2,6-dimethoxy phenol, hydroethidine (DHE), :2,5-dimethoxy-4- methyl phenol, 4,5-dimethylbenzene-l,2-diol, vanillin, cis-isoeugenol. trans-isoeugenol, acetovanillon, methyl isoeugenol, homovanillyl alcohol, syringaldehyde. (DHEOH). homovanillic acid, coniferyl alcohol, 2,4 dimethoxy-6-methyl benzoic acid, or a combination thereof. Any grouping or selections of these monomers are considered an embodiment of the disclosure. Preferred monomeric characterizations may be the basis for selections of embodiments of the disclosure.

[0058] In some embodiments, the phenolic monomers are methoxyphenols. Methoxyphenols include but are not limited to guaniacol, 1 ,2-dimethoxy benzene, 2-methoxy- 6methylphenol, 2-methoxy-4methylphenol, 3.4-dimethoxytoluene, 4-ethyl-2-methoxyphenol, 2-(2-methoxyethyl) phenol, 1,2,3-trimethoxybenzene, 2,6-dimethoxy phenol, 2,5-dimethoxy- 4-methyl phenol, vanillin, cis-isoeugenol. trans-isoeugenol. acetovanillon, methyl isoeugenol, homovanillyl alcohol, syringaldehyde, 3-(4-hydroxy-3-methoxyphenyl)-l-propanol, homovanillic acid, coniferyl alcohol, 2,4 dimethoxy-6-methyl benzoic acid, or a combination thereof.

[0059] In some embodiments, the phenolic monomers are catechols. Catechols include but are not limited to catechol, 3-methylcatechol, or a combination thereof.

[0060] In some embodiments, the phenolic monomers are phenols. Phenols include but are not limited to phenol, o-cresol, m-cresol, 2-ethylphenol, dihydroeugenol, 4,5- dimethylbenzene-l,2-diol, or a combination thereof.

[0061] The use of the phenolic monomers from the disclosed methods may be in a variety of downstream products including but not limited to epoxies, polyurethanes, UV inhibitors, antimicrobials, polyphenols for sun damage repair compositions, and anti-aging creams or compositions. Any use of phenolic monomers from the disclosed methods as an ingredient or starting material for a commercial product are contemplated herein.

[0062] The present disclosure also relates to a method of depolymerizing the lignin from biomass, the method comprising: providing biomass from saw dust or com stover;subjecting the biomass to catalytic fractionation reactions utilizing a solvent under supercritical conditions leading to the fragmentation of native lignin from the biomass into phenolic monomers dissolved in the solvent forming a solution of fragmented native lignin in the solvent; separating the fragmented lignin from the solution; and recovering the solvent for reutilization.EXAMPLESExample 1: Analysis of Products from Lignin Depolymerization of Saw Dust or Corn Stover Biomass

[0063] Biomass was analyzed to determine the total percentages of cellulose, hemicellulose, lignin, inorganics, and wax using NREL procedures. A 100 ml batch Parr Reactor was used to run the reactions with temperatures ranging from 160°C-300°C and pressure ranging from 30-200 bar. A nickel on activated carbon catalyst was prepared using an incipient impregnation method with 11% metal loading. Methanol was used as a solvent and reactions were conducted at a supercritical temperature and pressure. See Figure 1A for process. The output of the reactor was analyzed for the (i) percentage of lignin extracted from the available lignin using Mass Balance analysis (Figure 2), (ii) the concentration of lignin in the cellulose fraction, (iii) the amount of cellulose, hemicellulose, and sugars in the depolymerized lignin fraction (Figure 3), and (iv) weight percentage of phenolic components in the depolymerized lignin sample using GC-FID analysis (Figures 4 and 5).Compositional Analysis of Sawdust and Corn Stover

[0064] The compositional differences between pine sawdust and com stover were analyzed (Tables 1 and 2). Sawdust has a higher lignin content, whereas com stover contains more ash. These variations in composition are important because they influence how each biomass responds to depolymerization and ultimately affect the yield of phenolic monomers. Understanding the composition allows us to anticipate potential challenges, such as handling the high ash content in com stover, which could interfere with catalyst performance.Table 1: Compositional AnalysisTable 2: Elemental AnalysisMass Balance Analysis

[0065] In the process, the slurry is separated into liquid and solid streams (Figure IB).

[0066] For the liquid stream, after filtration, methanol is evaporated from the liquid to concentrate the sample. Sulfuric acid is then added, forming lignin, oil, and aqueous layers. Each layer is isolated, weighed, and analyzed. Lignin and oil content are further studied through drying, weighing, and GC / MS analysis to identify chemical components.

[0067] The solid portion, mostly fibers, and residual catalysts, undergoes magnetic separation to recover the catalyst. The remaining fibers are then treated to determine lignin, cellulose, and hemicellulose content.

[0068] A mass balance is maintained throughout, ensuring accurate quantification of all components.Yield and Compositional Analysis of Lignin

[0069] The reactions were run for 3 hours, obtaining the maximum yield. Using mass balance analysis, the total extracted lignin was calculated. The yield increases significantly after reaching 240°C, where methanol acts as a supercritical fluid. Sawdust lignin shows a high conversion rate of 95% (Figure 2A). The compositional analysis at different temperatures provides detailed masses of lignin, degraded sugars, extractives, and any residual catalyst in the sample. As the temperature rises from 160°C to 300°C, sugar content decreases, with lignin making up as much as 90% of the sample (Figure 3A). Above 300°C, the amount of extracted lignin only varies by 0.3-0.5%, but the amount of depolymerized phenolic lignin decreases significantly. At 350°C, the depolymerized amount decreases to 60.6% and at 400°C it wasestimated to be 48.8%. This is primarily due to recondensation of monomers to larger oligomeric fraction along with char formation.

[0070] A similar trend is observed with com stover lignin, reaching a 92% conversion at 300°C (Figure 2B). However, its compositional analysis differs notably; even at higher temperatures, sugars account for 40% of the sample’s total weight. Additionally, due to com stover's naturally higher inorganic content, about 15% of these inorganics transfer into the lignin sample (Figure 3B). At 350°C, the depolymerized amount decreases to 54% and at 400°C it was estimated to be 41.1%.Kinetic Model based on Mass Balance

[0071] A basic kinetic model using lignin yield data at various temperatures and time intervals from 1 to 7 hours was used for calculations. This gave the reaction order and rates at each temperature. From these results, the Arrhenius parameters were determined, including activation energy' and pre-exponential factors. The activation energy was 54 kJ / mol (Preexponential Factor (A): 200.1918 s'1, R2: 0.9220) for sawdust (Figure 6A) and 62 kJ / mol (Preexponential Factor (A): 2003.5201 s'1, R2: 0.9740) for com stover (Figure 6B). Due to the protective sheath in agricultural straws, a higher activation energy for com stover expected.Yield Percentage of Depolymerized Lignin as Phenolic Monomers using GC-FID Analysis

[0072] The yield percentages of depolymerized lignin were calculated by quantifying the weights of phenolic monomers. Using GC-FID analysis, around 30 phenolic monomers were identified and with their individual yields. These monomers were grouped into three categories — methoxyphenols, catechols, and phenols. Through delplot analysis, each product was classified as either primary or secondary based on its reaction pathway, revealing which monomers are directly produced and which arise from subsequent transformations. From this, a generalized kinetic model was formulated with corresponding rate equations. The calculated and experimental values were compared to assess the model’s accuracy using the kinetic parameters.

[0073] Figure 4A shows the yields of depolymerized lignin calculated using the GC-FID concentration of each phenolic monomer. At 300C. around 92 and 90% of lignin sample composed of phenolic monomers for sawdust and com stover respectively.

[0074] The stacked graph in Figures 5A and 5B display the identified phenolics and unknown products obtained via GC-FID after a 3 -hour run-time. For sawdust (SD), guaiacol, catechol, 4-ethyguaiacol, and isoeugenol collectively account for 55% of the total weight. Incontrast, for com stover (CS), catechol and guaiacol contribute about 30% of the weight, with other compounds distributed more evenly across the remainder.

[0075] With saw dust, the sinapyl or S units are known to produce more syringyl-type monomers like syringaldehyde and catechol. The higher yields of catechol and other S-type monomers from sawdust indicate its suitability for producing these valuable compounds. With com stover, guaiacol yields peak at 200°C and remain significant at higher temperatures. This aligns with the lignin structure of com stover, which is nch in guaiacyl units. Additionally, com stover has a more complex matrix than sawdust, making lignin more recalcitrant to extraction, thereby increasing the activation energy required.Reaction Kinetic Model

[0076] Figure 7A presents the yield data for grouped phenolics obtained from saw dust biomass at 300°C. In the top left graph, we see the yield trend for methoxyphenols, which increases until reaching a peak at 3 hours, after which it steeply decreases. Catechols display a slower initial rise, followed by a steady increase after 2-3 hours. For phenols, yield growth becomes more pronounced after 3 hours. The bottom right graph shows the averaged methoxyphenol yields at various temperatures; as temperature decreases, the peak yield occurs at later time points.

[0077] A similar trend is observed for com stover (CS) grouped phenolics (Figure 7B). In the phenols group, 4.5-dimethylbenzene-l,2-diol exhibits an unusual pattern that remains unexplained. The peak in methoxyphenols occurs at 3, 4, and 6 hours for 300°C, 280°C, and 260°C, respectively, while no peak is observed at 240°C.Primary and Secondary Reaction Products

[0078] The primary and secondary reaction products were evaluated by looking at conversion percentages and product yields. Figure 8 A shows the 1st rank Delplot for the grouped monomers. 100% conversion is taken for the highest yield. Methoxyphenols are i dent i Tied as primary products due to their finite intercepts, which means they form early in the reaction. In contrast, catechols have a zero intercept, indicating that they are secondary products, forming from the decomposition of methoxyphenols. Understanding this hierarchy of reaction products provides valuable insight into optimizing reaction conditions to maximize desired monomer y ields.

[0079] Further analysis reveals the dynamics of secondary reactions (Figure 8B) as all intercepts are finite here and thus categorizing catechols as secondary products. Catechols showa stronger secondary product tendency, which could mean they are intermediate products, while phenols can either directly form from lignin or result from catechol decomposition. Competing and parallel reactions must be expected, but the analysis performed here is restricted to identification and description of the major pathways at given reaction conditions, while still recognizing that further reactions exist.Reaction Kinetics and Rate Constants

[0080] To understand the underlying mechanisms, kinetic modeling was applied to derive rate constants and reaction orders for the reactions (Figure 9). This differential equation system captures how lignin transforms into methoxyphenols, which then decompose into catechols and phenols. Phenols can either directly form from lignin or result from catechol decomposition. By calculating rate constants such as ki, k2, and ks. each reaction pathway could be quantified, offering insight into the sensitivity of these reactions to factors like temperature and concentration.

[0081] The analysis yielded R2values to assess the accuracy of the kinetic models in predicting experimental results (Figures 16 and 17). For sawdust (SD), the model's fit for methoxyphenols remains suboptimal, likely due to unmodeled side reactions or catalytic effects that increase experimental yields. For instance, trace minerals or residual catalysts in the biomass may enhance methoxyphenols production. Additionally, if intermediate compounds or alternate reaction pathways contribute to methoxyphenols formation but aren't included in the model, calculated yields may fall short. In the case of com stover (CS), the model predicts a peak in methoxyphenols at 2 hours. However, in experimental setups, mass transfer limitations, such as diffusion constraints within the biomass, can delay methoxyphenols release and accumulation — factors not accounted for in the model.

[0082] Table 3 shows the summary of the calculated kinetic parameters for sawdust and com stover biomass. The rate constant ki for methoxyphenol production is significantly higher for com stover than for sawdust, indicating easier breakdown. Both biomasses show a fast decomposition of MPH. Additionally, sawdust lignin is more inclined to directly form phenols, whereas com stover demonstrates stronger reversibility, suggesting a dynamic equilibrium in phenol formation. The reaction orders a, b, c, and d provide further insight into each biomass's sensitivity to concentration, highlighting the contrasting behavior of these biomasses under similar conditions.Table 3: Rate Parameters for Sawdust and Corn StoverNote: SD: Sawdust; CS: Com Stover; SDL: SD lignin; CSL: CS lignin; MPH: Methoxyphenol;CT: Catechol; PH: PhenolConclusion

[0083] The high conversion rates achieved significant lignin conversion for both sawdust (95%) and com stover (92%) at elevated temperatures, highlighting effective extraction. The temperature impacted methanol’s role as a supercritical fluid with boosted yields above 240°C, with sawdust and com stover showing distinct compositional responses to temperature. The simplified representation of lumped model groups for complex reactions into a few generalized steps, makes it easier to analyze and interpret the reaction dynamics. This approach can be applied across different biomass types (e.g., sawdust, com stover) by adjusting rate constants, making it flexible for comparative studies. The model may underpredict the maximum yield of methoxyphenols, indicating that additional factors or reaction pathways might be missing. The lumped model assumes homogeneity and ideal mixing, potentially overlooking mass transfer limitations or local concentration effects that are present in real biomass matrices.

[0084] The present disclosure enables one of skill in the relevant art to make and use the inventions provided herein in accordance with multiple and varied embodiments. Various alterations, modifications, and improvements of the present disclosure that readily occur to those skilled in the art, including certain alterations, modifications, substitutions, andimprovements are also part of this disclosure. Accordingly, the foregoing description are by way of example to illustrate the discoveries provided herein. Furthermore, the foregoing Description and Examples are exemplary of the present invention and not limiting thereof. The scope of the invention is therefore set out in the appended claims.

[0085] Although specific embodiments of the present disclosure are herein illustrated and described in detail, the disclosure is not limited thereto. The above detailed descriptions are provided as exemplary of the present disclosure and should not be construed as constituting any limitation of the disclosure. Modifications will be obvious to those skilled in the art, and all modifications that do not depart from the spirit of the disclosure are intended to be included with the scope of the appended claims.

Claims

CLAIMS1. A method of depolymerizing lignin from biomass, the method comprising:(i) providing biomass from saw dust or com stover;(ii) extracting the lignin from the biomass in solvent phase;(iii) depolymerizing the lignin by catalytic fractionation using a catalyst and solvent under supercritical conditions to form phenolic monomers dissolved in the solvent;(iv) isolating the phenolic monomers; and(v) recovering the solvent for reuse.

2. The method of claim 1, further comprising:(vi) recovering the catalyst for reuse.

2. The method of claim 1 or 2, wherein the catalyst is nickel on activated carbon.

3. The method of any of claims 1 to 3, wherein the solvent is MeOH.

4. The method of any of claims 1 to 4, wherein the supercritical conditions comprise a temperature of about 160°C to about 300°C and a pressure of about 30 bar to about 200 bar.

5. The method of claim 5, wherein the temperature is about 240°C to about 300°C.

6. The method of claim 5, wherein the temperature is 300°C.

7. A method of depolymerizing lignin from biomass comprising: catalytically fractioning the lignin from biomass using a reaction containing a catalyst and solvent at a defined reaction temperature over a defined amount of time.

8. The method of claim 7, wherein the biomass is saw dust or com stover.

9. The method of claim 7 or 8, wherein the catalyst is nickel on activated carbon.

10. The method of any of claims 7 to 9, wherein the solvent is MeOH.

11. The method of any of claims 7 to 10, wherein the defined reaction temperature provides sufficient energy to overcome a calculated activation energy barrier of the depolymerization reaction.

12. The method of claim 11, wherein the calculated activation energy barrier is between about 50 kJ / mol and about 65 kJ / mol.

13. The method of claim 11, wherein when the biomass is saw dust, the calculated activation energy barrier is about 54 kJ / mol.

14. The method of claim 11, wherein when the biomass is com stover, the calculated activation energy' barrier is about 62 kJ / mol.

15. The method of claim 11 or 12, wherein when the biomass is saw dust, the calculated activation energy7barrier is about 54 kJ / mol and the defined reaction temperature is 300°C.

16. The method of claim 11 or 12, wherein when the biomass is com stover, the calculated activation energy barrier is about 62 kJ / mol and the defined reaction temperature is 300°C.

17. The method of any of claims 7 to 16, wherein the defined amount of time is 3 hours.

18. A method of producing phenolic monomers comprising:(i) providing a biomass from saw dust or com stover;(ii) extracting lignin from the biomass;(iii) depolymerizing the lignin by catalytic fractionation using a catalyst and solvent under supercritical conditions to form phenolic monomers dissolved in the solvent;(iv) isolating the phenolic monomers: and(v) recovering the solvent for reuse.

19. The method of claim 18, further comprising:(vi) recovering the catalyst for reuse.

20. The method of claim 18 or 19, wherein the catalyst is nickel on activated carbon.

21. The method of any of claims 18 to 20. wherein the solvent is MeOH.

22. The method of any of claims 18 to 21, wherein the supercritical conditions comprise a temperature of about 160°C to about 300°C and a pressure of about 30 bar to about 200 bar.

23. The method of claim 22, wherein the temperature is 300°C.

24. The method of any of claims 18 to 23. wherein the depolymerizing of lignin produces at least 30 unique phenolic monomers.

25. The method of any of claims 18 to 24, wherein the phenolic monomers are selected from propanoic acid, phenol, o-cresol, m-cresol, guaniacol, 2-ethylphenol, 1,2- dimethoxy benzene, 2-methoxy-6methylphenol, catetchol. 2-methoxy-4methylphenol, 3,4- dimethoxytoluene, 3-methylcathecoL 2-methoxyresorcinol, 4-ethyl-2-methoxyphenol, 2-(2- methoxy ethyl) phenol, 1,2, 3 -trimethoxy benzene, 2,6-dimethoxy phenol, hydroethidine (DHE), 2,5-dimethoxy-4-methyl phenol, 4,5-dimethylbenzene-l,2-diol, vanillin, cis-isoeugenol, transisoeugenol, acetovanillon, methyl isoeugenol, homovanillyl alcohol, syringaldehyde, 3-(4- Hydroxy-3-methoxyphenyl)-l-propanol, homovanillic acid, coniferyl alcohol, 2.4 dimethoxy- 6-methyl benzoic acid, or a combination thereof.

26. A method of depolymerizing the lignin from biomass, the method comprising:(i) providing biomass from saw dust or com stover;(ii) subjecting the biomass to catalytic fractionation reactions utilizing a solvent under supercritical conditions leading to the fragmentation of native lignin from the biomass into phenolic monomers dissolved in the solvent forming a solution of fragmented native lignin in the solvent;(iii) separating the fragmented lignin from the solution; and(iv) recovering the solvent for reutilization.

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