A comprehensive utilization method of diesel oil

Abstract

The invention discloses a comprehensive utilization method of diesel raw oil. Using diesel as the raw material, high-quality Jet A-1 fuel and ethylene cracking stock can be produced simultaneously. Meanwhile, it can provide raw materials for hydrocracking or fluid catalytic cracking and co-produce high-octane gasoline or BTX light components, providing a new process technical route for refineries to reduce the diesel-to-gasoline ratio, optimize the product structure, and produce high-value products.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil product processing, and particularly relates to a comprehensive utilization method for simultaneously producing high-quality No. 3 jet fuel, ethylene cracking stock, and hydrocracking and fluid catalytic cracking feedstock from diesel raw oil as raw material. Background Art

[0002] In recent years, with the transformation and development of China's economy and the continuous improvement of people's living standards, the market demand for aviation kerosene (also known as jet fuel) has been increasing continuously. Corresponding to the increasing annual consumption of aviation kerosene, the domestic consumption of vehicle diesel has decreased relatively; in addition, due to the absence of consumption tax, compared with the production of diesel, the profit of producing aviation kerosene is higher. Therefore, according to market needs, some refineries have the actual need to compress diesel production and increase the yield of aviation kerosene.

[0003] Domestic and foreign research institutions have studied the relationship between the properties of raw materials and the yield of light olefins in the steam cracking process, and found that the higher the content of n-alkanes and the lower the content of aromatics in the cracking raw material, the more beneficial it is to improve the olefin yield and reduce the coking of equipment, and it is more suitable as a cracking raw material.

[0004] In China, straight-run diesel accounts for more than half of the blending components in the diesel pool. Among them, the straight-run diesel has a relatively high content of paraffins, and the proportion of n-alkanes is relatively large, which is a potential raw material for cracking. However, if some of the aromatics contained in diesel directly enter the ethylene cracking unit, it will cause an increase in the coking amount of the cracking furnace, because only the side chains of aromatics in the cracking raw material can be cracked to produce target products such as ethylene or propylene, and the aromatic ring itself is difficult to open due to the high bond energy of the C-C conjugate bond reaching 611 kJ / mol. At 500-900 °C, it will generate coking precursors, and under the catalytic action of the furnace tube material nickel alloy steel, it can dehydrogenate and polycondense to produce asphaltene with poor fluidity at 300-400 °C, seriously affecting production. Therefore, if diesel is to be used as an ethylene raw material, it is necessary to remove the aromatics in it. Hydrogenation reaction and conventional solvent extraction are commonly used methods to remove aromatics from oil products.

[0005] CN 109705900 A discloses a method for maximizing the production of jet fuel and chemical raw materials from diesel fractions. The straight-run diesel reacts with a hydrocracking catalyst in a hydrocracking reaction zone in the presence of hydrogen. The reaction products are separated and fractionated to obtain light naphtha products, heavy naphtha products, kerosene fractions, and unconverted diesel fractions. The unconverted diesel fractions are recycled to the hydrocracking reaction zone. The kerosene fractions obtained by this method can be used as high-quality No. 3 jet fuel, the heavy naphtha products can be used as high-quality reforming raw materials, and the light naphtha products can be used as high-quality ethylene cracking stock. This method can reduce the diesel-to-gasoline ratio in refineries and increase the production of chemical materials.

[0006] CN1022844C discloses a method for producing high-value products using wax oil, which is characterized by adopting solvent extraction in an optimized combination with other technologies to process low-value, difficult-to-process inferior wax oil into high-quality, high-value steam cracking ethylene raw materials, catalytic cracking raw materials, rubber filler oil, asphalt modifier, etc. This technology has low production costs, no environmental pollution, and high economic benefits. It is a brand-new heavy oil processing route.

[0007] The above-mentioned method of producing aviation kerosene, low-carbon olefins or aromatics from distillate oil has harsh process conditions, high energy consumption, and poor raw oil properties. If the coking components in the raw materials are effectively removed, the overall process flow is complicated and the economic benefits are even less obvious. If the advantages of refining and chemical integration enterprises can be utilized, the raw materials and process structures of existing devices can be optimized through hydrofining units, aromatics combined units, ethylene cracking units and catalytic cracking units, and various raw material resources can be fully utilized, which is expected to solve the problem of diesel fuel outlet. This method, on the one hand, uses a fractionation system to first cut the kerosene fraction and diesel fraction in the diesel raw material, expanding the source of raw materials for the aviation kerosene hydrofining unit; on the other hand, solvent extraction technology (aromatics extraction) can achieve the enrichment of alkane components, and then combine hydrofining technology to effectively remove sulfur and nitrogen impurities, which can greatly improve the quality of ethylene feed. At the same time, the enriched aromatic components can provide raw materials for hydrocracking or catalytic cracking units after selective hydrofining to produce high-octane gasoline or BTX light components. This method provides an economically feasible technical route for the outlet of diesel, which can effectively alleviate the contradiction between market supply and demand. Summary of the invention

[0008] In order to overcome the above technical problems, the present invention provides a method for comprehensive utilization of diesel fuel oil, characterized in that it comprises the following steps:

[0009] S0, the raw oil first enters the fractionation system to separate the kerosene fraction and the diesel fraction, and the kerosene fraction enters the aviation kerosene hydrorefining reaction zone to prepare No. 3 jet fuel;

[0010] S1, the diesel fraction is contacted with an extraction solvent for solvent extraction to obtain an extracted oil rich in aromatics and a raffinate oil rich in alkanes;

[0011] S2, the raffinate oil is mixed with hydrogen and then enters the first hydrotreating reactor for deep hydrotreating reaction to obtain a light olefin cracking feedstock;

[0012] S3, separating the extracted oil rich in aromatics by distillation to obtain aromatic extracted oil;

[0013] S4, sequentially performing sulfidation treatment and activation treatment on the second hydrotreating reactor;

[0014] S5. Mix the aromatic extract oil obtained in step S3 with hydrogen and introduce it into the second hydrotreating reactor that has undergone sulfidation treatment and activation treatment. In the second hydrotreating reactor, the sulfur and nitrogen in the aromatic extract oil are removed, the olefins are saturated, and the polycyclic aromatic hydrocarbons are selectively hydrogenated and saturated to monocyclic aromatic hydrocarbons. The product of the second hydrotreating reaction can be directly used as a feedstock for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components.

[0015] In step S0, the cutting point between the kerosene fraction and the diesel fraction in the fractionation system is 230 - 300 °C.

[0016] Among them, in step S0, the purpose of the kerosene fraction entering the jet fuel hydrotreating reaction zone is to further remove the impurities therein and carry out aromatic saturation.

[0017] In step S2, the raffinate is mixed with hydrogen and then introduced into the first hydrotreating reactor for deep hydrotreating reaction. The main purposes are to remove sulfur and nitrogen, saturate olefins, and deeply hydrogenate and saturate a small amount of aromatics.

[0018] In step S5, the sulfur and nitrogen in the aromatic extract oil are removed, the olefins are saturated, and the polycyclic aromatic hydrocarbons are selectively hydrogenated and saturated to monocyclic aromatic hydrocarbons in the second hydrotreating reactor.

[0019] The obtained first hydrotreating product has a sulfur content and a nitrogen content both ≤ 10 μg / g, an alkane content not less than 55 wt%, and an aromatic content less than 10 wt%, and can be used as a high-quality feedstock for ethylene cracking.

[0020] The product obtained from the second hydrotreating reactor has a total aromatic content of not less than 70 wt% and a monocyclic aromatic content of not less than 50 wt%, and can be directly used as a feedstock for hydrocracking or fluid catalytic cracking to produce high-octane gasoline or BTX light components.

[0021] 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 normal pressure; preferably an ionic liquid.

[0022] 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.

[0023] 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 hexafluorophosphate, 1-hexyl-4-methylpyridinium tetrafluoroborate, and 1-hexyl-4-methylpyridinium hexafluorophosphate.

[0024] According to an embodiment of the present invention, in the step S1, the mass ratio of the extraction solvent to the feedstock oil is 0.5 to 2.0:1, the pressure of the extraction column is 0.1 to 0.6 MPa, and the extraction temperature is 15 to 85 °C; preferably, the mass ratio of the extraction solvent to the feedstock oil is 0.8 to 1.5:1, the pressure of the extraction column is 0.2 to 0.4 MPa, and the extraction temperature is 20 to 60 °C.

[0025] 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 solvents to obtain the raffinate oil rich in alkanes; 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.

[0026] According to an embodiment of the present invention, the adsorbent for the process of adsorbing and removing the solvent from the raffinate oil is activated carbon or molecular sieve.

[0027] According to an embodiment of the present invention, the hydrofining catalyst in the first hydrofining reaction zone and the second hydrofining reaction zone can be a supported catalyst containing metals of Group VIB and / or Group VIII, and the carrier is an alumina and / or silica carrier; it can also be a non-supported catalyst containing active metal components of Group VIB and / or Group VIII. The catalysts in the first hydrofining reaction zone and the second hydrofining reaction zone can be the same or different.

[0028] 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.

[0029] According to an embodiment of the present invention, in the hydrofining reaction, a hydroprotection agent accounting for 5 to 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 to 5.0 wt% nickel oxide, 5.5 to 10.0 wt% molybdenum oxide, and an alumina carrier with a bimodal pore size distribution.

[0030] In the hydrofining reaction, a hydroprotection agent accounting for 5 to 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 high.

[0031] According to an embodiment of the present invention, 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 . The preferred operating conditions are: 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 .

[0032] 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 column for recycling.

[0033] 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 an activation raw material in an activation gas atmosphere and under activation reaction conditions for 24 - 120 hours.

[0034] According to an embodiment of the present invention, the activation gas includes hydrogen, hydrogen sulfide and carbon monoxide. Based on the whole 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%.

[0035] According to an embodiment of the present invention, the steps of adjusting to the activation reaction after sulfidation are as follows: first reducing the concentration of hydrogen sulfide gas in the reactor gas, then increasing the concentration of carbon monoxide gas in the reactor gas, and finally adjusting the gas in the reactor to the activation gas.

[0036] According to an embodiment of the present invention, in the step S5, the following steps are included: after the activation of the second hydrofining reaction zone is completed, adjusting to normal reaction conditions, switching the feedstock oil from the activation raw material to the aromatic extract oil; adjusting the gas in the reaction system of the second hydrofining reaction zone to a hydrogen-rich gas, and reacting the aromatic extract oil with the catalyst under normal 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%.

[0037] According to an embodiment of the present invention, the end of the sulfidation process means that after the catalyst bed temperature in the reactor reaches the predetermined sulfidation temperature, the volume fraction of hydrogen sulfide in the reactor gas is greater than 1.5% and does not decrease any more.

[0038] 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%.

[0039] According to an embodiment of the present invention, the activation reaction conditions are as follows: hydrogen partial pressure of 0.5 - 8.0 MPa, reaction temperature of 300 - 450 °C, volumetric space velocity of 0.1 - 8.0 h -1 , hydrogen - to - oil volume ratio of 50 - 1000 Nm 3 / m 3 , and the activation reaction time is 48 - 96 hours.

[0040] According to an embodiment of the present invention, the second hydro - refining reaction conditions are as follows: hydrogen partial pressure of 1.0 - 10.0 MPa, reaction temperature of 280 - 420 °C, liquid hourly space velocity of 0.2 - 8.0 h -1 , hydrogen / oil volume ratio of 50 - 1800 Nm 3 / m 3 ; preferably, the operating conditions are: hydrogen partial pressure of 2.0 - 8.0 MPa, reaction temperature of 300 - 400 °C, liquid hourly space velocity of 0.5 - 6.0 h -1 , hydrogen / oil volume ratio of 200 - 1200 Nm 3 / m 3 .

[0041] 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 70%, and the sum of the volume fractions of hydrogen sulfide and carbon monoxide is less than 0.05%; preferably, 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%.

[0042] According to an embodiment of the present invention, the total aromatic hydrocarbon content of the obtained second hydro - refining reaction product is not less than 70 wt%, and the content of monocyclic aromatic hydrocarbons is not less than 50 wt%.

[0043] According to an embodiment of the present invention, the distillation range of the diesel raw material 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; preferably, the paraffin hydrocarbon content 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.

[0044] According to an embodiment of the present invention, the diesel raw material oil 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 raw material oil is straight - run diesel.

[0045] The "polycyclic aromatic hydrocarbons" referred to in the present invention refer 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).

[0046] Since the oxides of metals in Group VIB and / or Group VIII such as cobalt, nickel, molybdenum, and tungsten do not have hydrogenation activity and only have relatively high hydrogenation activity when present in a sulfide state, it is necessary to sulfide the fresh catalyst and the regenerated catalyst to convert them from the oxidized state to the sulfide state. The sulfidation process described above can be wet sulfidation or dry sulfidation. The sulfidation rate and degree of the catalyst are closely related to the sulfidation temperature. At each temperature, there is a limiting value for the sulfidation degree of the catalyst. After reaching this value, even if the time is extended, the sulfur content on the catalyst will not increase significantly. 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 further.

[0047] 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 hydrocarbon hydrogenation saturation active center. By adding an activation reaction process for catalyst selectivity regulation between the sulfidation process and the normal hydrofining production process in the present invention, the activity of one of the active centers can be effectively reduced, thereby improving the selectivity of the catalyst.

[0048] The catalyst selectivity regulation process described above 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 characteristics of the high aromatic hydrocarbon content in the catalytic raw material. During 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 hydrocarbon saturation active center is relatively weak. Therefore, the formed coke tends to cover the aromatic hydrocarbon hydrogenation saturation active center of the catalyst, moderately reducing the aromatic hydrocarbon hydrogenation saturation activity of the catalyst, while the desulfurization active center is effectively protected. When the activation atmosphere is withdrawn, 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 strength 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 strength of polycyclic aromatic hydrocarbons is higher than that of monocyclic aromatic hydrocarbons. Therefore, moderately reducing the hydrogenation active center has little effect on desulfurization, 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.

[0049] Taking the Co-Mo catalyst as an example, if only in an atmosphere of H2 and CO, under harsh reaction conditions, the Co in the sulfided CoMo catalyst is easily reduced to metallic Co, and the metallic Co is prone to react with CO to form [Co(CO4)] (cobalt carbonyl), resulting in permanent deactivation of the catalyst's desulfurization activity. This is because under harsh conditions during the carbon deposition process or with raw materials that are prone to carbon deposition, the carbon deposition reaction occurs not only at the hydrogenation active sites but also at the acidic sites on the surface of the support, leading to excessive carbon deposition on the surface of the catalyst support and clogging the pores of the catalyst. Although the desulfurization active sites are protected in this way, the catalyst pores are blocked, and the reactant molecules cannot approach the desulfurization active sites inside the pores, which also causes 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%.

[0050] The distillation range of the activation raw material is 150 - 400 °C, and among them, the total aromatic hydrocarbon content is 40 mass% - 90 mass%; it is preferably catalytic cracking diesel. The described activation reaction conditions are: at a hydrogen partial pressure of 0.5 - 8.0 MPa, a reaction temperature of 300 - 450 °C, a volume space velocity of 0.1 - 8.0 h-1, and a hydrogen-oil volume ratio of 50 - 1000 Nm 3 / m 3 , and the activation reaction time is 48 - 96 hours.

[0051] After the catalyst selectivity regulation process is completed, it is adjusted to normal reaction conditions, and the activation raw material is switched to diesel raw material, and the gas in the reaction system is adjusted to a hydrogen-rich gas. In the hydrogen-rich gas, based on the overall hydrogen-rich gas, it is preferably that 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%. The diesel fraction rich in aromatics reacts with the catalyst under normal reaction conditions, and the reactor effluent enters the 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 the stripping column. The effluent at the bottom of the stripping column enters the product tank as the product.

[0052] According to an embodiment of the present invention, the reaction temperature of the activation reaction described in step (3) is equivalent to the normal reaction temperature.

[0053] In the method for producing a diesel raw material for low-carbon olefins according to the present invention, it is characterized in that the extraction solvent described in step (1) is preferably an ionic liquid.

[0054] In the method for producing raw materials for low-carbon olefins from diesel oil according to the present invention, it is characterized in that, in step (1), the mass ratio of the extraction solvent to the raw material is 0.5 to 5.0:1, the pressure of the extraction column is 0.1 to 0.6 MPa, and the extraction temperature is 15 to 85 °C; the preferred operating conditions are: the mass ratio of the extraction solvent to the raw material is 0.8 to 4.0:1, the pressure of the extraction column is 0.2 to 0.4 MPa, and the extraction temperature is 20 to 70 °C.

[0055] In the method for producing raw materials for low-carbon olefins from diesel oil according to the present invention, it is characterized in that the distillation range of the diesel raw material is 150 - 400 °C, the paraffin content is ≥ 30% by mass, the total aromatic content is ≤ 60% by mass, the sulfur content is ≤ 1.5%, and the nitrogen content is ≤ 500 μg / g; preferably, the paraffin content is ≥ 35% by mass, the aromatic content is ≤ 45% by mass, the sulfur content is ≤ 8000 μg / g, and the nitrogen content is ≤ 300 μg / g.

[0056] In the method for producing raw materials for low-carbon olefins from diesel oil according to the present invention, it is characterized in that, in step (1), the diesel raw material is introduced from the bottom of the aromatic extraction column, so that it contacts countercurrently with the extraction solvent flowing from top to bottom in the extraction column, the raffinate oil with low aromatic content is obtained from the top of the column, and the rich solvent rich in aromatic hydrocarbons and solvent is obtained from the bottom of the column; the obtained raffinate oil with low aromatic content is washed with water or separated by adsorption to remove trace solvents to obtain ethylene cracking raw materials; the rich solvent rich in aromatic hydrocarbons is sent to a rectification column to recover the solvent, a logistics rich in aromatic hydrocarbons is obtained from the top of the rectification column, and a solvent logistics with an aromatic content of less than 0.5% by mass is obtained from the bottom of the stripping column and returned to the top of the aromatic extraction column in step (1) for recycling.

[0057] In the method for producing raw materials for low-carbon olefins from diesel oil according to the present invention, it is characterized in that the adsorbents for the process of adsorbing and removing solvents from the raffinate oil are activated carbon and molecular sieve.

[0058] Compared with the prior art, the advantages of the method of the present invention are:

[0059] 1. Using diesel oil as the raw material, the present invention can simultaneously produce high-quality jet fuel No. 3 and ethylene cracking feedstock, and at the same time can provide raw materials for hydrocracking or fluid catalytic cracking to co-produce high-octane gasoline or BTX light components, providing a new process technical route for refineries to reduce the diesel-gasoline ratio, optimize the product structure, and produce high-value products.

[0060] 2. The present invention uses diesel with relatively low sulfur and nitrogen contents as the raw material. First, the kerosene fraction therein is separated, then extraction is carried out to separate the alkane component and the aromatic hydrocarbon component, and finally hydrogenation is carried out separately. During the processing of the separated diesel fraction, the method of extraction first and then hydrogenation is adopted. 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.

[0061] 3. In the second hydrogenation reactor, through the catalyst selectivity control technology, during the effective removal of sulfur and nitrogen, the deep hydrogenation saturation activity of aromatic hydrocarbons decreases significantly, effectively improving the selectivity of monocyclic aromatic hydrocarbons, which can provide high-quality raw materials for hydrocracking or catalytic cracking and produce high-octane gasoline or BTX light components. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] APPENDIX Figure 1 is a process flow diagram of a preferred embodiment of the present invention:

[0063] 1 is the raw oil, 2 is the fractionation system, 3 is the kerosene fraction, 4 is the diesel fraction, 5 is hydrogen, 6 is the aviation kerosene hydrofining reaction device, 7 is the aviation kerosene hydrofining product, 8 is the extraction tower, 9 is the raffinate rich in alkanes, 10 is the extract rich in aromatic hydrocarbons, 11 is the first diesel hydrofining reaction device, 12 is the first hydrofining product, 13 is the solvent recovery tower, 14 is the extraction solvent, 15 is the aromatic hydrocarbon extract, 16 is the second diesel hydrofining reaction device, 17 is the second hydrofining product. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] 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.

[0065] Figure 1 is a process flow diagram of a preferred embodiment of a comprehensive utilization method of a diesel oil of the present invention. Many devices are omitted in the figure, such as pumps, heat exchangers, compressors, high-pressure separators and low-pressure separators in the hydrogenation section, water washing towers and dehydration towers in the extraction section, etc., but this is well known to those of ordinary skill in the art. As Figure 1 shown,

[0066] The process of the method provided by the present invention is described in detail as follows:

[0067] Diesel raw material oil 1 enters the fractionation system 2, separating out the kerosene fraction 3 and the diesel fraction 4. The kerosene fraction and hydrogen 5 are mixed through a pipeline and then enter the aviation kerosene hydrofining reaction unit 6 to remove impurities therein and undergo aromatic saturation to obtain the aviation kerosene hydrofining product 7, which can be directly used as high-quality No. 3 jet fuel. The diesel fraction 4 enters the middle and lower part of the extraction tower 8, and the extraction solvent 14 enters the upper part of the extraction tower 8 for countercurrent exchange extraction. The raffinate rich in alkanes distilled from the top of the extraction tower, after adsorbing the solvent with activated carbon or molecular sieve (not shown in the figure), is mixed with hydrogen 5 through a pipeline and then enters the first hydrofining reaction unit 11 to carry out desulfurization, denitrification, olefin saturation and aromatic saturation reactions, obtaining the first hydrofining product 12, whose sulfur and nitrogen contents are both <10 μg / g, the paraffin hydrocarbon content is not less than 55% by mass, and the aromatic hydrocarbon content is less than 10% by mass, which can be used as high-quality ethylene cracking raw material. The extract rich in aromatic hydrocarbons 10 distilled from the bottom of the extraction tower 8 enters the solvent recovery tower 13. After heating and distillation, the separated extraction solvent 14 is discharged from the bottom of the tower and returned to the extraction tower 8 for recycling. The aromatic extract 15 discharged from the top of the solvent recovery tower 13 is mixed with hydrogen 5 through a pipeline and then enters the second hydrofining reaction unit 16 to carry out desulfurization, denitrification, and moderate saturation reaction of aromatic hydrocarbons, obtaining the second hydrofining product 17, whose total aromatic hydrocarbon content is not less than 70% by mass, and the monocyclic aromatic hydrocarbon content is not less than 50% by mass, which can be directly used as raw material for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components.

[0068] For the selection of process conditions of the first hydrofining unit, it is appropriate to control the sulfur and nitrogen contents in the hydrofined distillate oil to ≤10 μg / g, the paraffin hydrocarbon content to be not less than 55% by mass, and the aromatic hydrocarbon content to be less than 10% by mass, so as to provide high-quality raw materials for the ethylene cracking unit; for the selection of process conditions of the second hydrofining unit, it is appropriate that the nitrogen content is less than 20 μg / g, the total aromatic hydrocarbon content is not less than 70% by mass, and the monocyclic aromatic hydrocarbon content is not less than 50% by mass, retaining the content of monocyclic aromatic hydrocarbons, and providing high-quality raw materials for the production of BTX components or high-octane gasoline in the hydrocracking or catalytic cracking unit.

[0069] The present invention does not particularly limit the type of the hydrofining catalyst, and those skilled in the art can select according to 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 according to the present invention preferably includes, based on the catalyst: nickel oxide is 1 - 10% by weight, the sum of the contents of molybdenum oxide and tungsten oxide is 10 - 50% by weight, the content calculated as phosphorus oxide is 0.5 - 8% by weight, 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% by weight, and the content of alumina is 55 - 98% by weight.

[0070] The hydrogenation protecting agent and the jet fuel and diesel hydrogenation refining catalysts used in the examples can be prepared according to the prior art or obtained through commercial purchase. For example, the hydrogenation protecting agent can be those with commercial brands RG-30A, RG-30B or RG-1 purchased from China Petroleum & Chemical Corporation, one or more of the jet fuel hydrogenation catalysts with commercial brands RSS-1A and RSS-2, and one or more of the diesel hydrogenation refining catalysts with commercial brands RS-2000, RS-2100, RS-2200 and RS-3100. In the examples of the present invention, RSS-2 is exemplarily used as the jet fuel hydrogenation catalyst, and Ni-Mo type RS-3100 and Co-Mo type RS-2200 are used as diesel hydrogenation refining catalysts A and B. The jet fuel hydrogenation reactor, the first diesel hydrogenation refining reactor and the second diesel hydrogenation refining reaction zone are all filled with 100 mL of catalyst, which should not be construed as a limitation to the present invention by those skilled in the art.

[0071] In the examples, two typical diesel oils are selected as the feedstock oils and are respectively denoted as feedstock oil A and feedstock oil B. The main properties of the feedstock oils are shown in Table 1.

[0072] Table 1 Properties of Feedstock Oils

[0073] 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 monoaromatic hydrocarbons 15.5 11.7 18.4 Total diaromatic hydrocarbons 6 5 49.9 Triaromatic hydrocarbons 0.5 0.3 9.1 Total aromatic hydrocarbons 22 17 77.4

[0074] Example 1

[0075] Using straight-run diesel A as the feedstock oil, the feedstock oil first enters the separation system and the fractionation system to cut out the kerosene fraction and the diesel fraction. The kerosene fraction enters the fixed-bed jet fuel hydrogenation refining unit, the reaction temperature is 250 °C, the hydrogen partial pressure is 2.0 MPa, the volume space velocity is 4.0 h -1 , and the hydrogen / oil volume ratio is 100:1. The properties of the kerosene fraction are shown in Table 3.

[0076] The ionic liquid of 1-heptyl-3-methylimidazolium tetrafluoroborate is used for solvent extraction with the diesel fraction, and the extraction conditions are shown in Table 3. The raffinate oil rich in alkanes at the top of the extraction column is adsorbed with the solvent by activated carbon and then mixed with hydrogen and enters the first hydrogenation refining reactor. The process conditions of the first hydrogenation refining reactor are shown in Table 2. The product obtained after the raffinate oil passes through the first hydrogenation refining reactor can be directly used as high-quality ethylene cracking feedstock, and the specific properties are shown in Table 4.

[0077] The extract oil obtained at the bottom of the extraction column enters the solvent recovery column, and after heating and distillation, the extract oil rich in aromatics is discharged from the top of the solvent recovery column. 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, and the gas in the reactor is switched to the hydrogen-rich gas to carry out the hydrofining reaction. 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 5.

[0078] Examples 2 - 4

[0079] The tests of Examples 2 to 4 are the same as the method steps of Example 1, and they are all the process routes of first extraction and then hydrogenation for diesel. The differences are the types of raw materials, extraction conditions, process conditions of the first and second hydrofining reactors, and changes in the selective regulation conditions of the second hydrofining reactor, as shown in Table 2 specifically.

[0080] Comparative Example 1

[0081] Using raw material oil A as the raw material, first cut and separate the kerosene fraction, and the kerosene fraction enters the fixed-bed jet fuel hydrofining unit for hydrofining; the diesel fraction enters the first hydrofining reaction zone for hydrogenation, and the hydrogenation product enters the extraction unit for extraction again. The specific extraction conditions and hydrogenation process conditions are shown in Table 2.

[0082] Comparative Example 2

[0083] 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 in Example 1.

[0084] Comparative Example 3

[0085] 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 in Example 1.

[0086] Comparative Example 4

[0087] Using raw material oil A as the raw material, other conditions are the same as those in Example 1, and the difference is that the second hydrofining unit only undergoes sulfidation treatment and does not undergo activation treatment.

[0088] Comparative Example 5

[0089] Using feedstock A as the raw material, with other conditions being the same as in Example 1, the difference being that the activated feedstock uses feedstock A

[0090] Calculated based on diesel as the raw material, the properties and yields of different products are shown in Tables 3 to 5.

[0091] Table 2

[0092]

[0093]

[0094] Table 3

[0095]

[0096]

[0097] Table 4

[0098] 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, % 73 72 72 74 73 100 80 73 73 Sulfur content, μg / g 4 5 6 3 5 65 4200 4 4 Nitrogen content, μg / g 1 1 1 1 2 22 60 1 1 Paraffin, wt% 57 58 60 60 53 47 50 57 57 Naphthenes, wt% 36 34 35 35 40 34 32 36 36 Monoaromatic hydrocarbons, wt% 5 6 4 3 5 16 16 5 5 Diaromatic hydrocarbons, wt% 2 1 1 2 2 3 2 2 2 Triaromatic hydrocarbons, wt% 0 0 0 0 0 0 0 0 0

[0099] Table 5

[0100] Item Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 3 Comparative Example 4 Comparative Example 5 Yield, % 14 14 12 11 14 20 14 14 Sulfur content, μg / g 6 8 9 7 7 9200 5 5 Nitrogen content, μg / g 2 2 5 4 3 600 1 1 Paraffin, wt% 8 8 10 11 8 12 13 13 Naphthenes, wt% 15 16 20 21 25 15 23 22 Monoaromatic hydrocarbons, wt% 69 68 63 62 52 49 57 58 Diaromatic hydrocarbons, wt% 8 8 7 6 15 22 7 7 Triaromatic hydrocarbons, wt% 0 0 0 0 0 2 0 0

[0101] As can be seen from the results in Tables 3 to 5, when the diesel fraction is processed according to the method of the present invention, the hydrotreated product of jet fuel can be used as high-quality No. 3 jet fuel. After being processed by the first hydrotreating reactor of diesel, the sulfur and nitrogen contents of the product are both less than 10 μg / g, the alkane content is not less than 55% by mass, and the aromatic content is less than 10% by mass, which can be used as high-quality ethylene feedstock; after being processed by the second hydrotreating reactor of diesel, the sulfur and nitrogen contents of the product are significantly reduced, among which the nitrogen content is less than 20 μg / g, the total aromatic content is not less than 70% by mass, and the content of monocyclic aromatics is not less than 50% by mass, which can be directly used as the feedstock for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components.

[0102]

[0103]

Claims

1. A comprehensive utilization method of diesel raw material oil, characterized in that, It includes the following steps: S0. The diesel raw material oil first enters the fractionation system to separate the kerosene fraction and the diesel fraction. The kerosene fraction enters the jet fuel hydrofining reaction zone to prepare No. 3 jet fuel. S1. The diesel fraction is contacted with the 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 undergone sulfidation treatment and activation treatment. The second hydrofining reaction product can be directly used as a raw material for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components. In step S0, the cut point between the kerosene fraction and the diesel fraction in the fractionation system is 230 - 300 °C. Among them, the activation treatment includes the following specific steps: The hydrofining catalyst after sulfidation is contacted with the activation raw material for 24 - 120 hours in an activation gas atmosphere and under activation reaction conditions. 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% - 90% by mass. The activation reaction conditions are as follows: hydrogen partial pressure of 0.5 - 8.0 MPa, reaction temperature of 300 - 450 °C, volumetric space velocity of 0.1 - 8.0 h -1 , hydrogen-oil volume ratio of 50 - 1000 Nm 3 / m 3 , and the activation reaction time is 48 - 96 hours.

2. The method according to claim 1, characterized in that, In 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, wherein The organic solvent is an ionic liquid solvent.

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

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

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

7. The method according to claim 6, wherein In step S1, the mass ratio of the extraction solvent to the diesel fraction 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.

8. The method according to claim 7, characterized in that The mass ratio of the extraction solvent to the diesel fraction is 0.8 to 1.5:1, the pressure of the extraction column is 0.2 to 0.4 MPa, and the extraction temperature is 20 to 60 °C.

9. The method according to claim 6, characterized in that The adsorbent for the raffinate oil adsorption and solvent removal process is selected from activated carbon or molecular sieve.

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

11. The method according to claim 10, characterized in that, The active metals are cobalt and molybdenum.

12. The method according to claim 1, wherein 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 support with a bimodal pore distribution.

13. The method according to claim 1, characterized in that, 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, wherein 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 .

15. The method according to claim 1, wherein 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%.

16. The method according to claim 1, characterized in that 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.

17. 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, adjust to the hydrofining reaction conditions, and switch the feedstock oil from the activation feedstock to the aromatic extract oil; adjust the gas in the second hydrofining reactor to a hydrogen-rich gas, and the aromatic extract oil reacts with the catalyst under normal 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%.

18. The method according to claim 17, wherein In the step S5, the specific steps for adjusting to the normal reaction conditions after the activation is completed 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.

19. The method according to claim 1, wherein The total aromatic content of the activation feedstock is 55 mass%-80 mass%.

20. 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 .

21. The method according to claim 20, 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 .

22. The method according to claim 17, wherein In the hydrogen-rich gas, based on the overall 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%.

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

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

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

26. The method according to claim 1, wherein The diesel feedstock oil is selected from one or more of straight-run diesel, catalytic cracking diesel, and coking diesel.

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

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