A method for producing clean diesel fuel

Abstract

This invention discloses a method for producing clean diesel fuel. The method includes: (1) diesel feedstock and hydrogen entering a hydrotreating reactor for hydrodesulfurization reaction; (2) the effluent from the hydrotreating reactor is heated by a heat exchanger with the diesel feedstock, and then passes through a high-pressure separator to obtain gaseous and liquid phase components. The liquid phase component is then stripped by a stripping tower, and the liquid phase component after removing impurities enters an adsorption dearomatization reactor filled with aromatics adsorbent from top to bottom; (3) after the adsorption dearomatization reactor undergoes an adsorption dearomatization reaction, the unadsorbed material is discharged from the bottom of the adsorption dearomatization reactor, which is the clean diesel fuel product. This invention can target the reaction characteristics of sulfides and aromatics in the feedstock by using different reaction methods and reaction conditions for targeted removal. It can not only achieve ultra-deep desulfurization, but also separate aromatic components in oil products with low hydrogen consumption. At the same time, it can produce clean diesel fuel products with low equipment energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of oil refining and chemical industry, and specifically relates to a method for producing clean diesel fuel. Background Technology

[0002] With economic development, the world's demand for oil is increasing, bringing convenience to people but also causing environmental pollution. SOx and NOx generated from the combustion of oil products are significant contributors to acid rain, which not only harms our living environment and human health but also corrodes buildings. Furthermore, sulfur compounds negatively impact oil processing, poisoning catalysts and affecting their activity. Currently, with growing environmental awareness, different countries are accelerating the upgrading of oil quality; China completed the upgrade from National III to National VI standards in a very short time. At present, crude oil is becoming increasingly heavy and of lower quality, leading to a corresponding decline in the quality of subsequent distillate oils, primarily characterized by higher levels of sulfides, nitrogen oxides, and polycyclic aromatic hydrocarbons, placing enormous pressure on subsequent processing and conversion.

[0003] According to the technical requirements for China V and China VI vehicle diesel, the quality requirements for polycyclic aromatic hydrocarbons (PAHs) in vehicle diesel are becoming increasingly stringent. The China VI vehicle diesel standard requires that the PAH content not exceed 7%, and the upcoming diesel standard will have even stricter standards for PAHs.

[0004] US5114562A discloses a two-stage processing flow for hydrodesulfurization and aromatics saturation of middle distillate oil. This method uses two independent reactors. The first reactor performs hydrodesulfurization, and the desulfurized product enters a stripping tower where hydrogen stripping removes the generated H2S and NH3. The product then enters the second reactor for aromatics hydrosaturation. While this method is technically mature, the saturation of aromatics in the oil is not selective; under these conditions, even monocyclic aromatics can easily reach deep saturation, resulting in significant hydrogen and energy consumption. Furthermore, the process is complex, difficult to operate, and requires substantial investment.

[0005] CN103214332A discloses a method for producing light aromatics and high-quality oil products from catalytic cracking diesel. The method involves extracting the catalytic cracking diesel using a solvent to obtain an extract oil rich in polycyclic aromatics and a raffinate oil rich in alkanes. The extract oil is then hydrorefined and hydrocrackinged to produce light aromatics and high-octane gasoline fractions. This method not only yields light aromatics but also produces high-cetane diesel and high-octane gasoline. However, because catalytic cracking diesel contains a significant amount of olefin compounds, as well as sulfur and nitrogen compounds, the extraction solvent is consumed in large quantities, which can affect the extraction efficiency. If the resulting raffinate oil is not refined, the high sulfur and nitrogen content makes it difficult to meet the quality requirements for clean fuels.

[0006] CN1156752A discloses a method for hydroconversion of diesel fractions. This method uses a hydroconversion catalyst containing molecular sieves and employs a single-stage, tandem single-stage, and two-stage hydroconversion process to remove aromatics, desulfurize, and improve the cetane number of inferior diesel. However, the diesel produced by this method has low specifications, with a sulfur content of less than 500 ppm and an aromatic content of less than 20 wt%. A large amount of aromatic components in the catalytic cracking diesel feedstock are hydrogenated to saturation, resulting in high hydrogen consumption in the hydrogenation reaction and failure to utilize different aromatic components. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for producing clean diesel fuel. This invention can target the removal of sulfides and aromatics from raw materials using different reaction methods and conditions, based on their reaction characteristics. It not only achieves ultra-deep desulfurization but also separates aromatic components from the oil with low hydrogen consumption. Furthermore, it produces clean diesel fuel with low equipment energy consumption.

[0008] This invention proposes a method for producing clean diesel fuel, comprising the following steps:

[0009] (1) Diesel feedstock and hydrogen enter the hydrotreating reactor to carry out hydrodesulfurization reaction;

[0010] (2) The material flowing out of the hydrogenation reactor exchanges heat with the diesel feedstock through a heat exchanger, and then passes through a high-pressure separator to obtain gas phase components and liquid phase components. The liquid phase components are then stripped by a stripping tower. The liquid phase components after removing impurities enter the adsorption dearomatization reactor filled with aromatic adsorbent from top to bottom.

[0011] (3) After the adsorption and dearomatization reactor undergoes the adsorption and dearomatization reaction, the unadsorbed material is discharged from the bottom of the adsorption and dearomatization reactor, which is the clean diesel product.

[0012] Furthermore, the adsorption-dearomatization reactor comprises at least two, preferably two to four, adsorption-dearomatization reactors operating in parallel and rotating. When the aromatic adsorbent in one of the adsorption-dearomatization reactors reaches 80% to 90% of its theoretical saturated adsorption capacity, the aromatic adsorbent is regenerated, and the reactor is switched to another in parallel for adsorption-dearomatization reaction, and so on.

[0013] Furthermore, the regeneration method includes: adding a desorbing agent to the adsorption-dearomatization reactor to desorb the aromatic components adsorbed by the adsorbent; after the desorption process is completed, the desorbing agent and the desorbed aromatic components are discharged from the adsorption-dearomatization reactor and enter a fractionation tower for separation, separating the desorbing agent and the aromatic components. The separated desorbing agent can be reused.

[0014] Furthermore, the eluent is preferably one or more of toluene, cyclohexane, etc.

[0015] Furthermore, the ratio of the amount of the desorbent to the mass of the diesel feedstock being treated is 2 to 10:1.

[0016] Further, in step (1), the properties of the diesel feedstock include: a distillation range of 180–370°C, an S content ≤15000 μg / g, preferably ≤12000 μg / g, an N content ≤800 μg / g, preferably ≤500 μg / g, and a polycyclic aromatic hydrocarbon content ≤30 wt%, preferably 10 wt%–20 wt%. The diesel feedstock is one or more of straight-run diesel, catalytic diesel, coking diesel, etc.

[0017] Furthermore, in step (1), the hydrogenation reactor is a gas-phase hydrogenation reactor.

[0018] Further, in step (1), the conditions for the hydrodesulfurization reaction include: a pressure of 0.1–6.0 MPa, preferably 1.0–3.0 MPa; a temperature of 260–400°C, preferably 320–380°C; a hydrogen-to-oil volume ratio of 100–800, preferably 300–600; and a volume hourly space velocity of 0.5–3.0 h⁻¹. -1 Preferably 0.5 to 1.5 hours -1 .

[0019] Further, in step (1), the catalyst packed in the hydrogenation reactor is a catalyst with alkyl transfer desulfurization function. The catalyst includes a support and active metal components. The support is alumina, and the active metal components are Mo and Co. Based on the mass of the catalyst, the content of the support is 50%–92%, the mass content of the active metal component Mo (based on oxides) is 5%–30%, and the mass content of the active metal component Co (based on oxides) is 3%–20%. The specific surface area of ​​the catalyst is ≥200 m². 2 / g, with a pore volume of ≥0.30mL / g. For example, the Mo-Co type FHUDS-5 catalyst developed by FRIPP.

[0020] Furthermore, in step (2), the effluent from the hydrogenation reactor is heated by a heat exchanger with the diesel feedstock, and the effluent from the hydrogenation reactor is cooled to 100-300°C, preferably 150-250°C.

[0021] Furthermore, in step (2), the gaseous components separated by the high-pressure separator can directly enter the circulating hydrogen desulfurization system, or they can enter from the bottom of the adsorption dearomatic reactor to carry the desorbent mixture remaining in the aromatic adsorbent out of the adsorption dearomatic reactor, and after being cooled by condenser II, the desorbent and gaseous stream are separated. The separated desorbent is reused, and the separated gaseous stream enters the circulating hydrogen desulfurization system.

[0022] Furthermore, in step (2), the liquid phase component is stripped by a stripping tower, and the impurities removed are components such as hydrogen sulfide and ammonia.

[0023] Furthermore, in step (2), after the liquid phase component is stripped by the stripping tower, the resulting liquid phase stream can first pass through condenser I to cool down to the temperature required by the adsorption dearomatization reactor before entering the adsorption dearomatization reactor from top to bottom.

[0024] Furthermore, the reaction conditions of the adsorption-dearomatization reactor include: a pressure of 0–2 MPa, preferably 0.1–0.5 MPa; a temperature of 10–100 °C, preferably 20–80 °C; and a volume hourly space velocity of 0.1–1 h⁻¹. -1 .

[0025] Further, the aromatic hydrocarbon adsorbent comprises a support and a modified metal, wherein the support is alumina and / or silicon oxide; the modified metal may be one or more of Group IB, Group IIB, Group VIB, and Group VIII, preferably Ni, Cu, or Zn. Based on the mass of the aromatic hydrocarbon adsorbent, the content of the support is 80%–99%, and the content of the modified metal, calculated as oxides, is 1%–20%.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The process method of the present invention couples gas-phase desulfurization and adsorption-based dearomatization processes, which significantly reduces the hydrogen consumption in the production of high-quality diesel. The hydrotreating reactor is filled with a specific Mo-Co type catalyst, which is conducive to the occurrence of the direct desulfurization pathway (DDS) and can remove most of the sulfides in the feedstock. Since the reaction pressure of the hydrotreating reactor is low, it is not conducive to the adsorption of aromatics on the catalyst. Moreover, the reaction temperature is high, and the hydrogenation saturation of aromatics is limited by thermodynamic equilibrium, which is not conducive to the hydrogenation saturation reaction of aromatics. Under these conditions, while achieving a significant removal of sulfides in the oil, the saturation of aromatics is avoided, and the aromatics are enriched. The adsorption-based dearomatization reaction can significantly reduce the hydrogen consumption of the reaction.

[0028] (2) Most of the sulfides can be removed by gas-phase hydrodesulfurization reaction. For some sulfides that are more difficult to remove, such as 4,6-dimethyl-dibenzothiophene and 2,4,6-trimethyl-dibenzothiophene, the sulfur atoms are affected by the methyl group and are subject to steric hindrance, making it difficult to remove the sulfides. However, the molecular structure of this type of sulfide contains aromatic groups. When aromatic adsorbent is packed in the adsorption dearomatization reactor, while removing aromatics, some unreacted sulfides can also be adsorbed and removed for heavier sulfides due to their molecular structure characteristics. This results in diesel products with lower sulfur content and components with higher alkane content after aromatic removal, which can significantly improve the cetane number of diesel.

[0029] (3) The hydrogenation reactor has a high reaction temperature, while the adsorption-de-aromatization reactor has a lower temperature. By installing a heat exchanger between the two reactors, the high-temperature effluent from the hydrogenation reactor can be exchanged with the diesel feedstock, achieving rational energy utilization. After heat exchange, the material can be directly fed into the stripping tower to remove impurities such as ammonia from the hydrogenation reactor effluent, avoiding the influence of ammonia in the material on the adsorption of aromatics. At the same time, after the adsorption-de-aromatization reactor is purged with a desorbent, the adsorbed polycyclic aromatic hydrocarbon components are desorbed. The gaseous component separated by the separator, i.e., high-temperature hydrogen, enters from the bottom of the adsorption-de-aromatization reactor, carrying the residual desorbent out of the reactor. After condensation, it becomes a liquid-phase desorbent, and the gaseous material can recover hydrogen through the circulating hydrogen desulfurization system. While making full use of heat, it can also carry the residual desorbent in the aromatic adsorbent out of the reactor, greatly improving the adsorption capacity of the adsorbent for aromatics during circulation. Attached Figure Description

[0030] Figure 1 The production process flow diagrams for clean diesel oil in Examples 1-3 of this invention are shown below.

[0031] Among them, 1-diesel feedstock, 2-hydrogenation reactor, 3-heat exchanger, 4-high pressure separator, 5-gas phase component, 6-liquid phase component, 7-stripping tower, 8-stripping tower top gas, 9-stripped liquid phase component, 10-condenser I, 12a / 12b-adsorption dearomatization reactor, 14-condenser II, 15-extractant, 18-clean diesel fuel, 19-fractionation tower, 20-aromatic component. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments, but it should be understood that the scope of protection of the present invention is not limited to the embodiments. In the present invention, unless otherwise expressly stated, percentages and contents are all expressed by mass.

[0033] The following is combined Figure 1 The process flow of this invention is described in detail. Wherein, Figure 1 Some devices are omitted from the drawing, such as the heating furnace and control valves.

[0034] Diesel feedstock 1 exchanges heat with the effluent from the hydrotreating reactor via heat exchanger 3. After mixing with hydrogen and heating in a heater, it enters the hydrotreating reactor 2 for hydrodesulfurization. The reacted material is cooled by heat exchanger 3 and then enters the high-pressure separator 4, where gaseous component 5 and liquid component 6 are separated. Liquid component 6 enters the stripping tower 7. After stripping, liquid component 9 is cooled by condenser I10 and then enters the adsorption dearomatization reactor 12a, which is filled with aromatic adsorbent, from top to bottom for adsorption and desorption reaction. The unadsorbed component 18 is used as clean diesel product. The separated gaseous component 5 can directly enter the circulating hydrodesulfurization system, or it can enter from the bottom of the adsorption dearomatization reactor 12a, carrying the desorbent mixture remaining in the aromatic adsorbent out of the adsorption dearomatization reactor. After being cooled by condenser II 14, the desorbent 15 is separated, and the gaseous stream 16 enters the circulating hydrodesulfurization system.

[0035] When the aromatic adsorbent in the adsorption-de-aromatization reactor 12a reaches 80% to 90% of its theoretical saturated adsorption capacity, the above operation is performed in the adsorption-de-aromatization reactor 12b by means of a control valve. At the same time, the aromatic adsorbent in the adsorption-de-aromatization reactor 12a is regenerated. The desorbent 15 enters from the top of the adsorption-de-aromatization reactor 12a to desorb the aromatic components adsorbed by the adsorbent. The excess desorbent and the desorbed aromatic components 17 enter the fractionation tower 19 for separation, and the desorbent 15 and the aromatic components 20 are separated.

[0036] Examples 1-3

[0037] use Figure 1 The process flow is as follows: The hydrogenation reactor is a gas-phase hydrogenation reactor, loaded with 100 mL of Mo-Co type catalyst A. The support for catalyst A is alumina, and the active metal components are Mo and Co. The support content is 74%, the active metal Mo content (calculated as oxide) is 21%, the active metal Co content (calculated as oxide) is 5%, and the remainder is the support. Adsorption-dearomatization reactors a and b are each loaded with 100 mL of aromatic hydrocarbon adsorbent. The aromatic hydrocarbon adsorbent includes alumina and silica supports, and the modified metal is Ni. The Ni content (calculated as NiO) is 2.2%, the alumina content is 48.9%, and the silica content is 48.9%. The desorbent used is a mixture of 30 v% toluene and 70 v% cyclohexane. The switching time between adsorption-dearomatization reactors a and b is 2000 s, and the mass ratio of diesel feedstock to desorbent per cycle is 1:2.5.

[0038] The feedstock was conventional three-line straight-run diesel. Catalyst properties are shown in Table 1, diesel feedstock properties are shown in Table 2, and reaction process conditions and evaluation results are shown in Table 3.

[0039] Comparative Example 1

[0040] A conventional fixed-bed hydrogenation reactor was used, and the reaction was carried out under low-pressure and high-temperature conditions. 100 mL of Mo-Co type catalyst A was loaded, and the reactor was followed by a separator, stripping, and other standard processes. Hydrogen gas, after being desulfurized, was pressurized and recycled using a circulating hydrogen compressor. The diesel feedstock was the same as in Examples 1-3, and the reaction process conditions and results are shown in Table 3.

[0041] Comparative Example 2

[0042] A conventional fixed-bed hydrogenation reactor was used, and the reaction was carried out under normal conditions. 100 mL of Mo-Ni type catalyst B was loaded, and the reactor was followed by a separator, stripping, and other standard processes. Hydrogen gas, after being desulfurized, was pressurized and recycled using a circulating hydrogen compressor. The diesel feedstock was the same as in Examples 1-3, and the reaction process conditions and results are shown in Table 3.

[0043] Comparative Example 3

[0044] A conventional diesel fixed-bed hydrotreating process was adopted, with two hydrotreating reactors. The first reactor was loaded sequentially from top to bottom with 35 mL of Mo-Ni type catalyst B and 35 mL of Mo-Co type catalyst A (same as in Examples 1-3), while the second reactor was loaded with 30 mL of noble metal dearomatization catalyst C. A hydrogen stripping system was installed between the two reactors, and the high-precision, low-precision, and stripping processes were normally followed after the second reactor. The hydrogen, after being desulfurized, was pressurized and recycled using a circulating hydrogen compressor. The diesel feedstock was the same as in Examples 1-3, and the reaction process conditions and results are shown in Table 3.

[0045] Table 1. Physicochemical properties of catalysts

[0046] Catalyst number A B C Active metals Mo-Co Mo-Ni Pt <![CDATA[MoO3,wt%]]> 21 24 - CoO, wt% 5 - - NiO, wt% - 5 - Pt, wt% 0.58 shape Clover Clover cylindrical bar Diameter, mm 1.1～1.3 1.1～1.3 1.2 <![CDATA[Specific surface area, m 2 ·g -1 > 210 192 180 <![CDATA[Pore volume, mL·g -1 > 0.35 0.34 0.35

[0047] Table 2 Properties of Crude Oil

[0048] Oil properties <![CDATA[Density (20 °C), g·cm -3 > 0.8566 Distillation range, ℃ 209～366 Sulfur content, μg / g 11060 Nitrogen content, μg / g 368 Total aromatics, wt% 30.7 Polycyclic aromatic hydrocarbons (wt%) 13.2

[0049] Table 3 Hydrogenation process conditions and results

[0050]

[0051]

[0052] The specific embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing clean diesel fuel, characterized in that, Includes the following steps: (1) Diesel feedstock and hydrogen enter the hydrotreating reactor to carry out hydrodesulfurization reaction; (2) The material flowing out of the hydrogenation reactor exchanges heat with the diesel feedstock through a heat exchanger, and then passes through a high-pressure separator to obtain gas phase components and liquid phase components. The liquid phase components are then stripped by a stripping tower. The liquid phase components after removing impurities enter the adsorption dearomatization reactor filled with aromatic adsorbent from top to bottom. (3) After the adsorption and dearomatization reactor undergoes the adsorption and dearomatization reaction, the unadsorbed material is discharged from the bottom of the adsorption and dearomatization reactor, which is the clean diesel product. In step (1), the hydrogenation reactor is a gas-phase hydrogenation reactor; In step (1), the conditions for the hydrodesulfurization reaction include: pressure of 0.1~3.0 MPa, temperature of 260~400℃, hydrogen-to-oil volume ratio of 100~800, and volume hourly space velocity of 0.5~3.0 h⁻¹. -1 ; In step (1), the catalyst packed in the hydrogenation reactor is a catalyst with alkyl transfer desulfurization function; the catalyst with alkyl transfer desulfurization function includes a support and an active metal component, the support is alumina, and the active metal components are Mo and Co. Based on the mass of the catalyst, the content of the support is 50%~92%, the mass content of the active metal component Mo (based on oxides) is 5%~30%, and the mass content of the active metal component Co (based on oxides) is 3%~20%. The specific surface area of ​​the catalyst is ≥200 m². 2 / g, pore volume is ≥0.30mL / g; In step (1), the properties of the diesel feedstock include: a distillation range of 180~370℃, sulfur content ≤15000μg / g, nitrogen content ≤800μg / g, and polycyclic aromatic hydrocarbon content ≤30wt%; The reaction conditions of the adsorption-dearomatization reactor include: pressure of 0~2MPa, temperature of 10~100℃, and volume hourly space velocity of 0.1~1h. -1 .

2. The method according to claim 1, characterized in that, The adsorption dearomatization reactor comprises at least two adsorption dearomatization reactors operating in parallel and rotating.

3. The method according to claim 1, characterized in that, The adsorption dearomatization reactor comprises 2 to 4 adsorption dearomatization reactors operating in parallel and rotating.

4. The method according to claim 2, characterized in that, The method for regenerating the adsorption dearomatization reactor includes: adding a desorbing agent to the adsorption dearomatization reactor to desorb the aromatic components adsorbed by the adsorbent; after the desorption process is completed, the desorbing agent and the desorbed aromatic components are discharged from the adsorption dearomatization reactor and enter a fractionation tower for separation, separating the desorbing agent and the aromatic components.

5. The method according to claim 4, characterized in that, The exfoliating agent is one or both of toluene and cyclohexane.

6. The method according to claim 1, characterized in that, In step (1), the properties of the diesel feedstock include: S content ≤ 12000 μg / g, N content ≤ 500 μg / g, and polycyclic aromatic hydrocarbon content of 10wt%~20wt%.

7. The method according to claim 1, characterized in that, In step (1), the conditions for the hydrodesulfurization reaction include: pressure of 1.0~3.0 MPa, temperature of 320~380℃, hydrogen-to-oil volume ratio of 300~600, and volume hourly space velocity of 0.5~1.5 h⁻¹. -1 .

8. The method according to claim 1, characterized in that, In step (2), the effluent from the hydrogenation reactor exchanges heat with the diesel feedstock through a heat exchanger, and the effluent from the hydrogenation reactor after heat exchange is cooled to 100~300℃.

9. The method according to claim 8, characterized in that, In step (2), the material flowing out of the hydrogenation reactor after heat exchange is cooled to 150~250℃.

10. The method according to claim 1, characterized in that, In step (2), the gaseous components obtained by the high-pressure separator directly enter the circulating hydrogen desulfurization system and / or enter from the bottom of the adsorption dearomatic reactor to carry the desorbent mixture remaining in the aromatic adsorbent out of the adsorption dearomatic reactor and cool it through condenser II to separate the desorbent and gaseous stream. The separated desorbent is reused and the separated gaseous stream enters the circulating hydrogen desulfurization system.

11. The method according to claim 1, characterized in that, In step (2), after the liquid phase component is stripped by the stripping tower, the resulting liquid phase stream first passes through condenser I and then enters the adsorption dearomatization reactor from top to bottom.

12. The method according to claim 1, characterized in that, The reaction conditions of the adsorption-dearomatization reactor include: pressure of 0.1~0.5MPa and temperature of 20~80℃.

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