Green method for preparing sustainable aviation fuel through propylene oligomerization-hydrogenation

Abstract

The invention belongs to the technical field of sustainable aviation fuel preparation processes, and provides a green method for preparing sustainable aviation fuel through propylene oligomerization-hydrogenation. The method comprises the following steps: dehydrating, desulfurizing and purifying green propylene, performing selective oligomerization in a fixed bed reactor by adopting a solid acid catalyst at the temperature of 70-180 DEG C, under the pressure of 2-5MPa and at the air speed of 1-3h <-1 > to prepare an olefin oligomer, and rectifying to obtain unreacted propylene and lt; c6 olefin is separated and mixed with fresh propylene for recycling, the obtained C9-C15 olefin passes through a fixed bed reactor, a nickel-based catalyst is adopted for catalytic hydrogenation, the temperature is controlled to be 60-150 DEG C, the pressure is controlled to be 1-3 MPa, the H2 / olefin molar ratio is controlled to be 2: 1-3: 1, the air speed is controlled to be 1-3 h <-1 >, it is ensured that olefin is completely saturated while cracking is avoided, after a product is subjected to gas-liquid separation, gas-phase H2 is recycled, and the C9-C15 olefin is recycled. And rectifying the liquid phase to obtain the sustainable aviation fuel meeting the ASTMD7566 standard.

Description

Technical Field

[0001] This invention belongs to the field of sustainable aviation fuel preparation technology, and relates to a method for producing sustainable aviation fuel by green propylene oligomerization-hydrogenation. Background Technology

[0002] Against the backdrop of global efforts to address climate change, the aviation industry, as one of the fastest-growing carbon-emitting sectors, is facing increasingly severe pressure to reduce emissions. Sustainable aviation fuel (SAF) is considered a key solution to achieving this goal. Currently, various technologies exist for obtaining SAF.

[0003] By converting waste oils and other materials into fuel, the amount of greenhouse gases released during traditional processing can be reduced, thus minimizing environmental impact. Through chemical processing methods, such as hydrogenation or transesterification, oxygen atoms in the raw materials are removed, and lipids can be converted into hydrocarbon-based mixtures suitable for aviation applications, thus exhibiting combustion characteristics similar to traditional aviation fuels. Chinese invention patent CN202511301085.1 discloses an apparatus and method for preparing sustainable aviation fuel from waste oils, involving dehydration and impurity removal, hydrogenation and deoxygenation, hydrogenation isomerization, and product separation and purification. This route is currently the mainstream route for producing SAF (Sports Air Fuel), but it is heavily reliant on special raw materials and is subject to certain limitations.

[0004] By utilizing agricultural residues, wood waste, and other biological materials, and through physical, chemical, or biological pretreatment, cellulose and hemicellulose are separated and the lignin structure is destroyed to improve enzymatic hydrolysis efficiency, saccharifying them into fermentable glucose and xylose. These substances are then fermented to produce intermediate products such as ethanol, which are then synthesized into hydrocarbon compounds that meet aviation fuel standards through processes such as pyrolysis, gasification, or catalytic conversion. Chinese invention patent CN202510094010.4 discloses a method for preparing sustainable aviation fuel component oil using biomass-based derivatives. Furfural is subjected to aldol condensation with 2,5-hexanedione to lengthen the carbon chain, obtaining an oxygenated aviation fuel precursor; this precursor is then pre-hydrogenated, followed by catalytic hydrodeoxygenation, catalytic hydrocracking, and catalytic isomerization, and fractionated to obtain the aviation fuel component oil. However, this process is lengthy, and the efficiency of the first aldol condensation reaction is too low. Chinese invention patent CN202510778198.4 discloses a method for producing sustainable aviation fuel from straw. The method involves first converting straw into syngas, then reacting the syngas with dimethyl ether through a two-stage catalyst to obtain ethanol, then converting the ethanol into ethylene, and finally converting the ethylene into aviation fuel. The overall process is too long, and the catalysts are expensive and have poor stability.

[0005] By directly capturing carbon dioxide from industrial emissions or the atmosphere, or by recycling industrial waste gases, hydrogen, etc., combined with carbon capture and storage technology, and the use of renewable energy, it is converted into raw materials for the production of SAF. Chinese Invention Patent CN202510038283.7 discloses a process for producing sustainable aviation fuel by capturing carbon dioxide from industrial boilers using by-product hydrogen in industry. Through steps such as Fischer-Tropsch synthesis and hydroisomerization, by-product hydrogen and carbon dioxide in industry are converted into sustainable aviation fuel. Although this technology not only reduces the concentration of carbon dioxide in the atmosphere but also provides a new way for the sustainable production of aviation fuel, the complexity of this technology is relatively high and the technology maturity still belongs to the experimental stage.

[0006] Despite the rapid expansion of the global SAF market scale and the continuous optimization of technical routes, the development of SAF also faces challenges such as tight raw material supply and high production costs. It is necessary to compare existing methods for producing SAF, such as Fischer-Tropsch synthesis, ester hydrogenation-isomerization, etc., to develop the advantages and potential challenges of new routes, and focus on whether the source of raw materials is sustainable, catalyst cost, reaction efficiency, and whether the product meets ASTM standards, etc. Summary of the Invention

[0007] The object of the present invention is to overcome the key defects of existing SAF production technologies, such as dependence on special raw materials, low product selectivity, high catalyst cost / poor stability, harsh hydrogenation process, and complex process, etc. A method is provided that uses green propylene as a raw material, first performs selective oligomerization with a solid acid catalyst to obtain C9-C15 olefins, and then performs hydrogenation with a nickel-based catalyst under mild conditions to produce sustainable aviation fuel.

[0008] The technical solution of the present invention: A method for producing sustainable aviation fuel by oligomerization-hydrogenation of green propylene, the steps are as follows: After dehydration and desulfurization purification of green propylene, in a fixed-bed reactor, using a solid acid catalyst, control the temperature at 70-180 °C, pressure at 2-5 MPa, and space velocity at 1-3 h -1 Under the condition, selectively prepare olefin oligomers; after the olefin oligomers are rectified, among them, unreacted propylene and olefins with <C6 are separated and mixed with fresh green propylene for recycling. The separated C9-C15 olefins are then passed through a fixed-bed reactor and catalytic hydrogenation is carried out using a nickel-based catalyst, controlling the temperature at 60-150 °C, pressure at 1-3 MPa, and space velocity at 1-3 h -1 Under the condition, the molar ratio of H2 to C9-C15 olefins is 2:1-3:1, ensuring that the C9-C15 olefins are completely saturated while avoiding cracking; after the product of catalytic hydrogenation is subjected to gas-liquid separation, the gaseous phase H2 is recycled, and the liquid phase is rectified to obtain sustainable aviation fuel meeting ASTM D7566 standards.

[0009] The green propylene sources are obtained by hydrogenating or electrolyzing carbon dioxide, by fermenting or catalytically converting biomass (such as vegetable oils and sugars), and by chemically recycling waste plastics (such as polypropylene) to decompose them and regenerate propylene monomers.

[0010] The solid acid catalyst is ZSM-5, Beta zeolite, or H3PW with a pore size of 0.5-0.7 nm and a Si to Al molar ratio of 30-100. 12 O 40 SO4 2- / ZrO2-Al2O3 is one type of ion exchange resin.

[0011] The nickel-based catalyst is a Ni-Mo catalyst supported on mesoporous Al2O3 modified with La2O3 or MgO, wherein the pore size of Al2O3 is 10-20 nm, the Ni loading is 10-15 wt%, and the molar ratio of Ni to Mo is 4:1-1:1.

[0012] The beneficial effects of this invention are: (1) This invention uses solid acid to achieve precise control of the oligomerization reaction of propylene, so that the product is highly concentrated in the C9-C15 (especially trimer to pentamer) aviation fuel fraction range, which greatly reduces the low-value C6 and C7 light fractions or the excessively heavy C18+ polymer. This high selectivity is directly converted into a higher yield of sustainable aviation fuel components, improving the efficiency of raw material utilization and process economy.

[0013] (2) Since the oligomers in the front end are mainly linear or single-branched olefins with relatively simple structures, the subsequent hydrogenation saturation reaction can be completed at lower temperatures and pressures. This significantly reduces equipment investment (reduced requirements for materials and pressure resistance), energy consumption, and operational safety risks.

[0014] (3) C9-C15 olefins obtained by selective oligomerization of propylene are mainly converted into isoalkanes after hydrogenation. These isoalkanes have excellent low-temperature fluidity, high energy density and good combustion characteristics, which fully meet the strict standards of aviation fuel and do not require complicated isomerization or cracking upgrading steps.

[0015] (4) Compared with routes that rely on Fischer-Tropsch synthesis or hydrogenation deoxygenation of ester-based oils, this technology uses propylene as a single, readily available raw material, and the supply chain is relatively simple. Attached Figure Description

[0016] Figure 1 This is a simplified process flow diagram for the production of sustainable aviation fuel from green propylene oligomerization and hydrogenation. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings and technical solutions.

[0018] Example 1 Bio-based propylene needs to be dehydrated and purified, and then in a fixed-bed reactor, using a ZSM-5 catalyst, controlling the temperature at 180 °C, pressure at 2 MPa, and space velocity at 3 h -1 to selectively oligomerize to produce olefin oligomers. After distillation, the unreacted propylene and C6 olefins are separated and mixed with fresh propylene for recycling. The obtained C9 to C15 olefins are then passed through a fixed-bed reactor. After analysis, the propylene conversion rate > 95%, and the C9-C15 olefin yield reaches 90%.

[0019] Example 2 Using the C9-C15 olefins obtained in Example 1 as raw materials, a NiMo catalyst supported on La2O3-modified mesoporous Al2O3 (Ni loading is 10 wt%, Ni-Mo molar ratio is 4:1) is used for catalytic hydrogenation, controlling the temperature at 60 °C, pressure at 1 MPa, H2 / olefin molar ratio at 2:1, and space velocity at 3 h -1 After the product is separated by gas-liquid separation, the gaseous H2 is recycled. After the liquid phase is distilled, it is found that its energy density is 44.1 MJ / kg, freezing point is -60 °C, density is 820 kg / m 3 (15 o C), viscosity is 7.6 mm 2 / s (-20 °C), meeting the sustainable aviation fuel standard of ASTM D7566, and the product yield reaches 99%.

[0020] Example 3 Carbon dioxide-based propylene needs to be dehydrated and purified, and then in a fixed-bed reactor, using a Beta zeolite catalyst, controlling the temperature at 70 °C, pressure at 5 MPa, and space velocity at 1 h -1 to selectively oligomerize to produce olefin oligomers. After distillation, the unreacted propylene and C6 olefins are separated and mixed with fresh propylene for recycling. The obtained C9 to C15 olefins are then passed through a fixed-bed reactor. After analysis, the propylene conversion rate > 90%, and the C9-C15 olefin yield reaches 85%.

[0021] Example 4 Using the C9-C15 olefins obtained in Example 3 as raw materials, a NiMo catalyst supported on MgO-modified mesoporous Al2O3 (Ni loading is 15 wt%, Ni-Mo molar ratio is 1:1) is used for catalytic hydrogenation, controlling the temperature at 150 °C, pressure at 3 MPa, H₂ / olefin molar ratio at 3:1, and space velocity at 1 h -1, after gas-liquid separation of the product, the gaseous H2 is recycled, and after rectification of the liquid phase, it is found by analysis that its energy density is 43.8 MJ / kg, freezing point -65 °C, density 830 kg / m 3 (15 o C), viscosity 7.5 mm 2 / s (-20 °C), a sustainable aviation fuel meeting ASTM D7566 standard, with a product yield of 98%.

[0022] Example 5 The chemical recycling of waste plastics to propylene requires dehydration and purification, and then in a fixed-bed reactor, using H3PW 12 O 40 catalyst, controlling the temperature at 140 °C, pressure at 3 MPa, and space velocity at 2 h -1 , selectively oligomerizing to prepare olefin oligomers. After rectification, the unreacted propylene and <C6 olefins are separated and mixed with fresh propylene for recycling. The obtained C9 to C15 olefins are then passed through a fixed-bed reactor. After analysis, the propylene conversion rate > 98%, and the C9-C15 olefin yield reaches 95%.

[0023] Example 6 Using the C9-C15 olefins obtained in Example 5 as raw materials, catalytic hydrogenation is carried out using a NiMo catalyst supported on La2O3-modified mesoporous Al2O3 (Ni loading is 15 wt%, Ni-Mo molar ratio is 4:1), controlling the temperature at 100 °C, pressure at 2 MPa, H2 / olefin molar ratio at 3:1, and space velocity at 2 h -1 , after gas-liquid separation of the product, the gaseous H2 is recycled, and after rectification of the liquid phase, it is found by analysis that its energy density is 44.5 MJ / kg, freezing point -70 °C, density 800 kg / m 3 (15 o C), viscosity 7.2 mm 2 / s (-20 °C), a sustainable aviation fuel product yield reaching 99%.

[0024] Example 7 Bio-based propylene requires dehydration and purification, and then in a fixed-bed reactor, using SO4 2- / ZrO2-Al2O3 catalyst, controlling the temperature at 180 °C, pressure at 5 MPa, and space velocity at 2 h -1 , selectively oligomerizing to prepare olefin oligomers. After rectification, the unreacted propylene and <C6 olefins are separated and mixed with fresh propylene for recycling. The obtained C9 to C15 olefins are then passed through a fixed-bed reactor. After analysis, the propylene conversion rate > 90%, and the C9-C15 olefin yield reaches 89%.

[0025] Example 8 Using the C9-C15 olefins obtained in Example 7 as raw materials, catalytic hydrogenation was carried out using a NiMo catalyst supported on La2O3-modified mesoporous Al2O3 (Ni loading of 10 wt%, Ni-Mo molar ratio of 3:1). The temperature was controlled at 120 °C, the pressure was 2 MPa, the H2 / olefin molar ratio was 3:1, and the space velocity was 2 h -1 , after the product was subjected to gas-liquid separation, the gaseous H2 was recycled. After the liquid phase was rectified, it was found by analysis that its energy density was 44.4 MJ / kg, the freezing point was -68 °C, and the density was 800 kg / m 3 (15 o °C), the viscosity was 7.1 mm 2 / s (-20 °C), which met the sustainable aviation fuel standard of ASTM D7566, and the product yield reached 97%.

[0026] Example 9 Bio-based propylene needs to be dehydrated and purified, and then in a fixed-bed reactor, using H3PW 12 O 40 catalyst, the temperature was controlled at 160 °C, the pressure was 3 MPa, and the space velocity was 2 h -1 , for the selective oligomerization to prepare olefin oligomers. After rectification, the unreacted propylene and <C6 olefins were separated and mixed with fresh propylene for recycling. The obtained C9 to C15 olefins were then passed through a fixed-bed reactor. After analysis, the propylene conversion rate > 93%, and the C9-C15 olefin yield reached 87%.

[0027] Example 10 Using the C9-C15 olefins obtained in Example 9 as raw materials, catalytic hydrogenation was carried out using a NiMo catalyst supported on MgO-modified mesoporous Al2O3 (Ni loading of 15 wt%, Ni-Mo molar ratio of 4:1). The temperature was controlled at 60 °C, the pressure was 1 MPa, the H2 / olefin molar ratio was 2:1, and the space velocity was 1 h -1 , after the product was subjected to gas-liquid separation, the gaseous H2 was recycled. After the liquid phase was rectified, it was found by analysis that its energy density was 44.5 MJ / kg, the freezing point was -67 °C, and the density was 790 kg / m 3 (15 o °C), the viscosity was 7.2 mm 2 / s (-20 °C), which met the sustainable aviation fuel standard of ASTM D7566, and the product yield reached 98%.

[0028] Example 11 Carbon dioxide-based propylene needs to be dehydrated and purified, and then in a fixed-bed reactor, using ZSM-5 catalyst, the temperature was controlled at 170 °C, the pressure was 5 MPa, and the space velocity was 2 h -1, olefin oligomers are prepared by selective oligomerization. After rectification, unreacted propylene and <C6 olefins are separated and mixed with fresh propylene for recycle use. The obtained C9 to C15 olefins are then passed through a fixed-bed reactor. After analysis, the propylene conversion rate > 89%, and the C9-C15 olefin yield reaches 85%.

[0029] Example 12 Using the C9-C15 olefins obtained in Example 11 as raw materials, a NiMo catalyst supported on La2O3-modified mesoporous Al2O3 (Ni loading is 10 wt%, Ni-Mo molar ratio is 1:1) is used for catalytic hydrogenation. The temperature is controlled at 100 °C, the pressure is 2 MPa, the H2 / olefin molar ratio is 1.5:1, and the space velocity is 2 h -1 , after the product is separated by gas-liquid separation, the gaseous H2 is recycled. After rectification of the liquid phase, analysis shows that its energy density is 45.0 MJ / kg, freezing point is -72 °C, and density is 830 kg / m 3 (15 o C), viscosity is 7.8 mm 2 / s (-20 °C), meeting the sustainable aviation fuel of ASTM D7566 standard, and the product yield reaches 99%.

[0030] Example 13 Bio-based propylene needs to be dehydrated and purified, and then in a fixed-bed reactor, an ion exchange resin catalyst is used. The temperature is controlled at 140 °C, the pressure is 3 MPa, and the space velocity is 2 h -1 , olefin oligomers are prepared by selective oligomerization. After rectification, unreacted propylene and <C6 olefins are separated and mixed with fresh propylene for recycle use. The obtained C9 to C15 olefins are then passed through a fixed-bed reactor. After analysis, the propylene conversion rate > 85%, and the C9-C15 olefin yield reaches 80%.

[0031] Example 14 Using the C9-C15 olefins obtained in Example 13 as raw materials, a NiMo catalyst supported on MgO-modified mesoporous Al2O3 (Ni loading is 15 wt%, Ni-Mo molar ratio is 4:1) is used for catalytic hydrogenation. The temperature is controlled at 80 °C, the pressure is 2 MPa, the H2 / olefin molar ratio is 2:1, and the space velocity is 1 h -1 , after the product is separated by gas-liquid separation, the gaseous H2 is recycled. After rectification of the liquid phase, analysis shows that its energy density is 44.6 MJ / kg, freezing point is -67 °C, and density is 800 kg / m 3 (15 o C), viscosity is 7.2 mm 2 / s (-20 °C), meeting the sustainable aviation fuel product yield reaches 97%.

Claims

1. A method for green propene oligomerization-hydrogenation to sustainable aviation fuel, characterized by, The steps are as follows: Green propylene needs to be purified by dehydration and desulfurization, and then, in a fixed bed reactor, a solid acid catalyst is used to control the temperature at 70-180 ℃, the pressure at 2-5 MPa, and the space velocity at 1-3 h -1 Under the conditions, olefin oligomers are selectively prepared. The olefin oligomers are separated by rectification, wherein the unreacted propylene and olefins less than C6 are separated and mixed with fresh green propylene for recycling, the obtained C9-C15 olefins are subjected to catalytic hydrogenation in a fixed bed reactor by using a nickel-based catalyst under the conditions of a temperature of 60-150 ℃, a pressure of 1-3 MPa, a space velocity of 1-3 h -1 The molar ratio of H2 and C9-C15 olefins is 2:1-3:1, which ensures complete saturation of C9-C15 olefins while avoiding cracking; the product after catalytic hydrogenation is subjected to gas-liquid separation, the gaseous H2 is recycled, and the liquid phase is subjected to rectification to obtain sustainable aviation fuel meeting the standard of ASTM D7566.

2. The method of green propene oligomerization-hydrogenation to sustainable aviation fuel according to claim 1, characterized in that, The green propylene source is obtained by carbon dioxide hydrogenation or carbon dioxide electrolysis, through biomass fermentation or catalytic conversion, or through chemical recycling of waste plastics to decompose and regenerate propylene monomer.

3. The method of green propene oligomerization-hydrogenation to sustainable aviation fuel according to claim 1, characterized in that, The solid acid catalyst is one of ZSM-5, Beta zeolite, H3PW 12 O 40 、SO4 2- / ZrO2-Al2O3, ion exchange resin with a pore size of 0.5-0.7 nm and a molar ratio of Si to Al of 30-100.

4. The method of green propene oligomerization-hydrogenation to sustainable aviation fuel according to claim 1, characterized in that, The nickel-based catalyst is a mesoporous Al2O3 supported Ni-Mo catalyst modified by adding La2O3 or MgO, wherein the pore size of Al2O3 is 10-20 nm, the Ni loading is 10-15 wt%, and the molar ratio of Ni to Mo is 4:1-1:1.

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