CHEMICAL-TYPE HYDROCRACKING CATALYST, PREPARATION METHOD THEREFOR, AND APPLICATION THEREOF

Abstract

A chemical-type hydrocracking catalyst contains the following components: a) a β zeolite, b) a layered MWW-type zeolite with a lamellar thickness of 2-12 nm, c) a metal functional component, d) a binder, and optionally e) a metal function regulating component. The catalyst can be used in hydrocracking reactions of feedstock oils rich in polycyclic aromatics for producing light aromatics and light alkanes.

Claims

1. A hydrocracking catalyst, comprising the following components: a) a β zeolite, preferably a hydrogen-type β zeolite, b) a layered MWW-type zeolite, c) a metal functional component, and d) a binder, and optionally e) a metal function regulating component, wherein the layered MWW-type zeolite has a lamellar thickness of 2-12 nm.

2. The catalyst according to claim 1, characterized in that, based on a total zeolite weight of 100 parts, the metal functional component is 0.1 to parts, preferably 0.2 to 50 parts, more preferably 0.2 to 45 parts based on element; and/or the binder is 5 to 2000 parts, preferably 10 to 1000 parts, more preferably 10 to 900 parts.

3. The catalyst according to claim 1, characterized in that, the β zeolite accounts for 50-99 wt %, preferably 60-95 wt % of the total zeolite amount.

4. The catalyst according to claim 1, characterized in that, the layered MWW-type zeolite accounts for 1-50 wt %, preferably 5-40 wt % of the total zeolite amount.

5. The catalyst according to claim 1, characterized in that, the β zeolite has a silica-to-alumina ratio between 10 and 200, more preferably between 30 and 100; and/or the β zeolite has a pore spaciousness index between 15 and 18; and/or the layered MWW-type zeolite has a lamellar thickness in the range of 2-12 nm, preferably 2-10 nm, more preferably 2-6 nm; and/or the layered MWW-type zeolite has a silica-to-alumina ratio between 10 and 100; and/or the binder is selected from one of alumina and silica.

6. The catalyst according to claim 1, characterized in that, the metal functional component is (a) noble metal(s) of platinum and/or palladium; or the metal functional component is a metal component in a non-sulfurized state, preferably a combination of at least one of a Group VIII metal and a Group IIB metal in a non-sulfurized state with a Group VIB metal oxide in a non-sulfurized state, more preferably a composite of at least one of nickel Ni, cobalt Co, and zinc Zn in a non-sulfurized state with molybdenum oxide MoOx and/or tungsten oxide WOx.

7. The catalyst according to claim 6, characterized in that, a weight ratio of the Group VIB metal to the sum of the Group VIII metal and the Group IIB metal is (0.2 to 20): 1, preferably (0.3 to 15): 1, based on metal element.

8. The catalyst according to claim 6, characterized in that, the Group VIII metal is selected from at least one of cobalt and nickel; and/or the Group VIB metal oxide is selected from at least one of oxide of molybdenum and oxide of tungsten, preferably at least one of molybdenum dioxide, molybdenum trioxide, tungsten dioxide, tungsten trioxide; and/or the Group IIB metal is zinc.

9. The catalyst according to claim 1, characterized in that, when the catalyst comprises a metal function regulating component, based on metal element, a weight ratio of the metal functional component to the metal function regulating component is (0.1 to 20): 1, preferably (0.1 to 15): 1; preferably the metal function regulating component is selected from tin and bismuth.

10. A method for preparing the hydrocracking catalyst according to claim 1, comprising molding a catalyst carrier containing the β zeolite and the layered MWW-type zeolite and loading the components including the metal functional component to obtain a catalyst precursor, and then reducing the catalyst precursor.

11. The preparation method according to claim 10, characterized in it comprises the following steps: 1) mixing and drying components including the β zeolite and the layered MWW-type zeolite and the binder, then calcining in an air atmosphere at 500 to 600° C. to obtain a desired catalyst carrier; 2) formulating a metal aqueous solution with metal components comprising a metal compound of the noble metal(s) of platinum and/or palladium, or comprising at least one of the Group VIII metal compound and the Group IIB metal compound and a Group VIB metal compound; impregnating the catalyst carrier obtained above by an incipient wetness impregnation method, calcining in an air atmosphere at 450 to 580° C. after drying to obtain a catalyst precursor; 3) reducing the obtained catalyst precursor under hydrogen condition to 400 to 500° C. to obtain the catalyst; optionally formulating the metal compound of the metal function regulating component into a metal aqueous solution before the above step 2) and after step 1), carrying out an incipient wetness impregnation of the catalyst carrier obtained in step 1), and calcining in air atmosphere at 350 to 500° C. after drying.

12. Application of a hydrocracking catalyst in a hydrocracking reaction, comprising a step of contacting the catalyst according to claim 1, under a hydrocracking condition, with a feedstock oil, preferably a feedstock oil rich in aromatics, more preferably a feedstock oil rich in polycyclic aromatics, such as light cycle oil and ethylene tar.

13. The application according to claim 12, characterized in that, the aromatics in the feedstock oil have a weight percentage of greater than 50% by weight; and/or the feedstock oil has a nitrogen content of≤20 ppm, a sulfur content of≤200 ppm.

14. The application according to claim 12, characterized in that, conditions of the hydrocracking reaction include: a temperature of 300 to 450° C., a hydrogen partial pressure of 2.0 to 10.0 MPa, a liquid hourly space velocity of 0.2 to 4.0 hour.sup.−1, a hydrogen/oil volume ratio of 500 to 4000.

15. The application according to claim 12, characterized in that a single-pass conversion of fractions at above 200° C. is greater than 70% by weight, and a total selectivity for chemical raw materials including light aromatics and C.sub.2-C.sub.5 light alkanes is greater than 80% by weight.

16. Use of the layered MWW-type zeolite for conversion of polycyclic aromatics, wherein the lamellar thickness of the layered MWW-type zeolite is preferably in the range of 2-12 nm.

Description

DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 is a TEM micrograph of the β zeolite of the hydrocracking catalyst in the present invention.

[0060] FIG. 2 is a TEM micrograph of the layered MWW-type zeolite of the hydrocracking catalyst in the present invention.

[0061] Therein FIG. 1 is a TEM micrograph of the β zeolite used in Examples 2-5 and Example 7 of the present invention, having a particle size between 200 and 500 nm.

[0062] Therein FIG. 2 is a TEM micrograph of the layered MWW-type zeolite—SRZ-21 zeolite used in the examples of the present invention. An obvious layered structure can be observed, with a single-layer MWW structure having a lamellar thickness of 2.6-2.7 nm, and there are also a small amount of double- or triple-layer MWW structure, with a lamellar thickness of about 5-9 nm.

MODE OF CARRYING OUT THE INVENTION

[0063] The present invention will be further described in detail through embodiments. However, it needs to be indicated that the protection scope of the present invention is not limited hereto, but is determined by the appended claims. Within the scope of the technical concept of the present invention, various simple variations of the technical solutions of the present invention can be made, and these simple variations are all within the protection scope of the present invention.

[0064] It needs to be further indicated that the various specific technical features described in the following embodiments can be combined in any appropriate manner where there is no contradiction. To avoid an unnecessary repetition, the possible combinations of the present invention will not be described separately.

[0065] In addition, different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the ideas of the present invention. The technical solution formed therefrom belongs to a part of the original disclosure of the present description, and meanwhile also falls within the protection scope of the present invention, but should not be considered as new contents that have not been disclosed or expected herein, unless those skilled in the art believe that the combination is obviously unreasonable.

[0066] In the context of the present description, except for the explicitly stated contents, any unmentioned matter is directly applicable to those known in the art without requiring any change.

[0067] All the publications, patent applications, patents and other reference literatures mentioned in the present description are incorporated herein by reference. Unless otherwise defined, all the technical and scientific terms used in the present description have the meanings conventionally understood by those skilled in the art. In case of conflict, the definitions in the present description shall prevail.

[0068] When materials, substances, methods, steps, devices, or parts etc. are derived in the present description using the prefix “known to those skilled in the art”, “prior art”, or similar terms, the objects derived from the prefix cover those conventionally used in the art at the time of filing of the present application, and also include those that are not commonly used currently but will become applicable for similar purposes as generally recognized in the art.

[0069] Without specification, all percentages, parts, ratios and the like mentioned in the present description are based on weight, unless the use of weight as a basis does not conform to the conventional understanding of those skilled in the art; the units of temperature are all ° C., the pressure is a gauge pressure, and the space velocity as mentioned is the liquid hourly space velocity LHSV.

[0070] None of the endpoints and the values of the ranges disclosed herein is limited to the precise ranges or values, and these ranges or values should be understood to include the values close to these ranges or values. Value ranges between endpoint values of each range, between endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new value ranges, which should be considered as specifically disclosed herein. In the following text, various technical solutions can be combined with each other in principle to obtain new technical solutions, which should also be considered as specifically disclosed herein.

Test Methods and Standards Involved in the Embodiments of the Present Invention

[0071] 1. in the present invention, the composition of the catalyst is analyzed by ICP (Inductive Coupled Plasma Emission Spectrometer) and XRF (X-ray fluorescence) methods. The composition ratio of Group VIB metal oxides is determined using XPS (X-ray photoelectron spectroscopy). The ICP test condition is: Varian 700-ES series XPS spectrometer. The XRF test condition is: Rigaku ZSX 100e XRF spectrometer. The XPS test condition is: Perkin Elmer PHI 5000C ESCA X-ray photoelectron spectrometer, use of Mg K excitation light source, operating voltage of 10 kV, current of 40 mA, vacuum degree of 4.0×10.sup.−8 Pa.

[0072] 2. in the present invention, the composition of the feedstock oil and the lightening product is determined by gas chromatography. The chromatographic model is Agilent 7890A, equipped with a FID detector, and a FFAP capillary chromatographic column for separation. The chromatographic column uses programmed heating with an initial temperature of 90° C., which is maintained for 15 minutes, and then is heated to 220° C. at a rate of 15° C./minute and maintained for 45 minutes. GC-MS and GC-FID methods are used to analyze the content of tetracyclic and more aromatics in hydrocracking products and realize a quantitative analysis of superheavy aromatics of pyrene (tetracyclic) to coronene (heptacyclic).

[0073] 3. in the present invention, the method for determining the pore spaciousness index is as follows: loading a specific hydrogen-type 12-membered ring zeolite with 0.1-0.5 wt % of platinum or palladium noble metal for the hydrocracking reaction of butyl cyclohexane, and analyzing the molar ratio of isobutane to n-butane in the product, which is the pore spaciousness index of this 12-membered ring zeolite. This spaciousness index can be used to characterize the broadness degree of different 12-membered ring zeolite pores.

[0074] The calculation bases of main result data involved in the embodiments of the present invention are as follows:

[0075] 1. the formula for calculating the total conversion (single-pass conversion of fractions above 200° C.) is:

[00001]$\mathrm{total}\mathrm{conversion}\left(\mathrm{wt}\%\right)=\frac{\begin{array}{c}\mathrm{amount}\mathrm{of}\mathrm{fractions}\mathrm{above}\\ 200°C.\mathrm{in}\mathrm{the}\mathrm{raw}\\ \mathrm{material}-\mathrm{amount}\mathrm{of}\\ \mathrm{fractions}\mathrm{above}200°C.\mathrm{in}\\ \mathrm{the}\mathrm{product}\end{array}}{\begin{array}{c}\mathrm{amount}\mathrm{of}\mathrm{fractions}\mathrm{above}\\ 200°C.\mathrm{in}\mathrm{the}\mathrm{raw}\mathrm{material}\end{array}}\times 100\%$

[0076] 2. the formula for calculating the total selectivity for chemical raw materials is:

[00002]$\mathrm{total}\mathrm{selectivity}\mathrm{for}\mathrm{chemical}\mathrm{raw}\mathrm{materials}\left(\mathrm{wt}\%\right)=\frac{\begin{array}{c}\mathrm{amount}\mathrm{of}C6-C10\mathrm{light}\mathrm{hydrocarbons}\mathrm{in}\mathrm{the}\mathrm{product}+\\ \mathrm{amount}\mathrm{of}C2-C5\mathrm{light}\mathrm{hydrocarbons}\mathrm{in}\mathrm{the}\mathrm{product}\end{array}}{\begin{array}{c}\mathrm{amount}\mathrm{of}\mathrm{fractions}\mathrm{above}200°C.\mathrm{in}\mathrm{the}\mathrm{raw}\mathrm{material}-\\ \mathrm{amount}\mathrm{of}\mathrm{fractions}\mathrm{above}200°C.\mathrm{in}\mathrm{the}\mathrm{product}\end{array}}\times 100\%$

[0077] 3. activity attenuation rate of online operation for 200 hours:

[00003]$200h\mathrm{activity}\mathrm{attenuation}\mathrm{rate}\left(\mathrm{wt}\%\right)=\frac{\begin{array}{c}\mathrm{total}\mathrm{conversion}\left(\mathrm{TOS}=24h\right)-\\ \mathrm{total}\mathrm{conversion}\left(\mathrm{TOS}=200h\right)\end{array}}{\mathrm{total}\mathrm{conversion}\left(\mathrm{TOS}=24h\right)}$

[0078] Raw materials involved in the embodiment portion of the present invention:

[0079] 1. to illustrate the effects of the present invention, two representative feedstock oils are provided. The composition of the feedstocks is shown in Table 1. Feedstock oil 1 and Feedstock oil 2 are hydrotreated light cycle oil.

[0080] 2. the raw materials involved in the examples and the comparative examples of the present invention, including but not limited to the raw materials of catalysts, are all commercially available.

TABLE-US-00001 TABLE 1 Feedstock Feedstock oil 1 oil 2 density (4° C.) 0.91 0.92 sulfur (wtppm) 93 56 nitrogen (wtppm) 14.3 7.4 non-aromatics (wt) 25.60 17.60 monocyclic aromatics (wt %) 50.08 70.27 polycyclic aromatics (wt %) 24.32 12.13 initial boiling point 195 157  5% 206 179 10% 216 188 30% 245 223 50% 266 242 70% 336 263 90% 351 285 end boiling point 365 325 fractions > 200° C. (wt %) 97 80

Comparative Example 1

[0081] Hydrogen-type β zeolite is selected from the hydrogen-type β zeolite of SINOPEC CATALYST DIVISION, which has a silica-to-alumina ratio (SAR) of 50.5 and a pore spaciousness index of 16.5. Its transmission electron microscope (TEM) micrograph is shown in FIG. 1. After hydrogen-type β zeolite and pseudoboehmite were fully mixed, they were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 550° C. for 4 hours, to obtain a desired catalyst carrier. A bimetallic aqueous solution was formulated with nickel nitrate and ammonium tungstate, and the above catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 120° C. and then calcination in an air atmosphere at 500° C. for 2 hours, a catalyst precursor was obtained. The obtained catalyst precursor was reduced to 450° C. under a hydrogen condition and maintained for 4 hours to obtain the hydrocracking catalyst C0 which, based on parts by weight, consisted of: 3.5 parts of Ni-12.5 parts of WO.sub.x/62 parts of β zeolite-22 parts of Al.sub.2O.sub.3 as balance, wherein x was 2.43.

[0082] Feedstock 1 was used as the feedstock oil. The reaction conditions were: temperature of 390° C., pressure of 8.5 MPa, LHSV of 1.0 hour.sup.−1, hydrogen-oil volume ratio of 3000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 93.20% and the total selectivity of chemical raw materials was 89.77%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was 81.59%, and the total selectivity of chemical raw materials was 83.23%. The activity attenuation rate of the catalyst at 200 h was 12.46%.

[0083] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.55% (see Table 3).

[Example 1] Preparation of Layered MWW-Type Zeolite

[0084] The layered MWW-type zeolite of the present invention is selected from the SRZ-21 zeolite of SINOPEC CATALYST DIVISION, and the specific preparation is as follows (according to Example 1 of the description of CN101121524A):

[0085] 6.1 g of sodium aluminate (Al.sub.2O.sub.3 content=42.0 wt %) was dissolved in 288 g of water, and 1.0 g of sodium hydroxide was added to dissolve it. Then under stirring, 34.0 g of hexahydropyridine was added, 60 g of solid silica and 5.5 g of trimethylsilyl chloride were then added. The reactants had material ratios(molar ratios) as follows: [0086] SiO.sub.2/Al.sub.2O.sub.3=40 [0087] NaOH/SiO.sub.2=0.025 [0088] trimethylsilyl chloride/SiO.sub.2=0.05, [0089] hexahydropyridine/SiO.sub.2=0.50, [0090] H.sub.2O/SiO.sub.2=16

[0091] After stirred homogeneously, the reaction mixture was charged into a stainless steel reactor and allowed to crystallize at 135° C. for 50 hours under stirring. Then the reaction mixture was discharged, filtered, washed, dried to give a SRZ-21 zeolite. The chemical analysis gave a molar ratio of SiO.sub.2/Al.sub.2O.sub.3 of 42.1.

[0092] Solid .sup.29Si MAS NMR spectrum was measured on a sample of the dried product, and the .sup.29Si MAS NMR spectrum exhibited a nuclear magnetic resornance peak at 15.1 ppm. Its X-ray diffraction data are shown in the Table 2 below, having MWW structural features.

TABLE-US-00002 TABLE 2 d-spacing (Å) I/Io 12.36 100 10.98 42 9.31 23 6.86 26 6.15 21 5.54 19 4.46 39 3.99 50 3.40 86

[0093] The above SRZ-21 zeolite has a SAR of 42.1. FIG. 2 is a TEM micrograph of the SRZ-21 zeolite. It can be observed that the SRZ-21 zeolite has an obvious lamellar structure, wherein the single-layer MWW structure has a lamellar thickness of 2.6-2.7 nm, and there are also a small amount of double- or triple-layer MWW structures, with a lamellar thickness of about 5-9 nm.

Example 2

[0094] The hydrogen-type β zeolite raw material is the same as β zeolite in Comparative Example 1;

[0095] The layered MWW-type zeolite is selected from the SRZ-21 zeolite prepared in Example 1.

[0096] After the above hydrogen-type β zeolite, SRZ-21 zeolite and pseudoboehmite were fully mixed, they were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 530° C. for 2 hours, to obtain a desired catalyst carrier. A bimetallic aqueous solution was formulated with nickel nitrate and ammonium tungstate, and the above catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 90° C. and then calcination in an air atmosphere at 500° C. for 2 hours, a catalyst precursor was obtained. The obtained catalyst precursor was reduced to 450° C. under a hydrogen condition and maintained for 4 hours, which could obtain the hydrocracking catalyst C1 of the present invention. Based on parts by weight, it consisted of: 3.5 parts of Ni-12.5 parts of WO.sub.x/152 parts of β zeolite-10 parts of SRZ-21-22 parts of Al.sub.2O.sub.3 as balance, wherein x was 2.41.

[0097] Feedstock 1 was used as the feedstock oil. The reaction conditions were: temperature of 375° C., pressure of 8.5 MPa, LHSV of 1.0 hour.sup.−1, hydrogen-oil volume ratio of 3000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 93.81% and the total selectivity of chemical raw materials was 90.05%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was 91.65%, and the total selectivity of chemical raw materials was 86.41%. The activity attenuation rate of the catalyst at 200 h was 2.30%.

[0098] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.27%.

Example 3

[0099] The hydrogen-type β zeolite raw material is the same as β zeolite in Comparative Example 1;

[0100] The layered MWW-type zeolite is selected from the SRZ-21 zeolite prepared in Example 1.

[0101] After the hydrogen-type β zeolite, SRZ-21 zeolite and pseudoboehmite were fully mixed, they were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 530° C. for 2 hours, to obtain a desired catalyst carrier. A trimetallic aqueous solution was formulated with cobalt oxalate, ammonium tungstate and ammonium molybdate, and the catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 90° C. and then calcination in an air atmosphere at 500° C. for 2 hours, a catalyst precursor was obtained. The obtained catalyst precursor was reduced to 480° C. under a hydrogen condition and maintained for 6 hours, which could obtain the hydrocracking catalyst C2 of the present invention. Based on parts by weight, it consisted of: 1.3 parts of Co-5.8 parts of WO.sub.x1-6.7 parts of MoO.sub.x2/35 parts of β zeolite-15 parts of SRZ-21-36.2 parts of Al.sub.2O.sub.3 as balance, wherein x1 was 2.55 and x2 was 2.30.

[0102] Feedstock 1 was used as the feedstock oil. The reaction conditions were: temperature of 390° C., pressure of 8.5 MPa, LHSV of 1.0 hour.sup.−1, hydrogen-oil volume ratio of 3000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 94.23% and the total selectivity of chemical raw materials was 91.45%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was 92.61%, and the total selectivity of chemical raw materials was 88.55%. The activity attenuation rate of the catalyst at 200 h was 1.72%.

[0103] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.09%.

Example 4

[0104] The hydrogen-type β zeolite raw material is the same as β zeolite in Comparative Example 1;

[0105] The layered MWW-type zeolite is selected from the SRZ-21 zeolite prepared in Example 1.

[0106] After the hydrogen-type β zeolite, SRZ-21 zeolite and pseudoboehmite were fully mixed, they were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 530° C. for 2 hours, to obtain a desired catalyst carrier. A bimetallic aqueous solution was formulated with zinc chloride and ammonium molybdate, and the catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 100° C. and then calcination in an air atmosphere at 480° C. for 3 hours, a catalyst precursor was obtained. The obtained catalyst precursor was reduced to 500° C. under a hydrogen condition and maintained for 4 hours, which could obtain the hydrocracking catalyst C3 of the present invention. Based on parts by weight, it consisted of: 3.8 parts of Zn-13.5 parts of MoO.sub.x/65 parts of β zeolite-5 parts of SRZ-21-12.7 parts of Al.sub.2O.sub.3 as balance, wherein x was 2.09.

[0107] Feedstock 1 was used as the feedstock oil. The reaction conditions were: temperature of 370° C., pressure of 8.5 MPa, LHSV of 1.0 hour.sup.−1, hydrogen-oil volume ratio of 3000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 95.07% and the total selectivity of chemical raw materials was 91.32%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was 93.84%, and the total selectivity of chemical raw materials was 89.47%. The activity attenuation rate of the catalyst at 200 h was 1.29%.

[0108] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.20%.

EXAMPLE 5

[0109] The hydrogen-type β zeolite raw material is the same as β zeolite in Comparative Example 1;

[0110] The layered MWW-type zeolite is selected from the SRZ-21 zeolite prepared in Example 1.

[0111] After the hydrogen-type β zeolite, SRZ-21 zeolite and pseudoboehmite were fully mixed, they were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 550° C. for 3 hours, to obtain a desired catalyst carrier. Bismuth nitrate was dissolved in water, loaded on the catalyst carrier by the incipient wetness impregnation method, dried at 110° C. and then calcined in an air atmosphere at 400° C. for 3 hours. A trimetallic solution was formulated with nickel oxalate, zinc acetate, and ammonium molybdate, and the above bismuth-loaded catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 100° C. and then calcination in an air atmosphere at 500° C. for 3 hours, a catalyst precursor was obtained. The catalyst precursor was reduced to 450° C. under a hydrogen condition and maintained for 4 hours, which could obtain the hydrocracking catalyst C4 of the present invention. Based on parts by weight, it consisted of: 0.8 parts of Zn-3.5 parts of Ni-1.5 parts of Bi-13.5 parts of MoO.sub.x/35 parts of β zeolite-5 parts of SRZ-21-40.7 parts of Al.sub.2O.sub.3 as balance, wherein x was 2.15.

[0112] Feedstock 1 was used as the feedstock oil. The reaction conditions were: temperature of 390° C., pressure of 8.5 MPa, LHSV space velocity of 1.0 hour.sup.−1, hydrogen-oil volume ratio of 3000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 93.56% and the total selectivity of chemical raw materials was 89.99%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was 90.27%, and the total selectivity of chemical raw materials was 85.73%. The activity attenuation rate of the catalyst at 200 h was 3.52%.

[0113] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.16%.

Example 6

[0114] Hydrogen-type β zeolite is selected from the hydrogen-type β zeolite of SINOPEC CATALYST DIVISION, which has a SAR of 82.5 and a pore spaciousness index of 15.8.

[0115] The layered MWW-type zeolite is selected from the SRZ-21 zeolite prepared in Example 1.

[0116] After the hydrogen-type β zeolite, SRZ-21 zeolite and porous silica gel powder (SiO.sub.2 content of greater than 99.9 wt %) were fully mixed, an ammonia-type silica sol with 30% of SiO.sub.2 on a dry basis was added. They were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 600° C. for 4 hours, to obtain a desired catalyst carrier. Stannic chloride was dissolved in water, loaded on the catalyst carrier by the incipient wetness impregnation method, dried at 110° C. and then calcined in an air atmosphere at 400° C. for 2 hours. A bimetallic aqueous solution was formulated with palladium chloride and chloroplatinic acid, and the above tin-loaded catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 110° C. and then calcination in an air atmosphere at 500° C. for 2 hours, a catalyst precursor was obtained. The obtained catalyst precursor was reduced to 400° C. under a hydrogen condition and maintained for 4 hours, which could obtain the desired hydrocracking catalyst C5. Based on parts by weight, it consisted of: 0.05 parts of Pt-0.15 parts of Pd-1.4 parts of Sn/65 parts of β zeolite-5 parts of SRZ-21-28.4 parts of SiO.sub.2 as balance.

[0117] Feedstock 2 was used as the feedstock oil. The reaction conditions were: temperature of 360° C., pressure of 6.0 MPa, LHSV of 1.2 hour.sup.−1, hydrogen-oil volume ratio of 2000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 96.35% and the total selectivity of chemical raw materials was 81.73%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was 95.09%, and the total selectivity of chemical raw materials was 80.92%. The activity attenuation rate of the catalyst at 200 h was 1.31%.

[0118] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.07%.

Example 7

[0119] The hydrogen-type β zeolite raw material is the same as β zeolite in Comparative Example 1;

[0120] The layered MWW-type zeolite is selected from the SRZ-21 zeolite prepared in Example 1.

[0121] After the above hydrogen-type β zeolite, SRZ-21 zeolite and pseudoboehmite were fully mixed, they were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 530° C. for 2 hours, to obtain a desired catalyst carrier. Stannic chloride was dissolved in water, loaded on the catalyst carrier by the incipient wetness impregnation method, dried at 110° C. and then calcined in an air atmosphere at 400° C. for 2 hours. A bimetallic aqueous solution was formulated with nickel nitrate and ammonium tungstate, and the above tin-loaded catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 90° C. and then calcination in an air atmosphere at 500° C. for 2 hours, a catalyst precursor was obtained. The obtained catalyst precursor was reduced to 450° C. under a hydrogen condition and maintained for 4 hours, which could obtain the hydrocracking catalyst C6 of the present invention. Based on parts by weight, it consisted of: 3.4 parts of Ni-1.8 parts of Sn-12.3 parts of WO.sub.x/51 parts of β zeolite-9.5 parts of SRZ-21-22 parts of Al.sub.2O.sub.3 as balance, wherein x was 2.45.

[0122] Feedstock 1 was used as the feedstock oil. The reaction conditions were: temperature of 375° C., pressure of 8.5 MPa, LHSV of 1.0 hour.sup.−1, hydrogen-oil volume ratio of 3000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 94.59% and the total selectivity of chemical raw materials was 92.05%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was 92.87%, and the total selectivity of chemical raw materials was 91.23%. The activity attenuation rate of the catalyst at 200 h was 1.82%.

[0123] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.23%.

Comparative Example 2

[0124] The hydrogen-type β zeolite raw material is the same as β zeolite in Comparative Example 1;

[0125] Hydrogen-type MCM-22 zeolite is taken from SINOPEC CATALYST DIVISION; the hydrogen-type MCM-22 zeolite is a typical MWW-type zeolite, which has a particle thickness of about 1.5 μm and a SAR of 45.

[0126] After the above hydrogen-type β zeolite, MCM-22 zeolite and pseudoboehmite were fully mixed, they were kneaded, extruded, dried at 120° C., and then calcined in an air atmosphere at 530° C. for 2 hours, to obtain a desired catalyst carrier. A bimetallic aqueous solution was formulated with nickel nitrate and ammonium tungstate, and the above catalyst carrier was impregnated by the incipient wetness impregnation method. After drying at 90° C. and then calcination in an air atmosphere at 500° C. for 2 hours, a catalyst precursor was obtained. The obtained catalyst precursor was reduced to 450° C. under a hydrogen condition and maintained for 4 hours, which could obtain the hydrocracking catalyst C7 of the present invention. Based on parts by weight, it consisted of: 3.5 parts of Ni-12.5 parts of WO.sub.x/52 parts of β zeolite-10 parts of MCM-22 parts of Al.sub.2O.sub.3 as balance, wherein x was 2.40.

[0127] Feedstock 1 was used as the feedstock oil. The reaction conditions were: temperature of 375° C., pressure of 8.5 MPa, LHSV of 1.0 hour.sup.−1, hydrogen-oil volume ratio of 3000. After a stable operation for 24 hours, samples were taken for analysis and calculation, wherein the total conversion was 90.15% and the total selectivity of chemical raw materials was 87.08%. The reaction condition and the feedstock remained unchanged, and after 200 hours of online operation, samples were taken for analysis and calculation, wherein the total conversion was and the total selectivity of chemical raw materials was 81.05%. The activity attenuation rate of the catalyst at 200 h was 16.10%.

[0128] After further analysis, the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation was 0.53%. Data of the content of tetracyclic and more superheavy aromatics in the hydrocracking product of 200 hours of online operation obtained in all the [Comparative Examples] and [Examples 2-7] are summarized in Table 3.

TABLE-US-00003 TABLE 3 Content of superheavy aromatics, Catalyst % C0 0.55 C1 0.27 C2 0.09 C3 0.20 C4 0.16 C5 0.07 C6 0.23 C7 0.53