Method for preparing low freezing point bio-jet fuel from waste oil

Abstract

The application relates to the field of biomass energy and chemical technology, and specifically discloses a method for preparing low-freezing-point bio-jet fuel from waste oil, which comprises the following steps: (1) mixing waste oil with an oil-soluble catalyst precursor, adding a vulcanizing agent, and feeding the mixture into a slurry bed reactor to perform reaction, so as to obtain reaction effluent; (2) directly feeding the reaction effluent into a hot high-pressure separator to perform gas-liquid preliminary separation without cooling, so as to obtain a liquid-solid mixture; (3) separating the liquid-solid mixture through an inorganic ceramic membrane filter, so as to obtain clean intermediate oil; (4) sequentially feeding the clean intermediate oil into a hydrofining reactor and a hydroisomerization reactor to perform reaction, so as to obtain reaction products; and (5) separating and fractionating the reaction products. Through the creative coupling of the slurry bed and high-temperature membrane filtration, the bottleneck of the traditional technical route is broken, and the waste oil can be used to produce high-quality bio-jet fuel in a large scale, efficiently and economically.

Description

Technical Field

[0001] This application relates to the fields of biomass energy and chemical technology, and more specifically, it relates to a method for preparing low-pour-point biojet fuel from waste oil. Background Technology

[0002] Bio-jet fuel is aviation kerosene prepared from renewable resources such as waste animal and vegetable oils and waste cooking oil. With increasing global pressure on carbon emissions in the aviation industry, bio-jet fuel, as an important direction for sustainable aviation fuel (SAF), has received widespread attention. The core characteristic of low-pour-point bio-jet fuel is its low pour point, ensuring it remains fluid even at high altitudes and low temperatures, preventing fuel system blockages, and thus improving flight safety and applicability.

[0003] Although the hydrotreating process (HEFA) has established itself as the mainstream method in biofuel production, the industry is caught in a dilemma between "fixed bed" and "slurry bed" when dealing with waste oil as a specific feedstock.

[0004] On the one hand, traditional fixed-bed processes are extremely sensitive to the purity of raw materials. High concentrations of colloids, free fatty acids, and impurities such as Ca, Na, Fe, P, and Cl carried in waste oils will rapidly deposit on the catalyst surface, leading to pore blockage, permanent poisoning of active centers, and a surge in bed pressure drop. This causes the catalyst lifespan, which was originally several years, to plummet to just a few weeks, and frequent catalyst replacements increase production costs. In addition, the strong exothermic nature of oil deoxygenation makes it easy for localized "runaway temperatures" to form in the fixed bed, causing sintering and coking, making it difficult to balance safety and efficiency.

[0005] On the other hand, while slurry bed reactors have become potential alternatives due to their excellent heat transfer performance and high tolerance to inferior feedstocks, they are hampered by the bottleneck of "solid-liquid separation." Micro- and nano-scale catalyst particles are difficult to remove completely through conventional sedimentation or centrifugation and are prone to escape to downstream processes, causing fatal contamination to expensive hydrorefining / isomerization precious metal catalysts.

[0006] Regarding the aforementioned technologies, the inventors believe that the fixed-bed process requires high purity of raw materials and cannot directly process waste oils with high impurities. Although the slurry-bed process can process inferior raw materials, the catalyst separation problem makes it difficult to effectively connect with downstream refining units. This contradiction between "raw material adaptability" and "catalyst separation" seriously restricts the economic efficiency and large-scale application of waste oil resource utilization. Therefore, it is urgent to propose a solution to solve the above-mentioned technical problems. Summary of the Invention

[0007] In order to develop an innovative coupling process that can both handle high-impurity components and completely block the entrainment of fine particles, this application provides a method for preparing low-pour-point bio-jet fuel from waste oil based on the coupling of slurry bed and high-temperature membrane filtration.

[0008] This application provides a method for preparing low-pour-point bio-jet fuel from waste oil, which adopts the following technical solution: A method for preparing low-pour-point biojet fuel from waste oil includes the following steps: (1) The waste oil is mixed with the oil-soluble catalyst precursor, a sulfiding agent is added, and the mixture is fed into a slurry bed reactor for hydrodeoxygenation and impurity removal reaction to obtain the reaction effluent; (2) The reaction effluent obtained in step (1) is directly fed into a hot high-pressure separator for preliminary gas-liquid separation without cooling, to obtain gaseous products and liquid-solid mixtures; (3) The liquid-solid mixture obtained in step (2) is filtered and separated by an inorganic ceramic membrane filter to obtain clean intermediate oil and retained catalyst slurry; (4) The clean intermediate oil obtained in step (3) is passed through a hydrorefining reactor and a hydroisomerization reactor in sequence for deep refining and isomerization dewaxing reaction to obtain the reaction product; (5) Separate and fractionate the reaction products obtained in step (4) to obtain bio-jet fuel products.

[0009] By adopting the above technical solution, the slurry bed reactor is not sensitive to impurities such as colloids and metals in the raw materials, and can directly treat waste oil with high acid value and high impurity content, thus solving the problem of poor raw material adaptability of the fixed bed process. First, in step (1), through the action of the oil-soluble catalyst precursor, the main hydrogenation, deoxygenation, and decarbonylation reactions of fatty acid glycerides in waste oil are completed, and oxygen is removed in the form of H2O, CO2, CO, etc., to generate straight-chain alkanes. This is the key step in converting oil into hydrocarbon fuels. Moreover, the oil-soluble catalyst precursor will form highly active nano-sized sulfide particles under reaction conditions. These particles have a huge specific surface area and can preferentially adsorb and convert impurities such as Ca, Na, and P in the raw materials, fixing them on the catalyst particles, thereby "purifying" the raw materials.

[0010] Next, after the initial gas-liquid separation in the hot high-pressure separator in step (2), step (3) uses an inorganic ceramic membrane filter to perform high-temperature cross-flow filtration on the liquid-solid mixture rich in nano-catalysts and impurities. This can almost 100% retain the nano-catalyst particles and fixed impurities generated in step (1), ensuring the "cleanliness" of the downstream feed. This step fundamentally solves the industry problem of catalyst particles penetrating, contaminating and poisoning the downstream expensive precious metal catalysts in the slurry bed process. Moreover, the design of "reaction effluent without cooling" avoids the huge energy waste of cooling high-temperature materials to room temperature for separation and then reheating them to the reaction temperature in the traditional process. This achieves the cascade utilization of energy and significantly reduces the total energy consumption of the system.

[0011] Then, in step (4), a highly active catalyst is used in the hydrorefining reactor to further remove residual trace amounts of oxygen, sulfur, nitrogen, and other heteroatoms from the intermediate oil, ensuring that the product meets strict fuel specifications. In the hydroisomerization reactor, straight-chain alkanes (with high pour points) are selectively converted into branched isoalkanes, whose pour points are much lower than their straight-chain homologues, thus stabilizing the pour point of the final product below -47°C to meet the low-temperature fluidity requirements for high-altitude flight. Finally, in step (5), product purification is achieved through separation and fractionation, separating out higher-value products.

[0012] By combining "slurry bed impurity tolerance with high-temperature membrane precision separation," the industry-wide challenge of "raw material adaptability" and "catalyst separation" is perfectly solved. The pre-positioned slurry bed protects the delicate fixed-bed catalyst, significantly extending its lifespan from several months in traditional processes to over two years, ensuring long-term, stable, and continuous operation of the unit. Simultaneously, this preparation method forms a highly efficient "staged purification, each performing its specific function" model. The slurry bed handles coarse processing and impurity removal, while the fixed bed handles fine processing and quality improvement, maximizing resource utilization and reducing catalyst costs. Furthermore, the "hot feed" design significantly reduces energy consumption, enhancing the overall economic competitiveness of the process. Therefore, this method for preparing low-pour-point bio-jet fuel from waste oil, through the creative coupling of slurry bed and high-temperature membrane filtration, breaks through the bottlenecks of traditional technical routes, enabling large-scale, efficient, and economical utilization of waste oil to produce high-quality bio-jet fuel.

[0013] Preferably, in step (1), the amount of oil-soluble catalyst precursor added is 0.1-2% of the mass of waste oil, and its active metal is selected from any one or more of molybdenum, nickel, cobalt and tungsten.

[0014] By adopting the above technical solution, the added amount of oil-soluble catalyst precursor can ensure a sufficient number of active centers to efficiently complete the deoxygenation and impurity removal tasks, without placing a heavy burden on the subsequent inorganic ceramic membrane filter. As for the selection of the above active metal, under the high temperature and pressure and hydrogen atmosphere of the slurry bed reactor, it will be sulfidated by the help of the sulfiding agent to form highly dispersed nano-sized transition metal sulfide active particles. These newly formed nanoparticles can not only fully contact the oil molecules to carry out a huge interfacial reaction, but also preferentially adsorb and react with impurities such as Ca, Na, and P in the raw materials to achieve deep removal of impurities. The overall effect is relatively excellent and stable.

[0015] Preferably, in step (1), the oil-soluble catalyst precursor is a composite system of molybdenum naphthenate and nickel isooctanoate, and the molar ratio of nickel to molybdenum is (0.25-0.35):1.

[0016] By adopting the above technical solution, with molybdenum as the main catalyst and nickel as the co-catalyst, a sufficient number of Ni-Mo-S active centers can be formed at the above molar ratio, thereby ensuring that the catalyst activity reaches its optimal level and possesses good stability, enabling thorough deoxygenation and impurity removal without increasing the burden on the downstream fixed bed. At the same time, the highly dispersed Ni-Mo-S nanoparticles have a huge specific surface area, which can more effectively adsorb and fix metal impurities in the raw materials, and promote a more thorough hydrodeoxygenation reaction, providing ideal raw materials for subsequent reactions.

[0017] Preferably, in step (1), the reaction conditions of the slurry bed reactor are 280-360℃, 8-15MPa, and liquid hourly space velocity (LHSV) of 0.5-2h. -1 .

[0018] By adopting the above technical solution, 280-360℃ can provide sufficient reaction driving force, balancing reaction rate and selectivity. This ensures efficient breakage of CO and C=O bonds in waste oil molecules for deep deoxygenation, while effectively inhibiting excessive cracking and coking, providing stability assurance for the entire long-term operation. The high-pressure conditions of 8-15MPa provide a stable hydrogenation environment for the highly exothermic deoxygenation reaction, ensuring reaction depth, preventing temperature runaway, and inhibiting coking. 0.5-2h -1 The range represents the optimal balance between single-pass conversion rate and unit processing capacity, ensuring that the majority of the reaction is completed in the slurry bed while also providing reasonable economies of scale. These three parameters together constitute a highly efficient and stable reaction system.

[0019] Preferably, in step (2), when the hot high-pressure separator performs separation, the temperature is 300-340℃ and the pressure is 9-10MPa.

[0020] By adopting the above technical solution, the hot high-pressure separator operates at 300-340℃, eliminating the need for material cooling before subsequent membrane filtration and even fixed-bed feeding. This reduces the overall system energy consumption and significantly improves the process's economic efficiency. The separator operates at a pressure of 9-10 MPa, facilitating efficient and stable initial gas-liquid separation. This separates most of the gaseous products, such as hydrogen and light gases, providing a relatively stable, primarily liquid-solid two-phase feed for downstream membrane filtration, protecting the inorganic ceramic membrane filter and optimizing its filtration performance. Therefore, the combination of these parameters provides a stable, high-temperature, and non-clogging liquid-solid feed for subsequent precision membrane filtration, ensuring the entire preparation process can operate stably and continuously over long periods.

[0021] Preferably, in step (3), an inorganic ceramic membrane is used in the inorganic ceramic membrane filter. The inorganic ceramic membrane is an alumina, zirconium oxide, silicon carbide or titanium oxide ceramic membrane, and the pore size of the inorganic ceramic membrane is 10-100 nm.

[0022] By adopting the above technical solutions, the inorganic ceramic membranes of the above types can support the continuous and stable operation of the entire preparation process. The membrane pore size is precisely controlled at the nanoscale of 10-100nm to effectively intercept these catalyst particles, ensure the cleanliness of the intermediate oil, and provide ultimate protection for the downstream fixed bed catalyst.

[0023] Preferably, in step (3), the operating temperature of the inorganic ceramic membrane filter is 250-300℃ and the operating pressure is 0.5-3MPa.

[0024] By adopting the above technical solution, maintaining the operating temperature at 250-300℃ can effectively prevent solid deposition and ensure that the filtration process can be carried out stably for a long time; while the operating pressure of 0.5-3MPa provides sufficient driving force to allow the clean oil phase to pass through the membrane efficiently, while completely retaining the nano-catalyst and impurity solids.

[0025] Preferably, in step (4), the hydrogenation refining reactor uses a Ni-Mo / Al2O3 or Co-Mo / Al2O3 catalyst, the reaction temperature is 340-380℃, and the pressure is 6-10MPa.

[0026] By adopting the above technical solution, the catalyst is a widely used hydrotreating catalyst in industry, which has high activity and selectivity for removing heteroatoms such as sulfur, nitrogen, and oxygen, and can achieve deep hydrorefining and thoroughly purify intermediate oil products. By controlling the reaction temperature at 340-380℃ and the pressure at 6-10MPa, not only is sufficient reaction kinetic energy provided to ensure the depth of refining, but also a high hydrogen partial pressure is maintained to promote the hydrotreating reaction and inhibit coking. In this way, an ideal feedstock can be provided for the subsequent isomerization step.

[0027] Preferably, in step (4), the hydroisomerization reactor uses a catalyst supported by SAPO-11, ZSM-22 or ZSM-23 and with platinum or palladium as the active metal, and the reaction temperature is 300-330℃ and the pressure is 7-8MPa.

[0028] By adopting the above-mentioned technical solutions, the aforementioned supports possess one-dimensional ten-membered ring channels and suitable acidity, which facilitates the entry and reaction of straight-chain or monomethyl branched alkane molecules, resulting in the formation of bulky multi-branched alkanes or aromatics. Platinum or palladium are excellent hydrogenation / dehydrogenation active centers, and their strong hydrogenation capacity can promptly saturate unstable intermediates, preventing them from polymerizing into carbon deposits and maintaining the long-term activity of the catalyst. At the same time, the reaction temperature is 300-330℃, and the pressure is 7-8MPa, which can achieve the best balance between isomerization activity and selectivity, and can also maintain a high hydrogen partial pressure, promote hydrogenation equilibrium, and maintain catalyst stability. This enables deep decondensation, ensures high product yield, and guarantees long-term stable operation.

[0029] Preferably, in step (5), the fraction distilled in the 150-280℃ range is a bio-jet fuel product.

[0030] By adopting the above technical solution, the setting of cutting the 150-280℃ fraction in step (5) is a standardized and refined product purification process. It is not only a necessary requirement to meet the product specifications, but also the final confirmation and guarantee of the low pour point characteristics created by all the preceding process steps, thereby obtaining high-quality sustainable aviation fuel with excellent low-temperature performance.

[0031] In summary, this application has the following beneficial effects: 1. This application perfectly solves the industry problem of "raw material adaptability" and "catalyst separation" through the innovative combination of "slurry bed impurity tolerance + high temperature membrane precision separation". The pre-slurry bed protects the delicate fixed bed catalyst, which significantly extends its life from several months in the traditional process to more than 2 years, ensuring that the equipment can operate for a long time, stably and continuously. 2. This application forms a highly efficient model of "graded purification and each performing its own function". The slurry bed is responsible for rough processing and impurity removal, while the fixed bed is responsible for fine processing and quality improvement. This makes the best use of resources, reduces catalyst costs, and the "hot feed" design in the process significantly reduces energy consumption and enhances the economic competitiveness of the entire process. 3. This application creates ideal feedstock (mainly straight-chain alkanes) for downstream isomerization through effective deoxygenation in the pre-processing step, while the efficient isomerization step directly endows bio-jet fuel with excellent low-temperature performance, resulting in a product with low pour point and high yield, fully meeting the standards for sustainable aviation fuel (SAF). Detailed Implementation

[0032] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0033] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this application are commercially available.

[0034] Example 1; A method for preparing low-pour-point biojet fuel from waste oil includes the following steps: (1) The waste oil is mixed with the oil-soluble catalyst precursor, a sulfiding agent is added, and the mixture is fed into a slurry bed reactor for hydrodeoxygenation and impurity removal reaction to obtain the reaction effluent; (2) The reaction effluent obtained in step (1) is directly fed into a hot high-pressure separator for preliminary gas-liquid separation without cooling, to obtain gaseous products and liquid-solid mixtures; (3) The liquid-solid mixture obtained in step (2) is filtered and separated by an inorganic ceramic membrane filter to obtain clean intermediate oil and retained catalyst slurry; (4) The clean intermediate oil obtained in step (3) is passed through a hydrorefining reactor and a hydroisomerization reactor in sequence for deep refining and isomerization dewaxing reaction to obtain the reaction product; (5) Separate and fractionate the reaction products obtained in step (4) to obtain bio-jet fuel products.

[0035] Note: In the above operation step (1), the sulfiding agent is DMDS, and its dosage is 150 μg / g oil based on the mass of waste oil; in step (1), the oil-soluble catalyst precursor is a composite system of molybdenum naphthenate and nickel isooctanoate, with a molar ratio of nickel to molybdenum of 0.3:1, and the amount of oil-soluble catalyst precursor added can be 0.1-2% of the mass of waste oil, which is 0.8% in this embodiment; the reaction conditions of the slurry bed reactor are 320℃, 11.5MPa, and liquid hourly space velocity of 1.25h. -1 The hydrogen-to-oil ratio is 1000:1. In step (2), the temperature is 320℃ and the pressure is 9.5MPa when the hot high-pressure separator is used for separation. In step (3), an inorganic ceramic membrane is used in the inorganic ceramic membrane filter. The inorganic ceramic membrane is a silicon carbide ceramic membrane with a pore size of 55nm. The operating temperature of the inorganic ceramic membrane filter is 275℃ and the operating pressure is 1.75MPa. In step (4), Ni-Mo / Al2O3 is used in the hydrorefining reactor. The reaction temperature is 360℃ and the pressure is 8MPa. In the hydroisomerization reactor, a catalyst with SAPO-11 as the support and platinum as the active metal is used. The loading of the active metal can be 0.3-1wt%, and in this embodiment, 0.5wt% is selected. The reaction temperature is 315℃ and the pressure is 7.5MPa. In step (5), the fraction distilled in the 150-280℃ range is used as bio-jet fuel product.

[0036] Example 2; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (1), the oil-soluble catalyst precursor is a composite system of molybdenum naphthenate and nickel isooctanoate, with a molar ratio of nickel to molybdenum of 0.25:1.

[0037] Example 3; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (1), the oil-soluble catalyst precursor is a composite system of molybdenum naphthenate and nickel isooctanoate, with a molar ratio of nickel to molybdenum of 0.35:1.

[0038] Example 4; A method for preparing low-pour-point biojet fuel from waste oil differs from Example 1 in that, in step (1), the reaction conditions in the slurry bed reactor are 280°C, 15 MPa, and a liquid hourly space velocity of 0.5 h⁻¹. -1 .

[0039] Example 5; A method for preparing low-pour-point biojet fuel from waste oil differs from Example 1 in that, in step (1), the reaction conditions in the slurry bed reactor are 360°C, 8 MPa, and a liquid hourly space velocity of 2 h⁻¹. -1 .

[0040] Example 6; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (2), the temperature is 300°C and the pressure is 10 MPa when the hot high-pressure separator is used for separation.

[0041] Example 7; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (2), the temperature is 340°C and the pressure is 9MPa when the hot high-pressure separator is used for separation.

[0042] Example 8; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (3), the pore size of the inorganic ceramic membrane is 10 nm.

[0043] Example 9; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (3), the pore size of the inorganic ceramic membrane is 100 nm.

[0044] Example 10; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (3), the operating temperature of the inorganic ceramic membrane filter is 250°C and the operating pressure is 3 MPa.

[0045] Example 11; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (3), the operating temperature of the inorganic ceramic membrane filter is 300°C and the operating pressure is 0.5 MPa.

[0046] Example 12; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (4), a Ni-Mo / Al2O3 catalyst is used in the hydrorefining reactor, the reaction temperature is 340℃, and the pressure is 10MPa.

[0047] Example 13; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (4), a Ni-Mo / Al2O3 catalyst is used in the hydrorefining reactor, the reaction temperature is 380℃, and the pressure is 6MPa.

[0048] Example 14; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (4), the hydroisomerization reactor uses SAPO-11 as the support and platinum as the active metal catalyst, with a reaction temperature of 300°C and a pressure of 8 MPa.

[0049] Example 15; A method for preparing low-pour-point bio-jet fuel from waste oil differs from Example 1 in that, in step (4), a catalyst with SAPO-11 as the support and platinum as the active metal is used in the hydroisomerization reactor, the reaction temperature is 330℃ and the pressure is 7MPa.

[0050] Comparative Example 1; A method for preparing low-pour-point biojet fuel from waste oils uses the same raw materials as in Example 1, but differs from Example 1 in that the raw materials are directly fed into a fixed-bed series system consisting of a hydrotreating catalyst and an isomerization catalyst.

[0051] Result: After 120 hours of operation, the pressure drop in the first reactor bed exceeded the allowable value (>0.5 MPa), forcing a shutdown. Disassembly and inspection revealed that the upper part of the catalyst bed was blocked by dense metal-containing (Ca, P) carbon deposits.

[0052] Comparative Example 2; A method for preparing low-pour-point bio-jet fuel from waste oil uses the same raw materials as in Example 1. The difference from Example 1 is that the same raw materials and slurry bed reaction conditions are used, but the subsequent separation uses a high-temperature centrifuge instead of a ceramic membrane filter, and then the fuel enters the same fixed bed system.

[0053] Results: After 600 hours of operation, the freezing point of the product effluent from the isomerization reactor gradually increased from -50℃ initially to -25℃. Analysis of the isomerization catalyst revealed significant molybdenum (Mo) and nickel (Ni) deposition on its surface, confirming that the penetration of fine-particle catalyst led to poisoning and deactivation of the precious metal catalyst.

[0054] Conclusion: Example 1 fully demonstrates the comprehensive advantages of the process of the present invention in processing high-impurity raw materials, maintaining long-term stable operation of the system, and producing high-quality, low-pour-point biojet fuel. Comparative Examples 1 and 2 clearly reveal the core problems faced when traditional processes or separation technologies are imperfect, thus indirectly confirming the necessity and synergistic effect of the two key technical features of the present invention: "slurry bed pre-protection" and "high-temperature membrane precision separation."

[0055] Performance testing; Test sample: Waste cooking oil (waste cooking oil) with an acid value of 18 mgKOH / g, a phosphorus content of 120 ppm, and a calcium content of 50 ppm.

[0056] Experimental method: The method for preparing low pour point bio-jet fuel from waste oil in Examples 1-15 was applied to the above-mentioned test samples, and the bio-jet fuel yield, pour point, aromatic content and sulfur content were tested. The test results are shown in Table 1 below.

[0057] Table 1 Application test results of Examples 1-15

[0058] As can be seen from Examples 1-15 and Table 1, this application provides a method for preparing low-pour-point bio-jet fuel from waste oil based on a slurry bed coupled with high-temperature membrane filtration. In practical application, the bio-jet fuel yield can reach up to 56.5%, with an optimal pour point of -53.2℃, meeting the requirements for qualified bio-jet fuel with a pour point < -47℃. Simultaneously, the optimal aromatic content is 8.2% (v / v), and the sulfur content is < 1 ppm, indicating excellent overall quality. Finally, it should be emphasized that the entire equipment corresponding to the above method can operate continuously and stably for 2000 hours, with no significant change in pressure drop across the reactors, demonstrating long-term, stable, and continuous operation.

[0059] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing low-pour-point bio-jet fuel from waste oil, characterized in that, Includes the following steps: (1) The waste oil is mixed with the oil-soluble catalyst precursor, a sulfiding agent is added, and the mixture is fed into a slurry bed reactor for hydrodeoxygenation and impurity removal reaction to obtain the reaction effluent; (2) The reaction effluent obtained in step (1) is directly fed into a hot high-pressure separator for preliminary gas-liquid separation without cooling, to obtain gaseous products and liquid-solid mixtures; (3) The liquid-solid mixture obtained in step (2) is filtered and separated by an inorganic ceramic membrane filter to obtain clean intermediate oil and retained catalyst slurry; (4) The clean intermediate oil obtained in step (3) is passed through a hydrorefining reactor and a hydroisomerization reactor in sequence for deep refining and isomerization dewaxing reaction to obtain the reaction product; (5) Separate and fractionate the reaction products obtained in step (4) to obtain bio-jet fuel products.

2. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (1), the amount of oil-soluble catalyst precursor added is 0.1-2% of the mass of waste oil, and its active metal is selected from any one or more of molybdenum, nickel, cobalt and tungsten.

3. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 2, characterized in that: In step (1), the oil-soluble catalyst precursor is a composite system of molybdenum naphthenate and nickel isooctanoate, with a molar ratio of nickel to molybdenum of (0.25-0.35):

1.

4. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (1), the reaction conditions of the slurry bed reactor are 280-360℃, 8-15MPa, and liquid hourly space velocity (LISH) of 0.5-2h. -1 .

5. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (2), the temperature is 300-340℃ and the pressure is 9-10MPa when the hot high-pressure separator is performing separation.

6. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (3), an inorganic ceramic membrane is used in the inorganic ceramic membrane filter. The inorganic ceramic membrane is an alumina, zirconium oxide, silicon carbide or titanium oxide ceramic membrane, and the pore size of the inorganic ceramic membrane is 10-100 nm.

7. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (3), the operating temperature of the inorganic ceramic membrane filter is 250-300℃ and the operating pressure is 0.5-3MPa.

8. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (4), the hydrogenation refining reactor uses Ni-Mo / Al2O3 or Co-Mo / Al2O3 catalyst, the reaction temperature is 340-380℃, and the pressure is 6-10MPa.

9. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (4), the hydroisomerization reactor uses a catalyst supported by SAPO-11, ZSM-22 or ZSM-23 and with platinum or palladium as the active metal. The reaction temperature is 300-330℃ and the pressure is 7-8MPa.

10. The method for preparing low-pour-point bio-jet fuel from waste oil according to claim 1, characterized in that: In step (5), the fractions distilled in the 150-280℃ range are bio-jet fuel products.

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