Process for preparing bio-jet fuel from waste oil

Abstract

The application relates to the technical field of bio-jet fuel, and discloses a process for preparing bio-jet fuel from waste oil. The waste oil is introduced into a hydrogenation refining reactor, hydrogen is introduced, a hydrogenation deoxygenation reaction is carried out under the catalysis of a hydrogenation catalyst, the obtained hydrogenation deoxygenation oil is subjected to a reaction in an isomerization condensation reduction reactor, finally, the hydrogenation deoxygenation oil is subjected to isomerization hot high-pressure separation and isomerization cold high-pressure separation treatment, and is cut into a rectifying tower, so that bio-jet fuel is obtained. The specific surface area of the carbon base body of the hydrogenation catalyst is large, the void structure is rich, a large number of Ni-Mo-P active catalytic centers can be exposed, noble metals such as platinum and ruthenium do not need to be added, the hydrogenation deoxygenation reaction efficiency on the waste oil is significantly improved, the mass fraction of branched alkanes and naphthenes in the bio-jet fuel is high, and the combustion performance is better.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of bio-jet fuel, and particularly relates 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 plant oil and catering waste oil, and has the advantages of high calorific value, low cost and green environmental protection. However, the 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 performances of the 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 the bio-jet fuel.

[0003] Common hydrodeoxygenation catalysts include nickel-based catalysts and precious metal catalysts such as ruthenium-based and platinum-based catalysts. The nickel-based catalyst has good hydrodeoxygenation catalytic activity and is relatively low in cost, and is therefore widely applied. In order to reduce the agglomeration of the nickel catalyst and increase the catalytic sites and catalytic activity, a catalyst carrier such as alumina or activated carbon needs to be added. Patent No. CN112044465B discloses an oil hydrodeoxygenation upgrading catalyst as well as a preparation method and application thereof. The catalyst is prepared by taking ruthenium oxide, molybdenum oxide and nickel oxide as active components and taking gamma-alumina, zeolite and activated carbon as catalyst carriers, and has good hydrodeoxygenation performance and can improve the quality of the oil. However, the patent needs to use expensive ruthenium catalysts, and the cost is high. SUMMARY

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

[0005] The technical scheme of the application is as follows: a process for preparing bio-jet fuel from waste oil:

[0006] (1) water, polyvinyl alcohol, phosphoric acid and urea are added to a reaction container, and a solution is obtained by stirring and reacting, the solution is poured into ethanol, suction filtration is performed, the filter cake is washed with ethanol, and drying is performed to obtain polyvinyl alcohol phosphoric acid.

[0007] (2) N,N-dimethylformamide, polyvinyl alcohol phosphoric acid, 1,5-naphthalene diisocyanate and dibutyltin dilaurate are added to a reaction container, nitrogen is introduced, a solution is obtained by stirring and reacting, the solution is poured into ethanol, suction filtration is performed, the filter cake is washed with ethanol, and drying is performed to obtain cross-linked polyvinyl alcohol phosphoric acid, and the preparation reaction formula is as follows:

[0008] .

[0009] (3) Add water, cross-linked polyvinyl phosphate, nickel compound, and molybdenum compound to the container, stir and dry to remove water, place the product in a tube furnace, introduce nitrogen gas, calcine, cool, and obtain hydrogenation catalyst.

[0010] (4) The 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 the stripping tower for fractionation to remove light components. The bottom oil of the tower is hydrodeoxygenated oil.

[0011] (5) The hydrodeoxygenated oil is fed into the first-stage isomeric dewaxing reactor for the first-stage reaction; the product is fed into the second-stage isomeric dewaxing reactor for the second-stage reaction; the product is fed into the third-stage isomeric dewaxing reactor for the third-stage reaction; and finally, after isomeric hot high-pressure separation and isomeric cold high-pressure separation, the product enters the distillation column for splitting to obtain bio-jet fuel.

[0012] Preferably, the mass ratio of polyvinyl alcohol, phosphoric acid and urea in (1) is 100:(70-200):(3.4-10).

[0013] Preferably, the reaction temperature in (1) is 95-100℃ and the reaction time is 6-10h.

[0014] Preferably, in (2), the mass ratio of polyvinyl phosphate, 1,5-naphthalene diisocyanate, and dibutyltin dilaurate is 100:(60-85):(0.16-0.22).

[0015] Preferably, the reaction temperature in (2) is 65-80℃ and the reaction time is 2-3h.

[0016] Preferably, in (2), the mass ratio of cross-linked polyvinyl phosphate, nickel compound, and molybdenum compound is 100:(33-57):(42-87).

[0017] Preferably, in (3), the calcination is carried out at a heating rate of 5-8℃ / min to 650-750℃ and held for 1-2 hours.

[0018] Preferably, in (3), the nickel compound is nickel nitrate or nickel chloride, and the molybdenum compound is ammonium molybdate.

[0019] Preferably, in (4) the hydrodeoxygenation reaction is carried out at a reaction pressure of 3-6 MPa and a space velocity of 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.

[0020] Preferably, in step (5), the reaction pressure is 3-5 MPa and the space velocity is 1-1.3 h⁻¹ during the first-order reaction.-1 The reaction temperature is 350-380℃, and the hydrogen-to-oil ratio is 800-900:1.

[0021] Preferably, in the second-order reaction of (5), 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.

[0022] Preferably, in (5) the reaction is carried out at a pressure of 3-5 MPa and a space velocity of 0.8-1 h⁻¹. -1 The reaction temperature is 300-320℃, and the hydrogen-to-oil ratio is 450-550:1.

[0023] The beneficial technical effects of this invention are as follows: Polyvinyl alcohol and phosphoric acid are reacted under urea catalysis to obtain polyvinyl phosphate. The hydroxyl groups of this polyvinyl phosphate are then cross-linked with 1,5-naphthalene diisocyanate to obtain cross-linked polyvinyl phosphate with a three-dimensional spatial network. Nickel and molybdenum elements are then uniformly adsorbed into the spatial network of the cross-linked polyvinyl phosphate. After high-temperature calcination, using polyvinyl alcohol and high-carbon naphthalene rings as carbon sources, a high-temperature carbonization process generates an active porous carbon matrix. Nickel and molybdenum elements and phosphate groups in situ generate highly dispersed Ni-Mo-P catalytic sites within the carbon matrix. Simultaneously, the catalyst carbon matrix has a large specific surface area and abundant porosity, exposing a large number of active catalytic centers. This significantly improves the efficiency of the hydrodeoxygenation reaction of waste oils without the need for the addition of precious metals such as platinum and ruthenium, resulting in higher mass fractions of branched alkanes and cycloalkanes in the bio-jet fuel and better combustion performance. Attached Figure Description

[0024] Figure 1 This is a process flow diagram for preparing bio-jet fuel.

[0025] Figure 2 This is a scanning electron microscope image of the hydrogenation catalyst in Example 1. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Example 1

[0028] (1) Add 1L of water, 200g of polyvinyl alcohol (model PVA0588, the same below), 220g of phosphoric acid and 10.6g of urea to a reaction vessel equipped with a reflux condenser. Heat to 100℃ and stir for 6h. Pour the solution after reaction into ethanol, filter, wash the filter cake with ethanol, and dry to obtain polyvinyl phosphate.

[0029] (2) Add 3L of N,N-dimethylformamide, 300g of polyvinyl alcohol phosphate, 207g of 1,5-naphthalene diisocyanate and 0.48g of dibutyltin dilaurate to the reaction vessel, purge with nitrogen, heat to 70°C, stir and react for 2h, pour the reaction solution into ethanol, filter, wash the filter cake with ethanol, dry, and obtain cross-linked polyvinyl alcohol phosphate.

[0030] (3) Add 15L of deionized water, 500g of cross-linked polyvinyl phosphate, 117g of nickel nitrate and 84g of ammonium molybdate tetrahydrate to the container, stir for 3h, dry to remove water, place the product in a tube furnace, introduce nitrogen gas, raise the temperature to 700℃ at a rate of 5℃ / min, keep it at the temperature for 1h, cool, and obtain the hydrogenation catalyst. Figure 2 The scanning electron microscope images show that the carbon support of the hydrogenation catalyst contains a large number of pores and has a large specific surface area.

[0031] (4) Combination Figure 2 The process flow diagram for preparing bio-jet kerosene is as follows: A hydrogenation catalyst is loaded into a hydrorefining reactor. Waste cooking oil is preheated and then introduced into the hydrorefining reactor. Hydrogen gas is introduced, and the hydrogen-to-oil ratio is controlled at 1200:1 (the hydrogen-to-oil ratio is the ratio of the standard volumetric flow rate of circulating hydrogen at the reactor inlet to the volumetric flow rate of waste cooking oil per unit time), with a pressure of 4 MPa and a space velocity of 1.5 h⁻¹. -1 The temperature is 380℃, 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.

[0032] (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 1.3 h⁻¹. -1 The 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.

[0033] Comparative Example 1

[0034] (1) Add 3L of N,N-dimethylformamide, 300g of polyvinyl alcohol, 207g of 1,5-naphthalene diisocyanate and 0.48g of dibutyltin dilaurate to the reaction vessel, purge with nitrogen, heat to 70°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.

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

[0036] (3) 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 1200:1, the pressure at 4 MPa, and the space velocity at 1.5 h⁻¹. -1 The temperature is 380℃, 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.

[0037] (4) 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 1.3 h⁻¹. -1 The 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.

[0038] Comparative Example 2

[0039] (1) Add 1L of water, 200g of polyvinyl alcohol, 220g of phosphoric acid and 10.6g of urea to a reaction vessel equipped with a reflux condenser, heat to 100°C, stir and react for 6 hours, pour the solution into ethanol, filter, wash the filter cake with ethanol, dry and obtain polyvinyl phosphate.

[0040] (2) Add 15L of deionized water, 500g of polyvinyl phosphate, 117g of nickel nitrate and 84g of ammonium molybdate tetrahydrate to the container, stir for 3h, dry to remove water, place the product in a tube furnace, introduce nitrogen gas, raise the temperature to 700℃ at a rate of 5℃ / min, keep it at the temperature for 1h, cool, and obtain the hydrogenation catalyst.

[0041] (3) 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 1200:1, the pressure at 4 MPa, and the space velocity at 1.5 h⁻¹. -1 The temperature is 380℃, 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.

[0042] (4) 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 1.3 h⁻¹. -1 The 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.

[0043] Comparative Example 3

[0044] (1) Add 15L of deionized water, 500g of cross-linked polyvinyl phosphate (prepared from Example 1), and 117g of nickel nitrate to a container, stir for 3h, dry to remove water, place the product in a tube furnace, introduce nitrogen gas, raise the temperature to 700℃ at a heating rate of 5℃ / min, keep it at the temperature for 1h, cool, and obtain the hydrogenation catalyst.

[0045] (2) 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 1200:1, the pressure at 4 MPa, and the space velocity at 1.5 h⁻¹. -1 The temperature is 380℃, 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.

[0046] (3) 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 1.3 h⁻¹.-1 The 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.

[0047] Example 2

[0048] (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.

[0049] (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.

[0050] (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.

[0051] (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 enter 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.

[0052] (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.

[0053] Example 3

[0054] (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.

[0055] (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.

[0056] (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.

[0057] (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.

[0058] (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 the distillation column for splitting to obtain bio-jet fuel.

[0059] Example 4

[0060] (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.

[0061] (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.

[0062] (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.

[0063] (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.

[0064] (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.

[0065] The composition of bio-jet fuel was tested using the ASTM D2425-21 standard, and the results are shown in Table 1.

[0066] Table 1. Composition of bio-jet fuel

[0067]

[0068] 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.

[0069] 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, cool, and obtain hydrogenation catalyst; 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; 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; 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.

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, The reaction temperature in (1) is 95-100℃ and the reaction time is 6-10h.

4. 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.

5. 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.

6. 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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