Process for producing transformer oil by hydrocracking catalyst grading

Abstract

The present application belongs to the technical field of hydrocracking, and particularly relates to a hydrocracking catalyst and a method for producing transformer oil by grading the hydrocracking catalyst. The method for producing transformer oil by grading the hydrocracking catalyst comprises the following steps: after raw oil is mixed with hydrogen, the mixture enters a hydrofining reaction zone and reacts with a hydrofining catalyst; hydrofining reaction effluent successively enters first and second hydrocracking reaction zones for catalysis and reaction; and the second hydrocracking reaction zone effluent is separated to obtain light naphtha, heavy naphtha, diesel oil and tail oil components, wherein the diesel oil is directly used as transformer oil. The method for producing transformer oil by grading the hydrocracking catalyst can produce qualified transformer oil products with high density, and by-products of high-quality heavy naphtha and tail oil, and has high economic benefits.

Description

Technical Field

[0001] This invention belongs to the technical field of petrochemicals, specifically relating to a method for producing transformer oil by grading hydrocracking catalysts. Background Technology

[0002] Currently, the demand for transformer oil is increasing, with naphthenic transformer oil being the primary type. Furthermore, regulations stipulate that transformer oil must be refined from naphthenic crude oil. Naphthenic transformer oil has a lower pour point and does not require dewaxing; however, naphthenic crude oil reserves are scarce, accounting for only 2% of total crude oil reserves, insufficient to meet the demand. In recent years, hydrocracking has become the mainstream technology for transformer oil production; however, hydrocracking transformer oil quality is lacking, requiring in-depth research into catalyst systems to directly produce qualified transformer oil products.

[0003] Hydrocracking diesel fuel shares similarities with transformer oil in terms of distillation range, density, and other properties. However, conventional hydrocracking diesel fuel fails to meet requirements in terms of pour point and stability. Furthermore, transformer oil produced using existing technologies suffers from low density, low price, and poor economic viability. Therefore, developing a hydrocracking catalyst system that lowers the pour point and aromatic content of diesel fuel is of great significance for meeting the enormous demand for transformer oil products and improving the economic efficiency of enterprises.

[0004] CN114149828A discloses a No. 5 industrial white oil and its preparation method. The preparation method of this invention uses hydrocracked diesel fraction as raw material, and removes light components from the diesel fraction through hydrocracking, hydrodearomatization, and stripping steps to obtain No. 5 industrial white oil. The preparation method of this invention can effectively control the pour point and aromatic content of No. 5 Class I industrial white oil, ensuring that all properties of the prepared No. 5 Class I industrial white oil meet quality requirements. Since transformer oil requires a pour point of less than -10℃, this method cannot utilize hydrocracked diesel oil to produce transformer oil components.

[0005] CN113969180A discloses a low-pressure hydrodearomatization method for hydrocracking diesel fractions, comprising the following steps: using a fixed-bed hydrotreating unit as a reactor, employing a nickel-reduced catalyst, introducing hydrogen gas, and performing a hydrotreating reaction on the hydrocracking diesel fraction at a hydrogen partial pressure of 1-3 MPa. After aromatic saturation, a dearomatized product is obtained. This invention uses the above process conditions to perform a hydrotreating reaction on hydrocracking diesel fractions, resulting in low operating pressure, low equipment requirements, and low operational risks; it also achieves good dearomatization effects on hydrocracking diesel fractions, meeting the dearomatization requirements for producing No. 5 Class I industrial white oil from hydrocracking diesel fractions. However, this method only reduces the aromatic content in diesel fuel and cannot lower the pour point of diesel fuel, thus still failing to meet the requirements for transformer oil specifications. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for producing transformer oil by hydrocracking catalyst gradation. This method can not only produce qualified transformer oil products with high density, but also produce high-quality heavy naphtha and tail oil products as by-products, resulting in high economic benefits.

[0007] The method for producing transformer oil by hydrocracking catalyst gradation according to the present invention includes the following steps:

[0008] (1) After the feedstock oil is mixed with hydrogen, it enters the hydrorefining reaction zone and undergoes denitrification, dearomatization and other impurity removal reactions with the hydrorefining catalyst;

[0009] (2) The effluent from the hydrorefining reaction enters the first hydrocracking reaction zone and the second hydrocracking reaction zone in sequence for catalysis, where aromatic ring opening, alkane cracking, and isomerization reactions occur; the packing volume ratio of the catalysts in the first hydrocracking reaction zone to the second hydrocracking reaction zone is 3:1 to 1:1.

[0010] (3) The effluent from the second reaction zone of hydrocracking is separated by a separation system to obtain light naphtha, heavy naphtha, diesel oil and tail oil components, of which diesel oil is directly used as transformer oil.

[0011] The feedstock oil is straight-run wax oil or a mixture of straight-run wax oil and coking wax oil; the initial boiling point of the mixture of straight-run wax oil and coking wax oil is 260–350℃, the final boiling point is 480–600℃, and the density is 0.87–0.93 g / cm³. 3 .

[0012] The hydrorefining catalyst in step (1) is one or more of FF-36, FF-46, FF-56, FF-66, and FTX (developed by Dalian Petrochemical Research Institute of China Petroleum & Chemical Corporation).

[0013] The catalysts packed in the first reaction zone of hydrocracking in step (2) are catalyst a and catalyst b in a mass ratio of 20:1 to 5:1, wherein catalyst a and catalyst b are mixed mechanically.

[0014] Catalyst a is based on the weight of catalyst a, with 40-60 wt.% alumina support, 20-40 wt.% Y molecular sieve, and 13-28 wt.% active metal as oxides; of which the active metal has a nickel mass fraction of 3-8 wt.% as NiO and a molybdenum mass fraction of 10-25 wt.% as MoO3.

[0015] The preparation method of catalyst a is as follows: after mechanically mixing Y molecular sieve with alumina, a binder is added and fully rolled into shape, and then dried at 70-110℃ to obtain a catalyst support; the catalyst support is impregnated with a solution containing nickel and molybdenum active metal components, wherein the impregnation method can be equal volume impregnation, excess volume impregnation or steam impregnation, preferably equal volume impregnation, and after drying at 80-120℃ and calcining at 300-600℃, catalyst a is obtained.

[0016] Based on the weight of catalyst b, the alumina support is 45-65 wt.%, the SAPO-11 molecular sieve is 20-40 wt.%, and the active metal content (calculated as oxide) is 13-30 wt., of which the active metal (calculated as CoO) has a cobalt mass fraction of 3-10 wt.% and a molybdenum mass fraction (calculated as MoO3) of 10-20 wt.%.

[0017] The preparation method of catalyst b is as follows: SAPO-11 molecular sieve and alumina are mechanically mixed, a binder is added and fully rolled and shaped, and then dried at 70-110℃ to obtain a catalyst support; the catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components, wherein the impregnation method can be equal volume impregnation, excess volume impregnation or steam impregnation, preferably equal volume impregnation, and then dried at 70-120℃ and calcined at 400-600℃ to obtain catalyst b.

[0018] The catalysts packed in the second reaction zone of hydrocracking in step (2) are catalyst c and catalyst d packed in a mass ratio of 0.01:1 to 0.2:1.

[0019] Catalyst c is based on the weight of catalyst c, with alumina support of 60-75 wt.%, Y molecular sieve of 10-20 wt.%, and active metal content of 15-25 wt.% as oxides; among which, the active metal has a nickel mass fraction of 3-8 wt.% as NiO and a molybdenum mass fraction of 10-20 wt.% as MoO3.

[0020] The catalyst c is prepared by mechanically mixing Y molecular sieve with alumina, adding binder and fully rolling it into shape, and then drying it at 80-120℃ to obtain a catalyst support; impregnating the catalyst support with a solution containing nickel and molybdenum active metal components, wherein the impregnation method can be equal volume impregnation, excess volume impregnation or steam impregnation, preferably equal volume impregnation, and then drying it at 70-110℃ and calcining it at 350-600℃ to obtain catalyst c.

[0021] Catalyst d is based on the weight of catalyst d, with 50-65 wt.% alumina support, 10-30 wt.% Beta molecular sieve, and 15-30 wt.% active metal as oxide, of which the mass fraction of cobalt as CoO is 3-10 wt.% and the mass fraction of molybdenum as MoO3 is 12-20 wt.%.

[0022] The catalyst d is prepared by mechanically mixing Beta molecular sieve and alumina, adding binder, fully rolling and molding, and then drying at 80-120°C to obtain a catalyst support; impregnating the catalyst support with a solution containing cobalt and molybdenum active metal components, wherein the impregnation method can be equal volume impregnation, excess volume impregnation or steam impregnation, preferably equal volume impregnation, and then drying at 80-120°C and calcining at 400-600°C to obtain catalyst d.

[0023] The reaction pressure of the hydrorefining reaction in step (1) is 12.0–18.0 MPa, preferably 13.0–16.0 MPa; the reaction temperature is 320–450 °C, preferably 340–400 °C; and the volume hourly space velocity is 0.5–3.0 h⁻¹. -1 Preferably 1.0 to 1.5 hours -1 The reaction pressure in the hydrocracking reaction zone of step (2) is 12.0–18.0 MPa, preferably 13.0–16.0 MPa; the reaction temperature is 320–420 °C, preferably 350–380 °C; and the volume hourly space velocity is 0.5–3.0 h⁻¹. -1 Preferably 1.0 to 2.5 hours -1 .

[0024] This invention involves loading composite hydrocracking catalysts with different active metals and molecular sieve supports into the first and second hydrocracking reaction zones, respectively. The first hydrocracking reaction zone has a high content of polycyclic aromatic hydrocarbons (PAHs) and long-chain alkanes. Y-type molecular sieves are used to enhance the ring-opening cracking reaction of aromatics, while SAPO-11 molecular sieves are combined to moderately crack and isomerize long-chain alkanes, thereby reducing the reaction temperature and cracking pressure in the lower bed. The composite hydrocracking catalyst used in the first hydrocracking reaction zone includes a support and an active metal, with a high proportion of Y-type molecular sieves, which can promote the ring-opening cracking reaction of PAHs and reduce the aromatic content in transformer oil.

[0025] The catalyst used in this invention in the second reaction zone of hydrocracking has a high proportion of Beta molecular sieves, which can promote alkane isomerization reactions and lower the pour point of transformer oil. The second reaction zone of hydrocracking has a high alkane content; using Beta molecular sieves to enhance alkane isomerization reactions and lower the pour point of diesel oil, and combining it with a small amount of Y molecular sieves to moderately crack monocyclic long-chain aromatics, further reduces the aromatic content in diesel oil and improves stability. The hydrocracking catalyst prepared by this invention can be used in any hydrocracking process and in any hydrogenation field, and can produce qualified transformer oil.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) The method for producing transformer oil by grading hydrocracking catalysts of the present invention uses hydrocracking catalysts with different characteristics according to the hydrocarbon molecule reaction characteristics of different molecular sieves and active metals and the hydrocarbon molecule reaction rules of the hydrocracking reaction zone. This can significantly reduce the polycyclic aromatic hydrocarbon content and pour point in diesel oil and directly produce qualified transformer oil products.

[0028] (2) The method for producing transformer oil by hydrocracking catalyst gradation of the present invention adopts catalyst gradation method, which significantly reduces the average reaction temperature of hydrocracking and achieves a stable temperature transition, effectively extending the operation cycle of the unit and reducing the energy consumption of the unit.

[0029] (3) The method for producing transformer oil by hydrocracking catalyst gradation of the present invention is simple, practical and flexible in operation. The yield and properties of transformer oil can be flexibly adjusted by simply changing the reaction temperature of the hydrocracking reaction zone according to the requirements of the raw material oil and the properties of the product. Detailed Implementation

[0030] The method provided by the present invention will be further described below with reference to the embodiments, but this does not limit the present invention.

[0031] The feedstock oils used in the following examples and comparative examples were straight-run wax oils, and their properties are shown in Table 1. Both the examples and comparative examples were evaluated for 2500 hours under the conditions in Table 3 to compare the properties of the transformer oils produced under different catalyst systems. The evaluation results for the examples are shown in Table 4, and the evaluation results for the comparative examples are shown in Table 5. The properties of FF-66, FC-32, and FC-14 used in the following examples and comparative examples are shown in Table 2.

[0032] In this invention, unless otherwise specified, percentages refer to mass fractions.

[0033] Example 1

[0034] The method for producing transformer oil by hydrocracking catalyst gradation includes the following steps:

[0035] (1) After the feedstock oil is mixed with hydrogen, it enters the hydrorefining reaction zone and undergoes denitrification, dearomatization and other impurity removal reactions with the hydrorefining catalyst; the hydrogen refining reaction zone is filled with industrial FF-66 hydrorefining catalyst.

[0036] (2) The effluent from the hydrorefining reaction enters the first hydrocracking reaction zone and the second hydrocracking reaction zone in sequence for catalysis, where aromatic ring opening, alkane cracking, and isomerization reactions occur; the packing volume ratio of the catalysts in the first hydrocracking reaction zone to the second hydrocracking reaction zone is 3:1.

[0037] The mass ratio of catalyst a to catalyst b in the first reaction zone of hydrocracking is 20:1.

[0038] Preparation method of catalyst a: 20% Y molecular sieve and 60% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 3% and the mass fraction of molybdenum (calculated as MoO3) is 17%. After drying at 80°C and calcining at 420°C, hydrocracking catalyst a is obtained.

[0039] Preparation method of catalyst b: 20% SAPO-11 molecular sieve and 65% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 100°C to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 3% and the mass fraction of molybdenum (calculated as MoO3) is 12%. After drying at 80°C and calcining at 450°C, hydrocracking catalyst b is obtained.

[0040] The mass ratio of catalyst c to catalyst d in the second reaction zone of hydrocracking is 0.01:1.

[0041] Preparation method of catalyst c: 10% Y molecular sieve and 75% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 3% and the mass fraction of molybdenum (calculated as MoO3) is 12%. After drying at 80°C and calcining at 420°C, hydrocracking catalyst c is obtained.

[0042] Preparation method of catalyst d: 10% Beta molecular sieve and 65% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. The mixture is then dried at 100°C to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 20 wt.%. After drying at 100°C and calcining at 450°C, hydrocracking catalyst d is obtained.

[0043] (3) The effluent from the second reaction zone of hydrocracking is separated by a separation system to obtain light naphtha, heavy naphtha, diesel oil and tail oil components, of which diesel oil is directly used as transformer oil.

[0044] Example 2

[0045] The method for producing transformer oil using hydrocracking catalyst gradation includes the following steps: 20:1

[0046] (1) After the feedstock oil is mixed with hydrogen, it enters the hydrorefining reaction zone and undergoes denitrification, dearomatization and other impurity removal reactions with the hydrorefining catalyst; the hydrogen refining reaction zone is filled with industrial FF-66 hydrorefining catalyst.

[0047] (2) The effluent from the hydrorefining reaction enters the first hydrocracking reaction zone and the second hydrocracking reaction zone in sequence for catalysis, where aromatic ring opening, alkane cracking, and isomerization reactions occur; the packing volume ratio of the catalysts in the first hydrocracking reaction zone and the second hydrocracking reaction zone is 1:1.

[0048] The mass ratio of catalyst a to catalyst b in the first reaction zone of hydrocracking is 5:1.

[0049] Preparation method of catalyst a: 40% Y molecular sieve and 40% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 8% and the mass fraction of molybdenum (calculated as MoO3) is 12 wt.%. After drying at 70°C and calcining at 400°C, hydrocracking catalyst a is obtained.

[0050] Preparation method of catalyst b: 40% SAPO-11 molecular sieve and 45% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 100°C to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 10%. After drying at 80°C and calcining at 400°C, hydrocracking catalyst b is obtained.

[0051] The mass ratio of catalyst c to catalyst d in the second reaction zone of hydrocracking is 0.2:1.

[0052] Preparation method of catalyst c: 20% Y molecular sieve and 60% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 8% and the mass fraction of molybdenum (calculated as MoO3) is 12%. After drying at 80°C and calcining at 450°C, hydrocracking catalyst c is obtained.

[0053] Preparation method of catalyst d: 30% Beta molecular sieve and 50% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 100°C to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 8% and the mass fraction of molybdenum (calculated as MoO3) is 12%. After drying at 100°C and calcining at 450°C, hydrocracking catalyst d is obtained.

[0054] (3) The effluent from the second reaction zone of hydrocracking is separated by a separation system to obtain light naphtha, heavy naphtha, diesel oil and tail oil components, of which diesel oil is directly used as transformer oil.

[0055] Example 3

[0056] The method for producing transformer oil by hydrocracking catalyst gradation includes the following steps:

[0057] (1) After the feedstock oil is mixed with hydrogen, it enters the hydrorefining reaction zone and undergoes denitrification, dearomatization and other impurity removal reactions with the hydrorefining catalyst; the hydrogen refining reaction zone is filled with industrial FF-66 hydrorefining catalyst.

[0058] (2) The effluent from the hydrorefining reaction enters the first hydrocracking reaction zone and the second hydrocracking reaction zone in sequence for catalysis, where aromatic ring opening, alkane cracking, and isomerization reactions occur; the packing volume ratio of the catalysts in the first hydrocracking reaction zone to the second hydrocracking reaction zone is 2:1.

[0059] The mass ratio of catalyst a to catalyst b in the first reaction zone of hydrocracking is 10:1.

[0060] Preparation method of catalyst a: 25% Y molecular sieve and 60% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 10%. After drying at 80°C and calcining at 410°C, hydrocracking catalyst a is obtained.

[0061] Preparation method of catalyst b: 30% SAPO-11 molecular sieve and 45% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 100°C to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 20%. After drying at 80°C and calcining at 450°C, hydrocracking catalyst b is obtained.

[0062] In the second reaction zone of hydrocracking, the mass ratio of catalyst c to catalyst d is 0.1:1.

[0063] Preparation method of catalyst c: 15% Y molecular sieve and 60% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 20%. After drying at 80°C and calcining at 450°C, hydrocracking catalyst c is obtained.

[0064] Preparation method of catalyst d: 20% Beta molecular sieve and 57% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 100°C to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 3% and the mass fraction of molybdenum (calculated as MoO3) is 20%. After drying at 100°C and calcining at 450°C, hydrocracking catalyst d is obtained.

[0065] (3) The effluent from the second reaction zone of hydrocracking is separated by a separation system to obtain light naphtha, heavy naphtha, diesel oil and tail oil components, of which diesel oil is directly used as transformer oil.

[0066] Example 4

[0067] The method for producing transformer oil by hydrocracking catalyst gradation includes the following steps:

[0068] (1) After the feedstock oil is mixed with hydrogen, it enters the hydrorefining reaction zone and undergoes denitrification, dearomatization and other impurity removal reactions with the hydrorefining catalyst; the hydrogen refining reaction zone is filled with industrial FF-66 hydrorefining catalyst.

[0069] (2) The effluent from the hydrorefining reaction enters the first hydrocracking reaction zone and the second hydrocracking reaction zone in sequence for catalysis, where aromatic ring opening, alkane cracking, and isomerization reactions occur; the packing volume ratio of the catalysts in the first hydrocracking reaction zone to the second hydrocracking reaction zone is 3:1.

[0070] The mass ratio of catalyst a to catalyst b in the first reaction zone of hydrocracking is 15:1.

[0071] Preparation method of catalyst a: 22% Y molecular sieve and 50% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. The mixture is then dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 3% and the mass fraction of molybdenum (calculated as MoO3) is 25%. After drying at 100°C and calcining at 480°C, hydrocracking catalyst a is obtained.

[0072] Preparation method of catalyst b: 22% SAPO-11 molecular sieve and 53% alumina were mechanically mixed, and then a binder was added and fully rolled and shaped. The mixture was then dried at 100°C to obtain a catalyst support. The catalyst support was impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals were impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) was 10% and the mass fraction of molybdenum (calculated as MoO3) was 15%. After drying at 100°C and calcining at 500°C, hydrocracking catalyst b was obtained.

[0073] The mass ratio of catalyst c to catalyst d in the second reaction zone of hydrocracking is 0.05:1.

[0074] Preparation method of catalyst c: 18% Y molecular sieve and 66% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. The mixture is then dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 6% and the mass fraction of molybdenum (calculated as MoO3) is 10%. After drying at 70°C and calcining at 500°C, hydrocracking catalyst c is obtained.

[0075] Preparation method of catalyst d: 22% Beta molecular sieve and 53% alumina were mechanically mixed, and then a binder was added and fully rolled into shape. The mixture was then dried at 100°C to obtain a catalyst support. The catalyst support was impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals were impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) was 10% and the mass fraction of molybdenum (calculated as MoO3) was 15%. After drying at 100°C and calcining at 4800°C, hydrocracking catalyst d was obtained.

[0076] (3) The effluent from the second reaction zone of hydrocracking is separated by a separation system to obtain light naphtha, heavy naphtha, diesel oil and tail oil components, of which diesel oil is directly used as transformer oil.

[0077] Example 5

[0078] The method for producing transformer oil by hydrocracking catalyst gradation includes the following steps:

[0079] (1) After the feedstock oil is mixed with hydrogen, it enters the hydrorefining reaction zone and undergoes denitrification, dearomatization and other impurity removal reactions with the hydrorefining catalyst; the hydrogen refining reaction zone is filled with industrial FF-66 hydrorefining catalyst.

[0080] (2) The effluent from the hydrorefining reaction enters the first hydrocracking reaction zone and the second hydrocracking reaction zone in sequence for catalysis, where aromatic ring opening, alkane cracking, and isomerization reactions occur; the packing volume ratio of the catalysts in the first hydrocracking reaction zone to the second hydrocracking reaction zone is 3:2.

[0081] The mass ratio of catalyst a to catalyst b in the first reaction zone of hydrocracking is 12:1.

[0082] Preparation method of catalyst a: 25% Y molecular sieve and 50% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 20%. After drying at 80°C and calcining at 460°C, hydrocracking catalyst a is obtained.

[0083] Preparation method of catalyst b: 30% SAPO-11 molecular sieve and 50% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 110℃ to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 15%. After drying at 100℃ and calcining at 450℃, hydrocracking catalyst b is obtained.

[0084] The mass ratio of catalyst c to catalyst d in the second reaction zone of hydrocracking is 0.08:1.

[0085] Preparation method of catalyst c: 17% Y molecular sieve and 60% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. Then, the mixture is dried at 80°C to obtain a catalyst support. Nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as NiO) is 5% and the mass fraction of molybdenum (calculated as MoO3) is 18%. After drying at 80°C and calcining at 450°C, hydrocracking catalyst c is obtained.

[0086] Preparation method of catalyst d: 20% Beta molecular sieve and 55% alumina are mechanically mixed, and then a binder is added and fully rolled and shaped. The mixture is then dried at 100°C to obtain a catalyst support. The catalyst support is impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals are impregnated by an equal volume impregnation method, wherein the mass fraction of nickel (calculated as CoO) is 8% and the mass fraction of molybdenum (calculated as MoO3) is 17%. After drying at 100°C and calcining at 500°C, hydrocracking catalyst d is obtained.

[0087] (3) The effluent from the second reaction zone of hydrocracking is separated by a separation system to obtain light naphtha, heavy naphtha, diesel oil and tail oil components, of which diesel oil is directly used as transformer oil.

[0088] Comparative Example 1

[0089] The industrial FF-66 hydrorefining catalyst was loaded into the hydrorefining reactor, and the FC-14 hydrocracking catalyst developed by the Dalian Petrochemical Research Institute of China Petroleum & Chemical Corporation was loaded into the hydrocracking reactor. A 2500-hour process evaluation experiment was conducted according to the conditions in Table 3.

[0090] Comparative Example 2

[0091] The industrial FF-66 hydrorefining catalyst was loaded into the hydrorefining reactor, and the FC-32 hydrocracking catalyst developed by the Dalian Petrochemical Research Institute of China Petroleum & Chemical Corporation was loaded into the hydrocracking reactor. A 2500-hour process evaluation experiment was conducted according to the conditions in Table 3.

[0092] Comparative Example 3

[0093] The industrial FF-66 hydrorefining catalyst was loaded into the hydrorefining reactor. The FC-14 and FC-32 hydrocracking catalysts developed by Dalian Petrochemical Research Institute of China Petroleum & Chemical Corporation were loaded into the hydrocracking reactor in equal volumes, and a 2500-hour process evaluation experiment was conducted according to the conditions in Table 3.

[0094] Table 1 Properties of Crude Oil

[0095] Testing items Testing standards Test results <![CDATA[Density (20 °C) / g·cm -3 > GB / T 1884 0.9130 Distillation range / ℃ ASTM D1160 260～540 S / ％ ASTM D5762-95 1.85 <![CDATA[N / μg·g -1 ]]> ASTM D5762-95 657 Aromatics / wt.% SH / T 0606 36.6

[0096] Table 2 Properties of Industrial Catalysts

[0097] Physical and chemical properties FF-66 FC-32 FC-14 Metal type Co-Mo Ni-Mo Ni-W Aperture / nm 2~10nm 2-8nm 3~10nm <![CDATA[Pore volume / mL·g -1 > ≥0.25 ≥0.25 ≥0.32 <![CDATA[Specific surface area / m 2 ·g -1 > ≥180 ≥350 ≥320 shape Gear ball cylindrical bar cylindrical bar <![CDATA[Loading heap ratio, g / cm 3 > 0.76 0.70 0.87

[0098] Table 3 Evaluation Criteria

[0099] Reaction pressure, MPa 14.7 <![CDATA[The space velocity of the first hydrofining reaction zone, h -1 > 1.0 <![CDATA[The catalyst hourly space velocity in the hydrocracking reaction zone, h -1 > 1.5 Nitrogen content of refined oil, ppm 10 Residual oil yield, % 25 Runtime, h 2500

[0100] Table 4. Test Results of Examples

[0101]

[0102] Table 5. Results of the comparative experiment

[0103] Transformer oil properties at 275–360℃ Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Density, g / cm 3 > 0.8456 0.8465 0.8414 Polycyclic aromatic hydrocarbon content, wt.% 2.6 2.4 2.3 Pour point, ℃ -5 -7 -6 Sieves colorimetry 22 21 23 Hydrogen consumption, wt.% 2.87 2.86 2.90 Cracking catalyst deactivation rate, °C / day 0.005 0.005 0.006

[0104] The experimental results from the comparative examples and embodiments show that, under the controlled-phase process, the hydrocracking method of the present invention not only meets the requirements for density, polycyclic aromatic hydrocarbon content, pour point, and color of the produced transformer oil, but also exhibits low hydrogen consumption and low deactivation rate of the hydrocracking catalyst system. When using the catalyst gradation system under the conditions of Example 5, the produced transformer oil with a temperature range of 275–360°C has the lowest pour point of -15°C, the lowest hydrogen consumption of 2.43 wt.%, and the lowest deactivation rate of the hydrocracking catalyst system of 0.001°C / day.

[0105] Of course, the above description is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is also not limited to the above examples, and all equivalent changes and improvements made by those skilled in the art within the scope of the present invention should fall within the patent coverage of the present invention.

Claims

1. A method for producing transformer oil by hydrocracking catalyst gradation, characterized in that: Includes the following steps: (1) After the feedstock oil is mixed with hydrogen, it enters the hydrorefining reaction zone and undergoes denitrification and dearomatization reactions with the hydrorefining catalyst; the feedstock oil is straight-run wax oil or a mixture of straight-run wax oil and coking wax oil; (2) The hydrorefining reaction effluent enters the first and second hydrocracking reaction zones in sequence, where aromatic ring opening, alkane cracking, and isomerization reactions occur; the packing volume ratio of the catalyst in the first and second hydrocracking reaction zones is 3:1 to 1:

1. The catalysts packed in the first reaction zone are catalysts a and b in a mass ratio of 20:1 to 5:

1. Catalyst a, based on its weight, contains 40–60 wt% alumina support, 20–40 wt% Y molecular sieve, and 13–28 wt% active metal as oxides; of which the active metals include 3–8 wt% nickel (calculated as NiO) and 10–25 wt% molybdenum (calculated as MoO3). Catalyst b, based on its weight, contains 45–65 wt% alumina support, 20–40 wt% SAPO-11 molecular sieve, and 13–30 wt% active metal as oxides; of which the active metals include 3–10 wt% cobalt (calculated as CoO) and 10–20 wt% molybdenum (calculated as MoO3). The second reaction zone is filled with catalysts c and d in a mass ratio of 0.01:1 to 0.2:

1. Catalyst c, based on its weight, contains 60-75 wt% alumina support, 10-20 wt% Y molecular sieve, and 15-25 wt% active metal as oxides; of which the active metal contains 3-8 wt% nickel as NiO and 10-20 wt% molybdenum as MoO3. Catalyst d, based on its weight, contains 50-65 wt% alumina support, 10-30 wt% Beta molecular sieve, and 15-30 wt% active metal as oxides; of which the active metal contains 3-10 wt% cobalt as CoO and 12-20 wt% molybdenum as MoO3. (3) The effluent from the second reaction zone of hydrocracking is separated into light naphtha, heavy naphtha, diesel oil and tail oil components, of which diesel oil is directly used as transformer oil.

2. The method for producing transformer oil by hydrocracking catalyst gradation according to claim 1, characterized in that: The crude oil has an initial boiling point of 260-350℃, a final boiling point of 480-600℃, and a density of 0.87-0.93 g / cm³. 3 .

3. The method for producing transformer oil by hydrocracking catalyst gradation according to claim 1, characterized in that: The hydrorefining catalyst in step (1) is one or more of FF-36, FF-46, FF-56, FF-66, and FTX.

4. The method for producing transformer oil by hydrocracking catalyst gradation according to claim 1, characterized in that: The reaction pressure of the hydrogenation refining reaction in step (1) is 12.0–18.0 MPa, the reaction temperature is 320–450 °C, and the volume hourly space velocity is 0.5–3.0 h⁻¹. -1 In step (2), the reaction pressure in the hydrocracking reaction zone is 12.0–18.0 MPa, the reaction temperature is 320–420 °C, and the volume hourly space velocity is 0.5–3.0 h⁻¹. -1 .

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