Method for preparing high energy density fuel using lignin oil as a single raw material

Abstract

The application discloses a preparation method of fuel, comprising the following steps: (1) preparing a lignin oil; (2) taking the lignin oil obtained in the step (1) as a single raw material, adding a catalyst with a core-shell structure, and reacting under certain conditions to obtain an oxygen-free fuel precursor; and (3) adding hydrogen to the oxygen-free fuel precursor obtained in the step (2) to obtain the fuel. The application further discloses the fuel obtained by the preparation method.

Description

Technical Field

[0001] This invention belongs to the field of fuel technology, specifically relating to a method for preparing high-energy, high-density fuel using lignin oil as a single raw material. Background Technology

[0002] Fuel density and calorific value are key factors determining spacecraft flight performance. High-energy-density liquid hydrocarbon fuels can be used in turbojet, ramjet, rocket, and combined-fuel engines. The development of the aerospace industry has placed higher demands on high-density fuels: on the one hand, they require fuels to provide more propulsive kinetic energy (i.e., higher density and higher volumetric calorific value, density > 0.85 g / mL) within a given fuel tank volume; on the other hand, they require safe use in lower temperature environments, i.e., good low-temperature fluidity and good thermal stability. High-energy-density fuel is an abbreviation for high-density liquid hydrocarbon fuels. RJ-4 (bridged tetrahydromethyldicyclopentadiene dimer) and JP-10 (hanging tetrahydrodicyclopentadiene) are classic petroleum-based high-energy-density fuels, widely recognized for their excellent overall properties. They are typically synthesized from petroleum-based feedstocks such as cyclopentadiene or methylcyclopentadiene. However, feedstock sources are limited, and these fuels produce large amounts of CO2 during combustion. Exploring green high-energy-density fuels is of great technological significance.

[0003] Lignin is one of the sources of pure natural aromatic compounds. It is a three-dimensional amorphous macromolecule composed of various cross-linked phenylpropane (C3-C6) units such as p-hydroxyphenyl, guaiacol, and eugenyl, linked by ether bonds (β-O-4, α-O-4, 4-O-5, etc.) and carbon-carbon bonds (β-5, 5-5, etc.). The annual industrial production of lignin can reach 50 million tons, and reports on the synthesis of high-density fuels from lignin have been increasing in recent years. The literature Journal of Energy Chemistry 77(2023)452–460 reports the use of lignin oil and externally added cyclopentanol for alkylation and hydrodeoxygenation to obtain high-energy-density fuels. Patent CN111218308 A discloses the preparation of 2,5-hexanedione from biomass raw materials, followed by the preparation of oxygen-containing organic compounds from 2,5-hexanedione through aldol condensation and hydrogenation, and then hydrodeoxygenation to obtain high-density fuels. CN116676098A discloses a method for preparing high-energy-density fuels in a one-pot process using biomass phenols and added cyclic alcohols (cyclopentanol, cyclohexanol). Other literature such as Catalysis Today 365(2021)235–240; Chemical Engineering Science 207(2019)441–447; ACS Sustainable Chem.Eng.2021,9,7112-7119; Fuel 97(2012)560–568; EnergyFuels Chemical Engineering Science Methods for preparing high-energy-density fuels using lignin as a raw material have also been reported in Angew. Chem. Int. Ed. 2019, 58, 12154 and Sustainable Energy Fuels, 2022, 6, 1616–1624.

[0004] However, these methods have the following problems: 1. The raw materials used are mostly one or a few specific molecules of lignin, requiring a raw material separation step. This is not only complex and results in low yield, but also leads to raw material waste and limited raw material sources. 2. Other components need to be added as raw materials to promote the reaction. These additional components are mostly petroleum-based, increasing the complexity of raw material sources. 3. The high-density fuel precursor contains oxygen, requiring harsh conditions for hydrodeoxygenation to obtain the high-density fuel. This step is not only cumbersome but also reduces product yield and places higher demands on equipment. 4. Due to the limited variety of raw materials, the high-energy-density fuel products are mostly composed of one or two components, resulting in a need to improve the overall performance of the product. Currently, liquid fuels with a density exceeding 1.0 g / mL are rare. 5. The use of acidic catalysts such as concentrated sulfuric acid results in significant pollution.

[0005] The present invention is proposed to solve the above problems. Summary of the Invention

[0006] The preparation method of this invention uses lignin oil as a single raw material and utilizes a newly synthesized core-shell structured catalyst to prepare a high-energy-density fuel precursor in a one-pot series process. The obtained fuel precursor is oxygen-free and similar to classic petroleum-based high-density fuel precursors. Then, simple and mild hydrogenation yields a saturated alkane-based classic petroleum-based high-density fuel. The method of this invention has widely available raw materials, a simple synthesis process, an oxygen-free fuel precursor, mild hydrogenation conditions, a three-dimensional fuel structure, complementary components, and a fuel density greater than 0.96 g / mL. -1 .

[0007] The technical solution of the present invention is as follows:

[0008] The first aspect of the present invention discloses a method for preparing a fuel, comprising the following steps: (1) preparing lignin oil; (2) using the lignin oil obtained in step (1) as a single raw material, adding a catalyst with a core-shell structure, and reacting under certain conditions to obtain an oxygen-free fuel precursor; (3) hydrogenating the oxygen-free fuel precursor obtained in step (2) to obtain the fuel.

[0009] Preferably, the lignin oil in step (1) is obtained by cracking or hydrogenating lignin sulfonate, beech, poplar, birch or corn stalks or one or more.

[0010] Preferably, the catalyst with a core-shell structure comprises: metal nanoparticles, a non-acidic spherical core, and an acidic spherical outer shell, wherein the metal nanoparticles are loaded on the spherical core. The core and shell walls have hollow cavities. The core and shell can be regular spherical shells or irregular spherical shells, such as ellipsoidal shells, flattened spherical shells, or other irregular spherical shells.

[0011] Preferably, the core shell wall has pores with a diameter of 0.5nm-30nm, the average diameter of the hollow cavity inside the core shell wall is 5-200nm, and the thickness of the core shell wall is 5-100nm; the outer shell wall also has pores with a diameter that gradually decreases from the outside to the inside, from 5nm-100nm to 0.5nm-30nm, and the thickness of the outer shell wall is 5-500nm.

[0012] Preferably, the core is one or more of silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, magnesium oxide, calcium oxide, zinc oxide, or pure silicon molecular sieve, and the metal nanoparticles are one or more of the same, with the metal nanoparticles accounting for 5wt% to 50wt% of the core; the outer shell is one or more molecular sieves, one or more metal oxides, or a composite of one or more metal oxides and silicon dioxide, or a composite of one or more molecular sieves and silicon dioxide.

[0013] Preferably, the core-shell structured catalyst comprises: Ni / SiO2@NbWOx, Ni / SiO2@Al-MCM-41, Au / Silicalite-1@WO3, Ni / TiO2@Al-SBA-15, RuNiCu / ZrO2@Al-SBA-16, NiFe / MgO@Ti-MCM-41, Ni / SBA-15@HY, Ni / SiO2@Hβ, Ir / SBA-16@HZSM-5, NiCo / SiO2@Al2O3, Pt / M CM-48@Nb2O5, RuNiCu / ZrO2@SiO2-Al2O3, NiFe / MgO@CsTPA, Pt / ZnO@HfTPA / MCM-41, RuNi / CeO2@SiO2-Nb2O5, RhF e / MCM-41@MOF-808-2.5SO4, PtCu / MCM-22@HfTPA, RuMo / SiO2@SnTPA, RuNiCu / SiO2@ZrTPA, NiCoMo / Si-CeOx@SO4 2- / ZrO2、NiZn / Ce-MgO x @ITQ、NiIr / Ce-MgO x @KIT-6, Au / Silicalite-1@Mordenite, Ni / SiO2@MMT-K10, Ni / TiO2@HPW / MCM-41. The above expressions a / b@c, where a / b before @ indicates that metal nanoparticle a is loaded on the core b; after @ indicates the outer shell, and c indicates the outer shell composition; the above expressions a / b@c / d, where a / b before @ indicates that metal nanoparticle a is loaded on the core b; after @ indicates the outer shell, and c / d indicates a composite of outer shell components c and d.

[0014] Preferably, the reaction temperature in step (2) is 150℃~350℃, the hydrogen pressure is 2~6MPa, the reaction time is 5~30h, and the catalyst accounts for 5wt%~20wt% of the mass of the reactants.

[0015] Preferably, the conditions for the hydrogenation reaction of the oxygen-free fuel precursor in step (3) are: temperature of 60℃~180℃, hydrogen pressure of 2~6MPa, reaction time of 2~10h, and catalyst accounting for 5wt%~20wt% of the mass of the oxygen-free fuel precursor.

[0016] Preferably, the catalyst is one or more of the following: Pd / C, Ni / SiO2, NiCo / MCM-41, PtO, RuNiCu / SBA-15, NiFe / SBA-16, Pt / C, RuNi / SiO2, RhFe / MCM-41, PtCu / HZSM-5, RuMo / Hβ, Pd / SAPO-11, Ni / HY, Ru / Al2O3, Rh / Al2O3-SiO2, Ni / Nb2O5, and Ni / Al-MCM-41.

[0017] The second aspect of this invention discloses a fuel obtained by the aforementioned preparation method, the density of which is greater than 0.96 g·mL. -1 Its freezing point is below -50℃; its kinetic viscosity is less than 10.90 mm. 2 / s (20℃); its calorific value is greater than 39.0 MJ / Kg.

[0018] The beneficial effects of this invention are:

[0019] 1. The preparation method of this invention uses lignin oil as a single raw material, avoiding the single raw material separation process and complex platform molecular reconstruction process. Furthermore, it eliminates the need for external fossil or other biomass raw materials, making the raw material sources simple, abundant, green, and sustainable. The preparation process utilizes a newly developed core-shell structured catalyst, achieving multi-step tandem direct preparation of the fuel precursor under single-pot conditions, avoiding multiple intermediate product separation and transfer processes, and simplifying the preparation process.

[0020] 2. The lignin oil used in the preparation method of this invention can be obtained by direct refining (cracking and / or hydrolysis) of one or more of lignin sulfonates, beech, poplar, birch, or corn stalks; lignin oils from different raw materials can undergo similar or mutual reactions to prepare high-density fuel precursors, with arbitrary mixing ratios. The composition of the lignin oil is determined by its source; it can be a single-source lignin oil or a mixture of lignin oils from different sources, thus the synthesized fuel is a mixture containing multiple components, allowing for complementary advantages between the components.

[0021] 3. The preparation method of this invention uses a newly developed catalyst with a core-shell structure to catalyze the production of oxygen-free fuel precursors containing only double bonds from lignin oil as a single raw material. The conversion rate of lignin oil can reach 100%, and the yield of high-density fuel precursors can reach over 70%, with a maximum of 98%.

[0022] 4. The newly developed core-shell structured catalysts of this invention include: Ni / SiO2@NbWOx, Ni / SiO2@Al-MCM-41, Au / Silicalite-1@WO3, Ni / TiO2@Al-SBA-15, RuNiCu / ZrO2@Al-SBA-16, NiFe / MgO@Ti-MCM-41, Ni / SBA-15@HY, Ni / SiO2@Hβ, Ir / SBA-16@HZSM-5, NiCo / SiO2@Al2O3, Pt / MCM-48@Nb2O5, RuNiCu / ZrO2@SiO2-Al2O3, NiFe / MgO@CsTPA, Pt / ZnO@HfTPA / MCM-41, RuNi / CeO2@SiO2-Nb2O5, R hFe / MCM-41@MOF-808-2.5SO4, PtCu / MCM-22@HfTPA, RuMo / SiO2@SnTPA, RuNiCu / SiO2@ZrTPA, NiCoMo / Si-CeOx@SO4 2- / ZrO2、NiZn / Ce-MgO x @ITQ、NiIr / Ce-MgO x @KIT-6, Au / Silicalite-1@Mordenite, Ni / SiO2@MMT-K10, Ni / TiO2@HPW / MCM-41. The newly developed core-shell structured catalyst and its preparation method are described in patent CN2024110013158.

[0023] 5. The preparation method of this invention yields a fuel precursor that is oxygen-free, containing only C=C single bonds and unsaturated C=C double bonds. Hydrogenation is carried out under mild conditions and is relatively easy to achieve. The final fuel molecule is a fuel mixture with a structure similar to classic petroleum-based JP-10 or RJ-4, with complementary components. The resulting fuel has a high density, greater than 0.96 g / mL. -1 It exhibits excellent low-temperature properties, with a freezing point below -50℃; its kinetic viscosity is less than 10.90 mmHg. 2 / s (20℃), the minimum can reach 1.90mm. 2 / s (20℃); its calorific value is greater than 39.0MJ / Kg, with a maximum of 43.2MJ / Kg.

[0024] 6. The preparation method of this invention uses a one-pot series process, which can directly synthesize high-density fuel from lignin oil. However, the newly developed core-shell structured catalyst has a lower hydrogenation effect than traditional hydrogenation catalysts, resulting in a lower yield. Existing catalytic hydrogenation methods can achieve higher yields by converting fuel precursors into high-energy, high-density fuels. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail below with reference to specific embodiments. Unless otherwise specified, the raw materials used in the embodiments are all commercially available products; unless otherwise specified, the processes used are all conventional processes in the art.

[0026] Example 1: Preparation of fuel precursors.

[0027] (1) Preparation of lignin oil: 2.0 g of lignin sulfonate, 0.20 g of Ru / C, and 20 mL of methanol were added to a 100 mL stainless steel autoclave with an internal Teflon insert and mechanical stirring. The autoclave was sealed, the air was replaced three times with nitrogen, and 3 MPa of H2 was added. The mixture was then heated to 250 °C for 12 h under magnetic stirring. After the reaction was complete, the solvent was evaporated by rotary evaporation at 40 °C to obtain crude lignin oil. The mixture was then etherified in 10 mL of dimethyl carbonate in the presence of 100 mg of Cs2CO3 at 180 °C for 3 h. The solid was filtered, the solvent was evaporated, and the mixture was extracted with petroleum ether to remove the polymer, thus obtaining lignin oil.

[0028] (2) 25g of lignin oil from step (1) and 2.00g of core-shell catalyst were added to a high-pressure reactor and the air was replaced with nitrogen three times. Hydrogen gas at 4MPa was introduced and the mixture was mechanically stirred at 600rpm / min and reacted at 250℃ for 10h. When the reaction was completed and the temperature dropped to room temperature, the catalyst was separated for analysis. The results showed that the conversion rate of lignin oil was 100% and the yield of fuel precursor was 90%.

[0029] The core-shell catalyst used in step (2) is Ni / SiO2@NbWOx. The applicant has filed a separate patent application for the catalyst preparation method.

[0030] Examples 1-25: Preparation of fuel precursors.

[0031] (1) The preparation of lignin oil is shown in Table 1.

[0032] (2) Same as in Example 1, the lignin oil obtained in step (1) is selected from core-shell structured catalysts such as Ni / SiO2@NbWOx, Ni / SiO2@Al-MCM-41, Au / Silicalite-1@WO3, Ni / TiO2@Al-SBA-15, RuNiCu / ZrO2@Al-SBA-16, NiFe / MgO@Ti-MCM-41, Ni / SBA-15@HY, Ni / SiO2@Hβ, Ir / SBA-16@HZSM-5, and NiCo / SiO2@Al 2O3, Pt / MCM-48@Nb2O5, RuNiCu / ZrO2@SiO2-Al2O3, NiFe / MgO@CsTPA, Pt / ZnO@HfTPA / MCM-41, RuNi / CeO2@SiO2-Nb2O5 , RhFe / MCM-41@MOF-808-2.5SO4, PtCu / MCM-22@HfTPA, RuMo / SiO2@SnTPA, RuNiCu / SiO2@ZrTPA, NiCoMo / Si-CeOx@SO4 2- / ZrO2、NiZn / Ce-MgO x @ITQ、NiIr / Ce-MgO x @KIT-6, Au / Silicalite-1@Mordenite, Ni / SiO2@MMT-K10, Ni / TiO2@HPW / MCM-41, etc., were used as catalysts (if the core is bimetallic, the molar ratio is 1:20 to 20:1; for trimetallic catalysts, the molar ratio is 1:20:1 to 20:1:20), and other parameters are the same as in Example 1. The results of reactants and their amounts, catalysts and their amounts, reactant conversion rates, reaction temperatures, reaction times, and fuel precursor yields are listed in Table 1.

[0033] Table 1. Precursors for fuel synthesis from lignin oil

[0034]

[0035]

[0036] As shown in Table 1, the conversion rate of lignin oil was 100%, and the yield of fuel precursors was 70-95%.

[0037] Using the above-obtained fuel precursors as raw materials, and Pd / C, Ni / SiO2, NiCo / MCM-41, PtO, RuNiCu / SBA-15, NiFe / SBA-16, Pt / C, RuNi / SiO2, RhFe / MCM-41, PtCu / HZSM-5, RuMo / Hβ, Pd / SAPO-11, Ni / HY, Ru / Al2O3, Rh / Al2O3-SiO2, Ni / Nb2O5, Ni / Al-MCM-41, etc. as catalysts, the metal loading of the prepared catalysts is 1wt% to 20wt%, the bimetallic molar ratio is 1:10 to 10:1, the trimetallic molar ratio is 1:20:1 to 20:1:20, and the SiO2 / Al2O3 ratio of the molecular sieves is in the range of 10 to 200. The fuel precursors are then gently hydrogenated to prepare fuel.

[0038] Examples 26-50: Preparation of high-energy, high-density fuels.

[0039] The fuel precursors obtained in Examples 1-25 were used to prepare fuels through mild hydrogenation. The fuel precursors and catalysts obtained in Examples 1-25 were added together to an autoclave (corresponding to Examples 26-50, respectively). Air was purged three times with nitrogen, followed by the introduction of hydrogen. The mixture was mechanically stirred and reacted at a certain temperature for a period. After the reaction was complete and the temperature dropped to room temperature, the catalyst was separated. The fuel precursor conversion rate was 100%. The reactants and their amounts, catalyst and its amount, reactant conversion rate, reaction temperature, and reaction time are shown in Table 2. As can be seen from Table 2, the fuel precursor conversion rate was 100%, and the fuel yield was greater than 90%.

[0040] Table 2. Fuel Preparation by Hydrogenation of Fuel Precursors

[0041]

[0042]

[0043] As shown in Table 2, the conversion rate of the fuel precursor is 100%, and the fuel yield is not less than 90%.

[0044] Example 51: Fuel Performance Test

[0045] The fuel obtained in Example 26, according to the national standard GB2540-81 "Determination of Density of Petroleum Products", had a density of 1.18 g·mL⁻¹. -1 According to the national standard GB2430-81 "Determination of Freezing Point of Jet Fuel", its freezing point was measured to be below -70℃; according to the national standard GB265-88 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products", its dynamic viscosity was measured to be 1.95 mm. 2 / s (20℃); its calorific value was determined to be 42.1 MJ / Kg according to the national standard GB / T384-81 "Determination of Calorific Value of Petroleum Products".

[0046] The fuel obtained in Example 50, according to the national standard GB2540-81 "Determination of Density of Petroleum Products", had a density of 1.31 g·mL⁻¹. -1 According to the national standard GB2430-81 "Determination of Freezing Point of Jet Fuel", its freezing point was measured to be below -50℃; according to the national standard GB265-88 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products", its dynamic viscosity was measured to be 3.35 mm. 2 / s (20℃); its calorific value was determined to be 41.2 MJ / Kg according to the national standard GB / T384-81 "Determination of Calorific Value of Petroleum Products".

[0047] The fuel densities obtained in other embodiments were all greater than 0.96 g·mL⁻¹. -1 The highest value was 1.30 g / mL. -1 The freezing point is below -50℃, with a minimum of -110℃; its kinetic viscosity is less than 10.90 mm. 2 / s (20℃), minimum is 1.90mm 2 / s (20℃); its calorific value is greater than 39.0MJ / Kg, with a maximum of 43.2MJ / Kg.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a fuel, characterized in that, The process includes the following steps: (1) preparing lignin oil; (2) using the lignin oil obtained in step (1) as a single raw material, adding a catalyst with a core-shell structure, and reacting under certain conditions to obtain an oxygen-free fuel precursor. (3) Hydrogenate the oxygen-free fuel precursor obtained in step (2) to obtain the fuel; The catalyst with a core-shell structure comprises: metal nanoparticles, a non-acidic spherical core, and an acidic spherical shell, wherein the metal nanoparticles are loaded on the spherical core; The core shell has pores with a diameter of 0.5 nm-30 nm, the average diameter of the hollow cavity inside the core shell is 5-200 nm, and the thickness of the core shell is 5-100 nm; the outer shell also has pores with a diameter that gradually decreases from the outside to the inside, from 5 nm-100 nm to 0.5 nm-30 nm, and the thickness of the outer shell is 5-500 nm. The core is silicon dioxide, and the metal nanoparticles account for 5 wt% to 50 wt% of the core; the core-shell structure catalyst is one or more of Ni / SiO2@NbWOx, Ni / SiO2@Al-MCM-41, Ni / SiO2@Hβ, NiCo / SiO2@Al2O3, and Ni / SiO2@MMT-K10; Step (2) The reaction temperature is 150℃ ~ 350℃, the hydrogen pressure is 2 ~ 6 MPa, and the reaction time is 5 ~ 30h; the catalyst accounts for 5wt% ~ 20wt% of the reactant mass.

2. The preparation method according to claim 1, characterized in that, The lignin oil in step (1) is obtained by cracking or hydrogenating lignin sulfonate, beech, poplar, birch or corn stalks or one or more of these.

3. The preparation method according to claim 1, characterized in that, The conditions for the hydrogenation reaction of the oxygen-free fuel precursor in step (3) are: temperature of 60℃ ~ 180℃, hydrogen pressure of 2 ~ 6 MPa, and reaction time of 2 ~ 10h; the catalyst in step (3) is one or more of Pd / C, Ni / SiO2, NiCo / MCM-41, RuNiCu / SBA-15, NiFe / SBA-16, Pt / C, RuNi / SiO2, RhFe / MCM-41, PtCu / HZSM-5, RuMo / Hβ, Pd / SAPO-11, Ni / HY, Ru / Al2O3, Rh / Al2O3-SiO2, Ni / Nb2O5, and Ni / Al-MCM-41, and the catalyst accounts for 5wt% ~ 20wt% of the mass of the oxygen-free fuel precursor.

Images