Method for converting lignin into sustainable aviation kerosene through carbon chain extension strategy

Abstract

The invention discloses a method for converting lignin into sustainable aviation kerosene through a carbon chain extension strategy, and relates to the field of biomass resource high-valued conversion, and the method comprises the following steps: in a high-pressure reaction kettle, carrying out a reaction on a lignin raw material, a catalyst and a solvent at 300 DEG C in a normal-pressure nitrogen atmosphere for 6 hours, and depolymerizing lignin into a high-carbon-value phenolic oil solution with increased carbon number, carrying out rotary evaporation to remove the solvent, adding a non-polar solvent and the catalyst in the second step, heating to 300 DEG C, and reacting for 3 hours to obtain the sustainable aviation fuel. The reaction process has the advantages that efficient depolymerization of lignin and carbon chain in-situ extension modification and deoxidation of phenolic products are realized through step-by-step catalytic reaction. The obtained high-carbon-value phenolic compound (the carbon number is C8-C17) can be directly used as a sustainable aviation kerosene component or a raw material for synthesis of fine chemicals, and the system value is effectively improved. Compared with a traditional lignin depolymerization and deoxidation process, the method breaks through the technical bottleneck of insufficient carbon chain length in the lignin conversion process through depolymerization-recarburization-deoxidation multi-stage reaction coupling, has the advantages of raw material greenness, process high efficiency and product high value, and provides a new way for preparing biofuels and chemicals from lignin.

Description

Technical Field

[0001] The present application relates to the field of high-value conversion of biomass resources, and in particular to a method for converting lignin into sustainable aviation fuel through a carbon chain extension strategy. Background Art

[0002] Lignocellulose is an abundant biomass resource in nature, primarily composed of three components: cellulose, hemicellulose, and lignin. Its wide availability, low cost, and environmental friendliness make it an ideal raw material for the production of biofuels and high-value-added chemicals. Lignin is a complex polymer composed of phenylpropane structural units connected by various chemical bonds. It is rich in carbon and has a high energy density. Furthermore, lignin, the second-largest renewable aromatic polymer in nature after cellulose, accounts for 15%-30% of the dry weight of plant biomass, with an annual production of up to 50 million tons. As the only natural resource capable of scalably providing aromatic ring structures, its efficient conversion is crucial for replacing fossil energy and promoting the development of green chemistry.

[0003] In recent years, lignin depolymerization technology has made significant progress, but it still faces some challenges. Traditional lignin depolymerization methods such as acid-base catalysis and pyrolysis have many problems in practical applications. The acid-base catalysis method requires a large amount of catalyst, and the product separation is difficult, which easily produces a large amount of waste liquid and pollutes the environment; the pyrolysis method often requires high temperature and pressure, high energy consumption, and the selectivity and quality of the product are difficult to be effectively controlled. Therefore, the development of an efficient, green and economical lignin depolymerization and reuse technology has become an important research direction in this field to meet the needs of high-value conversion of biomass resources.

[0004] The technology used in this patent to catalyze the depolymerization of lignin by solvent decomposition through a carbon chain extension strategy and further hydrodeoxygenate it for use in sustainable aviation fuel has significant advantages and innovations. First, this technology does not require the purification of intermediate products, which greatly simplifies the process flow and reduces production costs and energy consumption. The coupling of multi-stage reactions such as the depolymerization of lignin and the carbon chain extension of phenolic products can be completed in one catalytic solvent depolymerization reaction, thereby improving the reaction efficiency and the added value of the product. Secondly, by carrying out the reaction under a nitrogen atmosphere at normal pressure, the use of relatively expensive hydrogen as a reaction atmosphere is avoided. The high-carbon value phenolic compounds obtained are then further hydrodeoxygenated for value-added utilization to obtain cycloalkanes / aromatics sustainable aviation fuel, providing a clean and renewable energy solution. Therefore, the present invention provides a green new method for converting lignin into sustainable aviation fuel through a carbon chain extension strategy. Summary of the Invention

[0005] The present application provides a method for converting lignin into sustainable aviation fuel through a carbon chain extension strategy.

[0006] This application adopts the following technical solutions:

[0007] A method for converting lignin into sustainable aviation fuel through a carbon chain extension strategy, the synthesis method comprising the following steps:

[0008] (1) In a high-pressure reactor at 270°C-300°C, the lignin raw material, solvent and catalyst are reacted under normal pressure nitrogen conditions for 6-12 hours to depolymerize the lignin into a high-carbon value phenolic oil solution

[0009] (2) The phenol oil solution obtained in step (1) is distilled to remove the solvent, and a non-polar solvent and a hydrodeoxygenation catalyst are added. The mixture is heated in a high-pressure reactor at 200-300° C. under a hydrogen atmosphere for 1-4 hours. After the reaction, vacuum filtration is performed to obtain a mixed product such as cycloalkanes / aromatics, which is a sustainable jet fuel precursor.

[0010] The catalyst described in step (1) is a Mo-based catalyst such as MoC, MoO3, etc., wherein the reduction temperature of MoO3 is one of 300°C, 400°C and 500°C.

[0011] The feed ratios of the reaction catalyst and raw materials in step (1) are 2:1, 1:1 and 1:2.

[0012] In step (1), the volume ratio of lignin to solvent is 1:100-15:100.

[0013] The solvent in step (1) is one or more of methanol, ethanol, and 1,4-dioxane.

[0014] The lignin raw material in step (1) is one or more of enzymatically hydrolyzed lignin, solvent-extracted lignin, alkali lignin, or lignin derived from straw biogas fermentation.

[0015] The reaction temperature of step (1) is 270-300°C.

[0016] The reaction time of step (1) is 6-12h.

[0017] The catalyst in step (2) is a supported metal catalyst, the active component of which is one or more of the metals or metal oxides of Mn, Fe, Co, Ni, Mo, Ru, Pd, W, and Pt, with a content of 0.1% to 10%; the carrier is one or more of activated carbon, silica, tungsten trioxide, aluminum oxide, niobium pentoxide, and molecular sieves.

[0018] The non-polar solvent in step (2) is one or more of alkanes, cyclohexane, aromatic hydrocarbons, and water.

[0019] In step (2), the volume ratio of the phenolic oil to the solvent is 1:100-1:1.

[0020] The reaction temperature of step (2) is 200-300°C.

[0021] The hydrogen pressure in step (2) is 3-8 MPa.

[0022] The reaction time of step (2) is 1-4 hours.

[0023] At least one of the above technical solutions adopted in this application can achieve the following beneficial effects:

[0024] This application adopts a carbon chain extension strategy to convert lignin into sustainable aviation fuel. In the first step of lignin depolymerization, there is no need to purify and separate the intermediate products, which greatly simplifies the process flow and reduces production costs and energy consumption. The coupling of multi-stage reactions such as lignin depolymerization and carbon chain extension of phenolic products can be completed in one catalytic solvent depolymerization reaction, thereby improving the reaction efficiency and the added value of the product. It breaks through the limitations of traditional step-by-step processes and improves the reaction efficiency and the added value of the product. In contrast, existing technologies such as acid-base catalysis and thermal decomposition often require complex multi-step processes, and product separation is difficult. It is easy to produce a large amount of waste liquid or require harsh conditions such as high temperature and high pressure, resulting in problems such as high energy consumption, high cost, and environmental pollution.

[0025] The second step, hydrodeoxygenating high-carbon-value phenolic compounds to fuel precursors such as cycloalkanes and aromatics, allows the resulting phenolic oil to be directly fed into the reaction, eliminating the separation, purification, and redissolution of phenolic intermediates required in traditional processes and significantly streamlining the process. This process also allows for efficient hydrodeoxygenation of the reactants, achieving a yield approaching 100%. The resulting mixed hydrocarbon product, characterized by low oxygen content, high calorific value, and excellent low-temperature fluidity, can be directly used as sustainable jet fuel. The short-chain alkane byproducts generated simultaneously can be easily separated and reused as process fuel, completing the complete resource cycle.

[0026] The technical solution of this application is suitable for renewable lignin, achieving the green nature of the raw material and conforming to the concept of sustainable development. Furthermore, through the multi-stage coupling of "depolymerization-carburization-deoxygenation" reactions, it overcomes the dual bottlenecks of insufficient carbon chain length and deoxygenation efficiency of lignin-derived phenols. It has the significant advantages of high single-pass conversion rate, effectively reduced energy consumption, and no acidic waste liquid emissions, providing key technical support for the industrialization of lignin-based aviation fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 .Spectrum of the carbon chain-extended jet fuel precursor obtained by converting lignin with the MoO3-ethanol system. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the specific embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] Example 1

[0031] (1) Preparation of lignin depolymerization catalyst MoO3-400

[0032] The MoO3-400 catalyst was synthesized by the following method: Untreated ammonium molybdate was transferred to a muffle furnace and calcined at 400°C for 4 hours to obtain pure MoO3. The resulting MoO3 was then placed in a quartz reaction tube and heated from room temperature to 400°C at a rate of 5°C / min under a H2 atmosphere at a flow rate of 80 mL / min. The temperature was then maintained at 400°C for 12 hours. After cooling to room temperature, the catalyst was passivated with 5 wt% O2 / N2 for 12 hours to obtain the MoO3-400 catalyst, which was then used in lignin depolymerization reactions.

[0033] (2) Lignin depolymerization into high carbon number phenolic oils

[0034] First, 1.0g of lignin, 0.5g of MoO3-400, and 100mL of ethanol were weighed and placed into a 300mL Parr reactor. The reactor was sealed and flushed six times with high-purity nitrogen. The atmosphere was then evacuated to a gauge pressure of 0 MPa. A heating program was then initiated at 400 rpm, raising the temperature to 280°C and allowing the reaction to proceed for 6 hours. After the reaction was complete, the reaction mixture was cooled to room temperature, evacuated, and vacuum filtered to obtain the liquid product and solid insoluble matter from the lignin depolymerization reaction, which were subsequently analyzed. The solvent in the liquid product was then spin-dried to obtain the high-carbon phenol oil.

[0035] Chromatographic analysis results showed that the lignin conversion rate reached 91% and the yield of high-carbon value phenolic compounds reached 20%.

[0036] (3) Phenol oil hydrodeoxygenation catalyst Ru / WO x Preparation

[0037] Ru / WO x The catalyst was synthesized by the following method: first, WO was prepared by alcohol maturation method. xCarrier. First, 100 mL of ethanol was measured, and 3 g of WCl6 was added to it. Then, it was stirred vigorously for 10 minutes to completely dissolve. The solution was then transferred to a hydrothermal reactor and hydrothermaled at 160°C for 36 hours. After cooling to room temperature, the dark blue precipitate was centrifuged and washed three times with ethanol. Finally, it was freeze-dried for 7 hours to obtain WO. x Next, the incipient wetness impregnation method was used to impregnate WO x The Ru / WO was loaded on the substrate with 5 wt% Ru and reduced in pure H2 atmosphere at 400℃ for 4 h. After the reduction, the substrate was aged in 10% O2 / N2 for 6 h to obtain the corresponding Ru / WO. x The catalyst was used in subsequent experiments.

[0038] (4) Hydrodeoxygenation of phenolic oil to obtain sustainable aviation fuel

[0039] Weigh 0.1g of phenolic oil and 0.1g of Ru / WOx in 10mL of dodecane and transfer the entire mixture to a reactor. After sealing, purge the reaction vessel three times with high-purity N2 to ensure complete air displacement. Then, purge the reaction vessel three times with high-purity H2. Finally, fill the reaction vessel with 2MPa of H2. After a period of quiescence to ensure a leak-proof chamber, incubate the reaction at 280°C at 400rpm for 3 hours. After cooling to room temperature, vacuum filter the reaction vessel to obtain the liquid product.

[0040] Example 2

[0041] (1) Preparation of lignin depolymerization catalyst MoO3-300

[0042] The MoO3-300 catalyst was synthesized by the following method: First, a certain amount of untreated ammonium molybdate was transferred to a muffle furnace and calcined at 400°C for 4 hours to obtain pure MoO3. The resulting MoO3 was then placed in a quartz reaction tube and heated from room temperature to 300°C at a rate of 5°C / min under a H2 atmosphere at a controlled flow rate of 80 mL / min. The temperature was then maintained at 300°C for 12 hours. After cooling to room temperature, the catalyst was passivated with 5 wt% O2 / N2 for 12 hours to obtain the MoO3-300 catalyst, which was then used in lignin depolymerization reactions.

[0043] (2) Lignin depolymerization to high carbon number phenolic oils

[0044] First, 1.0g of lignin, 0.5g of MoO3-300, and 100mL of ethanol were weighed and placed into a 300mL Parr reactor. The reactor was sealed and flushed six times with high-purity nitrogen. The atmosphere was then evacuated to a gauge pressure of 0 MPa. A heating program was then initiated at 400 rpm, raising the temperature to 280°C and allowing the reaction to proceed for 6 hours. After the reaction was complete, the reaction mixture was cooled to room temperature, evacuated, and vacuum filtered to obtain the liquid product and solid insoluble matter from the lignin depolymerization reaction, which were subsequently analyzed. The solvent in the liquid product was then spin-dried to obtain the high-carbon phenol oil.

[0045] (3) Preparation of Ni / m-WO3 catalyst for hydrodeoxygenation of phenolic oil

[0046] The Ni / m-WO3 catalyst was synthesized by the following method: First, 2g of Na2WO4·2H2O was weighed and dispersed in 40mL of ultrapure water. Ultrasonication was performed for 5 minutes to completely dissolve the solution. The solution was then transferred to a room-temperature stirrer and 5mol / L nitric acid solution was slowly added while stirring. Stirring was continued for 30 minutes, and the solution was then hydrothermally heated at 180°C for 3 hours. After the reaction, the precipitate was removed, washed with ultrapure water several times by centrifugation until neutral, and then vacuum-dried at 60°C overnight. After complete drying, the solution was calcined at 350°C for 2 hours. After calcination, the solution was transferred to a tube furnace and maintained at 400°C for 4 hours under a flow of H2 (80mL / min). After cooling to room temperature, the solution was aged in a 10% O2 / N2 atmosphere for 6 hours before being removed for later use. This yielded the m-WO3 support. Next, m-WO3 was loaded with 5 wt% Ni using the incipient wetness impregnation method and reduced in a pure H2 atmosphere at 400°C for 4 h. After the reduction, it was aged in 10% O2 / N2 for 6 h to obtain the corresponding Ni / m-WO3 catalyst for subsequent experiments.

[0047] (4) Hydrodeoxygenation of phenolic oil to obtain sustainable aviation fuel

[0048] Weigh 0.1g of phenolic oil and 0.1g of Ni / m-WO3 in 10mL of dodecane and transfer the entire mixture to a reactor. After sealing, purge the reaction vessel three times with high-purity N2 to ensure complete air displacement. Then, purge the reaction vessel three times with high-purity H2. Finally, fill the reaction vessel with 2MPa of H2. After a period of quiescence to ensure a leak-proof chamber, incubate the reaction at 280°C at 400rpm for 3 hours. After cooling to room temperature, vacuum filter the reaction vessel to obtain the liquid product.

[0049] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for converting lignin into sustainable aviation fuel through a carbon chain extension strategy, characterized in that: The synthesis method comprises the following steps: (1) In a high-pressure reactor at 270° C. to 300° C., a lignin raw material, a solvent, and a catalyst are reacted under normal pressure nitrogen for 6 to 12 hours to depolymerize the lignin into a high-carbon phenolic oil solution; (2) distilling the phenol oil solution obtained in step (1) to remove the solvent, adding a non-polar solvent and a hydrodeoxygenation catalyst, heating the solution in a high-pressure reactor at 200-300° C. under a hydrogen atmosphere for 1-4 hours, and vacuum filtering the solution after the reaction to obtain a mixed product such as cycloalkanes / aromatics, which can further be used to obtain sustainable aviation fuel.

2. The method according to claim 1, characterized in that The catalyst in step (1) is MoC x , Mo-based catalysts such as MoO3, wherein the reduction temperature of MoO3 is one of 300°C, 400°C and 500°C.

3. The method according to claim 1, characterized in that The feed ratios of the reaction catalyst and raw materials in step (1) are 2:1, 1:1 and 1:

2.

4. The method according to claim 1, wherein In step (1), the volume ratio of lignin to solvent is 1:100-15:

100.

5. The method according to claim 1, characterized in that The solvent in step (1) is one or more of methanol, ethanol, and 1,4-dioxane.

6. The method according to claim 1, characterized in that The lignin raw material in step (1) is one or more of enzymatically hydrolyzed lignin, solvent-extracted lignin, alkali lignin, or lignin derived from straw biogas fermentation.

7. The method according to claim 1, characterized in that The reaction temperature of step (1) is 270-300°C.

8. The method according to claim 1, characterized in that The reaction time of step (1) is 2-12h.

9. The method according to claim 1, characterized in that The catalyst in step (2) is a supported metal catalyst, the active component of which is one or more of the metals or metal oxides of Mn, Fe, Co, Ni, Mo, Ru, Pd, W, and Pt, with a content of 0.1% to 10%; the carrier is one or more of activated carbon, silica, tungsten trioxide, aluminum oxide, niobium pentoxide, and molecular sieves.

10. The method according to claim 1, characterized in that The non-polar solvent in step (2) is one or more of alkanes, cyclohexane, aromatic hydrocarbons, and water.

11. The method according to claim 1, wherein In step (2), the volume ratio of the phenolic oil to the solvent is 1:100-1:

1.

12. The method according to claim 1, characterized in that The reaction temperature of step (2) is 200-300°C.

13. The method according to claim 1, wherein The hydrogen pressure in step (2) is 3-8 MPa.

14. The method according to claim 1, wherein The reaction time of step (2) is 1-4 hours.

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