CN110540873B

CN110540873B - Method for processing naphthenic oil

Info

Publication number: CN110540873B
Application number: CN201811291423.8A
Authority: CN
Inventors: 孙国权; 方向晨; 全辉; 姚春雷; 赵威; 张志银
Original assignee: China Petroleum and Chemical Corp; Sinopec Dalian Research Institute of Petroleum and Petrochemicals
Current assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2018-05-29
Filing date: 2018-10-31
Publication date: 2021-05-04
Anticipated expiration: 2038-10-31
Also published as: CN110540873A

Abstract

The invention discloses a method for processing naphthenic oil. The naphthenic base distillate oil is used as a raw material, and a two-stage series hydrogenation process of hydrotreating, hydrodewaxing and deep supplementary refining is adopted to produce the naphthenic base special oil. And (3) after the liquid generated oil obtained by the hydrotreating-hydrodewaxing reaction enters a complementary refining reaction zone, liquid-phase hydrofining reaction is carried out, and the obtained effluent is separated and fractionated to obtain the special oil product fraction. The method has simple flow and wide raw material adaptability, and is particularly suitable for the process of producing special oil products with good stability by the hydrogenation of naphthenic base raw materials.

Description

Method for processing naphthenic oil

Technical Field

The invention relates to a method for processing naphthenic oil, in particular to a method for producing naphthenic special oil by adopting a hydrogenation process.

Background

The traditional production of lubricant base oil adopts a solvent process, and the main two steps are solvent refining to remove non-ideal components such as aromatic hydrocarbon and the like and solvent dewaxing to ensure the low-temperature flow property of the base oil. In addition, clay or hydrorefining is generally performed.

The crude oil can be classified by adopting a characteristic factor K, and the paraffin base crude oil with the characteristic factor K larger than 12.1 is used; the characteristic factor K is 11.5-12.1, and the intermediate base crude oil is obtained; naphthenic base crude oils having a figure of merit K less than 11.5. The paraffin content of the paraffin-based distillate oil generally exceeds 50 percent, and the lubricating oil base oil with higher viscosity index, namely excellent viscosity-temperature performance can be produced by adopting the traditional lubricating oil base oil production process. The quantity of paraffin-based crude oil suitable for producing high viscosity index lubricating oil base oil by the traditional process is gradually reduced due to the deterioration of crude oil worldwide, so the technology for producing the lubricating oil by the hydrogenation method is developed rapidly. The hydrogenation process refers to a process for producing the lubricant base oil by adopting a combined process of hydrotreating or hydrocracking process-hydrodewaxing or isodewaxing-hydrofining, and has the advantages of high flexibility of raw materials, high yield of the base oil, high value of byproducts and the like. The naphthenic base crude oil has the characteristics of high density and viscosity, high content of aromatic hydrocarbon and naphthenic hydrocarbon, low condensation point and the like. The hydrogenation method can be adopted to produce the lubricating oil base oil which has no requirement on viscosity-temperature performance, such as electric oil, refrigerator oil, rubber filling oil and the like, and can fully utilize crude oil resources. The properties of the middle base crude oil are between those of the two crude oils, and only the lubricating base oil with medium viscosity index can be produced.

CN200410029869.5 describes a method for producing lube base oil by hydrotreating-hydrodewaxing-hydrofining, wherein the hydrotreating product of the method must be subjected to vapor-liquid separation, and the liquid product can enter the hydrodewaxing process. CN97196410.6 describes a method for producing lube base oil by hydrotreating-hydrodewaxing-hydrofining, wherein the feedstock of the method must be solvent refined before being hydrotreated, so as to meet the requirement that the viscosity index of the feedstock is greater than 75. The hydrogenation product must be separated from the gas and liquid to remove the hydrogen sulfide and ammonia from the hydrogenation material, and the liquid product can enter the hydrogenation pour point depression process. CN97122140.5 discloses a method for producing lube base oil by solvent refining-hydrotreating, which can greatly increase the viscosity index of raw material, but is not suitable for the process of producing naphthenic lube base oil with low requirement on viscosity index from naphthenic distillate oil raw material.

Isomerization dewaxing is a common method for improving the viscosity index of base oil of lubricating oil, but the method generally takes paraffin-based crude oil distillate as a raw material and has no obvious effect on naphthenic base crude oil distillate. The product after isodewaxing has poor stability and needs to be further refined, so the production process is more complicated and the cost is higher.

In summary, the suitable process for producing the naphthenic base special oil by the hydrogenation method is determined according to the characteristics of the raw materials and the requirements of the naphthenic base special oil product. The prior art can not meet the requirements of producing special oil products by naphthenic base distillate oil or light deoiling hydrogenation.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a naphthenic oil processing method which has strong raw material adaptability and simple and flexible process flow. The naphthenic base distillate oil is subjected to hydrogenation treatment, hydrodewaxing and deep supplementary refining reaction, and is subjected to proper rectification to produce the naphthenic base special oil product with higher quality.

The invention relates to a method for processing naphthenic oil, which comprises the following steps:

(1) mixing naphthenic base distillate oil and hydrogen, entering a hydrotreating reaction zone, and contacting with a hydrofining catalyst for reaction;

(2) the reaction effluent obtained in the step (1) enters a hydrodewaxing reaction zone and contacts a hydrodewaxing catalyst for reaction;

(3) performing gas-liquid separation on the effluent obtained in the step (2), mixing the obtained generated oil with hydrogen, feeding the mixture into a hydrogen mixing tank for hydrogen mixing, feeding the obtained saturated hydrogen-dissolved effluent into a complementary refining reaction zone, and contacting the effluent with a hydrogenation complementary refining catalyst for reaction;

(4) and (4) carrying out gas-liquid separation on the supplementary refining reaction effluent obtained in the step (3), and fractionating at least part of liquid to obtain a special oil product fraction.

In the invention, the naphthenic distillate can be at least one of naphthenic distillate oil, light deasphalted oil, coal tar hydrocracking tail oil or catalytic cracking diesel oil distillate. The naphthenic distillate has an aromatic content of 30 to 99 wt% and a density of 0.923 to 0.955 g/cm at 20 DEG C³. The distillation range of the naphthenic base distillate oil raw material is within any range of 140-600 ℃, the initial boiling point of the preferred naphthenic base distillate oil is 140-350 ℃, and the final boiling point is 400-600℃。

The hydrofining catalyst in the step (1) is a conventional hydrofining catalyst in the field, and can be a diesel hydrofining catalyst or a hydrocracking pretreatment catalyst. The hydrofining catalyst uses VIB group and/or VIII group metal as active component, uses alumina or silicon-containing alumina as carrier, and uses the VIB group metal as Mo and/or W, and uses the VIII group metal as Co and/or Ni. Based on the weight of the catalyst, the content of the VIB group metal is 10-50 wt% calculated by oxide, and the content of the VIII group metal is 3-15 wt% calculated by oxide; the properties are as follows: the specific surface area is 100-350 m²The pore volume is 0.15 to 0.6 mL/g. The selectable commercial catalysts are hydrogenation refining catalysts such as 3936, 3996, FF-16, FF-26, FF-36, FF-46, FF-56, FF-66 and the like which are researched and developed by the smooth petrochemical research institute of China petrochemical company Limited. It may be a similar catalyst developed by foreign catalyst companies, such as HC-K, HC-P catalyst by UOP, TK-555, TK-565 catalyst by Topsoe, KF-847, KF-848, etc. by AKZO.

The operation conditions of the hydrotreating reaction zone are as follows: the reaction pressure is 10.0-20.0 MPa, the reaction temperature is 300-420 ℃, the volume ratio of hydrogen to oil is 200-2000, and the volume airspeed is 0.1-3.0 h^-1(ii) a Preferably, the reaction pressure is 10.0-18.0 MPa, the volume ratio of hydrogen to oil is 500-1500, and the volume airspeed is 0.2-2.0 h^-1And the reaction temperature is 320-400 ℃.

The hydrodewaxing catalyst in the step (2) can be selected from lubricating oil hydrodewaxing catalysts commonly used in the field, can be commercial hydrodewaxing catalysts, such as 3881 and FDW-3 catalysts developed and developed by China petrochemical smoothing petrochemical research institute, and can also be prepared according to general knowledge in the field. The hydrogenation pour point depression reaction zone uses a hydrogenation pour point depression catalyst containing a ZSM-5 molecular sieve with proper acid distribution, the content of the ZSM-5 molecular sieve is 50wt% -85 wt% based on the weight of the catalyst, the hydrogenation pour point depression catalyst contains NiO and/or CoO which is 1.0 wt% -8.0 wt%, and the balance is a binder.

The operating conditions of the hydrogenation pour point depression reaction zone are as follows: the reaction pressure is 10.0-20.0 MPa, the reaction temperature is 300-420 ℃, the volume ratio of hydrogen to oil is 200-2000,the volume airspeed is 0.1-3.0 h^-1(ii) a Preferably, the reaction pressure is 10.0-18.0 MPa, the volume ratio of hydrogen to oil is 500-1200, and the volume airspeed is 0.2-2.0 h^-1And the reaction temperature is 320-400 ℃.

And (3) carrying out gas-liquid separation on the hydrodewaxing product in the step (3), carrying out saturated hydrogen dissolution on the obtained generated oil, and then, feeding the oil into a hydrofinishing reaction zone for treatment, wherein the hydrofinishing catalyst is a conventional noble metal hydrogenation catalyst in the field. The catalyst comprises the following components: noble metal Pt and/or Pd is/are used as a hydrogenation component, and a catalyst carrier consists of a small-grain Y-shaped molecular sieve, alumina and amorphous silica-alumina; the small-grain Y-type molecular sieve has the following properties, namely SiO₂/Al₂O₃The molar ratio is 40-120, the average diameter of crystal grains is 200-700 nm, preferably 300-500 nm, the unit cell constant is 2.425-2.435 nm, and the relative crystallinity is more than or equal to 95%, preferably 95-120%. The specific surface area of the catalyst is 900-1200 m²The pore volume is 0.5-0.80 mL/g, wherein the pore volume of the secondary mesopores with the diameter of 1.7-10 nm accounts for more than 50% of the total pore volume, preferably 50-80%, and more preferably 60-80%.

Based on the mass of the supplementary hydrofining catalyst, the content of Pt and/or Pd is generally 0.1-2%, and the rest is a carrier. The catalyst support generally comprises, on a mass basis: 5-40% of small-crystal-grain Y-shaped molecular sieve, 20-65% of amorphous silica-alumina and l 0-40% of alumina. The post-purification catalyst may be selected from any suitable commercial catalysts, or may be prepared according to conventional methods in the art, for example, CN104588073A discloses a method for preparing a post-purification catalyst.

The process conditions of the post-refining reaction zone are generally as follows: the reaction pressure is 4.0-20.0 MPa, preferably 10.0-15.0 MPa; the liquid hourly space velocity is 0.3-6.0 h^-1Preferably 0.5 to 3.0 hours^-1(ii) a The average reaction temperature is 150-380 ℃, preferably 200-360 ℃.

In the present invention, the post-polishing reaction zone preferably comprises two reaction zones connected in series, namely a first post-polishing zone and a second post-polishing zone. Correspondingly, the catalyst in the first additionally refining stage is an additionally refining catalyst A, and the catalyst in the second additionally refining stage is an additionally refining catalyst B. The metal content x2 in the catalyst B is lower than the metal content x1 in the catalyst A, and the content Y2 of the Y-type molecular sieve in the catalyst B is higher than the content Y1 of the Y-type molecular sieve in the catalyst A. Preferably, x2 is 0.1 to 1.5 percentage points lower than x1, and y2 is 5 to 50 percentage points higher than y 1. More preferably, x2 is 0.5 to 1.5 percentage points lower than x1, and y2 is 10 to 40 percentage points higher than y 1.

In the first and second additional refining stages, the additional refining catalyst used has different properties due to the difference in metal content and small-grained Y-type molecular sieve content. The supplemented and refined catalyst A has relatively high metal content and relatively low Y-type molecular sieve content, so that the hydrogenation performance is high and the cracking activity is weak. And (2) when the hydrogenated product of the hydrogenation treatment section is in contact reaction with a complementary refining catalyst A, unsaturated aromatic hydrocarbon generated by partial hydrogenation is subjected to further hydrogenation at a lower reaction temperature because the cracking activity of the catalyst is limited and the acid saturation function is strong, and most of carbon-carbon double bonds are saturated to obtain the naphthenic base special oil, so that the yield of the target product is improved.

The complementary refined catalyst B has relatively low metal content and higher Y-type molecular sieve content, so that the cracking performance of the catalyst is higher. The small ring or polycyclic naphthenic hydrocarbon with long side chain contained in the oil fraction generated by the catalyst A after the additional refining is further contacted with the additional refining catalyst B for reaction, the side chain on the naphthenic hydrocarbon is subjected to chain scission or isomerization reaction, and simultaneously, a small amount of unsaturated polycyclic aromatic hydrocarbon can be subjected to complete double bond saturation reaction.

Therefore, the catalyst grading combination adopted in the complementary refining stage well achieves the purposes of hydrogenation saturation of the polycyclic aromatic hydrocarbon in the distillate oil, retention of the polycyclic aromatic hydrocarbon in an ideal component, chain scission or isomerization of a long side chain on the cyclic hydrocarbon and pour point reduction. So that the hydrogenation method can be used for directly producing special oil products with good stability and high yield of target products.

In order to obtain better hydrogenation effect, the process conditions of the first and second additional refining sections should also be adaptively adjusted to match the catalyst grading scheme adopted by the additional refining section. If the average reaction temperature t2 of the second additional refining stage is higher than the average reaction temperature t1 of the first additional refining stage, t2 is preferably 10-150 ℃ higher than t1, and more preferably 30-120 ℃. The average reaction temperature of the first complementary refining reaction section is generally 150-350 ℃, and preferably 180-330 ℃; the average reaction temperature of the second additional refining reaction section is 180-380 ℃, preferably 220-350 ℃.

In the present invention, the first additional refining stage and the second additional refining stage may be disposed in one reactor, or may be disposed in two or more reactors, respectively.

In the present invention, the method may further comprise the step (5): and (4) recycling a part of the hydrofinishing liquid obtained in the step (4) to the step (3), mixing the hydrofinishing liquid with the liquid product obtained by hydrodewaxing, and then mixing the hydrogen with hydrogen.

The production method of the special oil product adopts two-stage process flow, and the oil generated in the hydrotreating-hydrodewaxing stage can be used as the feed of the supplementary refining stage only by simple steam stripping, so that the process is greatly simplified. The invention simplifies the process of the hydrogenation treatment of the naphthenic distillate and can ensure the product quality by selecting the catalyst with proper performance. The invention has strong raw material adaptability, adopts different hydrogenation-supplement refining catalyst grading combination modes according to different characteristics of the raw materials, can produce different types of special oil products, and has flexible process flow. And the reaction temperature gradient of the noble metal hydrogenation complementary refining reaction area is uniform, thereby being beneficial to reducing energy consumption, producing special oil products, greatly simplifying the process flow and saving the investment.

The hydrotreating reaction zone includes a catalyst that is a hydrofining catalyst. The hydrorefining catalyst has the functions of desulfurization, denitrification and aromatic hydrocarbon saturation. When the raw material is naphthenic base distillate oil or light deasphalted oil, and the lubricating oil base oil such as transformer oil, refrigerator oil and rubber filling oil which has no requirement on viscosity-temperature performance is produced, the hydrotreating reaction zone can be only used as a hydrotreating catalyst; the product of the hydrotreating reaction zone enters a reaction zone filled with a hydrodewaxing catalyst, the long side chain of the aromatic hydrocarbon is subjected to hydrodewaxing to reduce the pour point of the produced oil, and the produced oil is subjected to steam stripping separationRemoving H therefrom₂S and NH₃Then the saturated aromatic hydrocarbon can be fed into reaction zone in which the hydrogenation complementary refining catalyst is held, after the pour point of the product is reduced, the complementary refining product can be passed through the product separation process so as to obtain various special oil products with good stability.

The complementary refining catalyst used in the invention adopts a small-grain Y-shaped molecular sieve as an acid component, the Y-shaped molecular sieve has the characteristics of high silica-alumina ratio, high crystallinity, multiple secondary pores and large specific surface area, and is matched with amorphous silica-alumina and hydrogenation active metal components Pt and Pd, so that the exertion of aromatic hydrogenation saturation activity is promoted, the selective ring opening and chain scission of aromatic hydrocarbon are facilitated, the diffusion of reaction products is facilitated, and the carbon capacity is greatly enhanced, thereby improving the activity, selectivity and stability of the catalyst. The catalyst is especially suitable for hydrogenation dearomatization reaction of naphthenic base raw material, especially naphthenic base raw material with high viscosity and high content of polycyclic aromatic hydrocarbon.

In the present invention, two different types of the post-purification catalysts are preferably used in the post-purification reaction zone. The catalyst A used in the first additional refining section has stronger hydrogenation performance due to relatively higher metal content and lower Y-type molecular sieve content, and the proper cracking activity of the catalyst A also has important catalytic action on the hydrogenation saturation of the polycyclic aromatic hydrocarbon. While catalyst B used in the second additional refining stage had a relatively high Y-type molecular sieve content and a relatively low metal content and thus exhibited partial cracking activity. For naphthenic distillate, the partial cracking performance of the catalyst B can effectively carry out chain scission or isomerization reaction on the aromatic hydrocarbon with side chain alkane, and the pour point is further reduced. Therefore, the cyclic hydrocarbon generated by partial hydrogenation in the first complementary refining section can complete hydrogenation saturation of most or even all aromatic rings in the second complementary refining section at a relatively high reaction temperature, so as to obtain a special oil product with good stability.

Drawings

FIG. 1 is a schematic process flow diagram of the process of the present invention.

Detailed Description

The process of the present invention is described in more detail below with reference to specific examples.

As shown in figure 1, naphthenic base raw oil passes through a pipeline 1, circulating hydrogen passes through a pipeline 2, and the naphthenic base raw oil and the circulating hydrogen are mixed and then enter a hydrofining reactor 3 for reactions such as sulfur removal, nitrogen saturation and aromatic hydrocarbon saturation. The effluent of the hydrorefining reaction enters a hydrodewaxing reactor 5 through a pipeline 4, contacts with a hydrodewaxing catalyst, and undergoes a hydrodewaxing reaction with long side chain of aromatic hydrocarbon; the effluent of the hydrogenation and pour point depression reaction enters a gas-liquid separator 9 through a pipeline 6 for gas-liquid separation, and the obtained hydrogen-rich gas is treated through a pipeline 8 and optional hydrogen sulfide removal and then is mixed with make-up hydrogen introduced through a pipeline 7 to obtain circulating hydrogen; the obtained liquid generated oil is mixed with hydrogen gas through a pipeline 14 through a pipeline 10, then the mixed oil enters a hydrogen mixing tank 11 for full hydrogen mixing, the obtained effluent of saturated dissolved hydrogen enters a first supplementary refining reactor 13 through a pipeline 12, and the effluent of saturated dissolved hydrogen is contacted with a high-activity hydrogenation supplementary refining catalyst A for deep aromatic hydrogenation saturation reaction. The effluent obtained by the first supplementary refining enters a second supplementary refining reactor 16 through a pipeline 15, and is in contact reaction with a low-activity hydrogenation supplementary refining catalyst B to break chains of long side chains of cycloparaffins or isomerize and reduce pour points and saturate incompletely aromatic hydrocarbons, and meanwhile, the annular integrity of the cycloparaffins is kept, so that the low-temperature fluidity of a target product is facilitated. The second post-finishing reaction effluent is passed via line 17 to a gas-liquid separator 18 (typically comprising a high pressure separator and a low pressure separator) and the resulting hydrogen-rich gas is purified and withdrawn via line 19. The liquid obtained from the gas-liquid separator 18 enters a fractionating tower 21 through a pipeline 20, the gas is discharged through a pipeline 22, and the obtained special oil products with different specifications are discharged through

pipelines

23, 24 and 25 respectively.

Unless otherwise specified, the following percentages are mass percentages. Wherein, the Saybolt color of the solvent oil adopts GB/T3555, and the aromatic hydrocarbon content adopts GB/T17474 analysis method or analysis standard.

Example 1

As shown in the flow chart of figure 1, a hydrofining catalyst is used in a hydrotreating reaction zone, an FDW-3 catalyst is used in a hydrodewaxing reaction zone, and the catalyst in a complementary refining reaction zone is not segmented, but only one catalyst A is adopted. The properties of the catalysts used are shown in tables 2 and 3, respectively, and the properties of the specialty oil fractions obtained are shown in table 4.

The post-purification catalysts used in the examples were prepared according to the method disclosed in CN 104588073A.

Example 2

The hydrotreating and hydrodewaxing sections were as in example 1, with only catalyst B being used in the finishing reaction zone. The properties of the specialty oil fraction were also obtained as shown in Table 4.

Example 3

The hydrotreating and hydrodewaxing sections were as in example 1, the additional refining reaction zone was divided into two additional refining stages, and a catalyst A and a catalyst B were graded (the first additional refining stage was packed with catalyst A, and the second additional refining stage was packed with catalyst B). Meanwhile, the process conditions are also matched. The properties of the specialty oil fraction are shown in Table 4.

Example 4

The order of grading of the additionally refined catalyst was changed as in example 3. The properties of the specialty oil fraction were also obtained as shown in Table 4.

From the data listed in table 4, it can be seen that for the prior art scheme of feedstock hydrogenation, the properties of the special oils obtained under different conditions are different, and the catalyst grading method of example 3 is the best.

As can be seen from the data of examples 1-4, the naphthenic base oil raw material of the invention can obtain the special oil product with qualified pour point through the processes of hydrotreating, hydrodewaxing and deep supplementary hydrorefining. And wherein, the scheme of catalyst grading is adopted in the complementary refining reaction zone, and the obtained special oil product has better stability and more ideal hydrogenation effect.

TABLE 1 Properties of the stock oils

TABLE 2 physicochemical Properties of the hydrorefining catalyst

TABLE 3 supplementary refining catalyst Properties

TABLE 4 Process conditions and results

Claims

1. A process for treating naphthenic oils comprising the following:

(3) performing gas-liquid separation on the effluent obtained in the step (2), allowing the obtained generated oil and hydrogen to enter a hydrogen mixing tank for hydrogen mixing, allowing the obtained saturated hydrogen-dissolved effluent to enter a complementary refining reaction zone, and allowing the effluent to contact a hydrogenation complementary refining catalyst for reaction;

(4) performing gas-liquid separation on the supplementary refining reaction effluent obtained in the step (3), and fractionating at least part of obtained liquid to obtain a special oil product fraction;

the hydrogenation complementary refining catalyst takes precious metal Pt and/or Pd as a hydrogenation component, and a hydrogenation complementary refining catalyst carrier consists of a small-grain Y-shaped molecular sieve, alumina and amorphous silica-alumina;

the complementary refining reaction zone comprises two reaction sections connected in series, namely a first complementary refining section and a second complementary refining section, wherein the catalyst in the first complementary refining section is a complementary refining catalyst A, and the catalyst in the second complementary refining section is a complementary refining catalyst B, wherein the metal content x2 in the complementary refining catalyst B is lower than the metal content x1 in the complementary refining catalyst A, and the Y-type molecular sieve content Y2 in the complementary refining catalyst B is higher than the Y-type molecular sieve content Y1 in the complementary refining catalyst A.

2. The method of claim 1, wherein the naphthenic distillate oil has an aromatics content of 30 to 99 wt% and a density of 0.923 to 0.955 g/cm at 20 ℃³。

3. The process of claim 2, wherein the naphthenic distillate oil has a primary boiling point of 140 to 350 ℃ and a final boiling point of 400 to 600 ℃.

4. The process of claim 2 or 3, wherein said naphthenic distillate is selected from at least one of naphthenic distillate, light deasphalted oil, coal tar hydrocracked tail oil, or catalytically cracked diesel fraction.

5. The process of claim 1, wherein the hydroprocessing reaction zone is operated at conditions of: the reaction pressure is 10.0-20.0 MPa, the reaction temperature is 300-420 ℃, the volume ratio of hydrogen to oil is 200-2000, and the volume airspeed is 0.1-3.0 h^-1。

6. The process of claim 1 wherein the hydrodewaxing catalyst comprises ZSM-5 molecular sieve, the ZSM-5 molecular sieve being present in an amount of from 50wt% to 85wt%, NiO or CoO being present in an amount of from 1.0 wt% to 8.0 wt%, the balance being binder, based on the weight of the hydrodewaxing catalyst.

7. The process of claim 1 wherein said hydrodewaxing reaction zone is operated at conditions which are: the reaction pressure is 10.0-20.0 MPa, the reaction temperature is 300-420 ℃, the volume ratio of hydrogen to oil is 200-2000, and the volume airspeed is 0.1-3.0 h^-1。

8. The method of claim 1, wherein the small-grained Y-type molecular sieve has the following properties, SiO₂/Al₂O₃The molar ratio is 40-120, the average diameter of crystal grains is 200-700 nm, and the unit cell constant is 2.425-2.435 nm; the specific surface area of the hydrofinishing catalyst is 900-1200 m²The pore volume is 0.5-0.80 mL/g, wherein the pore volume of the secondary mesopores with the diameter of 1.7-10 nm accounts for more than 50% of the total pore volume.

9. The method according to claim 8, wherein the small-grained Y-type molecular sieve has a grain average diameter of 300 to 500 nm.

10. The method according to claim 8, wherein in the hydrofinishing catalyst, the pore volume of secondary mesopores of 1.7 to 10nm accounts for 50 to 80 percent of the total pore volume.

11. The process according to claim 8, wherein the content of Pt and/or Pd is 0.1 to 2% by mass based on the mass of the hydrorefining catalyst; the hydrofinishing catalyst carrier comprises the following components by mass: 5-40% of small-crystal-grain Y-type molecular sieve, 20-65% of amorphous silica-alumina and 78-40% of alumina l 0%.

12. The process of claim 1, wherein the process conditions in the post-polishing reaction zone are: the reaction pressure is 4.0-20.0 MPa, and the liquid hourly space velocity is 0.3-6.0 h^-1The volume ratio of hydrogen to oil is 50-3000, and the average reaction temperature is 150-380 ℃.

13. The method of claim 1, wherein x2 is 0.1 to 1.5 percentage points lower than x1 and y2 is 5 to 50 percentage points higher than y 1.

14. The process according to claim 13, wherein the average reaction temperature t2 of the second additional refining stage is higher than the average reaction temperature t1 of the first additional refining stage.

15. The process according to claim 14, wherein the average reaction temperature of the first additional refining reaction zone is 150 to 350 ℃ and the average reaction temperature of the second additional refining reaction zone is 180 to 380 ℃.

16. The method of claim 13, wherein x2 is 0.5 to 1.5 percentage points lower than x1 and y2 is 10 to 40 percentage points higher than y 1.

17. The process of claim 14 or 15, wherein t2 is 10 to 150 ℃ higher than t 1.

18. The process according to claim 15, wherein the average reaction temperature of the first additional refining reaction zone is 180 to 330 ℃ and the average reaction temperature of the second additional refining reaction zone is 220 to 350 ℃.