Method and system for combined treatment of catalytic cracking diesel and catalytic cracking diesel

文档序号：695702 发布日期：2021-05-04 浏览：46次中文

阅读说明：本技术 联合处理催化裂化柴油和催化裂解柴油的方法和系统 (Method and system for combined treatment of catalytic cracking diesel and catalytic cracking diesel ) 是由鞠雪艳习远兵孟勇新王哲丁石陈文斌张锐葛泮珠于 2019-10-30 设计创作，主要内容包括：本发明涉及柴油加工领域,具体涉及一种柴油的联合处理催化裂化柴油和催化裂解柴油的方法和系统。该方法包括：将催化裂化柴油和催化裂解柴油混合,并将得到的混合柴油原料在柴油分馏单元中进行分馏,得到轻柴油馏分和重柴油馏分；将轻柴油馏分引入至催化裂化单元中作为至少部分裂化原料油进行催化裂化；将重柴油馏分引入至加氢单元对其进行加氢处理,将重柴油馏分加氢产物引入至催化裂解单元中作为至少部分裂解原料油进行裂解。该系统包括催化裂化单元(1)、催化裂解单元(2)、柴油分馏单元(3)和加氢单元(4)。本发明提供的联合处理催化裂化柴油和催化裂解柴油的方法和系统,可有效提高了烯烃和芳烃产率,降低了氢耗和成本。(The invention relates to the field of diesel oil processing, in particular to a method and a system for jointly treating catalytic cracking diesel oil and catalytic cracking diesel oil by using diesel oil. The method comprises the following steps: mixing catalytic cracking diesel oil and catalytic cracking diesel oil, and fractionating the obtained mixed diesel oil raw material in a diesel oil fractionating unit to obtain a light diesel oil fraction and a heavy diesel oil fraction; introducing the light diesel oil fraction into a catalytic cracking unit to be used as at least part of cracked raw oil for catalytic cracking; introducing the heavy diesel oil fraction into a hydrogenation unit for carrying out hydrotreatment on the heavy diesel oil fraction, and introducing a heavy diesel oil fraction hydrogenation product into a catalytic cracking unit to be used as at least part of cracking raw oil for cracking. The system comprises a catalytic cracking unit (1), a catalytic cracking unit (2), a diesel oil fractionation unit (3) and a hydrogenation unit (4). The method and the system for jointly treating the catalytic cracking diesel oil and the catalytic cracking diesel oil can effectively improve the yield of olefin and aromatic hydrocarbon and reduce the hydrogen consumption and the cost.)

1. A method for combined treatment of catalytic cracking diesel and catalytic cracking diesel, the method comprising:

(1) introducing the cracked raw oil into a catalytic cracking unit for catalytic cracking to produce a cracked product, wherein the cracked product contains catalytic cracking diesel oil;

(2) introducing cracking raw oil into a catalytic cracking unit for catalytic cracking to produce a cracking product, wherein the cracking product contains catalytic cracking diesel oil;

(3) mixing the catalytic cracking diesel oil and the catalytic cracking diesel oil, and fractionating the obtained mixed diesel oil raw material in a diesel oil fractionating unit to obtain a light diesel oil fraction and a heavy diesel oil fraction;

(4) introducing the light diesel oil fraction into the catalytic cracking unit to be used as at least part of the cracked raw oil for catalytic cracking;

(5) introducing the heavy diesel oil fraction into a hydrogenation unit to carry out hydrotreating on the heavy diesel oil fraction to obtain a heavy diesel oil fraction hydrogenation product;

(6) introducing the heavy diesel oil fraction hydrogenation product into the catalytic cracking unit to be used as at least part of cracking raw oil for cracking.

2. The method of claim 1, wherein the hydrotreating comprises: and sequentially carrying out first hydrogenation treatment on the heavy diesel oil fraction in the presence of a first hydrogenation catalyst and carrying out second hydrogenation treatment in the presence of a second hydrogenation catalyst.

3. The process of claim 2, wherein the first hydrogenation catalyst comprises a support and a first active metal component supported on the support;

wherein the support is selected from at least one of alumina, silica, alumina-silica, titania, magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, silica-zirconia, titania-zirconia, silica-alumina-thoria, silica-alumina-titania, silica-alumina-magnesia and silica-alumina-zirconia;

the first active metal component is at least one metal element selected from VIB group and at least one metal element selected from VIII group; the VIB group metal element is preferably molybdenum and/or tungsten, and the VIII group metal element is preferably cobalt and/or nickel;

preferably, the content of at least one metal element selected from group VIB is 1-30 wt% and the content of at least one metal element selected from group VIII is 3-35 wt% based on the dry weight of the first hydrogenation catalyst and calculated by oxide;

preferably, the bulk density of the first hydrogenation catalyst is 0.4 to 1.3g/cm³The average particle diameter is 0.08-1.2mm, the specific surface area is 100-²/g。

4. The process according to claim 2 or 3, wherein the second hydrogenation catalyst contains an inorganic refractory component, a second active metal component and a carboxylic acid;

wherein the inorganic refractory component contains at least one of silica, magnesia, calcia, zirconia and titania and a portion of the second active metal component;

the second hydrogenation catalyst has a pore diameter of 2-40nm and a pore diameter of 100-300nm, wherein the pore volume of the pore diameter of 2-40nm accounts for 60-95% of the total pore volume, and the pore volume of 100-300nm accounts for 0.5-30% of the total pore volume;

preferably, the second active metal component is a group VIII metal element and a group VIB metal element;

wherein, in the second hydrogenation catalyst, the content of VIII group metal elements is 15-35 wt% and the content of VIB group metal elements is 35-75 wt% based on the dry weight of the second hydrogenation catalyst and calculated by oxides;

the group VIII metal element is preferably at least one selected from iron, cobalt, nickel, ruthenium, rhodium and palladium, and the group VIB metal element is preferably at least one selected from chromium, molybdenum and tungsten.

5. The method of claim 4, wherein the portion of the second active metal component is a portion of the group VIII metal elements in an amount of 60-90% of the total group VIII metal element content.

6. The process according to claim 4 or 5, wherein the second hydrogenation catalyst has a specific surface area of 70-200m²Per gram, pore volume of 0.15-0.6mL/g, average pore diameter of 5-25 nm;

preferably, in the second hydrogenation catalyst, the pore volume of 2-4nm is not more than 10% of the total pore volume.

7. A process according to any one of claims 4 to 6, wherein the inorganic refractory component is present in an amount of from 5 to 40 wt%, preferably from 10 to 30 wt%, based on the dry weight of the catalyst;

preferably, the weight ratio of the carboxylic acid to the inorganic refractory component on a dry basis is from 0.1 to 0.8: 1, preferably 0.2 to 0.6: 1;

preferably, the carboxylic acid is at least one selected from C1-18 monobasic saturated carboxylic acid, C7-10 phenyl acid, citric acid, adipic acid, malonic acid, succinic acid, maleic acid, tartaric acid and the like.

8. The process of claim 4 wherein the second hydrogenation catalyst further comprises phosphorus, based on the dry weight of the catalyst and P₂O₅The content of the phosphorus element is 0.8 to 10 wt%, preferably 1 to 8 wt%.

9. The method of any of claims 4-8, wherein the second hydrogenation catalyst is prepared by a method comprising:

(a) mixing a precursor containing at least one of silicon oxide, magnesium oxide, calcium oxide, zirconium oxide and titanium oxide with a part of a precursor of the second active metal component, and roasting to obtain an inorganic refractory component;

(b) mixing carboxylic acid and the precursors of the rest second active metal components to obtain impregnation liquid;

(c) and mixing the inorganic refractory component with the impregnation liquid, and molding and drying the obtained mixture to obtain the second hydrogenation catalyst.

10. The process of claim 9 wherein the impregnating solution obtained in step (b) further contains a phosphorus-containing material, said phosphorus-containing material being used in an amount such that P is present on a dry weight basis of the second hydrogenation catalyst₂O₅The content of the phosphorus element is 0.8-10 wt%, preferably 1-8 wt%;

preferably, the phosphorus-containing substance is at least one selected from the group consisting of phosphoric acid, hypophosphorous acid, ammonium phosphate and ammonium dihydrogen phosphate.

11. The method of claim 9, wherein in step (a), the firing conditions comprise: the roasting temperature is 300-900 ℃; the roasting time is 1-15 h; and/or

In step (c), the drying conditions include: the drying temperature is 50-250 ℃; the drying time is 2-10 h.

12. The method according to any one of claims 9 to 11, wherein the silica precursor is at least one of silica sol, silica and silica; the magnesium oxide precursor is at least one of magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium acetate and magnesium oxide; the precursor of the calcium oxide is at least one of calcium hydroxide, calcium carbonate, calcium oxalate, calcium nitrate, calcium acetate and calcium oxide; the zirconia precursor is at least one of zirconium hydroxide, zirconium carbonate, zirconium nitrate, zirconium acetate and zirconia; the precursor of the titanium oxide is at least one of titanium hydroxide, titanium nitrate, titanium acetate and zirconium oxide;

preferably, the average pore diameter of the precursors of the silicon oxide, the magnesium oxide, the calcium oxide, the zirconium oxide and the titanium oxide is not less than 10nm, the pore volume of the pore diameter of 2-6nm is not more than 15% of the total pore volume, and the pore volume of the pore diameter of 6-40nm is not less than 75% of the total pore volume.

13. The method as claimed in any one of claims 1 to 12, wherein the cut points of the light diesel fraction and the heavy diesel fraction obtained in step (3) are in the range of 220 ℃ and 240 ℃.

14. The process of any one of claims 1-12, wherein in step (5), the hydrotreating conditions comprise: the hydrogen partial pressure is 3-12MPa, the reaction temperature is 260-450 ℃, and the hydrogen-oil volume ratio is 400-1600Nm³/m³The liquid hourly space velocity is 0.3-4h^-1；

Preferably, the saturation rate of polycyclic aromatic hydrocarbon in the heavy diesel oil fraction hydrogenation product is not less than 85 wt%, the total aromatic hydrocarbon saturation rate is 12-80 wt%, and the distillation range of the heavy diesel oil fraction hydrogenation product is 200-400 ℃.

15. The method as claimed in any one of claims 1 to 12, wherein the boiling point ranges of the catalytically cracked diesel oil and the catalytically cracked diesel oil are 150 ℃ and 400 ℃ respectively, the content of total aromatic hydrocarbons is 60 to 90 wt% respectively, and the content of aromatic hydrocarbons with double rings and above is 40 to 80 wt% respectively;

preferably, the catalytic cracking diesel oil contains catalytic cracking light diesel oil and optional catalytic cracking heavy diesel oil;

preferably, in the step (3), the cetane number of the mixed diesel raw material is less than 25, and the distillation range is 170-400 ℃.

16. The process of any one of claims 1-15, wherein in step (1), the catalytic cracking conditions comprise: the temperature is 520 ℃ and 560 ℃, the mass ratio of the catalyst to the oil is 4-8, the oil gas retention time is 2-15s, the pressure is 0.1-0.3MPa, and the steam/cracked raw oil is 0-0.15;

preferably, the method further comprises fractionating the cracked product to obtain the catalytic cracking diesel.

17. The method of any one of claims 1-15, wherein in step (2), the conditions of the catalytic cracking comprise: the temperature is 580-600 ℃, the mass ratio of the oil to the solvent is 2-15, the oil gas retention time is 5-15s, the pressure is 0.1-0.3MPa, and the steam/cracked raw oil is 0-0.3;

preferably, the method further comprises fractionating the cracked product to obtain the catalytic pyrolysis diesel.

18. The method of any one of claims 1-17, wherein the method further comprises: in the step (6), before the heavy diesel oil fraction hydrogenation product is introduced into the catalytic cracking unit, heat exchange and gas-liquid separation are carried out on the heavy diesel oil fraction hydrogenation product, a liquid phase obtained by separation is introduced into the catalytic cracking unit, and a hydrogen-rich gas obtained by separation is circulated to the hydrogenation unit to serve as at least part of hydrogen of the hydrogenation unit;

preferably, before the hydrogen-rich gas is recycled to the hydrogenation unit, the method further comprises sequentially performing gas-liquid separation and compression on the hydrogen-rich gas to obtain recycle hydrogen, and recycling the recycle hydrogen to the hydrogenation unit.

19. A system for the combined treatment of catalytic cracking diesel and catalytic cracking diesel, the system comprising:

a catalytic cracking unit (1) for catalytically cracking the cracked feedstock oil to produce a cracked product, the cracked product containing catalytically cracked diesel;

the catalytic cracking unit (2) is used for carrying out catalytic cracking on the cracking raw oil to produce a cracking product, and the cracking product contains catalytic cracking diesel oil;

the diesel oil fractionating unit (3) is used for receiving the catalytic cracking diesel oil and fractionating the obtained mixed diesel oil to obtain a light diesel oil fraction and a heavy diesel oil fraction;

wherein the diesel oil fractionating unit (3) is communicated with the catalytic cracking unit (1) and is used for introducing the light diesel oil fraction into the catalytic cracking unit (1) as at least part of the cracked raw oil;

a hydrogenation unit (4) for receiving the heavy diesel oil fraction and hydrotreating it to obtain a heavy diesel oil fraction hydrogenation product;

the hydrogenation unit (4) is communicated with the catalytic cracking unit (2) and is used for introducing the heavy diesel oil fraction hydrogenation product into the catalytic cracking unit (2) to be used as at least part of cracking raw oil.

20. The system according to claim 19, wherein the hydrogenation unit (4) comprises a first hydrogenation zone (41) and a second hydrogenation zone (42) for subjecting the heavy diesel fraction to a first and a second hydrotreatment.

21. The system according to claim 19 or 20, wherein a cracking reaction unit and a cracked product fractionation unit are provided in the catalytic cracking unit (1); and/or

The catalytic cracking unit (2) is internally provided with a cracking reaction device and a cracking product fractionating device.

22. The system according to any one of claims 19 to 21, wherein the system further comprises a heat exchange unit (5) connected to the hydrogenation unit (4) for exchanging heat for the hydrogenation product of the heavy diesel fraction;

preferably, the system further comprises a first gas-liquid separation unit (6) which is respectively connected with the heat exchange unit (5) and the catalytic cracking unit (2) and is used for carrying out gas-liquid separation on the heavy diesel fraction hydrogenation product after heat exchange, introducing the obtained liquid phase into the catalytic cracking unit (1) to be used as at least part of the cracking raw oil, and introducing the obtained hydrogen-rich gas into the hydrogenation unit (4) to be used as at least part of hydrogen of the hydrogenation unit (4);

preferably, the system also comprises a second gas-liquid separation unit (7) connected with the first gas-liquid separation unit (6) and used for separating the hydrogen-rich gas into gas and liquid again;

preferably, the system also comprises a gas compression unit (8) for compressing the hydrogen-rich gas after gas-liquid separation again to obtain recycle hydrogen, and recycling the recycle hydrogen to the hydrogenation unit (4) as at least part of hydrogen of the hydrogenation unit (4).

Technical Field

The invention relates to the field of diesel oil processing, in particular to a method and a system for jointly treating catalytic cracking diesel oil and catalytic cracking diesel oil by using diesel oil.

Background

The proportion of catalytic cracking diesel oil in diesel oil products in China is high, and the catalytic cracking diesel oil accounts for 1/3 of a diesel oil pool. Its properties are high contents of S, N and arylhydrocarbon, low cetane number and poor stability. In recent years, with the wide application of high-severity catalytic cracking technologies such as isoparaffin-rich catalytic cracking technology (MIP), the aromatic hydrocarbon content, especially the polycyclic aromatic hydrocarbon content, in MIP catalytic diesel oil is further increased, and the cetane number is further reduced. With the increasing awareness of environmental protection, the national requirements for the clean quality of common diesel oil are continuously upgraded, the market demand of the diesel oil is obviously reduced, and the problem of surplus diesel oil is obvious. Therefore, it is necessary to process poor diesel into high value added products.

Meanwhile, gaps for gasoline, aromatic hydrocarbon and propylene in the current market are still large. One of the main units for producing gasoline and aromatic hydrocarbons in oil refining and chemical enterprises is a catalytic cracking unit, such as an FCC unit; one of the main plants for producing propylene is a catalytic cracking unit. The main raw materials of the catalytic cracking device comprise naphtha, diesel oil, wax oil and residual oil, wherein the yield of propylene in the catalytic cracking unit can reach 20 percent or even more than 30 percent after the residual oil raw material is subjected to hydrotreating. However, catalytic crackers that use diesel as the feedstock have a low propylene yield. Therefore, by selecting a proper process route, the yield of propylene produced by catalytic cracking of diesel oil and the production of light aromatic hydrocarbon are improved greatly.

No matter the catalytic cracking light diesel oil (LCO) hydrogenation-catalytic cracking combination is used for producing high-octane gasoline components or aromatic hydrocarbons, or the LCO hydrogenation-catalytic cracking combination is used for producing low-carbon olefins, the LCO must be firstly hydrofined and then used as a feed for catalytic cracking or catalytic cracking. Most of aromatic hydrocarbons in LCO are bicyclic and above bicyclic aromatic hydrocarbons (polycyclic aromatic hydrocarbons for short), and the aim of LCO hydrofining is to hydrogenate the polycyclic aromatic hydrocarbons in LCO. The catalytic cracking device needs to retain monocyclic aromatic hydrocarbons as much as possible, and the catalytic cracking device can properly improve the hydrogenation depth of the LCO, so that the LCO is difficult to be economically and effectively hydrogenated and produced by a single set of hydrogenation for refineries which simultaneously have catalytic cracking and catalytic cracking devices or need to flexibly adjust the catalytic cracking and catalytic cracking production.

CN 1422327 discloses a combined hydrogenation-catalytic cracking process for producing more propylene from LCO. The method comprises the steps of enabling catalytic cracking raw materials to pass through a first set of catalytic cracking device, and separating obtained products to obtain gas, naphtha, diesel oil and heavy components. And the cycle oil is subjected to hydrotreating and then enters a second set of catalytic cracking unit as a raw material, so that the yield of propylene is improved. The patent application requires that the decalin content in the hydrogenated cycle oil is maximized, and the total aromatic hydrocarbon content is less than 5 weight percent, and the ring-opening cracking reaction is easy to occur in the catalytic cracking process to produce propylene. This patent application relates to two sets of catalytic devices and does not make full use of the circulating oil, lacking economy.

CN101063047A discloses a heavy raw material hydrotreating-catalytic cracking method for increasing propylene yield, in which heavy distillate oil and optional light cycle oil from a catalytic cracking unit can be jointly reacted in one reaction zone, or can be reacted in two hydrogenation reaction zones filled with different hydrogenation catalysts, respectively, after cooling, separating and fractionating the reaction effluent, the obtained heavy liquid phase fraction is sent to a catalytic cracking unit, and the catalytic cracking reaction product is separated by a separator to obtain the final product. Although the method provided by the patent application improves the properties of the wax oil raw material of the catalytic cracking unit through a hydrotreating method, the hydrogen consumption is increased in the hydrogenation process.

Disclosure of Invention

The invention aims to overcome the defects of low yield of olefin and aromatic hydrocarbon, high hydrogen consumption and high cost in the diesel oil processing process in the prior art, and provides a method and a system for combined treatment of catalytic cracking diesel oil and catalytic cracking diesel oil, so that the yield of olefin and aromatic hydrocarbon is effectively improved, and the hydrogen consumption and the cost are reduced.

In order to achieve the above object, the present invention provides, in one aspect, a method for combined treatment of catalytic cracking diesel and catalytic cracking diesel, the method comprising:

(1) introducing the cracked raw oil into a catalytic cracking unit for catalytic cracking to produce a cracked product, wherein the cracked product contains catalytic cracking diesel oil;

(2) introducing cracking raw oil into a catalytic cracking unit for catalytic cracking to produce a cracking product, wherein the cracking product contains catalytic cracking diesel oil;

(4) introducing the light diesel oil fraction into the catalytic cracking unit to be used as at least part of the cracked raw oil for catalytic cracking;

(5) introducing the heavy diesel oil fraction into a hydrogenation unit to carry out hydrotreating on the heavy diesel oil fraction to obtain a heavy diesel oil fraction hydrogenation product;

(6) introducing the heavy diesel oil fraction hydrogenation product into the catalytic cracking unit to be used as at least part of cracking raw oil for cracking.

Preferably, the hydrotreating comprises: sequentially carrying out first hydrogenation treatment on the heavy diesel oil fraction in the presence of a first hydrogenation catalyst and carrying out second hydrogenation treatment in the presence of a second hydrogenation catalyst; the second hydrogenation catalyst contains an inorganic refractory component, a second active metal component and a carboxylic acid; wherein the inorganic refractory component contains at least one of silica, magnesia, calcia, zirconia and titania and a portion of the second active metal component; the second hydrogenation catalyst has a pore diameter of 2-40nm and a pore diameter of 100-300nm, wherein the pore volume of the pore diameter of 2-40nm accounts for 60-95% of the total pore volume, and the pore volume of 100-300nm accounts for 0.5-30% of the total pore volume.

Preferably, the part of the second active metal component is part of the VIII group metal elements, and the content of the part of the VIII group metal elements is 60-90% of the total content of the VIII group metal elements.

Preferably, the second hydrogenation catalyst further comprises phosphorus, based on the dry weight of the catalyst and based on P₂O₅The content of the phosphorus element is 0.8 to 10 wt%, preferably 1 to 8 wt%.

In a second aspect, the present invention provides a system for the combined treatment of catalytic cracking diesel and catalytic cracking diesel, the system comprising:

the catalytic cracking unit is used for carrying out catalytic cracking on the cracked raw oil to produce a cracked product, and the cracked product contains catalytic cracking diesel oil;

the catalytic cracking unit is used for carrying out catalytic cracking on the cracking raw oil to produce a cracking product, and the cracking product contains catalytic cracking diesel oil;

the diesel oil fractionating unit is used for receiving the catalytic cracking diesel oil and fractionating the obtained mixed diesel oil to obtain a light diesel oil fraction and a heavy diesel oil fraction;

the diesel oil fractionating unit is communicated with the catalytic cracking unit and is used for introducing the light diesel oil fraction into the catalytic cracking unit to be used as at least part of the cracked raw oil;

the hydrogenation unit is used for receiving the heavy diesel oil fraction and carrying out hydrogenation treatment on the heavy diesel oil fraction to obtain a heavy diesel oil fraction hydrogenation product;

the hydrogenation unit is communicated with the catalytic cracking unit and is used for introducing the heavy diesel oil fraction hydrogenation product into the catalytic cracking unit to be used as at least part of cracking raw oil.

The invention has the following advantages:

1. according to the invention, the diesel oil product is cut and fractionated to form the light diesel oil fraction and the heavy diesel oil fraction, on one hand, the light diesel oil fraction can provide a high aromatic hydrocarbon content raw material capable of producing high-octane gasoline for catalytic cracking, on the other hand, the light diesel oil fraction can be directly used as a catalytic cracking raw material without hydrogenation, so that the hydrogen consumption of the whole processing system is reduced, on the other hand, only the heavy diesel oil fraction is subjected to hydrotreating, and then the hydrogenation product is subjected to catalytic cracking, so that the olefin yield can be improved.

2. Aiming at catalytic cracking and catalytic cracking, the invention can carry out high-efficiency and high-economical combined production by a set of hydrofining device.

3. In a preferable situation, the invention adopts a special second hydrogenation catalyst which has higher content of hydrogenation active components, so that the aromatic saturation capacity of the hydrogenation product of the heavy diesel oil fraction is obviously improved, and the hydrogenation catalyst has higher denitrification and desulfurization capacity for oil products with high nitrogen and high sulfur content.

4. According to the invention, through reasonable grading of the conventional first hydrogenation catalyst and the special second hydrogenation catalyst, the operation period can be prolonged on one hand, the aromatic hydrocarbon hydrogenation activity of the whole catalyst system can be improved on the other hand, and the higher low-carbon olefin yield is realized in the catalytic cracking.

Drawings

FIG. 1 is a system for combined processing of catalytic cracking diesel and catalytic cracking diesel according to an embodiment of the present invention;

FIG. 2 is a system for combined processing of catalytically cracked diesel fuel and catalytically cracked diesel fuel, as one specific reference.

Description of the reference numerals

1 catalytic cracking unit 2 catalytic cracking unit 3 diesel oil fractionating unit

4 hydrogenation unit 5 heat exchange unit 6 first gas-liquid separation unit

7 second gas-liquid separation unit 8 gas compression unit

41 first hydrogenation zone 42 second hydrogenation zone

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a process for the combined treatment of catalytically cracked diesel fuel and catalytically cracked diesel fuel, which process comprises:

(1) introducing the cracked raw oil into a catalytic cracking unit for catalytic cracking to produce a cracked product, wherein the cracked product contains catalytic cracking diesel oil;

(2) introducing cracking raw oil into a catalytic cracking unit for catalytic cracking to produce a cracking product, wherein the cracking product contains catalytic cracking diesel oil;

(4) introducing the light diesel oil fraction into the catalytic cracking unit to be used as at least part of the cracked raw oil for catalytic cracking;

(5) introducing the heavy diesel oil fraction into a hydrogenation unit to carry out hydrotreating on the heavy diesel oil fraction to obtain a heavy diesel oil fraction hydrogenation product;

(6) introducing the heavy diesel oil fraction hydrogenation product into the catalytic cracking unit to be used as at least part of cracking raw oil for cracking.

According to the present invention, although the heavy diesel fraction is subjected to conventional hydrotreating to achieve the object of the present invention, that is, to improve the yields of olefins and aromatics and reduce the hydrogen consumption and cost, the inventors of the present invention further found in the research that by sequentially subjecting the heavy diesel fraction to a first hydrotreating in the presence of a first hydrogenation catalyst and a second hydrotreating in the presence of a second hydrogenation catalyst, through a reasonable grading of the first hydrogenation catalyst and the second hydrogenation catalyst, on the one hand, the operation cycle can be prolonged, and on the other hand, the aromatics hydrogenation activity of the entire catalyst system can be further improved, which leads to a higher yield of lower olefins in catalytic cracking.

Preferably, the first hydrogenation catalyst and the second hydrogenation catalyst are different.

According to the present invention, the first hydrogenation catalyst may be a hydrogenation catalyst conventional in the art, and for example, it may include a support and a first active metal component supported on the support. Among them, the carrier may be one conventionally used in the art, and may be, for example, but not limited to, alumina, silica, alumina-silica, titania, magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, silica-zirconia, titania-zirconia, silica-alumina-thoria, silica-alumina-titania, silica-alumina-magnesia and silica-alumina-zirconia. The first active metal component may be an active metal component conventionally used in the art as a hydrogenation catalyst, for example, the first active metal component is at least one metal element selected from group VIB and at least one metal element selected from group VIII.

According to a preferred embodiment of the invention, the group VIB metal element is molybdenum and/or tungsten, and the group VIII metal element is preferably cobalt and/or nickel.

According to a preferred first hydrogenation catalyst of the present invention, the support is alumina and the first active metal component is nickel and tungsten.

According to the invention, the contents of group VIB and group VIII metal elements in the first hydrogenation catalyst can vary within wide limits, preferably, the content of at least one group VIB metal element is from 1 to 30% by weight, preferably from 20 to 30% by weight, and the content of at least one group VIII metal element is from 3 to 35% by weight, preferably from 3 to 10% by weight, based on the dry weight of the first hydrogenation catalyst and calculated as oxides.

According to the present invention, the shape of the first hydrogenation catalyst is not particularly limited, and may be a shape of a hydrogenation catalyst that is conventional in the art, for example, a strip shape, a spherical shape, or another shape.

According to the present invention, it is preferred that the first hydrogenation catalyst has a bulk density of 0.4 to 1.3g/cm³。

According to the invention, the bulk density of the catalyst is determined by a catalyst bulk density analysis method (Q/SH 3360245-2014), specifically, the bulk density is determined by a method of measuring the tight bulk density with the sample diameter less than or equal to 3 mm:

the oscillator is turned on and the oscillation frequency is set to a set position. Putting a 500ml measuring cylinder in the middle of an oscillator, ensuring that the measuring cylinder does not topple over, pouring the catalyst into the 500ml measuring cylinder at a constant speed within 20-30 s while oscillating, stopping adding the catalyst when the volume approaches 500ml, continuing oscillating for 1min, closing the oscillator, weighing the weight of the catalyst in the measuring cylinder, recording the weight as W1(g), and accurately reading the volume V1 of the catalyst. The close bulk density of the catalyst is then:

the measurement was carried out three times in the same manner, and the average of the three times was the bulk density of the catalyst.

According to the present invention, it is preferred that the first hydrogenation catalyst has an average particle diameter of 0.08 to 1.2 mm.

According to the present invention, it is preferred that the specific surface area of the first hydrogenation catalyst is 100-300m²(ii) in terms of/g. Wherein, the specific surface area is determined by a low-temperature nitrogen adsorption method (meeting GB/T5816-1995 standard).

According to the present invention, the first hydrogenation catalyst may be prepared according to the methods of hydrogenation catalysts conventional in the art, for example, a method of impregnation, and specifically, may include: squeezing and mixing an alumina precursor (such as pseudo-boehmite) with a peptizing agent and an auxiliary agent, (2) forming the obtained mixture, and (3) roasting the formed alumina precursor to prepare an alumina carrier; (4) preparing an impregnation solution containing a metal component; (5) uniformly dipping the calcined alumina carrier into the dipping solution to prepare a catalyst precursor; (6) and drying or roasting the catalyst precursor to obtain the first hydrogenation catalyst.

Although the second hydrogenation catalyst can be a hydrogenation catalyst different from the first hydrogenation catalyst, which is conventional in the art, the effect of the present invention can be further improved, but the inventors of the present invention found that by adopting a special second hydrogenation catalyst, the second hydrogenation catalyst has a higher content of hydrogenation active components, so that the aromatic saturation capacity of the hydrogenation product of the heavy diesel fraction is obviously improved, and the second hydrogenation catalyst has better adaptability to high-nitrogen and high-sulfur distillate oil.

The special second hydrogenation catalyst contains an inorganic refractory component, a second active metal component and a carboxylic acid;

wherein the inorganic refractory component contains at least one of silica, magnesia, calcia, zirconia and titania and a portion of the second active metal component;

The silicon oxide, magnesium oxide, calcium oxide, zirconium oxide and titanium oxide contained in the inorganic refractory component in the second hydrogenation catalyst are basically inert substances and are difficult to combine with the VIII element to form a compound with a stable structure, so that the utilization rate of the VIII element is improved. In addition, the inorganic refractory components have weak acting force with other active components of the catalyst, so that the growth of an active phase of the catalyst can be promoted, and the performance of the catalyst is further promoted.

Preferably, the pore volume of pores with a pore diameter of 2-40nm accounts for 75-90% of the total pore volume, and the pore volume of pores with a pore diameter of 100-300nm accounts for 5-15% of the total pore volume. Wherein the pore volume of pores with a diameter of 2-4nm is not more than 10% of the total pore volume.

According to the invention, the specific surface area of the catalyst and the pore distribution, the pore diameter and the pore volume of the catalyst between 2 and 40nm are measured by a low-temperature nitrogen adsorption method (meeting the GB/T5816-1995 standard), and the pore distribution, the pore diameter and the pore volume of the catalyst between 100 and 300nm are measured by a mercury intrusion method. The pore volume of the catalyst with the pore diameter less than 100nm is measured by a low-temperature nitrogen adsorption method, the pore volume of the catalyst with the pore diameter more than 100nm is measured by a mercury intrusion method, and the pore volume of the catalyst is the sum of the pore volume of the catalyst and the pore volume of the catalyst. The average pore diameter was calculated according to the cylindrical pore model (average pore diameter ═ total pore volume × 4000/specific surface area).

Preferably, the specific surface area of the second hydrogenation catalyst is 70 to 200m²A/g, preferably from 90 to 180m²Pore volume of 0.15 to 0.6mL/g, preferably 0.2 to 0.4mL/g, and average pore diameter of 5 to 25nm, preferably 8 to 15 nm. Wherein, the specific surface area, the pore volume and the average pore diameter are measured after the catalyst is calcined at 400 ℃ for 3 hours.

According to the invention, the pore diameter of 2-40nm means a pore diameter of 2nm or more and less than 40nm, and the pore diameter of 100-300nm means a pore diameter of 100nm or more and less than 300nm, unless otherwise stated. The average pore diameter of 5 to 25nm means that the average of the pore diameters of all the pores of the second hydrogenation catalyst is not less than 5nm and not more than 25 nm. The pore diameter of 2-4nm is larger than or equal to 2nm and smaller than 4 nm.

According to the present invention, the second metal active component may be a component of an existing active component that can be used in the second hydrogenation catalyst, for example, the second metal active component may be a group VIII metal element and a group VIB metal element. Wherein the content of the second metal active component can also be changed in a wide range, preferably, the content of the VIII group metal element in the second hydrogenation catalyst is 15-35 wt%, preferably 20-30 wt% based on the dry weight of the second hydrogenation catalyst and calculated by oxide; the content of group VIB metal elements is from 35 to 75% by weight, preferably from 40 to 65% by weight.

According to a preferred embodiment of the present invention, the group VIII metal element is selected from at least one of iron, cobalt, nickel, ruthenium, rhodium and palladium, and the group VIB metal element is selected from at least one of chromium, molybdenum and tungsten.

The inventors of the present invention found in their studies that, preferably, by including a part of the group VIII metal element in the inorganic refractory component, the content of the active component in the second hydrogenation catalyst can be further increased, thereby further improving the hydrofinishing performance of the second hydrogenation catalyst. While the amount ratio of the group VIII metal element contained in the inorganic refractory component is not particularly limited and may be selected from a wide range, it is preferable that the content of the partial group VIII metal element is 60 to 90% of the total content of the group VIII metal elements.

According to the present invention, it is preferred that the inorganic refractory component is present in an amount of 5 to 40 wt%, more preferably 10 to 30 wt%, based on the dry weight of the second hydrogenation catalyst.

Here, the dry weight of the inorganic refractory powder is a weight determined by calcining the sample at 600 ℃ for 4 hours, and the dry weight of the second hydrogenation catalyst is a weight determined by calcining the sample at 400 ℃ for 3 hours. The dry basis weights appearing hereinafter are equally applicable to this definition. That is, in the absence of a contrary indication, the dry weight of the inorganic refractory powder as described herein is the weight determined by calcining the sample at 600 ℃ for 4 hours and the dry weight of the second hydrogenation catalyst is determined by calcining the sample at 400 ℃ for 3 hours. It will be appreciated by those skilled in the art that the organic acid contained in the second hydrogenation catalyst will decompose and volatilize at elevated temperatures when calculated on a dry weight basis, and therefore the organic acid content is not calculated on a dry weight basis.

The inventors of the present invention found in their studies that the introduction of a carboxylic acid compound into the second hydrogenation catalyst can protect the active component of the second hydrogenation catalyst and improve the activity of the catalyst. Therefore, the carboxylic acid is introduced into the second hydrogenation catalyst to protect the active component of the second hydrogenation catalyst and to improve the activity of the second hydrogenation catalyst, and the amount of the carboxylic acid added is not particularly limited. According to a preferred embodiment of the invention, the weight ratio, on a dry basis, of the carboxylic acid to the inorganic refractory component is between 0.1 and 0.8: 1, preferably 0.2 to 0.6: 1.

preferably, the carboxylic acid is selected from at least one of C1-18 monobasic saturated carboxylic acids (e.g., C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18 monobasic saturated carboxylic acids) (e.g., but not limited to, formic acid, acetic acid, propionic acid, octanoic acid, valeric acid, hexanoic acid, decanoic acid, pentanoic acid), C7-10 phenyl acids (e.g., C7, C8, C9, C10 phenyl acids) (e.g., but not limited to, benzoic acid, phenylacetic acid, phthalic acid, terephthalic acid), citric acid, adipic acid, malonic acid, succinic acid, maleic acid, tartaric acid, and the like.

According to a preferred embodiment of the present invention, in order to further improve the performance of the second hydrogenation catalyst, the second hydrogenation catalyst further comprises a phosphorus element, preferably P₂O₅Exist in the form of (1). Preferably, based on the dry weight of the second hydrogenation catalyst and P₂O₅The content of the phosphorus element is 0.8 to 10% by weight, more preferably 1 to 8% by weight.

According to the present invention, preferably, the second hydrogenation catalyst is a shaped catalyst, and the shape of the second hydrogenation catalyst is preferably a cylinder, a clover or a honeycomb.

According to a preferred embodiment of the present invention, the second hydrogenation catalyst is prepared by a method comprising:

(a) mixing a precursor containing at least one of silicon oxide, magnesium oxide, calcium oxide, zirconium oxide and titanium oxide with a part of the precursor added with the second metal active component, and roasting to obtain an inorganic refractory component;

(b) mixing carboxylic acid and the rest of the precursor added with the second metal active component to obtain impregnation liquid;

(c) and mixing the inorganic refractory component with the impregnation liquid, and molding and drying the obtained mixture to obtain the second hydrogenation catalyst.

The catalyst prepared by the conventional impregnation method has low metal loading, the content of the VIII group metal is usually less than 10%, and the content of the VIB group metal is usually less than 35%. This limits the number of active metal sites in the catalyst and the activity of the catalyst does not reach higher levels. The catalyst prepared by the kneading method can improve the loading of active metal in the catalyst, but the hydrofining activity of the catalyst is not high, and the utilization rate of the active metal is low. The current catalyst preparation generally does not employ this method. In the present invention, a portion of the hydrodesulfurization catalytically active component, and more preferably a portion of the group VIII metal, is mixed into a support precursor and calcined to form the inorganic refractory powder. And then mixing the impregnation liquid containing the residual active metal with the inorganic refractory powder, thereby improving the content of active components in the catalyst and further improving the hydrofining performance of the catalyst.

According to the invention, the precursors added with the second metal active component are preferably precursors of VIII group metal elements and VIB group metal elements; the precursors of the VIII group metal elements and the VIB group metal elements are used in such amounts that the contents of the VIII group metal elements and the VIB group metal elements are respectively the contents described above based on the dry weight of the catalyst and calculated by oxides, and the selection of the specific elements is also performed as described above.

According to the invention, in the precursor added with the second metal active component, the precursor of the iron element may include, but is not limited to, one or more of iron nitrate, iron oxide, iron carbonate hydroxide, and iron acetate, the precursor of the cobalt element may include, but is not limited to, one or more of cobalt nitrate, cobalt carbonate hydroxide, cobalt acetate, and cobalt oxide, the precursor of the nickel element may include, but is not limited to, one or more of nickel nitrate, nickel carbonate hydroxide, nickel acetate, and nickel oxide, the precursor of the ruthenium element may include, but is not limited to, one or more of ruthenium nitrate, ruthenium acetate, ruthenium oxide, and ruthenium hydroxide, the precursor of the rhodium element may include, but is not limited to, one or more of rhodium nitrate, rhodium hydroxide, and rhodium oxide, and the precursor of the palladium element may include, but is not limited to, one or more of palladium nitrate, palladium oxide, and palladium hydroxide, the precursors of the chromium element can include but are not limited to one or more of chromium nitrate, chromium oxide, chromium hydroxide and chromium acetate, the precursors of the molybdenum element can include but is not limited to one or more of ammonium heptamolybdate, ammonium molybdate, ammonium phosphomolybdate and molybdenum oxide, and the precursors of the tungsten element can include but is not limited to one or more of ammonium metatungstate, ammonium ethylmetatungstate and tungsten oxide.

The inventor of the present invention found in research that, preferably, by preparing a part of the precursor of the group VIII metal element into the inorganic refractory component and preparing the rest of the precursor of the group VIII metal element and the precursor of the group VIB metal element together into an impregnation solution to impregnate the inorganic refractory component, the content of the active component in the second hydrogenation catalyst can be further increased, thereby further improving the hydrorefining performance of the second hydrogenation catalyst. While the amount ratio of the precursor of the group VIII metal element used for preparing the inorganic refractory component is not particularly limited and may be selected from a wide range, it is preferable that the amount of the partial precursor of the group VIII metal element in step (a) is 60 to 90% of the total amount of the precursor of the group VIII metal element.

According to the present invention, in step (a), the precursor of silica, magnesia, calcia, zirconia, titania may be any of various materials that can provide silica, magnesia, calcia, zirconia, titania under the condition of calcination, for example, the silica precursor may be silica sol, silica, etc.; the magnesium oxide precursor is magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium acetate, magnesium oxide and the like; the precursor of the calcium oxide is calcium hydroxide, calcium carbonate, calcium oxalate, calcium nitrate, calcium acetate, calcium oxide and the like; the zirconia precursor is zirconium hydroxide, zirconium carbonate, zirconium nitrate, zirconium acetate, zirconia and the like; the precursor of the titanium oxide is titanium hydroxide, titanium nitrate, titanium acetate, zirconium oxide and the like.

In step (c), the inorganic refractory component is used in an amount such that the inorganic refractory component is present in the second hydrogenation catalyst in an amount of from 5 to 40 wt%, preferably from 10 to 30 wt%, based on the dry weight of the second hydrogenation catalyst.

In step (b), the amount and selection of the carboxylic acid are described in detail above, and are not repeated here.

According to the invention, the carboxylic acid substances are introduced into the impregnation liquid, so that the second metal active component can be effectively protected, and the forming of the second hydrogenation catalyst can be promoted, thereby effectively improving the performance of the catalyst.

In order to further improve the performance of the finally prepared second hydrogenation catalyst, the average pore diameters of the silicon oxide, the magnesium oxide, the calcium oxide, the zirconium oxide and the titanium oxide precursors are not less than 10nm, the pore volume with the pore diameter of 2-6nm accounts for no more than 15% of the total pore volume, and the pore volume with the pore diameter of 6-40nm accounts for no less than 75% of the total pore volume.

According to the invention, in order to further improve the solubility of the precursor of the second metal active component added in the prepared impregnation solution and improve the performance of the finally prepared second hydrogenation catalyst, a phosphorus-containing substance is preferably added in the preparation process of the impregnation solution, and the phosphorus-containing substance is preferably a phosphorus-containing inorganic acid and is further preferably at least one of phosphoric acid, hypophosphorous acid, ammonium phosphate and ammonium dihydrogen phosphate. Further preferably, the phosphorus-containing material is used in an amount such that the second hydrogenation catalyst is finally prepared on a dry weight basis and in terms of P₂O₅The content of the phosphorus element is 0.8 to 10% by weight, preferably 1 to 8% by weight, more preferably 2 to 8% by weight.

According to a preferred embodiment of the invention, in the preparation of the impregnation solution, the organic carboxylic acid compound and the precursors containing the group VIB metal element and the group VIII metal element are added to the aqueous solution of the phosphorus-containing substance, and then stirred at 40-100 ℃ for 1-8h until all the organic carboxylic acid compound and the precursors are dissolved. The order of addition of the organic carboxylic acid compound, the phosphorus-containing substance, and the metal element precursor may be interchanged.

According to the invention, in the step (a), the roasting conditions can be selected within a wide range, and preferably, the roasting temperature is 300-900 ℃, preferably 400-700 ℃; the roasting time is 1-15h, preferably 3-8 h.

According to the present invention, in step (c), the drying conditions can be selected within a wide range, preferably, the drying temperature is 50-250 ℃, preferably 100-200 ℃; the drying time is 2-10h, preferably 3-8 h.

According to the invention, the forming mode can be various existing forming methods, such as extrusion molding and rolling ball molding. The extrusion molding can be performed according to the prior art, and the inorganic refractory component to be extruded and molded and the impregnation solution containing the metal component are uniformly mixed and then extruded into a required shape, such as a cylinder, a clover shape, a honeycomb shape and the like.

In addition, the catalyst pore channel structures of the second hydrogenation catalyst provided by the invention are respectively concentrated between 2-40nm and 100-300 nm. In the poor-quality distillate oil, the size of reactant molecules is larger, so that a larger reaction space is inevitably needed, and the pore passages with the size of 100-300nm in the catalyst can provide a larger place for the diffusion of the reactants, so that the accessibility of the reactants and an active center is promoted, and the performance of the second hydrogenation catalyst is improved.

According to the invention, in the step (1), the catalytic cracking conditions can be conventional in the field, preferably, the temperature is 520-.

Wherein the catalytic cracking further comprises being carried out in the presence of a catalyst, which may be a catalyst conventionally used in the art for catalytic cracking, preferably MLC-500.

Wherein, the catalytic cracking is carried out in the presence of a aging agent, which can be the aging agent used for catalytic cracking in the prior art, and is preferably MAT-66.

According to the present invention, the products obtained by catalytic cracking generally include gasoline products, diesel products, liquefied gas products and slurry oil products, and therefore, preferably, the method further comprises fractionating the products obtained by catalytic cracking to obtain target products, such as gasoline (for example, the distillation range can be within 65-180 ℃) and aromatic hydrocarbons, and obtain catalytic cracking diesel.

Wherein, the condition of the fractional distillation is preferably that the distillation range of the obtained catalytic cracking diesel oil is within 170-450 ℃, the boiling point range is 150-400 ℃, the content of the total aromatic hydrocarbon is 60-90 wt%, and the content of the aromatic hydrocarbon with double rings and above double rings is 40-80 wt%.

Preferably, the density of the catalytic cracking diesel oil at 20 ℃ is 0.900-0.950g/cm³。

Preferably, the sulfur content of the catalytic cracking diesel oil is 3000-8000 mu g/g.

Preferably, the nitrogen content of the catalytic cracking diesel oil is 300-1500 mu g/g

Preferably, the content of monocyclic aromatic hydrocarbon in the catalytic cracking diesel oil is 12.0-30.0 wt%.

Preferably, the cetane number of the catalytic cracking diesel oil is less than 25.

Although the resulting catalytically cracked diesel fuel may be used for the purposes of the present invention in accordance with the present invention, it is preferred that the catalytically cracked diesel fuel feedstock comprises catalytically cracked light diesel fuel (LCO), with or without catalytically cracked heavy diesel fuel (HCO).

According to the present invention, the catalytically cracked feedstock oil, as described above, comprises a portion of the light diesel fraction recycled back in the present invention, and also comprises a feedstock conventionally used in the art for catalytic cracking, for example, may be, but is not limited to, coker gas oil, atmospheric residue, vacuum distillate, vacuum residue, and the like.

According to the invention, in the step (2), the catalytic cracking conditions can be the conventional catalytic cracking conditions in the field, preferably, the temperature is 580-600 ℃, the catalyst-oil mass ratio is 2-15, the oil-gas retention time is 5-15s, the pressure is 0.1-0.3MPa, and the steam/cracking raw oil is 0-0.3.

Wherein the catalytic cracking further comprises being carried out in the presence of a catalyst, which may be a catalyst conventionally used in the art for catalytic cracking, preferably MMC-2.

According to the present invention, the products obtained by catalytic cracking generally comprise a lower olefin product, a light naphtha product, a heavy naphtha product, catalytic cracking diesel oil and a slurry oil product, and therefore, preferably, the method further comprises fractionating the products obtained by catalytic cracking to obtain target products, such as a lower olefin product, a light naphtha product (for example, the distillation range can be within 65-135 ℃), a heavy naphtha product (for example, the distillation range can be within 130-175 ℃), and catalytic cracking diesel oil.

Wherein, the condition of the fractional distillation is preferably that the distillation range of the obtained catalytic cracking diesel is within 175-450 ℃, the boiling point range is 150-400 ℃, and the content of the total aromatic hydrocarbon is 60-90 wt%, wherein the content of the aromatic hydrocarbon of double rings and above double rings is 40-80 wt%.

Preferably, the density of the catalytic pyrolysis diesel oil at 20 ℃ is 0.920-0.970g/cm³。

Preferably, the sulfur content of the catalytic cracking diesel oil is 4000-10000 mu g/g.

Preferably, the nitrogen content of the catalytic cracking diesel is 500-2000 mu g/g.

Preferably, the content of the monocyclic aromatic hydrocarbon in the catalytic cracking diesel oil is 15-35 wt%.

Preferably, the cetane number of the catalytic pyrolysis diesel is less than 25, preferably less than 19.

According to the present invention, the catalytic cracking raw oil, as mentioned above, includes a part of the hydrogenation product of the heavy diesel oil fraction recycled back in the present invention, and also includes conventional raw materials for catalytic cracking, for example, but not limited to, atmospheric heavy oil, atmospheric wax oil, vacuum wax oil, residual oil fraction, etc.

According to the present invention, in the step (3), the amounts of the catalytic cracking diesel oil and the catalytic cracking diesel oil used for mixing are not particularly limited, but in order to further increase the yield of olefins and aromatics in the cracking unit and reduce the hydrogen consumption in the hydrogenation unit, it is preferable that the mixing ratio of the catalytic cracking diesel oil and the catalytic cracking diesel oil is such that the cetane number of the obtained mixed diesel oil raw material is less than 25 and the distillation range is 170-400 ℃.

The conditions for fractionating the mixed diesel oil raw material can refer to the conventional fractionation conditions in the field, and preferably, the cut point of the light diesel oil fraction and the heavy diesel oil fraction obtained after fractionation is in the range of 220-240 ℃, wherein the light diesel oil fraction obtained by fractionation can directly return to a catalytic cracking unit for catalytic cracking without hydrogenation, so that more gasoline and aromatic hydrocarbon are generated while hydrogen consumption is reduced. Thus, within this preferred range, the hydrogen consumption of the hydrogenation unit can be further reduced, as well as the gasoline and aromatics yields increased.

According to the invention, the aromatics in the heavy diesel fraction obtained by fractionation mainly comprise monocyclic aromatics, bicyclic aromatics and tricyclic aromatics, wherein the bicyclic aromatics and tricyclic aromatics account for a major portion of the total aromatic content. Hydrodesulfurization, hydrodenitrogenation, aromatic hydrocarbon hydrogenation saturation, hydrodemetallization and the like can occur in the hydrofinishing treatment of step (5), wherein an important purpose is to saturate most of polycyclic aromatic hydrocarbons and at least part of monocyclic aromatic hydrocarbons in the heavy diesel fraction to improve cracking performance and produce more olefins and aromatic hydrocarbons, preferably, in the hydrofinishing treatment, hydrogenation conditions are such that the polycyclic aromatic hydrocarbon saturation in the hydrogenation product of the heavy diesel fraction is not less than 85% by weight, preferably not less than 90% by weight, the total aromatic hydrocarbon saturation is 15-80% by weight, preferably 40-80% by weight, and the distillation range is 200-.

Wherein, the polycyclic aromatic hydrocarbon saturation ratio of the heavy diesel oil fraction hydrogenation product is calculated by adopting the following formula:

A_2m＝(A_2f–A_2p)/A_2fx 100 wt.%;

in the formula: a. the_2mThe polycyclic aromatic hydrocarbon saturation rate of the hydrogenation product of the heavy diesel oil fraction is weight percent;

A_2fis the weight fraction of polycyclic aromatic hydrocarbon in the heavy diesel oil fraction;

A_2pis the weight fraction of polycyclic aromatic hydrocarbon in the hydrogenation product of heavy diesel oil fraction.

The total aromatic saturation rate of the heavy diesel oil fraction hydrogenation product is calculated by adopting the following formula:

A_ta＝(A_af–A_ap)/A_afx 100% by weight

In the formula: a. the_taThe total aromatic saturation rate of the hydrogenation product of the heavy diesel oil fraction is weight percent;

A_afis the weight fraction of all aromatic hydrocarbons in the heavy diesel oil fraction;

A_apis the weight fraction of all aromatic hydrocarbons in the hydrogenation product of the heavy diesel oil fraction.

Preferably, the conditions for hydrogenating the heavy diesel oil fraction include a hydrogen partial pressure of 3-12MPa, preferably 6-12MPa, a reaction temperature of 260-450 ℃, preferably 280-400 ℃, more preferably 345-355 ℃, further preferably 350-355 ℃ and a hydrogen-oil volume ratio of 400-1600Nm³/m³Preferably 500-1000Nm³/m³More preferably 700-800Nm³/m³More preferably 750-850Nm³/m³The liquid hourly space velocity is 0.3-4h^-1Preferably 0.5 to 2h^-1。

According to the invention, although the heavy diesel oil fraction hydrogenation product can be directly returned to the catalytic cracking unit for cracking treatment, in order to more fully utilize heat and materials in the reaction process and fully recover the heavy diesel oil fraction hydrogenation product, heat exchange and gas-liquid separation are carried out on the heavy diesel oil fraction hydrogenation product before the heavy diesel oil fraction hydrogenation product is introduced into the catalytic cracking unit. The degree of the heat exchange is preferably that as much heavy diesel oil fraction hydrogenation product as possible exists in a liquid form, so that the heavy diesel oil fraction hydrogenation product and the hydrogen-rich gas can be effectively separated in the subsequent gas-liquid separation. After separation, the purified heavy diesel oil fraction hydrogenation product can be directly returned to the catalytic cracking unit for preparation of a target product, and the obtained hydrogen-rich gas can be recycled to the hydrogenation unit as at least part of hydrogen of the hydrogenation unit.

According to the present invention, in order to further improve the purity of the hydrogen-rich gas, it is preferable that before the hydrogen-rich gas is circulated to the hydrogenation unit, the method further includes subjecting the hydrogen-rich gas to gas-liquid separation and compression in sequence to obtain circulating hydrogen, and circulating the circulating hydrogen to the hydrogenation unit.

In a second aspect, the present invention provides a diesel fuel processing system comprising:

a catalytic cracking unit 1 for catalytically cracking the cracked feedstock oil to produce a cracked product, the cracked product containing catalytically cracked diesel oil;

the catalytic cracking unit 2 is used for carrying out catalytic cracking on the cracking raw oil to produce a cracking product, and the cracking product contains catalytic cracking diesel oil;

the diesel oil fractionating unit 3 is used for receiving the catalytic cracking diesel oil and fractionating the obtained mixed diesel oil to obtain a light diesel oil fraction and a heavy diesel oil fraction;

the diesel oil fractionating unit 3 is communicated with the catalytic cracking unit 1 and is used for introducing the light diesel oil fraction into the catalytic cracking unit 1 to serve as at least part of the cracked raw oil;

the hydrogenation unit 4 is used for receiving the heavy diesel oil fraction and carrying out hydrogenation treatment on the heavy diesel oil fraction to obtain a heavy diesel oil fraction hydrogenation product;

the hydrogenation unit 4 is communicated with the catalytic cracking unit 2 and is used for introducing the heavy diesel oil fraction hydrogenation product into the catalytic cracking unit 2 to serve as at least part of the cracking raw oil.

Preferably, the hydrogenation unit 4 comprises a first hydrogenation zone 41 and a second hydrogenation zone 42 for subjecting the heavy diesel fraction to a first hydrotreatment and a second hydrotreatment.

Preferably, a cracking reaction device and a cracked product fractionating device are arranged in the catalytic cracking unit 1.

Preferably, a cracking reaction device and a cracking product fractionating device are arranged in the catalytic cracking unit 2.

Preferably, the system also comprises a heat exchange unit 5 connected with the hydrogenation unit 4 and used for exchanging heat for the hydrogenation product of the heavy diesel oil fraction.

Preferably, the system further comprises a first gas-liquid separation unit 6, which is respectively connected with the heat exchange unit 5 and the catalytic cracking unit 2, and is used for performing gas-liquid separation on the heat-exchanged heavy diesel fraction hydrogenation product, introducing the obtained liquid phase into the catalytic cracking unit 1 as at least part of the cracking raw oil, and introducing the obtained hydrogen-rich gas into the hydrogenation unit 4 as at least part of hydrogen of the hydrogenation unit 4.

Preferably, the system further comprises a second gas-liquid separation unit 7 connected to the first gas-liquid separation unit 6 for further gas-liquid separation of the hydrogen-rich gas.

Preferably, the system further comprises a gas compression unit 8 for compressing the hydrogen-rich gas after gas-liquid separation again to obtain recycle hydrogen, and recycling the recycle hydrogen to the hydrogenation unit 4 as at least part of hydrogen of the hydrogenation unit 4.

The present invention will be described in detail below by way of examples.

The following examples all employ the process shown in fig. 1, specifically:

(1) introducing the cracked raw oil into a catalytic cracking unit 1 for catalytic cracking to produce cracked products, and fractionating the cracked products to obtain gasoline rich in aromatic hydrocarbons, catalytic cracked diesel oil and the like; wherein, the catalytic cracking conditions comprise: the reaction temperature is 560 ℃, the mass ratio of the agent to the oil is 7, the oil gas retention time is 7s, the pressure is 0.25MPa, the water vapor/raw material ratio is 0.04, the aging agent MAT is 66, and the catalyst MLC-500.

(2) Introducing cracking raw oil into a catalytic cracking unit 2 for catalytic cracking to produce a cracking product, and fractionating the cracking product to obtain a low-carbon olefin product, a light naphtha product, a heavy naphtha product, catalytic cracking diesel oil and the like; wherein, the catalytic cracking conditions comprise: the reaction temperature is 580-600 ℃, the mass ratio of the oil to the solvent is 10, the oil gas retention time is 7s, the pressure is 0.25MPa, the steam/raw material ratio is 0.2, and the catalyst MMC-2 is adopted.

(3) Mixing the catalytic cracking diesel oil and the catalytic cracking diesel oil in a mixing pipeline, introducing the obtained mixed diesel oil raw material into a diesel oil fractionating unit 3, and fractionating in the diesel oil fractionating unit 3 to obtain a light diesel oil fraction and a heavy diesel oil fraction.

(4) The light diesel oil fraction is directly returned to the catalytic cracking unit 1 through a circulating pipeline without being subjected to hydrotreating to be used as at least part of the cracked raw oil to be mixed with the catalytic cracking raw oil existing in the catalytic cracking unit 1, and then catalytic cracking is performed.

(5) The heavy diesel oil fraction is introduced into a hydrogenation unit 4 to be respectively subjected to hydrotreating in the presence of a first hydrogenation catalyst in a first hydrogenation zone 41 and in the presence of a second hydrogenation catalyst in a second hydrogenation zone 42, so as to obtain a heavy diesel oil fraction hydrogenation product.

(6) And (3) carrying out heat exchange on the heavy diesel oil fraction hydrogenation product in a heat exchange unit 5, and carrying out gas-liquid separation on the heavy diesel oil fraction hydrogenation product subjected to heat exchange in a first gas-liquid separation unit 6 to obtain a purified heavy diesel oil fraction hydrogenation product and a hydrogen-rich gas.

And the purified heavy diesel oil fraction hydrogenation product is returned to the catalytic cracking unit 2 through a circulating pipeline to be used as at least part of cracking raw oil to be mixed with the catalytic cracking raw oil existing in the catalytic cracking unit 2, and then catalytic cracking is carried out.

The hydrogen-rich gas is further subjected to gas-liquid separation in the first gas-liquid separation unit 7, and the separated gas phase is compressed in a recycle hydrogen compressor (gas compression unit 8) to meet the requirements and then recycled to the hydrogenation unit 4 for recycling.

Preparation example 1

This preparation example serves to illustrate the source of the first hydrogenation catalyst

The first hydrogenation catalyst was a commercially available molded RS-2100 catalyst produced by ChangLing catalyst division, petrochemical Co., Ltd., China, and was a nickel-tungsten catalyst having a bulk density of 1.03g/cm³Average particle diameter of 2-3mm and specific surface area of 165m²/g。

Preparation example 2-1

This preparation example is intended to illustrate the second hydrogenation catalyst and the method for preparing the same.

(1) Commercially available white carbon black (specific surface area: 220 m)²Per g, the average pore diameter is 12.7nm) and basic cobalt carbonate powder are uniformly mixed and then roasted at 400 ℃ for 3h to obtain the cobalt-containing inorganic refractory powder.

Wherein the amount of basic cobalt carbonate used corresponds to a cobalt (calculated as cobalt oxide) content of the catalyst of 22.0 wt.%.

(2) Adding a certain amount of MoO₃And respectively adding the basic cobalt carbonate and the citric acid into the aqueous solution containing the phosphoric acid, and heating and stirring the mixture until the basic cobalt carbonate and the citric acid are completely dissolved to obtain the impregnation solution containing the active metal.

Wherein the mass of the citric acid is 20 weight percent of the mass of the inorganic refractory component.

(3) The impregnating solution and the inorganic refractory component are uniformly mixed, and then extruded into strips for forming. The catalyst A1 in the oxidized state was prepared by drying at 200 ℃ for 3h to give a particle size of 1.6 mm.

Wherein the impregnating solution and the cobalt-containing inorganic refractory powder are mixed in such a proportion that the content of molybdenum oxide is 55.0 wt%, the content of cobalt oxide is 30.0 wt%, and P is in the catalyst, based on the dry weight of the catalyst and calculated as an oxide₂O₅The content was 5% by weight, and the content of the inorganic refractory component was 10.0% by weight.

After the catalyst A1 is roasted at 400 ℃ for 3h, the pore size distribution of the catalyst A is analyzed by using low-temperature nitrogen adsorption and mercury porosimetry. The specific surface area of the catalyst was 96.0m²(ii)/g, the pore diameter distribution was 2 to 40nm and 100-300nm, wherein the ratio of the pore volume of 2 to 40nm to the total pore volume was 86.6% (wherein the ratio of the pore volume of 2 to 4nm to the total pore volume was 9.5%), the ratio of the pore volume of 100-300nm to the total pore volume was 7.2%, the pore volume was 0.26mL/g, and the average pore diameter was 10.8 nm.

Preparation examples 2 to 2

This preparation example is intended to illustrate the second hydrogenation catalyst and the method for preparing the same.

The preparation of the second hydrofinishing catalyst A2 was carried out according to the method of preparation 2-1, except that in step (1) no group VIII metal element was introduced, but the same amount of group VIB metal element was introduced, the rest being the same, and the characterization was carried out according to the method of preparation 1, each parameter being within the scope of the present invention.

Comparative preparation example 1

This comparative example serves to illustrate a reference second hydrogenation catalyst and a method of making the same.

Commercially available white carbon black (specific surface area: 220 m)²The average pore diameter is 12.7nm), and basic cobalt carbonate powder are uniformly mixed without a roasting step to obtain the inorganic refractory powder containing cobalt. Wherein the amount of basic cobalt carbonate used corresponds to a cobalt (calculated as cobalt oxide) content of the catalyst of 22.0 wt.%. Then, an impregnation solution was prepared in accordance with the procedure (2) of preparation example 1, and a catalyst D1 was prepared in accordance with the procedure (3) of preparation example 1, the inorganic refractory components and the metal composition in the dry basis of the catalyst being the same as those of the catalyst of preparation example 1.

Comparative preparation example 2

This comparative example serves to illustrate a reference second hydrogenation catalyst and a method of making the same.

The production of a hydrorefining catalyst D2 was carried out in the same manner as in production example 2-1, except that no organic acid was added in the preparation of the active component solution, and the remainder was the same.

Comparative preparation example 3

This comparative example serves to illustrate a reference second hydrogenation catalyst and a method of making the same.

The hydrorefining catalyst D3 was prepared according to the method of preparation example 2-1, except that only white carbon black was replaced with pseudo boehmite powder, and the rest was the same.

Comparative preparation example 4

This comparative example serves to illustrate a reference second hydrogenation catalyst and a method of making the same.

The production of a hydrorefining catalyst D4 was carried out in the same manner as in production example 2-1, except that the group VIII metal element was not introduced in step (1), and the group VIII metal element was completely introduced in step (2), and the remainder was the same.

Catalyst sulfidation

Each catalyst prepared as above employs a temperature programmed sulfiding process to convert an oxidized catalyst to a sulfided catalyst. The vulcanization conditions are as follows: the vulcanization pressure is 6.4MPa, and the vulcanized oil contains CS₂2% by weight of keroseneThe volume space velocity is 2h^-1And the hydrogen-oil ratio is 300v/v, the constant temperature is kept for 6h at 230 ℃/h, then the temperature is increased to 320 ℃ for vulcanization for 8h, and the temperature increase rate of each stage is 10 ℃/h.

Example 1