Composite hydrocracking catalyst, method for preparing the same and use thereof

Abstract

The application provides a composite hydrocracking catalyst, wherein ZSM-5 molecular sieve and alumina are used to load nickel and molybdenum as catalyst I, Beta molecular sieve and alumina are used to load cobalt and molybdenum as catalyst II, catalyst I and catalyst II are mixed to obtain the composite hydrocracking catalyst. The application can consider the indicators of the aromatic content and the pour point of transformer oil, can realize the partition enhancement of the aromatic ring opening reaction and the chain alkane bond breaking isomerization reaction, and then reduces the aromatic content and the pour point of the hydrocracking diesel oil, so that the qualified transformer oil product can be directly produced by the conventional hydrocracking means.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hydrocracking, and particularly relates to a composite hydrocracking catalyst. BACKGROUND

[0002] Transformer oil is a special oil stable at high temperature, which has excellent electrical insulation performance. It has two important functions in the transformer, namely, suppressing electric arc and dissipating heat generated by the transformer. The high-specification transformer oil has high requirements on the content of aromatic hydrocarbons and the pour point. Although the diesel oil component produced by the conventional hydrocracking technology can meet the requirements on the distillation density, the aromatic hydrocarbons and the pour point are often difficult to be satisfied simultaneously. The main reason is that the conventional hydrocracking catalyst often uses a single molecular sieve and active metal component, which is difficult to balance the ring-opening of aromatic hydrocarbons and the isomerization of paraffins, and the produced transformer oil cannot meet the requirements of the national standard.

[0003] Therefore, it is of great significance for enterprises to develop a hydrocracking catalyst that can balance the ring-opening of aromatic hydrocarbons and the isomerization of paraffins, and simultaneously reduce the content of aromatic hydrocarbons and n-alkanes in the transformer oil component produced by hydrocracking, so as to produce qualified transformer oil products.

[0004] CN113969180A discloses a low-pressure hydrodearomatization method of hydrocracking diesel oil fraction. The invention uses a fixed-bed hydrogenation device as a reactor, and uses a nickel reduced catalyst to hydrogenate and saturate the hydrocracking diesel oil fraction under a hydrogen partial pressure of 1-3 MPa to obtain a low-aromatic product, which can meet the de-aromatization requirements of producing 5# industrial white oil from hydrocracking diesel oil fraction. However, even if the hydrocracking diesel oil is deeply hydrogenated and saturated, the pour point of the refined diesel oil cannot be greatly changed, and it is difficult to directly produce transformer oil.

[0005] CN107619706A discloses a transformer oil and a preparation method thereof. The transformer oil is prepared by using naphthenic and paraffin-based vacuum distillate oil as raw materials, through a three-stage high-pressure hydrogenation production process, and adding a combined aromatic hydrocarbon additive and an antioxidant. The components are as follows in mass percentage: 15% to 25% of paraffin-based base oil fraction, 4% to 7% of combined aromatic hydrocarbon additive, 0.3% ± 0.05% of antioxidant, and the balance of naphthenic base oil. The transformer oil provided by the invention has excellent carbon structure and anti-gas separation performance, and the low-temperature performance and antioxidant performance are higher than those of existing products on the market. However, the method has strict requirements on the composition of raw materials, the process flow is complex, and the production cost of transformer oil is high. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a preparation method of a composite hydrocracking catalyst, and a method for producing qualified transformer oil products by using the same.

[0007] The application provides a preparation method of a composite hydrocracking catalyst, comprising the following steps:

[0008] (1) mixing ZSM-5 molecular sieve, alumina and a binder to form a carrier I, loading nickel and molybdenum on the carrier I, drying, and calcining to obtain a catalyst I, wherein the average pore size of the catalyst I is 6.0-12.0 nm;

[0009] (2) mixing Beta molecular sieve, alumina and a binder to form a carrier II, loading cobalt and molybdenum on the carrier II, drying, and calcining to obtain a catalyst II, wherein the average pore size of the catalyst II is 2.0-4.0 nm;

[0010] (3) mixing the catalyst I and the catalyst II to obtain the composite hydrocracking catalyst.

[0011] The skilled in the art should understand that the average pore sizes of the catalyst I and the catalyst II are different, and the control of the pore size is known to the skilled in the art, and specifically, on the one hand, the pore size can be controlled by the selection of raw materials, for example, in the application, the pore size can be realized by selecting alumina, molecular sieve with different pore sizes and controlling the content thereof; on the other hand, the pore size can be controlled by the reaction conditions in the preparation process, such as the temperature and time of drying and calcining, so as to obtain a catalyst with a target pore size.

[0012] Further, the active components in steps (1) and (2) are loaded by an impregnation method, including an equal volume impregnation method, an excess volume impregnation method and a steam impregnation method, and the specific operation method is known to the skilled in the art.

[0013] Further, the temperature of drying in steps (1) and (2) is 60-140 DEG C, and the drying time is 2-12 h; the temperature of calcining is 300-550 DEG C, preferably 400-500 DEG C, and the calcining time is 2-12 h.

[0014] Further, based on the total weight of the catalyst I, the alumina accounts for 40.0-60.0 wt%, the ZSM-5 molecular sieve accounts for 10.0-30.0 wt%, the nickel accounts for 2.0-8.0 wt% in terms of oxide, and the molybdenum accounts for 10.0-25.0 wt% in terms of oxide.

[0015] Further, based on the total weight of the catalyst II, the alumina accounts for 60-80 wt%, the Beta molecular sieve accounts for 5-20 wt%, the cobalt accounts for 2-8 wt% in terms of oxide, and the tungsten accounts for 8-15 wt% in terms of oxide.

[0016] Further, the weight ratio of the catalyst I and the catalyst II is 1:0.2-1:4, preferably 1:0.5-1:1.

[0017] Further, the specific surface area of the catalyst I is 100-600 m 2 / g, the pore volume is 0.12-0.45 cm 3 / g, and the acid amount is 0.10-0.50 mmol / g.

[0018] Further, the specific surface area of the catalyst II is 200-700 m 2 / g, the pore volume is 0.15-0.50 cm 3 / g, and the acid amount is 0.05-0.40 mmol / g.

[0019] Further, the average pore diameter of the catalyst I is 2.0-8.0 nm higher than that of the catalyst II.

[0020] Further, the specific surface area of the composite hydrocracking catalyst is 150.0-650.0 m 2 / g, the average pore diameter is 2.0-10.0 nm, the pore volume is 0.13-0.47 cm 3 / g, and the acid amount is 0.10-0.45 mmol / g.

[0021] Further, the shape of the obtained hydrocracking catalyst can be clover, four-leaf clover, cylinder, and tooth ball.

[0022] The technical purpose of the second aspect of the present application is to provide the hydrocracking catalyst prepared by the above preparation method.

[0023] The hydrocracking catalyst of the present application loads cobalt-molybdenum active metal on ZSM-5 molecular sieve, increases the adsorption capacity of paraffin, strengthens the bond breaking and isomerization of paraffin, loads nickel-molybdenum active metal on Beta molecular sieve, can strengthen the adsorption capacity of aromatic hydrocarbon, enhance the ring-opening cracking reaction of aromatic hydrocarbon, and can significantly reduce the content of aromatic hydrocarbon in transformer oil.

[0024] The technical purpose of the third aspect of the present application is to provide the application of the above hydrocracking catalyst, and the above hydrocracking catalyst is used for preparing transformer oil by oil product hydrocracking.

[0025] Further, the oil product is a feedstock such as vacuum gas oil and coking wax oil. The density is 0.88-0.94 g / cm 3 , the initial boiling point is 220-260℃, the dry point is 500-580℃, the sulfur content is 0.5wt%-3.0wt%, and the nitrogen content is 200-2000 μg·g -1 .

[0026] Further, the temperature of the hydrocracking reaction is 340-420℃, preferably 360-400℃; the reaction pressure is 6.0-15.0 MPa, preferably 8.0-12.0 MPa; the hydrocracking segment volume space velocity is 0.5-4.0 h -1 , preferably 1.0-3.0 h -1 .

[0027] The technical purpose of the fourth aspect of the present application is to provide a method for producing transformer oil, which sequentially passes the oil through the beds filled with the hydrofining catalyst and the hydrocracking catalyst to produce the transformer oil.

[0028] Further, the reaction pressure of the hydrofining is 6.0-15.0 MPa, preferably 8.0-12.0 MPa; the reaction temperature is 320-400℃, preferably 340-380℃; the hydrofining volume space velocity is 0.2-2.0 h -1 , preferably 0.5-1.5 h -1 .

[0029] Further, the temperature of the hydrocracking reaction is 340-420℃, preferably 360-400℃; the reaction pressure is 6.0-15.0 MPa, preferably 8.0-12.0 MPa; the hydrocracking segment volume space velocity is 0.5-4.0 h -1 , preferably 1.0-3.0 h -1 .

[0030] The oil is straight-run diesel oil, catalytic diesel oil or mixed oil thereof. The density is 0.80-0.92 g / cm 3 , the initial boiling point is 180-300℃, and the final boiling point is 320-420℃. When the mixed oil of straight-run diesel oil and catalytic diesel oil is used as the raw material, the catalytic diesel oil is mixed at a ratio of 20.0-50.0 wt%.

[0031] Compared with the prior art, the method of the present application has the following beneficial effects:

[0032] (1) The present application loads cobalt-molybdenum active metals on ZSM-5 molecular sieves to increase the adsorption capacity of paraffins, strengthen the bond breaking and isomerization of paraffins, significantly reduce the pour point of transformer oil, and improve the yield of transformer oil. The nickel-molybdenum active metals loaded on the Beta molecular sieves can enhance the adsorption capacity of aromatics, strengthen the ring-opening cracking reaction of aromatics, significantly reduce the content of aromatics in transformer oil, and improve its stability and color. After the two are compounded, the aromatics content and pour point of transformer oil can be considered, and the ring-opening reaction of aromatics and the bond breaking and isomerization reaction of paraffins can be strengthened in different zones, thereby reducing the content of aromatics and the pour point of hydrocracking diesel oil, so that the conventional hydrocracking means can directly produce qualified transformer oil products.

[0033] (2) In the present application, by controlling the pore size difference of two different catalysts, the confined conversion of different sizes and types of raw oil is realized. The catalyst containing ZSM-5 molecular sieve has a larger pore size than the catalyst containing Beta molecular sieve, the reactant pressure in the catalyst containing ZSM-5 molecular sieve with large pore size is large, the diffusion resistance is small, and the secondary cracking of paraffin is less, while the reactant pressure in the catalyst containing Beta molecular sieve with small pore size is low, which will promote the flow of large molecular aromatic reactants into the surface of the Beta molecular sieve to occur ring-opening and cracking reactions, which is beneficial to reduce the amount of aromatics and coking.

[0034] (3) The hydrogenation catalyst system prepared by the method of the present application can realize selective hydrogenation and directional conversion of polycyclic aromatic hydrocarbons, not only the hydrogen consumption of the device is low, but also the quality of the produced transformer oil is good.

[0035] (4) The catalyst prepared by the method of the present application has simple preparation process, good reaction activity and selectivity, low required reaction temperature, and can significantly prolong the operation period of the device. DETAILED DESCRIPTION

[0036] The following will further illustrate the preparation method of the hydrogenation cracking catalyst provided by the present application by combining the examples, to compare and embody the effect and advantages of the hydrogenation cracking method of the present application, but not limit the present application.

[0037] In the following examples, the experimental methods are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified. The properties of different alumina used in the examples and comparative examples are shown in Table 1.

[0038] Table 1 Physicochemical properties of different alumina

[0039] Item Alumina-1 Alumina-2 Average pore diameter / nm 12.5 nm 6.8 nm Pore volume / mL-g -1 ]] 0.35 0.30 Specific surface area / m 2 ·g -1 ]]> 112.0 176.5

[0040] In the present application, unless otherwise specified, the percentage refers to the mass fraction.

[0041] In the following examples, the specific surface area and pore volume of the catalyst are determined by N2 adsorption-desorption method, the average pore size is determined by BJH method, and the acid amount is determined by NH3-TPD method.

[0042] Example 1

[0043] Preparation of composite hydrogenation cracking catalyst HCK-1

[0044] (1) 30%wt ZSM-5 molecular sieve and 40wt% alumina-1 are mechanically mixed, then a binder is added and the mixture is sufficiently rolled and formed, and then the catalyst carrier is obtained by drying at 100°C for 4h; an equal volume of a solution containing nickel-molybdenum active metal components is used to impregnate the catalyst carrier, and the nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of Ni is 4.5wt% as NiO, and the mass fraction of Mo is 25.5wt% as MoO3. Catalyst I is obtained after drying at 100°C for 4h and calcining at 500°C for 10h.

[0045] (2) 20wt% Beta molecular sieve and 60wt% alumina-2 are mechanically mixed, then a binder is added and the mixture is sufficiently rolled and formed, and then the catalyst carrier is obtained by drying at 60°C for 6h; the catalyst carrier is impregnated with a solution containing cobalt-molybdenum active metal components, and the cobalt-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of Co is 5.5wt% as CoO, and the mass fraction of Mo is 14.5wt% as MoO3. Catalyst II is obtained after drying at 60°C for 6h and calcining at 450°C for 4h.

[0046] (3) Finally, catalyst I and catalyst II are mechanically mixed in a weight ratio of 1:4 to obtain the final composite hydrocracking catalyst HCK-1.

[0047] In the composite hydrocracking catalyst, the average pore diameter of catalyst I is 10.0nm, the average pore diameter of catalyst II is 3.0nm, the average pore diameter of catalyst I is 7.0nm higher than that of catalyst II, the specific surface area of HCK-1 is 245.4m2 / g, the average pore diameter is 4.4nm, the pore volume is 0.27cm3 / g, and the acid amount is 0.25mmol / g. 2 3 / g, the average pore diameter is 4.4nm, the pore volume is 0.27cm

[0048] Two reactors in series are used, and a hydrofining catalyst and the hydrocracking catalyst prepared in the application are sequentially loaded, that is, a hydrofining catalyst FF-66 is loaded in the first reactor, and the HCK-1 hydrocracking catalyst is loaded in the second reactor. The feedstock oil 1 in Table 1 is used as the raw material, and the process evaluation experiment is carried out for 2500h according to the process reaction conditions in Table 3.

[0049] Example 2

[0050] Preparation of composite hydrocracking catalyst HCK-2

[0051] (1) 30%wt ZSM-5 molecular sieve and 40wt% alumina-1 are mechanically mixed, then a binder is added and the mixture is sufficiently rolled and formed, and then the catalyst carrier is obtained by drying at 100°C for 4h; an equal volume of a solution containing nickel-molybdenum active metal components is used to impregnate the catalyst carrier, and the nickel-molybdenum active metal is impregnated by an equal volume impregnation method, wherein the mass fraction of Ni is 4.5wt% as NiO, and the mass fraction of Mo is 25.5wt% as MoO3. Catalyst I is obtained after drying at 100°C for 4h and calcining at 500°C for 10h.​

[0052] (2) 5wt% Beta zeolite and 80wt% alumina-2 are mechanically mixed, then a binder is added, and the mixture is sufficiently rolled and formed, and then dried at 100°C for 4h to obtain a catalyst carrier; the catalyst carrier is impregnated with a solution containing cobalt and molybdenum active metal components, and cobalt and molybdenum active metals are impregnated by using an equal volume impregnation method, wherein the mass fraction of Co, calculated as CoO, is 2.5wt%, and the mass fraction of Mo, calculated as MoO3, is 12.5wt%. After being dried at 80°C for 4h and calcined at 500°C for 6h, catalyst II is obtained.

[0053] (3) Finally, catalyst I and catalyst II are mechanically mixed in a weight ratio of 1:2 to obtain the final composite hydrocracking catalyst HCK-2.

[0054] In the composite hydrocracking catalyst, the average pore diameter of catalyst I is 11.5nm, the average pore diameter of catalyst II is 3.5nm, the average pore diameter of catalyst I is 8.0nm higher than that of catalyst II, the specific surface area of HCK-2 is 238.7m 2 / g, the average pore diameter is 6.2nm, the pore volume is 0.37cm 3 / g, and the acid amount is 0.15mmol / g.

[0055] Two reactors in series are used, and a hydrofining catalyst and the hydrocracking catalyst prepared in the application are sequentially loaded, i.e. a hydrofining catalyst FF-66 is loaded in the first reactor, and the HCK-2 hydrocracking catalyst is loaded in the second reactor. The raw oil 1 in Table 1 is used as the raw material, and the process evaluation experiment is carried out for 2500h according to the process reaction conditions in Table 3.

[0056] Example 3

[0057] Preparation of composite hydrocracking catalyst HCK-3

[0058] (1) 20%wt ZSM-5 zeolite and 50wt% alumina-1 are mechanically mixed, then a binder is added, and the mixture is sufficiently rolled and formed, and then dried at 80°C for 8h to obtain a catalyst carrier; nickel and molybdenum active metals are impregnated by using an equal volume impregnation method, wherein the mass fraction of Ni, calculated as NiO, is 4.5wt%, and the mass fraction of Mo, calculated as MoO3, is 25.5wt%. After being dried at 100°C for 8h and calcined at 450°C for 10h, catalyst I is obtained.

[0059] (2) 15wt% Beta zeolite and 70wt% alumina-2 are mechanically mixed, then a binder is added and the mixture is sufficiently rolled and formed, and then dried at 90°C for 4h to obtain a catalyst carrier; the catalyst carrier is impregnated with a solution containing cobalt and molybdenum active metal components, and cobalt and molybdenum active metals are impregnated by using an equal volume impregnation method, wherein the mass fraction of Co is 3.5wt% as CoO, and the mass fraction of Mo is 11.5wt% as MoO3. After being dried at 80°C for 4h and calcined at 500°C for 4h, catalyst II is obtained.

[0060] (3) Finally, catalyst I and catalyst II are mechanically mixed in a weight ratio of 1:1 to obtain the final composite hydrocracking catalyst HCK-3.

[0061] In the composite hydrocracking catalyst, the average pore diameter of catalyst I is 6.0nm, the average pore diameter of catalyst II is 3.0nm, the average pore diameter of catalyst I is 3.0nm higher than that of catalyst II, the specific surface area of HCK-3 is 284.4m 2 / g, the average pore diameter is 4.5nm, the pore volume is 0.32cm 3 / g, and the acid amount is 0.25mmol / g.

[0062] Two reactors in series are used, and a hydrofining catalyst and the hydrocracking catalyst prepared in the application are sequentially loaded, i.e. the first reactor is loaded with a hydrofining catalyst FF-66, and the second reactor is loaded with the HCK-3 hydrocracking catalyst. The feedstock oil 2 in Table 1 is used as the raw material, and the process evaluation experiment is carried out for 2500h according to the process reaction conditions in Table 3.

[0063] Example 4

[0064] Preparation of composite hydrocracking catalyst HCK-4

[0065] (1) 25wt% ZSM-5 zeolite and 55wt% alumina-1 are mechanically mixed, then a binder is added and the mixture is sufficiently rolled and formed, and then dried at 100°C for 5h to obtain a catalyst carrier; nickel and molybdenum active metals are impregnated by using an equal volume impregnation method, wherein the mass fraction of Ni is 4.5wt% as NiO, and the mass fraction of Mo is 15.5wt% as MoO3. After being dried at 100°C for 5h and calcined at 500°C for 4h, catalyst I is obtained.

[0066] (2) 12wt% Beta zeolite and 68wt% alumina-2 were mechanically mixed, then binder was added and the mixture was sufficiently rolled and pressed to form a catalyst carrier, which was then dried at 120°C for 4h; 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 the equal volume impregnation method, in which the mass fraction of Co was 4.5wt% as CoO, and the mass fraction of Mo was 15.5wt% as MoO3. After drying at 120°C for 3h and calcination at 450°C for 3h, catalyst II was obtained.

[0067] (3) Finally, catalyst I and catalyst II were mechanically mixed in a weight ratio of 2:1 to obtain the final composite hydrocracking catalyst HCK-4.

[0068] In the composite hydrocracking catalyst, the average pore diameter of catalyst I was 4.5nm, the average pore diameter of catalyst II was 2.2nm, the average pore diameter of catalyst I was 2.3nm higher than that of catalyst II, the specific surface area of HCK-4 was 346.0m 2 / g, the average pore diameter was 3.7nm, the pore volume was 0.32cm 3 / g, and the acid amount was 0.35mmol / g.

[0069] Two reactors in series were used, and a hydrofining catalyst and the hydrocracking catalyst prepared in the application were sequentially loaded, i.e. the first reactor was loaded with hydrofining catalyst FF-66, and the second reactor was loaded with HCK-4 hydrocracking catalyst. The feedstock oil 2 in Table 1 was used as the raw material, and the process evaluation experiment was carried out for 2500h according to the process reaction conditions in Table 3.

[0070] Comparative Example 1

[0071] Preparation of composite hydrocracking catalyst HCK-5

[0072] (1) 30wt% ZSM-5 zeolite and 50wt% alumina-2 were mechanically mixed, then binder was added and the mixture was sufficiently rolled and pressed to form a catalyst carrier, which was then dried at 100°C for 7h; the catalyst carrier was impregnated with a solution containing nickel and molybdenum active metal components, and the nickel and molybdenum active metals were impregnated by the equal volume impregnation method, in which the mass fraction of Ni was 4.5wt% as NiO, and the mass fraction of Mo was 15.5wt% as MoO3. After drying at 100°C for 6h and calcination at 350°C for 8h, catalyst I was obtained.

[0073] (2) 20wt% Beta zeolite and 50wt% alumina-2 are mechanically mixed, then a binder is added and the mixture is sufficiently rolled and pressed to form a catalyst carrier, which is then dried at 60°C for 4h to obtain a catalyst carrier; the catalyst carrier is impregnated with a solution containing cobalt and molybdenum active metal components, and the cobalt and molybdenum active metals are impregnated by the equal-volume impregnation method, in which the mass fraction of Co, calculated as CoO, is 5.5wt%, and the mass fraction of Mo, calculated as MoO3, is 24.5wt%. After drying at 60°C for 4h and calcining at 350°C for 8h, catalyst II is obtained.

[0074] (3) Finally, catalyst I and catalyst II are mechanically mixed in a weight ratio of 1:4 to obtain the final composite hydrocracking catalyst HCK-5.

[0075] In the composite hydrocracking catalyst, the average pore diameter of catalyst I is 4.0nm, the average pore diameter of catalyst II is 3.2nm, the average pore diameter of catalyst I differs from that of catalyst II by less than 1nm, the specific surface area of HCK-5 is 447.0m 2 / g, the average pore diameter is 3.4nm, the pore volume is 0.38cm 3 / g, and the acid amount is 0.23mmol / g.

[0076] Two reactors in series are adopted, and a hydrofining catalyst and the hydrocracking catalyst prepared in the application are sequentially loaded in the reactors, i.e. the first reactor is loaded with the hydrofining catalyst FF-66, and the second reactor is loaded with the HCK-5 hydrocracking catalyst. The feedstock oil 1 in Table 1 is used as the raw material, and the 2500h process evaluation experiment is carried out according to the process reaction conditions in Table 3.

[0077] Comparative Example 2

[0078] The hydrofining catalyst FF-66 is loaded in the hydrofining reactor, the conventional industrial FC-46 hydrocracking catalyst is loaded in the second reactor instead of the hydrocracking catalyst of the application, the feedstock oil 1 in Table 1 is used as the raw material, and the 2500h process evaluation experiment is carried out according to the process reaction conditions in Table 3.

[0079] Comparative Example 3

[0080] The industrial FF-76 hydrofining catalyst is loaded in the hydrofining reactor, the conventional industrial FC-32 hydrocracking catalyst is loaded in the hydrocracking reactor, the feedstock oil 2 is used as the raw material, and the 2500h process evaluation experiment is carried out according to the conditions in Table 3.

[0081] The properties of the feedstock oils are shown in Table 2.

[0082] Table 2

[0083]

[0084]

[0085] The catalyst properties of hydrofining catalysts FF-66, FF-46, hydrocracking catalysts FC-46, FC-32 used in Example 5 and Comparative Example 1 are shown in Table 3.

[0086] Table 3

[0087] Industrial agent FF-66 FC-46 FC-32 Physicochemical properties Metal type Ni-Mo Ni-Mo Ni-W Pore diameter / nm 2-8 nm 3-9 nm 2-8 nm Pore volume / mL-g -1 ]] ≥0.28 ≥0.30 ≥0.28 Specific surface area / m 2 ·g -1 ]]> ≥180 ≥320 ≥300 Shape Tooth ball Tooth ball Tooth ball Charge bulk, g / cm 3 ]]> 0.75 0.64 0.72

[0088] Table 3 Evaluation Conditions

[0089] Reaction pressure, MPa 10.0 Refined volume space velocity, h -1 ]]> 2.0 Cracking agent volume space velocity, h -1 ]] 1.5 Refined oil nitrogen content, ppm 10 Hydrocracking conversion, % 70 Hydrofining reactor inlet hydrogen / oil ratio 600:1 Hydrocracking reactor inlet hydrogen / oil ratio 800:1 Running time, h 2500

[0090] The experimental results after running are shown in Table 4.

[0091] Table 4 Evaluation Results of Examples and Comparative Examples

[0092]

[0093]

[0094] From the experimental results of the comparative examples and examples, it can be seen that under the conditions of processing the same raw oil and controlling the same conversion rate, the hydrocracking catalyst of the present application has good activity, low hydrogen consumption, and the produced transformer oil has low aromatic content and pour point, and is qualified 0# transformer oil. When the catalyst system under the conditions of Example 1 is used, the polycyclic aromatic content of the produced 275-365°C transformer oil is the lowest, being 0.10%, and the pour point is -12°C.

Claims

1. A preparation method of a composite hydrocracking catalyst, comprising the following steps: (1) mixing ZSM-5 molecular sieve, alumina and a binder to form a carrier I, loading nickel and molybdenum on the carrier I, drying, and calcining to obtain a catalyst I, wherein the average pore size of the catalyst I is 6.0-12.0 nm; based on the total weight of the catalyst I, the alumina accounts for 40.0-60.0 wt%, the ZSM-5 molecular sieve accounts for 10.0-30.0 wt%, the nickel accounts for 2.0-8.0 wt% as an oxide, and the molybdenum accounts for 10.0-25.0 wt% as an oxide; (2) mixing Beta molecular sieve, alumina and a binder to form a carrier II, loading cobalt and molybdenum on the carrier II, drying, and calcining to obtain a catalyst II, wherein the average pore size of the catalyst II is 2.0-4.0 nm; based on the total weight of the catalyst II, the alumina accounts for 60-80 wt%, the Beta molecular sieve accounts for 5-20 wt%, the cobalt accounts for 2-8 wt% as an oxide, and the molybdenum accounts for 8-15 wt% as an oxide; (3) mixing catalyst I and catalyst II, the weight ratio of catalyst I and catalyst II being 1:0.2-1:4, to obtain the composite hydrocracking catalyst; the specific surface area of the composite hydrocracking catalyst being 150.0-650.0 m 2 / g, the average pore size being 2.0-9.0 nm, the pore volume being 0.13-0.47 cm 3 / g, and the acid amount being 0.10-0.45 mmol / g.

2. The production method according to claim 1, characterized by, The active components in steps (1) and (2) are loaded by an impregnation method, including an equal volume impregnation method, an excess volume impregnation method and a steam impregnation method.

3. The production method according to claim 1, characterized by, The drying temperature in steps (1) and (2) is 60-140℃, and the drying time is 2-12 h; the calcining temperature is 300-550℃, and the calcining time is 2-12 h.

4. The production method according to claim 1, characterized by, The average pore size of the catalyst I is higher than that of the catalyst II by 2.0-8.0 nm.

5. The hydrocracking catalyst prepared by the preparation method of any one of claims 1-4.

6. The application of the hydrocracking catalyst of claim 5, wherein the hydrocracking catalyst is used for preparing transformer oil by hydrocracking oil products.

7. Use according to claim 6, characterized in that, The oil product is vacuum gas oil or coking gas oil, the temperature of the hydrocracking reaction is 340-420℃, the reaction pressure is 6.0-15.0MPa, the volume space velocity of the hydrocracking section is 0.5-4.0h -1 .

8. A method of producing a transformer oil, characterized by, The oil product is sequentially passed through a bed layer filled with a hydrofining catalyst and the hydrocracking catalyst of claim 5 to produce transformer oil.

9. The method of claim 8, wherein, The oil product is straight-run diesel, catalytic diesel or a mixed oil thereof, and when the mixed oil of straight-run diesel and catalytic diesel is used as a raw material, the blending ratio of the catalytic diesel is 20.0-50.0 wt%.

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