A two-stage hydrocracking method for kerosene

Abstract

The present invention discloses a method for two-stage hydrocracking of kerosene. The method comprises: (1) in the presence of hydrogen, kerosene is contacted with a shape-selective cracking catalyst for shape-selective cracking reaction; wherein the mass content of C7+ n-alkanes in the effluent of the shape-selective cracking reaction is controlled below 3.0%; (2) the effluent of the shape-selective cracking reaction in step (1) is separated and fractionated to obtain ethylene feedstock, reforming feedstock and tail oil; (3) in the presence of hydrogen, the tail oil in step (2) is contacted with an isohydrocarbon conversion catalyst for isohydrocarbon conversion reaction, and after separation and fractionation, ethylene feedstock and reforming feedstock are obtained. This method uses kerosene as a raw material for hydrocracking to produce chemical raw materials, and can greatly improve the yield and quality of chemical raw materials, namely ethylene feedstock and reforming feedstock.

Description

Technical Field

[0001] The present invention belongs to the field of hydrocarbon oil hydrocracking, and particularly relates to a two-stage kerosene hydrocracking method. Background Art

[0002] The global refining capacity is growing slowly, and the scale of refineries continues to increase. The production route of light raw materials has the advantages of high product yield, low cost, less project investment, low energy consumption, and less pollution.

[0003] CN201580070326.4 discloses a method for preparing LPG and BTX, including: a) subjecting a mixed hydrocarbon stream to a first hydrocracking in the presence of a first hydrocracking catalyst to prepare a first hydrocracking product stream; b) separating the first hydrocracking product stream to provide at least one light hydrocarbon stream containing at least C2 and C3 hydrocarbons, an intermediate hydrocarbon stream composed of C4 and / or C5 hydrocarbons, and a heavy hydrocarbon stream containing at least C6+ hydrocarbons, and c) subjecting the heavy hydrocarbon stream to a second hydrocracking in the presence of a second hydrocracking catalyst to prepare a second hydrocracking product stream containing BTX, wherein the second hydrocracking is more severe than the first hydrocracking, d) wherein, in the presence of a C4 hydrocracking catalyst, at least part of the intermediate hydrocarbon stream is subjected to C4 hydrocracking to prepare a C4 hydrocracking product stream, and the C4 hydrocracking is optimized for converting C4 hydrocarbons into C3 hydrocarbons.

[0004] CN201480037272.7 discloses a method for producing light olefin hydrocarbon compounds from a hydrocarbon raw material, including the following steps: (a) feeding the hydrocarbon raw material to a reaction zone for ring opening; (b) separating the reaction product generated from the reaction zone into an overhead stream and a side stream; (c) feeding the side stream from (b) to a gasoline hydrocracker (GHC) unit; (d) separating the reaction product of the GHC in step (c) into an overhead stream containing hydrogen, methane, ethane, and liquefied petroleum gas and a stream containing aromatic hydrocarbon compounds and a small amount of hydrogen and non-aromatic hydrocarbon compounds; (e) feeding the overhead stream from the gasoline hydrocracker (GHC) unit to a steam cracker unit.

[0005] The above methods are mainly used for producing LPG and BTX. At the same time, when producing ethylene raw materials, the content of normal paraffins in the ethylene raw materials is low, which will also result in a low yield of trienes in the steam cracking to ethylene unit. Therefore, it is of great significance to develop a hydrocracking method suitable for producing high-quality chemical raw materials from kerosene. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the object of the present invention is to provide a two-stage kerosene hydrocracking method. This method uses kerosene as a raw material for hydrocracking to produce chemical raw materials, and can greatly improve the yield and quality of chemical raw materials (i.e., ethylene raw materials and reforming raw materials).

[0007] The present invention provides a two-stage hydrocracking method for kerosene. The method uses kerosene as a raw material to hydrocrack and produce ethylene raw materials and reforming raw materials. The method includes:

[0008] (1) In the presence of hydrogen, kerosene is contacted with a shape-selective cracking catalyst for a shape-selective cracking reaction; wherein the mass content of C7 normal paraffins in the effluent of the shape-selective cracking reaction is controlled to be below 3.0%; + The mass content of C7 normal paraffins is controlled to be below 3.0%;

[0009] (2) The effluent of the shape-selective cracking reaction in step (1) is separated and fractionated to obtain ethylene raw materials, reforming raw materials and tail oil;

[0010] (3) In the presence of hydrogen, the tail oil in step (2) is contacted with an isohydrocarbon conversion catalyst for an isohydrocarbon conversion reaction, and after separation and fractionation, ethylene raw materials and reforming raw materials are obtained.

[0011] According to the present invention, in step (1), the shape-selective cracking catalyst can be one or more catalysts.

[0012] According to the present invention, the composition of the shape-selective cracking catalyst in step (1), based on the mass of the catalyst, includes:

[0013] a) 55% to 72% of molecular sieve; the molecular sieve is selected from one or more of ZSM-5 molecular sieve, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 molecular sieves, preferably ZSM-5 molecular sieve;

[0014] b) At least one selected from the metals of Group VIB and Group VIII, calculated as oxides, in an amount of 3% to 18%;

[0015] c) 1% to 13% of binder;

[0016] d) 8% to 37% of macroporous alumina.

[0017] According to the present invention, preferably, component a) is ZSM-5 molecular sieve. Preferably, the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 40 to 60.

[0018] According to the present invention, preferably, the metal of Group VIB in component b) is molybdenum and / or tungsten. The metal of Group VIII in component b) is cobalt and / or nickel.

[0019] According to the present invention, preferably, the binder in component c) can be a conventional binder; such as one or more of alumina, silica, titanium oxide, etc., preferably small-pore alumina. The properties of the small-pore alumina are as follows: specific surface area is 240 to 300 m 2 / g, with a pore volume of 0.3 - 0.5 mL / g and an average pore diameter of 3 - 6 nm.

[0020] According to the present invention, preferably, the properties of the macroporous alumina in component d) are as follows: the specific surface area is 300 - 380 m 2 / g, with a pore volume of 0.8 - 1.2 mL / g and an average pore diameter of 8 - 20 nm.

[0021] According to the present invention, preferably, the composition of the shape - selective cracking catalyst in step (1), based on the mass of the catalyst, includes:

[0022] a) 55% - 72% of ZSM - 5 molecular sieve;

[0023] b) 5% - 15% of molybdenum and / or tungsten, and 2% - 5% of cobalt and / or nickel, calculated as oxides;

[0024] c) 1% - 13% of binder;

[0025] d) 8% - 37% of macroporous alumina.

[0026] According to the present invention, the specific surface area of the shape - selective cracking catalyst in step (1) is 300 - 500 m 2 / g, with a pore volume of 0.30 - 0.50 mL / g.

[0027] According to the present invention, the preparation method of the shape - selective cracking catalyst in step (1) can be prepared according to the conventional methods in the art. First, the molecular sieve and the binder are shaped, then dried and calcined, and then the metal components are loaded; the preferred method for loading the metal components is the impregnation method.

[0028] According to the present invention, preferably, the mass content of C7 + n - paraffin in step (1) is controlled at 0.5 wt% - 3 wt%. As a non - restrictive example, the mass content of C7 + [[ID=3S]]n - paraffin in step (1) can be 0.1 wt%, 0.8 wt%, 1.2 wt%, 1.8 wt%, 2 wt%, 2.5 wt%, etc.

[0029] According to the present invention, the reaction pressure of the shape - selective cracking reaction in step (1) is 2.0 - 6.0 MPa, preferably 3.0 - 5.0 MPa.

[0030] According to the present invention, the reaction conditions of the shape - selective cracking reaction in step (1) are as follows: the average reaction temperature is 250 - 450 °C, preferably 300 - 400 °C; the liquid hourly space velocity is 0.1 - 15.0 h -1 , preferably 1.0 - 5.0 h -1; The hydrogen-to-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0031] According to the present invention, the mass content of n-alkanes in the kerosene in step (1) is 10% to 60%, preferably 20% to 50%. The kerosene can be straight-run kerosene, coker kerosene and other kerosene fractions with a relatively high n-alkane content.

[0032] According to the present invention, the mass content of cyclic hydrocarbons in the kerosene in step (1) is 30% to 80%, and the cyclic hydrocarbons are the sum of naphthenes and aromatics.

[0033] According to the present invention, the initial boiling point of the kerosene in step (1) is 100°C to 200°C, preferably 130°C to 180°C; the final boiling point is 210°C to 300°C, preferably 220°C to 280°C; the initial boiling point of the kerosene is at least 30°C to 150°C lower than the final boiling point, preferably 50°C to 100°C lower.

[0034] According to the present invention, the kerosene in step (1) may contain impurities such as sulfur, nitrogen, etc. According to actual needs, a hydrofining catalyst can be arranged upstream of the shape-selective cracking catalyst to remove impurities such as sulfur, nitrogen, etc. Among them, the nitrogen content in the reaction stream in contact with the shape-selective cracking catalyst is preferably below 50 mg / kg, more preferably below 20 mg / kg. The hydrofining catalyst can adopt a conventional hydrofining catalyst, which is mainly used for hydrodesulfurization, denitrification and other impurities. The hydrofining catalyst includes a carrier and a hydrogenation active metal, wherein the carrier is an inorganic refractory oxide, generally selected from one or more of alumina, amorphous silica-alumina, silica or titanium oxide, etc.; the hydrogenation active metal includes Group VIB and / or Group VIII metal components. In the hydrofining catalyst, Group VIB is preferably selected from tungsten and / or molybdenum, and its content in the catalyst based on the mass of the oxide is 5% to 30%, preferably 10% to 20%, and Group VIII is preferably selected from nickel and / or cobalt, and its content in the catalyst based on the mass of the oxide is 1% to 6%, preferably 1.5% to 5%.

[0035] According to the present invention, in the product obtained in step (3), the mass ratio of the C6-C8 monocyclic cyclic hydrocarbons to the total cyclic hydrocarbon mass in the raw material is 0.30 to 0.50, preferably 0.38 to 0.45. The raw material is kerosene.

[0036] According to the present invention, the isomerization hydrocarbon conversion catalyst in step (3) can be one or more catalysts. The isomerization hydrocarbon conversion catalyst in step (3) has the function of ring-opening cracking of polycyclic cyclic hydrocarbons, selectively cracking the side chains of isomerization hydrocarbons or cyclic hydrocarbons and retaining monocyclic cyclic hydrocarbons.

[0037] According to the present invention, preferably, in step (3), the isomerization hydrocarbon conversion catalyst, based on the mass of the catalyst, comprises:

[0038] k) The hydrogenation component content is 5 wt% to 40 wt%, preferably 10 wt% to 20 wt% in terms of oxide;

[0039] l) The cracking component content is 20 wt% to 80 wt%, preferably 30 wt% to 70 wt%;

[0040] m) The binder content is 5 wt% to 75 wt%, preferably 10 wt% to 50 wt%.

[0041] According to the present invention, preferably, the hydrogenation component in component k) includes at least one of Group VIB and / or Group VIII metals, metal oxides, and metal sulfides. Preferably, the hydrogenation component in component k) includes at least one of metals, metal oxides, and metal sulfides of iron, chromium, molybdenum, tungsten, cobalt, and nickel.

[0042] According to the present invention, preferably, the cracking component in component l) includes an acidic molecular sieve, preferably at least one of Beta zeolite and Y zeolite, more preferably Beta zeolite.

[0043] According to the present invention, preferably, the binder in component m) is alumina and / or silica.

[0044] According to the present invention, the isomerization hydrocarbon conversion catalyst in step (3) can be prepared according to the conventional methods in the art. First, the molecular sieve and the binder are shaped, then dried and calcined, and then the metal components are loaded; the loading of metal components preferably uses the impregnation method.

[0045] According to the present invention, in step (3), the reaction pressure of the isomerization hydrocarbon conversion reaction is 1 to 5 MPa, preferably 2 to 4 MPa. Preferably, the reaction pressure of the isomerization hydrocarbon conversion reaction in step (3) is lower than the pressure of the shape-selective cracking reaction described in step (1), preferably 0.5 MPa to 2 MPa lower, preferably 1.0 MPa to 1.5 MPa lower.

[0046] According to the present invention, the reaction conditions of the isomerization hydrocarbon conversion reaction in step (3) are as follows: the average reaction temperature is 250 to 450 °C, preferably 300 to 400 °C; the liquid hourly space velocity is 0.1 to 15.0 h -1 , preferably 1.0 to 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0047] According to the present invention, preferably, the effluent of the isomerization hydrocarbon conversion reaction in step (3) is subjected to supplementary hydrorefining.

[0048] According to the present invention, the effluent of the isomer hydrocarbon conversion reaction in step (3) is separated and fractionated to obtain ethylene feedstock and reforming feedstock. Preferably, the separation and fractionation system for the effluent of the isomer hydrocarbon conversion reaction in step (3) can share a set of system with the separation and fractionation system for the effluent of the shape-selective cracking reaction in step (2).

[0049] According to the present invention, in step (3) and / or step (2), the reforming feedstock is heavy naphtha. The ethylene feedstock in step (3) and / or step (2) includes ethane, propane, butane and light naphtha. Heavy naphtha can be used as reforming feedstock to produce BTX. The ethylene feedstock can be steam cracked to produce light olefins. Light olefins refer to olefins with four or less carbon atoms, especially ethylene, propylene and butadiene.

[0050] According to the present invention, preferably, the reforming feedstock in step (3) and / or step (2) is subjected to supplementary hydrofining.

[0051] Petroleum hydrocarbons have a complex composition, mainly including paraffins, naphthenes and aromatics. High-quality ethylene feedstock is small-molecule normal paraffins, and reforming feedstock is monocyclic naphthenes and aromatics. The inventors have found through research that kerosene feedstock can pass through the shape-selective cracking of straight-chain paraffins, the ring-opening cracking of polycyclic cyclic hydrocarbons, and the selective hydrocracking of long side chains on isomer hydrocarbons or cyclic hydrocarbons in sequence to retain monocyclic cyclic hydrocarbons as much as possible, and can selectively generate small-molecule normal paraffins, so as to efficiently enrich small-molecule normal paraffins in the ethylene feedstock, and at the same time retain monocyclic cyclic hydrocarbons in the reforming feedstock as much as possible to achieve efficient enrichment of high-quality reforming feedstock, which can achieve the purpose of greatly improving the yield and quality of chemical raw materials, and thus complete the present invention.

[0052] Compared with the prior art, the present invention has the following beneficial technical effects:

[0053] (1) In the two-stage hydrocracking method of kerosene of the present invention, kerosene contacts and reacts with a shape-selective cracking catalyst containing macroporous alumina, which can effectively remove impurities such as sulfur and nitrogen in the reactants, and at the same time selectively crack the normal paraffins in the feedstock and the long straight chains of isoparaffins and naphthenes containing long straight chains to generate small-molecule normal paraffins, and control the content of C7 + normal paraffins in the reaction effluent to be below 3%; then contact and react with an isomer hydrocarbon conversion catalyst, mainly to crack the polycyclic cyclic hydrocarbons to open the rings and retain the monocyclic cyclic hydrocarbons and further break the side chains in each hydrocarbon to generate small-molecule hydrocarbons. In this way, a large amount of the straight-chain alkanes in the feedstock can be converted into gas and light naphtha components, that is, enriched in the ethylene feedstock, while the monocyclic cyclic hydrocarbons are retained in the heavy naphtha fraction, that is, enriched in the reforming feedstock. Through simple fractionation, the efficient separation of alkanes and cyclic hydrocarbons can be achieved, increasing the production of high-quality ethylene cracking feedstock while improving the quality of heavy naphtha as a catalytic reforming feed.

[0054] (2) The content of monocyclic cyclic hydrocarbons in the heavy naphtha obtained by the method of the present invention is high. As the feedstock for the catalytic reforming unit, the alkane cyclization and dehydrogenation unit in the catalytic reforming unit can be omitted, which can greatly reduce the investment and energy consumption of the catalytic reforming unit. At the same time, since the hydrocracking reaction follows the carbocation reaction mechanism, the side chain breaking reaction of cyclic hydrocarbons with more than C9 can be selectively achieved, so that the C6-C8 cyclic hydrocarbons in the product have a high enrichment degree, and the BTX yield can be greatly increased after catalytic reforming and aromatics extraction.

[0055] (3) The present invention selectively converts the alkanes in kerosene into small molecule alkanes. This process consumes a certain amount of hydrogen, but the light hydrocarbons also have a high hydrogen yield as the raw material for the ethylene unit, and the lower the carbon number, the higher the hydrogen yield. Therefore, most of the hydrogen consumed in the hydrogenation process can be recovered after passing through the ethylene unit. At the same time, the light hydrocarbons as the ethylene raw material can greatly increase the yields of ethylene, propylene and butadiene, and extend the cleaning cycle of the ethylene unit, significantly improving the economic benefits of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a process flow schematic diagram of Examples 1-4;

[0057] Main reference numeral description:

[0058] 1 - Kerosene, 2 - Hydrogen, 3 - Shape-selective cracking reaction zone, 4 - Shape-selective cracking reaction effluent, 5 - Isomer hydrocarbon conversion reaction zone, 6 - Isomer hydrocarbon conversion reaction effluent, 7 - Separator, 8 - Gas-phase stream rich hydrogen gas, 9 - Liquid-phase stream, 10 - Fractionating tower, 11 - Gas fraction, 12 - Light naphtha, 13 - Heavy naphtha, 14 - Tail oil. DETAILED DESCRIPTION OF THE INVENTION

[0059] The functions and effects of the present invention will be further described below through examples, but the following examples do not limit the method of the present invention.

[0060] In the present invention, unless otherwise specified, % are all mass fractions.

[0061] The total volume space velocity in the examples and comparative examples is the ratio of the fresh feed volume to the total volume of the catalyst.

[0062] In the present invention, the shape-selective cracking catalysts in each example are represented by Cat-A plus a number, such as Cat-A1 and Cat-A2. The shape-selective cracking catalysts are prepared by the conventional active metal saturation impregnation method, and the physical and chemical properties of the obtained catalysts are shown in Table 1.

[0063] In the present invention, the isomerization hydrocarbon conversion catalysts in each example are represented by Cat-B plus a number, such as Cat-B1 and Cat-B2. The physical and chemical properties of the catalysts are shown in Table 2. The isomerization hydrocarbon conversion catalysts in each example are prepared by a conventional active metal saturation impregnation method. Among them, the properties of the Beta zeolite used are as follows: the SiO2 / Al2O3 molar ratio is 30, the specific surface area is 350 m 2 / g, and the pore volume is 0.32 cm 3 / g. The properties of the Y zeolite used are as follows: the SiO2 / Al2O3 molar ratio is 15, the specific surface area is 400 m 2 / g, the pore volume is 0.30 cm 3 / g, and the physical and chemical properties of the obtained catalysts are shown in Table 2.

[0064] In the present invention, the feedstock oil in each example uses kerosene as the raw material, and its main properties are shown in Table 3.

[0065] In the present invention, the process flow diagrams of Examples 1 to 4 are as Figure 1 shown. Figure 1 In it, kerosene 1 and hydrogen 2 are mixed and enter the shape-selective cracking reaction zone 3 to contact with the shape-selective cracking catalyst for shape-selective cracking reaction; the shape-selective cracking reaction effluent 4 enters the separator 7, and the separated gas-phase stream rich in hydrogen gas 8 is recycled, and the liquid-phase stream 9 enters the fractionating tower 10 to be fractionated to obtain gas fractions 11 (ethane, propane, and butane), light naphtha 12, heavy naphtha 13, and tail oil 14; the tail oil 14 and hydrogen 2 are mixed and enter the isomerization hydrocarbon conversion reaction zone 5 to contact and react with the isomerization hydrocarbon conversion catalyst; the isomerization hydrocarbon conversion reaction effluent 6 enters the separator 7 for separation and fractionation.

[0066] In the present invention, the properties of the macroporous alumina in each example are: the specific surface area is 350 m 2 / g, the pore volume is 1.0 mL / g, and the average pore diameter is 15 nm. The binder in Table 1 is microporous alumina. The properties of the microporous alumina are: the specific surface area is 260 m 2 / g, the pore volume is 0.4 mL / g, and the average pore diameter is 4 nm.

[0067] In the present invention, the distillation range of the light naphtha is the liquid component with a boiling point less than 60 °C, and the distillation range of the heavy naphtha is 60 - 175 °C.

[0068] In the present invention, the yield of the ethylene raw material refers to the mass ratio of ethane, propane, butane, and light naphtha in the hydrocracking product to the fresh feedstock (kerosene) of the hydrocracking, and the yield of the heavy naphtha refers to the mass ratio of the heavy naphtha in the hydrocracking product to the fresh feedstock of the hydrocracking.

[0069] Examples 1 to 4

[0070] The hydrocracking method described adopts asFigure 1 The process includes the steps of:

[0071] (1) In the presence of hydrogen, kerosene is contacted with a shape-selective cracking catalyst for shape-selective cracking reaction; and the mass content of C7 normal paraffin in the effluent of the shape-selective cracking reaction is controlled; + The mass content of normal paraffin;

[0072] (2) The effluent of the shape-selective cracking reaction in step (1) is separated and fractionated to obtain ethylene feedstock, reforming feedstock and tail oil;

[0073] (3) In the presence of hydrogen, the tail oil in step (3) is contacted with an isohydrocarbon conversion catalyst for isohydrocarbon conversion reaction; the effluent of the isohydrocarbon conversion reaction uses the same set of separation and fractionation system as in step (2);

[0074] The reforming feedstock is heavy naphtha; the ethylene feedstock includes ethane, propane, butane and light naphtha.

[0075] The process conditions and hydrogenation effects of each example are shown in Table 4.

[0076] Comparative Example 1

[0077] The difference from Example 1 is that the feedstock oil is directly contacted with the isohydrocarbon conversion catalyst for reaction. The process conditions and hydrogenation effects in this example are shown in Table 4.

[0078] Comparative Example 2

[0079] The difference from Example 1 is that in step (1), the content of C7 normal paraffin in the reaction effluent is controlled to be 4%. The process conditions and hydrogenation effects in this example are shown in Table 4. + The mass content of normal paraffin is 4%. The process conditions and hydrogenation effects in this example are shown in Table 4.

[0080] Comparative Example 3

[0081] The difference from Example 1 is that in step (1), the shape-selective cracking catalyst used is catalyst Cat-B1. The process conditions and hydrogenation effects in this example are shown in Table 4.

[0082] Table 1 Physicochemical properties of the shape-selective cracking catalyst

[0083] Catalyst Cat-A1 Cat-A2 <![CDATA[Pore volume, cm 3 / g]]> 0.40 0.50 <![CDATA[Specific surface area, m 2 / g]]> 400 300 Particle size, μm 0.8 0.6 Catalyst composition ZSM-5, wt% 65 58 Mo, wt% 15 5 Ni, wt% 2 5 Binder, wt% 3 2 Macroporous alumina, wt% 15 30 <![CDATA[SiO2 / Al2O3 molar ratio of ZSM-5]]> 40 60

[0084] Table 2 Physicochemical properties of the isohydrocarbon conversion catalyst

[0085]

[0086]

[0087] Table 3 Main properties of the feedstock

[0088] Name of feedstock oil Kerosene <![CDATA[Density (20 °C) / kg·m -3 > 788.3 Distillation range / °C (ASTM D86) IBP / 10% 162 / 184 30％ / 50％ 196 / 205 70％ / 90％ 215 / 231 95% / EBP 238 / 246 n-alkane, wt% 24 Cyclic hydrocarbon, wt% 42 Nitrogen content, mg / kg 20

[0089] Table 4 Process Conditions and Hydrogenation Effects of Each Example

[0090]

[0091]

[0092] Continued Table 4

[0093]

[0094] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A two-stage hydrocracking method for kerosene, comprising: (1) In the presence of hydrogen, kerosene is contacted with a shape-selective cracking catalyst for shape-selective cracking reaction; Among them, the mass content of C7 + n-alkanes in the effluent of the shape-selective cracking reaction is controlled below 3.0%; (2) The effluent from the shape-selective cracking reaction in step (1) is separated and fractionated to obtain ethylene feedstock, reforming feedstock and tail oil; (3) In the presence of hydrogen, the tail oil in step (2) is contacted with an isohydrocarbon conversion catalyst for isohydrocarbon conversion reaction, and after separation and fractionation, ethylene feedstock and reforming feedstock are obtained; The reaction pressure of the shape-selective cracking reaction in step (1) is 2.0 - 6.0 MPa; Heavy naphtha is used as reforming feedstock to produce BTX; Ethane, propane, butane and light naphtha are used as ethylene feedstock to produce light olefins; The composition of the shape-selective cracking catalyst in step (1), based on the mass of the catalyst, includes: a) 55% - 72% molecular sieve; the molecular sieve is selected from one or more of ZSM-5 molecular sieve, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 molecular sieves; b) At least one metal selected from Group VIB and Group VIII metals, calculated as oxides, in an amount of 3% - 18%; c) 1% - 13% binder; d) 8% - 37% macroporous alumina; The isohydrocarbon conversion catalyst in step (3), based on the mass of the catalyst, includes: k) The content of the hydrogenation component is 5 wt% - 40 wt%, calculated as oxides; l) The content of the cracking component is 20 wt% - 80 wt%; m) The content of the binder is 5 wt% - 75 wt%; Among them, the cracking component in component l) includes at least one of Beta molecular sieve and Y molecular sieve.

2. The method according to claim 1, characterized in that, The molecular sieve of the shape-selective cracking catalyst in step (1) is ZSM-5 molecular sieve.

3. The method according to claim 1, wherein The composition of the shape-selective cracking catalyst in step (1), based on the mass of the catalyst, includes: a) 55% - 72% ZSM-5 molecular sieve; b) 5% - 15% molybdenum and / or tungsten, and 2% - 5% cobalt and / or nickel, calculated as oxides; c) 1% - 13% binder; d) 8% - 37% macroporous alumina.

4. The method according to claim 2 or 3, characterized in that, The properties of the macroporous alumina described in component d) are as follows: the specific surface area is 300~380 m 2 / g, the pore volume is 0.8~1.2 mL / g, and the average pore diameter is 8~20 nm.

5. The method according to claim 1, wherein The specific surface area of the shape-selective cracking catalyst described in step (1) is 300-500 m 2 / g, and the pore volume is 0.30-0.50 mL / g.

6. The method according to claim 1, characterized in that, C7 in step (1) + The mass content of the n-alkane is controlled to be 0.5 wt% to 3 wt%.

7. The method according to claim 1, wherein The reaction pressure of the shape-selective cracking reaction described in step (1) is 3.0 to 5.0 MPa; and / or, the average reaction temperature is 250 to 450 °C; and / or, the liquid hourly space velocity is 0.1 to 15.0 h -1 ; and / or, the hydrogen-oil volume ratio is 100:1 to 2500:

1.

8. The method according to claim 7, characterized in that The average reaction temperature of the shape-selective cracking reaction described in step (1) is 300-400 °C; and / or, the liquid hourly space velocity is 1.0-5.0 h -1 ; and / or, the hydrogen-oil volume ratio is 400:1-2000:

1.

9. The method according to claim 1, wherein The mass content of normal paraffins in the kerosene in step (1) is 10% - 60%; And / or, the mass content of cyclic hydrocarbons in the kerosene in step (1) is 30% - 80%; And / or, the initial boiling point of the kerosene in step (1) is 100°C - 200°C; the final boiling point is 210°C - 300°C.

10. The method according to claim 1, wherein The mass content of normal paraffins in the kerosene in step (1) is 20% - 50%; And / or, the initial boiling point of the kerosene in step (1) is 130°C - 180°C; the final boiling point is 220°C - 280°C.

11. The method according to claim 1, wherein The isohydrocarbon conversion catalyst in step (3), based on the mass of the catalyst, includes: k) The content of the hydrogenation component is 10 wt% - 20 wt%, calculated as oxides; l) The content of the cracking component is 30 wt% - 70 wt%; m) The content of the binder is 10 wt% - 50 wt%.

12. The method according to claim 11, wherein The hydrogenation component in component k) includes at least one of metals, metal oxides, and metal sulfides of iron, chromium, molybdenum, tungsten, cobalt, and nickel; And / or, the cracking component in component l) includes Beta molecular sieve.

13. The method according to claim 1, wherein In step (3), the reaction pressure of the isoparaffin conversion reaction is 1 to 5 MPa.

14. The method according to claim 13, wherein In step (3), the reaction pressure of the isoparaffin conversion reaction is 2 to 4 MPa.

15. The method according to claim 1 or 13, characterized in that, The reaction pressure of the isoparaffin conversion reaction in step (3) is 0.5 MPa to 2 MPa lower than the pressure of the shape-selective cracking reaction described in step (1).

16. The method according to claim 15, wherein The reaction pressure of the isoparaffin conversion reaction in step (3) is 1.0 MPa to 1.5 MPa lower than the pressure of the shape-selective cracking reaction described in step (1).

17. The method according to claim 1, wherein The reaction conditions for the isomerized hydrocarbon conversion reaction in step (3) are as follows: the average reaction temperature is 250 to 450 °C; and / or, the hourly space velocity of the liquid is 0.1 to 15.0 h -1 ; and / or, the hydrogen-to-oil volume ratio is 100:1 to 2500:

1.

18. The method according to claim 17, wherein The reaction conditions for the isomerized hydrocarbon conversion reaction in step (3) are as follows: the average reaction temperature is 300 to 400 °C; and / or, the liquid hourly space velocity is 1.0 to 5.0 h -1 ; and / or, the hydrogen-to-oil volume ratio is 400:1 to 2000:1.

Images