Process for preparing biological aviation kerosene from waste oil

Abstract

The invention relates to the technical field of biological aviation kerosene, and discloses a process for preparing biological aviation kerosene from waste grease. The method comprises the following steps: introducing waste oil into a hydrofining reactor, introducing hydrogen, carrying out a hydrodeoxygenation reaction under the catalysis of a hydrogenation catalyst, carrying out a reaction on the obtained hydrodeoxygenated oil in an isomerization pour point depressing reactor, and finally carrying out isomerization hot high-pressure separation treatment, isomerization cold high-pressure separation treatment and rectification tower segmentation to obtain the biological aviation kerosene. The specific surface area of a carbon matrix of the hydrogenation catalyst is large, the void structure is rich, a large number of Ni-Mo-P active catalytic centers can be exposed, precious metals such as platinum and ruthenium do not need to be added, the hydrodeoxygenation reaction efficiency of waste oil and fat is remarkably improved, the mass fraction of branched paraffin and cycloparaffin in biological aviation fuel is high, and the combustion performance is better.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-jet fuel, in particular to a process for preparing bio-jet fuel from waste oil. BACKGROUND

[0002] Bio-jet fuel is prepared from renewable resources such as waste animal and vegetable oil and catering waste oil. It has high calorific value, low cost and is environmentally friendly. However, catering waste oil contains a large amount of unsaturated fatty acids and has a high oxygen content, which affects the combustion calorific value and other properties of bio-jet fuel. Therefore, the waste oil raw material needs to be subjected to a hydrodeoxygenation reaction to generate high-calorific-value branched alkanes and naphthenes, so as to improve the combustion characteristics of bio-jet fuel.

[0003] Common hydrodeoxygenation catalysts include nickel-based catalysts and noble metal catalysts such as ruthenium-based and platinum-based catalysts. Among them, nickel-based catalysts have good hydrodeoxygenation catalytic activity and are relatively inexpensive, and are widely used. In order to reduce the agglomeration of nickel and other catalysts, increase the catalytic sites and improve the catalytic activity, a catalyst carrier such as alumina or activated carbon is usually added. Patent No. CN112044465B discloses an oil hydrodeoxygenation upgrading catalyst, its preparation method and application. The catalyst is prepared by using ruthenium oxide, molybdenum oxide and nickel oxide as active components, and gamma-alumina, zeolite and activated carbon as catalyst carriers. The prepared catalyst has good hydrodeoxygenation performance and can improve the quality of oil products. However, the patent needs to use expensive ruthenium catalyst, which has high cost. SUMMARY

[0004] The present application solves the problem of low hydrodeoxygenation efficiency of nickel-based catalysts for oil, and significantly improves the content of branched alkanes and naphthenes in bio-jet fuel without adding noble metal catalysts.

[0005] The technical solution of the present application is a process for preparing bio-jet fuel from waste oil: (1) water, polyvinyl alcohol, phosphoric acid and urea are added to a reaction container, and the mixture is stirred to obtain a solution. The solution is poured into ethanol, filtered, the filter cake is washed with ethanol, and dried to obtain phosphoric acid polyvinyl alcohol.

[0006] (2) N,N-dimethylformamide, phosphoric acid polyvinyl alcohol, 1,5-naphthalene diisocyanate and dibutyltin dilaurate are added to a reaction container, nitrogen is introduced, and the mixture is stirred to obtain a solution. The solution is poured into ethanol, filtered, the filter cake is washed with ethanol, and dried to obtain cross-linked phosphoric acid polyvinyl alcohol. The preparation reaction formula is: .

[0007] (3) adding water, cross-linked phosphoric acid polyvinyl alcohol, nickel compound and molybdenum compound into the container, stirring and drying to remove water, placing the product in a tube furnace, passing nitrogen, calcining, and cooling to obtain a hydrogenation catalyst.

[0008] (4) loading the hydrogenation catalyst into a hydrofining reactor, passing the waste oil through a preheater into the hydrofining reactor, passing hydrogen, performing a hydrodeoxygenation reaction, passing the reaction product through a condenser into a three-phase separator for "oil-gas-water" three-phase separation, passing the oil phase into a stripping tower for fractionation to remove light components, and the tower bottom oil being a hydrodeoxygenated oil.

[0009] (5) passing the hydrodeoxygenated oil into a first-stage isomerization and condensation reduction reactor for a first-stage reaction, passing the product into a second-stage isomerization and condensation reduction reactor for a second-stage reaction, passing the product into a third-stage isomerization and condensation reduction reactor for a third-stage reaction, finally performing isomerization hot high-pressure separation and isomerization cold high-pressure separation, and passing the product into a rectification tower for cutting to obtain bio-jet fuel.

[0010] Preferably, in (1), the mass ratio of polyvinyl alcohol, phosphoric acid and urea is 100:(70-200):(3.4-10).

[0011] Preferably, in (1), the reaction temperature is 95-100°C and the reaction time is 6-10h.

[0012] Preferably, in (2), the mass ratio of phosphoric acid polyvinyl alcohol, 1,5-naphthalene diisocyanate and dibutyltin dilaurate is 100:(60-85):(0.16-0.22).

[0013] Preferably, in (2), the reaction temperature is 65-80°C and the reaction time is 2-3h.

[0014] Preferably, in (2), the mass ratio of cross-linked phosphoric acid polyvinyl alcohol, nickel compound and molybdenum compound is 100:(33-57):(42-87).

[0015] Preferably, in (3), the calcination is to increase the temperature to 650-750°C at a temperature increasing rate of 5-8°C / min, and to keep the temperature for 1-2h.

[0016] Preferably, in (3), the nickel compound is nickel nitrate or nickel chloride, and the molybdenum compound is ammonium molybdate.

[0017] Preferably, in (4), during the hydrodeoxygenation reaction, the reaction pressure is 3-6MPa, the space velocity is 1-1.6h -1 , the reaction temperature is 370-420°C, and the hydrogen to waste oil ratio is 800-1200:1.

[0018] Preferably, in (5), during the first-stage reaction, the reaction pressure is 3-5MPa and the space velocity is 1-1.3h-1 The reaction temperature is 350-380 DEG C, and the hydrogen / oil ratio is 800-900:1.

[0019] Preferably, in the secondary reaction of (5), the reaction pressure is 3-5 MPa, the space velocity is 1-1.2 h -1 The reaction temperature is 330-350 DEG C, and the hydrogen / oil ratio is 650-800:1.

[0020] Preferably, in the tertiary reaction of (5), the reaction pressure is 3-5 MPa, the space velocity is 0.8-1 h -1 The reaction temperature is 300-320 DEG C, and the hydrogen / oil ratio is 450-550:1.

[0021] The application has the beneficial technical effects that: under the catalysis of urea, polyvinyl alcohol and phosphoric acid are reacted to obtain polyvinyl alcohol phosphate, the hydroxyl groups of which are crosslinked and polymerized with 1,5-naphthalene diisocyanate to obtain crosslinked polyvinyl alcohol phosphate with a three-dimensional space network. Then, nickel and molybdenum elements are uniformly adsorbed into the space network of the crosslinked polyvinyl alcohol phosphate, and after high-temperature calcination, the polyvinyl alcohol and the naphthalene ring with high carbon content are carbonized to form an active porous carbon matrix, and the nickel and molybdenum elements and the phosphoric acid groups in-situ generate high-dispersion Ni-Mo-P catalytic sites in the carbon matrix. Meanwhile, the specific surface area of the catalyst carbon matrix is large, and the void structure is rich, which can expose a large number of active catalytic centers, and there is no need to add noble metals such as platinum and ruthenium, so that the hydrogenation deoxygenation reaction efficiency of waste oil is significantly improved, the mass fraction of branched alkanes and naphthenes in bio-jet fuel is high, and the combustion performance is better. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a process flow chart for preparing bio-jet fuel.

[0023] Figure 2 is a scanning electron microscope image of the hydrogenation catalyst of Example 1. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] Example 1 (1) Into a reaction vessel equipped with a condensing reflux tube, 1 L of water, 200 g of polyvinyl alcohol (type PVA0588, hereinafter the same), 220 g of phosphoric acid, and 10.6 g of urea were added, heated to 100°C, and stirred for 6 h. The solution after the reaction was poured into ethanol, suction filtered, the filter cake was washed with ethanol, and dried to obtain a phosphoric acid polyvinyl alcohol.

[0026] (2) Into a reaction vessel, 3 L of N,N-dimethylformamide, 300 g of the phosphoric acid polyvinyl alcohol, 207 g of 1,5-naphthalene diisocyanate, and 0.48 g of dibutyltin dilaurate were added, nitrogen was introduced, heated to 70°C, and stirred for 2 h. The solution after the reaction was poured into ethanol, suction filtered, the filter cake was washed with ethanol, and dried to obtain a crosslinked phosphoric acid polyvinyl alcohol.

[0027] (3) Into a vessel, 15 L of deionized water, 500 g of the crosslinked phosphoric acid polyvinyl alcohol, 117 g of nickel nitrate, and 84 g of ammonium molybdate tetrahydrate were added, stirred for 3 h, and dried to remove water. The product was placed in a tube furnace, nitrogen was introduced, and heated to 700°C at a temperature increase rate of 5°C / min, and calcined for 1 h. After cooling, a hydrogenation catalyst was obtained. Figure 2 The scanning electron microscope image of the hydrogenation catalyst showed that the carbon carrier of the hydrogenation catalyst contained a large number of pore structures and had a large specific surface area.

[0028] (4) The process flow diagram for the preparation of bio-jet fuel was combined with the preparation process of the bio-jet fuel according to the application. Figure 2 The process for preparing bio-jet fuel is as follows: a hydrogenation catalyst was loaded into a hydrogenation reactor, and catering waste oil was introduced into the hydrogenation reactor through a preheater, hydrogen was introduced, the hydrogen to oil ratio was controlled to be 1200:1 (the hydrogen to oil ratio is the ratio of the standard volume flow rate of circulating hydrogen at the inlet of the reactor to the volume flow rate of the catering waste oil per unit time), the pressure was 4 MPa, the space velocity was 1.5 h -1 , the temperature was 380°C, and a hydrogenation deoxygenation reaction was performed. The reaction product was introduced into a three-phase separator through a condenser for "oil-gas-water" three-phase separation, the oil phase was introduced into a stripping column for fractionation to remove light components, and the oil at the bottom of the column was hydrogenation deoxygenated oil.

[0029] (5) The hydrogenation deoxygenated oil was introduced into a first-stage isomerization and condensation reduction reactor, and reacted under the conditions of a pressure of 5 MPa, a space velocity of 1.3 h -1 , a temperature of 360°C, and a hydrogen to oil ratio of 800:1. The product was introduced into a second-stage isomerization and condensation reduction reactor, and reacted under the conditions of a pressure of 3 MPa, a space velocity of 1.2 h -1 , a reaction temperature of 350°C, and a hydrogen to oil ratio of 700:1. The product was introduced into a third-stage isomerization and condensation reduction reactor, and reacted under the conditions of a pressure of 3 MPa, a space velocity of 1 h -1 , a temperature of 320°C, and a hydrogen to oil ratio of 450:1. Finally, the product was subjected to isomerization hot high-pressure separation and isomerization cold high-pressure separation, and then introduced into a rectifying column for cutting to obtain bio-jet fuel.

[0030] Comparative Example 1 (1) Into a reaction vessel, 3L of N,N-dimethylformamide, 300g of polyvinyl alcohol, 207g of 1,5-naphthalene diisocyanate, 0.48g of dibutyltin dilaurate were added, nitrogen was introduced, heated to 70°C, and stirred for 2h. The solution was poured into ethanol, suction filtered, the filter cake was washed with ethanol, and dried to obtain a crosslinked polyvinyl alcohol.

[0031] (2) Into a vessel, 15L of deionized water, 500g of crosslinked polyvinyl alcohol, 117g of nickel nitrate, and 84g of ammonium molybdate tetrahydrate were added, stirred for 3h, and dried to remove water. The product was placed in a tube furnace, nitrogen was introduced, and heated to 700°C at a rate of 5°C / min, and held for 1h. After cooling, a hydrogenation catalyst was obtained.

[0032] (3) The hydrogenation catalyst was loaded into a hydrofining reactor, and the catering waste oil was introduced into the hydrofining reactor through a preheater, hydrogen was introduced, the hydrogen to oil ratio was controlled to be 1200:1, the pressure was 4MPa, the space velocity was 1.5h -1 , the temperature was 380°C, and the hydrogenation deoxygenation reaction was carried out. The reaction product was introduced into a three-phase separator through a condenser for "oil-gas-water" three-phase separation, the oil phase was introduced into a stripping column for fractionation to remove light components, and the oil at the bottom of the column was hydrogenation deoxygenated oil.

[0033] (4) The hydrogenation deoxygenated oil was introduced into a first isomerization and condensation reduction reactor, and the reaction was carried out under the conditions of a pressure of 5MPa, a space velocity of 1.3h -1 , a temperature of 360°C, and a hydrogen to oil ratio of 800:1. The product was introduced into a second isomerization and condensation reduction reactor, and the reaction was carried out under the conditions of a pressure of 3MPa, a space velocity of 1.2h -1 , a reaction temperature of 350°C, and a hydrogen to oil ratio of 700:1. The product was introduced into a third isomerization and condensation reduction reactor, and the reaction was carried out under the conditions of a pressure of 3MPa, a space velocity of 1h -1 , a temperature of 320°C, and a hydrogen to oil ratio of 450:1. Finally, the product was treated by isomerization hot high pressure separation and isomerization cold high pressure separation, and then introduced into a rectifying column for cutting to obtain bio-jet fuel.

[0034] Comparative Example 2 (1) Into a reaction vessel equipped with a condenser reflux tube, 1L of water, 200g of polyvinyl alcohol, 220g of phosphoric acid, and 10.6g of urea were added, heated to 100°C, and stirred for 6h. The solution was poured into ethanol, suction filtered, the filter cake was washed with ethanol, and dried to obtain a phosphoric acid polyvinyl alcohol.

[0035] (2) Add 15 L of deionized water, 500 g of polyvinyl alcohol phosphate, 117 g of nickel nitrate, and 84 g of ammonium molybdate tetrahydrate into a container, stir for 3 h, dry and remove water, place the product in a tube furnace, pass nitrogen, and increase the temperature to 700℃ at a rate of 5℃ / min, keep the temperature for 1 h, cool, and obtain a hydrogenation catalyst.

[0036] (3) Load the hydrogenation catalyst into the hydrofining reactor, pass the catering waste oil through the preheater into the hydrofining reactor, pass hydrogen, control the hydrogen / oil ratio to be 1200:1, the pressure to be 4 MPa, the space velocity to be 1.5 h -1 -1, and the temperature to be 380℃, perform hydrodeoxygenation reaction, pass the reaction product through the condenser into the three-phase separator for "oil-gas-water" three-phase separation, pass the oil phase into the stripping tower for fractionation to remove light components, and the oil at the bottom of the tower is the hydrodeoxygenated oil.

[0037] (4) Pass the hydrodeoxygenated oil into the first-stage isomerization and condensation reduction reactor, perform reaction, control the pressure to be 5 MPa, the space velocity to be 1.3 h -1 -1, the temperature to be 360℃, and the hydrogen / oil ratio to be 800:1; pass the product into the second-stage isomerization and condensation reduction reactor, perform reaction, control the pressure to be 3 MPa, the space velocity to be 1.2 h -1 -1, the reaction temperature to be 350℃, and the hydrogen / oil ratio to be 700:1; pass the product into the third-stage isomerization and condensation reduction reactor, perform reaction, control the pressure to be 3 MPa, the space velocity to be 1 h -1 -1, the temperature to be 320℃, and the hydrogen / oil ratio to be 450:1; finally, perform isomerization hot high-pressure separation and isomerization cold high-pressure separation, and pass the product into the rectifying tower for cutting to obtain bio-jet fuel.

[0038] Comparative Example 3 (1) Add 15 L of deionized water, 500 g of cross-linked polyvinyl alcohol phosphate (prepared in Example 1), and 117 g of nickel nitrate into a container, stir for 3 h, dry and remove water, place the product in a tube furnace, pass nitrogen, and increase the temperature to 700℃ at a rate of 5℃ / min, keep the temperature for 1 h, cool, and obtain a hydrogenation catalyst.

[0039] (2) Load the hydrogenation catalyst into the hydrofining reactor, pass the catering waste oil through the preheater into the hydrofining reactor, pass hydrogen, control the hydrogen / oil ratio to be 1200:1, the pressure to be 4 MPa, the space velocity to be 1.5 h -1 -1, and the temperature to be 380℃, perform hydrodeoxygenation reaction, pass the reaction product through the condenser into the three-phase separator for "oil-gas-water" three-phase separation, pass the oil phase into the stripping tower for fractionation to remove light components, and the oil at the bottom of the tower is the hydrodeoxygenated oil.

[0040] (3) Pass the hydrodeoxygenated oil into the first-stage isomerization and condensation reduction reactor, perform reaction, control the pressure to be 5 MPa, the space velocity to be 1.3 h -1The temperature was 360℃, and the hydrogen-to-oil ratio was 800:1. The product was fed into a two-stage isomerization dewaxing reactor for reaction, with the pressure controlled at 3 MPa and the space velocity at 1.2 h⁻¹. -1 The reaction temperature was 350℃, and the hydrogen-to-oil ratio was 700:1. The product was fed into a three-stage isomerization dewaxing reactor for reaction, with the pressure controlled at 3 MPa and the space velocity at 1 h⁻¹. -1 The temperature was 320℃ and the hydrogen-to-oil ratio was 450:1. Finally, after heterogeneous hot high-pressure separation and heterogeneous cold high-pressure separation, the product entered the distillation column for splitting to obtain bio-jet fuel.

[0041] Example 2 (1) Add 0.8L of water, 200g of polyvinyl alcohol, 140g of phosphoric acid and 6.8g of urea to a reaction vessel equipped with a reflux condenser, heat to 95°C, stir and react for 8 hours, pour the solution into ethanol, filter, wash the filter cake with ethanol, dry and obtain polyvinyl phosphate.

[0042] (2) Add 4L of N,N-dimethylformamide, 300g of polyvinyl alcohol phosphate, 255g of 1,5-naphthalene diisocyanate and 0.66g of dibutyltin dilaurate to the reaction vessel, purge with nitrogen, heat to 80°C, stir and react for 2h, pour the solution into ethanol, filter, wash the filter cake with ethanol, dry, and obtain cross-linked polyvinyl alcohol phosphate.

[0043] (3) Add 20L of deionized water, 500g of cross-linked polyvinyl chloride, 102g of nickel chloride and 115g of ammonium molybdate tetrahydrate to the container, stir for 5h, dry to remove water, place the product in a tube furnace, introduce nitrogen gas, raise the temperature to 750℃ at a heating rate of 5℃ / min, keep it at the temperature for 1h, cool, and obtain the hydrogenation catalyst.

[0044] (4) Load the hydrogenation catalyst into the hydrorefining reactor, and pass the waste cooking oil through the preheater into the hydrorefining reactor. Introduce hydrogen gas, control the hydrogen-to-oil ratio at 800:1, the pressure at 6 MPa, and the space velocity at 1 h⁻¹. -1 The temperature is 420℃, and a hydrodeoxygenation reaction is carried out. The reaction products are condensed and then enter a three-phase separator for "oil-gas-water" three-phase separation. The oil phase enters a stripping tower for fractionation to remove light components. The bottom oil of the tower is hydrodeoxygenated oil.

[0045] (5) The hydrodeoxygenated oil is fed into the primary isomerization dewaxing reactor for reaction, and the pressure is controlled at 3 MPa and the space velocity is 1.3 h⁻¹. -1 The temperature was 380℃, and the hydrogen-to-oil ratio was 900:1. The product was fed into a two-stage isomerization dewaxing reactor for reaction, with the pressure controlled at 3 MPa and the space velocity at 1.2 h⁻¹. -1The reaction temperature was 350℃, and the hydrogen-to-oil ratio was 700:1. The product was fed into a three-stage isomerization dewaxing reactor for further reaction, with the pressure controlled at 3 MPa and the space velocity at 0.8 h⁻¹. -1 The temperature was 300℃ and the hydrogen-to-oil ratio was 550:1. Finally, after heterogeneous hot high-pressure separation and heterogeneous cold high-pressure separation, the product entered a distillation column for splitting to obtain bio-jet fuel.

[0046] Example 3 (1) Add 1L of water, 200g of polyvinyl alcohol, 400g of phosphoric acid and 20g of urea to a reaction vessel equipped with a reflux condenser, heat to 95°C, stir and react for 10h, pour the solution into ethanol, filter, wash the filter cake with ethanol, dry and obtain polyvinyl phosphate.

[0047] (2) Add 3L of N,N-dimethylformamide, 300g of polyvinyl alcohol phosphate, 180g of 1,5-naphthalene diisocyanate and 0.54g of dibutyltin dilaurate to the reaction vessel, purge with nitrogen, heat to 70°C, stir and react for 3h, pour the solution into ethanol, filter, wash the filter cake with ethanol, dry, and obtain cross-linked polyvinyl alcohol phosphate.

[0048] (3) Add 16L of deionized water, 500g of cross-linked polyvinyl phosphate, 85g of nickel nitrate and 143g of ammonium molybdate tetrahydrate to the container, stir for 5h, dry to remove water, place the product in a tube furnace, introduce nitrogen gas, raise the temperature to 650℃ at a rate of 5℃ / min, keep it at the temperature for 2h, cool, and obtain the hydrogenation catalyst.

[0049] (4) Load the hydrogenation catalyst into the hydrorefining reactor, and introduce waste cooking oil into the hydrorefining reactor through a preheater. Introduce hydrogen gas, control the hydrogen-to-oil ratio at 1000:1, the pressure at 3 MPa, and the space velocity at 1.6 h⁻¹. -1 The temperature is 370℃, and a hydrodeoxygenation reaction is carried out. The reaction products are condensed and then enter a three-phase separator for "oil-gas-water" three-phase separation. The oil phase enters a stripping tower for fractionation to remove light components. The bottom oil of the tower is hydrodeoxygenated oil.

[0050] (5) The hydrodeoxygenated oil is fed into the primary isomerization dewaxing reactor for reaction, and the pressure is controlled at 5 MPa and the space velocity is 1 h⁻¹. -1 The temperature was 350℃, and the hydrogen-to-oil ratio was 900:1. The product was fed into a two-stage isomerization dewaxing reactor for reaction, with the pressure controlled at 5 MPa and the space velocity at 1 h⁻¹. -1 The reaction temperature was 330℃, and the hydrogen-to-oil ratio was 800:1. The product was fed into a three-stage isomerization dewaxing reactor for reaction, with the pressure controlled at 3 MPa and the space velocity at 1 h⁻¹. -1The temperature was 300℃ and the hydrogen-to-oil ratio was 500:1. Finally, after heterogeneous hot high-pressure separation and heterogeneous cold high-pressure separation, the product entered a distillation column for splitting to obtain bio-jet fuel.

[0051] Example 4 (1) Add 1L of water, 200g of polyvinyl alcohol, 310g of phosphoric acid and 15.2g of urea to a reaction vessel equipped with a reflux condenser, heat to 100℃, stir and react for 9h, pour the solution into ethanol, filter, wash the filter cake with ethanol, dry and obtain polyvinyl phosphate.

[0052] (2) Add 4L of N,N-dimethylformamide, 300g of polyvinyl alcohol phosphate, 225g of 1,5-naphthalene diisocyanate and 0.66g of dibutyltin dilaurate to the reaction vessel, purge with nitrogen, heat to 65°C, stir and react for 3h, pour the solution into ethanol, filter, wash the filter cake with ethanol, dry, and obtain cross-linked polyvinyl alcohol phosphate.

[0053] (3) Add 20L of deionized water, 500g of cross-linked polyvinyl phosphate, 66g of nickel nitrate and 174g of ammonium molybdate tetrahydrate to the container, stir for 5h, dry to remove water, place the product in a tube furnace, introduce nitrogen gas, raise the temperature to 750℃ at a rate of 8℃ / min, keep it at the temperature for 1h, cool, and obtain the hydrogenation catalyst.

[0054] (4) Load the hydrogenation catalyst into the hydrorefining reactor, and introduce waste cooking oil into the hydrorefining reactor through a preheater. Introduce hydrogen gas, control the hydrogen-to-oil ratio at 1000:1, the pressure at 6 MPa, and the space velocity at 1.4 h⁻¹. -1 The temperature is 400℃, and the hydrodeoxygenation reaction is carried out. The reaction products are condensed and enter a three-phase separator for "oil-gas-water" three-phase separation. The oil phase enters the stripping tower for fractionation to remove light components. The bottom oil of the tower is hydrodeoxygenated oil.

[0055] (5) The hydrodeoxygenated oil is fed into the primary isomerization dewaxing reactor for reaction, and the pressure is controlled at 5 MPa and the space velocity is 1.2 h⁻¹. -1 The temperature was 380℃, and the hydrogen-to-oil ratio was 900:1. The product was fed into a two-stage isomerization dewaxing reactor for reaction, with the pressure controlled at 5 MPa and the space velocity at 1 h⁻¹. -1 The reaction temperature was 340℃, and the hydrogen-to-oil ratio was 650:1. The product was fed into a three-stage isomerization dewaxing reactor for reaction, with the pressure controlled at 5 MPa and the space velocity at 1 h⁻¹. -1 The temperature was 300℃ and the hydrogen-to-oil ratio was 550:1. Finally, after heterogeneous hot high-pressure separation and heterogeneous cold high-pressure separation, the product entered a distillation column for splitting to obtain bio-jet fuel.

[0056] The composition of bio-jet fuel was tested using the ASTM D2425-21 standard, and the results are shown in Table 1.

[0057] Table 1. Composition of bio-jet fuel

[0058] After testing, compared with Comparative Examples 1-3, the bio-jet fuel prepared in Example 1 had a branched-chain alkanes content of 91.69-94.73% and a cycloalkanes content of 4.13-6.28%. This allows for more efficient hydrodeoxygenation of fatty acids from waste oils into high-calorific-value fuels such as alkanes and cycloalkanes. This is mainly because nickel and molybdenum elements generate Ni-Mo-P catalytic sites in situ within the catalyst carbon support, exhibiting high dispersion and exposing a large number of active catalytic centers, thus improving the efficiency of the hydrodeoxygenation reaction on waste oils. Examples 2-4, through optimization of different reaction conditions, also produced bio-jet fuels with high contents of branched-chain alkanes and cycloalkanes.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A process for preparing bio-jet fuel from waste oil, characterized in that, The process includes: S1. A hydrogenation catalyst is loaded into the hydrorefining reactor. Waste oil is passed into the hydrorefining reactor through a preheater and hydrogen is introduced to carry out the hydrodeoxygenation reaction. The reaction product is passed into a three-phase separator through a condenser for "oil-gas-water" three-phase separation. The oil phase enters a stripping tower for fractionation to remove light components. The bottom oil of the tower is hydrodeoxygenated oil. S2. The hydrodeoxygenated oil is fed into a primary isomeric dewaxing reactor for primary reaction; the product is fed into a secondary isomeric dewaxing reactor for secondary reaction; the product is fed into a tertiary isomeric dewaxing reactor for tertiary reaction; and finally, after isomeric hot high-pressure separation and isomeric cold high-pressure separation, the product enters a distillation column for splitting to obtain bio-jet fuel. Methods for preparing hydrogenation catalysts include: (1) Add water and polyvinyl alcohol, phosphoric acid and urea in a mass ratio of 100:(70-200):(3.4-10) to the reaction vessel, stir to obtain a solution, pour the solution into ethanol, filter, wash the filter cake, dry and obtain polyvinyl alcohol phosphate. (2) Add N,N-dimethylformamide and polyvinyl phosphate, 1,5-naphthalene diisocyanate and dibutyltin dilaurate in a mass ratio of 100:(60-85):(0.16-0.22) to the reaction vessel, introduce nitrogen gas, stir to obtain a solution, pour the solution into ethanol, filter, wash the filter cake, dry and obtain cross-linked polyvinyl phosphate; (3) Add water and cross-linked polyvinyl phosphate, nickel compound and molybdenum compound in a mass ratio of 100:(33-57):(42-87) to the container, stir and dry to remove water, then place in a tube furnace, introduce nitrogen gas, calcine and cool to obtain hydrogenation catalyst.

2. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, During the hydrogenation and deoxygenation reaction in S1, the reaction pressure is 3-6 MPa and the space velocity is 1-1.6 h⁻¹. -1 The reaction temperature is 370-420℃, and the hydrogen-to-oil ratio of hydrogen to waste oil is 800-1200:

1.

3. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, In the first-order reaction of S2, the reaction pressure is 3-5 MPa and the space velocity is 1-1.3 h⁻¹. -1 The reaction temperature is 350-380℃, and the hydrogen-to-oil ratio is 800-900:

1.

4. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, During the second-order reaction in S2, the reaction pressure is 3-5 MPa and the space velocity is 1-1.2 h⁻¹. -1 The reaction temperature is 330-350℃, and the hydrogen-to-oil ratio is 650-800:

1.

5. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, In the S2 third-stage reaction, the reaction pressure is 3-5 MPa and the space velocity is 0.8-1 h⁻¹. -1 The reaction temperature is 300-320℃, and the hydrogen-to-oil ratio is 450-550:

1.

6. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, The reaction temperature in (1) is 95-100℃ and the reaction time is 6-10h.

7. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, The reaction temperature in (2) is 65-80℃ and the reaction time is 2-3h.

8. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, In step (3), the calcination is carried out by raising the temperature to 650-750℃ at a rate of 5-8℃ / min and holding it at that temperature for 1-2 hours.

9. The process for preparing bio-jet fuel from waste oil according to claim 1, characterized in that, In (3), the nickel compound is nickel nitrate or nickel chloride, and the molybdenum compound is ammonium molybdate.

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