A catalytic conversion process for producing light aromatics

Abstract

The application provides a catalytic conversion method and system for producing light aromatic hydrocarbons. Catalytic cracking cycle oil is subjected to two-stage hydrotreating reactions in the presence of hydrogen and a hydrogenation catalyst. The reaction product is separated by a partition wall fractionating column to obtain gas, hydrogenated light naphtha, hydrogenated heavy naphtha, hydrogenated light diesel oil and hydrogenated heavy diesel oil. The hydrogenated heavy diesel oil is returned to the second stage of the hydrogenation device, and the hydrogenated light diesel oil is introduced into a catalytic cracking device to perform a cracking reaction in the presence of a catalytic cracking catalyst. The reaction product is separated to obtain dry gas, liquefied gas, catalytic naphtha rich in light aromatic hydrocarbons, catalytic heavy aromatic hydrocarbon fraction, catalytic cracking cycle oil and oil slurry. The catalytic cracking cycle oil is returned to the first stage of the hydrogenation device for recycling. The method can significantly improve the yield of light aromatic hydrocarbons.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, and more specifically, to a catalytic conversion method for producing light aromatics. Background Technology

[0002] With the development of heavy crude oil refining and the rapid growth in market demand for light and high-quality products, catalytic cracking technology, as a means of refining heavy oil into lighter forms, has developed rapidly in my country. However, the quality of catalytic cracking diesel (or catalytic cracking light cycle oil) has remained poor, characterized by high density, high aromatic content, and low cetane number. Even with diesel hydrotreating technology, it is difficult to meet increasingly stringent diesel specifications. Meanwhile, light aromatics (benzene, toluene, and xylene, collectively known as BTX), represented by para-xylene, are important raw materials for the production of chemical products. Market demand for light aromatics is increasing and currently remains insufficient. Therefore, producing light aromatics through catalytic cracking diesel is a way to meet market demand.

[0003] US4585545 discloses a catalytic conversion method that first hydrotreats the entire fraction of catalytic cracking light cycle oil, and then uses the resulting hydrotreated diesel to produce gasoline rich in monocyclic aromatic hydrocarbons through catalytic cracking.

[0004] CN01807978.4 (CN1422327A) discloses a method for upgrading catalytic cracking light cycle oil, which involves deep hydrogenation of the catalytic light cycle oil produced by the first catalytic cracking unit using heavy oil as feedstock, and then feeding the resulting hydrotreated diesel into the second catalytic cracking unit.

[0005] CN01808113.4 (CN1466619A) discloses a method for converting catalytic cracking light cycle oil, which divides the reaction zone of the catalytic cracking riser into upstream and downstream reaction zones. Heavy oil is injected into the downstream zone, and hydrotreated light cycle oil, a product of catalytic cracking, is injected into the upstream zone after hydrotreating.

[0006] ZL201310010219.5 discloses a method for producing aromatic compounds, wherein the catalytic cracking yields compounds with a distillation range of 250~450. o The C-grade diesel fraction is sent to a hydrotreating unit, where the catalytic cracking heavy cycle oil is hydrotreated and then further catalytically cracked to produce benzene, toluene, and xylene.

[0007] ZL201310517666.X discloses a catalytic conversion method for producing aromatic gasoline, which cuts catalytic cracking light cycle oil into light and heavy fractions. The heavy fraction is hydrotreated and then fed separately into different catalytic cracking units along with the light fraction, thereby maximizing the production of catalytic gasoline rich in benzene, toluene, and xylene.

[0008] As can be seen from the published literature above, one important approach to processing catalytic cracking light cycle oil is to hydrotreat it before catalytic cracking. However, it is worth noting that the choice of fractions before and after hydrotreating is crucial for both hydrogen consumption and the yield of light aromatics from catalytic cracking. Summary of the Invention

[0009] The purpose of this invention is to provide a catalytic conversion method for producing light aromatics based on existing technology.

[0010] To achieve the above objectives, this invention provides a catalytic conversion method for producing light aromatics. The catalytic cracking cycle oil undergoes a two-stage hydrotreating reaction in the presence of hydrogen and a hydrotreating catalyst. The reaction products are separated by a partition distillation tower to obtain gas, hydrotreated light naphtha, hydrotreated heavy naphtha, hydrotreated light diesel oil, and hydrotreated heavy diesel oil. The hydrotreated heavy diesel oil is returned to the second stage of the hydrotreating unit, while the hydrotreated light diesel oil enters the catalytic cracking unit and undergoes a cracking reaction in the presence of a catalytic cracking catalyst. The reaction products are separated to obtain dry gas, liquefied petroleum gas (LPG), catalytic naphtha rich in light aromatics, catalytic heavy aromatics fraction, catalytic cracking cycle oil, and slurry oil. The catalytic cracking cycle oil is returned to the first stage of the hydrotreating unit for recycling.

[0011] A first aspect of the present invention provides a catalytic conversion method for producing light aromatics, the method comprising:

[0012] (1) Catalytic cracking cycle oil enters the hydrotreating unit and undergoes a two-stage hydrotreating reaction with hydrogen in the presence of a hydrotreating catalyst to obtain hydrotreated oil gas;

[0013] (2) Hydrogenated oil and gas enter the partition distillation tower for separation to obtain gas, hydrogenated light naphtha, hydrogenated heavy naphtha, hydrogenated light diesel oil and hydrogenated heavy diesel oil;

[0014] (3) The hydrogenated heavy diesel oil obtained in step (2) is returned to the second stage of the hydrogenation unit for recycling, and the hydrogenated light diesel oil obtained in step (2) enters the catalytic cracking unit, where catalytic cracking reaction is carried out in the presence of catalytic cracking catalyst, and the catalytic cracking reaction products are separated to obtain dry gas, liquefied gas, catalytic naphtha rich in light aromatics, catalytic heavy aromatics fraction, catalytic cracking cycle oil and oil slurry.

[0015] (4) The catalytic cracking cycle oil obtained in step (3) is returned to the first stage of the hydrotreating unit for recycling; optionally, the catalytic heavy aromatic fraction obtained in step (3) is returned to the catalytic cracking unit for recycling.

[0016] According to the catalytic conversion method of the first aspect, in step (1), the hydrogenation reaction conditions are as follows:

[0017] Preferably, the reaction conditions for the first stage of hydrogenation are: hydrogen partial pressure 5.0~20.0 MPa and reaction temperature 300~450 °C.o C. Volumetric hourly space velocity (VHSV) 0.5~5.0 h⁻¹ -1 Hydrogen-to-oil volume ratio 300~1600 Nm 3 / m 3 ; and / or

[0018] Preferably, the reaction conditions for the second stage hydrogenation treatment are a hydrogen partial pressure of 5.0~20.0 MPa and a reaction temperature of 350~500 °C. o C. Volumetric hourly space velocity (VHSV) 0.1~3.0 h⁻¹ -1 Hydrogen-to-oil volume ratio 400~2000 Nm 3 / m 3 .

[0019] According to the catalytic conversion method of the first aspect, in step (1), the hydrogenation catalysts are the same or different in the two-stage hydrogenation treatment reaction;

[0020] Preferably, the hydrogenation catalyst comprises an active metal component and a support, wherein the active metal component is selected from one or more of Group VIB metals and / or Group VIII non-noble metals, and the support is selected from one or more of alumina, silica, and amorphous silica-alumina.

[0021] More preferably, the active metal component is selected from any one of the following metal combinations: nickel-tungsten, nickel-tungsten-cobalt, nickel-molybdenum, and cobalt-molybdenum.

[0022] According to the catalytic conversion method of the first aspect, in step (2), at least one partition wall is provided in the partition distillation column, which divides the partition distillation column into four areas: a pre-separation zone, a common distillation section, a common stripping section, and a side-stream distillation zone. The hydrogenated oil and gas feed position is located in the pre-separation zone.

[0023] According to the catalytic conversion method of the first aspect, the pressure at the top of the partitioned distillation column is 0.1~1.0 MPa, preferably 0.2~0.7 MPa;

[0024] The temperature at the top of the tower is 50~120°C. o C, preferably 60~100 o C;

[0025] The ratio of the liquid phase mass flow rate entering the pre-separation zone from the common rectification section to that entering the side-stream rectification zone is 0.1~10, preferably 0.5~5;

[0026] The ratio of the vapor mass flow rate from the common stripping section to the pre-separation zone to the side-stream rectification zone is 1~15, preferably 2~10; and / or

[0027] The ratio of the total mass flow rate of the gas phase to the mass flow rate of the produced gas phase at the pre-separation zone extraction location is 10~150, preferably 30~120.

[0028] According to the catalytic conversion method of the first aspect, the number of trays in the pre-separation zone of the partitioned distillation column is 10 to 40, preferably 20 to 35;

[0029] The common rectifying section has 2 to 10 trays, preferably 3 to 8; the common stripping section has 2 to 10 trays, preferably 3 to 8; and / or

[0030] The number of trays in the sidestream distillation zone is 10 to 45, preferably 25 to 40.

[0031] According to the catalytic conversion method of the first aspect, wherein the side-stream distillation zone is located at trays 20-45, preferably trays 30-40, and preferably, the side-stream distillation zone is further provided with a mid-section circulating heat extraction; and / or

[0032] Preferably, the pre-separation zone is equipped with a gas phase extraction point, located on the 20th to 40th trays of the pre-separation zone, more preferably on the 25th to 35th trays, and the return point is located on the 30th to 45th trays of the side-stream distillation zone, more preferably on the 30th to 40th trays.

[0033] According to the catalytic conversion method of the first aspect, in step (2), the hydrotreated light naphtha is separated from the common rectification section of the partition distillation column, with an initial boiling point of 20-40. o C, final boiling point is 55~65 o C;

[0034] The hydrotreated heavy naphtha is extracted from plates 5 to 30 of the side-stream rectification zone of the distillation column, preferably plates 10 to 20, with an initial boiling point of 55-65°C. o C, final boiling point is 140~170 o C;

[0035] The hydrotreated light diesel oil is extracted from any location below the hydrotreated heavy naphtha extraction point in the side-stream rectification zone, preferably from plate 25 to 35, with an initial boiling point of 140 to 170°C. o C, final boiling point is 230~280 o C; and / or

[0036] The hydrotreated heavy diesel oil is separated from the lower part of the common stripping section of the distillation column, with an initial boiling point of 230~280°C. o C.

[0037] According to the catalytic conversion method of the first aspect, in step (3), the initial boiling point of the catalytic naphtha is 20~40. o C, final boiling point is 140~160 o C;

[0038] The initial boiling point of the catalytic heavy aromatic fraction is 140~160°C. o C, final boiling point is 210~250 o C; and / or

[0039] The initial boiling point of the catalytic cracking cycle oil is 210~250°C. o C, final boiling point is 320~360 o C.

[0040] According to the catalytic conversion method of the first aspect, in step (3), the conditions for the catalytic cracking reaction include:

[0041] The heavy hourly space velocity of oil and gas is 4~20h. -1 Preferably 8~16h -1 ;

[0042] The catalytic cracking reaction temperature is 520~650℃ o C, preferably 560~640 o C; and / or

[0043] The weight ratio of the agent to oil is 6 to 26, preferably 8 to 20.

[0044] According to the catalytic conversion method of the first aspect, in step (3), the catalytic cracking catalyst contains 10-60 parts by weight of molecular sieve, 1-40 parts by weight of binder and 1-90 parts by weight of support;

[0045] The molecular sieve is selected from one or more of ZSM molecular sieve, Y molecular sieve, HY molecular sieve, USY molecular sieve and Beta molecular sieve. Optionally, the molecular sieve contains rare earth elements, which are one or more of La, Ce, Pr and Nd.

[0046] The adhesive is selected from silica adhesives and / or alumina adhesives;

[0047] The carrier is selected from one or more of the following: silica, kaolin, montmorillonite, diatomite, halloysite, soapstone, rettosite, sepiolite, attapulgite, hydrotalcite, and bentonite.

[0048] A second aspect of the present invention provides a catalytic conversion system for producing light aromatics, comprising:

[0049] The hydrogenation unit is a two-stage hydrogenation unit, which is provided with a hydrogen inlet and a hydrogenated oil / gas outlet. The first stage of the hydrogenation unit is provided with a catalytic cracking cycle oil inlet, and the second stage of the hydrogenation unit is provided with a hydrogenated heavy diesel oil inlet.

[0050] A partition distillation column is provided, wherein at least one partition wall is provided within the partition distillation column, dividing the column into four regions: a common stripping section at the bottom of the column, a common rectification section at the top of the column, a pre-separation zone in the middle section of the column, and a side-stream rectification zone. The pre-separation zone is provided with a hydrotreated oil / gas inlet, which is connected to the hydrotreated oil / gas outlet of the hydrotreating unit. The common rectification section is provided with a low-boiling-point fraction outlet. The side-stream rectification zone is provided with a hydrotreated heavy naphtha rich in light aromatics outlet and a hydrotreated light diesel oil outlet. The bottom of the common stripping section is provided with a hydrotreated heavy diesel oil outlet, which is connected to the hydrotreated heavy diesel oil inlet on the second section of the hydrotreating unit.

[0051] A catalytic cracking unit is provided with a hydrotreated light diesel oil inlet, a dry gas outlet, a liquefied petroleum gas outlet, a catalytic naphtha rich in light aromatics outlet, a catalytic heavy aromatics outlet, a catalytic cracking cycle oil outlet, and a slurry oil outlet. The catalytic heavy aromatics outlet is connected to a catalytic heavy aromatics fractionation pipeline, and the catalytic cracking cycle oil outlet is connected to a catalytic cracking cycle oil inlet on the first section of the hydrotreated unit. Optionally, the catalytic heavy aromatics fractionation pipeline is connected to the hydrotreated light diesel oil inlet.

[0052] According to the catalytic conversion system of the second aspect, the catalytic cracking unit is a single reactor or a dual reactor;

[0053] Preferably, the reactor is selected from one or more of the following: constant diameter riser, constant linear velocity riser, variable diameter riser, variable linear velocity riser, fluidized bed, and composite reactor, wherein the composite reactor is composed of a constant diameter or variable diameter riser and a fluidized bed.

[0054] Through the above technical solution, the present invention utilizes a partitioned separation tower to efficiently separate hydrogenated light diesel oil, which produces a large amount of light aromatics, from the hydrogenated catalytic cracking cycle oil and uses it as feedstock for catalytic cracking, thereby improving the yield of light aromatics.

[0055] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0056] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0057] Figure 1 This is a schematic diagram of the system structure in a preferred embodiment of the present invention.

[0058] Figure 2 This is a schematic diagram of the comparative system structure of the present invention.

[0059] Explanation of reference numerals in the attached figures

[0060] 100. Hydrogenation unit; 200. Divider-wall distillation column; 300. Catalytic cracking unit; 400. Light naphtha separator; 500. Heavy naphtha separator;

[0061] 101. Hydrogen inlet; 102. Catalytic cracking cycle oil inlet; 103. Hydrogenation oil and gas pipeline; 104. First stage of the hydrotreating unit; 105. Second stage of the hydrotreating unit;

[0062] 201. Pre-separation zone; 202. Common rectification section; 203. Common stripping section; 204. Side-stream rectification zone; 205. Separator wall; 206. Hydrogenated light diesel pipeline; 207. Hydrogenated heavy diesel pipeline;

[0063] 301. Catalytic cracking heavy aromatics fraction pipeline; 302. Catalytic cracking circulating oil pipeline;

[0064] 501. Hydrogenated diesel pipeline;

[0065] A01, A01′. Gas; A02, A02′. Hydrogenated light naphtha; B, B′. Hydrogenated heavy naphtha; C, C′. Dry gas; D, D′. Liquefied petroleum gas; E, E′. Catalytic naphtha; F, F′. Catalytic slurry oil; G. Catalytic heavy aromatics. Detailed Implementation

[0066] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0067] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0068] Any specific numerical value disclosed in this application (including the endpoints of the numerical range) is not limited to the exact value, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical range, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0069] In this application, the terms "upstream" and "downstream" refer to the direction of reaction material flow. For example, when the reaction material flows from bottom to top, "upstream" refers to the position located at the bottom, while "downstream" refers to the position located at the top.

[0070] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0071] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0072] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0073] Before describing the technical solution of this invention, the terms used herein are defined as follows:

[0074] The term "initial boiling point" refers to the temperature at which the boiling range begins.

[0075] The term "final boiling point" refers to the temperature at the end of the distillation process.

[0076] The light aromatic hydrocarbons mentioned in this invention refer to C6-C8 aromatic hydrocarbons.

[0077] This invention provides a catalytic conversion method for producing light aromatics, the method comprising:

[0078] (1) Catalytic cracking cycle oil enters the hydrotreating unit and undergoes a two-stage hydrotreating reaction with hydrogen in the presence of a hydrotreating catalyst to obtain hydrotreated oil gas;

[0079] (2) Hydrogenated oil and gas enter the partition distillation tower for separation to obtain gas, hydrogenated light naphtha, hydrogenated heavy naphtha, hydrogenated light diesel oil and hydrogenated heavy diesel oil;

[0080] (3) The hydrogenated heavy diesel oil obtained in step (2) is returned to the second stage of the hydrogenation unit for recycling, and the hydrogenated light diesel oil obtained in step (2) enters the catalytic cracking unit, where catalytic cracking reaction is carried out in the presence of catalytic cracking catalyst, and the catalytic cracking reaction products are separated to obtain dry gas, liquefied gas, catalytic naphtha rich in light aromatics, catalytic heavy aromatics fraction, catalytic cracking cycle oil and oil slurry.

[0081] (4) The catalytic cracking cycle oil obtained in step (3) is returned to the first stage of the hydrotreating unit for recycling; optionally, the catalytic heavy aromatic fraction obtained in step (3) is returned to the catalytic cracking unit for recycling.

[0082] The inventors of this invention have discovered that light diesel oil after hydrotreating catalytic cracking cycle oil is more suitable as a feedstock for catalytic cracking to produce light aromatics than full-fraction diesel oil, significantly improving the yield of light aromatics.

[0083] Optionally, returning the heavy aromatics fraction from catalytic cracking to the catalytic cracking unit for zone conversion can further improve the yield of light aromatics.

[0084] In one embodiment, the hydrogenation reaction conditions in step (1) are as follows:

[0085] Preferably, the reaction conditions for the first stage of hydrogenation are: hydrogen partial pressure 5.0~20.0 MPa and reaction temperature 300~450 °C. o C. Volumetric hourly space velocity (VHSV) 0.5~5.0 h⁻¹ -1 Hydrogen-to-oil volume ratio 300~1600 Nm 3 / m 3 ; and / or

[0086] Preferably, the reaction conditions for the second stage hydrogenation treatment are a hydrogen partial pressure of 5.0~20.0 MPa and a reaction temperature of 350~500 °C. o C. Volumetric hourly space velocity (VHSV) 0.1~3.0 h⁻¹ -1 Hydrogen-to-oil volume ratio 400~2000 Nm 3 / m 3 .

[0087] In one embodiment, in step (1), the hydrogenation catalysts are the same or different in the two hydrogenation treatment reactions;

[0088] Preferably, the hydrogenation catalyst comprises an active metal component and a support, wherein the active metal component is selected from one or more of Group VIB metals and / or Group VIII non-noble metals, and the support is selected from one or more of alumina, silica, and amorphous silica-alumina.

[0089] More preferably, the active metal component is selected from any one of the following metal combinations: nickel-tungsten, nickel-tungsten-cobalt, nickel-molybdenum, and cobalt-molybdenum.

[0090] In one embodiment, in step (2), at least one partition wall is provided in the partition distillation column, which divides the partition distillation column into four areas: a pre-separation zone, a common distillation section, a common stripping section, and a side-stream distillation zone. The hydrogenated oil and gas feed position is located in the pre-separation zone.

[0091] In one embodiment, the pressure at the top of the partitioned distillation column is 0.1~1.0 MPa, preferably 0.2~0.7 MPa;

[0092] The temperature at the top of the tower is 50~120°C. oC, preferably 60~100 o C;

[0093] The ratio of the liquid phase mass flow rate entering the pre-separation zone from the common rectification section to that entering the side-stream rectification zone is 0.1~10, preferably 0.5~5;

[0094] The ratio of the vapor mass flow rate from the common stripping section to the pre-separation zone to the side-stream rectification zone is 1~15, preferably 2~10; and / or

[0095] The ratio of the total mass flow rate of the gas phase to the mass flow rate of the produced gas phase at the pre-separation zone extraction location is 10~150, preferably 30~120.

[0096] In one embodiment, the number of trays in the pre-separation zone of the partition distillation column is 10 to 40, preferably 20 to 35;

[0097] The common rectifying section has 2 to 10 trays, preferably 3 to 8; the common stripping section has 2 to 10 trays, preferably 3 to 8; and / or

[0098] The number of trays in the sidestream distillation zone is 10 to 45, preferably 25 to 40.

[0099] In one embodiment, the side-stream rectification zone is located at trays 20-45, preferably trays 30-40, and preferably, the side-stream rectification zone also includes a mid-section circulating heat extraction system; and / or

[0100] Preferably, the pre-separation zone is equipped with a gas phase extraction point, located on the 20th to 40th trays of the pre-separation zone, more preferably on the 25th to 35th trays, and the return point is located on the 30th to 45th trays of the side-stream distillation zone, more preferably on the 30th to 40th trays.

[0101] In one embodiment, in step (2), the light naphtha is separated from the common rectification section of the partition distillation column, with an initial boiling point of 20-40. o C, final boiling point is 55~65 o C;

[0102] The heavy naphtha is extracted from plates 5 to 30 of the side-stream rectification zone of the distillation column, preferably plates 10 to 20, with an initial boiling point of 55 to 65°C. o C, final boiling point is 140~170 o C;

[0103] The hydrotreated light diesel oil is extracted from any location below the hydrotreated heavy naphtha extraction point in the side-stream rectification zone, preferably from plate 25 to 35, with an initial boiling point of 140 to 170°C. o C, final boiling point is 230~280 o C; and / or

[0104] The hydrotreated heavy diesel oil is separated from the lower part of the common stripping section of the distillation column, with an initial boiling point of 230~280°C. o C.

[0105] In one embodiment, in step (3), the initial boiling point of the catalytic naphtha is 20-40 °C. o C, final boiling point is 140~160 o C;

[0106] The initial boiling point of the catalytic heavy aromatic fraction is 140~160°C. o C, final boiling point is 210~250 o C; and / or

[0107] The initial boiling point of the catalytic cracking cycle oil is 210~250°C. o C, final boiling point is 320~360 o C.

[0108] In one embodiment, in step (3), the conditions for the catalytic cracking reaction include:

[0109] The heavy hourly space velocity of oil and gas is 4~20h. -1 Preferably 8~16h -1 ;

[0110] The catalytic cracking reaction temperature is 520~650℃ o C, preferably 560~640 o C; and / or

[0111] The weight ratio of the agent to oil is 6 to 26, preferably 8 to 20.

[0112] This invention employs a partitioned distillation column to separate hydrogenated light diesel and hydrogenated heavy diesel. The recycling of hydrogenated heavy diesel can further improve the yield of light aromatics from diesel hydrogenation. Hydrogenated light diesel is the highest quality feedstock for the production of light aromatics by catalytic cracking, and its distillation range is similar to that of the heavy aromatic fraction in the catalytic product. Hydrogenated light diesel, together with the recycled catalytic heavy aromatics, is used as feedstock for catalytic cracking, thereby improving the utilization efficiency of aromatics. This method maximizes the production of light aromatics through hydrogenation and catalytic cracking.

[0113] In one embodiment, in step (3), the catalytic cracking catalyst contains 10-60 parts by weight of molecular sieve, 1-40 parts by weight of binder and 1-90 parts by weight of support.

[0114] The molecular sieve is selected from one or more of ZSM molecular sieve, Y molecular sieve, HY molecular sieve, USY molecular sieve and Beta molecular sieve. Optionally, the molecular sieve contains rare earth elements, which are one or more of La, Ce, Pr and Nd.

[0115] The adhesive is selected from silica adhesives and / or alumina adhesives;

[0116] The carrier is selected from one or more of the following: silica, kaolin, montmorillonite, diatomite, halloysite, soapstone, rettosite, sepiolite, attapulgite, hydrotalcite, and bentonite.

[0117] The present invention also provides a catalytic conversion system for producing light aromatics, comprising:

[0118] The hydrogenation unit is a two-stage hydrogenation unit, which is provided with a hydrogen inlet and a hydrogenated oil / gas outlet. The first stage of the hydrogenation unit is provided with a catalytic cracking cycle oil inlet, and the second stage of the hydrogenation unit is provided with a hydrogenated heavy diesel oil inlet.

[0119] A partition distillation column is provided, wherein at least one partition wall is provided within the partition distillation column, dividing the column into four regions: a common stripping section at the bottom of the column, a common rectification section at the top of the column, a pre-separation zone in the middle section of the column, and a side-stream rectification zone. The pre-separation zone is provided with a hydrotreated oil / gas inlet, which is connected to the hydrotreated oil / gas outlet of the hydrotreating unit. The common rectification section is provided with a low-boiling-point fraction outlet. The side-stream rectification zone is provided with a hydrotreated heavy naphtha rich in light aromatics outlet and a hydrotreated light diesel oil outlet. The bottom of the common stripping section is provided with a hydrotreated heavy diesel oil outlet, which is connected to the hydrotreated heavy diesel oil inlet on the second section of the hydrotreating unit.

[0120] A catalytic cracking unit is provided with a hydrotreated light diesel oil inlet, a dry gas outlet, a liquefied petroleum gas outlet, a catalytic naphtha rich in light aromatics outlet, a catalytic heavy aromatics outlet, a catalytic cracking cycle oil outlet, and a slurry oil outlet. The catalytic heavy aromatics outlet is connected to a catalytic heavy aromatics fractionation pipeline, and the catalytic cracking cycle oil outlet is connected to a catalytic cracking cycle oil inlet on the first section of the hydrotreated unit. Optionally, the catalytic heavy aromatics fractionation pipeline is connected to the hydrotreated light diesel oil inlet.

[0121] In one embodiment, the catalytic cracking unit is a single reactor or a dual reactor;

[0122] Preferably, the reactor is selected from one or more of the following: constant diameter riser, constant linear velocity riser, variable diameter riser, variable linear velocity riser, fluidized bed, and composite reactor, wherein the composite reactor is composed of a constant diameter or variable diameter riser and a fluidized bed.

[0123] refer to Figure 1 In a preferred embodiment of the present invention, the distillation range is 220~350. oThe catalytic cracking cycle oil of C enters the first stage 104 of the hydrotreating unit through the catalytic cracking cycle oil inlet 102. It then contacts the hydrogen and hydrotreating catalyst entering through the hydrogen inlet 101 for a two-stage hydrotreating reaction. After the reaction oil and gas undergoes hot and cold high-low separation to separate the cycle hydrogen and low-grade gas, the liquid phase enters the pre-separation zone 201 of the adjacent distillation column 200 through the hydrotreating oil and gas pipeline 103. The pre-separated oil and gas then enters the side-stream distillation zone 204 through the pre-separation zone oil and gas pipeline 208. The common distillation section 202 at the top of the column separates gases smaller than 60... o C fraction, further separated into gas A01 and hydrotreated light naphtha A02, and the common stripping section 203 at the bottom of the column separates out products with a content greater than 240. o The hydrotreated heavy diesel oil from C returns to the second stage 105 of the hydrotreating unit via hydrotreated heavy diesel oil pipeline 207. The upper part of the side stream distillation zone 204 has a separation range of 60~160. o Hydrogenated heavy naphtha B from C has a lower fraction with a distillation range of 160~240. o Hydrogenated light diesel oil (C) enters the catalytic cracking unit 300 via hydrogenated light diesel oil pipeline 206 as feedstock in the first reaction zone, reacting with the catalytic cracking catalyst to obtain reaction products: dry gas (C), liquefied petroleum gas (D), catalytic naphtha (E) rich in benzene, toluene, and xylene, and slurry oil (F) with a distillation range of 150-240. o The C-catalyst heavy aromatics fraction is returned to the catalytic cracking unit 300 for zoned recycling via catalytic heavy aromatics fraction pipeline 301, with a distillation range of 240~350. o The catalytic cracking cycle oil from unit C is returned to the first stage 104 of the hydrotreating unit via catalytic cracking cycle oil pipeline 302 for reuse. The catalytic cracking unit uses a single riser reactor.

[0124] The present invention will be further described in detail below through embodiments. Unless otherwise specified, the raw materials used in the embodiments are all commercially available.

[0125] The hydrogenation catalysts used in the examples and comparative examples were purchased from brands FZC and FC-70, and the catalytic cracking catalyst was purchased from brand SLA-1.

[0126] The properties of the catalytic cracking cycle oils used in the examples and comparative examples are shown in Table 1.

[0127] Table 1

[0128]

[0129] Example 1

[0130] refer to Figure 1The hydrogenation unit 100 employs a fixed-bed reactor and includes separate hot and cold sections, comprising a first section 104 and a second section 105. The upper and lower sections respectively house FZC and FC-70 hydrogenation catalysts. Hydrogen enters the first section 104 through hydrogen inlet 101, and catalytic cracking cycle oil enters the first section 104 through catalytic cracking cycle oil inlet 102. A partition wall 205 is installed inside the distillation column 200 to radially separate the column. The number of trays in the pre-separation zone 201, common rectification section 202, common stripping section 203, and side-stream rectification zone 204 are 34, 6, 4, and 36, respectively. The top reflux ratio is 6. Hydrogenated heavy naphtha B is collected from the 15th tray from the top of the side-stream rectification zone 204, and hydrogenated light diesel oil is collected from the 32nd tray from the top of the side-stream rectification zone 204. The pressure at the top of the adjacent distillation column 200 is 0.4 MPa, and the temperature at the top is 67°C. o C. The side-stream rectification zone has a mid-section circulating heat recovery section. The side-stream output and return points are located at plates 31 and 30 of the side-stream rectification zone. The pre-separation zone of the diverter column has a vapor output point located at plate 25 of the pre-separation zone, and the return point is located at plate 30 of the side-stream rectification zone. The liquid phase mass flow rate ratio entering the pre-separation zone from the common rectification section to the side-stream rectification zone is 2.64; the vapor phase mass flow rate ratio entering the pre-separation zone from the common stripping section to the side-stream rectification zone is 4.22; the ratio of the total vapor phase mass flow rate to the output vapor phase mass flow rate at the output point of the pre-separation zone is 69.36. The catalytic cracking unit 300 uses a single riser reactor.

[0131] Distillation range: 220~350 o The catalytic cracking cycle oil and hydrogen in C are sequentially passed through the upper and lower sections of the hydrotreating unit and reacted with two different hydrotreating catalysts. The hydrogen partial pressure is 8.0 MPa, and the reaction temperatures in the upper and lower sections are 360°C and 360°C respectively. o C and 380 o C, with a volumetric hourly space velocity of 2.0 h⁻¹. -1 and 1.0h -1 The hydrogen-to-oil volume ratios are 800 and 1300, respectively. The reaction oil and gas enter the adjacent distillation column 200 through the hydrogenated oil and gas pipeline 103 for separation, separating three fractions with boiling points from low to high. The fraction drawn from the top of the column is less than 60... o The C light fraction can be further separated into A01 gas and A02 hydrotreated light naphtha (25~60). o C), the common stripping section at the bottom of the column 203 separates out a product greater than 240 o C-hydrotreated heavy diesel oil returns to the second section 105 of the hydrotreating unit via hydrotreated heavy diesel oil pipeline 207. 57-150 ml is extracted from the upper part of the side-stream rectification zone 204 (the 15th plate from top to bottom). o Hydrogenated heavy naphtha B from C, extracted from the bottom (32nd plate from the top), yields 150-240. oC's hydrotreated light diesel oil enters the catalytic cracking unit 300 via hydrotreated light diesel oil pipeline 206, where it reacts at a temperature of 580°C, a catalyst-to-oil mass ratio of 10, and a heavy hourly space velocity of 10 h⁻¹. -1 Under certain conditions, the mixture reacts with a catalyst. After the reaction, the oil and gas are separated to obtain dry gas C and liquefied petroleum gas D, with a distillation range of 25~150. o C is a catalytic naphtha E rich in benzene, toluene, and xylene, with a distillation range of 150-240. o C-catalyzed heavy aromatics, with a distillation range of 240~350. o C's catalytic cracking cycle oil and slurry oil F have a distillation range of 150~240. o The heavy aromatics fraction from the C-catalyst is returned to the catalytic cracking unit 300 for recycling via heavy aromatics fraction pipeline 301, with a distillation range of 240~350. o The catalytic cracking cycle oil of C is returned to the hydrotreating unit via catalytic cracking cycle oil pipeline 302. The product distribution is shown in Table 2.

[0132] Example 2

[0133] The hydrogenation unit 100 employs a fixed-bed reactor, comprising a first section 104 and a second section 105. The upper and lower sections respectively house RN-411 and RHC-100 hydrogenation catalysts. Hydrogen enters the first section 104 through hydrogen inlet 101, and catalytic cracking cycle oil enters the first section 104 through catalytic cracking cycle oil inlet 102. A partition wall 205 is installed inside the distillation column 200 to radially separate the column. The pre-separation zone 201, common rectification section 202, common stripping section 203, and side-stream rectification zone 204 have 34, 6, 4, and 36 trays respectively, with a top reflux ratio of 6. Hydrogenated heavy naphtha B is collected from the 15th tray from the top of the side-stream rectification zone 204, and hydrogenated light diesel oil is collected from the 32nd tray from the top of the side-stream rectification zone 204. The pressure at the top of the adjacent distillation column 200 is 0.4 MPa, and the temperature at the top is 67°C. o C. The side-stream distillation zone features mid-section circulating heat extraction, with the side-stream exit and return points located at plates 31 and 30 of the side-stream distillation zone. The pre-separation zone of the diverter column features a vapor exit point located at plate 25 of the pre-separation zone, and the return point is located at plate 30 of the side-stream distillation zone. The liquid phase mass flow rate ratio entering the pre-separation zone from the common distillation section to the side-stream distillation zone is 2.64; the vapor phase mass flow rate ratio entering the pre-separation zone from the common stripping section to the side-stream distillation zone is 4.22; the ratio of the total vapor phase mass flow rate to the exit vapor phase mass flow rate at the exit point in the pre-separation zone is 69.36. The catalytic cracking unit 300 employs a single riser reactor, with the catalyst passing through the second reaction zone and the first reaction zone sequentially from bottom to top.

[0134] Distillation range: 220~350 oThe catalytic cracking cycle oil and hydrogen in C are sequentially passed through two stages of the hydrotreating unit 100, reacting with two different hydrotreating catalysts. The hydrogen partial pressure is 8.0 MPa, and the reaction temperatures in the two stages are 360°C and 360°C respectively. o C and 380 o C, with a volumetric hourly space velocity of 2.0 h⁻¹. -1 and 1.0h -1 The hydrogen-to-oil volume ratios are 800 and 1300, respectively. The reaction oil and gas enter the adjacent distillation column 200 through the hydrogenated oil and gas pipeline 103 for separation, separating three fractions with boiling points from low to high. The fraction drawn from the top of the column is less than 60... o The C light fraction can be further separated into A01 gas and A02 hydrotreated light naphtha (25~60). o C), the common stripping section at the bottom of the column 203 separates out a product greater than 240 o C-hydrotreated heavy diesel oil is returned to the second stage 105 of the hydrotreating unit, and 57-150 ml is extracted from the upper part of the side-stream rectification zone 204 (the 15th plate from top to bottom). o Hydrogenated heavy naphtha B from C, extracted from the bottom (32nd plate from the top), yields 150-240. o C's hydrotreated light diesel oil enters the catalytic cracking unit 300 via hydrotreated light diesel oil pipeline 206, where it reacts at a reaction temperature of 580°C, a catalyst-to-oil mass ratio of 10, and a heavy hourly space velocity of 10 h⁻¹. -1 The mixture reacts with a catalyst under specific conditions. After the reaction, the oil and gas are separated to obtain dry gas (C), liquefied petroleum gas (D), and catalytic naphtha (E) with a distillation range of 150-240°C (25-150°C). o C-catalyzed heavy aromatics, distillation range 240~350 o C's catalytic cracking cycle oil and slurry oil F have a distillation range of 240~350. o The catalytic cracking cycle oil of C is returned to the hydrotreating unit 100 via catalytic cracking cycle oil pipeline 302, while the catalytic heavy aromatics fraction is not returned to the catalytic cracking unit. The product distribution is shown in Table 2.

[0135] Comparative Example

[0136] like Figure 2 As shown, this comparative example differs from the embodiment in that, after the catalytic cracking cycle oil is hydrogenated in the hydrotreating unit 100, the reaction oil gas undergoes hot and cold high-low separation to separate the cycle hydrogen and low-grade gas. The liquid phase then enters the light naphtha separator 400, which has 30 trays and a reflux ratio of 0.8. Gas A01 and hydrotreated light naphtha A02 fractions are separated at the top of the separator, while hydrotreated heavy naphtha and hydrotreated diesel fractions are separated at the bottom and sent to the heavy naphtha separator 500, which has 40 trays and a reflux ratio of 1.8. The hydrotreated heavy naphtha fraction B is collected from the top of the separator, and the hydrotreated diesel fraction from the bottom enters the catalytic cracking unit 300 via the hydrotreated diesel pipeline 501. The operating conditions of the catalytic cracking unit 300 are the same as in embodiment 2. The product distribution is shown in Table 2.

[0137] Table 2

[0138]

[0139] As can be seen from Table 2, the total C6-C8 light aromatics yields of Examples 1 and 2 were 11.68 and 3.96 percentage points higher than those of the comparative examples, respectively.

[0140] Based on Aspen, the accuracy and energy consumption of the separation process in the embodiment and the comparative example are calculated and compared in Table 3.

[0141] Table 3

[0142]

[0143] Compared with the comparative example, the embodiment has comparable separation accuracy for heavy naphtha under the condition of producing an additional stream of hydrotreated light diesel oil, while the total energy consumption remains basically unchanged, and the equipment investment of a separation tower is saved.

[0144] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A catalytic conversion method for producing light aromatics, characterized in that, The method includes: (1) Catalytic cracking cycle oil enters the hydrotreating unit and undergoes a two-stage hydrotreating reaction with hydrogen in the presence of a hydrotreating catalyst to obtain hydrotreated oil gas; (2) Hydrogenated oil and gas enter the distillation column of the partition wall and are separated to obtain gas, hydrogenated light naphtha, hydrogenated heavy naphtha, hydrogenated light diesel oil and hydrogenated heavy diesel oil; (3) The hydrogenated heavy diesel oil obtained in step (2) is returned to the second stage of the hydrogenation unit for recycling, and the hydrogenated light diesel oil obtained in step (2) enters the catalytic cracking unit, where catalytic cracking reaction is carried out in the presence of catalytic cracking catalyst, and the catalytic cracking reaction products are separated to obtain dry gas, liquefied gas, catalytic naphtha rich in light aromatics, catalytic heavy aromatics fraction, catalytic cracking cycle oil and oil slurry. (4) The catalytic cracking cycle oil obtained in step (3) is returned to the first stage of the hydrotreating unit for recycling; The partitioned distillation column is equipped with at least one partition wall, which divides the column into four regions: a pre-separation zone, a common rectification section, a common stripping section, and a side-stream rectification zone. The hydrogenated oil / gas feed is located in the pre-separation zone. The pre-separation zone of the partition distillation column has 10 to 40 trays. The number of trays in the common rectification section is 2 to 10. The common stripping section has 2 to 10 trays; and / or The number of trays in the side-stream distillation zone is 10 to 45.

2. The catalytic conversion method according to claim 1, characterized in that, The catalytic heavy aromatic fraction obtained in step (3) is returned to the catalytic cracking unit for recycling.

3. The catalytic conversion method according to claim 1, characterized in that, In step (1), the conditions for the two-stage hydrogenation reaction are as follows: The conditions for the first stage of hydrogenation are: hydrogen partial pressure 5.0~20.0 MPa, reaction temperature 300~450 °C. o C. Volumetric hourly space velocity (VHSV) 0.5~5.0 h⁻¹ -1 Hydrogen-to-oil volume ratio 300~1600 Nm 3 / m 3 ; and / or The reaction conditions for the second-stage hydrogenation process are: hydrogen partial pressure 5.0~20.0 MPa, reaction temperature 350~500 °C. o C. Volumetric hourly space velocity (VHSV) 0.1~3.0 h⁻¹ -1 Hydrogen-to-oil volume ratio 400~2000 Nm 3 / m 3 .

4. The catalytic conversion method according to claim 1, characterized in that, In step (1), the hydrogenation catalysts are the same or different in the two hydrogenation treatment reactions.

5. The catalytic conversion method according to claim 4, characterized in that, The hydrogenation catalyst comprises an active metal component and a support, wherein the active metal component is selected from one or more Group VIB metals and / or Group VIII non-noble metals, and the support is selected from one or more alumina, silica, and amorphous silica-alumina.

6. The catalytic conversion method according to claim 5, characterized in that, The active metal component is selected from any of the following metal combinations: nickel-tungsten, nickel-tungsten-cobalt, nickel-molybdenum, and cobalt-molybdenum.

7. The method according to claim 1, characterized in that, In the distillation column with partition wall, the pressure at the top of the column is 0.1~1.0 MPa; The temperature at the top of the tower is 50~120°C. o C; The ratio of liquid phase mass flow rate entering the pre-separation zone from the common rectification section to that entering the side-stream rectification zone is 0.1~10; The ratio of the vapor mass flow rate from the common stripping section to the pre-separation zone to the side-stream rectification zone is 1–15; and / or The ratio of the total mass flow rate of the gas phase to the mass flow rate of the produced gas phase at the pre-separation zone extraction location is 10~150.

8. The method according to claim 7, characterized in that, In the distillation column with partition wall, the pressure at the top of the column is 0.2~0.7MPa; The temperature at the top of the tower is 60~100 o C; The ratio of liquid phase mass flow rate entering the pre-separation zone from the common rectification section to that entering the side-stream rectification zone is 0.5~5; The ratio of the vapor mass flow rate from the common stripping section to the pre-separation zone to the side-stream rectification zone is 2–10; and / or The ratio of the total mass flow rate of the gas phase to the mass flow rate of the produced gas phase at the pre-separation zone extraction location is 30~120.

9. The catalytic conversion method according to claim 1, characterized in that, The pre-separation zone in the partition distillation column has 20 to 35 trays. The number of trays in the common rectification section is 3 to 8; The common stripping section has 3 to 8 trays; and / or The side-stream distillation zone has 25 to 40 trays.

10. The catalytic conversion method according to claim 1, characterized in that, The feed and return points of the side-stream rectification zone are located on trays 20 to 45 of the side-stream rectification zone; and / or The pre-separation zone is equipped with a gas phase extraction point, located on trays 20 to 40 of the pre-separation zone, and the return point is located on trays 30 to 45 of the side-stream distillation zone.

11. The catalytic conversion method according to claim 10, characterized in that, The extraction and return points of the side-stream rectification zone are located at plates 30-40 of the side-stream rectification zone. The side-stream rectification zone is also equipped with a mid-section circulating heat extraction system; and / or The pre-separation zone is equipped with a gas phase extraction point, located on plates 25-35 of the pre-separation zone, and the return point is located on plates 30-40 of the side-stream distillation zone.

12. The catalytic conversion method according to any one of claims 1 to 11, characterized in that, In step (2), the hydrotreated light naphtha is separated from the common rectification section of the distillation column, with an initial boiling point of 20-40°C. o C, final boiling point is 55~65 o C; The hydrogenated heavy naphtha is extracted from plates 5 to 30 of the side-stream rectification zone of the adjacent distillation column, with an initial boiling point of 55-65°C. o C, final boiling point is 140~170 o C; The hydrotreated light diesel oil is extracted from any location below the hydrotreated heavy naphtha extraction point in the side-stream rectification zone, with an initial boiling point of 140-170°C. o C, final boiling point is 230~280 o C; and / or The hydrotreated heavy diesel oil is separated from the lower part of the common stripping section of the distillation column, with an initial boiling point of 230~280°C. o C.

13. The catalytic conversion method according to claim 12, characterized in that, The hydrotreated heavy naphtha is extracted from plates 10-20 of the side-stream rectification zone of the adjacent distillation column; and / or The hydrogenated light diesel oil is extracted from plates 25 to 35 of the side-stream distillation zone.

14. The catalytic conversion method according to claim 2, characterized in that, In step (3), the initial boiling point of the catalytic naphtha is 20-40 °C. o C, final boiling point is 140~160 o C; The initial boiling point of the catalytic heavy aromatic fraction is 140~160°C. o C, final boiling point is 210~250 o C; and / or The initial boiling point of the catalytic cracking cycle oil is 210~250°C. o C, final boiling point is 320~360 o C.

15. The catalytic conversion method according to claim 1, characterized in that, In step (3), the conditions for the catalytic cracking reaction include: The heavy hourly space velocity of oil and gas is 4~20h. -1 ; The catalytic cracking reaction temperature is 520~650℃ o C; and / or The weight ratio of the agent to oil is 6~26.

16. The catalytic conversion method according to claim 15, characterized in that, In step (3), the conditions for the catalytic cracking reaction include: The heavy hourly space velocity of oil and gas is 8–16 h⁻¹. -1 ; The catalytic cracking reaction temperature is 560~640℃ o C; and / or The weight ratio of the agent to oil is 8~20.

17. The catalytic conversion method according to claim 1, characterized in that, In step (3), the catalytic cracking catalyst contains 10-60 parts by weight of molecular sieve, 1-40 parts by weight of binder and 1-90 parts by weight of support; The molecular sieve is selected from one or more of ZSM molecular sieve, Y molecular sieve, HY molecular sieve, USY molecular sieve and Beta molecular sieve; The adhesive is selected from silica adhesives and / or alumina adhesives; The carrier is selected from one or more of the following: silica, kaolin, montmorillonite, diatomite, halloysite, soapstone, rettosite, sepiolite, attapulgite, hydrotalcite, and bentonite.

18. The catalytic conversion method according to claim 17, characterized in that, The molecular sieve contains rare earth elements, which are one or more of La, Ce, Pr, and Nd.

19. A catalytic conversion system for producing light aromatics, comprising: The hydrogenation unit is a two-stage hydrogenation unit, which is provided with a hydrogen inlet and a hydrogenated oil / gas outlet. The first stage of the hydrogenation unit is provided with a catalytic cracking cycle oil inlet, and the second stage of the hydrogenation unit is provided with a hydrogenated heavy diesel oil inlet. A partition distillation column is provided, wherein at least one partition wall is provided within the partition distillation column, dividing the column into four regions: a common stripping section at the bottom of the column, a common rectification section at the top of the column, a pre-separation zone in the middle section of the column, and a side-stream rectification zone. The pre-separation zone is provided with a hydrotreated oil / gas inlet, which is connected to the hydrotreated oil / gas outlet of the hydrotreating unit. The common rectification section is provided with a low-boiling-point fraction outlet. The side-stream rectification zone is provided with a hydrotreated heavy naphtha rich in light aromatics outlet and a hydrotreated light diesel oil outlet. The bottom of the common stripping section is provided with a hydrotreated heavy diesel oil outlet, which is connected to the hydrotreated heavy diesel oil inlet on the second section of the hydrotreating unit. The catalytic cracking unit includes a hydrotreated light diesel oil inlet, a dry gas outlet, a liquefied petroleum gas (LPG) outlet, a catalytic naphtha-rich outlet, a catalytic heavy aromatics outlet, a catalytic cracking cycle oil outlet, and a slurry oil outlet. The catalytic heavy aromatics outlet is connected to a catalytic heavy aromatics fractionation pipeline, and the catalytic cracking cycle oil outlet is connected to the catalytic cracking cycle oil inlet on the first section of the hydrotreating unit. The pre-separation zone of the partition distillation column has 10 to 40 trays. The number of trays in the common rectification section is 2 to 10. The common stripping section has 2 to 10 trays; and / or The number of trays in the side-stream distillation zone is 10 to 45.

20. The catalytic conversion system according to claim 19, characterized in that, The catalytic heavy aromatics fractionation pipeline is connected to the inlet of the hydrotreated light diesel oil.

21. The catalytic conversion system according to claim 19, characterized in that, The catalytic cracking unit is a single reactor or a dual reactor.

22. The catalytic conversion system according to claim 21, wherein the reactor is selected from one or more of the following: constant diameter riser, constant linear velocity riser, variable diameter riser, variable linear velocity riser, fluidized bed, and composite reactor, wherein the composite reactor is composed of a constant diameter or variable diameter riser and a fluidized bed.

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