A method and system for the production of light aromatics

Abstract

The application provides a method and system for producing light aromatic hydrocarbons, which comprises: feeding catalytic cracking raw oil into a first reaction zone of a catalytic cracking device for catalytic conversion to obtain reaction oil gas; feeding the reaction oil gas into a first rectifying tower after gas-solid separation from the catalyst to separate a first fraction oil gas, a second fraction oil and oil slurry; feeding the second fraction oil into a diesel hydrogenation device for hydrotreating; feeding the first fraction oil gas and hydrogenated oil gas from the diesel hydrogenation device into a second rectifying tower after degassing separation of the rich gas to separate a naphtha fraction rich in light aromatic hydrocarbons, a heavy aromatic fraction and a diesel fraction; and feeding the heavy aromatic fraction and the diesel fraction into a second reaction zone and the first reaction zone of the catalytic cracking device respectively for partitioned catalytic conversion. The application effectively separates the catalytic conversion products and the catalytic diesel hydrogenation products in the same separation system and then performs partitioned catalytic conversion, thereby improving the yield of light aromatic hydrocarbons and saving the investment in separation device equipment.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, and more specifically, to a method and system for producing more light aromatic hydrocarbons. Background Technology

[0002] Light aromatic hydrocarbons (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 aromatic hydrocarbons is increasing and currently remains in a state of supply shortage.

[0003] Oil refineries generate large quantities of products containing heavy aromatics during actual production, such as heavy gasoline and heavy naphtha, which have low market demand. These products are rich in monocyclic and polycyclic aromatic hydrocarbons with a high number of carbon atoms and can theoretically be used to produce light aromatics.

[0004] ZL201911047207.3 discloses a method for producing light aromatics. The method involves contacting a feedstock containing heavy aromatics with a catalyst in a fluidized bed reactor under hydrogen conditions to undergo a light aromatics-rich reaction, yielding a product rich in light aromatics and a catalyst to be generated. The resulting product is then separated to obtain hydrogen, non-aromatic components, C6-C8 light aromatics, and C9+ aromatic components, with at least a portion of the C9+ aromatic components being returned to the fluidized bed reactor. This method can produce light aromatics from heavy aromatics. However, the conversion of the feedstock containing heavy aromatics requires a hydrogen-rich unit, and the separation and reuse of C9+ aromatics from the product involves a long process, resulting in significant investment and energy consumption for industrial implementation.

[0005] Patent ZL201610917106.7 discloses a catalytic cracking method for producing low-carbon olefins and light aromatics. In this method, heavy feedstock reacts with a first-stage catalytic cracking catalyst in a first reactor (riseer reactor I), while light feedstocks rich in saturated hydrocarbons and olefins react with a second-stage catalytic cracking catalyst in a second reactor (riseer reactor II) and a third reactor (fluidized bed reactor) to increase the production of low-carbon olefins and light aromatics. This patented method utilizes a catalytic cracking partitioning conversion approach to achieve the goal of increasing light aromatics production.

[0006] Using catalytic cracking units to convert feedstocks containing heavy aromatics can save on equipment investment. Furthermore, effectively separating and reprocessing the heavy aromatics produced by the catalytic cracking unit can further improve the yield of light aromatics. Summary of the Invention

[0007] The purpose of this invention is to effectively separate catalytic conversion products and catalytic hydrogenation products in the same separation system and then perform zoned catalytic conversion, thereby improving the yield of light aromatics while saving investment in separation equipment.

[0008] To achieve the above objectives, the present invention provides a method for producing more light aromatics. The method includes: feeding catalytic cracking feedstock into the first reaction zone of a catalytic cracking unit for catalytic conversion to obtain reaction oil gas; separating the reaction oil gas from the catalyst gas-solid mixture and then feeding it into a first distillation column to separate a first fraction oil gas, a second fraction oil, and an oil slurry; feeding the second fraction oil into a diesel hydrotreating unit for hydrotreating; and degassing the first fraction oil gas and the hydrotreated oil gas from the diesel hydrotreating unit together to separate rich gas to obtain the first fraction oil, which then enters a second distillation column to separate naphtha fraction rich in light aromatics, heavy aromatics fraction, and diesel fraction; and feeding the heavy aromatics fraction and diesel fraction into the second reaction zone and the first reaction zone of the catalytic cracking unit, respectively, for zoned catalytic conversion.

[0009] A first aspect of the present invention provides a method for producing more light aromatic hydrocarbons, the method comprising:

[0010] (1) The feedstock oil for catalytic cracking enters the first reaction zone of the catalytic cracking unit and comes into contact with the catalyst for catalytic cracking to obtain the first reaction oil and gas;

[0011] (2) After the first reaction oil and gas are separated from the catalyst gas and solid, they enter the first distillation column to separate the first fraction oil and gas, the second fraction oil and oil slurry;

[0012] (3) The second fraction oil obtained in step (2) is subjected to hydrogenation treatment. Hydrogen is separated from the hydrogenation product obtained by hydrogenation treatment to obtain hydrogenated oil gas. The hydrogenated oil gas and the first fraction oil gas are degassed and separated to obtain rich gas and the first fraction oil.

[0013] (4) The first distillate obtained in step (3) enters the second distillation column and is separated to obtain naphtha fraction rich in light aromatics, heavy aromatics fraction and diesel fraction;

[0014] (5) The heavy aromatic fraction obtained in step (4) is sent to the second reaction zone of the catalytic cracking unit, and the diesel fraction is sent to the first reaction zone of the catalytic cracking unit for catalytic conversion.

[0015] According to the method of the first aspect, in step (1), the catalytic cracking feedstock is selected from at least one of hydrotreated diesel, straight-run diesel, straight-run wax oil, hydrotreated wax oil, hydrotreated cracking tail oil, and hydrotreated residue oil, and the diesel fraction separated from the second distillation column.

[0016] According to the method of the first aspect, in step (1), the conditions for catalytic transformation in the first reaction zone are:

[0017] The heavy hourly space velocity of oil and gas is 4~20h. -1 Preferably 6~12h -1 ;

[0018] The reaction time is 1~10s, preferably 2~6s; and / or

[0019] The weight ratio of the agent to oil is 4 to 14, preferably 6 to 10.

[0020] According to the method of the first aspect, in step (2), the initial boiling point of the first distillate oil and gas is 0~40℃ and the final boiling point is 220~250℃;

[0021] The second distillate oil has an initial boiling point of 220-250°C and a final boiling point of 340-360°C; and / or

[0022] The initial boiling point of the oil slurry is 340~360℃.

[0023] According to the method of the first aspect, in step (3), the hydrogenation treatment is hydrorefining, hydromodification, or hydrocracking; and / or

[0024] The initial boiling point of the hydrogenated oil and gas is 0~60℃, and the final boiling point is 280~350℃.

[0025] According to the method of the first aspect, in step (4), the initial boiling point of the naphtha fraction is 20~40℃ and the final boiling point is 140~160℃;

[0026] The initial boiling point of the heavy aromatic fraction is 140~160℃, and the final boiling point is 210~250℃;

[0027] The initial boiling point of the diesel fraction is 210~250℃, and the final boiling point is 280~350℃.

[0028] According to the method of the first aspect, in step (5), the conditions for catalytic transformation in the second reaction zone are:

[0029] The heavy hourly space velocity of oil and gas is 4~20h. -1 8~16h preferred -1 ;

[0030] The reaction time is 0.1~5s, preferably 0.5~3s; and / or

[0031] The weight ratio of the agent to oil is 6 to 26, preferably 10 to 22.

[0032] According to the method of the first aspect, in step (2), the pressure at the top of the first distillation column is 0.1~0.5MPa, preferably 0.2~0.4MPa.

[0033] According to the method of the first aspect, in step (4), the second distillation column is a conventional distillation column or a partitioned distillation column;

[0034] Preferably, the top pressure of the second distillation column is 0.1~1.0 MPa, more preferably 0.2~0.7 MPa; and / or

[0035] The top temperature of the second distillation column is 50~120°C. o C, more preferably 60~100 o C;

[0036] More preferably, the second distillation column has 30 to 50 trays, more preferably 35 to 45; the naphtha fraction rich in light aromatics is extracted from the top 10 to 40 trays, preferably the 15 to 30 trays, of the side stream of the second distillation column.

[0037] According to the method of the first aspect, the second distillation column is a partitioned distillation column, and at least one partition wall is provided in the partitioned distillation column, which divides the partitioned distillation column into four areas: a pre-separation zone, a common distillation section, a common stripping section, and a side-stream distillation zone, and the oil and gas feed position is located in the pre-separation zone;

[0038] Preferably, the number of trays in the pre-separation zone of the partition distillation column is 10-40, more preferably 20-35; the number of trays in the common rectification section is 3-20, more preferably 5-15; the number of trays in the common stripping section is 2-10, more preferably 3-8; and / or the number of trays in the side-stream rectification zone is 10-45, more preferably 25-40.

[0039] More preferably, 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 to 10, preferably 0.5 to 5; and / or

[0040] More preferably, the ratio of the gas mass flow rate entering the pre-separation zone from the common stripping section to the side-stream rectification zone is 1 to 15, more preferably 2 to 10.

[0041] According to the method of the first aspect, in step (1), the catalyst is a catalytic cracking catalyst, the catalyst comprising 10 to 60 parts by weight of molecular sieve, 1 to 40 parts by weight of binder and 1 to 90 parts by weight of support;

[0042] 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.

[0043] The adhesive is a silica adhesive and / or an alumina adhesive; and / or

[0044] The carrier is selected from one or more of the following: silica, kaolin, montmorillonite, diatomite, halloysite, soapstone, rettosite, sepiolite, attapulgite, hydrotalcite, and bentonite.

[0045] A second aspect of the present invention provides a system for producing light aromatic hydrocarbons, comprising:

[0046] A catalytic cracking unit includes:

[0047] The reactor is provided with a first reaction zone and a second reaction zone, wherein the first reaction zone and the second reaction zone are connected in series and the second reaction zone is located upstream of the first reaction zone, and the catalyst contacts the feed oil in sequence through the second reaction zone and the first reaction zone.

[0048] A gas-solid separator is connected to the oil-catalyst mixture outlet of the first reaction zone of the reactor, thereby separating the first reaction oil-gas from the catalyst in the first reaction zone.

[0049] The first distillation column is provided with a first fraction oil and gas outlet, a second fraction oil outlet and an oil slurry outlet. The inlet of the first distillation column is connected to the outlet of the catalytic cracking unit through a pipeline.

[0050] A diesel hydrogenation unit is provided with a diesel inlet, a hydrogen inlet, and a hydrogenation product outlet. The diesel inlet of the diesel hydrogenation unit is connected to the second distillate oil outlet of the first distillation column.

[0051] The high-low separation device is provided with a hydrogenation product inlet, a hydrogen outlet and a hydrogenated oil and gas outlet. The hydrogenation product inlet is connected to the hydrogenation product outlet of the diesel hydrogenation unit. The high-low separation device separates the hydrogenated oil and gas from the hydrogenation product from the diesel hydrogenation unit.

[0052] A degassing separation device is provided with an oil and gas inlet, a rich gas outlet and a first distillate oil outlet. The oil and gas inlet of the degassing separation device is connected to the first distillate oil and gas outlet of the first distillation column and the hydrogenated oil and gas outlet of the high and low separation unit, so that the first distillate oil and gas from the first distillation column and the hydrogenated oil and gas from the high and low separation unit are degassed and separated into rich gas and first distillate oil.

[0053] The second distillation column is provided with a first distillate oil inlet, a naphtha distillate outlet, a heavy aromatics distillate outlet, and a diesel distillate outlet. The first distillate oil inlet is connected to the first distillate oil outlet of the degassing and separation unit. The heavy aromatics distillate outlet is connected to the second reaction zone of the reactor of the catalytic cracking unit. The diesel distillate outlet is connected to the first reaction zone of the reactor of the catalytic cracking unit.

[0054] According to the system of the second aspect, the reactor is selected from one or two 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.

[0055] The first reaction zone and the second reaction zone are located on the same or different reactors.

[0056] According to the system of the second aspect, the first distillation column is a conventional distillation column with 20 to 40 trays, preferably 25 to 35, and the second distillate oil is collected from the top 5 to 30 trays, preferably the 10 to 25 trays, of the first distillation column side stream;

[0057] Preferably, the first distillation column is heated by a vapor feed, and the bottom of the column is stripped with steam; and / or

[0058] Preferably, one or more intermediate-section heat recovery sections can be provided on the side stream of the first distillation column.

[0059] According to the system of the second aspect, the first distillation column and / or the second distillation column are equal-diameter distillation columns or variable-diameter distillation columns.

[0060] Through the above technical solution, the present invention further separates the first fraction of oil and gas produced by catalytic cracking and the hydrogenated oil and gas of the diesel hydrotreating unit into naphtha fraction rich in light aromatics and heavy aromatics fraction in the same fractionating tower. At the same time, the separated heavy aromatics fraction is sent to the catalytic cracking unit for zoned conversion, so as to achieve full conversion of heavy aromatics fraction, improve the yield of light aromatics, and save equipment investment.

[0061] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0062] 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:

[0063] Figure 1 This is a schematic diagram of the system structure in a preferred embodiment of the present invention.

[0064] Figure 2 This is a schematic diagram of the comparative system structure of the present invention.

[0065] Explanation of reference numerals in the attached figures:

[0066] 100. Catalytic cracking riser reactor; 200. First distillation column; 300. Diesel hydrotreating unit; 400. Second distillation column; 500. First hydrotreating distillation column; 600. Second hydrotreating distillation column; 700. High and low separation unit;

[0067] 101. Inlet to the first reaction zone; 102. Inlet to the second reaction zone; 103. Inlet to the fluidizing medium; 104. Second reaction zone; 105. First reaction zone; 106. Reaction oil and gas pipeline;

[0068] 201. First distillate oil pipeline; 202. Second distillate oil pipeline; 203. Bottom stripping steam pipeline;

[0069] 301. Catalytic diesel inlet; 302. Hydrogenation product pipeline; 303. Hydrogenation oil and gas pipeline;

[0070] 401. Pre-separation zone; 402. Common rectification section; 403. Common stripping section; 404. Side stream rectification zone; 405. Partition wall;

[0071] 501. >150°C Hydrogenation Fraction Pipeline;

[0072] A, A′, A″. Gas-rich; B, B′, B″. Naphtha fraction rich in light aromatics; C, C′, C″. Heavy aromatics fraction; D, D″. Diesel fraction; E. Oil slurry. Detailed Implementation

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 invention. 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.

[0079] Before describing the technical solution of this invention, the terms used herein are defined as follows:

[0080] The term "initial boiling point" refers to the temperature at which the boiling range begins.

[0081] The term "final boiling point" refers to the temperature at the end of the distillation process.

[0082] The light aromatic hydrocarbons mentioned in this invention refer to C6-C8 aromatic hydrocarbons.

[0083] This invention provides a method for producing more light aromatics, the method comprising:

[0084] (1) The feedstock oil for catalytic cracking enters the first reaction zone of the catalytic cracking unit and comes into contact with the catalyst for catalytic cracking to obtain the first reaction oil and gas;

[0085] (2) After the first reaction oil and gas are separated from the catalyst gas and solid, they enter the first distillation column to separate the first fraction oil and gas, the second fraction oil and oil slurry;

[0086] (3) The second fraction oil obtained in step (2) is subjected to hydrogenation treatment. Hydrogen is separated from the hydrogenation product obtained by hydrogenation treatment to obtain hydrogenated oil gas. The hydrogenated oil gas and the first fraction oil gas are degassed and separated to obtain rich gas and the first fraction oil.

[0087] (4) The first distillate obtained in step (3) enters the second distillation column and is separated to obtain naphtha fraction rich in light aromatics, heavy aromatics fraction and diesel fraction;

[0088] (5) The heavy aromatic fraction obtained in step (4) is sent to the second reaction zone of the catalytic cracking unit, and the diesel fraction is sent to the first reaction zone of the catalytic cracking unit for catalytic conversion.

[0089] In one embodiment, in step (1), the catalytic cracking feedstock is selected from at least one of hydrotreated diesel, straight-run diesel, straight-run wax oil, hydrotreated wax oil, hydrotreated cracking tail oil, and hydrotreated residue oil, as well as the diesel fraction separated from the second distillation column.

[0090] Optionally, the first and second reaction zones of the catalytic cracking unit may be located on the same riser reactor, with the catalyst sequentially passing through the two reaction zones from bottom to top to react with the feedstock oil. Alternatively, the two reaction zones may be located on two separate riser reactors.

[0091] The inventors of this invention discovered that effectively separating catalytic cracking products and catalytic diesel hydrotreating products, and then returning the heavy aromatics fraction to the catalytic cracking riser for zoned conversion, can improve the yield of light aromatics from catalytic cracking. This invention effectively separates catalytic conversion products and catalytic diesel hydrotreating products in the same separation system, followed by zoned catalytic conversion, thereby increasing the yield of light aromatics while saving on investment in separation equipment.

[0092] In one embodiment, in step (1), the conditions for catalytic conversion in the first reaction zone are:

[0093] The heavy hourly space velocity of oil and gas is 4~20h. -1 Preferably 6~12h -1 ;

[0094] The reaction time is 1~10s, preferably 2~6s; and / or

[0095] The weight ratio of the agent to oil is 4 to 14, preferably 6 to 10.

[0096] In one embodiment, in step (2), the initial boiling point of the first distillate oil and gas is 0~40℃, and the final boiling point is 220~250℃;

[0097] The second distillate oil has an initial boiling point of 220-250°C and a final boiling point of 340-360°C; and / or

[0098] The initial boiling point of the oil slurry is 340~360℃.

[0099] In one embodiment, in step (3), the hydrogenation treatment is hydrorefining, hydromodification, or hydrocracking; and / or

[0100] The initial boiling point of the hydrogenated oil and gas is 0~60℃, and the final boiling point is 280~350℃.

[0101] In one embodiment, in step (4), the initial boiling point of the naphtha fraction is 20~40℃, and the final boiling point is 140~160℃.

[0102] The initial boiling point of the heavy aromatic fraction is 140~160℃, and the final boiling point is 210~250℃;

[0103] The initial boiling point of the diesel fraction is 210~250℃, and the final boiling point is 280~350℃.

[0104] In one embodiment, in step (5), the conditions for catalytic conversion in the second reaction zone are:

[0105] The heavy hourly space velocity of oil and gas is 4~20h. -1 8~16h preferred -1 ;

[0106] The reaction time is 0.1~5s, preferably 0.5~3s; and / or

[0107] The weight ratio of the agent to oil is 6 to 26, preferably 10 to 22.

[0108] In one embodiment, in step (2), the pressure at the top of the first distillation column is 0.1~0.5MPa, preferably 0.2~0.4MPa.

[0109] In one embodiment, in step (4), the second distillation column is a conventional distillation column or a partitioned distillation column;

[0110] Preferably, the top pressure of the second distillation column is 0.1~1.0 MPa, more preferably 0.2~0.7 MPa; and / or

[0111] The top temperature of the second distillation column is 50~120°C. o C, more preferably 60~100 o C;

[0112] More preferably, the second distillation column has 30 to 50 trays, more preferably 35 to 45; the naphtha fraction rich in light aromatics is extracted from the top 10 to 40 trays, preferably the 15 to 30 trays, of the side stream of the second distillation column.

[0113] In one embodiment, the second distillation column is a partitioned distillation column, and at least one partition wall is provided in the partitioned distillation column. The partition wall divides the partitioned distillation column into four areas: a pre-separation zone, a common distillation section, a common stripping section, and a side-stream distillation zone. The oil and gas feed position is located in the pre-separation zone.

[0114] Preferably, the number of trays in the pre-separation zone of the partition distillation column is 10-40, more preferably 20-35; the number of trays in the common rectification section is 3-20, more preferably 5-15; the number of trays in the common stripping section is 2-10, more preferably 3-8; and / or the number of trays in the side-stream rectification zone is 10-45, more preferably 25-40.

[0115] More preferably, 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 to 10, preferably 0.5 to 5; and / or

[0116] More preferably, the ratio of the gas mass flow rate entering the pre-separation zone from the common stripping section to the side-stream rectification zone is 1 to 15, more preferably 2 to 10.

[0117] This invention employs a partitioned distillation column to precisely separate the heavy aromatics fraction and diesel fraction from catalytic cracking and diesel hydrotreating products, and then convert them in the catalytic cracking zone, thereby improving the utilization efficiency of aromatics and maximizing the production of light aromatics from catalytic cracking.

[0118] In one embodiment, in step (1), the catalyst is a catalytic cracking catalyst, which includes 10-60 parts by weight of molecular sieve, 1-40 parts by weight of binder and 1-90 parts by weight of support.

[0119] 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.

[0120] The adhesive is a silica adhesive and / or an alumina adhesive; and / or

[0121] The carrier is selected from one or more of the following: silica, kaolin, montmorillonite, diatomite, halloysite, soapstone, rettosite, sepiolite, attapulgite, hydrotalcite, and bentonite.

[0122] The present invention also provides a system for producing light aromatic hydrocarbons, comprising:

[0123] A catalytic cracking unit includes:

[0124] The reactor is provided with a first reaction zone and a second reaction zone, wherein the first reaction zone and the second reaction zone are connected in series and the second reaction zone is located upstream of the first reaction zone, and the catalyst contacts the feed oil in sequence through the second reaction zone and the first reaction zone.

[0125] A gas-solid separator is connected to the oil-catalyst mixture outlet of the first reaction zone of the reactor, thereby separating the first reaction oil-gas from the catalyst in the first reaction zone.

[0126] The first distillation column is provided with a first fraction oil and gas outlet, a second fraction oil outlet and an oil slurry outlet. The inlet of the first distillation column is connected to the outlet of the catalytic cracking unit through a pipeline.

[0127] A diesel hydrogenation unit is provided with a diesel inlet, a hydrogen inlet, and a hydrogenation product outlet. The diesel inlet of the diesel hydrogenation unit is connected to the second distillate oil outlet of the first distillation column.

[0128] The high-low separation device is provided with a hydrogenation product inlet, a hydrogen outlet and a hydrogenated oil and gas outlet. The hydrogenation product inlet is connected to the hydrogenation product outlet of the diesel hydrogenation unit. The high-low separation device separates the hydrogenated oil and gas from the hydrogenation product from the diesel hydrogenation unit.

[0129] A degassing separation device is provided with an oil and gas inlet, a rich gas outlet and a first distillate oil outlet. The oil and gas inlet of the degassing separation device is connected to the first distillate oil and gas outlet of the first distillation column and the hydrogenated oil and gas outlet of the high and low separation unit, so that the first distillate oil and gas from the first distillation column and the hydrogenated oil and gas from the high and low separation unit are degassed and separated into rich gas and first distillate oil.

[0130] The second distillation column is provided with a first distillate oil inlet, a naphtha distillate outlet, a heavy aromatics distillate outlet, and a diesel distillate outlet. The first distillate oil inlet is connected to the first distillate oil outlet of the degassing and separation unit. The heavy aromatics distillate outlet is connected to the second reaction zone of the reactor of the catalytic cracking unit. The diesel distillate outlet is connected to the first reaction zone of the reactor of the catalytic cracking unit.

[0131] In one embodiment, the reactor is selected from one or two 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;

[0132] The first reaction zone and the second reaction zone are located on the same or different reactors.

[0133] In one embodiment, the first distillation column is a conventional distillation column with 20 to 40 trays, preferably 25 to 35, and the second distillate oil is collected from the top 5 to 30 trays, preferably 10 to 25 trays, of the first distillation column.

[0134] Preferably, the first distillation column is heated by a vapor feed, and the bottom of the column is stripped with steam; and / or

[0135] Preferably, one or more intermediate-section heat recovery sections can be provided on the side stream of the first distillation column.

[0136] In one embodiment, the second distillation column is a conventional distillation column or a partitioned distillation column, with 30 to 50 trays, preferably 35 to 45; the naphtha fraction rich in light aromatics is collected from the top 10 to 40 trays, preferably the 15 to 30 trays, of the side stream of the second distillation column.

[0137] In one embodiment, the first distillation column and / or the second distillation column are equal-diameter distillation columns or variable-diameter distillation columns.

[0138] refer to Figure 1 In a preferred embodiment of the present invention, the catalyst enters the catalytic cracking riser reactor 100 through the catalyst inlet under the action of the fluidizing medium, and passes upward sequentially through the second reaction zone 104 and the first reaction zone 105. The catalytic cracking feedstock oil, after being preheated, enters the first reaction zone 105 of the catalytic cracking riser reactor 100 through the first reaction zone inlet 101 to react with the catalyst. The fluidizing medium enters the catalytic cracking riser reactor 100 through the fluidizing medium inlet 103. After the reaction, the catalyst is stripped and separated from the reaction oil and gas in the gas-solid separator. After leaving the gas-solid separator, the reaction oil and gas enter the first distillation column 200 through the reaction oil and gas pipeline 106 for separation. The reaction oil and gas are separated into three fractions with boiling points from low to high through the first distillation column 200. The first fraction oil and gas is separated at the top of the column, the second fraction oil is separated in the middle of the column, and the oil slurry E is separated at the bottom of the column. The bottom of the first distillation column 200 is provided with a bottom stripping steam pipeline 203. The second fraction oil enters the catalytic diesel hydrotreating unit 300 via the second fraction oil pipeline 202 for hydrotreating. Hydrogen and the second fraction oil enter the catalytic diesel hydrotreating unit through the hydrogen inlet and catalytic diesel inlet 301, respectively. The hydrotreating product enters the high-low separation unit 700 via the hydrotreating product pipeline 302, where hydrogen is separated to obtain hydrotreated oil gas. This hydrotreated oil gas, along with the first fraction oil gas, undergoes degassing treatment via the hydrotreated oil gas pipeline 303 to separate rich gas A. The resulting first fraction oil enters the second rectification column 400 for further separation. The common rectification section at the top of the second rectification column 400 separates naphtha fraction B, rich in light aromatics; the side stream rectification section separates heavy aromatics fraction C; and the common stripping section at the bottom separates diesel fraction D. Diesel fraction D returns to the inlet 101 of the first reaction zone of the catalytic cracking riser reactor 100, while heavy aromatics fraction C returns to the inlet 102 of the second reaction zone of the catalytic cracking riser reactor 100 for further catalytic conversion.

[0139] 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.

[0140] The catalysts used in the examples and comparative examples were purchased from the brand name SLA-1.

[0141] The properties of the first feedstock oil used in the examples and comparative examples are shown in Table 1.

[0142] Table 1

[0143]

[0144] Example

[0145] refer to Figure 1 The catalytic cracking riser reactor 100 is a riser reactor with a constant diameter. Fluidizing medium enters the catalytic cracking riser reactor 100 through fluidizing medium inlet 103. The feedstock for catalytic cracking is hydrotreated diesel oil, which, after preheating, enters the first reaction zone of the catalytic cracking riser reactor 100 through the first reaction zone inlet 101 at a feed rate of 40 g / min along with atomized steam. The reaction time is 3 s, the reactant-to-oil mass ratio is 10, and the weight hourly space velocity is 10 h⁻¹. -1 The reaction occurs under certain conditions with the catalyst. After stripping, the catalyst is separated from the reaction oil and gas. The reaction oil and gas then enters the first distillation column at 200°C for separation, yielding three fractions with increasing boiling points. The first fraction (initial to 240°C) is separated from the top of the column. o C), the second distillate oil (240~350) is separated in the middle of the tower. o C), greater than 350 separated at the bottom of the tower o C's oil slurry E. The second fraction oil enters the catalytic diesel hydrotreating unit 300 through the second fraction oil pipeline 202 for hydrotreating. The hydrotreating product is separated into hydrogen by the high and low separation unit 700. The resulting hydrotreated oil gas and the first fraction oil gas are degassed to separate the rich gas and then enter the second rectification column 400 for separation, separating the naphtha fraction B (25~150) rich in light aromatics. o C), heavy aromatics fraction C (150~240) o C), Diesel fraction D (>240) o C), diesel fraction D and heavy aromatic fraction C are returned to the first and second reaction zones of the riser reactor for conversion, respectively. The reaction time in the second reaction zone is 1.0 s, the catalyst-to-oil mass ratio is 20, and the heavy hourly space velocity is 13 h⁻¹. -1 The first distillation column is a conventional constant-diameter distillation column with 30 trays and a pressure of 0.25 MPa. The second distillate oil (240~350) is produced as a side stream. o C) The 20th tray is the sampling point. The second distillation column is a partitioned distillation column, with one partition wall installed inside to radially separate the column. The number of trays in the pre-separation zone, common rectification section, common stripping section, and side-stream rectification zone are 34, 10, 4, and 36, respectively. The reflux ratio at the top of the column is 6. The heavy aromatic fraction C (150~240) o C) The sample is taken from the 20th plate from the bottom up in the side stream separation zone. The pressure at the top of the adjacent distillation column is 0.4 MPa, and the temperature at the top is 67°C. o C. The number of trays and reflux ratio of the distillation column are shown in Table 2. The product composition is shown in Table 3.

[0146] Comparative Example

[0147] The comparative example uses the current conventional catalytic cracking process flow, with reference to... Figure 2 The feedstock, hydrotreated diesel, and catalyst are the same as in the previous example. The hydrotreated diesel, after preheating, is fed into the riser reactor at a feed rate of 40 g / min along with atomizing medium steam. The reaction time is 3 seconds, the catalyst-to-oil mass ratio is 10, and the weight hourly space velocity is 10 h⁻¹. -1 The reaction occurs under certain conditions with the catalyst. After stripping, the catalyst is separated from the reaction oil and gas in a gas-solid separator. The reaction oil and gas then enter a conventional first distillation column (200°C) for separation. The first distillation column has 30 trays. The oil and gas are separated into three fractions with boiling points from low to high, with fractions below 210°C. o The first fraction of oil and gas is separated from the top of the column, and the lower part of the distillation column is separated at 210~350. o C's diesel fraction, with a bottom extract exceeding 350 o C's oil slurry E. Less than 210 o After separating the rich gas A' from the first fraction of oil and gas, the first fraction oil obtained enters the second distillation column 400 through the first fraction oil pipeline 201. The second distillation column has 40 trays and a reflux ratio of 2, separating the naphtha fraction B' (25~150) rich in light aromatics. o C) and heavy aromatic fraction C' (150~210) o C). 210~350 o Diesel fraction C enters diesel hydrotreating unit 300 via second fraction oil pipeline 202. After the hydrotreating product is separated into recirculating hydrogen by high and low separation unit 700, the resulting hydrotreated oil and gas pass through first hydrotreating distillation column 500. First hydrotreating distillation column 500 has 30 trays and a reflux ratio of 0.8. Rich gas A'' and light naphtha fraction B'' (25...) are separated at the top of the column. o C~150 o C), >150 separated from the bottom of the tower o The C fraction enters the second hydrotreating distillation column 600 via pipeline 501. The second hydrotreating distillation column 600 has 10 trays and a reflux ratio of 1.8. 150-250 mg / L is separated at the top of the column. o C'', heavy aromatics fraction C'', >250g separated at the bottom of the column o C, the hydrotreated diesel fraction D'', enters the catalytic cracking riser reactor 100. The number of trays and reflux ratio of the distillation column are shown in Table 2. The product composition is shown in Table 3.

[0148] Table 2

[0149]

[0150] Table 3

[0151]

[0152] As can be seen from Table 3, compared with the comparative example, the yield of C6-C8 light aromatics in the examples was 6.97 percentage points higher, generating significant economic value.

[0153] Based on Aspen, the energy consumption of the implementation examples and comparative examples was calculated, and the comparison is shown in Table 3.

[0154] By integrating and optimizing the repetitive separation sequences of the diesel cracking unit and the catalytic unit, equipment investment and process complexity can be significantly reduced while keeping the total energy consumption basically unchanged.

[0155] 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 method for producing more light aromatics, characterized in that, The method includes: (1) The feedstock oil for catalytic cracking enters the first reaction zone of the catalytic cracking unit and comes into contact with the catalyst for catalytic cracking to obtain the first reaction oil and gas; (2) After the first reaction oil and gas are separated from the catalyst gas and solid, they enter the first distillation column to separate the first fraction oil and gas, the second fraction oil and oil slurry; (3) The second fraction oil obtained in step (2) is subjected to hydrogenation treatment. Hydrogen is separated from the hydrogenation product obtained by hydrogenation treatment to obtain hydrogenated oil gas. The hydrogenated oil gas and the first fraction oil gas are degassed and separated to obtain rich gas and the first fraction oil. (4) The first distillate obtained in step (3) enters the second distillation column and is separated to obtain naphtha fraction rich in light aromatics, heavy aromatics fraction and diesel fraction; (5) The heavy aromatics fraction obtained in step (4) is fed into the second reaction zone of the catalytic cracking unit, and the diesel fraction is fed into the first reaction zone of the catalytic cracking unit for catalytic conversion. The second distillation column is a partitioned distillation column, which is provided with at least one partition wall. The partition wall divides the partitioned distillation column into four areas: a pre-separation zone, a common distillation section, a common stripping section, and a side-stream distillation zone. The oil and gas feed is located in the pre-separation zone. The pre-separation zone of the distillation column has 10 to 40 trays; the common rectification section has 3 to 20 trays; the common stripping section has 2 to 10 trays; and / or the side-stream rectification section has 10 to 45 trays.

2. The method according to claim 1, characterized in that, In step (1), the catalytic cracking feedstock is selected from at least one of hydrotreated diesel, straight-run diesel, straight-run wax oil, hydrotreated wax oil, hydrotreated cracking tail oil, and hydrotreated residue oil, as well as the diesel fraction separated from the second distillation column.

3. The method according to claim 1, characterized in that, In step (1), the conditions for catalytic conversion in the first reaction zone are: The heavy hourly space velocity of oil and gas is 4~20h. -1 ; The reaction time is 1~10s; and / or The weight ratio of the agent to oil is 4~14.

4. The method according to claim 3, characterized in that, In step (1), the conditions for catalytic conversion in the first reaction zone are: The heavy hourly space velocity of oil and gas is 6-12 h⁻¹. -1 ; The reaction time is 2-6 seconds; and / or The weight ratio of the agent to oil is 6-10.

5. The method according to claim 1, characterized in that, In step (2), the initial boiling point of the first distillate oil and gas is 0~40℃, and the final boiling point is 220~250℃; The second distillate oil has an initial boiling point of 220-250°C and a final boiling point of 340-360°C; and / or The initial boiling point of the oil slurry is 340~360℃.

6. The method according to claim 1, characterized in that, In step (3), the hydrotreating process is hydrorefining, hydromodification, or hydrocracking; and / or The initial boiling point of the hydrogenated oil and gas is 0~60℃, and the final boiling point is 280~350℃.

7. The method according to claim 1, characterized in that, In step (4), the initial boiling point of the naphtha fraction is 20~40℃, and the final boiling point is 140~160℃; The initial boiling point of the heavy aromatic fraction is 140~160℃, and the final boiling point is 210~250℃; The initial boiling point of the diesel fraction is 210~250℃, and the final boiling point is 280~350℃.

8. The method according to claim 1, characterized in that, In step (5), the conditions for catalytic conversion in the second reaction zone are: The heavy hourly space velocity of oil and gas is 4~20h. -1 ; The reaction time is 0.1~5s; and / or The weight ratio of the agent to oil is 6~26.

9. The method according to claim 8, characterized in that, In step (5), the conditions for catalytic conversion in the second reaction zone are: The heavy hourly space velocity of oil and gas is 8–16 h⁻¹. -1 ; The reaction time is 0.5~3s; and / or The weight ratio of the agent to oil is 10~22.

10. The method according to claim 1, characterized in that, In step (2), the pressure at the top of the first distillation column is 0.1~0.5MPa.

11. The method according to claim 1, characterized in that, In step (2), the pressure at the top of the first distillation column is 0.2~0.4MPa.

12. The method according to claim 1, characterized in that, In step (4), The top pressure of the second distillation column is 0.1~1.0 MPa; and / or The top temperature of the second distillation column is 50~120°C. o C.

13. The method according to claim 12, characterized in that, The top pressure of the second distillation column is 0.2~0.7 MPa; and / or The top temperature of the second distillation column is 60~100°C. o C.

14. The method according to claim 12, characterized in that, The naphtha fraction rich in light aromatics is extracted from the common rectification section of the second rectification column.

15. The method according to claim 1, characterized in that, The pre-separation zone of the distillation column has 20 to 35 trays; the common rectification section has 5 to 15 trays; the common stripping section has 3 to 8 trays; and / or the side-stream rectification section has 25 to 40 trays.

16. The method according to claim 15, characterized in that, 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; and / or The ratio of the gas mass flow rate from the common stripping section to the pre-separation zone and the side-stream rectification zone is 1 to 15.

17. The method according to claim 16, characterized in that, 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; and / or The ratio of the gas mass flow rate from the common stripping section to the pre-separation zone and the side-stream rectification zone is 2 to 10.

18. The method according to claim 1, characterized in that, In step (1), the catalyst is a catalytic cracking catalyst, which includes 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 a silica adhesive and / or an alumina adhesive; and / or The carrier is selected from one or more of the following: silica, kaolin, montmorillonite, diatomite, halloysite, soapstone, rettosite, sepiolite, attapulgite, hydrotalcite, and bentonite.

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

20. A system for producing light aromatics, comprising: A catalytic cracking unit includes: The reactor is provided with a first reaction zone and a second reaction zone, wherein the first reaction zone and the second reaction zone are connected in series and the second reaction zone is located upstream of the first reaction zone, and the catalyst contacts the feed oil in sequence through the second reaction zone and the first reaction zone. A gas-solid separator is connected to the oil-catalyst mixture outlet of the first reaction zone of the reactor, thereby separating the first reaction oil-gas from the catalyst in the first reaction zone. The first distillation column is provided with a first fraction oil and gas outlet, a second fraction oil outlet and an oil slurry outlet. The inlet of the first distillation column is connected to the outlet of the catalytic cracking unit through a pipeline. A diesel hydrogenation unit is provided with a diesel inlet, a hydrogen inlet, and a hydrogenation product outlet. The diesel inlet of the diesel hydrogenation unit is connected to the second distillate oil outlet of the first distillation column. The high-low separation device is provided with a hydrogenation product inlet, a hydrogen outlet and a hydrogenated oil and gas outlet. The hydrogenation product inlet is connected to the hydrogenation product outlet of the diesel hydrogenation unit. The high-low separation device separates the hydrogenated oil and gas from the hydrogenation product from the diesel hydrogenation unit. A degassing separation device is provided with an oil and gas inlet, a rich gas outlet and a first distillate oil outlet. The oil and gas inlet of the degassing separation device is connected to the first distillate oil and gas outlet of the first distillation column and the hydrogenated oil and gas outlet of the high and low separation unit, so that the first distillate oil and gas from the first distillation column and the hydrogenated oil and gas from the high and low separation unit are degassed and separated into rich gas and first distillate oil. The second distillation column is equipped with a first distillate oil inlet, a naphtha distillate outlet, a heavy aromatics distillate outlet, and a diesel distillate outlet. The first distillate oil inlet is connected to the first distillate oil outlet of the degassing separation unit. The heavy aromatics distillate outlet is connected to the second reaction zone of the reactor in the catalytic cracking unit. The diesel distillate outlet is connected to the first reaction zone of the reactor in the catalytic cracking unit. The second distillation column is a partitioned distillation column, which is provided with at least one partition wall. The partition wall divides the partitioned distillation column into four areas: a pre-separation zone, a common distillation section, a common stripping section, and a side-stream distillation zone. The oil and gas feed is located in the pre-separation zone. The pre-separation zone of the distillation column has 10 to 40 trays; the common rectification section has 3 to 20 trays; the common stripping section has 2 to 10 trays; and / or the side-stream rectification section has 10 to 45 trays.

21. The system according to claim 20, characterized in that, The reactor is selected from one or two of the following: constant diameter riser, constant linear velocity riser, variable diameter riser, variable linear velocity riser, fluidized bed, and composite reactor. The composite reactor is composed of a constant diameter or variable diameter riser and a fluidized bed. The first reaction zone and the second reaction zone are located on the same or different reactors.

22. The system according to claim 20, characterized in that, The first distillation column is a conventional distillation column with 20 to 40 trays. The second distillate oil is collected from the top 5 to 30 trays of the first distillation column.

23. The system according to claim 22, characterized in that, The first distillation column has 25 to 35 trays, and the second distillate oil is collected from the top 10 to 25 trays of the first distillation column.

24. The system according to claim 22, characterized in that, The first distillation column is heated by a vapor feed, and the bottom of the column is stripped with steam; and / or One or more intermediate-section heat recovery sections are provided on the side of the first distillation column.

25. The system according to any one of claims 20 to 24, characterized in that, The first distillation column and / or the second distillation column are equal-diameter distillation columns or variable-diameter distillation columns.

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