A hydrocracking method for producing transformer oil

Abstract

The present invention is applicable to the field of hydrocracking technology and provides a hydrocracking method for producing transformer oil and a catalyst used therein. The hydrocracking method comprises the following steps: Step 1: the feedstock oil is mixed with hydrogen and then enters a hydrorefining reaction zone to contact with a hydrorefining catalyst to undergo desulfurization, denitrogenation, dearomatization, demetallization, and other impurity removal reactions; Step 2: the hydrorefining reaction effluent enters a hydrocracking reaction zone to contact with a hydrocracking catalyst to undergo aromatic ring opening and paraffin isomerization reactions; Step 3: the hydrocracking reaction effluent passes through a separation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha, transformer oil, and tail oil products. Thus, the present invention can achieve maximum hydrogenation saturation of aromatics, significantly reduce the aromatic content in the hydrocracking product, and solve the problem of balancing aromatic ring opening capacity and paraffin isomerization capacity, thereby producing high-quality transformer oil.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrocracking, in particular to a hydrocracking method for producing transformer oil. Background Art

[0002] Transformer oil is a petroleum fractionation product. Its primary components are alkanes, cycloalkanes, and aromatic unsaturated hydrocarbons. Commonly known as square shed oil, it is a light yellow, transparent liquid. Transformer oil is a mineral oil obtained through distillation and refining of natural petroleum. It is a mixture of natural hydrocarbons, obtained through acid and alkali refining of the lubricating oil fraction of petroleum, resulting in a pure, stable, low-viscosity, and excellent insulating and cooling properties. Transformer oil's functions include: dissipating heat and cooling during operation; insulating and maintaining windings; and extinguishing arcs at high-voltage leads and tap-changer contacts, preventing corona and arc discharges.

[0003] Hydrocracking diesel products can be used as transformer oil products. Transformer oil requires low aromatic and high isoparaffin content. Conventional hydrocracking catalysts often use a single molecular sieve component, which makes it difficult to take into account both the ring opening of aromatics and the isomerization of paraffins. The transformer oil produced will face the problem of excessively high aromatic content or pour point.

[0004] Therefore, it is of great significance to develop a hydrocracking catalyst that takes into account both the ring-opening of aromatics and the isomerization ability of paraffins, so as to simultaneously reduce the content of aromatics and normal paraffins in the transformer oil components produced by hydrocracking, thereby producing qualified transformer oil products.

[0005] CN109794273A discloses a hydroprocessing catalyst, its preparation method, and a method for preparing a transformer oil base oil. This invention discloses a hydroprocessing catalyst comprising an SB powder carrier and Al, Si, B, P, a Group VIB metal element, and a Group VIII metal element supported on the carrier. The catalyst can be used to catalyze the preparation of a special transformer oil base oil that offers both oxidative stability and gassing properties and is free of inhibitors. However, this method has poor adaptability to the feedstock oil and cannot produce high-specification transformer oil.

[0006] CN108893182A discloses a non-cycloalkyl high-overload transformer oil base oil and its preparation method. This invention fractionates the non-cycloalkyl base oil to an initial boiling point of 290±5°C and a final boiling point of 420±5°C, thereby obtaining the non-cycloalkyl high-overload transformer oil base oil. The non-cycloalkyl base oil is fractionated and cut to remove light and heavy components, resulting in a base oil with an initial boiling point of 290±5°C and a final boiling point of 420±5°C. This base oil has advantages such as a high closed-cup flash point, low kinematic viscosity, and low density. However, this method requires complex distillation ranges for the feedstock, resulting in high costs and low yields.

[0007] Transformer oil requires low aromatic content and pour point. Existing catalyst systems are difficult to meet the requirements of aromatic ring opening while taking into account the isomerization reaction of paraffins, thereby achieving the purpose of reducing transformer oil aromatic content and pour point.

[0008] In summary, the existing technology has obvious inconveniences and defects in actual use, so it is necessary to improve it. Summary of the Invention

[0009] In view of the above-mentioned drawbacks, the object of the present invention is to provide a hydrocracking method for producing transformer oil and a catalyst therefor, which can achieve maximum hydrogenation saturation of aromatics, significantly reduce the aromatic content in the hydrocracking product, and solve the difficult problem of balancing the ring-opening ability of aromatics and the isomerization ability of paraffins, and produce high-quality transformer oil.

[0010] In order to achieve the above object, the present invention provides a hydrocracking method for producing transformer oil, comprising the following steps:

[0011] In step 1, the feedstock oil is mixed with hydrogen and then enters the hydrorefining reaction zone to contact and react with the hydrorefining catalyst. In step 2, the effluent from the hydrorefining reaction enters the hydrocracking reaction zone to contact and react with the hydrocracking catalyst. In step 3, the effluent from the hydrocracking reaction passes through a separation system to obtain a product.

[0012] The hydrorefining reaction zone described in step one is graded and loaded with two hydrorefining catalysts, the upper part of the reaction zone is loaded with a cobalt-molybdenum type hydrorefining catalyst, and the lower part of the reaction zone is loaded with a nickel-molybdenum type hydrorefining catalyst; according to the differences in the structure and composition of the aromatics in the hydrorefining reaction zone, a hydrorefining catalyst with a strong directional saturation ability of aromatics is matched and used, thereby achieving maximum hydrogenation saturation of aromatics and significantly reducing the aromatics content in the hydrocracking product.

[0013] The hydrocracking catalyst in step 2 comprises a carrier and an active metal. The hydrocracking catalyst is prepared using Y molecular sieve, ZSM-22 molecular sieve and alumina as carriers and Group VIII and Group VIB metals as active metal components.

[0014] According to a hydrocracking method for producing transformer oil of the present invention, the reaction pressure of the hydrorefining reaction zone in step 1 is 10.0-20.0 MPa, the hydrorefining reaction temperature is 320-420° C., and the volume space velocity is 0.3-3.0 h -1 In step 2, the reaction pressure of the hydrocracking reaction zone is 10.0 to 20.0 MPa, the hydrocracking reaction temperature is 340 to 450 ° C, and the volume space velocity is 0.5 to 3.0 h -1 .

[0015] According to a hydrocracking method for producing transformer oil of the present invention, the raw oil in step 1 is a mixture of straight-run wax oil and catalytic diesel, with an initial boiling point of 180-310°C, a final boiling point of 440-570°C, and a density of 0.89-0.93 g / cm 3 The blending ratio of catalytic diesel in the raw materials is 10% to 30%.

[0016] According to a hydrocracking method for producing transformer oil of the present invention, the preparation method of the hydrocracking catalyst is as follows:

[0017] After mechanically mixing Y molecular sieve and alumina, a binder is added and fully rolled to form, and then dried at 70-120°C for 3-10 hours to obtain a catalyst carrier; the catalyst carrier is impregnated with a solution containing nickel-molybdenum active metal components, and after the active metal is impregnated, the catalyst carrier is dried at 60-120°C for 3-10 hours and calcined at 350-550°C for 4-12 hours to obtain a first hydrocracking catalyst; nickel-molybdenum active metals with strong cyclic hydrocarbon ring-opening ability are loaded on the Y molecular sieve, thereby enhancing the ring-opening cracking reaction of aromatic hydrocarbons.

[0018] After mechanically mixing ZSM-22 molecular sieve with alumina, a binder is added and thoroughly rolled before forming the mixture. The mixture is then dried at 60-120°C for 3-10 hours to obtain a catalyst support. The catalyst support is then impregnated with a solution containing active metal components of cobalt and molybdenum. After impregnation with the active metal components, the catalyst support is dried at 60-120°C for 3-10 hours and calcined at 400-600°C for 4-12 hours to obtain a second hydrocracking catalyst. The cobalt and molybdenum active metals, which have a strong paraffin adsorption capacity, are loaded onto the ZSM-22 molecular sieve to reduce the effect of aromatics on the adsorption isomerization reaction of paraffins, thereby lowering the pour point of transformer oil.

[0019] The final composite hydrocracking catalyst is obtained by mechanically mixing the first hydrocracking catalyst and the second hydrocracking catalyst. The combination of the two can solve the problem of balancing the aromatic hydrocarbon ring-opening ability and the paraffin isomerization ability.

[0020] According to a hydrocracking method for producing transformer oil of the present invention, based on the weight of the first catalyst, the alumina carrier comprises 40-60wt%, the Y molecular sieve content comprises 25-40wt%, the active metal content in terms of oxides comprises 15-35wt%, wherein the mass fraction of nickel species in terms of NiO comprises 3-10wt%, and the mass fraction of molybdenum in terms of MoO3 comprises 12-25wt%; based on the weight of the second catalyst, the alumina carrier comprises 50-70wt%, the ZSM-22 molecular sieve content comprises 5-20wt%, the active metal content in terms of oxides comprises 10-30wt%, wherein the mass fraction of nickel species in terms of CoO comprises 2-10wt%, and the mass fraction of molybdenum in terms of MoO3 comprises 6-20wt%.

[0021] According to a hydrocracking method for producing transformer oil of the present invention, the mass mixing ratio of the first hydrocracking catalyst to the second hydrocracking catalyst is 5:(1-5).

[0022] According to a hydrocracking method for producing transformer oil of the present invention, the crystal form of alumina in the hydrocracking catalyst carrier includes one or more combinations of α-alumina, β-alumina, γ-alumina, δ-alumina, θ-alumina, and η-alumina.

[0023] According to the hydrocracking method for producing transformer oil of the present invention, the hydrocracking catalyst binder is derived from aluminum sol, sesbania powder and polyethylene glycol, and the amount of the binder added is 3-10 wt% of the carrier mass.

[0024] According to the hydrocracking method for producing transformer oil of the present invention, the impregnation method can be an equal volume impregnation method, an excess volume impregnation method, and a steam impregnation method.

[0025] According to the hydrocracking method for producing transformer oil of the present invention, in step 1, the volume filling ratio of the hydrorefining catalyst in the upper reaction zone to that in the lower reaction zone is 5:(1-15).

[0026] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0027] (1) The present invention uses a hydrotreating catalyst with strong aromatic directional saturation ability based on the differences in aromatic structure and composition in the hydrotreating reaction zone, thereby achieving maximum hydrogenation saturation of aromatics and significantly reducing the aromatic content in the hydrocracking product.

[0028] (2) The present invention loads nickel-molybdenum active metals, which have strong cyclic hydrocarbon ring-opening ability, onto Y molecular sieve, thereby enhancing the ring-opening cracking reaction of aromatic hydrocarbons. Furthermore, cobalt-molybdenum active metals, which have strong paraffin adsorption ability, onto ZSM-22 molecular sieve, thereby reducing the effect of aromatic hydrocarbons on paraffin adsorption isomerization reactions and lowering the pour point of transformer oil. The combination of these two metals solves the difficult problem of balancing aromatic hydrocarbon ring-opening ability with paraffin isomerization ability.

[0029] (3) The hydrogenation catalyst system prepared by the method of the present invention can achieve deep hydrogenation and efficient conversion of polycyclic aromatic hydrocarbons, and the transformer oil produced is of good quality. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] The present invention provides a hydrocracking method for producing transformer oil, comprising the following steps:

[0032] Step 1: After the crude oil is mixed with hydrogen, it enters the hydrorefining reaction zone and contacts with the hydrorefining catalyst to undergo desulfurization, denitrogenation, dearomatization, demetallization and other impurity removal reactions. The reaction pressure is 10.0-20.0 MPa, the hydrorefining reaction temperature is 320-420°C, and the volume space velocity is 0.3-3.0 h -1 ; The use of a hydrotreating catalyst with strong aromatic directional saturation ability achieves maximum hydrogenation saturation of aromatics and can significantly reduce the aromatic content in the hydrocracking product.

[0033] Step 2: The effluent from the hydrotreating reaction enters the hydrocracking reaction zone and contacts with the hydrocracking catalyst to cause aromatic ring opening and paraffin isomerization reaction. The reaction pressure is 10.0-20.0 MPa, the hydrocracking reaction temperature is 340-450°C, and the volume space velocity is 0.5-3.0 h -1 ;

[0034] Step 3: The hydrocracking reaction effluent passes through a separation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha, transformer oil and tail oil products.

[0035] The hydrocracking catalyst prepared by the present invention can be used in any hydrocracking process. In the hydrocracking process involved, the reaction conditions for refining and cracking are: reaction pressure 10.0-20.0 MPa, preferably 12.0-17.0 MPa; hydrofining reaction temperature 320-420°C, preferably 350-400°C; hydrofining volume space velocity 0.3-3.0 h -1 , preferably 0.5~1.0h -1 The hydrocracking reaction temperature is 340-450°C, preferably 370-390°C; the volume space velocity in the hydrocracking section is 0.5-3.0h -1 , preferably 1.0 to 2.0 hours -1 .

[0036] The raw material oil in step 1 is a mixture of straight-run wax oil and catalytic diesel, with an initial boiling point of 180-310°C, a final boiling point of 440-570°C, and a density of 0.89-0.93 g / cm 3 The blending ratio of catalytic diesel in the raw materials is 10% to 30%.

[0037] The hydrorefining reaction zone described in step 1 is loaded with two hydrorefining catalysts loaded with different active metals in a graded manner. The upper reaction zone is loaded with a cobalt-molybdenum hydrorefining catalyst with strong ability to saturate polycyclic aromatic hydrocarbons to monocyclic aromatic hydrocarbons, while the lower reaction zone is loaded with a nickel-molybdenum hydrorefining catalyst with strong ability to saturate monocyclic aromatic hydrocarbons. The volumetric loading ratio of the hydrorefining catalysts in the upper reaction zone to the lower reaction zone is 5:(1-15).

[0038] The cobalt-molybdenum catalyst in the upper part of the hydrotreating reaction zone involved in step 1 can use an industrial hydrotreating catalyst, such as FHUDS-5, FHUDS-7, FF-12, etc. developed by Sinopec Dalian Research Institute of Petrochemicals.

[0039] The nickel-molybdenum type hydrorefining catalyst loaded in the lower part of the hydrorefining reaction zone involved in step 1 is generally an industrial catalyst, such as FF-66, FHUDS-6, FHUDS-8 and other catalysts developed by Sinopec Dalian Research Institute of Petrochemicals.

[0040] A hydrocracking catalyst comprises a carrier and an active metal. The carrier comprises Y molecular sieve, ZSM-22 molecular sieve, and alumina, and the active metal components comprise Group VIII and Group VIB metals. The hydrocracking catalyst is prepared as follows:

[0041] After mechanically mixing Y molecular sieve with alumina, a binder is added and thoroughly rolled and formed, followed by drying at 70-120°C for 3-10 hours to obtain a catalyst support. The catalyst support is then impregnated with a solution containing nickel and molybdenum active metal components, where the impregnation method can be equal volume impregnation, excess volume impregnation, or steam impregnation, with equal volume impregnation being preferred. After impregnation with the active metal, the catalyst support is dried at 60-120°C for 3-10 hours and calcined at 350-550°C for 4-12 hours to obtain the first hydrocracking catalyst. The nickel and molybdenum active metals, which have strong cyclic hydrocarbon ring-opening capabilities, are loaded onto the Y molecular sieve, enhancing the ring-opening cracking reaction of aromatic hydrocarbons.

[0042] Based on the weight of the first catalyst, the alumina carrier is 40-60wt%, the Y molecular sieve content is 25-40wt%, and the active metal content in terms of oxide is 15-35wt%, of which the mass fraction of nickel species in terms of NiO is 3-10wt%, and the mass fraction of molybdenum in terms of MoO3 is 12-25wt%.

[0043] After mechanically mixing ZSM-22 molecular sieve with alumina, a binder is added and thoroughly rolled to form the mixture. The mixture is then dried at 60-120°C for 3-10 hours to obtain a catalyst support. The catalyst support is then impregnated with a solution containing active metal components, including cobalt and molybdenum. After impregnation with the active metal components, the catalyst support is dried at 60-120°C for 3-10 hours and calcined at 400-600°C for 4-12 hours to obtain the second hydrocracking catalyst. The cobalt and molybdenum active metal components, which have a strong alkane adsorption capacity, are loaded onto the ZSM-22 molecular sieve to reduce the effect of aromatics on the adsorption isomerization reaction of alkanes, thereby lowering the pour point of transformer oil.

[0044] Based on the weight of the second catalyst, the alumina carrier is 50-70wt%, the ZSM-22 molecular sieve content is 5-20wt%, and the content of the active metal in terms of oxide is 10-30wt%, of which the mass fraction of the nickel species in terms of CoO is 2-10wt%, and the mass fraction of molybdenum in terms of MoO3 is 6-20wt%.

[0045] Finally, the first hydrocracking catalyst and the second hydrocracking catalyst are mechanically mixed to form the final composite hydrocracking catalyst. The mass ratio of the first hydrocracking catalyst to the second hydrocracking catalyst is 5:(1-5). This combination of the two can overcome the difficult problem of balancing aromatic ring-opening capacity and paraffin isomerization capacity.

[0046] The impregnation method may be an equal volume impregnation method, an excess volume impregnation method, a steam impregnation method, etc., preferably an equal volume impregnation method.

[0047] Furthermore, the hydrocracking catalyst binder is derived from aluminum sol, sesbania powder, polyethylene glycol, etc. The amount of the binder added is 3-10 wt% of the carrier mass.

[0048] Furthermore, the hydrocracking catalyst carrier contains alumina, and the crystal form of the alumina includes at least one of α-alumina, β-alumina, γ-alumina, δ-alumina, θ-alumina, η-alumina, etc., preferably γ-alumina and / or η-alumina.

[0049] The hydrocracking method for producing transformer oil of the present invention can be used in any hydrogenation field and can produce qualified transformer oil.

[0050] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0051] (1) The present invention uses a hydrotreating catalyst with strong aromatic directional saturation ability based on the differences in aromatic structure and composition in the hydrotreating reaction zone, thereby achieving maximum hydrogenation saturation of aromatics and significantly reducing the aromatic content in the hydrocracking product.

[0052] (2) The present invention loads nickel-molybdenum active metals, which have strong cyclic hydrocarbon ring-opening ability, onto Y molecular sieve, thereby enhancing the ring-opening cracking reaction of aromatic hydrocarbons. Furthermore, cobalt-molybdenum active metals, which have strong paraffin adsorption ability, onto ZSM-22 molecular sieve, thereby reducing the effect of aromatic hydrocarbons on paraffin adsorption isomerization reactions and lowering the pour point of transformer oil. The combination of these two metals solves the difficult problem of balancing aromatic hydrocarbon ring-opening ability with paraffin isomerization ability.

[0053] (3) The hydrogenation catalyst system prepared by the method of the present invention can achieve deep hydrogenation and efficient conversion of polycyclic aromatic hydrocarbons, and the transformer oil produced is of good quality.

[0054] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0055] The feedstock oils used in the following Examples and Comparative Examples were straight-run wax oil and catalytic diesel fuel, with the catalytic diesel fuel blending ratio at 15%. Their properties are shown in Table 1. Both the Examples and Comparative Examples were evaluated for 2200 hours under the conditions listed in Table 3 to compare the properties of the transformer oils produced using different catalyst systems. The evaluation results for the Examples are shown in Table 4, and those for the Comparative Examples are shown in Table 5.

[0056] In the present invention, unless otherwise specified, percentages refer to mass fractions.

[0057] Example 1

[0058] The hydrotreating reaction zone is filled with FHUDS-5 and FHUDS-6 hydrotreating catalysts respectively along the logistics direction, and the filling volume ratio between the two is 1:0.2.

[0059] The hydrocracking reaction zone is filled with composite hydrocracking catalyst HC-1, the preparation method of which is as follows:

[0060] (1) First, 25% Y molecular sieve and 60% alumina were mechanically mixed, and then 5 wt% of polyethylene glycol binder relative to the carrier was added and fully rolled and formed. The mixture was then dried at 70°C for 3 hours to obtain a catalyst carrier. Nickel and molybdenum active metals were impregnated using an equal volume impregnation method, wherein the mass fraction of nickel species calculated as NiO was 3% and the mass fraction of molybdenum calculated as MoO3 was 12 wt%. After the active metal impregnation, the mixture was dried at 80°C for 3 hours and calcined at 430°C for 4 hours to obtain a first hydrocracking catalyst. After calcination, the polyethylene glycol binder disappeared.

[0061] (2) First, 5% ZSM-22 molecular sieve and 70% alumina were mechanically mixed, and then 10 wt% of polyethylene glycol binder relative to the carrier was added and fully rolled and formed, and then dried at 80°C for 10 hours to obtain a catalyst carrier; the catalyst carrier was impregnated with a solution containing cobalt and molybdenum active metal components, and the cobalt and molybdenum active metal was impregnated by an equal volume impregnation method, wherein the mass fraction of nickel species calculated as CoO was 2% and the mass fraction of molybdenum calculated as MoO3 was 23 wt%. After the active metal was impregnated, the second hydrocracking catalyst was obtained after drying at 80°C for 10 hours and calcining at 500°C for 12 hours. Finally, the first hydrocracking catalyst and the second hydrocracking catalyst were mechanically mixed at a ratio of 1:0.2 to obtain the final composite hydrocracking catalyst HC-1. The hydrocracking catalyst HC-1 prepared above was loaded into a hydrocracking reactor, and a 2200-hour process evaluation experiment was carried out according to the conditions in Table 3.

[0062] Example 2

[0063] The hydrotreating reaction zone is filled with FHUDS-5 and FHUDS-6 hydrotreating catalysts respectively along the logistics direction, and the filling volume ratio between the two is 1:2.

[0064] The hydrocracking reaction zone is filled with composite hydrocracking catalyst HC-2, the preparation method of which is as follows:

[0065] (1) First, 40% Y molecular sieve and 40% alumina were mechanically mixed, and then 6% by weight of polyethylene glycol binder relative to the carrier was added and fully rolled and formed. The mixture was then dried at 70°C for 5 hours to obtain a catalyst carrier. Nickel and molybdenum active metals were impregnated by an equal volume impregnation method, wherein the mass fraction of nickel species calculated as NiO was 5% and the mass fraction of molybdenum calculated as MoO3 was 15% by weight. After the active metal impregnation, the mixture was dried at 80°C for 10 hours and calcined at 430°C for 10 hours to obtain a first hydrocracking catalyst.

[0066] (2) First, 15% ZSM-22 molecular sieve and 60% alumina were mechanically mixed, and then 8 wt% of polyethylene glycol binder relative to the carrier was added and fully rolled and formed. The catalyst carrier was then dried at 80°C for 6 hours to obtain a catalyst carrier. The catalyst carrier was impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals were impregnated using an equal volume impregnation method, wherein the mass fraction of nickel species calculated as CoO was 10 wt% and the mass fraction of molybdenum calculated as MoO3 was 15 wt%. After the active metals were impregnated, the catalyst carrier was dried at 80°C for 6 hours and calcined at 550°C for 4 hours to obtain the second hydrocracking catalyst. Finally, the first hydrocracking catalyst and the second hydrocracking catalyst were mechanically mixed at a ratio of 1:0.4 to obtain the final composite hydrocracking catalyst HC-2. The hydrocracking catalyst HC-2 prepared above was loaded into a hydrocracking reactor, and a 2200-hour process evaluation experiment was carried out according to the conditions in Table 3.

[0067] Example 3

[0068] The hydrotreating reaction zone is filled with FHUDS-7 and FHUDS-6 hydrotreating catalysts respectively along the logistics direction, and the filling volume ratio between the two is 1:3.

[0069] The hydrocracking reaction zone is filled with composite hydrocracking catalyst HC-3, the preparation method of which is as follows:

[0070] (1) First, 30% Y molecular sieve and 40% alumina were mechanically mixed, and then 6% by weight of polyethylene glycol binder relative to the carrier was added and fully rolled and formed. The mixture was then dried at 80°C for 6 hours to obtain a catalyst carrier. Nickel and molybdenum active metals were impregnated using an equal volume impregnation method, wherein the mass fraction of nickel species calculated as NiO was 5% and the mass fraction of molybdenum calculated as MoO3 was 25% by weight. After the active metal impregnation, the mixture was dried at 80°C for 8 hours and calcined at 430°C for 8 hours to obtain a first hydrocracking catalyst.

[0071] (2) First, 20% ZSM-22 molecular sieve and 50% alumina were mechanically mixed, and then 4 wt% polyethylene glycol binder relative to the carrier was added and fully rolled and formed. The catalyst carrier was then dried at 80°C for 6 hours to obtain a catalyst carrier. The catalyst carrier was impregnated with a solution containing cobalt and molybdenum active metal components. The cobalt and molybdenum active metals were impregnated using an equal volume impregnation method, wherein the mass fraction of nickel species calculated as CoO was 10% and the mass fraction of molybdenum calculated as MoO3 was 20 wt%. After the active metals were impregnated, the catalyst carrier was dried at 80°C for 7 hours and calcined at 550°C for 5 hours to obtain the second hydrocracking catalyst. Finally, the first hydrocracking catalyst and the second hydrocracking catalyst were mechanically mixed in a ratio of 1:1 to obtain the final composite hydrocracking catalyst HC-3. The hydrocracking catalyst HC-3 prepared above was loaded into a hydrocracking reactor, and a 2200-hour process evaluation experiment was carried out according to the conditions in Table 3.

[0072] Example 4

[0073] The hydrotreating reaction zone is filled with FHUDS-5 and FHUDS-6 hydrotreating catalysts respectively along the logistics direction, and the filling volume ratio between the two is 1:1.

[0074] The hydrocracking reaction zone is filled with composite hydrocracking catalyst HC-4, the preparation method of which is as follows:

[0075] (1) First, 30% Y molecular sieve and 50% alumina were mechanically mixed, and then a polyethylene glycol binder (7 wt% relative to the carrier) was added and fully rolled and formed. The mixture was then dried at 70°C for 6 hours to obtain a catalyst carrier. Nickel and molybdenum active metals were impregnated using an equal volume impregnation method, wherein the mass fraction of nickel species calculated as NiO was 5% and the mass fraction of molybdenum calculated as MoO3 was 15 wt%. After the active metal impregnation, the mixture was dried at 80°C for 6 hours and calcined at 450°C for 6 hours to obtain a first hydrocracking catalyst.

[0076] (2) First, 16% ZSM-22 molecular sieve and 60% alumina were mechanically mixed, and then 9 wt% of polyethylene glycol binder relative to the carrier was added and fully rolled and formed, and then dried at 80°C for 8 hours to obtain a catalyst carrier; the catalyst carrier was impregnated with a solution containing cobalt and molybdenum active metal components, and the cobalt and molybdenum active metal was impregnated by an equal volume impregnation method, wherein the mass fraction of nickel species calculated as CoO was 6 wt% and the mass fraction of molybdenum calculated as MoO3 was 18 wt%. After the active metal was impregnated, the second hydrocracking catalyst was obtained after drying at 80°C for 8 hours and calcining at 520°C for 8 hours. Finally, the first hydrocracking catalyst and the second hydrocracking catalyst were mechanically mixed at a ratio of 1:0.8 to obtain the final composite hydrocracking catalyst HC-4. The hydrocracking catalyst HC-4 prepared above was loaded into a hydrocracking reactor, and a 2200-hour process evaluation experiment was carried out according to the conditions in Table 3.

[0077] Comparative Example 1

[0078] The industrial FHUDS-5 hydrotreating catalyst was loaded into the hydrotreating reactor, and the FC-14 hydrocracking catalyst developed by Sinopec Dalian Research Institute of Petrochemicals was loaded into the hydrocracking reactor. A 2200-h process evaluation experiment was carried out according to the conditions in Table 3.

[0079] Comparative Example 2

[0080] The industrial FHUDS-7 hydrotreating catalyst was loaded into the hydrotreating reactor, and the FC-14 hydrocracking catalyst developed by Sinopec Dalian Research Institute of Petrochemicals was loaded into the hydrocracking reactor. A 2200-h process evaluation experiment was carried out according to the conditions in Table 3.

[0081] Comparative Example 3

[0082] Industrial FHUDS-5 and FTX hydrotreating catalysts were loaded into the hydrotreating reactor at a loading volume ratio of 1:1. The FC-14 hydrocracking catalyst developed by Sinopec Dalian Research Institute of Petrochemicals was loaded into the hydrocracking reactor. A 2200-h process evaluation experiment was carried out according to the conditions in Table 3.

[0083] Comparative Example 4

[0084] The industrial FHUDS-5 hydrotreating catalyst was loaded into the hydrotreating reactor, and the HC-3 hydrocracking catalyst in Example 2 was loaded into the hydrocracking reactor. A 2200-h process evaluation experiment was conducted according to the conditions in Table 3.

[0085] Table 1 Properties of crude oil

[0086] Raw oil name Mixed raw materials <![CDATA[Density (20 °C) / g·cm -3 > 0.9202 Distillation range / ℃ 180～550 S，％ 2.05 <![CDATA[N / μg·g -1 ]]> 689 Aromatics, wt% 40.6

[0087] Table 2 Industrial catalysts

[0088] Industrial agents FHUDS-5 FHUDS-7 FC-14 Metal Type Co-Mo Co-Mo Ni-W Pore diameter / nm 2~10nm 2~10nm 3~10nm <![CDATA[Pore volume / mL·g -1 > ≥0.25 ≥0.25 ≥0.32 <![CDATA[Specific surface area / m 2 ·g -1 > ≥180 ≥180 ≥320 shape Gear Ball Gear Ball Gear Ball <![CDATA[Loading heap ratio, g / cm 3 > 0.80 0.75 0.90

[0089] Table 3 Evaluation conditions

[0090] Reaction pressure, MPa 17.0 <![CDATA[Space velocity of preparation volume, h -1 > 1.0 <![CDATA[Volume hourly space velocity of cracking agent, h -1 > 1.5 Nitrogen content of refined oil, ppm 10 Hydrocracking conversion rate, % 70 Hydrogen-to-oil ratio at the inlet of hydrotreating / hydrocracking reactor 900:1 / 1200:1 Running time, h 2200

[0091] Table 4 Example test results

[0092] project Example 1 Example 2 Example 3 Example 4 Transformer oil requirements <![CDATA[Density, g / cm 3 > 0.8245 0.8225 0.8215 0.8280 ≯0.895 PAHs content, wt% 0.16 0.14 0.12 0.20 ≯3 Pour point, ℃ -16 -15 -17 -13 ≯-10 Saybolt color 25+ 25+ 25+ 25+ 25+

[0093] Table 5 Comparative Example Test Results

[0094]

[0095]

[0096] The experimental results of the comparative examples and the examples show that, under the conditions of controlling the same conversion rate, the hydrocracking method of the present invention not only reduces hydrogen consumption, but also produces transformer oil with low aromatic content and pour point, making it a qualified transformer oil. When the catalyst grading system under the conditions of Example 3 is used, the transformer oil produced at 275-365°C has the lowest polycyclic aromatic hydrocarbon content of 0.12% and a pour point of -17°C.

[0097] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0098] (1) The present invention uses a hydrotreating catalyst with strong aromatic directional saturation ability based on the differences in aromatic structure and composition in the hydrotreating reaction zone, thereby achieving maximum hydrogenation saturation of aromatics and significantly reducing the aromatic content in the hydrocracking product.

[0099] (2) The present invention loads nickel-molybdenum active metals, which have strong cyclic hydrocarbon ring-opening ability, onto Y molecular sieve, thereby enhancing the ring-opening cracking reaction of aromatic hydrocarbons. Furthermore, cobalt-molybdenum active metals, which have strong paraffin adsorption ability, onto ZSM-22 molecular sieve, thereby reducing the effect of aromatic hydrocarbons on paraffin adsorption isomerization reactions and lowering the pour point of transformer oil. The combination of these two metals solves the difficult problem of balancing aromatic hydrocarbon ring-opening ability with paraffin isomerization ability.

[0100] (3) The hydrogenation catalyst system prepared by the method of the present invention can achieve deep hydrogenation and efficient conversion of polycyclic aromatic hydrocarbons, and the transformer oil produced is of good quality.

[0101] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A hydrocracking method for producing transformer oil, characterized in that: The following steps are involved: In step 1, the feedstock oil is mixed with hydrogen and then enters the hydrorefining reaction zone to contact and react with the hydrorefining catalyst. In step 2, the effluent from the hydrorefining reaction enters the hydrocracking reaction zone to contact and react with the hydrocracking catalyst. In step 3, the effluent from the hydrocracking reaction passes through a separation system to obtain a product. Wherein, the hydrorefining reaction zone described in step 1 is filled with two hydrorefining catalysts in a graded manner, the upper part of the reaction zone is filled with a cobalt-molybdenum type hydrorefining catalyst, and the lower part of the reaction zone is filled with a nickel-molybdenum type hydrorefining catalyst; the hydrocracking catalyst described in step 2 includes a carrier and an active metal, and the hydrocracking catalyst is prepared with Y molecular sieve, ZSM-22 molecular sieve and alumina as carriers and Group VIII and Group VIB metals as active metal components; The preparation method of the hydrocracking catalyst is as follows: First, 30% Y molecular sieve and 40% alumina were mechanically mixed, and then a polyethylene glycol binder (6 wt% relative to the carrier) was added and fully rolled to form a catalyst carrier. The catalyst carrier was then dried at 80°C for 6 hours to obtain a catalyst carrier. An equal volume impregnation method was used to impregnate nickel and molybdenum active metals, wherein the mass fraction of nickel species calculated as NiO was 5% and the mass fraction of molybdenum calculated as MoO3 was 25 wt%. After impregnation with the active metals, the catalyst carrier was dried at 80°C for 8 hours and calcined at 430°C for 8 hours to obtain a first hydrocracking catalyst. First, 20% ZSM-22 molecular sieve and 50% alumina were mechanically mixed, and a polyethylene glycol binder of 4 wt% relative to the carrier was added and fully rolled to form, and then dried at 80°C for 6 hours to obtain a catalyst carrier; the catalyst carrier was impregnated with a solution containing cobalt and molybdenum active metal components, and the cobalt and molybdenum active metals were impregnated by an equal volume impregnation method, wherein the mass fraction of nickel species calculated as CoO was 10%, and the mass fraction of molybdenum calculated as MoO3 was 20 wt%; after the active metal was impregnated, the second hydrocracking catalyst was obtained after being dried at 80°C for 7 hours and calcined at 550°C for 5 hours; finally, the first hydrocracking catalyst and the second hydrocracking catalyst were mechanically mixed in a ratio of 1:1 to obtain the final composite hydrocracking catalyst.

2. A hydrocracking method for producing transformer oil according to claim 1, characterized in that, The reaction pressure of the hydrofining reaction zone in step 1 is 10.0-20.0 MPa, the hydrofining reaction temperature is 320-420°C, and the volume space velocity is 0.3-3.0 h -1 In step 2, the reaction pressure of the hydrocracking reaction zone is 10.0 to 20.0 MPa, the hydrocracking reaction temperature is 340 to 450 ° C, and the volume space velocity is 0.5 to 3.0 h -1 .

3. A hydrocracking method for producing transformer oil according to claim 1, characterized in that, The raw oil in step 1 is a mixture of straight-run wax oil and catalytic diesel, with an initial boiling point of 180-310°C, a final boiling point of 440-570°C, and a density of 0.89-0.93 g / cm 3 ; The blending ratio of catalytic diesel in the raw materials is 10%~30%.

4. A hydrocracking method for producing transformer oil according to claim 1, characterized in that, The crystal form of the alumina in the hydrocracking catalyst carrier includes one or more combinations of α-alumina, β-alumina, γ-alumina, δ-alumina, θ-alumina, and η-alumina.

5. A hydrocracking method for producing transformer oil according to claim 1, characterized in that, The impregnation methods include equal volume impregnation, excess volume impregnation and steam impregnation.

6. A hydrocracking method for producing transformer oil according to claim 1, characterized in that, The volume filling ratio of the hydrotreating catalyst in the upper reaction zone and the lower reaction zone in step 1 is 5: (1~15).

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