Process method for selective deep desulfurization and denitrification of aromatic-rich fraction

Abstract

The invention discloses a process method for selective deep desulfurization and denitrification of aromatic-rich fractions. The process method comprises the following steps: (1) mixing aromatic-rich diesel oil with hydrogen, and then feeding the mixture into a pre-hydrogenation reaction zone I for pre-hydrogenation dealkene reaction; (2) a product obtained in the step (1) enters a hydrofining reaction zone II for a hydrofining desulfurization and denitrification reaction; (3) carrying out flash evaporation on the product obtained in the step (2) to separate recycle hydrogen, enabling the obtained refined diesel oil to enter a moving bed adsorption denitrification reaction zone III, and carrying out deep adsorption denitrification reaction on the refined diesel oil under the action of an adsorption denitrification agent to obtain a desulfurized and denitrified refined aromatic-rich diesel oil component; and (4) enabling the inactivated adsorption denitrification agent in the step (3) to enter an adsorbent regeneration area IV, and completing reduction and drying of the inactivated adsorption denitrification agent under the action of a desorption agent to obtain the cyclically regenerated adsorption denitrification agent. According to the process method, deep removal of the sulfur-containing nitrogen-containing compound can be realized, and the investment cost is also greatly reduced.

Description

Technical Field

[0001] This invention relates to a selective hydrogenation refining process for aromatic fractions, specifically a process for deep desulfurization and denitrification of aromatic-rich fractions. Background Technology

[0002] In recent years, my country's economic structure has been constantly changing, and Chinese oil refining enterprises are shifting from a stage of high-speed development to a stage of high-quality development. Currently, integrated refining and chemical production, as well as cleaner, lower-carbon, and more intelligent production processes, have become the main characteristics of high-quality development in the oil refining industry. However, oil products contain high levels of sulfur-containing compounds such as thiophene (TH), benzothiophene, and dibenzothiophene (DBT), and nitrogen-containing compounds such as quinoline, pyridine, and pyrrole, which can be converted into SO₂ during combustion. X and NO X This leads to environmental problems such as acid rain and smog. Simultaneously, these sulfur and nitrogen compounds degrade oil quality and affect reaction processes. For example, sulfur and nitrogen impurities in naphthalene-rich fractions such as catalytic diesel are poisons to catalysts in subsequent alkylation reactions; therefore, feedstocks must undergo refining pretreatment before use in subsequent reactions. Nitrogen compounds in naphthalene-rich feedstocks strongly inhibit desulfurization reactions. During deep desulfurization and denitrification, naphthalene aromatics also undergo side reactions such as partial hydrogenation saturation and ring-opening. Therefore, developing highly active and selective hydrorefining processes is crucial to both increasing the depth of nitrogen impurity removal during feedstock hydrorefining and ensuring the yield of naphthalene aromatics during the hydrorefining process.

[0003] Currently, most research teams focus on catalyst preparation for the hydrodesulfurization and denitrogenation of aromatic diesel fuel.

[0004] Patent CN108236965A discloses a modified hydrodesulfurization catalyst and its preparation method. It employs a nanocrystal self-assembly method and an impregnation method to prepare a citric acid and magnesium-modified L / Al₂O₃ composite support. Then, a solution of molybdenum and cobalt salts is used for ultrasonic dispersion to obtain the hydrodesulfurization catalyst. This technology only focuses on hydrodesulfurization catalysts for diesel fuel; it does not explore the process and does not examine the hydrotreating performance of actual oil products.

[0005] Patent CN116590047A discloses a process system and production method for preparing refined diesel oil. Based on the different properties of the feedstock oils, it focuses on optimizing the feedstock space velocity, reducing the space velocity of inferior feedstocks and increasing the space velocity of high-quality feedstocks to improve the quality of refined diesel oil. Based on the different purity of hydrogen, it focuses on optimizing the hydrogen partial pressure and reducing the pressure drop of the unit, thereby improving the quality of refined diesel oil while reducing the unit's energy consumption. However, this process method cannot reduce the sulfur and nitrogen content in the diesel oil to below 5 μg / g, which is insufficient for subsequent naphthalene purification processes.

[0006] Patent CN116240045B discloses a process for deep hydroconversion of high-aromatic catalytic cracking diesel, relating to the field of hydrocarbon hydroconversion processes. This process is the first to utilize deep hydroconversion to convert high-aromatic catalytic cracking diesel, yielding jet fuel or serving as a good substitute for coal-based general-purpose diesel for ground equipment. However, this process only systematically removes sulfur from the diesel, without further exploring nitrogen content, and it does not consider aromatic saturation, making it unsuitable for processing naphthalene fractions.

[0007] In summary, current research on desulfurization and denitrogenation processes for rich aromatic diesel oils is very limited. Furthermore, the currently published hydrodesulfurization and denitrogenation catalysts and hydrorefining processes are unlikely to reduce the sulfur and nitrogen content of rich aromatic diesel oil to below 5 μg / g, which has a significant impact on subsequent processes.

[0008] Therefore, developing a novel preparation process for the desulfurization and denitrogenation of aromatic oils, laying a solid foundation for the subsequent production of naphthalene products, has become a current research hotspot. Summary of the Invention

[0009] The technical problem to be solved by this invention is to enable aromatic distillate oils to have lower sulfur and nitrogen content, with both sulfur and nitrogen content below 5 μg / g, so that they can be used for the production of subsequent naphthalene products.

[0010] To address the problems existing in the prior art, the present invention aims to provide a process for deep desulfurization and denitrification of aromatic diesel fuel. Based on a systematic understanding of the influence of operating conditions and catalyst performance on the deep hydrogenation of aromatic diesel fuel, three different reactors and an adsorption denitrifying agent reduction and regeneration unit are set up. This solves the problem of high sulfur and nitrogen content in aromatic diesel fuel and minimizes the hydrogenation saturation of polycyclic aromatic hydrocarbons. Furthermore, the process of the present invention employs a highly efficient moving bed deep adsorption denitrification process, achieving deep removal of sulfur and nitrogen-containing compounds. The process is continuous and allows for the regeneration of the adsorption denitrifying agent, significantly reducing investment costs.

[0011] To achieve the above objectives, the present invention provides a process for selective deep desulfurization and denitrification of aromatic-rich fractions, the process comprising the following steps:

[0012] (1) After mixing the aromatic diesel with hydrogen, it enters the pre-hydrogenation reaction zone I for pre-hydrogenation deolefination reaction;

[0013] (2) The product obtained in step (1) is fed into the hydrogenation refining reaction zone II for hydrogenation refining desulfurization and denitrification reaction;

[0014] (3) The product obtained in step (2) is flash-separated to remove circulating hydrogen. The refined diesel oil obtained is then fed into the moving bed adsorption denitrification reaction zone III. The adsorption denitrification reaction zone III is equipped with an adsorption denitrification agent. The refined diesel oil undergoes a deep adsorption denitrification reaction under the action of the adsorption denitrification agent to obtain the refined aromatic diesel oil component after desulfurization and denitrification.

[0015] (4) The deactivated adsorbent obtained in step (3) is introduced into the adsorbent regeneration zone IV. The adsorbent regeneration zone IV is equipped with a desorbent. The deactivated adsorbent is reduced and dried under the action of the desorbent to obtain a recycled adsorbent, thereby realizing the continuous regeneration of the adsorbent.

[0016] Further, in step (1), the conditions for the pre-hydrogenation deolefin reaction are: hydrogen partial pressure 0.2–4 MPa, reaction temperature 50–400 °C, and hydrogen-to-oil volume ratio 100–500 Nm³. 3 / m 3 Liquid hourly space velocity (LHSV) is 0.3–3.0 h⁻¹. -1 Preferably, the hydrogen partial pressure is 0.5–2 MPa, the reaction temperature is 120–360 °C, and the hydrogen-to-oil volume ratio is 150–400 Nm³. 3 / m 3 Liquid hourly space velocity (LHSV) is 0.5–2.0 h⁻¹. -1 .

[0017] Further, in step (2), the conditions for the hydrorefining desulfurization and denitrification reaction are: hydrogen partial pressure 0.2–4 MPa, reaction temperature 280–400 °C, and hydrogen-to-oil volume ratio 100–500 Nm³. 3 / m 3 Liquid hourly space velocity (LHSV) is 0.3–3.0 h⁻¹. -1 Preferably, the hydrogen partial pressure is 0.5–2 MPa, the reaction temperature is 320–360 °C, and the hydrogen-to-oil volume ratio is 150–400 Nm³. 3 / m 3 Liquid hourly space velocity (LHSV) is 0.5–2.0 h⁻¹. -1 .

[0018] Further, in step (1), a catalyst is added to the pre-hydrogenation deolefination reaction, the catalyst comprising a support and an active metal supported thereon;

[0019] The carrier is an inorganic refractory oxide; the inorganic refractory oxide is selected from at least one of alumina, amorphous aluminum silicate, silicon dioxide, and titanium dioxide;

[0020] The active metal is selected from Group VIB metal components and / or Group VIII metal components.

[0021] Furthermore, the group VIB metals include tungsten and / or molybdenum, and the content of the group VIB metals as oxides is 10% to 30% by weight, preferably 15% to 25%.

[0022] Further, the Group VIII metals include nickel and / or cobalt, and the content of the Group VIII metals as oxides is 1% to 8% by weight, preferably 1.5% to 6%.

[0023] Furthermore, in step (2), the hydrorefining catalyst used in the hydrorefining desulfurization and denitrogenation reaction is the same as or different from the catalyst used in the pre-hydrogenation deolefin reaction in step (1), preferably the same catalyst.

[0024] Furthermore, in step (3), the conditions for the deep adsorption denitrification reaction are: pressure 0–1 MPa, temperature 30–90 °C, and liquid hourly space velocity 0.1–0.5 h⁻¹. -1 .

[0025] Further, in step (3), the adsorption denitrification agent includes powder, binder, and acid solution; wherein, the raw material components of the powder, by weight, include: 10-30 parts by weight of silicon dioxide, 20-50 parts by weight of aluminum oxide, and 20-60 parts by weight of zinc oxide, preferably including: 15-25 parts by weight of silicon dioxide, 25-45 parts by weight of aluminum oxide, and 25-55 parts by weight of zinc oxide; the raw material components of the binder, by weight, include: 10-90 parts by weight of silica sol and 10-90 parts by weight of aluminum sol for bonding, preferably including: 20-80 parts by weight of silica sol and 20-80 parts by weight of aluminum sol for bonding; the acid solution is at least one of sulfuric acid, nitric acid, and phosphoric acid, with an acid loading of 2-8%, preferably, the acid solution is a sulfuric acid solution.

[0026] Further, in step (4), the desorbent is an alcohol solution, which is selected from at least one of methanol solution and ethanol solution; the desorption conditions for the inactivated adsorbent to complete reduction in the elution solution are: pressure 0-1 MPa, temperature 30-90℃, and liquid hourly space velocity 0.1-2 h⁻¹. -1 Preferably, the desorption conditions are: pressure 0–0.5 MPa, temperature 30–60 °C, and liquid hourly space velocity 0.5–1.5 h⁻¹. -1 .

[0027] Furthermore, in step (4), the drying gas in the drying process is nitrogen or air, and the drying conditions are: a volume hourly space velocity (VHSV) of 500–5000 h⁻¹. -1 Temperature 100~200℃, pressure 0~1MPa.

[0028] Furthermore, the recycled adsorption denitrifying agent obtained in step (4) is used as the adsorption denitrifying agent for the deep adsorption denitrification reaction in adsorption denitrification reaction zone III in step (3), wherein the single cycle service life of the adsorption denitrifying agent is not less than 15 days.

[0029] The present invention has at least the following beneficial effects:

[0030] (1) The process method of the present invention adopts a process of selective hydrodesulfurization and denitrification coupled with deep adsorption denitrification. Under the condition of avoiding excessive hydrogenation saturation of aromatics, the nitrogen content in the product can be further reduced by adsorption. This can achieve deep removal of sulfur and nitrogen compounds in oil products, while maximizing the avoidance of hydrogenation saturation of polycyclic aromatics, which is conducive to subsequent high value-added utilization.

[0031] (2) Conventional hydrorefining processes are extremely difficult to remove residual nitrogen compounds. If further hydrorefining is used, it will inevitably lead to a large saturation loss of aromatics, resulting in poor economic efficiency. However, the coupled process method proposed in this invention can further remove nitrogen compounds from the product without losing aromatics, thereby meeting the standards for secondary utilization of the product.

[0032] (3) The process method of the present invention adopts a highly efficient moving bed deep adsorption denitrification process and is equipped with a high nitrogen capacity adsorption denitrification agent to achieve deep removal of sulfur and nitrogen compounds. At the same time, it has the advantages of continuous process, mild conditions, long operating cycle and low operating cost, which greatly reduces investment cost.

[0033] (4) The adsorption denitrification agent used in this invention includes powder, binder, and acid solution. The raw material components of the powder include silica, alumina, and zinc oxide. Adding zinc oxide can increase the specific surface area of ​​the adsorption denitrification agent, enhance its adsorption function, and improve the adsorption denitrification effect. Silica surface contains a large number of hydroxyl groups. Adding acid solution can cause the hydroxyl groups to react with the acid solution, introducing acid radicals to form new functional groups, providing more adsorption sites, enhancing silica's adsorption capacity for nitrogen compounds, thereby improving the adsorption denitrification efficiency. The adsorption effect is significantly improved compared to before acid modification. Secondly, the introduction of acid radicals changes the charge distribution and polarity of the silica surface, making it more conducive to adsorbing nitrogen compounds with opposite charges. Adding acid solution can also enhance the stability and durability of the adsorption denitrification agent, making it less susceptible to removal by water. Furthermore, the modified adsorption denitrification agent can be desorbed and regenerated using alcohols, exhibiting good periodicity. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a process flow diagram of the selective deep desulfurization and denitrification of aromatic fractions according to the present invention.

[0036] In the attached figures, the following labels are used:

[0037] A-Flash evaporation unit; B-Adsorption denitrifying agent regeneration dryer; C-Adsorption denitrifying agent reduction regeneration unit;

[0038] 1-Aromatic diesel fuel and hydrogen mixture; 2-Producted oil; 3-Producted oil; 4-Recycled hydrogen; 5-Deactivated adsorbent and denitrifying agent; 6-Recycled adsorbent and denitrifying agent; 7-Refined aromatic diesel fuel;

[0039] I - Pre-hydrogenation reaction zone; II - Hydrogenation purification reaction zone; III - Adsorption denitrification reaction zone; IV - Adsorbent regeneration zone. Detailed Implementation

[0040] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the present invention.

[0041] The selective deep desulfurization and denitrification process for aromatic fractions of the present invention includes the following steps:

[0042] (1) After mixing the aromatic diesel with hydrogen, it enters the pre-hydrogenation reaction zone I for pre-hydrogenation deolefination reaction;

[0043] (2) The product obtained in step (1) is fed into the hydrogenation refining reaction zone II for hydrogenation refining desulfurization and denitrification reaction;

[0044] (3) The product obtained in step (2) is flash-separated to remove circulating hydrogen. The refined diesel oil obtained is then fed into the moving bed adsorption denitrification reaction zone III. The adsorption denitrification reaction zone III is equipped with an adsorption denitrification agent. The refined diesel oil undergoes a deep adsorption denitrification reaction under the action of the adsorption denitrification agent to obtain the refined aromatic diesel oil component after desulfurization and denitrification.

[0045] (4) The deactivated adsorbent obtained in step (3) is introduced into the adsorbent regeneration zone IV. The adsorbent regeneration zone IV is equipped with a desorbent. The deactivated adsorbent is reduced and dried under the action of the desorbent to obtain a recycled adsorbent, thereby realizing the continuous regeneration of the adsorbent.

[0046] Evaluation method:

[0047] Sulfur / Nitrogen Content: The sulfur / nitrogen content was measured using a Multi EAS / N analyzer from Anakitikjena, Germany. To ensure the accuracy of the measurement results, each sample was measured three times and the average value was taken. Appropriate sulfur / nitrogen standards were selected to correct the sulfur / nitrogen content. The measurement range was 0.2–1000 μg / g, and the measurement accuracy was ≥0.2 μg / g.

[0048] Aromatic saturation: The diesel fuel composition of the hydrogenation products was determined using a GC-MS analyzer. The total aromatic conversion rate was calculated using the following formula:

[0049] Total aromatics conversion rate C a (%)

[0050]

[0051] In the formula, a o —Total aromatic hydrocarbon content of raw materials, %; a—Total aromatic hydrocarbon content of products, %.

[0052] Examples 1-5:

[0053] The reaction conditions for Examples 1-5 are shown in Table 1.

[0054] Table 1 Reaction conditions of Examples 1-5

[0055]

[0056]

[0057] The catalysts or desorbents used in each reaction zone and regeneration zone of Examples 1-5 are shown in Table 2.

[0058] Table 2 Catalysts or Desorbents Used in Examples 1-5

[0059]

[0060]

[0061]

[0062] Comparative Example 1:

[0063] The difference from Example 3 is that the adsorption denitrification agent used in the adsorption denitrification reaction zone III contains only alumina and silicon dioxide, wherein the content of alumina is 50 parts by weight and the content of silicon dioxide is 50 parts by weight.

[0064] Comparative Example 2:

[0065] The difference from Example 3 is that the adsorption denitrification reaction zone III and the adsorbent regeneration zone IV were removed, and a hydrogenation purification zone with the same reaction conditions as the hydrogenation purification reaction zone II was added after the hydrogenation purification reaction zone II.

[0066] The performance analysis of the hydrorefined product oils obtained in Examples 1-5 and Comparative Examples 1-2 is shown in Table 3.

[0067] Table 3. Analytical results of hydrorefined oil products from Examples 1-5 and Comparative Examples 1-2

[0068]

[0069]

[0070] As can be seen from the results in Table 3, (1) the process method of the present invention adopts a process of selective hydrodesulfurization and denitrification coupled with deep adsorption denitrification, which can achieve deep removal of sulfur and nitrogen compounds in oil products, and at the same time can maximize the avoidance of hydrogenation saturation of polycyclic aromatic hydrocarbons, which is conducive to subsequent high value-added utilization; (2) the process method of the present invention adopts a high-efficiency moving bed deep adsorption denitrification process and is equipped with a high nitrogen capacity adsorption denitrification agent to achieve deep removal of sulfur and nitrogen compounds. At the same time, it has the advantages of continuous process, mild conditions, long operating cycle and low operating cost, which greatly reduces investment costs.

[0071] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A process for selective deep desulfurization and denitrification of aromatic-rich fractions, characterized in that, Includes the following steps: (1) After mixing the aromatic diesel with hydrogen, it enters the pre-hydrogenation reaction zone I for pre-hydrogenation deolefination reaction; (2) The product obtained in step (1) is fed into the hydrogenation refining reaction zone II for hydrogenation refining desulfurization and denitrification reaction; (3) The product obtained in step (2) is flash-separated to remove circulating hydrogen. The refined diesel oil obtained is then fed into the moving bed adsorption denitrification reaction zone III. The adsorption denitrification reaction zone III is equipped with an adsorption denitrification agent. The refined diesel oil undergoes a deep adsorption denitrification reaction under the action of the adsorption denitrification agent to obtain the refined aromatic diesel oil component after desulfurization and denitrification. (4) The deactivated adsorbent obtained in step (3) is introduced into the adsorbent regeneration zone IV. The adsorbent regeneration zone IV is equipped with a desorbent. The deactivated adsorbent is reduced and dried under the action of the desorbent to obtain a recycled adsorbent, thereby realizing the continuous regeneration of the adsorbent.

2. The process method according to claim 1, characterized in that, In step (1), the conditions for the pre-hydrogenation deolefin reaction are: hydrogen partial pressure 0.2–4 MPa, reaction temperature 50–400 °C, and hydrogen-to-oil volume ratio 100–500 Nm³. 3 / m 3 Liquid hourly space velocity (LHSV) is 0.3–3.0 h⁻¹. -1 .

3. The process method according to claim 1, characterized in that, In step (2), the conditions for the hydrorefining desulfurization and denitrification reaction are: hydrogen partial pressure 0.2–4 MPa, reaction temperature 280–400 °C, and hydrogen-to-oil volume ratio 100–500 Nm³. 3 / m 3 Liquid hourly space velocity (LHSV) is 0.3–3.0 h⁻¹. -1 .

4. The process method according to claim 1, characterized in that, In step (1), a catalyst is added to the pre-hydrogenation deolefin reaction, the catalyst comprising a support and an active metal supported thereon; The carrier is an inorganic refractory oxide; the inorganic refractory oxide is selected from at least one of alumina, amorphous aluminum silicate, silicon dioxide, and titanium dioxide; The active metal is selected from Group VIB metal components and / or Group VIII metal components.

5. The process method according to claim 1, characterized in that, The group VIB metals include tungsten and / or molybdenum, and the content of the group VIB metals as oxides is 10% to 30% by weight. The Group VIII metals include nickel and / or cobalt, and the content of the Group VIII metals as oxides is 1% to 8% by weight.

6. The process method according to claim 1, characterized in that, In step (2), the hydrorefining catalyst used in the hydrorefining desulfurization and denitrogenation reaction may be the same as or different from the catalyst used in the pre-hydrogenation deolefin reaction in step (1).

7. The process method according to claim 1, characterized in that, In step (3), the conditions for the deep adsorption denitrification reaction are: pressure 0–1 MPa, temperature 30–90 °C, and liquid hourly space velocity 0.1–0.5 h⁻¹. -1 .

8. The process method according to claim 1, characterized in that, In step (3), the adsorption denitrification agent comprises powder, binder, and acid solution; wherein, the raw material components of the powder, by weight, include: 10-30 parts by weight of silicon dioxide, 20-50 parts by weight of aluminum oxide, and 20-60 parts by weight of zinc oxide; the raw material components of the binder, by weight, include: 10-90 parts by weight of silica sol and 10-90 parts by weight of aluminum sol for bonding; the acid solution is at least one of sulfuric acid, nitric acid, and phosphoric acid, with an acid loading of 2-8%.

9. The process method according to claim 1, characterized in that, In step (4), the desorbent is an alcohol solution, which is selected from at least one of methanol solution and ethanol solution; the conditions for the deactivated adsorbent to be reduced in the elution solution are: pressure 0-1 MPa, temperature 30-90℃, and liquid hourly space velocity 0.1-2 h⁻¹. -1 ; In step (4), the drying gas in the drying process is nitrogen or air, and the drying conditions are: volume hourly space velocity (VHSV) of 500–5000 h⁻¹. -1 Temperature 100~200℃, pressure 0~1MPa.

10. The process method according to claim 1, characterized in that, The recycled adsorption denitrifying agent obtained in step (4) is used as the adsorption denitrifying agent for the deep adsorption denitrification reaction in adsorption denitrification reaction zone III in step (3), wherein the single cycle service life of the adsorption denitrifying agent is not less than 15 days.

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