A method for hydrodewaxing

Abstract

The application discloses a method for hydrogenation and condensation, wherein high-chain alkane content raw oil is separated after passing through a hydrogenation and condensation catalyst filled in a hydrogenation and condensation reaction zone to obtain low-condensation diesel oil products. The hydrogenation and condensation catalyst filled in the hydrogenation and condensation reaction zone contains 5-30% Y molecular sieve, 2-20% β molecular sieve, 1-30% Group VIII B and / or Group VIII metal hydrogenation active metal and 0-15% carbon, with the weight of the hydrogenation and condensation catalyst as the basis. Preferably, the hydrogenation and condensation catalyst contains 10-20% Y molecular sieve, 5-15% β molecular sieve, 4-26% Group VIII B and / or Group VIII metal hydrogenation active metal and 0.1-7% carbon. The carbon content of the hydrogenation and condensation catalyst filled in the hydrogenation and condensation reaction zone shows an increasing trend along the flow direction. The method can save the cold hydrogen amount of a reaction device, effectively alleviate the concentrated heat release problem caused by the single molecular type of the raw oil, significantly improve the yield of the low-condensation diesel oil, and increase the isomeric hydrocarbon content of the diesel oil products.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for hydrodewaxing, in particular to a method for hydrodewaxing of high paraffin content feedstock. BACKGROUND

[0002] The demand for low pour point diesel in China is strong, and the production of low pour point diesel is highly profitable. The yield of diesel is restricted by the properties of feedstock and the pour point of diesel product, which is a key problem that restricts the profitability of oil refining enterprises.

[0003] For feedstock with high content of linear alkanes, excessive acidity can cause severe cracking of linear alkanes, resulting in excessive naphtha fraction in the oil and reducing the yield of diesel product. In addition, in actual production, due to the excessive content of linear alkanes in the feedstock and the single type of molecules, concentrated heat release can easily occur at a certain reaction temperature point. In order to suppress heat release, a large amount of cold hydrogen needs to be injected into each bed of the reaction device, resulting in high consumption of cold hydrogen. Excessive acidity of the catalyst can cause excessive cracking of linear alkanes, and low activity can cause low cracking rate of long linear alkanes, affecting the yield of diesel product. Therefore, there is an urgent need for a method that can fully crack long linear alkanes, while preserving medium length linear alkanes from excessive cracking, and fully isomerize medium length linear alkanes, to reduce the pour point of diesel product and improve the yield of diesel product.

[0004] The current method for industrial production of Y-type molecular sieves generally uses a directing agent method. The ordinary Y-type molecular sieves prepared by this method have a crystal size of about 1 µm, and there are about 300-400 unit cells in each dimension. The proportion of pores with a pore diameter less than 1 nm in the ordinary Y-type molecular sieves prepared by conventional synthesis is 15%-20%, the proportion of pores with a pore diameter of 1 nm-10 nm is 45%-50%, and the proportion of pores with a pore diameter greater than 10 nm is 30%-40%. For large molecule cracking reactions, the ideal pore size range suitable for feedstock reaction and product diffusion is 1 nm-10 nm. Although the Y-type molecular sieves can be modified to adjust the distribution of the ideal pore size range, the pore size distribution of the original molecular sieves directly determines the pore size distribution of the modified molecular sieves, and the pore expansion can affect the framework structure of the molecular sieves, thereby affecting the activity and stability of the molecular sieves. β zeolite is a medium pore, high-silicon zeolite with a three-dimensional twelve-membered ring pore structure developed successfully by the United States Mobil Company in the 1960s. Its pore channel is between ZSM-5 type molecular sieves and Y type molecular sieves, and it has high thermal stability. Since the late 1980s, scholars from various countries have been actively researching β zeolite. Due to its unique pore structure and excellent catalytic performance, β zeolite has broad application prospects in the petroleum and chemical industries.

[0005] CN112725022A discloses a method for hydrogenation dewaxing, which is to use 1,3,5-triisopropylbenzene as raw material, to treat the outer surface of the catalyst to reduce or remove the acid sites on the outer surface of the dewaxing catalyst, and to improve the yield of diesel product. CN201010514141.7 discloses a method for hydrogenation dewaxing of diesel, which process is as follows: the waxy diesel raw material passes through the hydrogenation dewaxing catalyst bed and the hydrogenation refining catalyst bed in turn, and the final hydrogenation refined product is separated to obtain diesel product. CN107345153A discloses a method for producing low-condensation diesel by hydrogenation cracking, which uses a large-grained, high-crystallinity, and effective pore size distribution concentrated Y-type molecular sieve as the cracking component and modified beta molecular sieve as the modified cracking component. This method is particularly suitable for treating high-condensation point waxy diesel under medium pressure conditions, has high catalytic activity and diesel selectivity, and the condensation point of the diesel fraction is greatly reduced, and the product properties of the diesel are improved. CN1769390A discloses a method for producing high-quality low-condensation diesel from distillate oil, which includes a hydrogenation refining reaction zone and a hydrogenation dewaxing reaction zone, wherein the upper part of the hydrogenation dewaxing reaction zone is provided with a flash section, the lower part is provided with a hydrogenation dewaxing section, and hot hydrogen gas is injected at the bottom of the hydrogenation dewaxing reaction zone. The temperature difference of the dewaxing reaction zone is small, which fully utilizes the hydrogenation activity of the refining catalyst and the selectivity of the dewaxing catalyst. CN104611043A discloses a method for producing low-condensation diesel, which is to pass the raw oil through the mixed catalyst bed of the hydrogenation dewaxing catalyst and the hydrogenation modification isomerization dewaxing catalyst and the hydrogenation dewaxing catalyst bed in turn, which reasonably combines the temperature rise of the modification process and the temperature drop of the hydrogenation dewaxing process.

[0006] The above-mentioned patents improve the product yield and quality of the hydrogenation dewaxing device by improving the catalyst or adjusting the process, but for the raw material oil with high paraffin content and single molecular type, it is still necessary to improve the catalyst and the catalyst loading mode to meet the needs of diesel yield and isomerization performance of the catalyst. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a hydrogenation dewaxing method, which can save the amount of cold hydrogen of the reaction device, effectively alleviate the concentrated heat release problem caused by the single molecular type of the raw material oil, significantly improve the yield of low-condensation diesel, and increase the isomerate content of the diesel product.

[0008] A method for hydrodewaxing, a high paraffin content feedstock oil is separated after passing through a hydrodewaxing catalyst packed in a hydrodewaxing reaction zone, to obtain a low freezing diesel product, the hydrodewaxing catalyst packed in the hydrodewaxing reaction zone contains 5-30% Y zeolite, 2-20% β zeolite, 1-30% Group VIII B and / or Group VIII hydrogenation active metal, and 0-15% carbon, based on the weight of the catalyst; preferably, the Y zeolite content is 10-20%, the β zeolite content is 5-15%, the Group VIII B and / or Group VIII hydrogenation active metal content is 4-26%, and the carbon content is 0.1-7%, for example, 0.5%, 1%, 2%, 3%, 4%, 5% or 6%; the carbon content of the hydrodewaxing catalyst packed in the hydrodewaxing reaction zone increases along the flow direction.

[0009] In the above method, the distillation range of the high paraffin content feedstock oil is 50-800°C, preferably 150-500°C; the paraffin mass content of the high paraffin content feedstock oil is 80% or more, preferably 90% or more; preferably, the linear paraffin mass content of the high paraffin content feedstock oil is 80% or more, preferably 90% or more, and most preferably 95% or more.

[0010] In the above method, the molar ratio of silicon to aluminum of the Y zeolite is 10-150, preferably 10-120. The molar ratio of silicon to aluminum of the β zeolite is 10-150, preferably 10-120. The Group VIII B metal is one or more of Mo and W, and the Group VIII metal is one or more of Co and Ni.

[0011] In the above method, the reaction pressure of the hydrodewaxing reaction zone is 2-20 MPa, the space velocity is 0.1-5 h -1 -5 h -1 , the hydrogen to oil volume ratio is 1:100-1:2000, preferably 1:500-1:1500.

[0012] In the above method, the hydrodewaxing catalyst packed in the hydrodewaxing reaction zone contains at least N kinds of hydrodewaxing catalysts along the flow direction according to the carbon mass content, N is at least 2, preferably 2-6, and most preferably 3-4; the carbon mass content of the Nth hydrodewaxing catalyst is 0.1-10% higher than that of the N-1th hydrodewaxing catalyst, preferably 0.5-7% higher, and further preferably 1-5% higher; the packing volume ratio of the Nth hydrodewaxing catalyst to the N-1th hydrodewaxing catalyst is 1:0.1-1:10, preferably 1:0.5-1:5.0.

[0013] In the above method, the contents of Y zeolite, β zeolite and Group VIII B and / or Group VIII hydrogenation active metal in the hydrodewaxing catalyst packed in the hydrodewaxing reaction zone can be the same or different, preferably the same.

[0014] In the above method, the hydrodewaxing catalyst packed in the hydrodewaxing reaction zone is obtained by one of the following methods:

[0015] Method one: first, a hydrodewaxing catalyst containing Y zeolite, β zeolite, Group VIII B and / or Group VIII hydrogenation active metal is prepared or selected; then, different depth carbon deposition treatment is carried out to obtain a final hydrodewaxing catalyst with different carbon content;

[0016] Method two: the spent hydrodewaxing catalyst containing Y zeolite, β zeolite, Group VIII B and / or Group VIII hydrogenation active metal is first purged with hydrogen, the volume flow ratio of hydrogen to catalyst is 1:1~2000:1, preferably 200:1~1500:1, the purging time is 1h~48h, and / or the spent catalyst is immersed in oil-soluble substances such as ethanol and / or n-heptane and / or petroleum ether with a mass content of 90%~100% for 1h~48h, after solid-liquid separation, drying, the drying temperature is 30℃~260℃, and the drying time is 0.5h~10h. The above immersion process can be mixed with two or more oil-soluble substances, or immersed separately, by the above method, the oil content of the spent catalyst is reduced to 1%~5%; then, calcination regeneration treatment is carried out to obtain a hydrodewaxing catalyst with different carbon content.

[0017] In the above method (1), the different depth carbon deposition treatment method can be high temperature heat treatment of the hydrodewaxing catalyst commodity or self-made hydrodewaxing catalyst with high gum content. A non-limiting pretreatment method of the present application is as follows: the commercially available or self-made hydrodewaxing catalyst is placed in a pressure vessel, oil with high gum content is used as raw material, the reaction pressure in the pressure vessel is 4~20MPa, the reaction temperature is 200~500℃, and the treatment time is 1~24h, then the final catalyst is obtained after drying and calcination. The oil with high gum content has a gum content of 1%~30%, a distillation range of 150℃~600℃, and an aromatic hydrocarbon content of 30%~80%. The drying temperature is 150~400℃. The calcination temperature is 300~700℃.

[0018] In the above method, the hydrogenation-dewaxing catalyst loaded in the hydrogenation-dewaxing reaction zone is preferably prepared by the following method: hydrogenation-dewaxing catalyst containing Y molecular sieve, β molecular sieve, Group VIII B and / or Group VIII metal hydrogenation active metal is first purged with hydrogen, and / or the spent catalyst is immersed in oil-soluble substances such as ethanol and / or n-heptane and / or petroleum ether, and the above immersion process can be immersion in a mixture of two or more oil-soluble substances, or separate immersion in multiple oil-soluble substances. Through the above method, the oil content of the spent catalyst is reduced to between 1wt% and 5wt%. Then, the regenerated treatment of calcination is carried out, and the temperature and time of calcination are controlled to obtain hydrogenation-dewaxing catalysts with different carbon contents. The hydrogenation-dewaxing catalyst prepared by the above method can not only improve the mass content and yield of isoparaffin in diesel oil, but also simplify the regeneration process.

[0019] Compared with the prior art, the hydrogenation-dewaxing method of the present application can solve the problem that excessive content of alkanes, especially straight-chain alkanes, in the raw oil leads to concentrated heat release, making it difficult to control the temperature of the reactor, and easily leading to the occurrence of the phenomenon of temperature runaway. Although the reactor bed size is large at home and abroad at present, and cold hydrogen can be injected between the beds to reduce the temperature of the reactor bed, for oil with high content of alkanes, which is prone to concentrated reaction heat release, increasing the amount of injected cold hydrogen cannot fundamentally solve the problem of temperature rise in the catalyst bed. The hydrogenation-dewaxing method of the present application can effectively inhibit the excessive cracking of straight-chain alkanes, improve the isomerization rate of straight-chain alkanes, and achieve the purpose of improving the yield of low-condensation diesel oil by loading hydrogenation-dewaxing catalysts with different carbon mass contents. DETAILED DESCRIPTION

[0020] The effects and advantages of the method of the present application will be further illustrated below in combination with examples and comparative examples, but the following examples do not constitute a limitation on the method of the present application, and the % mentioned in the upper limit of the present application is mass percent, unless otherwise specified.

[0021] In the above method, the regenerated hydrogenation-dewaxing catalyst loaded in the hydrogenation-dewaxing reaction zone has Y molecular sieve and β molecular sieve as acidic components, and Group VIII B and / or Group VIII metal as hydrogenation active metal component. Based on the weight of the regenerated hydrogenation-dewaxing catalyst, the weight content of the hydrogenation active metal component calculated as an oxide is 1% to 30%, the weight content of Y molecular sieve is 5% to 30%, and the weight content of β molecular sieve is 2% to 20%.

[0022] In the above method, the regenerated de-waxing catalyst is prepared by uniformly retaining different degrees of carbon deposition by heat treatment of the spent de-waxing catalyst.

[0023] The pre-treatment method used in the embodiments of the present application is as follows: the spent hydrodewaxing catalyst is immersed in n-heptane and ethanol for 1-48 hours respectively, and then the immersed spent hydrodewaxing catalyst is calcined in a calcining furnace to obtain the final regenerated hydrodewaxing catalyst.

[0024] The spent hydrodewaxing catalyst is an inactivated hydrodewaxing catalyst used in a laboratory or a refinery.

[0025] The raw oil used in the use of the spent hydrodewaxing catalyst can be straight-run diesel, catalytic diesel, vacuum gas oil, etc.

[0026] The spent hydrodewaxing catalyst used in the embodiments and the comparative examples has the following composition: Y molecular sieve and β molecular sieve are used as the acidic component, W and Ni are used as the hydrogenation active metal component, the content of Y molecular sieve is 15% based on the weight of the spent hydrodewaxing catalyst, the content of β molecular sieve is 10%, the content of W is 19% as calculated in the form of oxide, the content of Ni is 8% as calculated in the form of oxide, the content of small-pore alumina is 15%, the content of carbon is 6.82%, the content of amorphous silicon aluminum z is 26.18%, and the molar ratio of silicon oxide to aluminum oxide is 1.0:2.4, and the physical properties of the spent catalyst are shown in Table 1.

[0027] In the embodiments and the comparative examples of the present application, the operating conditions of the hydrodewaxing reaction zone are as follows: the reaction pressure is 8.0 MPa, the volume ratio of light oil is 600:1, the volume space velocity is 2.5 h -1 , the reaction temperature is 340℃, and the properties of the high paraffin raw oil are shown in Table 2.

[0028] Table 1 Physical properties of the spent catalyst

[0029]

[0030] Table 2 Properties of the raw oil

[0031]

[0032] Comparative Example 1

[0033] The hydrodewaxing catalyst used in the comparative example is a brand new one, and the composition of the catalyst is as follows: the content of Y molecular sieve is 15% based on the weight of the hydrodewaxing catalyst, the content of β molecular sieve is 10%, the content of W is 19% as calculated in the form of oxide, the content of Ni is 8% as calculated in the form of oxide, the content of carbon is 6.82%, the content of small-pore alumina is 15%, the content of amorphous silicon aluminum is 26.18%, and the molar ratio of silicon oxide to aluminum oxide is 1.0:2.4, and the hydrodewaxing catalyst is not layered either. The raw oil used is shown in Table 2, and the hydrodewaxing product distribution and properties are shown in Table 3.

[0034] Table 3

[0035]

[0036] Example 1

[0037] The packed regenerated hydrodewaxing catalyst was packed in two stages from top to bottom by the following treatment: the first stage used the spent catalyst shown in Table 1, soaked in anhydrous ethanol for 24 h, dried at 80°C for 3 h, and calcined at a temperature of 450°C for 3 h, and the carbon content of the catalyst was 0.12% as measured under normal pressure. The second stage used the spent catalyst shown in Table 1, soaked in anhydrous ethanol for 12 h, dried at 90°C for 3 h, and calcined at a temperature of 400°C for 1 h, and the carbon content of the catalyst was 4.5% as measured under normal pressure. The volume ratio of the catalysts packed in the first stage to the second stage was 1:1. The raw material described in Table 2 was used, and the hydrodewaxed product distribution and properties are shown in Table 4.

[0038] Table 4

[0039]

[0040] Example 2

[0041] The packed hydrodewaxing catalyst was packed in four stages from top to bottom by the following treatment: the first stage used the spent catalyst shown in Table 1, soaked in petroleum ether for 8 h, dried at 70°C for 5 h, calcined at a temperature of 440°C for 5 h, and the carbon content of the catalyst was 0.5% as measured under normal pressure. The second stage used the spent catalyst shown in Table 1, soaked in n-heptane for 10 h, dried at 100°C for 3 h, calcined at a temperature of 430°C for 2 h, and the carbon content of the catalyst was 1.2% as measured under normal pressure. The third stage used the spent catalyst shown in Table 1, soaked in petroleum ether for 9 h, dried at 120°C for 6 h, calcined at a temperature of 370°C for 4 h, and the carbon content of the catalyst was 2.3% as measured under normal pressure. The fourth stage used the spent catalyst shown in Table 1, soaked in petroleum ether for 10 h, dried at 70°C for 4 h, calcined at a temperature of 320°C for 2 h, and the carbon content of the catalyst was 4.1% as measured under normal pressure. The volume ratio of the catalysts packed in the first stage to the fourth stage was 1:1:3:2. The raw material described in Table 1 was used, and the hydrodewaxed product distribution and properties are shown in Table 5.

[0042] Table 5

[0043]

[0044] Example 3

[0045] The packed hydrogenation catalyst was packed in 3 stages from top to bottom by the following treatment: the first stage used the spent catalyst shown in Table 1, soaked in anhydrous ethanol for 7 h, dried at 75°C for 3.5 h, the calcination temperature was 520°C, the calcination time was 3 h, and the carbon deposition of the catalyst was 0.7% under normal pressure. The second stage used the spent catalyst shown in Table 1, soaked in petroleum ether for 5 h, dried at 95°C for 4.5 h, the calcination temperature was 400°C, the calcination time was 3 h, and the carbon deposition of the catalyst was 2.8% under normal pressure. The third stage used the spent catalyst shown in Table 1, soaked in petroleum ether for 15 h, dried at 115°C for 6.5 h, the calcination temperature was 360°C, the calcination time was 0.5 h, and the carbon deposition of the catalyst was 4.7% under normal pressure. The volume ratio of the catalysts packed in the first stage to the third stage was 1:2:2. The raw material described in Table 1 was used, and the product distribution and properties of the hydrogenation dewaxing were shown in Table 6.

[0046] Table 6

[0047]

[0048] Example 4

[0049] The packed hydrogenation catalyst was packed in 5 stages from top to bottom by the following treatment: the first stage used the spent catalyst shown in Table 1, soaked in n-heptane for 18 h, dried at 85°C for 8 h, the calcination temperature was 570°C, the calcination time was 1 h, and the carbon deposition of the catalyst was 0.6% under normal pressure. The second stage used the spent catalyst shown in Table 1, soaked in anhydrous ethanol for 13 h, dried at 105°C for 8 h, the calcination temperature was 390°C, the calcination time was 5 h, and the carbon deposition of the catalyst was 1.7% under normal pressure. The third stage used the spent catalyst shown in Table 1, soaked in anhydrous ethanol for 15 h, dried at 95°C for 9 h, the calcination temperature was 380°C, the calcination time was 2 h, and the carbon deposition of the catalyst was 2.8% under normal pressure. The fourth stage used the spent catalyst shown in Table 1, soaked in petroleum ether for 24 h, dried at 125°C for 5 h, the calcination temperature was 360°C, the calcination time was 2 h, and the carbon deposition of the catalyst was 3.9% under normal pressure. The fifth stage used the spent catalyst shown in Table 1, soaked in anhydrous ethanol for 7.5 h, dried at 130°C for 5.5 h, the calcination temperature was 300°C, the calcination time was 1 h, and the carbon deposition of the catalyst was 4.6% under normal pressure. The volume ratio of the catalysts packed in the first stage to the fifth stage was 1:3:2:2:1. The raw material described in Table 1 was used, and the product distribution and properties of the hydrogenation dewaxing were shown in Table 7.

[0050] Table 7

[0051]

[0052] Example 5

[0053] The packed hydrogenation catalyst was packed in four stages from top to bottom by the following treatment: the first stage used the spent catalyst shown in Table 1, hydrogen purging, the volume flow rate of hydrogen to the volume of catalyst was 1200h -1 : 1, the purging time was 8h, the calcination temperature was 470°C, the calcination time was 5h, the carbon deposition of the catalyst was 0.02% under normal pressure. The second stage used the spent catalyst shown in Table 1, hydrogen purging, the volume flow rate of hydrogen to the volume of catalyst was 1500h -1 : 1, the purging time was 28h, the calcination temperature was 450°C, the calcination time was 0.5h, the carbon deposition of the catalyst was 1.2% under normal pressure. The third stage used the spent catalyst shown in Table 1, hydrogen purging, the volume flow rate of hydrogen to the volume of catalyst was 800h -1 : 1, the purging time was 12h, the calcination temperature was 400°C, the calcination time was 0.5h, the carbon deposition of the catalyst was 3.8% under normal pressure. The fourth stage used the spent catalyst shown in Table 1, hydrogen purging, the volume flow rate of hydrogen to the volume of catalyst was 500h -1 : 1, the purging time was 19h, the calcination temperature was 280°C, the calcination time was 1h, the carbon deposition of the catalyst was 5.12% under normal pressure. The volume ratio of the catalyst packed in the first stage to the fourth stage was 1:1:3:1. The raw material used was shown in Table 1, the product distribution and properties of the hydrogenation catalyst were shown in Table 8.

[0054] Table 8

[0055]

[0056] Example 6

[0057] The packed hydrogenation catalyst was packed in four stages from top to bottom by the following treatment: the first stage used the spent catalyst shown in Table 1, hydrogen purging, the volume flow rate of hydrogen to the volume of catalyst was 1200h -1:1, the carbon deposition amount of the catalyst was 2.1% under normal pressure, the purging time was 12h, and the calcination temperature was 460℃ and the calcination time was 0.5h. The spent catalyst of the second stage was soaked in petroleum ether for 18h, dried at 110℃ for 5h, and the carbon deposition amount of the catalyst was 3.2% under normal pressure, the calcination temperature was 340℃ and the calcination time was 6h. The spent catalyst of the third stage was soaked in anhydrous ethanol for 22h, dried at 90℃ for 8h, and the carbon deposition amount of the catalyst was 4.1% under normal pressure, the calcination temperature was 320℃ and the calcination time was 1h. The spent catalyst of the fourth stage was soaked in petroleum ether for 24h, dried at 125℃ for 5h, and the carbon deposition amount of the catalyst was 5.12% under normal pressure, the calcination temperature was 300℃ and the calcination time was 0.5h. The volume ratio of the catalysts of the first stage to the fourth stage was 1:2:2:3. The raw material was used as described in Table 1, and the product distribution and properties of the hydrodewaxing product were shown in Table 9.

[0058] Table 9

[0059]

Claims

1. A method for dewaxing by hydrogen, characterized in that: High-alkane feedstock is separated after passing through a hydrodewaxing catalyst packed in a hydrodewaxing reaction zone to obtain low-pour-point diesel product. The hydrodewaxing catalyst packed in the hydrodewaxing reaction zone has, by weight, a Y molecular sieve content of 5%~30%, a β molecular sieve content of 2%~20%, a Group VIB and / or Group VIII metal hydrotreating active metal content of 1%~30%, and a carbon content of 0.1%~7%. The carbon content of the hydrodewaxing catalyst packed in the hydrodewaxing reaction zone increases by mass along the flow direction. The hydrogen-induced condensation depressant reaction zone is filled with at least N kinds of hydrogen-induced condensation depressant catalysts along the material flow direction according to the different carbon mass contents, and the N is at least 2. The high-alkane-content feedstock oil has an alkane content of over 80% by mass.

2. The method according to claim 1, characterized in that: The hydrogen dewaxing catalyst packed in the hydrogen dewaxing reaction zone contains, by weight, 10% to 20% Y molecular sieve, 5% to 15% β molecular sieve, and 4% to 26% active metal for hydrogenation of Group VIB and / or Group VIII metals.

3. The method according to claim 1, characterized in that: The high-alkane-content feedstock oil has a distillation range of 50–800°C; the alkane content of the high-alkane-content feedstock oil is above 90% by mass.

4. The method according to claim 3, characterized in that: The high-alkane-content feedstock oil has a distillation range of 150–500°C.

5. The method according to claim 3, characterized in that: The high-alkane-content feedstock oil contains more than 95% straight-chain alkanes by mass.

6. The method according to claim 1, characterized in that: The silicon-aluminum molar ratio of the Y molecular sieve is 10–150.

7. The method according to claim 6, characterized in that: The silicon-to-aluminum molar ratio of the Y molecular sieve is 10–120.

8. The method according to claim 1, characterized in that: The silicon-to-aluminum molar ratio of the β-zeolite is 10–150.

9. The method according to claim 8, characterized in that: The silicon-to-aluminum molar ratio of the β-zeolite is 10–120.

10. The method according to claim 1, characterized in that: The Group VIB metal is one or both of Mo and W, and the Group VIII metal is one or both of Co and Ni.

11. The method according to claim 1, characterized in that: The reaction pressure in the hydrogen decondensation reaction zone is 2 MPa to 20 MPa, and the space velocity is 0.1 h⁻¹. -1 ~5h -1 The hydrogen-to-oil volume ratio is 1:100 to 1:2000.

12. The method according to claim 11, characterized in that: The hydrogen-to-oil volume ratio is 1:500 to 1:1500.

13. The method according to claim 1, characterized in that: The value of N is 2 to 6.

14. The method according to claim 13, characterized in that: The value of N is 3 to 4.

15. The method according to claim 1, characterized in that: The carbon mass content in the Nth hydrodewaxing catalyst is 0.1% to 10% higher than that in the (N-1)th hydrodewaxing catalyst; the loading volume ratio of the Nth hydrodewaxing catalyst to the (N-1)th hydrodewaxing catalyst is 1:0.1 to 1:

10.

16. The method according to claim 15, characterized in that: The carbon mass content in the Nth hydrodewaxing catalyst is 0.5% to 7% higher than that in the (N-1)th hydrodewaxing catalyst; the packing volume ratio of the Nth hydrodewaxing catalyst to the (N-1)th hydrodewaxing catalyst is 1:0.5 to 1:5.

0.

17. The method according to claim 15, characterized in that: The carbon content in the Nth hydrodewaxing catalyst is 1% to 5% higher than that in the N-1th hydrodewaxing catalyst.

18. The method according to claim 1, characterized in that: The hydrogen dewaxing catalyst packed in the hydrogen dewaxing reaction zone has the same or different contents of Y molecular sieve, β molecular sieve, and active metals for hydrogenation of Group VIB and / or Group VIII metals, based on the weight of carbon removed.

19. The method according to claim 1, characterized in that: The hydrodewaxing catalyst packed in the hydrodewaxing reaction zone is obtained by one of the following methods: Method 1: First, prepare or select a hydrogenation dewaxing catalyst containing Y molecular sieve, β molecular sieve, Group VIB and / or Group VIII metal hydrogenation active metal; then perform carbon deposition treatment at different depths to obtain hydrogenation dewaxing catalysts with different carbon contents. Method 2: Perform carbon removal and regeneration treatments of different depths on the nascent hydrodewaxing catalyst containing Y molecular sieve, β molecular sieve, Group VIB and / or Group VIII metal hydrogenation active metal to obtain hydrodewaxing catalysts with different carbon contents.

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