Method for preparing high-density aviation fuel through pyrolysis oil hydrogenation

Abstract

The invention relates to the field of aviation fuel synthesis, and discloses a method for preparing high-density aviation fuel through pyrolysis oil hydrogenation, which comprises the following steps: preparing a supported molecular sieve catalyst; the cracking oil is subjected to solvent extraction, distillation, aromatic hydrocarbon extraction and mild hydrogenation pretreatment to separate a refined cracking oil component; and performing catalytic hydrogenation conversion reaction on the refined pyrolysis oil component to prepare the high-density aviation fuel. The high-dispersion supported molecular sieve catalyst is prepared through molecular sieve ion exchange, alkali modification and optimized hydrolysis load, and is used for hydrogenation reaction of pyrolysis oil components under the solvent-free condition, the aromatic hydrocarbon conversion rate is high, and the produced naphthenic mixture has the characteristics of high density and low freezing point; the fuel can be directly used as advanced aviation fuel or a traditional aviation fuel additive to improve the volume calorific value of the fuel; the preparation method disclosed by the invention is mild in reaction condition, simple in implementation route, high in yield of the high-density polycyclic hydrocarbon compound and wide in industrial prospect.

Description

Technical Field

[0001] The invention relates to the field of aviation fuel synthesis, and in particular to a method for preparing high-density aviation fuel by hydrogenating pyrolysis oil. Background Art

[0002] Despite the growing focus on innovation with more sustainable energy sources, carbon emissions from industry and transportation remain one of the main contributors to climate change. In the past decade, research on the synthesis of biojet fuels using lignocellulosic platforms has gained widespread attention. However, due to the high production cost of biojet fuels, traditional fossil jet fuels still dominate the aviation fuel sector. Therefore, improving the thermochemical conversion performance of fossil fuels at this stage is crucial to achieving carbon reduction targets.

[0003] Cycloalkanes are the main components of advanced aviation fuels and are widely used in military aircraft and propulsion systems. Due to their high density or volumetric energy content, the use of cycloalkanes as aviation fuel can significantly increase the aircraft's range, payload, and flight speed without changing the fuel tank volume. These characteristics have obvious advantages in practical applications. However, the current price of high-density aviation fuel is higher than that of traditional aviation fuel, which to some extent limits its application in civil aviation. Therefore, it is necessary to develop and utilize a wider range of available raw materials to synthesize more cost-effective high-density aviation fuels similar to JP-10.

[0004] Pyrolysis oil is usually a component obtained through coal or petroleum cracking processing units. Some pyrolysis oils have the typical characteristics of being rich in aromatics, such as coal tar, catalytic cracking oil slurry, ethylene tar, etc. By molecular tailoring to obtain a pyrolysis oil component with a suitable structure, hydrogenation of the pyrolysis oil component is expected to obtain a high-density aviation fuel composed of polycyclic cycloalkanes. However, this hydrogenation process must try to solve the problems of low activity of conventional catalysts, poor hydrogenation saturation capacity of metal sulfide catalysts such as NiMoS / Al2O3 and CoMoS / Al2O3, harsh reaction conditions, and the need for high temperature and high pressure to achieve complete hydrogenation. At the same time, the cost of the catalyst must also be considered to facilitate industrial prospects. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a method for preparing high-density aviation fuel by hydrogenating pyrolysis oil, and its technical scheme is as follows: A method for preparing high-density aviation fuel by hydrogenating pyrolysis oil comprises the following steps: (1) Preparation of supported molecular sieve catalysts The supported molecular sieve catalyst includes a molecular sieve carrier and a transition metal active component, and its preparation includes the following two steps: The first step is ion exchange and alkali treatment of the molecular sieve carrier: the molecular sieve is added to the NH4NO3 aqueous solution and stirred, the solid precipitate after centrifugation is dried, the obtained sample is calcined in air, alkali solution is added, and it is treated in a hydrothermal reactor and washed with deionized water until neutral; The second step is to prepare the catalyst by loading the transition metal with urea hydrolysis method: distilled water is added to the transition metal salt to form a solution, and then the molecular sieve carrier and urea are dispersed in the solution, stirred at room temperature and placed in a hydrothermal reactor for treatment. After the hydrothermal reaction is completed, the mixed solution is filtered and washed with deionized water. After the precipitate is dried, it is reduced at high temperature in a H2 atmosphere; (2) The pyrolysis oil is separated into refined pyrolysis oil components through solvent extraction, distillation, aromatic extraction, and mild hydrogenation pretreatment units; (3) Catalytic hydrogenation reaction of refined pyrolysis oil components to produce high-density aviation fuel.

[0006] Furthermore, the molecular sieve carrier in step (1) is one or a mixture of two or more of Y, Beta, ZSM-5, and MOR molecular sieves.

[0007] Furthermore, the transition metal active component in step (1) is one or a combination of Ni, Co, Mo, Sn, Fe, and Cu.

[0008] Furthermore, the mass of the transition metal active component in step (1) is 0.1 wt% to 10.0 wt% of the mass of the supported molecular sieve catalyst.

[0009] Furthermore, the first stirring step of step (1) is continuous stirring at 60° C. for 0.5 to 2 h; the hydrothermal temperature of the hydrothermal reactor is 100 to 115° C., and the treatment time is 4 h.

[0010] Furthermore, in the second step of step (1), the mass ratio of the molecular sieve carrier to urea is (4:1) to (4:5); the hydrothermal temperature of the hydrothermal reactor is 80 to 100°C, and the treatment time is 8 hours; after the precipitate is dried, it is reduced in a H2 atmosphere at 400°C for 2 to 3 hours, and the heating rate is 1.5°C / min.

[0011] Furthermore, the cracking oil in step (2) is refined coal tar, catalytic oil slurry, ethylene tar or other petroleum components with low impurity content and rich in aromatics.

[0012] Furthermore, the refined pyrolysis oil component separated by pretreatment in step (2) has a boiling point of 180 to 300°C.

[0013] Furthermore, the reaction conditions for the catalytic hydrogenation conversion reaction of the refined pyrolysis oil component in step (3) to prepare high-density aviation fuel are: temperature 160-240° C., hydrogen pressure 1-5 MPa, time 0.5-6 h, and the mass ratio of reactants to catalyst is (4:1)-(20:1).

[0014] Furthermore, the high-density aviation fuel obtained by the reaction in step (3) is mainly composed of C8-C 14 Side-chain polycyclic hydrocarbons, of which the content of hydrogenated aromatics is >99%.

[0015] Compared with the prior art, the present invention mainly has the following beneficial technical effects: 1. The present invention adopts strategies such as molecular sieve ion exchange, base-modified carrier and optimized hydrolysis loading to successfully prepare highly dispersed and uniformly distributed transition metal nanoparticle catalysts, realize the interaction between metal and carrier, and effectively retain the strong acidity of molecular sieve, with excellent catalytic performance and hydrogenation rate.

[0016] 2. The process route of the present invention can carry out the hydrogenation reaction of the pyrolysis oil components in a solvent-free environment and at a relatively low temperature, and can directly generate C8-C 14 A mixture of branched cycloalkanes with an aromatic conversion rate of more than 99%, which efficiently converts the cracking oil components into high-density aviation fuel.

[0017] 3. The high-density aviation fuel prepared by the present invention has a density of up to 0.90-0.95 g / mL and a freezing point below -60°C. The fuel performance is comparable to that of JP-10, so it is an advanced aviation fuel with broad prospects and high cost-effectiveness.

[0018] 4. The high-density aviation fuel prepared by the present invention can be directly used as an advanced aviation fuel or as a traditional aviation fuel additive to increase the volume calorific value of the fuel.

[0019] 5. The preparation method of the present invention has mild reaction conditions, a simple implementation route, and a high yield for high-density polycyclic hydrocarbon compounds, and has good industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the X-ray diffraction pattern of the Beta molecular sieve obtained in Example 1 of the present invention.

[0021] Figure 2 These are transmission electron microscope images and high-resolution transmission electron microscope images of the Beta molecular sieve loaded with Ni obtained in Example 1 of the present invention.

[0022] Figure 3 This is a GCMS chart of the distillation separation product and the hydrogenation product of a refinery's rich aromatic oil in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in combination with the embodiments, drawings and tables. Obviously, the described embodiments are exemplary and are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0024] 1. Preparation of supported molecular sieve catalyst (1) Add 5-8 g of molecular sieve to 200 mL of 1 M NH4NO3 aqueous solution, stir continuously at 60°C for 0.5-2 h, dry the solid precipitate after centrifugation, repeat this process three times, and calcine the obtained sample in air for 3 h; then add 100 ml of 1 mol / L NaOH solution to the obtained sample, treat it in a hydrothermal autoclave at 100-115°C for 4 h, and wash it with deionized water until it is neutral.

[0025] (2) About 1 g of nickel nitrate with a carrier mass fraction of 10 wt% was added to 50 mL of distilled water, and then 2 g of Beta molecular sieve carrier and 1.5 g of urea were dispersed in the mixed solution. After stirring at room temperature for 3 h, the mixed solution was placed in a stainless steel hydrothermal reactor and hydrothermally heated at 100 ° C for 8 h. After the hydrothermal reaction, the mixed solution was filtered, washed with deionized water, and dried at 90 ° C. Finally, the dried precipitate was reduced at 400 ° C for 3 h in a H2 atmosphere with a heating rate of 1.5 ° C / min.

[0026] 2. A refinery distills rich aromatic oil to obtain refined pyrolysis oil components A fraction with a boiling point range of 190-280°C was separated from the aromatic oil of a refinery by using a real boiling point distillation apparatus. The distillation was carried out under a reduced pressure of 10Pa.

[0027] 3. Catalytic hydrogenation of refined pyrolysis oil components to produce high-density aviation fuel (1) Treatment before reaction: 20 g of the refined pyrolysis oil component and 2 g of the supported molecular sieve catalyst prepared above were added into a 100 mL reactor.

[0028] (2) Leak test: Inject high-pressure N2 gas into the reactor for leak test.

[0029] (3) Replacement gas: Replace the air in the reactor with N2 for 3 to 5 times, with a pressure less than 2 MPa.

[0030] (4) Filling H2: Fill the reactor with 5MPaH2; (5) Heating: The reactor was heated by a heater, the constant temperature was 200° C., and the heating time was 30 min.

[0031] (6) Carrying out the reaction: Start magnetic stirring under constant temperature and pressure conditions, the stirring speed is 300 rpm, and the reaction time is 3 h.

[0032] Figure 1 This is the X-ray crystal diffraction diagram of the treated Beta molecular sieve obtained in Example 1. It can be seen that the Beta molecular sieve after ion exchange and alkali treatment has a high degree of crystallinity. High crystallinity indicates that the obtained molecular sieve has high purity, low content of other impurities, good stability in catalytic reactions, and is not prone to crystal transformation.

[0033] Figure 2 To obtain a typical transmission electron microscope image of the Beta molecular sieve loaded with metal Ni in Example 1. Figure 2 It can be seen that the Ni element forms highly dispersed nanoparticles on the molecular sieve support wall, with an average size of about 3 to 5 nm. High-resolution transmission electron microscopy images further show that the Ni nanoparticles are distributed on the Beta support, with plane spacings of d=0.217nm, 0.262nm, and 0.352nm, corresponding to Ni 0 (111), (200) and (220) planes. This indicates that the metal Ni is highly dispersed on its surface and has a high metal dispersion, which is conducive to exposing more metal active sites.

[0034] Figure 3 To obtain the GCMS total ion chromatogram of the refined pyrolysis oil component and the component after catalytic hydrogenation of the refined pyrolysis oil component in Example 1. Figure 3 It can be seen that the product distribution has changed greatly. After catalytic hydrogenation of the refined cracking oil components, the product distribution is concentrated in a smaller peak position, which proves that the aromatic ring is hydrogenated during the catalytic process.

[0035] Comparative Example 1 A conventional supported Ni / Al2O3 catalyst was loaded into a 100 mL reactor, and the refined cracking oil component was catalytically hydrogenated according to the method in Example 1. Example 2

[0036] The difference from Example 1 is that Y-type molecular sieve is selected in the preparation process of the supported molecular sieve catalyst. Example 3

[0037] The difference from Example 1 is that ZSM-5 molecular sieve is selected in the preparation process of the supported molecular sieve catalyst. Example 4

[0038] The difference from Example 1 is that the preparation process of the supported molecular sieve catalyst uses MOR molecular sieve.

[0039] Liquid products were analyzed for light solubles and CHC products using an Agilent 7890 / 5973 gas chromatograph / mass spectrometer (GC / MS). Specific parameters were: HP-5MS column (column length 60m, inner diameter 250μm, film thickness 0.25μm); carrier gas was He, flow rate 1.2mL / min; GC column box starting temperature 60℃, light component (model compound) heating rate 5 (or 10)℃ / min, final temperature 300℃, maintained for 10 (or 6)min; MS used EI as ion source, split ratio 20:1, solvent delay 1.5min, quadrupole mass analyzer, bombardment voltage 70eV, m / z acquisition range 33-550, database NIST11.

[0040] The refined pyrolysis oil components and the reaction conversion rates and product analyses of Example 1 and Comparative Example 1 are shown in Table 1.

[0041] Table 1 Refined pyrolysis oil components and reaction conversion rates and product analysis of Example 1 and Comparative Example 1 ; As shown in Table 1, the refined cracking oil component mainly contains aromatic compounds. Among them, benzene compounds account for 5.0%, aromatic olefins account for 12.6%, indene and its homologues account for 14.3%, naphthalene and its homologues account for 57.9%, biphenyl organic matter accounts for 7.0%, and other hydrocarbons account for 3.2%, which can be regarded as a good potential precursor of high-density aviation fuel. In addition, after catalytic hydrogenation, all aromatics in Example 1 are converted into hydrogenated aromatic compounds, including 14.9% cyclohexane derivatives, 9.9% octahydroindene, 7.3% bicyclohexane, 57.7% decahydronaphthalene and its homologues and 10.2% other cycloalkyl compounds. The content of aromatics and cycloalkanes is crucial to achieving the energy density required for jet fuel; it is well known that reducing the aromatic content (increasing the hydrogen content) in the fuel can significantly reduce the particle emissions of the aircraft. Reliable jet fuel can maintain a high volume energy density without aromatics. Therefore, from the perspective of product distribution, Example 1 fully meets the requirements of high-density aviation fuel. However, under the same conditions, the products generated in Comparative Example 1 mainly include tetralin (50.6%), biphenyl (4.5%), naphthalene (7.3%), dihydroindene (13.8%), benzene (18.0%) and other products (5.8%), and the yield of unsaturated and partially saturated products is greater than 94%. Comparative Example 1 is difficult to achieve efficient hydrogenation conversion of refined pyrolysis oil components at relatively low temperatures, and the resulting product is difficult to meet the standards of high-density jet fuel.

[0042] Table 2 Physical and chemical properties of different fuels ; In order to evaluate the potential of the fuel oil prepared by the invention as a high-performance aviation fuel, the obtained alkane mixture was further tested, and the specific fuel performance results are shown in Table 2. The density of the alkane mixture fuel of Examples 1-4 is as high as 0.91-0.93 g / mL, the freezing point is lower than -60°C, the flash point is as high as 58-60°C, and the net volume calorific value is 39.5-40.7 MJ / L. Its fuel performance is comparable to that of JP-10, and it is an advanced aviation fuel with broad prospects, economical and efficient.

[0043] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing high-density aviation fuel by hydrogenating pyrolysis oil, characterized in that: The following steps are involved: (1) Preparation of supported molecular sieve catalysts The supported molecular sieve catalyst includes a molecular sieve carrier and a transition metal active component, and its preparation includes the following two steps: The first step is ion exchange and alkali treatment of the molecular sieve carrier: the molecular sieve is added to the NH4NO3 aqueous solution and stirred, the solid precipitate after centrifugation is dried, the obtained sample is calcined in air, alkali solution is added, and it is treated in a hydrothermal reactor and washed with deionized water until neutral; The second step is to prepare the catalyst by loading the transition metal with urea hydrolysis method: distilled water is added to the transition metal salt to form a solution, and then the molecular sieve carrier and urea are dispersed in the solution, stirred at room temperature and placed in a hydrothermal reactor for treatment. After the hydrothermal reaction is completed, the mixed solution is filtered and washed with deionized water. After the precipitate is dried, it is reduced at high temperature in a H2 atmosphere; (2) The pyrolysis oil is separated into refined pyrolysis oil components through solvent extraction, distillation, aromatic extraction, and mild hydrogenation pretreatment units; (3) Catalytic hydrogenation reaction of refined pyrolysis oil components to produce high-density aviation fuel.

2. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The molecular sieve carrier in step (1) is one or a mixture of two or more of Y, Beta, ZSM-5, and MOR molecular sieves.

3. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The transition metal active component in step (1) is one or a combination of Ni, Co, Mo, Sn, Fe, and Cu.

4. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The mass of the transition metal active component in step (1) is 0.1 wt% to 10.0 wt% of the mass of the supported molecular sieve catalyst.

5. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The first step of stirring in step (1) is continuous stirring at 60° C. for 0.5 to 2 h; the hydrothermal temperature of the hydrothermal reactor is 100 to 115° C., and the treatment time is 4 h.

6. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: In the second step of step (1), the mass ratio of the molecular sieve carrier to urea is (4:1) to (4:5); the hydrothermal temperature of the hydrothermal reactor is 80 to 100° C., and the treatment time is 8 hours; after the precipitate is dried, it is reduced in a H2 atmosphere at 400° C. for 2 to 3 hours, and the heating rate is 1.5° C. / min.

7. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The cracking oil in step (2) is refined coal tar, catalytic oil slurry, ethylene tar or other petroleum components with low impurity content and rich in aromatics.

8. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The refined pyrolysis oil component separated by pretreatment in step (2) has a boiling point of 180 to 300°C.

9. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The reaction conditions for the catalytic hydrogenation conversion reaction of the refined cracking oil component in step (3) to prepare high-density aviation fuel are: temperature 160-240° C., hydrogen pressure 1-5 MPa, time 0.5-6 h, and a mass ratio of reactants to catalyst of (4:1)-(20:1).

10. The method for preparing high-density aviation fuel by hydrogenating pyrolysis oil according to claim 1, characterized in that: The components of the high-density aviation fuel obtained by the reaction in step (3) are mainly C8-C 14 Side-chain polycyclic hydrocarbons, of which the content of hydrogenated aromatics is >99%.

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