A method for producing aviation kerosene

Abstract

The present invention discloses a production method of aviation kerosene. The method of the present invention comprises the following steps: (1) aviation kerosene raw material and hydrogen enter reactor I for gas-phase hydrogenation reaction; (2) the effluent from reactor I enters reactor II after being pressurized. Among them, the gas-phase component is discharged upward from reactor II, and after being treated for hydrogen sulfide removal, a hydrogenated light component is obtained. The liquid-phase component undergoes an isomerization reaction downward, and the isomerization reaction product is discharged from the bottom of reactor II; (3) the isomerization reaction product is mixed with the hydrogenated light component to obtain an aviation kerosene product. The method of the present invention can produce high-quality aviation kerosene products with a low freezing point under the conditions of a simple process, low energy consumption, and low cost.

Description

Technical Field

[0001] The present invention belongs to the field of clean oil refining, and particularly relates to a production method of aviation kerosene. Background Art

[0002] Aviation kerosene is one of the high-value-added products in the oil refining industry. In recent years, with the development of China's civil aviation industry, the demand for aviation fuel has been continuously increasing. In the face of the continuous increasing demand for aviation kerosene production, in order to increase the production of aviation kerosene and comply with the development requirements of the industry, the main method for oil refining enterprises to increase the production of aviation kerosene is to achieve the purpose of increasing the production of aviation kerosene by means of cutting heavy straight-run kerosene fractions. However, the increase in the kerosene distillation range will increase the content of straight-chain alkanes in the kerosene fraction, resulting in the unqualified freezing point index of the aviation kerosene product, which limits the further increase in the production of aviation kerosene by means of cutting the distillation range. The existing solution is to fill a catalyst with isomerization performance in the reactor to isomerize the long straight-chain alkanes to reduce the freezing point of the aviation kerosene product. However, long-branched-chain alkanes are mainly concentrated in the heavy components of the cut, and if the full fraction of aviation kerosene is used for isomerization reaction, first, the reaction effect is not good, and second, it is easy to cause partial cracking of small molecules, reducing the yield of aviation kerosene; in addition, the severity of the reaction can also be increased to improve the properties of the aviation kerosene product, such as increasing the reaction pressure, increasing the reaction temperature, reducing the reaction space velocity, etc. However, the existing aviation kerosene unit has a relatively low pressure design level, generally 3-4 MPa, which is difficult to significantly improve the product quality, and the method of increasing the severity has a large improvement in the smoke point and is difficult to improve the freezing point index. Therefore, although the limit of the final boiling point in the aviation kerosene quality index is ≯300 °C, in order to ensure the qualification of the freezing point index, oil refining enterprises can only control the final boiling point of aviation kerosene at ≯260 °C at present. However, if the final boiling point is controlled too low, the purpose of reducing diesel and increasing the production of aviation kerosene cannot be achieved.

[0003] CN109722291A discloses a method for reducing the freezing point of high-endpoint aviation kerosene. This method uses diesel as a raw material, designs a freezing point reduction catalyst, and utilizes the synergistic effect of molecular sieves with different pore sizes to cause the isomerization reaction of long-chain hydrocarbon substances in the raw material, and by controlling the reaction temperature of pre-refining before isomerization and reducing the isomerization reaction temperature, the occurrence of over-cracking reaction is avoided, and low-freezing-point aviation kerosene and diesel products are produced. However, this method is for the isomerization of the full fraction of diesel, and the complete isomerization of straight-chain hydrocarbon substances in the material will reduce the service life of the isomerization agent to a certain extent, and will also affect the cetane number of diesel products.

[0004] CN109722293B discloses a method for co-producing jet fuel and low-freezing diesel. The raw material distillation range of this method can be between straight-run diesel and straight-run wax oil. After the raw material is fractionated for the first time, the heavy components are isomerized, and then the isomerized heavy components are fractionated again. The light components fractionated are mixed with the light components fractionated for the first time to be used as the low-freezing-point jet fuel product, and the heavy components are low-freezing diesel. By controlling the fractionation ratios of the two times and the recycle ratio of the heavy components, flexible production is achieved. However, this process is relatively complex, at least 4 fractionation and reaction devices need to be set up, and there are also stripping separations between the reactors, etc., resulting in complex operations and high energy consumption. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for producing jet fuel. The method of the present invention can produce high-quality jet fuel products with low freezing points under the conditions of simple process, low energy consumption, and low cost.

[0006] The present invention provides a method for producing jet fuel, comprising the following steps:

[0007] (1) The jet fuel raw material and hydrogen enter Reactor I for gas-phase hydrogenation reaction;

[0008] (2) The effluent from Reactor I is pressurized and then enters Reactor II. Among them, the gas-phase components are discharged upward from Reactor II. After desulfurization treatment, hydrogenated light components are obtained, and the liquid-phase components are subjected to isomerization reaction downward, and the obtained isomerization reaction products are discharged from the bottom of Reactor II;

[0009] (3) The isomerization reaction products are mixed with the hydrogenated light components to obtain jet fuel products.

[0010] Further, the properties of the jet fuel raw material are as follows: the initial boiling point is 120°C to 150°C, the final boiling point is 280°C to 300°C, the density (20°C) ≤ 0.85 g / m 3 , further 0.70 to 0.85 g / m 3 , the S content ≤ 4000 μg / g, further 500 to 3500 μg / g, the freezing point ≤ -10°C, preferably -30°C to -12°C.

[0011] Further, both Reactor I and Reactor II are fixed-bed reactors. Reactor II preferably adopts a fixed-bed reactor provided with a flash zone.

[0012] Further, a flash zone is provided in Reactor II. No catalyst is filled above and in the flash zone, and the area below the flash zone is the reaction zone. The effluent from Reactor I is pressurized and fed into the flash zone of Reactor II. The obtained gas-phase components are discharged upward from Reactor II, and the obtained liquid-phase components are subjected to isomerization reaction downward, and the obtained isomerization reaction products are discharged from the bottom of Reactor II.

[0013] Further, the operating conditions of the reactor I are as follows: the pressure is 0.1 to 3.0 MPa, preferably 0.5 to 2.0 MPa; the hydrogen-oil volume ratio is 100 to 1000, preferably 200 to 600; the temperature is 150 to 350 °C, preferably 200 to 300 °C; the volume space velocity is 0.1 to 6.0 h -1 , preferably 1.5 to 4.0 h -1 .

[0014] Further, the catalyst loaded in the reactor I includes a hydrofining catalyst. The hydrofining catalyst includes a carrier and a hydrogenation active metal; wherein the carrier is an inorganic refractory oxide, selected from one or more of alumina, amorphous silica-alumina, silica or titanium oxide, etc.; the hydrogenation active metal includes Group VIB and / or Group VIII metal components, wherein the Group VIB metal is selected from tungsten and / or molybdenum, and the Group VIII metal is selected from nickel and / or cobalt. Based on the mass of the hydrofining catalyst, the content of the Group VIB metal in terms of oxide is 10 wt% to 20 wt%, and the content of the Group VIII metal in terms of oxide is 1 wt% to 9 wt%. The hydrofining catalyst can adopt a commercial hydrofining catalyst, such as the FH-40 series catalysts developed by Fushun Research Institute of Petroleum and Petrochemicals (FRIPP) of Sinopec. For example, FH-40A and FH-40C catalysts.

[0015] Further, the effluent from the reactor I is pressurized by a compressor, and the compressor can be a conventional commercial compressor, such as a reciprocating or centrifugal compressor. Among them, the pressurization can ensure the normal feeding of the reactor II and meet the operating pressure requirements of the reactor II.

[0016] Further, the operating conditions of the reactor II are as follows: the pressure is 0.5 to 10.0 MPa, preferably 1.0 to 7.0 MPa, and further preferably 2.0 to 6.0 MPa; the temperature is 100 to 400 °C, preferably 150 to 260 °C; the volume space velocity is 0.1 to 4.0 h -1 , preferably 0.1 to 2.0 h -1 .

[0017] Further, the pressure of the reactor II is at least 0.4 MPa higher than the pressure of the reactor I, preferably 0.5 to 5.5 MPa higher, and further preferably 1.0 to 5.0 MPa higher.

[0018] Further, the catalyst loaded in Reactor II is a hydroisomerization catalyst, and the isomerization catalyst includes a carrier and a hydrogenation active metal; wherein the carrier is an inorganic refractory oxide and a molecular sieve. The inorganic refractory oxide is selected from one or more of alumina, amorphous silica-alumina, silica, titanium oxide, etc., preferably alumina; the molecular sieve is selected from at least one of ZSM-5, β zeolite, USY, Y, ZSM-3, ZSM-20, MCM-68, SAPO-5, SAPO-37, mordenite, etc. The hydrogenation active metal includes a Group VIB metal component or a Group VIII metal component. The Group VIB metal component is selected from tungsten, and the Group VIII is selected from nickel, platinum or palladium, preferably nickel. Based on the mass of the catalyst, the content of the hydrogenation active metal is 0.1 wt% to 10.0 wt%, the content of the molecular sieve is 5 wt% to 85 wt%, and the content of the inorganic refractory oxide is 10 wt% to 60 wt%. For example, FDW-3 developed by Fushun Research Institute of Petroleum and Petrochemicals, SINOPEC.

[0019] Further, the gas-phase components discharged from Reactor II are heat-exchanged in a heat exchanger and then enter a high-pressure separator for separation to obtain hydrogenated light components and hydrogen containing hydrogen sulfide.

[0020] Further, the gas-phase components discharged from Reactor II are cooled to 50 - 200 °C, preferably 40 - 120 °C, in a heat exchanger.

[0021] Further, the hydrogen containing hydrogen sulfide separated by the high-pressure separator can be recycled back to Reactor I to continue participating in the reaction after removing hydrogen sulfide and ammonia.

[0022] Further, the freezing point of the jet fuel product is ≯ -47 °C.

[0023] Compared with the prior art, the method of the present invention has the following advantages:

[0024] (1) Compared with the conventional fixed-bed jet fuel hydrogenation technology, since Reactor I of the present invention is close to atmospheric pressure conditions, there is no need to boost pressure during the hydrogen recycling process, eliminating the recycle hydrogen compressor and the involved heat exchange process, which can significantly reduce energy consumption and the construction investment of the device. From the perspective of the chemical reaction rate, the present invention is a combined process of gas-phase and liquid-phase reactions. The reactions that occur are gas-phase and liquid-phase reactions, and the reaction rate is significantly higher than that of three-phase reactions.

[0025] (2) Compared with the conventional process of using a refining agent and a hydroisomerization catalyst in series, the method of the present invention can improve the freezing point of jet fuel, avoid the contact of the whole fraction of jet fuel with the isomerization catalyst, optimize the isomerization reaction environment and reduce the reaction space velocity by only liquefying the macromolecular straight-chain alkanes before the isomerization reaction, thereby improving the reaction efficiency. Moreover, the contents of hydrogen sulfide and ammonia in the isomerization reaction products are significantly reduced, which can extend the service life of the hydroisomerization catalyst. Compared with the conventional process of separately loading the refining agent and the isomerization catalyst in two series-connected reactors, the stripping equipment between the two reactors can be omitted. Since the material flowing out of Reactor I is in a high-temperature and low-pressure state, during the pressurization and liquefaction process by the compressor, it can promote the dissolution of hydrogen in the liquefied oil product. And because the gas-phase hydrogenation reactor is in a reaction state of low pressure and high hydrogen-oil ratio, at a relatively high reaction temperature, while desulfurizing the reaction material, there is enough hydrogen remaining, which can also play a role in mixing hydrogen with the oil and gas. Moreover, due to the different dissolution laws of hydrogen, hydrogen sulfide and ammonia generated after the reaction in the oil product, that is, at high temperature, the solubility of hydrogen is high and the solubility of hydrogen sulfide is low, so the hydrogen concentration in the liquefied liquid phase is high and the hydrogen sulfide concentration is low. It can directly enter the subsequent liquid-phase hydrogenation reactor without further stripping, and can ensure a higher hydrogen content in the liquid phase to ensure the saturation reaction of aromatic hydrocarbons and other substances in Reactor II.

[0026] (3) The present invention optimizes the reaction types and reaction conditions in each reactor, and overall reduces the reaction severity and simplifies the process flow. As a pretreatment reactor for Reactor II, Reactor I first removes the substances in the jet fuel raw material that are easy to react under low-pressure conditions. In the material flowing out of Reactor I, the unreacted macromolecules (mainly long straight-chain alkanes) are slightly pressurized and liquefied by a compressor and enter Reactor II as liquefied heavy components for the isomerization reaction. Since Reactor I is under the condition of high hydrogen-oil ratio and hydrogen is highly dissolved in the oil product during the pressurization process by the compressor, there is no need to add additional hydrogen-dissolving equipment before entering the liquid-phase hydrogenation reactor. Moreover, since the small molecules have already undergone a hydrogenation reaction in Reactor I, only a pressure sufficient to liquefy the macromolecules is required during the pressurization process, without the need for high pressure, which reduces the severity of the liquid-phase hydrogenation reaction. In addition, since the small molecules have been removed in Reactor I, the content of long straight-chain alkanes in the macromolecules entering Reactor II is significantly increased, which is conducive to targeted removal, promotes the right shift of the chemical equilibrium, increases the conversion rate of long straight-chain alkanes, and thus achieves the purpose of reducing the freezing point of jet fuel.

[0027] (4) In the effluent of Reactor I involved in the present invention, the reacted small molecules do not liquefy during the pressurization process of the compressor, and are liquefied by heat exchange and condensation cooling before entering the high-pressure separator. This liquefaction method is conducive to the separation of hydrogen and raw materials, can recover a large amount of hydrogen for recycling, and improve the hydrogen utilization rate. The liquefied small molecules are hydrogenated light components, which can enter the subsequent stripping system after being mixed with the isomerization reaction products. The entire reaction system does not require the hydrogen compressor in the fixed-bed reaction system and the circulating oil pump in the liquid-phase hydrogenation reaction system, simplifies the process flow, reduces the investment cost, and at the same time, improves the reaction efficiency and reduces the reaction severity.

[0028] (5) The present invention realizes the separation and separate optimization of hydrogenation and isomerization reactions. In Reactor I, the hydrogenation reaction of small molecule substances under low pressure mainly occurs. Since the hydrogen partial pressure in Reactor I is relatively high, cyclic substances and long-chain alkanes in the oil are not easily adsorbed on the catalyst surface, avoiding the occupation of the active sites on the catalyst surface and the dehydrogenation reaction of cyclic substances to generate aromatics. At the same time, the reaction pressure in the liquid-phase reaction system increases, which is more conducive to the targeted reaction of the isomerization catalyst. Brief Description of the Drawings

[0029] Figure 1 is a schematic process flow diagram of the aviation kerosene production of the present invention;

[0030] Among them, 1 - aviation kerosene raw material and hydrogen; 2 - Reactor I, 3 - effluent of Reactor I; 4 - compressor; 5 - Reactor II; 6 - isomerization reaction product; 7 - gas-phase component; 8 - heat exchanger; 9 - high-pressure separator; 10 - hydrogen containing hydrogen sulfide; 11 - hydrogenated light component; 12 - stripping system; 13 - low-freezing-point aviation kerosene product. Detailed Embodiments

[0031] The present invention will be further described below in conjunction with embodiments, but it should be understood that the protection scope of the present invention is not limited by the embodiments.

[0032] In the present invention, unless otherwise clearly stated, percentages and percentage contents are by mass.

[0033] In the present invention, the freezing point of aviation kerosene is measured by the method of GB / T 2430, and the analytical instrument is the SH12C automatic aviation kerosene freezing point measuring instrument.

[0034] The following will be combined with Figure 1 to describe the process flow of the present invention in detail.

[0035] The jet fuel feedstock and hydrogen 1 enter reactor I 2, where a gas-phase hydrogenation reaction occurs to obtain the effluent 3 from reactor I; it then enters compressor 4, and after being pressurized by compressor 4, it enters reactor II 5. The liquid-phase components therein undergo an isomerization reaction downward to obtain an isomerization reaction product 6, and the gas-phase components 7 are discharged upward from reactor II and enter heat exchanger 8, and then enter high-pressure separator 9, where they are separated into hydrogen 10 containing hydrogen sulfide and hydrogenated light components 11. The isomerization reaction product 6 and the hydrogenated light components 11 are mixed and enter the stripping system 12, and finally a low-freezing-point jet fuel product 13 can be obtained.

[0036] Examples 1 - 3

[0037] Adopt the Figure 1 process flow schematic diagram as shown. Two 100 mL fixed-bed hydrogenation reactors are connected in series, namely reactor I and reactor II. A reciprocating compressor with a conventional power is set between the reactors. Reactor I is filled with 50 mL of Mo-Ni type hydrogenation catalyst A, and reactor II is filled with 50 mL of isomerization catalyst B. A gas-phase outlet is set above reactor II, which is connected to a heat exchanger (to cool the gas-phase components to 130 °C) and a high-pressure separator. The liquid-phase outlet pipeline set at the bottom of reactor II is connected to the liquid-phase outlet pipeline at the bottom of the high-pressure separator, and they enter the subsequent stripping system together.

[0038] The properties of the catalysts are shown in Table 1, the properties of the feedstock oil are shown in Table 2, and the reaction process conditions and results are shown in Table 3.

[0039] Comparative Example 1

[0040] Adopt a conventional fixed-bed hydrogenation process flow, and set up a hydrogenation reactor, namely reactor 1. The feedstock oil is the same as that in Example 1, and both the feedstock oil and hydrogen enter reactor 1 from the top of reactor 1. 100 mL of catalyst A is filled in reactor 1. The reaction process conditions and results are shown in Table 3.

[0041] Comparative Example 2

[0042] Adopt a two-stage hydrogenation process flow, and set up reactor 1 and reactor 2. The same feedstock as in Example 1 is introduced into hydrogenation reactor 1 (filled with 50 mL of hydrogenation catalyst A) and hydrogenation reactor 2 (filled with 50 mL of isomerization catalyst B) in sequence. A stripping device needs to be set between the two hydrogenation reactors.

[0043] Comparative Example 3

[0044] Adopt the same hydrogenation process flow as in Example 1, with the only difference being that a high-power reciprocating compressor is set between the first and second reactors and the control of process conditions. The reaction process conditions and results are shown in Table 3.

[0045] Table 1 Physicochemical properties of the catalysts

[0046] Catalyst Number A B Grade FH-40A FDW-3 Active Metal Ni-Mo Ni NiO, wt% 4.5 2.2 <![CDATA[MoO 3 or WO 3 , wt%]]> 15 - Shape Trifolium Cylindrical Bar Diameter, mm 2.0 1.5 <![CDATA[Specific surface area, m 2 ·g -1 > 170 180 <![CDATA[Pore volume, mL·g -1 > 0.45 0.40

[0047] Table 2 Properties of feedstock oil

[0048]

[0049]

[0050] Table 3 Hydrotreating process conditions and results

[0051]

[0052] As can be seen from Table 3, the conventional fixed-bed hydrotreating technology uses jet fuel with a relatively high dry point as the feedstock. When the operating conditions of an industrial unit are adopted, due to the high content of straight-chain alkanes, the freezing point index cannot meet the requirements. When the two-stage hydrotreating technology is used, after the first-stage hydrotreating, stripping is required to remove hydrogen sulfide and ammonia, and then the whole fraction enters the hydrotreating reactor 2. Under the same throughput and catalyst loading, it is equivalent to increasing the volumetric space velocity of the straight-chain alkane part, which affects the reaction effect. At the same time, since the isomerization is carried out on the whole fraction, the service life of the catalyst will be reduced to a certain extent. When the hydrogen-oil ratio in reactor 1 is too large, the partial pressure of the feedstock will be reduced to a certain extent, which affects the adsorption of small-molecule sulfur on the catalyst surface in reactor 1, resulting in poor desulfurization effect. At the same time, the subsequent liquefaction process also becomes more difficult and requires an increase in pressure to achieve, resulting in increased energy consumption. By combining reactor I and reactor II, the present invention realizes low-pressure reaction conditions. The entire reaction system does not require the hydrogen compressor in the fixed-bed reaction system and the recycle oil pump in the liquid-phase hydrotreating reaction system. At the same time, since the concentrations of hydrogen sulfide and ammonia in the liquid-phase hydrotreating reaction material are controlled under these conditions, no gas equipment is required between the two reactors, which simplifies the process flow, reduces the investment cost, improves the reaction efficiency, reduces the reaction severity, and can produce high-quality low-freezing-point jet fuel products using the cut heavy jet fuel fraction with a relatively high dry point as the feedstock.

Claims

1. A production method of aviation kerosene, characterized in that, the method comprises the following steps: (1) The aviation kerosene raw material and hydrogen enter Reactor I for gas-phase hydrogenation reaction; wherein, Reactor I serves as a pretreatment reactor for Reactor II, and the substances in the aviation kerosene raw material that are easy to react are removed first under low-pressure conditions. In the material flowing out of Reactor I, the unreacted macromolecules are pressurized and liquefied by a compressor and enter Reactor II for isomerization reaction; (2) The effluent from Reactor I is pressurized and then enters Reactor II. Among them, the gas-phase components are discharged upward from Reactor II. After desulfurization treatment of hydrogen sulfide, hydrogenated light components are obtained. The liquid-phase components go downward for isomerization reaction, and the obtained isomerization reaction products are discharged from the bottom of Reactor II; (3) The isomerization reaction products are mixed with the hydrogenated light components to obtain aviation kerosene products, and the freezing point of the aviation kerosene products is ≤ -47°C; The operating conditions of the reactor I are as follows: the pressure is 0.1 - 2.0 MPa; the hydrogen-to-oil volume ratio is 100 - 1000; the temperature is 150 - 350 °C; the volume space velocity is 0.1 - 6.0 h -1 ; The operating conditions of the reactor II are as follows: the pressure is 1.0 to 10.0 MPa; the temperature is 100 to 400 °C; the volume space velocity is 0.1 to 4.0 h -1 .

2. The method according to claim 1, characterized in that, The properties of the jet fuel feedstock are as follows: the initial boiling point is 120°C to 150°C, the final boiling point is 280°C to 300°C, the density at 20°C is not more than 0.85 g / m 3 , S is not more than 4000 μg / g, and the freezing point is not more than -10°C.

3. The method according to claim 2, characterized in that, the properties of the aviation kerosene raw material are as follows: the S content is 500 - 3500 μg / g, and the freezing point is -30°C to -12°C.

4. The method according to claim 1, characterized in that, both Reactor I and Reactor II are fixed-bed reactors; Reactor II adopts a fixed-bed reactor provided with a flash evaporation zone.

5. The method according to claim 1, characterized in that, The operating conditions of the reactor I are as follows: the pressure is 0.5 - 2.0 MPa; the hydrogen-oil volume ratio is 200 - 600; the temperature is 200 - 300 °C; the volume space velocity is 1.5 - 4.0 h -1 .

6. The method according to claim 1, characterized in that, The operating conditions of the reactor II are as follows: the pressure is 1.0 - 7.0 MPa; the temperature is 150 - 260 °C; the volume space velocity is 0.1 - 2.0 h -1 .

7. The method according to claim 1, characterized in that, the operating conditions of Reactor II are as follows: the pressure is 2.0 - 6.0 MPa.

8. The method according to claim 6, characterized in that, the pressure of Reactor II is at least 0.4 MPa higher than the pressure of Reactor I.

9. The method according to claim 8, characterized in that, the pressure of Reactor II is 0.5 - 5.5 MPa higher than the pressure of Reactor I.

10. The method according to claim 8, characterized in that, the pressure of Reactor II is 1.0 - 5.0 MPa higher than the pressure of Reactor I.

11. The method according to claim 1, characterized in that, the gas-phase components discharged from Reactor II are heat-exchanged through a heat exchanger and then enter a high-pressure separator for separation to obtain hydrogenated light components and hydrogen gas containing hydrogen sulfide.

12. The method according to claim 7, characterized in that, the gas-phase components discharged from Reactor II are cooled to 50 - 200°C through a heat exchanger.

13. The method according to claim 12, characterized in that, the gas-phase components discharged from Reactor II are cooled to 40 - 120°C through a heat exchanger.

14. The method according to claim 1, characterized in that, the catalyst filled in Reactor I includes a hydrofining catalyst; the catalyst filled in Reactor II is a hydroisomerization catalyst.

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