Method and device for producing ultra-low-aromatic special oil by low-medium pressure hydrogenation

Abstract

The application discloses a kind of middle-low pressure hydrogenation production ultra-low aromatic special oil product method and device, belong to petroleum chemical energy technical field.The application uses two-stage four-region catalyst grading hydrogenation process: raw material is first passed through the preprocessor equipped with adsorbent and is treated to remove water and oxygen, then is gasified after heating furnace, in turn into first reactor (hydrofining section) and second reactor (hydrodearomatization section);First reactor is composed of A region and B region, and second reactor is composed of C region and D region.Deep de-aromatic is realized by two-stage hydrogenation and catalyst grading.Hydrogenation product is first subjected to gas-liquid separation in stripping column, and then is cut in rectifying column to obtain high-quality hydrogenated oil products of different fractions.The device has the characteristics of strong raw material adaptability, can realize continuous regeneration production, and significantly improves efficiency.It can also efficiently hydrogenate and upgrade various raw materials, and has broad application prospect.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical energy technology, specifically relating to a technology for producing ultra-low aromatic specialty oils by low-pressure hydrogenation of petroleum products. Background Technology

[0002] Currently, the global refining industry faces the challenge of structural overcapacity, particularly in the gasoline and diesel markets. With the rapid development of new energy vehicles and the accelerated transformation of the energy structure, the growth in demand for traditional gasoline and diesel has slowed, while the demand for chemical raw materials and high-end specialty oil products continues to rise. Against this backdrop, "reducing oil production and increasing chemical production" has become a key strategic direction for refining enterprises to optimize their product structure and enhance their competitiveness. Adjusting production facilities and processes to reduce the proportion of gasoline and diesel output and increase the production of high-value-added chemical products and specialty oil products has become the main path for the industry's transformation and upgrading.

[0003] Ultra-low aromatic specialty oils are widely used in high-end electronic cleaning, precision instrument manufacturing, pharmaceutical preparations, and environmentally friendly coatings. Due to their high purity, low toxicity, and controllable volatility, market demand continues to grow, making them one of the important high-profit products in the process of "reducing oil and increasing chemicals" for refining and chemical enterprises. However, the current production of ultra-low aromatic specialty oils mainly relies on high-temperature and high-pressure hydrogenation refining technology, which has significant bottlenecks: (1) The process conditions are harsh, and the reaction is usually carried out under hydrogen pressure exceeding 10 MPa, which places extremely high demands on equipment materials and safety; (2) The investment and operating costs are high, with large investments in equipment such as high-pressure reactors, circulating compressors, and high-pressure heat exchange systems, as well as high energy consumption and rapid catalyst loss; and the technology is highly dependent. These factors restrict the capacity expansion and price optimization of ultra-low aromatic specialty oils, making it difficult to fully meet market demand.

[0004] To reduce production costs and promote industry adoption, the development of low-pressure hydrogenation technology has become a current research hotspot. This technology aims to achieve efficient saturation and desulfurization, deoxygenation, and denitrification of aromatics at lower pressures (typically ≤8 MPa) through process optimization, thereby significantly reducing equipment investment and operating costs.

[0005] While the existing two-stage, two-agent hydrogenation process is widely used, its technical bottlenecks are also quite significant: Patent CN115785993A balances hydrogenation activity and cracking reaction through two-stage hydrogenation and catalyst bed structure control, but the reaction hydrogen pressure is as high as 20 MPa; Patent CN103059978A achieves high-activity desulfurization by regulating the pore structure and acidity of the catalyst, but still relies on a hydrogen pressure of 10 MPa; Patent CN102311794A designs a combined process of liquid-phase circulation and gas-phase hydrogenation to improve hydrogen utilization, but the process is complex and it is also difficult to get rid of high-pressure dependence.

[0006] In summary, existing processes not only have stringent requirements for the multifunctionality of catalysts, but are also subject to harsh high-pressure reaction conditions, resulting in high operating costs. Summary of the Invention

[0007] To address the issue of existing oil hydrotreating processes' stringent reliance on high-pressure conditions, this invention provides an innovative medium-to-low-pressure hydrotreating process for aromatics removal. This process, through the construction of a "two-stage, four-zone" catalyst gradation system, achieves deep desulfurization, denitrification, and deoxygenation of fuel oil under low-pressure and mild operating conditions, while also completing a high level of aromatics saturation, resulting in high-quality hydrogenated oil products.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A method for producing ultra-low aromatic specialty oils by medium- and low-pressure hydrogenation includes the following steps:

[0010] (1) Raw material pretreatment: The raw oil is passed into the preprocessor and contacted with the adsorbent at a preset temperature to remove impurities from the raw oil;

[0011] (2) Feed preparation: The raw oil processed in step (1) is heated to vaporization and mixed with the dried hydrogen to form a mixed feed;

[0012] (3) Two-stage four-zone hydrogenation reaction: The mixed feed is passed sequentially through a hydrogenation refining section and a hydrogenation dearomatization section arranged in series for reaction;

[0013] The hydrorefining section includes a catalytic A zone and a catalytic B zone connected in sequence. The catalytic A zone is filled with a hydrodesulfurization catalyst for desulfurization, and the catalytic B zone is filled with a hydrodeoxygenation and dechlorination catalyst for deoxygenation and dechlorination.

[0014] The hydrodearomatization section includes a catalytic C zone and a catalytic D zone connected in sequence, wherein the catalytic C zone and the catalytic D zone are filled with an aromatic hydrogenation catalyst for aromatic hydrogenation saturation.

[0015] (4) Product separation and distillation: The hydrogenation reaction product obtained in step (3) is subjected to gas-liquid separation to obtain liquid product, and the liquid product is fractionated to obtain ultra-low aromatic special oil products of different fractions.

[0016] Further, the adsorbent mentioned in step (1) is selected from one or more combinations of activated carbon, alumina, silica, molecular sieve, calcium oxide, zinc oxide, and iron oxide; the amount of adsorbent added is 20% to 80% of the total loading of the catalyst in the subsequent hydrorefining section (the sum of catalysts in zones A and B); the pretreatment temperature is 20 to 300°C.

[0017] More preferably, the adsorbent is a combination of activated carbon and zinc oxide, and the amount added is 50% to 80% of the total mass of catalyst (A+B), and the pretreatment temperature is 150 to 250°C.

[0018] Furthermore, in step (2), the temperature at which the raw oil is heated to vaporization is 200~400℃, preferably 300~400℃; the desiccant used for drying the hydrogen is selected from calcium oxide, silica gel balls, and molecular sieves, preferably calcium oxide.

[0019] Furthermore, the operating conditions of the hydrorefining section are as follows: reaction temperature of 200~400℃, hydrogen partial pressure of 3~8MPa, and hydrogen-to-oil volume ratio of 300~1000; the mass hourly space velocity of catalytic zone A and catalytic zone B are each independently 0.5~5 h⁻¹. -1 .

[0020] More preferably, the reaction temperature of the hydrorefining section is 300~400℃, the hydrogen partial pressure is 5~7 MPa, and the hydrogen-to-oil volume ratio is 500~900.

[0021] Furthermore, in the hydrorefining section, catalytic zone A is packed with one of Ni-Mo / Al2O3 or Ni-W / Al2O3 catalysts, with a mass hourly space velocity of 0.5~5 h⁻¹. -1 Preferably 0.5~2 h -1 The catalyst B region is loaded with one of the following catalysts: Ni-Co-Mo / Al2O3, Ni-Co-W / Al2O3, Co-Mo / Al2O3, and Co-W / Al2O3, with a mass space velocity of 0.5–5 h⁻¹. -1 Preferably 0.5~2 h -1 .

[0022] Furthermore, the operating conditions of the hydrodearomatization section are as follows: reaction temperature of 150~250℃, hydrogen partial pressure of 3~8MPa, and hydrogen-to-oil volume ratio of 300~1000; the mass hourly space velocity of the catalytic C zone and the catalytic D zone are each independently 0.5~5 h⁻¹. -1 .

[0023] More preferably, the reaction temperature of the hydrodearomatization section is 200~250℃, the hydrogen partial pressure is 5~7 MPa, and the hydrogen-to-oil volume ratio is 500~900.

[0024] Furthermore, in the hydrodearomatization section, catalytic region C and catalytic region D are each independently packed with one of Ni / Al2O3 or Pt / Al2O3 catalysts, with each having a mass hourly space velocity (WHSV) of 0.5–5 h⁻¹. -1 Preferably 0.5~2 h -1 .

[0025] An apparatus for implementing a medium- and low-pressure hydrogenation method to produce ultra-low aromatic specialty oils, the apparatus comprising, in sequence along the material flow direction: a feed pretreatment unit, a feed preparation unit, a two-stage four-zone hydrogenation reaction unit, and a product separation and distillation unit; the feed pretreatment unit includes a pre-processor for holding an adsorbent and purifying the feed oil; the feed preparation unit includes a heater for vaporizing the pretreated feed oil and a hydrogen dryer for drying hydrogen; the two-stage four-zone hydrogenation reaction unit includes a series-connected... The reactor comprises a first-stage reactor and a second-stage reactor. The first-stage reactor is a hydrorefining section, which is internally divided by a partition into sequentially connected catalytic zones A and B, each filled with a catalyst of corresponding function. The second-stage reactor is a hydrodearomatization section, which is internally divided by a partition into sequentially connected catalytic zones C and D, each filled with an aromatic hydrocarbon hydrogenation catalyst. The product separation and distillation unit includes a stripping column for gas-liquid separation of the hydrogenation reaction products and a distillation column for fractionation of the liquid products, connected in sequence.

[0026] Furthermore, in the hydrorefining section, the catalyst in catalytic region A is Ni-Mo / Al2O3 or Ni-W / Al2O3, and the catalyst in catalytic region B is Ni-Co-Mo / Al2O3, Ni-Co-W / Al2O3, Co-Mo / Al2O3, or Co-W / Al2O3;

[0027] The catalysts in the C and D regions of the hydrodearomatization section are independently Ni / Al2O3 or Pt / Al2O3.

[0028] Furthermore, the feedstock oil processed by the process or apparatus is selected from one of gasoline, diesel, kerosene, coal tar, coal liquefaction oil, raffinate oil, condensate oil, heavy benzene, and residual oil.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] This invention provides an innovative medium-low pressure hydrodearomatization process, which constructs a two-stage, four-zone catalyst gradation process. Under low-pressure and mild process conditions, it achieves a significant improvement in comprehensive performance: (1) Deep purification: Under low pressure, it achieves high performance indicators such as removal rate of impurities ≥90% and dearomatization rate ≥95%; (2) Economical and efficient: The catalyst cost is low, and the catalytic activity is optimized through the synergistic effect of zone gradation; (3) Stable and easy to implement: The catalyst has a long lifespan, the process conditions are mild and environmentally friendly, and the difficulty and cost of industrial implementation are greatly reduced. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart illustrating the application process;

[0033] Figure 2 This is a color comparison chart of the example and the comparative product. Detailed Implementation

[0034] To gain a deeper understanding of this invention, we will provide a comprehensive and detailed description. However, this invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a full understanding of the disclosure of this invention.

[0035] This invention provides a process for producing ultra-low aromatic specialty oils through low-pressure hydrotreating of petroleum products. The process flow is as follows: First, the feedstock oil enters a pre-processor where impurities are removed by an adsorbent (feedstock pretreatment unit). Then, the treated feedstock oil is heated and vaporized in a heater, and mixed with dried hydrogen gas (feed preparation unit). Next, the mixed feedstock sequentially passes through a two-stage, four-zone hydrotreating reaction unit loaded with different functional catalysts. The two stages consist of a first-stage reactor (hydrorefining stage) and a second-stage reactor (hydrodearomatization stage). The first-stage reactor comprises zones A and B, and the second-stage reactor comprises zones C and D (two-stage, four-zone hydrotreating reaction unit). Finally, the product enters the product separation and distillation unit: the obtained product is sent to a stripping tower for gas-liquid separation, and the separated liquid product is further distilled to obtain hydrotreated oils (ultra-low aromatic specialty oils) of different fractions.

[0036] The specific operating conditions for each unit are limited as follows:

[0037] (1) Raw material pretreatment unit

[0038] The feedstock first enters the pre-processor to remove trace impurities that affect catalyst life and oil quality.

[0039] Adsorbent: selected from one or more combinations of activated carbon, alumina, silicon dioxide, molecular sieve, calcium oxide, zinc oxide, and iron oxide; preferably a combination of activated carbon and zinc oxide.

[0040] Operating parameters: The amount of adsorbent added is 20% to 80% (preferably 50% to 80%) of the total amount of catalyst (A+B) in the subsequent hydrorefining stage; the pretreatment temperature is 20 to 300°C (more preferably 150°C to 250°C).

[0041] (2) Feeding preparation unit

[0042] The pretreated feedstock oil is vaporized in a heating furnace and mixed with dry hydrogen.

[0043] Heating furnace: The outlet temperature is controlled at 200~400℃ (preferably 300~400℃).

[0044] Hydrogen drying: The desiccant is selected from calcium oxide, silica gel balls and molecular sieve (preferably calcium oxide).

[0045] (3) Two-stage four-zone hydrogenation reaction unit

[0046] The mixed feed passes sequentially through a hydrorefining section and an aromatics hydrogenation section connected in series. Each section is filled with complementary catalysts to achieve deep purification of the oil and saturation of aromatics under low-pressure conditions.

[0047] The first stage is the hydrorefining stage, which consists of catalytic A and B zones and mainly removes heteroatoms such as sulfur, nitrogen, oxygen, and chlorine.

[0048] Catalytic A zone: loaded with hydrodesulfurization catalyst, with a mass hourly space velocity (WHSV) of 0.5–5 h⁻¹. -1 More preferably, one of Ni-Mo / Al2O3 or Ni-W / Al2O3 catalysts is used, with a space velocity of 0.5~2 h⁻¹. -1 ;

[0049] Catalytic B zone: loaded with hydrodeoxygenation and dechlorination catalyst, with a mass hourly space velocity (WHSV) of 0.5–5 h⁻¹. -1 More preferably, one of the catalysts Ni-Co-Mo / Al2O3, Ni-Co-W / Al2O3, Co-Mo / Al2O3, and Co-W / Al2O3 is used, with a space velocity of 0.5~2 h⁻¹. -1 .

[0050] Common operating conditions: reaction temperature of 200~400℃ (preferably 300~400℃), hydrogen pressure of 3~8 MPa (preferably 5~7 MPa), and hydrogen-to-oil volume ratio of 300~1000 (preferably 500~900).

[0051] The second stage: the hydrodearomatization stage, which consists of the C and D regions of the catalyst, is specifically designed for the deep selective hydrogenation saturation of aromatics.

[0052] Catalyst C section: packed with nickel-based or platinum-based aromatic hydrogenation catalyst, with a mass hourly space velocity (WHSV) of 0.5–5 h⁻¹. -1 More preferably, one of Ni / Al2O3 or Pt / Al2O3 catalysts is used, with a space velocity of 0.5~2 h⁻¹. -1 .

[0053] Catalyst D section: packed with nickel-based or platinum-based aromatic hydrogenation catalyst, with a mass hourly space velocity (WHSV) of 0.5–5 h⁻¹. -1 More preferably, one of Ni / Al2O3 or Pt / Al2O3 catalysts is used, with a space velocity of 0.5~2 h⁻¹. -1 .

[0054] Common operating conditions: reaction temperature is 150~250℃ (preferably 200~250℃), hydrogen pressure is 3~8 MPa (preferably 5~7 MPa), and hydrogen-to-oil volume ratio is 300~1000 (preferably 500~900).

[0055] (4) Product separation and distillation unit

[0056] The hydrogenation reaction products are separated into hydrogen-rich gas and liquid products by a stripping tower. The liquid products are then cut by a distillation tower to obtain the target products of different fractions (such as ultra-low aromatic specialty oils).

[0057] (5) Raw material adaptability

[0058] The process of this invention has wide adaptability to raw materials. The raw material oil is selected from gasoline, diesel, kerosene, coal tar, coal liquefaction oil, residue oil, condensate oil, heavy benzene, residual oil, and other oil products.

[0059] The analytical methods for the products obtained in each embodiment and comparative example are as follows: sulfur and nitrogen content were determined by Jiangsu Jiangfen JF-TSN-5000Plus sulfur and nitrogen analyzer according to relevant standards; chlorine content was determined by Jiangsu Jiangfen JF-WK-2000A coulometric analyzer according to relevant standards; aromatic hydrocarbon content was tested and calculated using a TU-1901 ultraviolet spectrophotometer according to the petrochemical industry standard NB / SH / T0913-2015.

[0060] Example 1

[0061] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0062] 1 g of activated carbon was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 200℃. The outlet temperature of the raw material heater was set to 300℃. Silica gel balls were packed into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g of Ni-Mo / Al2O3 was loaded into catalytic zone A, and 1 g of Ni-Co-Mo / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 3 h⁻¹. -1 The reaction temperature was 300℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 800. The hydrodearomatization section consisted of catalytic zone C packed with 1 g Ni / Al₂O₃ and catalytic zone D packed with 1 g Ni / Al₂O₃; the mass hourly space velocity (H₂S₀) for this section was 3 h⁻¹. -1The reaction temperature was 200℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 800.

[0063] Process Operation and Product Analysis: Diesel fuel is fed into a pre-processor, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0064] Example 2

[0065] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0066] 1 g of silica was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 150℃. The outlet temperature of the raw material heater was set to 200℃. Molecular sieves were loaded into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g of Ni-W / Al2O3 was loaded into catalytic zone A, and 1 g of Ni-Co-Mo / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 0.5 h⁻¹. -1 The reaction temperature was 400℃, the hydrogen partial pressure was 3 MPa, and the hydrogen-to-oil volume ratio was 400. The hydrodearomatization section consisted of a catalyst zone C packed with 1 g Pt / Al₂O₃ and a catalyst zone D packed with 1 g Ni / Al₂O₃; the mass hourly space velocity (H₂S₀) for this section was 0.5 h⁻¹. -1 The reaction temperature was 200℃, the hydrogen partial pressure was 3 MPa, and the hydrogen-to-oil volume ratio was 400.

[0067] Process Operation and Product Analysis: Kerosene is pre-treated, then gasified in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower, and the liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0068] Example 3

[0069] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0070] A mixture of 1 g activated carbon and silica was packed as an adsorbent in the pre-processor, and the pre-treatment temperature was set to 20°C. The outlet temperature of the raw material heater was set to 200°C. Calcium oxide was packed as a desiccant in the hydrogen dryer. Hydrogen refining section: 1 g Ni-Mo / Al2O3 was packed in catalytic zone A, and 1 g Ni-Co-W / Al2O3 was packed in catalytic zone B; the mass hourly space velocity (HHSV) for this section was 5 h⁻¹.-1 The reaction temperature was 200℃, the hydrogen partial pressure was 8 MPa, and the hydrogen-to-oil volume ratio was 800. The hydrodearomatization section consisted of 1 g Pt / Al₂O₃ packed in catalyst zone C and 1 g Pt / Al₂O₃ in catalyst zone D; the mass hourly space velocity (H₂S₀) for this section was 5 h⁻¹. -1 The reaction temperature was 250℃, the hydrogen partial pressure was 8MPa, and the hydrogen-to-oil volume ratio was 800.

[0071] Process Operation and Product Analysis: Condensate oil is pre-treated, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower, and the liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0072] Example 4

[0073] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0074] A mixture of 0.4 g alumina and 0.6 g activated carbon was used as the adsorbent in the pre-processor, and the pre-treatment temperature was set to 300℃. The outlet temperature of the raw material heater was set to 400℃. Silica gel balls were used as the desiccant in the hydrogen dryer. Hydrogen refining section: 2.5 g Ni-Mo / Al2O3 was packed in catalytic zone A, and 2.5 g Co-Mo / Al2O3 was packed in catalytic zone B; the mass hourly space velocity (HHSV) for this section was 0.5 h⁻¹. -1 The reaction temperature was 300℃, the hydrogen partial pressure was 4 MPa, and the hydrogen-to-oil volume ratio was 1000. The hydrodearomatization section consisted of a catalyst zone C packed with 1 g Ni / Al₂O₃ and a catalyst zone D packed with 1 g Pt / Al₂O₃; the mass hourly space velocity (H₂S₀) for this section was 1 h⁻¹. -1 The reaction temperature was 150℃, the hydrogen partial pressure was 4 MPa, and the hydrogen-to-oil volume ratio was 1000.

[0075] Process Operation and Product Analysis: Heavy benzene is pre-treated, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0076] Example 5

[0077] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0078] 1 g of calcium oxide was loaded into the pre-processor as an adsorbent, and the pre-processing temperature was set to 100℃. The outlet temperature of the raw material heater was set to 200℃. Silica gel balls were packed into the hydrogen dryer as a desiccant. Hydrogen refining section: 0.625 g of Ni-W / Al2O3 was loaded into catalytic zone A, and 0.625 g of Ni-Co-W / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 2 h⁻¹. -1 The reaction temperature was 250℃, the hydrogen partial pressure was 6 MPa, and the hydrogen-to-oil volume ratio was 300. In the hydrodearomatization section: catalytic zone C was packed with 0.5 g Pt / Al₂O₃, and catalytic zone D was packed with 1.5 g Ni / Al₂O₃; the mass hourly space velocity (H₂S₀) in zone C of this section was 4 h⁻¹. -1 The mass hourly space velocity (MHSV) in region D is 1.33 h⁻¹. -1 The reaction temperature was 180℃, the hydrogen partial pressure was 6 MPa, and the hydrogen-to-oil volume ratio was 300.

[0079] Process Operation and Product Analysis: Coal tar is pre-treated and then gasified in a heater. It is then mixed with dried hydrogen to form a mixed feed. This mixed feed is sequentially processed through a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0080] Example 6

[0081] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0082] 1 g of zinc oxide was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 50℃. The outlet temperature of the raw material heater was set to 400℃. Molecular sieves were loaded into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g of Ni-Mo / Al2O3 was loaded into catalytic zone A, and 1 g of Co-W / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 3 h⁻¹. -1 The reaction temperature was 350℃, the hydrogen partial pressure was 3 MPa, and the hydrogen-to-oil volume ratio was 500. The hydrodearomatization section consisted of a catalyst C zone packed with 1 g Ni / Al₂O₃ and a catalyst D zone packed with 1 g Pt / Al₂O₃; the mass hourly space velocity (H₂S₀) for this section was 3 h⁻¹. -1 The reaction temperature was 150℃, the hydrogen partial pressure was 3 MPa, and the hydrogen-to-oil volume ratio was 500.

[0083] Process Operation and Product Analysis: The raffinate oil is pre-treated, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0084] Example 7

[0085] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0086] 1 g of iron oxide was loaded into the pre-processor as an adsorbent, and the pre-processing temperature was set to 300℃. The outlet temperature of the raw material heater was set to 250℃. Molecular sieves were loaded into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g of Ni-W / Al2O3 was loaded into catalytic zone A, and 1 g of Co-Mo / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 2 h⁻¹. -1 The reaction temperature was 300℃, the hydrogen partial pressure was 7 MPa, and the hydrogen-to-oil volume ratio was 1000. The hydrodearomatization section consisted of 1 g Pt / Al₂O₃ packed in catalytic zone C and 1 g Ni / Al₂O₃ packed in catalytic zone D; the mass hourly space velocity (H₂S₀) for this section was 2 h⁻¹. -1 The reaction temperature was 200℃, the hydrogen partial pressure was 7 MPa, and the hydrogen-to-oil volume ratio was 1000.

[0087] Process Operation and Product Analysis: Coal liquefaction oil is pre-treated, then gasified in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0088] Example 8

[0089] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0090] A mixture of 0.5 g zinc oxide and 0.5 g iron oxide was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 80℃. The outlet temperature of the raw material heater was set to 350℃. Calcium oxide was loaded into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g Ni-Mo / Al2O3 was loaded into catalytic zone A, and 1 g Ni-Co-W / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 2 h⁻¹. -1The reaction temperature was 300℃, the hydrogen partial pressure was 7 MPa, and the hydrogen-to-oil volume ratio was 700. The hydrodearomatization section consisted of 1 g Pt / Al₂O₃ packed in catalyst zone C and 1 g Pt / Al₂O₃ in catalyst zone D; the mass hourly space velocity (H₂S₀) for this section was 2 h⁻¹. -1 The reaction temperature was 200℃, the hydrogen partial pressure was 7 MPa, and the hydrogen-to-oil volume ratio was 700.

[0091] Process Operation and Product Analysis: Heavy benzene is pre-treated, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0092] Example 9

[0093] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0094] 1 g of molecular sieve was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 120℃. The outlet temperature of the raw material heater was set to 300℃. Calcium oxide was loaded into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g of Ni-W / Al2O3 was loaded into catalytic zone A, and 1 g of Co-W / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 0.5 h⁻¹. -1 The reaction temperature was 400℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 600. The hydrodearomatization section consisted of 1 g Ni / Al₂O₃ packed in catalyst zone C and 1 g Ni / Al₂O₃ in catalyst zone D; the mass hourly space velocity (H₂H₀) for this section was 0.5 h⁻¹. -1 The reaction temperature was 250℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 600.

[0095] Process Operation and Product Analysis: The residual oil is pre-treated, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases in a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0096] Example 10

[0097] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0098] 1 g of activated carbon was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 200℃. The outlet temperature of the raw material heater was set to 300℃. Silica gel balls were packed into the hydrogen dryer as a desiccant. Hydrogen refining section: 0.6 g of Ni-Mo / Al2O3 was loaded into catalytic zone A, and 1.4 g of Ni-Co-Mo / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) of zone A in this section was 5 h⁻¹. -1 The mass hourly space velocity (MHSV) in zone B is 2.14 h⁻¹. -1 The reaction temperature was 300℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 800. The hydrodearomatization section consisted of a catalyst C zone packed with 1 g Pt / Al₂O₃ and a catalyst D zone packed with 1 g Ni / Al₂O₃; the mass hourly space velocity (H₂S₀) for this section was 3 h⁻¹. -1 The reaction temperature was 200℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 800.

[0099] Process Operation and Product Analysis: Gasoline is pre-treated and then vaporized in a heater. It is then mixed with dried hydrogen to form a mixed feed. This mixed feed is sequentially processed through a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases via a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0100] Example 11

[0101] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0102] 1 g of zinc oxide was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 50℃. The outlet temperature of the raw material heater was set to 400℃. Molecular sieves were loaded into the hydrogen dryer as a desiccant. Hydrogen refining section: 1.2 g of Ni-Mo / Al2O3 was loaded into catalytic zone A, and 0.8 g of Co-W / Al2O3 was loaded into catalytic zone B; the mass hourly space velocity (HHSV) of zone A in this section was 2.5 h⁻¹. -1 The mass hourly space velocity (MHSV) in zone B is 3.75 h. -1 The reaction temperature was 350℃, the hydrogen partial pressure was 3 MPa, and the hydrogen-to-oil volume ratio was 500. In the hydrodearomatization section: catalytic zone C was packed with 0.7 g Ni / Al₂O₃, and catalytic zone D was packed with 1.3 g Pt / Al₂O₃; the mass hourly space velocity (HHSV) in zone C of this section was 4.28 h⁻¹. -1 The mass hourly space velocity (MHSV) in region D is 2.3 h⁻¹. -1 The reaction temperature was 150℃, the hydrogen partial pressure was 3 MPa, and the hydrogen-to-oil volume ratio was 500.

[0103] Process Operation and Product Analysis: The raffinate oil is pre-treated, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0104] Comparative Example 1

[0105] This experiment does not include a pretreatment unit. The specific operating parameters for the feed preparation unit and the hydrogenation reaction unit are as follows:

[0106] The outlet temperature of the raw material heating furnace is set to 300℃. Silica gel balls are packed inside the hydrogen dryer as a desiccant. Hydrogen refining section: Catalytic zone A is packed with 1 g Ni-Mo / Al2O3, and catalytic zone B is packed with 1 g Co-Mo / Al2O3; the mass hourly space velocity (HHSV) for this section is 3 h⁻¹. -1 The reaction temperature was 300℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 800. The hydrodearomatization section consisted of catalytic zone C packed with 1 g Ni / Al₂O₃ and catalytic zone D packed with 1 g Ni / Al₂O₃; the mass hourly space velocity (H₂S₀) for this section was 3 h⁻¹. -1 The reaction temperature was 250℃, the hydrogen partial pressure was 5MPa, and the hydrogen-to-oil volume ratio was 800.

[0107] Process Operation and Product Analysis: Diesel fuel is fed into a pre-processor, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0108] Comparative Example 2

[0109] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0110] 1 g of activated carbon was loaded into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 200℃. The outlet temperature of the raw material heater was set to 200℃. Molecular sieves were loaded into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g of Ni-W / Al2O3 was loaded into catalytic zone A, and no catalyst was loaded into catalytic zone B; the mass hourly space velocity (WHSV) of this section was 1 h⁻¹. -1 The reaction temperature was 300℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 600. The hydrodearomatization section consisted of a catalyst C zone packed with 1 g Pt / Al₂O₃ and a catalyst D zone packed with 1 g Ni / Al₂O₃; the mass hourly space velocity (H₂S₀) for this section was 1 h⁻¹. -1The reaction temperature was 200℃, the hydrogen partial pressure was 5 MPa, and the hydrogen-to-oil volume ratio was 600.

[0111] Process Operation and Product Analysis: Diesel fuel is fed into a pre-processor, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0112] Comparative Example 3

[0113] The specific operating parameters for the feed pretreatment unit, feed preparation unit, and hydrogenation reaction unit are as follows:

[0114] A mixture of 0.5 g activated carbon and 0.5 g zinc oxide was packed into the pre-processor as an adsorbent, and the pre-treatment temperature was set to 250℃. The outlet temperature of the raw material heater was also set to 250℃. Silica gel balls were packed into the hydrogen dryer as a desiccant. Hydrogen refining section: 1 g Ni-Mo / Al2O3 was packed into catalytic zone A, and no catalyst was packed into catalytic zone B; the mass hourly space velocity (HHSV) for this section was 1 h⁻¹. -1 The reaction temperature was 400℃, the hydrogen partial pressure was 6 MPa, and the hydrogen-to-oil volume ratio was 700. In the hydrodearomatization section: catalytic zone C was loaded with 1 g of Ni / Al₂O₃, while catalytic zone D was unloaded; the mass hourly space velocity (WHSV) for this section was 1 h⁻¹. -1 The reaction temperature was 250℃, the hydrogen partial pressure was 6 MPa, and the hydrogen-to-oil volume ratio was 700.

[0115] Process Operation and Product Analysis: The raffinate oil is pre-treated, then vaporized in a heater, and mixed with dried hydrogen to form a mixed feed. This mixed feed is then sequentially reacted in a hydrorefining section (Area A → Area B) and a hydrodearomatization section (Area C → Area D). The reaction products are separated into gas and liquid phases by a stripping tower. The liquid product is collected and analyzed according to the analytical methods described in this invention. The key quality indicators of the obtained products are listed in Table 1.

[0116] Table 1 Comparison of impurity hydrogenation removal rate and aromatic removal rate between the examples and comparative products

[0117]

[0118] Note: The data in the table are the sampling and analysis results of each device after 240 hours of operation.

[0119] From the data in Table 1 and Figure 2A direct comparison shows that the two-stage, four-zone low-pressure hydrogenation process provided by this invention can achieve deep purification of fuel oil under significantly milder conditions (hydrogen pressure ≤ 8 MPa, temperature ≤ 400℃). Specifically, the aromatics removal rate is consistently above 96%, and the comprehensive removal rate of various heteroatoms (sulfur, nitrogen, chlorine, etc.) also exceeds 90%. In contrast, the comparative examples lack some relevant process flows (Comparative Example 1 lacks a pretreatment process, Comparative Example 2 is a two-stage, three-zone process, and Comparative Example 3 is a two-stage, two-zone process), resulting in a significant decrease in both aromatics removal and impurity removal rates. Furthermore, the feedstock oil in Example 1 and Comparative Example 1 is diesel oil, with a dark yellow color, while the product of Comparative Example 1 is significantly darker in color than that of Example 1. Figure 2 This directly demonstrates the crucial role of pretreatment in protecting the activity of subsequent catalysts and achieving deep hydrogenation. Therefore, this invention, through a systematic design of "pretreatment" and "two-stage, four-zone catalyst gradation," successfully achieves highly active and selective hydrodearomatization and deimpurification of fuel oil under low-pressure conditions.

[0120] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for producing ultra-low aromatic specialty oils by medium- and low-pressure hydrogenation, characterized in that: Includes the following steps: (1) Raw material pretreatment: The raw oil is passed into the preprocessor and contacted with the adsorbent at a preset temperature to remove impurities from the raw oil; (2) Feed preparation: The raw oil processed in step (1) is heated to vaporization and mixed with the dried hydrogen to form a mixed feed; (3) Two-stage four-zone hydrogenation reaction: The mixed feed is passed sequentially through a hydrogenation refining section and a hydrogenation dearomatization section arranged in series for reaction; The hydrorefining section includes a catalytic A zone and a catalytic B zone connected in sequence. The catalytic A zone is filled with a hydrodesulfurization catalyst for desulfurization, and the catalytic B zone is filled with a hydrodeoxygenation and dechlorination catalyst for deoxygenation and dechlorination. The hydrodearomatization section includes a catalytic C zone and a catalytic D zone connected in sequence, wherein the catalytic C zone and the catalytic D zone are filled with an aromatic hydrogenation catalyst for aromatic hydrogenation saturation. (4) Product separation and distillation: The hydrogenation reaction product obtained in step (3) is subjected to gas-liquid separation to obtain liquid product, and the liquid product is fractionated to obtain ultra-low aromatic special oil products of different fractions.

2. The process method according to claim 1, characterized in that, The adsorbent mentioned in step (1) is selected from one or more combinations of activated carbon, alumina, silicon dioxide, molecular sieve, calcium oxide, zinc oxide, and iron oxide; The amount of adsorbent added is 20% to 80% of the total catalyst loading in the subsequent hydrorefining stage; the pretreatment temperature is 20 to 300℃.

3. The method according to claim 1, characterized in that, In step (2), the temperature at which the raw oil is heated to vaporization is 200~400℃; the desiccant used for the hydrogen drying process is selected from calcium oxide, silica gel balls and molecular sieves.

4. The method according to claim 1, characterized in that, The operating conditions of the hydrorefining section are as follows: reaction temperature 200~400℃, hydrogen partial pressure 3~8 MPa, hydrogen-to-oil volume ratio 300~1000; and the mass hourly space velocity (MHV) of each of the catalytic A and catalytic B zones is 0.5~5 h⁻¹. -1 .

5. The method according to claim 1 or 4, characterized in that, In the hydrogenation refining section Catalytic region A is loaded with one of Ni-Mo / Al2O3 or Ni-W / Al2O3 catalysts, with a mass hourly space velocity of 0.5–5 h⁻¹. -1 ; Catalytic zone B is filled with Ni-Co-Mo / Al2O3, Ni-Co-W / Al2O3, Co-Mo / Al2O3, Co-W / Al2O3 One type of catalyst with a mass hourly space velocity (H₂S) of 0.5–5 h₂. -1 .

6. The method according to claim 1, characterized in that, The operating conditions for the hydrodearomatization section are as follows: reaction temperature 150-250℃, hydrogen partial pressure 3-8 MPa, hydrogen-to-oil volume ratio 300-1000; and the mass hourly space velocity (HHSV) of the catalytic C zone and catalytic D zone is independently 0.5-5 h⁻¹. -1 .

7. The method according to claim 1 or 6, characterized in that, In the hydrodearomatization section, catalytic region C and catalytic region D are each independently packed with one of Ni / Al2O3 or Pt / Al2O3 catalysts, with each having a mass hourly space velocity (WHSV) of 0.5–5 h⁻¹. -1 .

8. An apparatus for implementing the method of producing ultra-low aromatic specialty oils by medium- and low-pressure hydrogenation according to any one of claims 1 to 7, characterized in that, The apparatus, along the material flow direction, sequentially comprises: a raw material pretreatment unit, a feed preparation unit, a two-stage four-zone hydrogenation reaction unit, and a product separation and distillation unit; The raw material pretreatment unit is equipped with a preprocessor for holding the adsorbent and purifying the raw oil. The feed preparation unit includes a heating furnace for gasifying the pretreated raw material oil and a hydrogen dryer for drying hydrogen. The two-stage four-zone hydrogenation reaction unit includes a first-stage reactor and a second-stage reactor arranged in series. The first-stage reactor is a hydrogenation refining section, which is internally separated by a partition to form a catalytic zone A and a catalytic zone B connected in sequence, and each zone is filled with a catalyst with a corresponding function. The second-stage reactor is a hydrogenation dearomatization section, which is internally separated by a partition to form a catalytic zone C and a catalytic zone D connected in sequence, and each zone is filled with an aromatic hydrogenation catalyst. The product separation and distillation unit includes a stripping column for gas-liquid separation of hydrogenation reaction products and a distillation column for fractionation of liquid products, connected in sequence.

9. The apparatus according to claim 8, characterized in that, The catalyst in the hydrorefining section, catalytic region A, is one of Ni-Mo / Al2O3 and Ni-W / Al2O3, and the catalyst in catalytic region B is one of Ni-Co-Mo / Al2O3, Ni-Co-W / Al2O3, Co-Mo / Al2O3, and Co-W / Al2O3. The catalysts in the C and D regions of the hydrodearomatization section are each independently one of Ni / Al2O3 and Pt / Al2O3.

10. The apparatus according to claim 8, characterized in that, The feedstock oil being processed is selected from one of the following: gasoline, diesel, kerosene, coal tar, coal liquefaction oil, residue oil, condensate oil, heavy benzene, and residual oil.

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