A catalytic diesel combined treatment process and system

Abstract

The present invention discloses a catalytic diesel combined treatment process and system, the treatment process includes the following contents: catalytic diesel is fractionated to obtain component A, component B and component C, component A, component B and component C enter different catalyst beds in a fixed bed hydrogenation reaction zone for reaction respectively, the first liquid phase material obtained after gas-liquid separation of the reaction effluent enters an ebullating bed hydrogenation reaction zone for reaction, and the reaction effluent is separated to obtain naphtha and unconverted diesel. The treatment process is based on the concept of molecular refining combined with a fixed bed-ebullating bed hydrogenation combined process, and the different aromatics in the catalytic diesel raw material are matched with suitable reaction paths for treatment, so as to solve the problems of hot spots and high hydrogen consumption in the existing catalytic diesel process, and at the same time greatly improve the quality and yield of high value-added aromatic products, and the operation cycle of the device is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and in particular relates to a catalytic diesel high-efficiency conversion process and system. Background Art

[0002] At present, the total annual processing capacity of catalytic cracking units in my country has exceeded 170 million tons, and the annual output of catalytic diesel has reached 35 million tons. In recent years, on the one hand, as the quality of crude oil deteriorates, the raw materials processed by catalytic cracking have become increasingly heavy and inferior, resulting in increased operating severity of catalytic cracking units and reduced quality of catalytic diesel; on the other hand, in order to reduce the olefin content of gasoline and produce more propylene, many catalytic units use MIP, MIP-CGP or FDFCC technology, but these technologies, while producing more propylene and effectively reducing gasoline olefins, further deteriorate the quality of catalytic diesel. Although the properties of catalytic diesel from different companies are different, they all have common characteristics, namely high density, low cetane number and high aromatic content. Catalytic diesel has become the main bottleneck restricting the current refining companies to achieve diesel quality upgrades with high efficiency and low consumption. For the hydrogenation technology of catalytic diesel with low-quality high aromatics, it can be divided into hydrorefining technology, hydromodification technology, hydrocracking technology and hydroconversion technology according to different production purposes. For example, UOP's MQD (Maximum quality distillate) joint refining technology, MAK-LCO hydro-modification process, HyCycle Unicracking process and Sinopec FRIPP's FD2G technology, all of these different processing technologies are used to convert low-quality diesel into clean diesel oil or gasoline, chemical products; currently, several processing technologies have certain market applications, but they all have problems, mainly because the cycloalkane content in the product is too high, resulting in product indicators that do not meet the load requirements, high hydrogen consumption, and poor economy. Therefore, finding an efficient, low-consumption and economical processing route for catalytic diesel quality upgrade as soon as possible is a technical problem that needs to be solved urgently, which can greatly promote the physical efficiency of enterprises.

[0003] CN107286987A provides a combined process for treating inferior diesel. The inferior diesel raw material is mixed with hydrogen and then enters a fixed bed hydrogenation reaction zone, where a hydrogenation reaction is carried out under the action of a hydrorefining catalyst; the resulting reaction oil is mixed with hydrogen and then enters an ebullated bed hydrocracking reaction zone, where a hydrocracking reaction is carried out in the presence of an ebullated bed hydroconversion catalyst, and the product is obtained after separation. In this combined process, inferior diesel is directly processed in a fixed bed, which is prone to generate hot spots, the reaction process is difficult to control, the product quality is poor, the yield is low, and the device operation cycle is short, the hydrogen consumption is relatively large, and the economy is poor. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a combined catalytic diesel processing process. The processing process is based on the concept of molecular refining, by separating the catalytic diesel according to different hydrocarbon components, and combining the pre-fractionation and fixed bed-boiling bed hydrogenation combined process, the different aromatics in the catalytic diesel raw materials are matched with suitable reaction pathways for processing, thereby solving the problems of hot spots and high hydrogen consumption in the existing catalytic diesel process treatment, and at the same time greatly improving the quality and yield of high value-added aromatic products, and the operation cycle of the device is greatly improved.

[0005] The present invention provides a catalytic diesel combined treatment process, the treatment process comprising the following contents:

[0006] (1) After fractionation of catalytic diesel, component A rich in single-ring aromatics, component B rich in double-ring aromatics, and component C rich in three-ring or higher aromatics are obtained;

[0007] (2) In the presence of hydrogen, component A, component B and component C obtained in step (1) are fed into different catalyst beds of the fixed bed hydrogenation reaction zone through the third feed port, the second feed port and the first feed port respectively to react, and the reaction effluent is subjected to gas-liquid separation to obtain a first gas phase material and a first liquid phase material;

[0008] (3) The first liquid phase material obtained in step (3) enters the ebullated bed hydrogenation reaction zone, reacts under the action of hydrogen and the ebullated bed hydrogenation catalyst, and the reaction effluent is separated to obtain a second gas phase material and a second liquid phase material. The second liquid phase material is further fractionated to obtain naphtha and unconverted diesel.

[0009] Furthermore, in the above-mentioned catalytic diesel combined treatment process, the catalytic diesel comes from the diesel fraction obtained by catalytic cracking reaction in the catalytic device. Generally, the initial distillation point of the catalytic diesel is generally not less than 150°C, and the final distillation point is generally not higher than 350°C. The aromatic content in the catalytic diesel is higher than 50wt%, preferably 55wt% to 90wt%, and the density at 20°C is generally greater than 920kg / m 3 , the nitrogen content is usually 200-1500 mg / kg.

[0010] Furthermore, in the above catalytic diesel combined treatment process, the cutting point temperature of component A and component B is 180-250°C, preferably 180-220°C; the cutting point temperature of component B and component C is 260-330°C, preferably 290-310°C.

[0011] Furthermore, in the above-mentioned catalytic diesel combined treatment process, three catalyst beds are arranged inside the fixed bed hydrogenation reaction zone according to the flow direction of the liquid material, specifically, a first catalyst bed, a second catalyst bed and a third catalyst bed are arranged in sequence, wherein the first feed port is arranged at the top of the reactor, the second feed port is arranged between the first catalyst bed and the second catalyst bed, and the third feed port is arranged between the second catalyst bed and the third catalyst bed.

[0012] Furthermore, in the above-mentioned catalytic diesel combined treatment process, component A rich in monocyclic aromatics enters the third catalyst bed of the fixed bed hydrogenation reaction zone through the third feed port for reaction, component B rich in bicyclic aromatics enters the second catalyst bed of the fixed bed hydrogenation reaction zone through the second feed port for reaction, and component C rich in three or more aromatics enters the first catalyst bed of the fixed bed hydrogenation reaction zone through the first feed port for reaction. The first catalyst bed has a high concentration of new hydrogen, and the polycyclic aromatics rich in component C mainly undergo high hydrogenation saturation reaction in the first catalyst bed. At the same time, the reaction process of entering the first catalyst bed is long, ensuring the reaction effect. Component B rich in bicyclic aromatics enters from the second feed port and is mixed with component C (currently mainly bicyclic aromatics) after denitrogenation and partial aromatic saturation, and further selective hydrogenation saturation reaction of bicyclic aromatics occurs in the second catalyst bed. At the same time, the feed temperature of component B is optimized to adjust the appropriate reaction temperature of bicyclic aromatics, solving the problem of uncontrollable high temperature of the second reaction bed due to the large heat release of polycyclic aromatics in the upper bed.

[0013] Furthermore, in the above catalytic diesel combined treatment process, the unconverted diesel obtained in step (3) can be returned to the fixed bed hydrogenation reaction zone for treatment, preferably returned to the second catalyst bed of the fixed bed hydrogenation reaction zone through the second feed inlet for treatment.

[0014] Furthermore, in the above-mentioned catalytic diesel combined treatment process, the first gas phase material obtained in step (1) and the second gas phase material obtained in step (3) enter the hydrogen separation and purification unit for treatment, and circulating hydrogen and light hydrocarbons are obtained after treatment, wherein the hydrogen separation and purification unit includes a light hydrocarbon recovery tower, a hydrogen sulfide removal tower and a membrane separation device, and the concentrated hydrogen is returned to the fixed bed hydrogenation reaction zone and / or the ebullating bed hydrogenation reaction zone as circulating hydrogen for utilization. The specific setting of the hydrogen separation and purification unit can be reasonably selected by those skilled in the art according to actual conditions.

[0015] Furthermore, in the above catalytic diesel combined treatment process, the naphtha obtained by fractionation of the second liquid phase material in step (4) can be further separated into light naphtha and heavy naphtha according to actual needs. The light naphtha and heavy naphtha can be directly discharged from the device as products, and their main components include monocyclic aromatic hydrocarbon components with carbon numbers of C5 to C9, specifically light aromatic hydrocarbons such as benzene, toluene, xylene, methyl ethylbenzene, and mesitylene.

[0016] Further, in the above catalytic diesel combined treatment process, the reaction pressure of the fixed bed hydrogenation reaction zone is as follows;

[0017] Reaction conditions of the first catalyst bed: reaction pressure of 5.0-20.0 MPa, preferably 6.0-10.0 MPa; reaction temperature of 300-420°C, preferably 320-390°C; hydrogen-to-oil volume ratio of 500-2000, preferably 600-1500; liquid hourly volume space velocity of 0.1-5.0 h -1 , preferably 0.5~2.0h -1 ;

[0018] The reaction conditions of the second catalyst bed are as follows: the reaction pressure is 5.0-20.0 MPa, preferably 6.0-10.0 MPa; the reaction temperature is 330-420°C, preferably 340-400°C; the hydrogen-oil volume ratio is 500-2000, preferably 600-1500; the liquid hourly volume space velocity is 0.1-5.0 h -1 , preferably 0.5~2.0h -1 ;

[0019] The third catalyst bed reaction conditions are as follows: reaction pressure is 5.0-20.0 MPa, preferably 6.0-10.0 MPa; reaction temperature is 300-420°C, preferably 350-420°C; hydrogen-to-oil volume ratio is 500-2000, preferably 600-1500; liquid hourly volume space velocity is 0.1-5.0 h -1 , preferably 0.5~2.0h -1 .

[0020] Furthermore, the reaction temperature of the first catalyst bed is 5-20°C lower than that of the second catalyst bed, preferably 5-10°C lower; the reaction temperature of the second catalyst bed is 5-20°C lower than that of the third catalyst bed, preferably 5-10°C lower.

[0021] Furthermore, in the above catalytic diesel combined treatment process, the first catalyst bed is loaded with a hydrogenation catalyst with a strong denitrification function, the second catalyst bed is loaded with a hydrogenation catalyst with a denitrification and desulfurization function, and the third catalyst bed is loaded with a hydrogenation catalyst with a strong desulfurization function.

[0022] Furthermore, in the above-mentioned catalytic diesel combined treatment process, the first catalyst bed is loaded with Ni-Mo or Ni-W hydrogenation catalyst, and the pore volume of pores with a diameter of 60 to 600 angstroms accounts for 30% to 60% of the total pore volume, and the pores less than 60 angstroms account for 10% to 40% of the total pore volume; the second catalyst bed is loaded with Ni-Co-Mo hydrogenation catalyst, and the pore volume of pores with a diameter of 60 to 600 angstroms accounts for 30% to 50% of the total pore volume, and the pores less than 60 angstroms account for 20% to 40% of the total pore volume; the third catalyst bed is loaded with Co-Mo hydrogenation catalyst, wherein the pore volume of pores with a diameter of 60 to 600 angstroms accounts for 30% to 50% of the total pore volume, and the pores less than 60 angstroms account for 25% to 50% of the total pore volume.

[0023] Furthermore, in the above-mentioned catalytic diesel combined treatment process, more than one ebullated bed reactor can be set in the ebullated bed hydrogenation reaction zone, and preferably an ebullated bed reactor with a three-phase separator arranged inside the reactor is used. Specifically, an ebullated bed reactor with a three-phase separator developed by Fushun Petrochemical Research Institute of China Petroleum and Chemical Corporation can be used.

[0024] Furthermore, in the above-mentioned catalytic diesel combined treatment process, the ebullated bed hydrogenation catalyst can be selected from the existing diesel hydrogenation catalyst in the art, or prepared by itself according to the method disclosed in the prior art. Specifically in the present invention, the ebullated bed hydrogenation catalyst uses high-silicon alumina and molecular sieve as carriers, and uses Group VIII metals and Group VIB metals as active metal components. Based on the weight of the catalyst, the content of high-silicon alumina is 30% to 70%, the content of molecular sieve is 10% to 50%, the content of Group VIII metal in terms of oxide is 1% to 9%, and the content of Group VIB metal in terms of oxide is 10% to 30%. The Group VIII metal is preferably Ni and / or Co; the Group VIB metal is preferably W and / or Mo; the molecular sieve is selected from one or more of Y-type molecular sieve, β molecular sieve, ZSM-5 molecular sieve, SAPO molecular sieve, and MCM-41 mesoporous molecular sieve.

[0025] Furthermore, in the above-mentioned catalytic diesel combined treatment process, the process conditions of the ebullated bed hydrogenation reaction zone are: reaction temperature is 350-450°C, preferably 380-440°C, reaction pressure is 5.0-15.0MPa, preferably 6.0-10.0MPa, hydrogen-to-oil volume ratio is 500-2000, preferably 600-1500, liquid hourly volume space velocity is 0.1-5.0h -1 , preferably 0.2~2.0h -1 .

[0026] Furthermore, in the above-mentioned catalytic diesel combined treatment process, the first gas-liquid separation unit and the second gas-liquid separation unit usually include various forms of gas-liquid separators, generally including at least one of a hot high-pressure gas-liquid separator, a hot low-pressure gas-liquid separator, a cold high-pressure gas-liquid separator, and a cold low-pressure gas-liquid separator.

[0027] Furthermore, in the above catalytic diesel combined treatment process, the fractionation process can be achieved by using a fractionation tower, and the fractionation tower can be any type of fractionation tower currently available in the art, specifically a plate tower or a packed tower.

[0028] The second aspect of the present invention provides a catalytic diesel combined treatment system, comprising:

[0029] The first fractionation unit is used to receive and separate the catalytic diesel, and obtain a component A rich in monocyclic aromatic hydrocarbons, a component B rich in dicyclic aromatic hydrocarbons, and a component C rich in tricyclic aromatic hydrocarbons or higher after fractionation;

[0030] A fixed bed hydrogenation reaction zone, which is used to receive hydrogen and component A, component B and component C obtained by the first fractionation unit, and component A, component B and component C enter the fixed bed hydrogenation reaction zone through the first feed inlet, the second feed inlet and the third feed inlet respectively;

[0031] A first gas-liquid separation unit is used to receive the reaction effluent from the fixed-bed hydrogenation reaction zone and obtain a first gas phase material and a first liquid phase material after gas-liquid separation;

[0032] An ebullated bed hydrogenation reaction zone, which is used to receive hydrogen and the first liquid phase material from the first gas-liquid separation unit, and react under the action of an ebullated bed hydrogenation catalyst;

[0033] A second gas-liquid separation unit is used to receive the reaction effluent from the ebullated bed hydrogenation reaction zone, and obtain a second gas phase material and a second liquid phase material after separation of the reaction effluent;

[0034] The second fractionation unit is used to receive the second liquid phase material from the second gas-liquid separation unit, and obtain naphtha and unconverted diesel after separation.

[0035] Furthermore, in the above-mentioned catalytic diesel combined processing system, three catalyst beds are arranged inside the fixed bed hydrogenation reaction zone according to the flow direction of the liquid phase material, specifically, a first catalyst bed, a second catalyst bed and a third catalyst bed are arranged in sequence, wherein the first feed port is arranged at the top of the reactor, the second feed port is arranged between the first catalyst bed and the second catalyst bed, and the third feed port is arranged between the second catalyst bed and the third catalyst bed; component A rich in monocyclic aromatic hydrocarbons enters the second catalyst bed of the fixed bed hydrogenation reaction zone through the second feed port for reaction, component B rich in dicyclic aromatic hydrocarbons enters the third catalyst bed of the fixed bed hydrogenation reaction zone through the third feed port for reaction, and component C rich in three or more ring aromatic hydrocarbons enters the first catalyst bed of the fixed bed hydrogenation reaction zone through the first feed port for reaction.

[0036] Furthermore, in the above catalytic diesel combined treatment system, the unconverted diesel obtained by the second fractionation unit can be returned to the fixed bed hydrogenation reaction zone via a pipeline for treatment, preferably returned to the third catalyst bed of the fixed bed hydrogenation reaction zone via a third feed inlet for treatment.

[0037] Furthermore, in the above-mentioned catalytic diesel combined processing system, the system includes a hydrogen separation and purification unit, which is used to receive the first gas phase material from the first gas-liquid separation unit and the second gas phase material from the second gas-liquid separation unit, and obtain circulating hydrogen and light hydrocarbons after processing; wherein the hydrogen separation and purification unit includes a light hydrocarbon recovery device, a hydrogen sulfide removal tower and a membrane separation device, and the concentrated hydrogen is returned to the fixed bed hydrogenation reaction zone and / or the ebullating bed hydrogenation reaction as circulating hydrogen for utilization. The specific setting of the hydrogen separation and purification unit can be reasonably selected by those skilled in the art according to actual conditions.

[0038] Furthermore, in the above-mentioned catalytic diesel combined treatment system, more than one ebullated bed reactor can be set in the ebullated bed hydrogenation reaction zone, and preferably an ebullated bed reactor with a three-phase separator arranged inside the reactor is used. Specifically, an ebullated bed reactor with a three-phase separator developed by Fushun Petrochemical Research Institute of China Petroleum and Chemical Corporation can be used.

[0039] Furthermore, in the above-mentioned catalytic diesel combined processing system, the first gas-liquid separation unit and the second gas-liquid separation unit usually include various forms of gas-liquid separators, generally including at least one of a hot high-pressure gas-liquid separator, a hot low-pressure gas-liquid separator, a cold high-pressure gas-liquid separator, and a cold low-pressure gas-liquid separator.

[0040] Furthermore, in the above catalytic diesel combined treatment system, the fractionation unit is provided with at least one fractionation tower, and the fractionation tower can be any type of fractionation tower currently available in the art, specifically a plate tower or a packed tower.

[0041] Compared with the prior art, the catalytic diesel processing technology and processing system provided by the present invention have the following advantages:

[0042] (1) In the catalytic diesel combined treatment process provided by the present invention, according to the different suitable reaction conditions for different hydrocarbon molecules, the catalytic diesel is subjected to hydrocarbon separation and then partitioned reaction. Component A is rich in monocyclic aromatics, component B is rich in dicyclic aromatics, and component C is rich in polycyclic aromatics. The hydrogenation processes of monocyclic, dicyclic and polycyclic aromatics all have their suitable reaction ranges. For the catalytic diesel hydrocracking route to produce more light aromatics, the suitable aromatic conversion path is the gradual selective hydrogenation saturation of polycyclic aromatics. If monocyclic, dicyclic and polycyclic aromatics are hydrogenated under the same reaction conditions and catalyst, it is bound to cause the occurrence of non-ideal hydrogenation supersaturation reaction, thereby reducing the yield of the target product. In addition, in the process of hydrocarbon separation, the degree of impurity enrichment is actually classified, wherein component C is a high nitrogen fraction, while the impurity content in component A and component B is relatively low, thereby achieving multiple separations of aromatics and impurities.

[0043] (2) In the catalytic diesel combined treatment process provided by the present invention, the reaction conversion process adopts a fixed bed-ebullated bed combined hydrogenation process, and the fixed bed unit adopts a staged feeding mode, combined with catalyst grading loading, and the aromatic content entering the ebullated bed unit is retained to the greatest extent under the premise of ensuring that the impurity removal reaches the index. The first catalyst bed is loaded with a catalyst with a strong denitrification function. Since the temperature of the reaction bed is relatively low, the hydrogen partial pressure is high, and the hydrogen sulfide concentration is low, it is conducive to the hydrogenation reaction of nitrogen-containing aromatics; the second bed device has a catalyst with strong hydrogenation denitrification and desulfurization performance. The sulfur and nitrogen impurity contents in the material in the reaction bed are at an intermediate level, and at the same time, it ensures that the sulfur is easily removed and the nitrogen-containing impurities are further removed; the third bed device is loaded with a strong desulfurization catalyst with an alkyl transfer function. The hydrogen partial pressure of the bed is relatively low, the concentrations of hydrogen sulfide and ammonia are high, and the reaction temperature is high. Under the restriction of thermodynamic equilibrium, the aromatic hydrogenation saturation equilibrium constant decreases, and the sulfur content in the aromatics is further removed through the alkyl transfer function.

[0044] (3) In the catalytic diesel combined treatment process provided by the present invention, for the bicyclic aromatic hydrocarbons rich in hydrogenated to one ring saturated in the product oil after fixed-bed hydrorefining, the ebullating bed hydrogenation process can utilize the uniform temperature and pressure characteristics in the ebullating bed reactor to optimize the ring-opening reaction path of such substances and retain the monocyclic aromatic hydrocarbons therein.

[0045] (4) In the catalytic diesel combined treatment process provided by the present invention, the unconverted diesel in the hydrogenation product oil is returned to the fixed bed hydrogenation specific reaction zone, which can further achieve precise hydrogenation, maximize the production of light aromatics, and reduce diesel production. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1This is a schematic diagram of the catalytic diesel combined treatment process provided by the present invention.

[0047] Among them, 1-catalytic diesel, 2-first fractionation unit, 3-component A, 4-component B, 5-component C, 6-first catalyst bed, 7-second catalyst bed, 8-third catalyst bed, 9-first gas-liquid separation unit, 10-first gas phase material, 11-first liquid phase material, 12-ebullated bed hydrogenation reaction zone, 13-second gas-liquid separation unit, 14-hydrogen separation and purification unit, 15-circulating hydrogen, 16-second fractionation unit, 17-unconverted diesel, 18-light naphtha, 19-heavy naphtha, 20-light hydrocarbon fraction.

[0048] Figure 2 This is a schematic diagram of the catalytic diesel treatment process flow of Comparative Example 1 of the present invention.

[0049] Figure 3 This is a schematic diagram of the catalytic diesel treatment process flow of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0050] Next, the technical features of the present invention will be further described through embodiments and in conjunction with the accompanying drawings, but these embodiments cannot limit the present invention.

[0051] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0052] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different directions of objects in use or operation in addition to the directions drawn in the drawings. For example, if the object in the figure is turned over, the elements described as being "below" or "below" other elements or features will be oriented "above" the elements or features. Therefore, the exemplary term "below" can include both below and above directions. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0053] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0054]

[0043] All numerical values ​​for parameters (eg, amounts or conditions) herein are to be understood as being modified in all instances by the term "about", whether or not "about" actually appears before the numerical value.

[0055] like Figure 1 As shown, the combined treatment process of catalytic diesel of the present invention is as follows: catalytic diesel 1 enters the first fractionation unit 2, and after separation, component A3, component B4 and component C5 are obtained, component C5 enters the first catalyst bed 6 in the fixed bed hydrogenation reaction zone, component B4 enters the second catalyst bed 7 in the fixed bed hydrogenation reaction zone, component A3 enters the third catalyst bed 8 of the fixed bed reactor, and reacts under the action of hydrogen, and the fixed bed product oil obtained by the reaction enters the first gas-liquid separation unit 9, and after separation, a first gas phase stream 10 and a first liquid phase stream 11 are obtained, and the first liquid phase stream 11 enters the ebullating bed hydrogenation reaction zone 12, and reacts under the action of hydrogen. The reaction takes place under the reaction, and the boiling bed hydrogenation generated oil obtained after the reaction enters the second gas-liquid separation unit 13. The second gas phase material and the first gas phase material 10 obtained after separation enter the hydrogen separation and purification unit 14 together for treatment. After the treatment, circulating hydrogen 15 and light hydrocarbons 20 are obtained. The liquid phase material obtained after separation in the second gas-liquid separation unit 13 enters the second fractionation unit 16 for separation to obtain light naphtha 18, heavy naphtha 19 and unconverted diesel 17. The light naphtha and the heavy naphtha are mixed and used as the raw material for the subsequent aromatic extraction device, among which the unconverted diesel 17 can be circulated to the second catalyst bed 7 of the fixed bed hydrogenation reaction zone for treatment.

[0056] The basic properties of the catalytic diesel used in the examples and comparative examples of the present invention are shown in Table 1.

[0057] Table 1 Basic properties of catalytic diesel

[0058]

[0059] Example 1

[0060] use Figure 1 In the process flow shown in the figure, the cutting point temperature of component A and component B is 210°C, and the cutting point temperature of component B and component C is 320°C; the reaction pressure of the fixed bed reaction unit is 8.0MPa, and the temperatures of the three reaction beds are 370°C, 380°C, and 390°C, respectively. Relative to the catalytic diesel feedstock, the hydrogen-to-oil volume ratio is 800, and the liquid hourly volume space velocity is 1.0h -1 The catalysts used in the first, second and third catalyst beds of the fixed bed were prepared in the laboratory according to conventional knowledge in the field. The catalyst in the first catalyst bed was supported by γ-alumina, and the molybdenum and nickel contents were 21.5wt% and 4.5wt% respectively, calculated as metal oxides, with a specific surface area of ​​168m 2 / g, pore volume of 0.39mL / g, average pore diameter of 90 angstroms, catalyst shape is columnar extrusion; the catalyst of the second catalyst bed uses γ-alumina as carrier, and the molybdenum, nickel and cobalt contents are 20.5wt%, 2.5wt% and 2.1wt% respectively calculated as metal oxides, and the specific surface area is 245m 2 / g, pore volume of 0.42mL / g, average pore diameter of 83 angstroms, and the catalyst shape is columnar extrusion; the catalyst of the third catalyst bed uses γ-alumina as the carrier, and the molybdenum and cobalt contents are 19.0w% and 3.5wt% respectively, calculated as metal oxides, and the specific surface area is 320 m 2 / g, pore volume of 0.23mL / g, average pore diameter of 78 angstroms, and catalyst shape of clover. The reaction conditions of the ebullient bed hydrogenation reaction zone are reaction temperature of 415℃, reaction pressure of 8.0MPa, hydrogen-to-oil volume ratio of 800, liquid hourly volume space velocity of 0.8h -1 The catalyst used was the spherical FC-70 hydrocracking catalyst developed by Sinopec Dalian Petrochemical Research Institute; at the same time, in the product oil fractionation unit, the cut point temperature of heavy naphtha and unconverted diesel was 200°C. The specific test results are shown in Table 2.

[0061] Example 2

[0062] The method is basically the same as Example 1, except that the temperatures of the three bed layers of the fixed bed are adjusted and changed, and the temperatures of the three reaction bed layers are 375°C, 385°C, and 395°C respectively; other conditions remain unchanged. The specific test results are shown in Table 2.

[0063] Example 3

[0064] The reaction conditions of the ebullated bed unit were basically the same as those of Example 1, except that the reaction conditions of the ebullated bed hydrogenation reaction zone were changed to a reaction temperature of 425°C, a reaction pressure of 8.5 MPa, a hydrogen-to-oil volume ratio of 800, and a liquid hourly volume space velocity of 0.6 h -1 The specific test results are shown in Table 2.

[0065] Comparative Example 1

[0066] Comparative Example 1: Figure 2In the process flow shown, catalytic diesel 1 and hydrogen are mixed and enter the first fixed bed reactor 2 for hydrofining reaction, sulfur and nitrogen impurities are removed, and aromatics are saturated. The hydrogenated oil obtained after the reaction then enters the second fixed bed reactor 3, in which a hydrocracking reaction is carried out, and the hydrogenated oil obtained enters the gas-liquid separator 4. The gas phase stream obtained after separation enters the hydrogen recovery unit 5 for treatment to obtain circulating hydrogen 7 and light hydrocarbon components 6, and the liquid phase stream enters the fractionation system 8 for separation to obtain light naphtha 9, heavy naphtha 10 and unconverted diesel 11, wherein the unconverted diesel 11 is returned to the second fixed bed reactor for further reaction. Among them, the catalyst of the device in the first fixed bed reactor is arranged in the same bed layer as the catalyst bed layer of the fixed bed reactor in Example 1, and the properties of the catalyst in each bed layer are the same as those in Example 1, except that the comparative catalytic diesel enters the reactor from the first bed layer of the fixed bed. The reaction conditions of the fixed bed and the ebullating bed are the same as those in Example 1. The specific test results are shown in Table 2.

[0067] Comparative Example 2

[0068] The process flow of Comparative Example 2 is the same as that of Comparative Example 1, except that the first fixed bed reaction unit is filled with only the first bed catalyst in Comparative Example 1, that is, the molybdenum and nickel contents are 21.5wt% and 4.5wt% respectively, calculated as metal oxides, and the specific surface area is 168m 2 / g, pore volume is 0.39mL / g, average pore diameter is 90 angstroms, and the catalyst shape is columnar extrusion; fixed bed reaction temperature is 370℃, hydrogen-to-oil volume ratio is 800, liquid hourly volume space velocity is 1.0h -1 , the specific test results are shown in Table 2.

[0069] Comparative Example 3

[0070] use Figure 3 The process flow shown in this comparative example is Figure 2 In the process flow shown, catalytic diesel 1 and hydrogen are mixed and enter the fixed bed reactor 2 for hydrofining reaction, sulfur and nitrogen impurities are removed, and aromatics are saturated. The hydrogenated oil obtained after the reaction then enters the ebullated bed reactor 3, in which a hydrocracking reaction is carried out, and the hydrogenated oil obtained enters the gas-liquid separator 4. The gas phase stream obtained after separation enters the hydrogen recovery unit 5 for treatment to obtain circulating hydrogen 7 and light hydrocarbon components 6, and the liquid phase stream enters the fractionation system 8 for separation to obtain light naphtha 9, heavy naphtha 10 and unconverted diesel 11, wherein the unconverted diesel 11 is returned to the ebullated bed reactor for further reaction. Among them, the catalyst of the device in the first fixed bed reactor is arranged in the same bed layer as the catalyst bed layer of the fixed bed reactor in Example 1, and the properties of the catalyst in each bed layer are the same as those in Example 1, except that the comparative catalytic diesel enters the reactor from the first bed layer of the fixed bed. The reaction conditions of the fixed bed and the ebullated bed are the same as those in Example 1. The specific test results are shown in Table 2.

[0071] Table 2 Test results

[0072]

Claims

1. A catalytic diesel combined treatment process, the treatment process comprising the following contents: (1) After fractionation of catalytic diesel, component A rich in single-ring aromatics, component B rich in double-ring aromatics, and component C rich in three-ring or higher aromatics are obtained; (2) In the presence of hydrogen, component A, component B and component C obtained in step (1) enter different catalyst beds in a fixed bed hydrogenation reaction zone through a third feed port, a second feed port and a first feed port respectively for reaction, and the reaction effluent is subjected to gas-liquid separation to obtain a first gas phase material and a first liquid phase material; according to the flow direction of the liquid phase material, a first catalyst bed, a second catalyst bed and a third catalyst bed are sequentially arranged inside the fixed bed hydrogenation reaction zone, wherein the first feed port is arranged at the top of the reactor, the second feed port is arranged between the first catalyst bed and the second catalyst bed, and the third feed port is arranged between the second catalyst bed and the third catalyst bed; the first catalyst bed is loaded with a Ni-Mo or Ni-W hydrogenation catalyst; the second catalyst bed is loaded with a Ni-Co-Mo hydrogenation catalyst; and the third catalyst bed is loaded with a Co-Mo hydrogenation catalyst; (3) The first liquid phase material obtained in step (2) enters the ebullated bed hydrogenation reaction zone, reacts under the action of hydrogen and an ebullated bed hydrogenation catalyst, and the reaction effluent is separated to obtain a second gas phase material and a second liquid phase material. The second liquid phase material is further fractionated to obtain naphtha and unconverted diesel; the naphtha is used as a raw material for an aromatics extraction unit.

2. The catalytic diesel combined treatment process according to claim 1, wherein: Catalytic diesel comes from the diesel fraction obtained by catalytic cracking reaction in a catalytic unit. The initial distillation point of catalytic diesel is not lower than 150°C, and the final distillation point is not higher than 350°C.

3. The catalytic diesel combined treatment process according to claim 1, wherein: The aromatic content in catalytic diesel is higher than 50wt%, and the density at 20℃ is higher than 920kg / m 3 , nitrogen content is 200~1500 mg / kg.

4. The catalytic diesel combined treatment process according to claim 1, wherein: The aromatic content in catalytic diesel is 55wt% to 90wt%.

5. The catalytic diesel combined treatment process according to claim 1, wherein: The cutting point temperature of component A and component B is 180-250°C; the cutting point temperature of component B and component C is 260-330°C.

6. The catalytic diesel combined treatment process according to claim 1, wherein: The cutting point temperature of component A and component B is 180-220°C; the cutting point temperature of component B and component C is 290-310°C.

7. The catalytic diesel combined treatment process according to claim 1, wherein: The unconverted diesel obtained in step (3) is returned to the fixed bed hydrogenation reaction zone for treatment.

8. The catalytic diesel combined treatment process according to claim 1, wherein: The unconverted diesel obtained in step (3) is returned to the second catalyst bed of the fixed bed hydrogenation reaction zone for treatment.

9. The catalytic diesel combined treatment process according to claim 1, wherein: The first gas phase material obtained in step (2) and the second gas phase material obtained in step (3) enter the hydrogen separation and purification unit for treatment, and after the treatment, circulating hydrogen and light hydrocarbons are obtained.

10. The catalytic diesel combined treatment process according to claim 1, wherein: The reaction pressure of the fixed bed hydrogenation reaction zone is as follows: The reaction conditions of the first catalyst bed are: the reaction pressure is 5.0-20.0 MPa, the reaction temperature is 300-420°C, the hydrogen-oil volume ratio is 500-2000, and the liquid hourly volume space velocity is 0.1-5.0 h -1 ; Reaction conditions of the second catalyst bed: reaction pressure of 5.0-20.0 MPa, reaction temperature of 330-420°C, hydrogen-oil volume ratio of 500-2000, liquid hourly volume space velocity of 0.1-5.0 h -1 ; Reaction conditions of the third catalyst bed: reaction pressure of 5.0-20.0 MPa, reaction temperature of 300-420°C, hydrogen-to-oil volume ratio of 500-2000, liquid hourly volume space velocity of 0.1-5.0 h -1 .

11. The catalytic diesel combined treatment process according to claim 1, wherein: The reaction pressure of the fixed bed hydrogenation reaction zone is as follows: The reaction conditions of the first catalyst bed are: the reaction pressure is 6.0-10.0 MPa, the reaction temperature is 320-390°C, the hydrogen-oil volume ratio is 600-1500, and the liquid hourly volume space velocity is 0.5-2.0 h -1 ; Reaction conditions of the second catalyst bed: reaction pressure of 6.0-10.0 MPa, reaction temperature of 340-400°C, hydrogen-oil volume ratio of 600-1500, liquid hourly volume space velocity of 0.5-2.0 h -1 ; Reaction conditions of the third catalyst bed: reaction pressure of 6.0-10.0 MPa, reaction temperature of 350-420°C, hydrogen-oil volume ratio of 600-1500, liquid hourly volume space velocity of 0.5-2.0 h -1 .

12. The catalytic diesel combined treatment process according to claim 1, wherein: The reaction temperature of the first catalyst bed is 5-20°C lower than that of the second catalyst bed; the reaction temperature of the second catalyst bed is 5-20°C lower than that of the third catalyst bed.

13. The catalytic diesel combined treatment process according to claim 1, wherein: The reaction temperature of the first catalyst bed is 5-10°C lower than that of the second catalyst bed; the reaction temperature of the second catalyst bed is 5-10°C lower than that of the third catalyst bed.

14. The catalytic diesel combined treatment process according to claim 1, wherein: The process conditions of the ebullient bed hydrogenation reaction zone are: reaction temperature of 350-450°C, reaction pressure of 5.0-15.0 MPa, hydrogen-oil volume ratio of 500-2000, liquid hourly volume space velocity of 0.1-5.0 h -1 .

15. The catalytic diesel combined treatment process according to claim 1, wherein: The process conditions of the ebullient bed hydrogenation reaction zone are: reaction temperature of 380-440°C, reaction pressure of 6.0-10.0 MPa, hydrogen-oil volume ratio of 600-1500, liquid hourly volume space velocity of 0.2-2.0 h -1 .

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