A processing method for diesel raw oil

Abstract

The present invention discloses a method for simultaneously producing a raw material for low-carbon olefin cracking and a raw material for hydrocracking / catalytic cracking using diesel feedstock. By adopting the method of extraction first and then hydrogenation, compared with the method of hydrogenation first and then extraction, it is possible to avoid the excessive saturation of aromatics during the prior hydrogenation process. By using the method of extraction first, the extracted raw materials enter the hydrogenation reactor respectively, and the depth of hydrogenation can be controlled according to the needs of the product.

Description

Technical Field

[0001] The present invention belongs to the technical field of diesel processing, and particularly relates to a method for simultaneously producing a raw material for cracking low-carbon olefins and a raw material for hydrocracking / catalytic cracking using diesel raw oil as a raw material. Background Art

[0002] Low-carbon olefins such as ethylene and propylene are basic raw materials for chemical production. The steam cracking unit is the leading unit in petrochemical industry and has a major impact on the economic benefits of enterprises. At present, the main steam cracking raw materials are naphtha, hydrogenated tail oil, light hydrocarbon and diesel. In recent years, with the continuous increase in ethylene production capacity and the gradual shortage of crude oil resources, the contradiction between supply and demand of ethylene raw materials has gradually increased, and how to expand its raw material sources has become particularly important.

[0003] In recent years, the adjustment of industrial structure has caused great changes in the consumption structure of refined oil products, which is prominently manifested in the significant reduction of the diesel-to-gasoline consumption ratio. In the future, the growth of diesel consumption will be much slower than that of gasoline, and the differentiation trend of refined oil demand will be more obvious. The surplus of diesel resources will intensify in the future, and gasoline will turn into a tight balance. This has put forward new requirements for the adjustment of the refining product structure and the unit structure, and the task of reducing the production diesel-to-gasoline ratio is arduous. Therefore, how to reduce diesel has become a topic of discussion among major refining and chemical enterprises.

[0004] CN 103666550B discloses a method for increasing the production of low-carbon olefins and aromatics by steam cracking of coking gasoline. The raw material oil is pretreated by extracting aromatics with an ionic liquid solvent and extracting olefins with an ionic liquid solvent respectively to remove the aromatics and olefins therein, and a hydrocarbon stream with an aromatic content lower than 2 wt% and an olefin content lower than 4 wt% is obtained and enters the steam cracking process for cracking and separation; the crude aromatic hydrocarbon stream is sent to a hydrocracking gasoline aromatic extraction unit to separate aromatic products, and at the same time, the obtained saturated hydrocarbon-rich stream is returned and introduced into the cracking process together with the aromatic-poor petroleum hydrocarbon stream to react to produce low-carbon olefins. This method has opened up a suitable application path for coking gasoline, expanded the source of cracking raw materials, utilized the original cracking hydrocracking gasoline aromatic extraction system to recover non-aromatic components, and at the same time increased the production of low-carbon olefins and aromatics in the cracking process.

[0005] CN 1176293A discloses a preparation method for ethylene cracking, which is characterized in that light wax oil and coking diesel are used as raw materials and ethylene cracking stock is produced by high-pressure hydrofining. It has the advantages of simple production method, reduced operating costs, high total yield of ethylene, propylene and butadiene obtained by cracking, good quality; low yield of fuel oil obtained by cracking, less coking of the cracking furnace, and expanded source of ethylene cracking stock.

[0006] CN101475834B discloses a system and method for preparing high-quality gasoline and diesel oil by post-hydrogenation of component refinery hydrocarbons after recombination, which is characterized by including an extraction system, a distillation system and a hydrogenation unit. The upper part of the extraction system is connected to the distillation system through a pipeline; the lower part of the extraction system is connected to the hydrogenation unit through a pipeline, and the hydrogenation unit is connected to the pipeline at the upper part of the distillation system through a pipeline; the upper part of the distillation system directly extracts products through a pipeline, and the middle part of the distillation system is connected to another hydrogenation unit through a pipeline; the lower part of the distillation system directly extracts products through a pipeline. The system and method for preparing high-quality gasoline and diesel oil by post-hydrogenation of component refinery hydrocarbons after recombination of the present invention can not only remove olefins, but also remove mercaptans and diolefins; it has a small scale and low cost. Summary of the Invention

[0007] In the prior art, the methods for producing low-carbon olefins or aromatics from middle distillates have problems such as poor quality of feedstock oil. If the easily coking components in the feedstock are effectively removed, the overall process flow is complex, the energy consumption increases, and the economic benefits are even less obvious. The present invention takes advantage of the integrated refining and chemical enterprises, and through the aromatics complex unit, diesel hydrofining, and ethylene cracking unit, optimizes the feedstock and process structure of the existing units, can make full use of various feedstock resources, and is expected to solve the problems of the outlet of diesel and the shortage of ethylene feedstock. For the diesel fraction with relatively low sulfur and nitrogen content in the feedstock, the solvent extraction technology (aromatic extraction) can be used to effectively separate aromatics and alkanes, and then they enter the hydrogenation reactor respectively for appropriate reactions, which can not only obtain ideal ethylene feedstock, but also produce high-value-added aromatic products and high-octane gasoline blending components as by-products, alleviating the market supply and demand contradiction.

[0008] The present invention provides a method for simultaneously producing low-carbon olefin cracking feedstock and hydrocracking / catalytic cracking feedstock from diesel feedstock oil, including the following steps:

[0009] S1. The diesel feedstock oil first contacts with an extraction solvent for solvent extraction to obtain an extract rich in aromatics and a raffinate rich in alkanes;

[0010] S2. The raffinate is mixed with hydrogen and then enters the first hydrofining reactor for deep hydrofining reaction to obtain low-carbon olefin cracking feedstock;

[0011] S3. The extract rich in aromatics is separated by distillation to obtain an aromatic extract;

[0012] S4. The second hydrofining reactor is successively subjected to sulfidation treatment and activation treatment;

[0013] S5. Mix the aromatic extract oil obtained in step S3 with hydrogen and feed it into a second hydrotreating reactor that has undergone sulfidation treatment and activation treatment for hydrotreating reaction. The resulting second hydrotreating reaction product can be directly used as a feedstock for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components.

[0014] Among them, after the raffinate oil in step S2 is mixed with hydrogen, it enters the first hydrotreating reactor for deep hydrotreating reaction. The main purpose is to remove sulfur and nitrogen, saturate olefins, and deeply hydrogenate and saturate a small amount of aromatics to obtain a feedstock for low-carbon olefin cracking.

[0015] In step S5, sulfur and nitrogen are removed from the aromatic extract oil in the second hydrotreating reactor, olefins are saturated, and polycyclic aromatics are selectively hydrogenated and saturated to monocyclic aromatics. The resulting second hydrotreating reaction product can be directly used as a feedstock for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components.

[0016] According to an embodiment of the present invention, in step S1, the extraction solvent is an organic solvent with a vaporization temperature of not less than 380 °C under atmospheric pressure; preferably an ionic liquid.

[0017] Further preferably, the ionic liquid is an ionic liquid with a cation of alkyl-substituted imidazole or alkyl-substituted pyridine and an anion of tetrafluoroborate or hexafluorophosphate.

[0018] More preferably, the ionic liquid is one or more of 1-heptyl-4-methylpyridinium tetrafluoroborate, 1-heptyl-4-methylpyridinium hexafluorophosphate, 1-heptyl-3-methylimidazolium tetrafluoroborate, 1-heptyl-3-methylimidazolium hexafluoroborate, 1-hexyl-4-methylpyridinium tetrafluoroborate, and 1-hexyl-4-methylpyridinium hexafluorophosphate.

[0019] According to an embodiment of the present invention, in step S1, the mass ratio of the extraction solvent to the raw material is 0.5 - 5.0:1. Preferably, the mass ratio of the extraction solvent to the raw material oil is 0.5 - 2.0:1; the pressure of the extraction column is 0.1 - 0.6 MPa, and the extraction temperature is 15 - 85 °C. Preferably, the mass ratio of the extraction solvent to the raw material oil is 0.8 - 1.5:1, the pressure of the extraction column is 0.2 - 0.4 MPa, and the extraction temperature is 20 - 60 °C.

[0020] According to an embodiment of the present invention, in the step S1, it specifically includes the following steps: the feedstock oil enters the extraction column to be extracted with the extraction solvent, the raffinate oil with low aromatic hydrocarbons is obtained from the top of the column, and the rich solvent containing aromatic hydrocarbons and the solvent is obtained from the bottom of the column; the obtained raffinate oil with low aromatic hydrocarbons is washed with water or separated by adsorption to remove trace amounts of the solvent, and then the raffinate oil rich in alkanes is obtained; the rich solvent containing aromatic hydrocarbons is sent to the distillation column to recover the solvent, the extract oil rich in aromatic hydrocarbons is obtained from the bottom of the distillation column, and the solvent stream with an aromatic hydrocarbon content of less than 0.5 wt% is obtained from the top of the distillation column and returned to the top of the extraction column for recycling.

[0021] According to an embodiment of the present invention, the adsorbent for the process of adsorbing and removing the solvent from the raffinate oil is selected from activated carbon or molecular sieve.

[0022] According to an embodiment of the present invention, the hydrofining catalyst in the first hydrofining reaction zone and the second hydrofining reaction zone may be a supported catalyst containing Group VIB and / or Group VIII metals, and the carrier is an alumina and / or silica carrier; it may also be a non-supported catalyst containing Group VIB and / or Group VIII active metal components. The catalysts in the first hydrofining reaction zone and the second hydrofining reaction zone may be the same or different.

[0023] According to an embodiment of the present invention, the second hydrofining catalyst is a supported catalyst or a non-supported catalyst including active metals, and the active metals are at least one or several selected from molybdenum, tungsten, cobalt, and nickel; preferably, the active metals are cobalt and molybdenum.

[0024] According to an embodiment of the present invention, in the hydrofining reaction, a hydroprotection agent accounting for 5 - 20% of the total volume of the hydrofining catalyst is loaded at the top of the hydrofining catalyst bed. The hydroprotection agent includes 1.0 - 5.0 wt% nickel oxide, 5.5 - 10.0 wt% molybdenum oxide, and an alumina carrier with a bimodal pore size distribution.

[0025] In the hydrofining reaction, a hydroprotection agent accounting for 5 - 20% of the total volume of the hydrofining catalyst is loaded at the top of the hydrofining catalyst bed to protect the main catalyst, avoid rapid coking of the bed, and prevent the pressure drop of the catalyst bed from reaching the limit value too quickly when the olefin or metal content in the diesel is relatively high.

[0026] According to an embodiment of the present invention, the first hydrofining reaction conditions are: hydrogen partial pressure 0.1 - 12.0 MPa, reaction temperature 300 - 500 °C, liquid hourly space velocity 0.2 - 8.0 h -1 、hydrogen / oil volume ratio 100 - 2000 Nm 3 / m 3 ;

[0027] Preferably, the first hydrofining reaction conditions are as follows: hydrogen partial pressure of 4.0 - 10.0 MPa, reaction temperature of 320 - 450 °C, liquid hourly space velocity of 0.5 - 6.0 h -1 , hydrogen / oil volume ratio of 300 - 1500 Nm 3 / m 3 .

[0028] According to an embodiment of the present invention, the sulfur and nitrogen contents of the obtained first hydrofining product are ≤ 10 μg / g, the paraffin content is not less than 55 wt%, and the aromatic content is less than 10 wt%.

[0029] According to an embodiment of the present invention, in the step S3, the extract oil rich in aromatics is separated by distillation, and the extraction solvent is obtained at the bottom of the tower for recycling.

[0030] According to an embodiment of the present invention, in the step S4, the activation treatment includes the following specific steps: contacting the sulfided hydrofining catalyst with the activation raw material in an activation gas atmosphere and under activation reaction conditions for 24 - 120 hours.

[0031] According to an embodiment of the present invention, the activation gas includes hydrogen, hydrogen sulfide, and carbon monoxide. Based on the overall activation gas, the volume fraction of hydrogen is not less than 80%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is 0.3% - 2%.

[0032] According to an embodiment of the present invention, the steps for adjusting to the activation reaction after sulfidation are as follows: first, reduce the concentration of hydrogen sulfide gas in the reactor gas, then increase the concentration of carbon monoxide gas in the reactor gas, and finally adjust the gas in the reactor to the activation gas.

[0033] According to an embodiment of the present invention, in the step S5, it includes the following steps: after the activation of the second hydrofining reaction zone is completed, adjust to the normal reaction conditions, and switch the feed from the activation raw material to the aromatic extract oil; adjust the gas in the reaction system of the second hydrofining reaction zone to a hydrogen-rich gas, and the aromatic extract oil reacts with the catalyst under the hydrofining reaction conditions. In the hydrogen-rich gas, based on the overall hydrogen-rich gas, the volume fraction of hydrogen is at least 70%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is less than 0.05%.

[0034] According to an embodiment of the present invention, the specific steps for adjusting to the hydrofining reaction conditions after the activation is completed in the step S5 are as follows: first, reduce the concentration of carbon monoxide gas in the reactor gas, then reduce the concentration of hydrogen sulfide gas in the reactor gas, and finally adjust the gas in the reactor to a hydrogen-rich gas.

[0035] According to an embodiment of the present invention, the end of the sulfidation process means that after the temperature of the catalyst bed layer in the reactor reaches the predetermined sulfidation temperature, the volume fraction of hydrogen sulfide in the gas in the reactor is greater than 1.5% and does not decrease any more.

[0036] The inventors of the present invention have found through a large number of experimental studies that after the catalyst is sulfided, there are two active centers: a desulfurization active center and an aromatic hydrogenation saturation active center. By adding an activation reaction process for catalyst selectivity regulation between the sulfidation process and the normal hydrofining production process, the activity of one of the active centers can be effectively reduced, thereby improving the selectivity of the catalyst.

[0037] The catalyst selectivity regulation process is to bring the activation raw material into contact with the catalyst in the atmosphere of the activation gas under the activation reaction conditions. This process takes advantage of the characteristic of high aromatic hydrocarbon content in the catalytic raw material. In the reaction process, the raw material with a high aromatic hydrocarbon content is more likely to form coke. However, CO in the activation atmosphere will be preferentially adsorbed on the desulfurization active center of the catalyst, and its adsorption on the aromatic saturation active center is relatively weak. Therefore, the formed coke tends to cover the aromatic hydrogenation saturation active center of the catalyst, moderately reducing the aromatic hydrogenation saturation activity of the catalyst, while the desulfurization active center is effectively protected. When the activation atmosphere is removed, the desulfurization active center can be effectively released, so that the desulfurization activity of the catalyst is basically not lost or only slightly lost. The adsorption intensity of sulfur- and nitrogen-containing compounds with the same number of aromatic rings is higher than that of aromatic hydrocarbons with the same number of aromatic rings, and the adsorption intensity of polycyclic aromatic hydrocarbons is higher than that of monocyclic aromatic hydrocarbons. Therefore, moderately reducing the hydrogenation active center has little impact on desulfurization and denitrification and the hydrogenation saturation of polycyclic aromatic hydrocarbons, but can significantly inhibit the saturation of monocyclic aromatic hydrocarbons and improve the selectivity of monocyclic aromatic hydrocarbons.

[0038] Taking the Co-Mo catalyst as an example, if only in an atmosphere of H2 and CO, under harsh reaction conditions, Co in the sulfided CoMo catalyst is easily reduced to metallic Co, and metallic Co is easily reacted with CO to form [Co(CO4)] (cobalt carbonyl), resulting in permanent deactivation of the desulfurization activity of the catalyst. This is because under harsh conditions during the coking process or with raw materials that are prone to coking, the coking reaction will occur not only on the hydrogenation active center, but also on the acidic center on the surface of the carrier, resulting in excessive coking on the surface of the catalyst carrier and blocking the pores of the catalyst. Although the desulfurization active sites are protected in this way, the pores of the catalyst are blocked, and the reactant molecules cannot approach the desulfurization active sites inside the pores, which will also lead to a decrease in the desulfurization activity of the catalyst. Therefore, the activation gas described in the present invention includes hydrogen, hydrogen sulfide, and carbon monoxide. Based on the overall activation gas, it is preferably that the volume fraction of hydrogen is not less than 80%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is 0.3% - 2.0%.

[0039] According to an embodiment of the present invention, the distillation range of the activation raw material is 150 - 400 °C, and the total aromatic hydrocarbon content is 50 wt% - 90 wt%; preferably 55 - 80 wt%; preferably catalytic cracking diesel oil.

[0040] According to an embodiment of the present invention, the activation reaction conditions are as follows: hydrogen partial pressure 0.5 - 8.0 MPa, reaction temperature 300 - 450 °C, volume hourly space velocity 0.1 - 8.0 h -1 , hydrogen - to - oil volume ratio 50 - 1000 Nm 3 / m 3 , and the activation reaction time is 48 - 96 hours.

[0041] According to an embodiment of the present invention, the second hydrofining reaction conditions are: hydrogen partial pressure 1.0 - 10.0 MPa, reaction temperature 280 - 420 °C, liquid hourly space velocity 0.2 - 8.0 h -1 , hydrogen / oil volume ratio 50 - 1800 Nm 3 / m 3 ;

[0042] Preferably, the second hydrofining reaction conditions are: hydrogen partial pressure 2.0 - 8.0 MPa, reaction temperature 300 - 400 °C, liquid hourly space velocity 0.5 - 6.0 h -1 , hydrogen / oil volume ratio 200 - 1200 Nm 3 / m 3 .

[0043] The diesel fraction rich in aromatic hydrocarbons reacts with the catalyst under normal reaction conditions. The reactor effluent enters a high - pressure separator to separate the gas - phase and liquid - phase products. The gas - phase is recycled after desulfurization of hydrogen sulfide, and the liquid - phase stream enters a stripping column. The effluent from the bottom of the stripping column enters the product tank as the product.

[0044] According to an embodiment of the present invention, in the hydrogen - rich gas, based on the whole hydrogen - rich gas, the volume fraction of hydrogen is at least 85%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is less than 0.02%.

[0045] According to an embodiment of the present invention, the total aromatic hydrocarbon content of the obtained second hydrofining reaction product is not less than 70 wt%, and the monocyclic aromatic hydrocarbon content is not less than 50 wt%.

[0046] According to an embodiment of the present invention, the distillation range of the diesel feedstock oil is 150 - 400 °C, the paraffin hydrocarbon content ≥ 30 wt%, the total aromatic hydrocarbon content ≤ 60 wt%, the sulfur content ≤ 1.5%, and the nitrogen content ≤ 500 μg / g; preferably, the paraffin hydrocarbon content ≥ 35 wt%, the aromatic hydrocarbon content ≤ 45 wt%, the sulfur content ≤ 8000 μg / g, and the nitrogen content ≤ 300 μg / g.

[0047] According to an embodiment of the present invention, the diesel feedstock is selected from one or more of straight-run diesel, catalytic cracking diesel, coking diesel, diesel fraction of coal direct liquefaction oil, and diesel fraction of coal tar; preferably, the diesel feedstock is straight-run diesel.

[0048] The "polycyclic aromatic hydrocarbons" in the present invention refers to the sum of the mass fractions of bicyclic aromatic hydrocarbons and aromatic hydrocarbons with three or more rings in the mass spectrometry composition data obtained by mass spectrometry (analysis method SH / T-0606).

[0049] Compared with the prior art, the advantages of the method of the present invention are as follows:

[0050] 1. The present invention opens up an effective utilization path for diesel and expands the source of ethylene feedstock.

[0051] 2. The present invention uses diesel with relatively low sulfur and nitrogen contents as the raw material and adopts the method of extraction first and then hydrogenation. Compared with the method of hydrogenation first and then extraction, it can avoid the excessive saturation of aromatic hydrocarbons during the prior hydrogenation process. By adopting the method of extraction first, the extracted raw materials enter the hydrogenation reactors respectively, and the depth of hydrogenation can be controlled according to the needs of the product.

[0052] 3. Through the selective catalyst regulation technology in the second hydrogenation reactor, during the effective removal of sulfur and nitrogen, the deep hydrogenation saturation activity of aromatic hydrocarbons drops significantly, effectively improving the selectivity of monocyclic aromatic hydrocarbons, which can provide high-quality raw materials for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a process flow diagram of a preferred embodiment of the present invention;

[0054] 1 is the feedstock oil, 2 is the extraction column, 3 is the raffinate rich in alkanes, 4 is the extract rich in aromatic hydrocarbons, 5 is the solvent recovery column, 6 is the extraction solvent, 7 is the aromatic hydrocarbon extract, 8 is hydrogen, 9 is the first hydrofining reaction device, 10 is the second hydrofining reaction device, 11 is the first hydrofining product, and 12 is the second hydrofining product. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] The method provided by the present invention will be further described below in conjunction with the drawings and embodiments, but the present invention is not limited thereto.

[0056] Figure 1 is a process flow diagram of a preferred embodiment of the method for selectively desulfurizing and denitrifying diesel to produce low-carbon olefins according to the present invention. Many devices such as pumps, heat exchangers, compressors, high-pressure and low-pressure separators in the hydrogenation section, and water washing towers and dehydration towers in the extraction section are omitted in the figure, but this is well-known to those of ordinary skill in the art. For exampleFigure 1 As shown

[0057] The process of the method provided by the present invention is described in detail as follows:

[0058] Diesel raw material oil 1 enters the middle and lower part of the extraction column 2, and the extraction solvent 6 enters the upper part of the extraction column 2. They exchange and extract countercurrently. The raffinate rich in alkanes distilled from the top of the extraction column, after adsorbing the solvent with activated carbon or molecular sieve (not shown in the figure), is mixed with hydrogen 8 through a pipeline and then enters the first hydrofining reaction device 9 for desulfurization, denitrification, olefin saturation, and aromatic saturation reactions to obtain the first hydrofining product 11, whose sulfur and nitrogen contents are both < 10 μg / g, the alkane content is not less than 55% by mass, and the aromatic content is less than 10% by mass, and it can be used as high-quality ethylene cracking raw material. The extract rich in aromatics 4 distilled from the bottom of the extraction column 2 enters the solvent recovery column 5. After heating and distillation, the separated extraction solvent 6 is discharged from the bottom of the column and returned to the extraction column 2 for recycling. The aromatic extract 7 discharged from the top of the solvent recovery column 5 is mixed with hydrogen 8 through a pipeline and then enters the second hydrofining reaction device 10 for desulfurization, denitrification, and moderate saturation reaction of aromatics. The moderate saturation of aromatics is mainly the reaction of polycyclic aromatics hydrogenating to form monocyclic aromatics to obtain the second hydrofining product 12, whose total aromatic content is not less than 70% by mass, and the monocyclic aromatic content is not less than 50% by mass, and it can be directly used as raw material for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components. It can be used as raw material for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components.

[0059] For the selection of process conditions of the first hydrofining device, it is appropriate to control the sulfur and nitrogen contents in the hydrofined distillate oil at ≤ 10 μg / g, the alkane content at not less than 55% by mass, and the aromatic content at less than 10% by mass, so as to provide high-quality raw material for the ethylene cracking device; for the selection of process conditions of the second hydrofining device, it is appropriate to control the nitrogen content at less than 20 μg / g, the total aromatic content at not less than 70% by mass, and the monocyclic aromatic content at not less than 50% by mass, retaining the content of monocyclic aromatics, and providing high-quality raw material for the production of BTX components or high-octane gasoline in the hydrocracking or fluid catalytic cracking device.

[0060] The present invention does not particularly limit the type of the hydrofining catalyst, and those skilled in the art can select various hydrofining catalysts commonly used in the art. In order to make the product quality of the present invention better, the composition of the hydrofining catalyst in the method of the present invention preferably includes, based on the catalyst: nickel oxide is 1-10 wt%, the sum of the contents of molybdenum oxide and tungsten oxide is 10-50 wt%, the content calculated as phosphorus oxide is 0.5-8 wt%, and the balance is the carrier. Preferably, the carrier of the hydrofining catalyst contains silica-alumina. Based on the silica-alumina, the content of silica in the silica-alumina is 2-45 wt%, and the content of alumina is 55-98 wt%.

[0061] The hydrogenation protective agent and the hydrofining catalyst used in the examples can be prepared according to the prior art or obtained by commercial purchase. For example, it can be one or several of the hydrogenation protective agents with the commercial brand numbers RG-30A, RG-30B or RG-1 and the hydrofining catalysts with the commercial brand numbers RS-2000, RS-2100, RS-2200 and RS-3100 purchased from China Petroleum & Chemical Corporation. Using Ni-Mo type RS-3100 and Co-Mo type RS-2200 as diesel hydrofining catalysts A and B, 100 mL is filled in both the first hydrofining reactor and the second hydrofining reaction zone, which should not be understood as a limitation to the present invention by those skilled in the art.

[0062] In the examples, two typical diesel oils were selected as the feedstocks and denoted as feedstock A and feedstock B respectively. The main properties of the feedstocks are shown in Table 1.

[0063] Table 1 Properties of Feedstocks

[0064] Feedstock oil A B C <![CDATA[Density (20 °C), g / cm 3 > 0.84 0.83 0.97 Sulfur content, μg / g 6500 4500 6830 Nitrogen content, μg / g 210 121 1500 Hydrocarbon composition, wt% Paraffin 48 50 14.5 Total naphthenes 30 33 8.1 Total monocyclic aromatics 15.5 11.7 18.4 Total bicyclic aromatics 6 5 49.9 Tricyclic aromatics 0.5 0.3 9.1 Total aromatics 22 17 77.4

[0065] Example 1

[0066] The ionic liquid of 1-heptyl-4-methylpyridinium hexafluorophosphate was used for solvent extraction with feedstock A, and the extraction conditions are shown in Table 3. The raffinate rich in alkanes at the top of the extraction column was mixed with hydrogen after adsorbing the solvent by activated carbon and then entered the first hydrofining reactor. The process conditions of the first hydrofining reactor are shown in Table 2. The product obtained after the raffinate passed through the first hydrofining reactor can be directly used as high-quality ethylene cracking feedstock, and the specific properties are shown in Table 3.

[0067] The extract oil obtained at the bottom of the extraction column enters the solvent recovery column, and the extract oil rich in aromatics is discharged from the top of the solvent recovery column after heating and distillation. Before the raffinate oil rich in aromatics enters the second reactor, selective regulation needs to be carried out first after the sulfidation of the second hydrofining reaction zone is completed. During the selective regulation period, the gas in the reaction system is adjusted to the activation gas, and the raw material is the activation raw material C. The specific regulation parameters are shown in Table 2. After the selective regulation of the second hydrofining reaction zone is completed, the reaction conditions are adjusted to normal, the activation raw material is switched to the extract oil rich in aromatics, the gas in the reactor is switched to the hydrogen-rich gas, and the hydrofining reaction is carried out. The process conditions of the second hydrofining reactor are shown in Table 2. The product of the second hydrofining can be directly used as the raw material for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components, and the specific properties are shown in Table 4.

[0068] Examples 2 to 4

[0069] The tests of Examples 2 to 4 have the same method steps as those of Example 1, and they are all the process routes of first extracting and then hydrogenating diesel. The differences are the types of raw material oils, the extraction conditions, the process conditions of the first and second hydrofining reactors, and the changes in the selective regulation conditions of the second hydrofining reactor. The specific details are shown in Table 2.

[0070] Comparative Example 1

[0071] Using raw material oil A as the raw material, the diesel raw material enters the first hydrofining reaction zone for hydrogenation, and the hydrogenation product enters the extraction unit for extraction. The specific extraction conditions and hydrogenation process conditions are shown in Table 2.

[0072] Comparative Example 2

[0073] Using raw material oil A as the raw material, without passing through the solvent extraction unit, only through the first hydrofining unit, the first hydrofining product is directly used as ethylene feedstock, and the first hydrofining process conditions are the same as those of Example 1.

[0074] Comparative Example 3

[0075] Using raw material oil A as the raw material, only through the solvent extraction unit, without passing through the first and second hydrofining units, the raffinate oil rich in alkanes is obtained at the top of the extraction column, and the extract oil obtained at the bottom of the extraction column is distilled to obtain the aromatic extract oil, and the rest is the same as that of Example 1.

[0076] Comparative Example 4

[0077] Using raw material oil A as the raw material, with other conditions the same as those of Example 1, the difference is that the second hydrofining unit only undergoes sulfidation treatment and does not undergo activation treatment.

[0078] Comparative Example 5

[0079] Using feedstock A as the raw material, with other conditions being the same as in Example 1, the difference being that the activation feedstock is feedstock A.

[0080] Table 2 Specific process conditions

[0081]

[0082]

[0083] Table 3 Properties of the product in the first hydrofining reaction zone

[0084] Item Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Yield, % 82 84 85 86 82 100 80 82 82 Sulfur content, μg / g 5 6 6 4 5 65 4200 5 5 Nitrogen content, μg / g 2 2 2 2 2 22 60 2 2 Paraffin, wt% 56 57 59 59 53 47 50 56 56 Naphthenes, wt% 35 35 36 35 40 34 32 35 35 Monocyclic aromatics, wt% 7 7 4 4 5 16 16 7 7 Bicyclic aromatics, wt% 2 1 1 2 2 3 2 2 2 Tricyclic aromatics, wt% 0 0 0 0 0 0 0 0 0

[0085] Table 4 Properties of the product in the second hydrofining reaction zone

[0086]

[0087]

[0088] From the results in Table 3 to Table 4, it can be seen that when diesel is treated by the method of the present invention, the sulfur and nitrogen contents of the product after being treated in the first hydrofining reactor are both less than 10 μg / g, and the paraffin hydrocarbon content is significantly increased, which is significantly better than Comparative Examples 1 - 3; for the product after being treated in the second hydrofining reactor, its sulfur and nitrogen contents are significantly reduced, and the content of monocyclic aromatic hydrocarbons is significantly increased. Comparing with Comparative Examples 1 - 5, it can be known that the method of the present invention can also effectively reduce the deep hydrogenation saturation of monocyclic aromatic hydrocarbons and increase the content of monocyclic aromatic hydrocarbons.

[0089] Data source Examples and comparative examples ELN test record number: 119033-2022-1215-010

Claims

1. A method for simultaneously producing a raw material for low-carbon olefin cracking and a raw material for hydrocracking / catalytic cracking using diesel feedstock as the raw material, characterized in that, It includes the following steps: S1. The diesel raw material oil first contacts with an extraction solvent for solvent extraction to obtain an extract rich in aromatics and a raffinate rich in alkanes; S2. The raffinate is mixed with hydrogen and then enters the first hydrofining reactor for deep hydrofining reaction to obtain a raw material for light olefin cracking; S3. The extract rich in aromatics is separated by distillation to obtain an aromatic extract; S4. The second hydrofining reactor is successively subjected to sulfidation treatment and activation treatment; S5. The aromatic extract obtained through step S3 is mixed with hydrogen and enters the second hydrofining reactor that has been subjected to sulfidation treatment and activation treatment for hydrofining reaction. The obtained second hydrofining reaction product can be directly used as a raw material for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components; The activation treatment includes the following specific steps: The hydrofining catalyst after sulfidation is contacted with an activation raw material in an activation gas atmosphere and under activation reaction conditions for 24 - 120 hours; The activation gas includes hydrogen, hydrogen sulfide and carbon monoxide. Based on the overall activation gas, the volume fraction of hydrogen is not less than 80%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is 0.3% - 2%; The distillation range of the activation raw material is 150 - 400 °C, and the total aromatic content is 50 wt% - 90 wt%; The activation reaction conditions are as follows: hydrogen partial pressure 0.5 - 8.0 MPa, reaction temperature 300 - 450 °C, space velocity 0.1 - 8.0 h -1 , hydrogen-to-oil volume ratio 50 - 1000 Nm 3 / m 3 , and the activation reaction time is 48 - 96 hours.

2. The method according to claim 1, wherein In the step S1, the extraction solvent is an organic solvent with a vaporization temperature not lower than 380 °C under normal pressure.

3. The method according to claim 2, characterized in that, The organic solvent is an ionic liquid.

4. The method according to claim 3, characterized in that, The ionic liquid is an ionic liquid with a cation of alkyl-substituted imidazole or alkyl-substituted pyridine and an anion of tetrafluoroborate or hexafluorophosphate.

5. The method according to claim 3, characterized in that, The ionic liquid is one or more of 1-heptyl-4-methylpyridinium tetrafluoroborate, 1-heptyl-4-methylpyridinium hexafluorophosphate, 1-heptyl-3-methylimidazolium tetrafluoroborate, 1-heptyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-4-methylpyridinium tetrafluoroborate, 1-hexyl-4-methylpyridinium hexafluorophosphate.

6. The method according to claim 1, characterized in that, In the step S1, it specifically includes the following steps: The raw material oil enters the extraction tower to carry out extraction with the extraction solvent. The lean aromatic raffinate is obtained from the top of the tower, and the rich solvent rich in aromatics and solvent is obtained from the bottom of the tower; the obtained lean aromatic raffinate is washed with water or separated by adsorption to remove trace amounts of solvent to obtain a raffinate rich in alkanes; the rich solvent rich in aromatics and solvent is sent to a distillation tower to recover the solvent. The aromatic extract rich in aromatics is obtained from the bottom of the distillation tower, and a solvent stream with an aromatic content less than 0.5 wt% is obtained from the top of the distillation tower. The solvent stream is returned to the top of the extraction tower for recycling.

7. The method according to claim 6, characterized in that, In the step S1, the mass ratio of the extraction solvent to the raw material oil is 0.5 - 2.0:1, the pressure of the extraction tower is 0.1 - 0.6 MPa, and the extraction temperature is 15 - 85 °C.

8. The method according to claim 7, wherein The mass ratio of the extraction solvent to the raw material oil is 0.8 - 1.5:1, the pressure of the extraction tower is 0.2 - 0.4 MPa, and the extraction temperature is 20 - 60 °C.

9. The method according to claim 6, wherein The adsorbent for the process of adsorbing and removing the solvent from the raffinate is selected from activated carbon or molecular sieve.

10. The method according to claim 1, characterized in that, The second hydrofining catalyst in the second hydrofining reactor is a supported catalyst or a non-supported catalyst comprising active metals, and the active metals are at least one or several selected from molybdenum, tungsten, cobalt, and nickel.

11. The method according to claim 10, wherein The active metals are cobalt and molybdenum.

12. The method according to claim 1, wherein In the hydrofining reaction, a hydrofining protective agent accounting for 5-20% of the total volume of the hydrofining catalyst is loaded at the top of the hydrofining catalyst bed. The hydrofining protective agent comprises 1.0-5.0 wt% nickel oxide, 5.5-10.0 wt% molybdenum oxide, and an alumina support with a bimodal pore size distribution.

13. The method according to claim 1, wherein The first hydrofining reaction conditions are as follows: hydrogen partial pressure is 0.1 - 12.0 MPa, reaction temperature is 300 - 500 °C, liquid hourly space velocity is 0.2 - 8.0 h -1 , hydrogen / oil volume ratio is 100 - 2000 Nm 3 / m 3 .

14. The method according to claim 13, characterized in that, The first hydrofining reaction conditions are as follows: hydrogen partial pressure is 4.0 - 10.0 MPa, reaction temperature is 320 - 450 °C, liquid hourly space velocity is 0.5 - 6.0 h -1 , hydrogen / oil volume ratio is 300 - 1500 Nm 3 / m 3 .

15. The method according to claim 1, characterized in that, The sulfur and nitrogen contents of the obtained first hydrofining product are ≤10 μg / g, the paraffin hydrocarbon content is not less than 55 wt%, and the aromatic hydrocarbon content is less than 10 wt%.

16. The method according to claim 1, wherein In the step S5, the following steps are included: after the activation of the second hydrofining reactor is completed, it is adjusted to normal reaction conditions, and the feed is switched from the activation raw material to the aromatic extract oil; the gas in the second hydrofining reactor is adjusted to a hydrogen-rich gas, and the aromatic extract oil reacts with the catalyst under the hydrofining reaction conditions. In the hydrogen-rich gas, based on the whole hydrogen-rich gas, the volume fraction of hydrogen is at least 70%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is less than 0.05%.

17. The method according to claim 16, wherein In the step S5, the specific steps for adjusting to the hydrofining reaction conditions after the activation is completed are: first reducing the concentration of carbon monoxide gas in the reactor gas, then reducing the concentration of hydrogen sulfide gas in the reactor gas, and finally adjusting the gas in the reactor to a hydrogen-rich gas.

18. The method according to claim 1, wherein The total aromatic hydrocarbon content of the activation raw material is 55-80 wt%.

19. The method according to claim 1, wherein The second hydrofining reaction conditions are as follows: hydrogen partial pressure is 1.0 - 10.0 MPa, reaction temperature is 280 - 420 °C, liquid hourly space velocity is 0.2 - 8.0 h -1 , hydrogen / oil volume ratio is 50 - 1800 Nm 3 / m 3 .

20. The method according to claim 19, wherein The second hydrofining reaction conditions are as follows: hydrogen partial pressure is 2.0 - 8.0 MPa, reaction temperature is 300 - 400 °C, liquid hourly space velocity is 0.5 - 6.0 h -1 , hydrogen / oil volume ratio is 200 - 1200 Nm 3 / m 3 .

21. The method according to claim 16, characterized in that, In the hydrogen-rich gas, based on the whole hydrogen-rich gas, the volume fraction of hydrogen is at least 85%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is less than 0.02%.

22. The method according to claim 1, wherein The total aromatic hydrocarbon content of the obtained second hydrofining reaction product is not less than 70 wt%, and the monocyclic aromatic hydrocarbon content is not less than 50 wt%.

23. The method according to claim 1, wherein The distillation range of the diesel feedstock oil is 150-400 °C, the paraffin hydrocarbon content is ≥30 wt%, the total aromatic hydrocarbon content is ≤60 wt%, the sulfur content is ≤1.5%, and the nitrogen content is ≤500 μg / g.

24. The method according to claim 1, characterized in that, The paraffin hydrocarbon content of the diesel feedstock oil is ≥35 wt%, the aromatic hydrocarbon content is ≤45 wt%, the sulfur content is ≤8000 μg / g, and the nitrogen content is ≤300 μg / g.

25. The method according to claim 1, wherein The diesel feedstock oil is selected from one or several of straight-run diesel, catalytic cracking diesel, coking diesel, diesel fraction of direct coal liquefaction oil, and diesel fraction of coal tar.

26. The method according to claim 25, wherein The diesel feedstock oil is straight-run diesel.

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