Continuous hydrodeoxygenation of lignin to produce aromatic hydrocarbons for jet fuel.

Abstract

Described herein are systems and methods for the catalytic deoxygenation of lignin to produce low-oxygen aromatic compounds useful as sustainable aviation or marine fuels. The provided systems and methods can be performed continuously without the need for solvents, improving both efficiency and cost-effectiveness.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 395,067, filed August 4, 2022, the contents of which are incorporated herein by reference in their entirety.

[0002] (Contractual Origin) This invention was made with government support under Contract No. DE-AC36-08GO28308 awarded by the Department of Energy. The government has certain rights in this invention. [Background technology]

[0003] In 2019, 106 billion gallons of jet fuel were consumed worldwide, and this amount is expected to more than double by 2050 due to increasing travel demand. To mitigate the impact of climate change, the aviation industry has committed to halving its net CO2 emissions by 2050. Achieving this goal requires the large-scale deployment of sustainable aviation fuel (SAF). Currently, most commercially available SAF is produced synthetically by deoxygenating plant-derived lipid feedstocks to produce a mixture of iso- and n-alkane hydrocarbons. However, these feedstocks are not available in the quantities required to meet projected fuel demand. Notably, cycloalkanes and aromatics together account for 30–70% by weight of modern aviation fuel, amounting to 32–74 billion gallons per year. However, current SAF technology is unable to produce aromatic or cycloalkane components at the required scale to meet the jet fuel properties (i.e., fuel density and elastomer compatibility) required to power the existing aircraft fleet. This constraint limits SAF to a 50% blend with conventional fossil fuels. Therefore, technologies to produce aromatics and cycloalkanes from renewable feedstocks are essential for the development of practical 100% drop-in SAF.

[0004] Lignin is the largest source of renewable aromatic compounds available in nature, accounting for 15–30% of lignocellulosic biomass. In principle, the 90 million dry tons of lignin harvested in the United States in 2017 could produce 15 billion gallons of jet fuel hydrocarbons based on their carbon content. Given projections of future lignin supplies, this figure could increase to 63 billion gallons per year by 2040 (more than 50% of current global demand). Despite lignin's great potential, it is highly intractable once separated from the cellulose fibers in biomass. Therefore, in the cellulosic ethanol and paper industries, lignin is currently redistributed in open fields or burned as a low-grade heat source. Alternative lignin extraction methods relying on reductive catalytic fractionation (RCF), protecting group chemistry, or flow-through solvolysis minimize recondensation pathways, but the resulting lignin oils have high oxygen contents (27–34 wt%) that must be reduced to trace levels for use as jet fuel. Toward this end, significant progress has been made in developing catalysts capable of hydrodeoxygenation (HDO) of oxygenated aromatic compounds. However, translating promising catalysts into viable process strategies using real lignin feedstocks has been hindered by significant challenges, including the use of expensive precious metal catalysts, catalyst deactivation due to reduced deoxygenation efficiency when using real feedstocks, excessive hydrogen consumption due to ring hydrogenation and hydrocracking, and reduced carbon yields due to condensation / coking, hydrocracking to gaseous products, or upgrading of only the monomer fraction. Summary of the Invention [Problem to be solved by the invention]

[0005] Described herein are systems and methods for the catalytic deoxygenation of lignin to produce low-oxygen aromatic compounds useful as sustainable aviation or marine fuels. The provided systems and methods can be performed continuously without the need for solvents, improving both efficiency and cost-effectiveness. [Means for solving the problem]

[0006] In one embodiment, a method for producing aromatic compounds from a lignin feedstock is provided using a two-stage process: a first stage at a low temperature and a second stage at a high temperature to completely deoxygenate the lignin while avoiding undesirable secondary reactions such as condensation reactions. This method can utilize a single or multiple catalysts, including, by way of example, a MoC-based catalyst. The low temperature in the first stage can be selected, for example, from the range of 250°C to 450°C, 300°C to 400°C, 325°C to 375°C, 325°C to 350°C, or about 350°C. The higher temperature in the second stage can be selected, for example, from the range of 275°C to 475°C, 325°C to 425°C, 350°C to 400°C, 350°C to 375°C, or about 375°C. The aromatic hydrocarbons produced can have a very low oxygen content, e.g., the mole fraction of oxygen in the compounds produced can be 10% or less, 5% or less, 1% or less, 0.5% or less, or 0.1% or less.

[0007] The method can be carried out using pure lignin oil, e.g., solvent-free lignin. The ability to react pure lignin oil can provide various advantages, such as reduced costs and smaller reactor requirements. However, the described system and method can also be utilized in situations where it is preferable to dissolve the lignin reactant in a solvent, such as an aromatic solvent, e.g., toluene.

[0008] In one aspect, provided is a system or reactor for the production of low-oxygen aromatic compounds, comprising: a first reaction zone including a first catalyst at a first-stage temperature; and a second reaction zone including a second catalyst at a second-stage temperature; wherein the reactor is capable of hydrodeoxygenating lignin to produce aromatic products. The reactor may be a packed-bed reactor or a trickle-bed reactor. The reactor may allow for continuous process flow, either in individual steps (e.g., each step sequentially) or as a single continuous process. The reactor may be capable of steady-state operation.

[0009] Other catalysts, including supported metal catalysts, may be useful as a second, higher temperature catalyst. Furthermore, the described process may be modified to produce cycloalkanes rather than aromatic products. This may be accomplished by incorporating a metal-doped Mo2C-based catalyst or by replacing one or both catalysts with a catalyst comprised of nickel phosphide.

[0010] In one embodiment, a catalyst is provided that is comprised of MoC that is capable of partial or complete deoxygenation of lignin, as described by the systems and methods provided herein. [Brief explanation of the drawings]

[0011] Some embodiments are illustrated in the referenced figures of the drawings. The embodiments and figures disclosed herein are intended to be considered illustrative and not restrictive.

[0012] Figure 1 provides a schematic diagram of the HDO of RCF lignin oil. [Figure 1A] Figure 1A provides an overview of lignin monomers quantified as described herein at all levels of partial conversion. Monomer conversion in one or two passes yields similar results, with propylbenzene as the major product. Darker colors represent the major reaction pathway over MoC, while lighter colors represent products resulting from side reactions, including functional group rearrangements and ring alkylation (products marked with an asterisk). These have been previously observed during molybdenum oxide-catalyzed deoxygenation. Abbreviations are as follows: PS: propyl syringol, PS = propenyl syringol, PS-OH: dihydrosinapyl alcohol, PG: propyl guaiacol, PG = propenyl guaiacol, PG-OH: dihydroconiferyl alcohol, PP: propyl phenol, Alk.PG: methylpropyl guaiacol, Alk.PP: methylpropyl phenol, Rearr.PG: methoxypropyl phenol, PB-OMe: propyl anisole, PB: propyl benzene, PCH: propyl cyclohexane. [Figure 1B] Figure 1B shows examples of dimers identified in the feedstock, intermediates, and products. Dimer conversion is temperature sensitive, and at higher temperatures there is a parallel pathway to condensation products.

[0013] FIG. 2 shows a control experiment without catalyst to evaluate the stability of lignin oil. [Figure 2A] Figure 2A shows the mass balance of steady-state samples taken during a control experiment without catalyst. The bars indicate the mass fractions of monomer and non-monomer, and the product bars are scaled by the overall mass recovery. The bar heights are the average values, and the error bars represent one standard deviation for three steady-state samples. A feed bar is included with each experiment to account for slight variations between batches of RCF oil. [Figure 2B] Figure 2B shows GPC of the feedstock ("RCF oil") and the product obtained from a control experiment without catalyst at different temperatures. The inset shows the dimer and oligomer portions of the curve to highlight the change in product distribution with increasing temperature. All samples were adjusted to the same concentration of 2 mg / mL, and the recordings have not been normalized or scaled.

[0014] Figure 3 shows the activity and stability of Mo2C in solvent-free lignin HDO. Conditions were: 900 psi, 2.88 g Mo2C (60-100 mesh), 90 mL / min hydrogen, and 1 mL / min toluene for 30 min at start-up. [Figure 3A]Figure 3A shows steady-state results for monomer distribution and monomer molar balance in an HDO experiment in which pure RCF lignin oil ("feedstock") was flowed over a 2.88 g MoC (60-100 mesh) packed bed in a trickling-bed reactor. The steady-state results were obtained 2.5 hours into the run and represent several hours of data. Water produced during the reaction was removed before performing mass and molar balance calculations. Each bar indicates the reaction temperature and weight hourly space velocity (WHSV), calculated as the lignin oil mass flow rate divided by the catalyst mass. [Figure 3B] Figure 3B shows the temporal distribution of quantified monomers at 300 °C and 0.1 mL / min of lignin oil (WHSV = 2.35 h-1) as a function of time from start-up. [Figure 3C] Figure 3C shows the temporal distribution of quantified monomers at 325 °C and 0.1 mL / min of lignin oil (WHSV = 2.35 h-1) as a function of time from start-up. [Figure 3D] Figure 3D shows the temporal distribution of quantified monomers at 350 °C and 0.1 mL / min of lignin oil (WHSV = 2.35 h-1) as a function of time from start-up. [Figure 3E] FIG. 3E shows the conversion of oxygen from the monomer fraction for each run shown in FIGS. 3B-3D, plotted as mole percent oxygen removal from the monomer for each run time.

[0015] FIG. 4 shows the optimization of deep deoxygenation of lignin oil for the production of aromatics for jet fuel. [Figure 4A] Figure 4A shows the carbon, oxygen, and hydrogen content of the oil by mass as determined by total carbon analysis. The weight percent results of the total carbon analysis were multiplied by the steady-state mass recovery of the oil after removing the water-soluble fraction to generate the plot. [Figure 4B] FIG. 4B shows the results of quantitative GC×GC analysis of the final deoxygenated oil from each experiment shown in FIG. 4A. [Figure 4C]Figure 4C shows the simulated ASTM D2887 distillation of the fully deoxygenated product from each multi-pass experiment, with the dimer region plotted and expanded. The protocol and conditions are described in the specification. [Figure 4D] Figure 4D shows the production of fully deoxygenated lignin oil using optimized multi-pass conditions. A Sankey diagram shows the carbon balance at each pass stage of the optimized multi-pass experiment. The carbon content of the whole oil was measured by total carbon analysis. The carbon content of the monomer was measured by GC-FID analysis and plotted as a fraction of the total carbon content. The carbon content was multiplied by the steady-state mass recovery of the oil at each pass stage. Photographs show the state of the oil at each stage of the process, with the water formed during the reaction (bottom layer) separating from the deoxygenated organics (top layer). Conditions: 2.88 g Mo2C (60-100 mesh), 0.1 mL / min lignin oil, 90 mL / min hydrogen, 900 psi, first pass at 350 °C, second pass at 375 °C, 1 mL / min toluene for 30 minutes at start-up.

[0016] [Figure 5] FIG. 5 shows an example process for reduced catalytic fractionation as described herein using poplar wood as the lignin source.

[0017] [Figure 6] FIG. 6 shows an example of a hydrodeoxygenation process and an example of a trickling bed reactor.

[0018] [Figure 7] Figure 7 shows examples of cycloalkane and aromatic products obtained from the described process. The colors or gray scales correspond to the graphs shown in Figures 8, 10A, 10B, 12A, and 12B.

[0019] [Figure 8] Figure 8 shows the feedstock composition and monomer / oil ratios of poplar, pine, and corn stover feedstocks, showing that pine has a lower monomer / oil ratio.

[0020] [Figure 9] FIG. 9 shows the GPC-UV chromatography of poplar, pine and corn stover feedstocks.

[0021] [Figure 10A] Figure 10A shows the monomer distribution of pine raw material at 350°C and 400°C for different times.

[0022] [Figure 10B] FIG. 10B shows the carbon, hydrogen, and oxygen content of the pine raw material.

[0023] [Figure 11] FIG. 11 shows the effect of feed ether content on fuel properties, showing that 66% of the product is aromatics within the jet fuel range.

[0024] [Figure 12] FIG. 12 shows the monomer distribution of corn stover feedstock at 350° C. and 400° C. for different times.

[0025] [Figure 13] Figure 13 shows the elemental content of poplar, pine and corn stover feedstocks. Nitrogen and sulfur are attributed to proteins and extractives. DETAILED DESCRIPTION OF THE INVENTION

[0026] The embodiments described herein should not necessarily be construed as limited to addressing the particular problems or deficiencies discussed herein. References herein to "one embodiment," "one embodiment," "exemplary embodiment," "some embodiments," and the like indicate that the described embodiments may include particular features, structures, or characteristics, but not all embodiments necessarily include the particular features, structures, or characteristics. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly stated.

[0027] As used herein, the term "substantially" is used to indicate that an exact value is not necessarily achievable. For example, those skilled in the art will understand that in a chemical reaction, 100% conversion of reactants is possible, but unlikely. The majority of the reactants are converted to products, and the conversion of the reactants may asymptotically approach 100% conversion. That is, from a practical standpoint, 100% of the reactants are converted, but from a technical standpoint, a small, and sometimes difficult to define, amount remains. In this example of a chemical reactant, the amount may be relatively easily defined by the detection limit of the instrument used to analyze it. However, in many cases, this amount may not be easily defined, hence the term "substantially." In some embodiments of the present invention, The term "substantially" is defined as approaching a particular numerical value or target value within 20%, 15%, 10%, 5%, or 1% of that numerical value or target value. In a further embodiment of the present invention, the term "substantially" is defined as approaching a particular numerical value or target value within 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% of that numerical value or target value.

[0028] As used herein, the term "about" is used to indicate that an exact value is not necessarily achievable. Thus, the term "about" is used to indicate this uncertainty limit. In some embodiments of the present invention, the term "about" is used to indicate an uncertainty limit of no more than ±20%, ±15%, ±10%, ±5%, or ±1% of a particular numerical value or target value. In some embodiments of the present invention, the term "about" is used to indicate an uncertainty limit of no more than ±1%, ±0.9%, ±0.8%, ±0.7%, ±0.6%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, or ±0.1% of a particular numerical value or target value.

[0029] As used herein, the terms "MoC" or "MoC-based catalyst" refer to a catalyst that essentially comprises or consists of one form of molybdenum carbide. In some embodiments, the catalyst essentially comprises or consists of MoC or β-MoC, although other forms or phases of molybdenum carbide may also be major or minor components. Additionally, MoC-based catalysts may include metal-doped catalysts in which metals such as transition metals, e.g., Cu, Ni, Pt, are included in the catalyst. MoC-based catalysts may also have multi-dimensional or multi-layered structures.

[0030] The discussion and examples provided are presented for purposes of illustration and description. The foregoing is not intended to limit the aspects, embodiments, or configurations to the forms or structures disclosed herein. In the foregoing detailed description, for example, various features of aspects, embodiments, or configurations are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. Features of aspects, embodiments, or configurations may be combined into alternative aspects, embodiments, or configurations other than those described above. This method of disclosure should not be interpreted as reflecting an intention that an aspect, embodiment, or configuration requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single disclosed embodiment, configuration, or aspect described above. While certain aspects of the prior art have been discussed to facilitate disclosure of some embodiments of the present invention, applicants do not intend to disclaim any of these technical aspects, and the claimed invention may encompass one or more of the prior art aspects discussed herein. Accordingly, the following claims are hereby incorporated into this specification, with each claim standing on its own as a separate aspect, embodiment, or configuration. [Example]

[0031] [Production of aromatic hydrocarbons for jet fuel by continuous hydrodeoxygenation of lignin] This example describes a solvent-free process for HDO of poplar RCF lignin oil with near-quantitative carbon yields using an earth-abundant molybdenum carbide (MoC) catalyst. HDO experiments under solvent-free conditions with a continuous inflow of real lignin feedstock were conducted in a custom-built, three-phase trickling-bed reactor. Poplar RCF lignin oil was selected as an exemplary lignin substrate based on recent findings demonstrating the commercial viability of RCF in lignin-first biorefineries. The RCF process involves solvent extraction and catalytic decomposition of lignin from whole biomass, producing an oxygenated aromatic oil composed of ~50 wt% monomeric species and ~50 wt% carbon-carbon bonded dimers and larger oligomers. Thus, complete deoxygenation of RCF oil produces a mixture rich in C9 to C20 alkylated arenes, which is ideal for jet fuel blending. 〔result〕

[0032] (Tracking deoxygenation using Mo2C catalyst) The complexity of lignin oil components and their deoxygenation products requires rigorous analytical methods to accurately calculate mass balances. Therefore, we identified and quantified partially and fully deoxygenated monomers and dimers in HDO experiments using a feedstock consisting of 2 wt% RCF oil dissolved in toluene. We used unsupported Mo2C as a catalyst due to its ability to directly cleave the CO bond in model aromatic oxygenated molecules without hydrogenating the aromatic ring. While Mo2C has not been extensively studied for the exhaustive deoxygenation of lignin oils, we hypothesized that it could provide a method for controlling hydrogen-efficient deoxygenation and aromatic product selectivity. Figure 1A summarizes all lignin-derived monomers quantified in this study by gas chromatography with flame ionization detection (GC-FID). This method yielded a monomer molar balance of 100% ± 5% at all levels of partial conversion examined. We used trimethylsilyl derivatization and GC coupled with gas chromatography-mass spectrometry (GC-MS) to identify dimeric compounds at different levels of conversion (Figure 1B). In general, the monomer and dimer species showed similar conversion and selectivity trends to those observed in gas-phase MoC HDO using model compounds. The first functional group to undergo deoxygenation is the γ-hydroxyl group (e.g., dihydroconiferyl alcohol, PG-OH), producing guaiacol and syringol derivatives. Next, deoxygenation of the methoxy group (e.g., propylguaiacol, PG) produces phenols. Finally, cleavage of the phenol group (e.g., propylphenol, PP) produces alkylbenzenes.

[0033] (Evaluation of the stability of solvent-free lignin oil) While a 2 wt% RCF oil mixture in toluene was a useful system for analytical method development, toluene only dissolves up to 70 wt% of RCF oil, preferentially extracting low-molecular-weight components. For this reason, pure RCF oil was used as the feedstock for all subsequent studies. To investigate the stability of solvent-free RCF oil at high temperatures and determine the acceptable operating temperatures for the HDO process, we performed uncatalyzed flow experiments using other conditions suitable for HDO chemistry. At reactor temperatures of 325 °C, 350 °C, and 375 °C, the mass recoveries of lignin oil were 98.7 (±1.2), 98.5 (±2.0), and 98.6 (±2.5) wt%, respectively. At 400 °C, the mass recovery was 93.2 (±0.9) wt% (Figure 2A). PG-OH and PS-OH, which account for 15 wt% of the RCF oil feedstock, were the most temperature-sensitive monomers, with total recoveries of 90.0, 87.9, 40.2, and 17.8 wt% at 325 °C, 350 °C, 375 °C, and 400 °C, respectively. Furthermore, in a catalyst-free experiment at 400 °C, rearranged, alkylated, and partially deoxygenated monomer products were produced, totaling 5.6 wt%. Changes in the molecular weight distribution of the lignin oil were characterized using gel permeation chromatography (GPC) and GC-MS data from derivatized samples. Increasing the temperature from 325 °C to 400 °C gradually decreased the dimer concentration, indicating that condensation reactions favored the formation of new oligomers (Figure 2B).

[0034] (Mo2C catalytic activity during HDO reaction of lignin oil) Next, we evaluated the activity and stability of MoC in the continuous HDO reaction of undiluted lignin oil at temperatures below 400 °C to reduce deleterious lignin condensation (Figures 3A–3E). To avoid structural changes in the char phase caused by exposure to molecular oxygen, fresh MoC was synthesized in situ by carbonization of ammonium molybdate tetrahydrate (AMT) immediately before the start of each experiment. The temperature was 350 °C, weight hourly space velocity (WHSV) 2.35 g. リグニン / g 触媒Under the conditions of 1000 kJ / h, the monomer oxygen conversion reached a steady state at 65.8 ± 0.05 mol%, and the main monomer products were PP at 50.2 mol%, PB at 13.8 mol%, and PB-OMe at 11.6 mol% (Figure 3A). Although stable deoxygenation was achieved under these conditions, the residence time (WHSV = 1.175 h) was significantly longer. -1 Doubling the temperature and reusing the partially deoxygenated oil over a fresh catalyst bed at 350 °C did not result in complete deoxygenation of the monomer. Higher temperatures were required to activate the aryl-OH bond, at 375 °C and WHSV = 2.35 h. -1 We achieved 48.5% removal of phenolic groups at 300°C and 325°C. Figures 3B and 3C show the effect of temperature on catalyst stability. Transient data collected during 2.5-6 hour runs at 300°C and 325°C showed stable deactivation profiles, with monomer oxygen conversion decreasing from 58 to 52 mol% at 325°C and from 32 to 22 mol% at 300°C. While temperatures as low as 150°C have been used to deoxygenate anisole and 280°C for near-complete deoxygenation of a model phenolic mixture to aromatics at steady state using Mo2C, our data indicate that temperatures of 350°C and 375°C, respectively, are required for stable removal of methoxy and phenolic groups in pure lignin oil. These results regarding activity and stability are similar to the performance of MoO3 in HDO. PXRD analysis of the catalyst after the reaction did not indicate bulk oxidation to MoO3, but in situ techniques indicate that the surface of Mo2C is oxidized during the reaction with oxygen-containing compounds. This may explain why previous studies using Mo2C on the HDO of real lignin feedstocks with high oxygen content did not achieve complete deoxygenation, and highlights the difficulty of applying model system results to biomass feedstocks.

[0035] (Achieving thorough deoxygenation to aromatic hydrocarbons) Taken together, the lignin-oil stability (Figures 2A-2B) and catalytic activity (Figures 3A-3E) experiments reveal an important trade-off in the HDO of lignin-oil. At low temperatures, the catalyst deactivates but high carbon balance is achieved by maintaining oligomers. On the other hand, high temperatures are required to maintain catalytic activity and achieve complete deoxygenation, resulting in the loss of dimers through condensation. We evaluated two methods to produce highly deoxygenated oil products: i) 400 °C for WHSV = 1.175 h; -1 (ii) increasing the temperature and residence time in the first pass under conditions of (i) above; and (ii) operating in a two-pass mode, where the first HDO step was performed at an intermediate temperature to produce a mixture of partially deoxygenated monomers and oligomers that are more resistant to subsequent condensation reactions, followed by a second pass at a higher temperature to achieve complete deoxygenation. In the two-pass experiments, the products from the first pass were recovered over a fresh catalyst bed at 325°C, 350°C, or 375°C, respectively. These products were then deoxygenated in a second pass at 375°C using a fresh catalyst bed. Figure 4A summarizes the carbon, hydrogen, and oxygen content of each oil, along with the mass recovery for each pass and the overall carbon recovery. After the first passes at 400°C, 375°C, 350°C, and 325°C, 0.7, 8.0, 11.7, and 15.8 wt.% oxygen remained, respectively. This decreased to 1.0, 2.1, and 1.2 wt % at 375-375°C, 350-375°C, and 325-375°C, respectively.

[0036] Near-complete deoxygenation of the product was confirmed by heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance spectroscopy (NMR) and derivatization + GC-MS. The final monomer product distribution was similar in both cases, with a selectivity value of approximately 78 mol% for propylbenzene. The dimer product was more sensitive to temperature, and quantitative GC × GC analysis showed that the dimer contents were 8.9, 9.5, 11.9, and 14.2 wt% for first-pass temperatures of 400 °C, 375 °C, 350 °C, and 325 °C, respectively (Figure 4B). This trend in dimer recovery was confirmed by simulated distillation (Figure 4C) and other chromatographic techniques.

[0037] An optimal balance between catalyst stability and jet fuel aromatics production was achieved by performing a second pass at 350 °C followed by 375 °C. In fact, 350 °C was the optimal temperature for maintaining stable catalytic activity during partial deoxygenation in the first pass (total product oxygen content of 11.7%). Meanwhile, higher temperatures of 375 °C and 400 °C increased the loss of aromatic dimers. Figure 4D summarizes the optimal overall process. We successfully reduced the total oxygen content from 26.3 mol% to 2.1 mol% (95.7% conversion). We also achieved an unprecedented recovery of 73.1 C-mol% (86% of the theoretical value based on removal of methoxy groups) and a monomer selectivity to aromatic hydrocarbons of 87.5%. For reference, recent reports have shown that the yields for one- and two-step processes are 10–30 wt% and 30–50 wt%, respectively. On the other hand, our process consistently achieved mass recoveries of 50-60 wt%, achieving higher deoxygenation levels than those reported in these studies. Quantitative GC × GC analysis determined the final aromatic dimer (C14-C20) content to be 11.9 wt% and aromatic monomer (C9-C12) content to be 56 wt%, resulting in a total of 67.9 wt% jet fuel aromatics in the final oil. [Discussion, Recommendations, and Conclusions]

[0038] The provided examples demonstrate that lignin stability is a major limitation under typical HDO conditions. They also demonstrate that two-pass HDO, i.e., stabilization by partial conversion in the first pass followed by extensive deoxygenation in the second pass, is a viable strategy for improving lignin with high atom economy. This strategy may be broadly applicable to other lignin feedstocks. Furthermore, HDO reactions using Mo2C selectively cleaved C-O bonds in the lignin substrate while preserving the C-C structure. In addition to minimizing hydrogen consumption, this selectivity suggests the possibility of tailoring the HDO product distribution by modifying the lignin feedstock itself. For example, utilizing a lignin substrate with a high proportion of dimer components can increase the C14–C20 aromatic fraction in the deoxygenated product. Furthermore, the carbon skeletons of the dimer and oligomer fractions maintain sufficient chemical functionality during the reaction to differentiate the types of inter-lignin bond types (e.g., β-1 vs. β-5) synthesized in plants. This provides analytical opportunities to quantitatively track lignin bond distribution.

[0039] This example inspires the development of catalysts capable of achieving stable HDO of real lignin feedstocks at low temperatures. Notably, the catalyst behavior in reactions with pure lignin oil was clearly different from previously reported studies of gas-phase model compounds. Furthermore, while the existing literature provides a strong framework for understanding the impact of controlled MoC surface oxidation on model compound reactivity, the parameters determining the extent of catalytic oxidation under reaction conditions with real feedstock lignin have not previously been mapped and are not fully understood. Understanding the factors driving catalyst surface deactivation under reaction conditions with real feedstocks may enable rational catalyst design or reaction engineering solutions that mitigate catalyst deactivation and enable lower operating temperatures. Overall, conducting experiments in a trickling-bed reactor using real feedstock lignin to generate continuous, steady-state HDO data, along with rigorous analysis to track carbon balances and individual components, was essential to understanding the limitations of this complex system.

[0040] The deoxygenated aromatics obtained from this process can be directly blended with existing commercial SAF (composed primarily of iso- and n-paraffins), potentially overcoming the current 50% blending barrier by providing the aromatic components necessary to enhance both fuel density and elastomer compatibility. Subsequent hydrogenation, ring-opening, and / or hydrocracking reactions can also be carried out to convert a fraction of the lignin-derived aromatics into other paraffinic compounds (including naphthenes and iso- / n-alkanes), thereby producing an entirely lignin-derived SAF.

[0041] Finally, we propose blending potential feedstocks (rather than deoxygenated products) to achieve the desired aromatic / aliphatic ratio, followed by deoxygenation over Mo2C to directly produce a complete drop-in SAF. Ongoing techno-economic analysis and life cycle assessment aim to identify key areas for further development and integration of our products into 100% SAF blends. 〔material and method〕

[0042] (RCF lignin oil production) 60 g of poplar (ground to less than 2 mm and sieved), 12 g of 5 wt. % ruthenium-loaded carbon (Sigma-Aldrich®), and 400 mL of methanol (ACS reagent grade, Macron Fine Chemicals) were charged into a 1 L batch reactor (Parr Instrument Company®, Series 4525HP). The reactor was sealed, flushed three times, and then pressurized to 30 bar with H2 (UHP, Airgas®). During the reaction, the mixture was stirred at 700 rpm using an overhead impeller. The temperature was monitored using an internal thermocouple, and the furnace, stirring speed, and cooling water were controlled by a Parr® instrument controller (Series 4848). The temperature was increased from 25°C to 225°C over 1.5 hours, then held at 225°C for 3 hours, followed by rapid cooling to 25°C with cooling water. The catalyst loading, hydrogen pressure, and reaction time were optimized to achieve complete conversion of the ether linkage and allow molar closure of the monomer without the formation of monomer during HDO.

[0043] After the reaction, the lignin fraction was isolated by vacuum filtration through a 4 μm ceramic filter. The solids were washed twice with methanol, and the solvent was removed under vacuum. The resulting oil was purified by dichloromethane (DCM) / water extraction to remove any sugars or acids extracted from the biomass during RCF. This was done using 30 mL of DCM (Laboratory-plus grade, Honeywell®) and 30 mL of water (Milli-Q®), followed by two 15 mL washes of the aqueous phase. The DCM was pre-removed by rotary evaporation at 100 Torr, followed by secondary evacuation to 0.1 mTorr on a Schlenk line with magnetic stirring at 250 rpm, and then removed from the organic phase under vacuum. Overall, this process yielded ~9 g of purified RCF lignin oil from a single 60 g poplar RCF run.

[0044] (Catalyst synthesis) AMT (ACS reagent grade, Sigma-Aldrich®) was sieved through 60–100 mesh and charged into a trickle-bed reactor in an amount appropriate to obtain the desired amount of MoC (see charging procedure). The reactor was then heated from 25 °C to 700 °C over 3.5 h and held at 700 °C for 3 h. Hydrogen gas was flowed at a rate of 55 mL / min throughout the synthesis, and methane (UHP, Airgas) was flowed at a rate of 15 mL / min for the first 6 h. This allowed for a 0.5-h purge step with pure hydrogen gas at 700 °C. The reactor was then cooled and sealed under flowing hydrogen gas prior to reaction.

[0045] (Trickling bed reactor design) The reaction was carried out in a custom-built trickle-bed reactor. The 21-inch long, 1 / 4-inch outer diameter Hastelloy reactor tube was heated by a vertically mounted, adiabatic, single-zoned furnace (Applied Test Systems®, Series 3210) with a steel block (machined to fill the voids in the furnace) to ensure adequate heat transfer and maintain isothermal operation. A K-type thermocouple attached to the outside of the reactor tube was used for temperature measurement, and another thermocouple attached to the outside of the steel block in the center of the furnace was used to regulate the temperature with a PID temperature controller (Digi-sense®, TC9500). Gas flow rates were controlled using mass flow controllers (Brooks®, SLA5850S1BAB1B2A1), and liquids were delivered by a Teledyne® ISCO syringe pump (Model 500D). Liquid was fed to the top of the reactor through 1 / 16-inch OD 316 stainless steel tubing extending to the beginning of the heating zone. Gas was fed to the top of the reactor through 1 / 4-inch 316 stainless steel tubing and co-flowed with the liquid in a downward flow through the packed catalyst bed. Liquid samples were collected at room temperature in a gas-liquid separator (Jerguson Gage & Valve Co.®). Gas exited the top of the gas-liquid separator and passed through a diaphragm backpressure regulator (Equilibar®, H3P1SNN8-NSBP1500T100G20KK) to maintain total system pressure. A nitrogen backfill line allowed system pressure to be maintained during sampling via a needle valve (Swagelok®).

[0046] (Reactor Filling Procedure) A quartz wool (Technical Glass Products Inc.®) plug was placed at the bottom of the reactor tube, followed by 9.75 inches of quartz chips (fused silicon dioxide (granular), Sigma-Aldrich®) filling the reactor from the bottom to the center of the heated zone of the furnace. The quartz wool plug, catalyst layer, and another quartz wool plug were loaded in this order. For the pure lignin oil experiments, the catalyst layer consisted of pure catalyst only. For the 2 wt% lignin oil in toluene experiments, the catalyst was diluted to 1 g with 120-grit silicon carbide powder (98.0% or higher, Alfa Aesar®). Finally, quartz chips were added to the top of the reactor, up to 1 inch below the level of the drop tube.

[0047] (Preparation of raw materials) Following the above procedure for producing RCF oil, pure lignin oil was used directly and oils produced in 5–10 batch reactions were mixed to produce 45–90 g of raw oil. Regenerated lignin oil was prepared by mixing samples from previous experiments after removing enough samples for analysis. The aqueous phase that phase-separated from the partially deoxygenated lignin oil was removed with a pipette. 2 wt% lignin oil diluted in toluene was prepared by adding 2 wt% lignin oil, 0.2 wt% decane (≥99.0%, Sigma-Aldrich®), and 97.8 wt% toluene (≥99.8%, VWR Chemicals® BDH) to a large glass container. The mixture was then vigorously shaken, sonicated for 20 minutes, and allowed to equilibrate overnight. The cloudy lignin oil in toluene was centrifuged at 8000 rpm for 5 minutes to remove any suspended, undissolved lignin oil and prevent clogging. The resulting liquid was decanted and used in the reaction.

[0048] (Reaction execution) After catalyst synthesis, the reactor was cooled to room temperature at atmospheric pressure while flowing hydrogen at a rate of 55 mL / min. A steel heat transfer block was placed inside the furnace, and the reactor was slowly pressurized to a reaction pressure of 900 psi with a nitrogen backfill. The hydrogen flow rate was set at 30 mL / min for the toluene-dissolved reagents or 90 mL / min for the pure lignin oil. The reactor was leak-checked and heated. For the toluene-dissolved reagents, the feed was flowed at a rate of 2 mL / min during heating to prewet the catalyst bed. The feed flow rate was reduced to the reaction flow rate once the reactor reached the desired temperature. The reservoir was vented when the furnace reached 200 °C, and samples were taken when the furnace reached 250 °C and 300 °C. Samples were taken every 40 min throughout the experiment. For the pure lignin oil experiments, the reactor was heated to the reaction temperature while flowing pure toluene at 1 mL / min. Once the reactor reached temperature, the liquid feed was switched to pure lignin oil at a flow rate of 0.1 mL / min or 0.05 mL / min. Samples were taken every 30 or 60 min.

[0049] (Sample workup and analysis) Each sample was collected in a pre-weighed vial, allowing for post-experiment sample mass measurement. To prepare pure lignin oil samples for gas chromatography with flame ionization detection (GC-FID) analysis, 30 μL of oil was dissolved in 2 mL of acetone containing 2 mg / mL of 1,3,5-tri-tert-butylbenzene (≥98.0%, TCI®). For accuracy, the oil and acetone solutions were weighed and dissolved. For experiments using reagents dissolved in toluene, samples were weighed and injected into the GC-FID without additional workup procedures, using the included decane internal standard. To prepare samples for NMR analysis, 100 mg of oil was dissolved in 500 μL of acetone-d6 (99 atom % D, Acros Organics®).

[0050] (Quantitative determination of monomers by GC-FID) One microliter of each prepared sample was injected into an Agilent 7890A GC system using an Agilent Technologies 7693 autosampler. The GC method used a split ratio of 10:1, an inlet temperature of 280°C, and a ramp rate of 10°C / min from 50°C to 280°C, followed by a 10-minute hold at 280°C, for a total run time of 29 minutes. The GC was equipped with a 30 m x 250 μm x 0.25 μm Agilent Technologies HP-5MS column, and a flame ionization detector (FID) was used for product quantification.

[0051] GC-FID was used to measure methylcyclohexane (99.0% or higher, TCI®), toluene (99.8% or higher, VWR Chemicals®), and The samples were calibrated with BDH), propylcyclohexane (98.0%, TCI), propylbenzene (≥99.0%, Sigma-Aldrich®), 4-propyltoluene (≥99.0%, TCI®), p-propylanisole (≥99.0%, Sigma-Aldrich®), 4-propylphenol (≥99.0%, Sigma-Aldrich®), 2-methoxy-4-propylphenol (propylguaiacol) (≥99.0%, Sigma-Aldrich®), isoeugenol (≥98.0%, Sigma-Aldrich®), 4-allyl-2,6-dimethoxyphenol (≥95.0%, Sigma-Aldrich®), and dihydroconiferyl alcohol (synthesized in-house). Relative response factors (RFs) were obtained for each of these compounds using decane (in experiments conducted in toluene, where decane was used as an internal standard) and 1,3,5-tri-tert-butylbenzene (in experiments using pure lignin oil). Furthermore, to accurately quantify decane in lignin oil in toluene feedstock, decane was calibrated using the relative response factor for 1,3,5-tri-tert-butylbenzene. RFs were calculated by fitting a line plot of the relative mass fraction of the target compound versus the area ratio to the standard. For non-commercially available products, an adjustment factor was used to obtain an approximate RF. For each sample, the peak areas corresponding to known products were integrated. The ratio of the compound's peak area to the standard peak area was calculated, and the mass fraction of the compound was obtained by multiplying the RF and the mass fraction of the standard. The mass fraction was then used for subsequent calculations, such as molar balance, conversion, and yield.

[0052] (Gas Chromatography and Mass Spectrometry (GC-MS)) Analysis was performed using an Agilent Technologies® 7820A GC system equipped with an HP-5MS Ultra Inert 30 m x 250 μm x 0.25 μm column and an Agilent® 5977B single quadrupole mass detector. Monomeric compounds in the raw materials and products were identified by injecting the same samples into GC-FID and GC-MS using the same column and method. Products were identified using GC-MS fragmentation patterns, which matched the identical retention times observed in GC-FID.

[0053] Dimers were analyzed by GC-MS after derivatization, similar to our previously published method. Solvent-free lignin oil samples were dissolved in tetrahydrofuran (HPLC grade, VWR Chemicals® BDH) (THF) at a concentration of 10 mg / mL. The derivatization reaction was carried out by mixing 600 μL of a 10 mg / mL lignin oil solution, 50 μL of pyridine, and 100 μL of a silylating agent [N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) containing 1% trimethylchlorosilane (TMS) (Sigma-Aldrich®)] and heating at 50 °C for 20 min. Because BSTFA readily reacts with water, it was ordered in 1 mL ampoules and used immediately after opening.

[0054] For analysis, 1 μL of sample was manually injected into the GC-MS. This method used a split ratio of 10:1, a flow rate of 12 mL / min, and an inlet temperature of 280 °C. The oven was programmed to ramp from 150 °C to 300 °C at a rate of 5 °C / min and hold at 300 °C for 18 min, for a total run time of 49 min. GC-MS spectra were analyzed by comparing them to published structures of the dimer to predict possible structures and comparing these with the MS spectrum of the unknown.

[0055] (Gel Permeation Chromatography (GPC)) Gel permeation chromatography was performed according to a procedure similar to our previously published method. Neat oil samples were prepared for gel permeation chromatography by dissolving them in THF (HPLC grade, VWR Chemicals® BDH) at a concentration of 2 mg / mL and filtering through a 0.2 μm PTFF syringe filter. 20 μL of each sample was injected using a Hewlett-Packard 1100 Series autosampler. THF was used as the carrier solvent at a flow rate of 0.3 mL / min. Three 5 μL PLgel Agilent GPC columns (10 4 Å, 10 3 The columns (50 Å and 50 Å) were arranged in series in increasing order of pore size. The columns were kept at a constant temperature of 26°C, and the system was operated at a pressure of approximately 30 bar (a function of flow rate, column choice, and temperature). Analysis of the eluate was performed using a UV diode array detector at a wavelength of 280 nm, with a reference wavelength of 360 nm and a slit of 4 nm.

[0056] (NMR spectroscopy) NMR spectra were acquired on a Bruker® Advance Neo 400 MHz equipped with a 5 mm broadband observation (BBFO) SmartProbe, and spectra were processed using Bruker's TopSpin® 4.0.8 (Windows) software. The central solvent peak (acetone-d6) was used as the internal reference (δC / δH: 29.84 / 2.05 ppm). Structure elucidation and assignment verification of monomers and oligomers were performed using a set of conventional 1D and 2D (gradient selection and 1 H detection, e.g. 1 H‐ 13 C HSQC NMR experiments were performed using a typical matched Gaussian apodization for F2 (LB = -0.1; GB = 0.001) and a squared cosine bell apodization for F1.

[0057] (Quantitative GC x GC TOF-FID analysis) Detailed characterization of the deoxygenated hydrocarbon products was performed by comprehensive two-dimensional gas chromatography with simultaneous time-of-flight mass spectrometry and flame ionization detection (GC×GC TOF-FID). Samples were prepared for analysis by dilution (1:10 by weight with acetone). A LECO Pegasus® 4D system (LECO Corp®) equipped with a liquid nitrogen-cooled thermal modulator and post-column flow splitter was used for the analysis. The primary column was an Rtx-17sil, 20 m x 180 μm x 0.18 μm, and the secondary column was a ZB-5HT, 1.0 m x 180 μm x 0.18 μm. The method used an injection volume of 1.0 μL, a split ratio of 100:1, and an injector temperature of 300 °C. The primary oven was held at 35 °C for 5 min, then ramped to 125 °C at 3 °C / min, ramped to 350 °C at 10 °C / min, and held for 1 min. The secondary oven was offset by 40°C from the primary oven, and the modulator was offset by 15°C from the secondary oven. The modulator period was set to 8 seconds, with a 1-second hot pulse and a 3-second cold pulse from the start of the run until 800 seconds, followed by a 2-second hot pulse and a 2-second cold pulse until the end of the run. The transfer line to the mass spectrometer and FID was held at 350°C. The TOF mass range was m / z 29–600, the acquisition rate was 200 spectra / second, and the solvent delay was 70 seconds. The FID flow rates were set to 40 mL / min of hydrogen, 300 mL / min of air, and 25 mL / min of nitrogen. Compounds were identified using LECO ChromaTof® software by library matching and exploiting the retention time regions of the 2D chromatograms. The FID signal was calibrated using a set of representative compounds to establish linearity and precision. All linear calibration results were R 2 ≥ 0.995. Compounds were quantified from their theoretical response factors calculated from the effective carbon numbers.

[0058] (Qualitative GC x GC FID / MS analysis) Qualitative characterization of the deoxygenated products was performed using two-dimensional gas chromatography coupled with flame ionization detection and mass spectrometry (GC×GC FID / MS). The analysis was performed using an Agilent® 7890A GC and an Agilent 5975C Inert XL MSD. The system was equipped with a thermomodulator (Zoex ZX10711) cooled by a chiller (PolyScience® P10N4A101B). Samples were injected directly after the reaction. Data analysis was performed using the software package Canvas. TM This was done using v4.

[0059] The primary column was an Rxi-5HT, 30 m x 0.25 mm x 0.25 μm, and the secondary column was a BPX50, 2 m x 0.15 mm x 0.25 μm. The analytical method used a split ratio of 50:1, an injection volume of 5 μL, and an injector temperature of 350 °C. The primary oven was held at 45 °C for 1 min and then ramped to 300 °C at 3 °C / min. This temperature was then held for 5 min. The secondary column was offset by 25 °C from the primary column, and the thermal modulator was offset by 5 °C from the secondary column. The modulator had a 16-second period and a hot jet duration of 375 ms. The transfer line to the MS was maintained at 250 °C. The mass range was set to 40–550 m / z, the acquisition rate was 50 spectra / s, and there was no solvent delay. The FID detector was maintained at 300 °C, with a hydrogen flow rate of 30 mL / min and an air flow rate of 400 mL / min.

[0060] (Total Carbon, Hydrogen and Oxygen (CHO) Analysis Method) Total carbon and hydrogen were measured by the combustion method using a LECO® Series CHN628 elemental analyzer (LECO® Corp.) Oxygen content was calculated by difference.

[0061] (Simulated distillation) Due to limited sample volume, distillation temperatures were determined by simulated distillation rather than physical distillation (i.e., ASTM D86). The boiling range distribution of the deoxygenated oil was measured by simulated distillation according to ASTM method D2887-19. An Agilent® 7890A GC equipped with a cooled column inlet and FID was used. The method settings were those described in ASTM D2887 Table 1 for the open tubular column (option 7). The column used was an MXT-1HT, 10 m x 530 μm x 2.65 μm (Restek Corp®). Samples were diluted 1:10 by volume with carbon disulfide for analysis. An injection volume of 0.1 μL was injected onto the analytical column. Boiling point calibration was performed using a prepared standard purchased from Sigma-Aldrich® (part number #500658), and accuracy was verified with the standard reference diesel oil described in D2887. Data analysis was performed using Separation Systems SimDis Expert® 9.

[0062] (Mass balance in pure lignin HDO experiments) To calculate the mass balance, a single-pass pure lignin-oil experiment was conducted in which steady-state samples were accumulated for 3 hours. Up to 18 mL of sample was collected in a pre-weighed flask. After weighing the entire sample, the aqueous phase was removed using a pipette. The remaining organic phase was weighed and characterized. The mass flow rate of the lignin-oil feedstock was measured by weighing the oil collected directly at the outlet of the ISCO pump for 4 minutes at the experimental flow rate, repeated three times. The feedstock mass was obtained by multiplying the mass flow rate by the steady-state collection time. The carbon mass recovery was obtained by multiplying the feedstock mass and steady-state oil mass by the carbon mass percent of each sample.

[0063] (Solid composition analysis procedure) Compositional analysis of poplar samples was performed according to guidelines published by NREL. The poplar used was a reference material from the Idaho National Laboratory (origin: Morrow County, Oregon; harvest year: 2013; hybrid clone: Populus deltoides × Populus nigra, clone OP-367). The samples were first washed with high-pressure, high-temperature running water, followed by ethanol. The biomass was then treated with 72 wt% sulfuric acid at 30°C for 1 hour with stirring. The slurry was then diluted with water to 4 wt% sulfuric acid and heated in an autoclave at 121°C for 1 hour. Klason lignin content was determined gravimetrically by filtering the acid-insoluble residue from the acidified water slurry. The Klason lignin was then combusted to determine the ash content of the biomass. Acid-soluble lignin was quantified by UV / Vis spectroscopy (Thermo Scientific Nanodrop® 8000 spectrophotometer). Lignin absorbance measurements were performed at 240 nm and quantified with an extinction coefficient of 2.5. Sugar content was measured by high-performance liquid chromatography (HPLC, Agilent® 1100 HPLC) using a refractive index detector (RI) maintained at 55°C. A Shodex® Sugar SP0810 column equipped with a guard column was used for the analysis, with HPLC-grade water as the mobile phase at a flow rate of 0.6 mL / min at 85°C.

[0064] (Catalyst characterization by powder X-ray diffraction) Powder X-ray diffraction (PXRD) was performed using a Bruker® D8 diffractometer with Cu Kα radiation, a step size of 0.02°, and a step time of 0.2 seconds. [Example]

[0065] [Comparison of poplar, pine and corn stover raw materials] Comparisons of various lignin feedstocks are shown in Figures 8-12. Figure 7 shows examples of monomers corresponding to jet fuel grade cycloalkanes and aromatics that can be produced by the methods provided herein.

[0066] The invention described herein can be further understood by the following non-limiting examples.

[0067] (Example 1) A method comprising the steps of: providing reactants comprising lignin and hydrogen; partially deoxygenating the reactants in the presence of a first catalyst at a first temperature to produce an intermediate; Deoxygenating the intermediate in the presence of a second catalyst at a second temperature to produce a product comprising aromatic hydrocarbons.

[0068] (Example 2) The method of Example 1, wherein the second temperature is higher than the first temperature.

[0069] (Example 3) 3. The method of any one of Examples 1 to 2, wherein the reactants comprise more than 50% lignin oil.

[0070] (Example 4) 4. The method of any of Examples 1 to 3, wherein the reactants comprise greater than 99% lignin oil.

[0071] (Example 5) The method according to any one of Examples 1 to 4, wherein the reactants do not contain a solvent.

[0072] (Example 6) The method according to any one of Examples 1 to 5, wherein the first temperature is selected from the range of 250°C to 450°C.

[0073] (Example 7) The method according to any one of Examples 1 to 6, wherein the second temperature is selected from the range of 275°C to 475°C.

[0074] (Example 8) The method of any of Examples 1-7, wherein the first catalyst, the second catalyst, or both, comprise Mo2C.

[0075] (Example 9) The method of any of Examples 1 to 8, wherein the first catalyst and the second catalyst are the same.

[0076] (Example 10) The method according to any one of Examples 1 to 9, wherein the partial deoxidation step and the deoxidation step are each carried out successively.

[0077] (Example 11) The method of any of Examples 1 to 10, wherein the partial deoxidizing and deoxidizing steps are part of a continuous process.

[0078] (Example 12) The method of any of Examples 1 to 11, wherein the product is a sustainable aviation or marine fuel.

[0079] (Example 13) The method according to any one of Examples 1 to 12, wherein the oxygen molar fraction of the product is 5% or less.

[0080] (Example 14) A reactor comprising: a first reaction zone containing a first catalyst at a first temperature; a second reaction zone containing a second catalyst at a second temperature; wherein the reactor is capable of hydrodeoxygenating lignin to produce aromatic products.

[0081] (Example 15) 15. The reactor of Example 14, wherein the second temperature is greater than the first temperature.

[0082] (Example 16) 16. The reactor of example 14 or 15, wherein the reactor is a trickle bed reactor.

[0083] (Example 17) 17. The reactor of any of Examples 14-16, wherein the first catalyst, the second catalyst, or both, comprise Mo2C.

[0084] (Example 18) 18. The reactor of any of Examples 14 to 17, wherein the reactor is capable of continuously producing an aromatic product.

[0085] (Example 19) A catalyst containing Mo2C that can convert lignin into aromatic compounds with a yield of 80% or more.

[0086] The terms and expressions used herein are used as terms of description and not of limitation. Furthermore, the use of such terms and expressions is not intended to exclude equivalents of the shown and described features or portions thereof, but recognizes that various modifications are possible within the scope of the invention as defined by the appended claims. Thus, while the present invention has been specifically disclosed by preferred and exemplary embodiments and optional features, it should be understood that those skilled in the art may utilize modifications and variations of the concepts disclosed herein, and that such modifications and variations may be considered within the scope of the invention as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the invention, and it will be apparent to those skilled in the art that the invention can be practiced using numerous variations of the apparatus, apparatus components, methods, and steps described herein. As will be apparent to those skilled in the art, methods and apparatus useful for the present methods can include numerous optional components and processing elements and steps.

[0087] As used herein and in the appended claims, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Thus, for example, a reference to "a cell" includes a plurality of such cells and equivalents known to those skilled in the art. Similarly, the terms "a" (or "an"), "one or more," and "at least one" can be used interchangeably herein. It should also be noted that the terms "consisting of," "including," and "having" can be used interchangeably. The phrase "any of claims XX-YY" (where XX and YY refer to claim numbers) is intended to provide multiple dependent claims in an alternative format and, in some embodiments, is interchangeable with the phrase "any of claims XX-YY."

[0088] When a group of substituents is disclosed herein, it is understood that all individual elements and all subgroups of that group are individually disclosed. When a Markush group or other group is used herein, it is intended that all individual elements of the group and all possible combinations and subcombinations of the group are individually disclosed. For example, when a device is described that discloses various materials, device components, and / or device configurations, it is intended that the description include specific reference to each combination and / or variation that corresponds to the disclosed range.

[0089] Any and all ingredient formulations or combinations of components described or exemplified herein may be used to practice the present invention unless otherwise specified.

[0090] When a range is given in the specification, all intermediate and subranges and all individual values contained within that range are intended to be included in the disclosure, such as, for example, a density range, a numerical range, a temperature range, a time range, or a composition or concentration range, etc. It is understood that any range or individual value within a range or subrange contained herein can be excluded from the claims.

[0091] All patents and publications cited in the specification are indicative of the level of skill of those skilled in the art to which the invention pertains. References cited herein are incorporated by reference in their entirety to demonstrate the state of the art as of the publication date or filing date. It is also intended that this information be used herein, where appropriate, to exclude certain embodiments that fall within the prior art. For example, if a composition of matter is claimed, it should be understood that compounds known and available in the art prior to the applicant's invention, including compounds for which the references cited herein provide useful disclosures, are not intended to be included within the scope of the composition of matter claims herein.

[0092] As used herein, "consisting of" is synonymous with "comprising," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of" excludes elements, steps, or ingredients not specified in the claim element. As used herein, "consisting essentially of" does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In any instance herein, any of the terms "comprising," "essentially comprising," and "consisting of" may be replaced with either of the other two terms. The inventions illustratively described herein may suitably be practiced in the absence of any element or elements, limitation, or limitations not specifically disclosed herein.

[0093] All known functional equivalents of all materials and methods are intended to be encompassed by the present invention. The terms and expressions used are used as terms of description rather than limitation, and the use of such terms and expressions is not intended to exclude equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed invention. Thus, while the present invention has been specifically disclosed by preferred embodiments and optional features, it should be understood that those skilled in the art may make modifications and variations of the concepts disclosed herein, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

Claims

1. A method comprising the steps of: providing reactants comprising lignin and hydrogen; partially deoxygenating the reactants in the presence of a first catalyst at a first temperature to produce an intermediate; Deoxygenating the intermediate in the presence of a second catalyst at a second temperature to produce a product comprising aromatic hydrocarbons.

2. The method of claim 1 , wherein the second temperature is greater than the first temperature.

3. 10. The method of claim 1, wherein the reactants comprise greater than 50% lignin oil.

4. 10. The method of claim 1, wherein the reactants comprise greater than 99% lignin oil.

5. The method of claim 1 , wherein the reactants are solvent-free.

6. The method of claim 1, wherein the first temperature is selected from the range of 250°C to 450°C.

7. The method of claim 1, wherein the second temperature is selected from the range of 275°C to 475°C.

8. The first catalyst, the second catalyst, or both are Mo ２ The method of claim 1 , comprising C.

9. The method of claim 1 , wherein the first catalyst and the second catalyst are the same.

10. The method of claim 1 , wherein the partial deoxidizing step and the deoxidizing step are each performed sequentially.

11. 10. The method of claim 1, wherein the partially deoxidizing and deoxidizing steps are part of a continuous process.

12. 10. The method of claim 1, wherein the product is a sustainable aviation or marine fuel.

13. 10. The method of claim 1, wherein the product has an oxygen mole fraction of 5% or less.

14. A reactor comprising: a first reaction zone containing a first catalyst at a first temperature; a second reaction zone containing a second catalyst at a second temperature; wherein the reactor is capable of hydrodeoxygenating lignin to produce aromatic products.

15. The method of claim 14 , wherein the second temperature is greater than the first temperature.

16. The method of claim 14, wherein the reactor is a trickle bed reactor.

17. The first catalyst, the second catalyst, or both are Mo ２ The method of claim 14, comprising C.

18. 15. The method of claim 14, wherein the reactor is capable of continuously producing aromatic products.

19. Mo ２ A catalyst containing C, which is capable of converting lignin into aromatic compounds in a yield of 80% or more.

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