A method for producing low-carbon olefin raw materials by selective desulfurization and denitrogenation of diesel

Abstract

The present invention relates to a method for preparing low-carbon olefin raw materials by selective desulfurization and denitrogenation of diesel, wherein the diesel raw material oil is contacted with a selectively regulated hydrofining catalyst for hydrofining reaction, and the obtained refined oil is subjected to solvent extraction to obtain extracted oil rich in aromatics and raffinate oil rich in alkanes; wherein the raffinate oil is used as a high-quality raw material for steam cracking to produce ethylene, and the extracted oil can be directly used as a raw material for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components. The present invention optimizes the raw materials and process structure of the existing device, not only fully utilizes various raw material resources, but also effectively solves the problem of diesel outlet and ethylene material shortage.

Description

Technical Field

[0001] The invention relates to a combined method of hydrogenation and extraction, in particular to a method for producing low-carbon olefin raw materials by solvent extraction after selective hydrogenation, desulfurization and denitrogenation of diesel. Background Art

[0002] Low-carbon olefins such as ethylene and propylene are the basic raw materials for chemical production. Steam cracking ethylene production is the leader in petrochemicals and has a major impact on the economic benefits of enterprises. In recent years, with the continuous increase in ethylene production capacity and the increasing shortage of crude oil resources, the contradiction between the supply and demand of raw materials for steam cracking ethylene has gradually increased, and how to expand its raw material sources has become particularly important.

[0003] By studying the relationship between the properties of raw materials and the yield of low-carbon olefins in the process of steam cracking to produce ethylene, it was found that the higher the normal alkane content and the lower the aromatic content of the cracking raw material, the more conducive it will be to increasing the olefin yield and reducing the coking of equipment, and the more suitable it will be as a cracking raw material.

[0004] In recent years, the adjustment of industrial structure has led to a significant change in the consumption structure of refined oil products, which is particularly reflected in the significant reduction in the diesel-to-gasoline ratio. In the future, the growth of diesel consumption will be much slower than that of gasoline, and the trend of differentiation in refined oil demand will be more obvious. In the future, the surplus of diesel resources will intensify and gasoline will turn into a tight balance. This has put forward new requirements for the adjustment of the refining product structure and device structure, and the task of reducing the diesel-to-gasoline ratio in production is arduous. Therefore, how to reduce diesel has become a topic of discussion among major refining companies.

[0005] Diesel oil has a high content of chain alkanes, and a large proportion of normal alkanes, making it a potential raw material for cracking. However, if some aromatics contained in diesel oil are directly fed into the ethylene cracking unit, it will cause an increase in the amount of coking in the cracking furnace, because only the side chains of aromatics in the cracking raw materials can be cracked to produce target products such as ethylene or propylene. The aromatic ring itself is difficult to open due to the high bond energy of the CC conjugated bond of 611 kJ / mol, and coking precursors are generated at 500-900°C. Under the catalytic effect of the furnace tube material nickel alloy steel, it can be dehydrogenated and condensed at 300-400°C to produce asphaltene with poor fluidity, which seriously affects production.

[0006] CN103666550B discloses a method for increasing the production of light olefins and aromatics by steam cracking of coking gasoline. The raw oil is pretreated with ionic liquid solvent to extract aromatics and ionic liquid solvent to extract olefins, respectively, to remove aromatics and olefins therefrom, and the obtained hydrocarbon stream with an aromatic content of less than 2wt% and an olefin content of less than 4wt% enters a steam cracking process for cracking and separation; the crude aromatic stream is sent to a hydrocracking gasoline aromatic extraction device to separate aromatic products, and the obtained saturated hydrocarbon-rich stream is returned and introduced into a cracking process together with an aromatic-poor petroleum hydrocarbon stream to react and produce light olefins.

[0007] CN1176293A discloses a method for preparing ethylene cracking material, which uses light wax oil and tar diesel as raw materials and produces ethylene cracking material through high-pressure hydrogenation refining. The process conditions are temperature of 300-350℃, hydrogen partial pressure of 15.0-17.0MPa, volume space velocity of 0.5-1.2h -1 , the purity of hydrogen is 92.0-98.0%. This method has high system pressure, high hydrogen consumption, high investment cost and high operating cost. Summary of the invention

[0008] The purpose of the present invention is to provide a method for producing low-carbon olefin raw materials by selectively desulfurizing and denitrogenating diesel based on the prior art.

[0009] The method provided by the present invention comprises:

[0010] (1) selectively controlling the hydrotreating catalyst, contacting the sulfided hydrotreating catalyst with an activation raw material in an activation gas atmosphere and under activation reaction conditions for 24 to 120 hours, wherein the activation gas comprises hydrogen, hydrogen sulfide and carbon monoxide, and based on the entire activation gas, the volume fraction of hydrogen is not less than 80%, and the volume fraction of the sum of hydrogen sulfide and carbon monoxide is 0.3% to 2%;

[0011] (2) hydrorefining, wherein the diesel feedstock is contacted with the hydrorefining catalyst treated in step (1) in a hydrogen-rich gas atmosphere under hydrorefining reaction conditions to carry out a hydrorefining reaction to obtain a refined oil, wherein the volume fraction of hydrogen is at least 80% and the volume fraction of the sum of hydrogen sulfide and carbon monoxide is less than 0.05% based on the entire hydrogen-rich gas;

[0012] (3) solvent extraction, the refined oil enters the extraction tower and is extracted with the extraction solvent to obtain an extracted oil rich in aromatics and a raffinate oil rich in alkanes, wherein the sulfur and nitrogen contents in the raffinate oil are both ≤10 μg / g, the paraffin content is not less than 55% by mass, and the aromatic content is less than 10% by mass. The raffinate oil is a raw material for steam cracking to produce ethylene.

[0013] In the present invention, the distillation range of the diesel feedstock oil is 150-400° C., and in the diesel feedstock oil, the paraffin content is ≥30% by mass, and the total aromatic content is ≤60% by mass.

[0014] In one embodiment of the present invention, the paraffin content of the diesel feedstock is ≥35% by mass, and the aromatic content is ≤45% by mass.

[0015] In one embodiment of the present invention, the diesel feedstock oil is selected from one or more of straight-run diesel, catalytic cracking light cycle oil, and coker diesel.

[0016] In one embodiment of the present invention, the distillation range of the activated raw material in step (1) is 150-400° C., and the total aromatics content is 50% to 90% by mass, preferably 55% to 80% by mass.

[0017] In one embodiment of the present invention, the activation reaction conditions in step (1) are: hydrogen partial pressure 0.5-8.0 MPa, reaction temperature 300-450°C, volume space velocity 0.1-8.0 h -1 、Hydrogen oil volume ratio 50~1000Nm 3 / m 3 , the activation reaction time is 48 to 96 hours.

[0018] In one embodiment of the present invention, the hydrotreating reaction conditions in step (2) are: hydrogen partial pressure 0.5-10.0 MPa, reaction temperature 300-450°C, liquid hourly volume space velocity 0.2-10.0 h -1 、Hydrogen oil volume ratio 50~1600Nm 3 / m 3 ; The preferred hydrogen partial pressure is 1.0 to 8.0 MPa, and the preferred reaction temperature is 320 to 400°C.

[0019] In one embodiment of the present invention, in step (2), based on the entire hydrogen-rich gas, the volume fraction of hydrogen is at least 85%, and the volume fraction of the sum of hydrogen sulfide and carbon monoxide is less than 0.02%.

[0020] In the present invention, the depth of the hydrofining reaction can be controlled under relatively mild hydrogenation reaction conditions by regulation. In a preferred case, the sulfur and nitrogen contents in the refined oil are ≤100 μg / g, and the aromatics are as saturated as possible, so as to achieve the goal of desulfurization and denitrogenation while minimizing the saturation of aromatics. In one embodiment of the present invention, the sulfur content in the refined oil is ≤100 μg / g, the nitrogen content is ≤100 μg / g, and the aromatic saturation rate is not greater than 10%.

[0021] The method provided by the present invention can reduce the influence of sulfur and nitrogen impurities on the extraction solvent and the impurity content in the extracted oil and the raffinate oil on the one hand; on the other hand, by controlling the appropriate severity of the hydrofining, the excessive hydrogenation saturation of aromatics to cycloalkanes can be effectively avoided, the influence on the solvent extraction is reduced, and the difficulty of extraction is reduced. Because in the extraction process, the separation of paraffins and cycloalkanes is relatively difficult and it is difficult to separate them effectively, by reducing the content of cycloalkanes in the hydrofining product, the difficulty of extraction can be effectively reduced and the extraction effect can be improved.

[0022] In one embodiment of the present invention, the hydrotreating catalyst is a supported catalyst or an unsupported catalyst comprising an active metal, wherein the active metal is at least one or more selected from molybdenum, tungsten, cobalt, and nickel; preferably, the active metal is cobalt and molybdenum.

[0023] In one embodiment of the present invention, a hydrogenation protective agent accounting for 5 to 20% of the total volume of the hydrogenation refining catalyst is loaded upstream of the hydrorefining catalyst, and the hydrogenation protective agent includes 1.0 to 5.0 weight % of nickel oxide, 5.5 to 10.0 weight % of molybdenum oxide and an alumina carrier with a double pore distribution. The hydrogenation protective agent is loaded upstream of the hydrorefining catalyst to 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.

[0024] In one embodiment of the present invention, the following steps are included:

[0025] (a) sulfiding a fresh hydrotreating catalyst or a regenerated hydrotreating catalyst;

[0026] (b) After the vulcanization process is completed, the gas in the reaction system is adjusted to an activating gas;

[0027] (c) introducing the activated raw material into the reaction system and contacting it with the sulfurized hydrotreating catalyst under activation reaction conditions;

[0028] (d) adjusting to normal reaction conditions, switching the activating feedstock to diesel with a high aromatic content, preferably catalytic cracking diesel;

[0029] (e) The gas in the reaction system is adjusted to be a hydrogen-rich gas, and the diesel feedstock is contacted with a hydrotreating catalyst under hydrotreating reaction conditions to react; the diesel feedstock is selectively desulfurized and denitrogenated, while deep hydrogenation of aromatics to cycloalkanes is avoided to obtain a refined oil with low sulfur and low nitrogen content.

[0030] In one embodiment of the present invention, the reaction temperature and reaction pressure of the activation reaction are equivalent to the reaction temperature and reaction pressure of the hydrotreating reaction conditions.

[0031] In one embodiment of the present invention, the volume space velocity of the activation reaction is equivalent to the volume space velocity of the hydrofining reaction conditions.

[0032] In a preferred embodiment of the present invention, in step (b), the concentration of hydrogen sulfide gas in the reactor gas is first reduced, then the concentration of carbon monoxide gas in the reactor gas is increased, and finally the gas in the reactor is adjusted to be an activation gas.

[0033] In a preferred embodiment of the present invention, in step (e), the concentration of carbon monoxide gas in the reactor gas is first reduced, then the concentration of hydrogen sulfide gas in the reactor gas is reduced, and finally the gas in the reactor is adjusted to be hydrogen-rich gas.

[0034] Since the oxides of cobalt, nickel, molybdenum and tungsten do not have hydrogenation activity and only have high hydrogenation activity when they exist in the sulfide state, it is necessary to sulfidize the fresh catalyst and the regenerated catalyst to convert it from the oxidized state to the sulfided state. The sulfidation process can be wet sulfidation or dry sulfidation. The sulfidation speed and degree of the catalyst are closely related to the sulfidation temperature. At each temperature, the sulfidation degree of the catalyst has a limit value. 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 catalyst bed temperature 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 no longer decreases.

[0035] The inventors of the present invention have found through a large number of experimental studies that after the catalyst is vulcanized, there are two active centers, namely, a desulfurization active center and an aromatic hydrogenation saturation active center. The present invention adds a catalyst selectivity regulation process between the vulcanization process and the normal production process, which can significantly shield one of the active centers, thereby improving the selectivity of the catalyst. The catalyst selectivity regulation process is to contact the activated raw material with the catalyst in the atmosphere of the activation gas and under the activation reaction conditions. This process can effectively cover the catalyst aromatic hydrogenation saturation active center, greatly reducing the catalyst aromatic hydrogenation saturation activity, while the desulfurization active center is effectively protected, so that the catalyst desulfurization activity is basically not lost or the loss is very small. And under high temperature conditions, the aromatic hydrogenation saturation activity is limited by thermodynamic equilibrium, which also effectively reduces the saturation activity of aromatics.

[0036] If only in H 2 In the presence of CO and CO atmosphere, under harsh reaction conditions, the Co in the sulfided CoMo catalyst is easily reduced to metallic Co, and the metallic Co easily reacts with CO to generate [Co(CO 4 )](carbonyl cobalt), thereby causing permanent deactivation of the catalyst's desulfurization activity. This is because, during the carbon deposition process, harsh conditions or raw materials that are more likely to produce carbon deposition will cause the carbon deposition reaction to occur not only at the hydrogenation active center, but also at the acidic center on the carrier surface, resulting in excessive carbon deposition on the catalyst carrier surface and blocking the catalyst pores. In this way, although the desulfurization active sites are protected, the catalyst pores are blocked, and the reactant molecules cannot approach the desulfurization active sites in the pores, which will also lead to a decrease in the catalyst's desulfurization activity. Therefore, the activating gas described in the present invention includes hydrogen, hydrogen sulfide and carbon monoxide. Based on the overall activating gas, it is preferred that the volume fraction of hydrogen is not less than 80%, and the volume fraction of the sum of hydrogen sulfide and carbon monoxide is 0.3% to 2%.

[0037] Diesel crude oil is contacted with a hydrotreating catalyst under hydrotreating reaction conditions to react. The reaction effluent enters a high-pressure separator to separate gaseous and liquid products. The gas phase is recycled after desulfurization, and the liquid phase enters a stripping tower. The bottom effluent of the stripping tower is used as refined oil and goes to an extraction device.

[0038] In one embodiment of the present invention, in step (3), refined oil enters the aromatic extraction tower from the bottom of the aromatic extraction tower, and the refined oil is countercurrently contacted with the extraction solvent from top to bottom in the extraction tower, and a raffinate oil poor in aromatics is obtained from the top of the tower, and a rich solvent rich in aromatics and solvent is obtained from the bottom of the tower; the obtained raffinate oil poor in aromatics is washed with water or adsorbed to separate trace amounts of solvent to obtain raffinate oil; the rich solvent rich in aromatics is sent to a distillation tower to recover the solvent, and an extracted oil rich in aromatics is obtained from the top of the distillation tower, and a solvent stream with an aromatic content of less than 0.5% by mass is obtained at the bottom of the distillation tower, which is returned to the top of the aromatic extraction tower for recycling.

[0039] In one embodiment of the present invention, the extraction solvent in step (3) is an ionic liquid, and the vaporization temperature of the ionic liquid at normal pressure is not less than 380°C. In one embodiment of the present invention, the ionic liquid comprises a cation and an anion: the cation is an alkyl-substituted imidazole or an alkyl-substituted pyridine, and the anion is a tetrafluoroborate or a hexafluorophosphate. Preferably, the ionic liquid is selected from one or more of 1-heptyl-4-methylpyridine tetrafluoroborate, 1-heptyl-4-methylpyridine hexafluorophosphate, 1-heptyl-3-methylimidazole tetrafluoroborate, 1-heptyl-3-methylimidazole hexafluoroborate, 1-hexyl-4-methylpyridine tetrafluoroborate, and 1-hexyl-4-methylpyridine hexafluorophosphate.

[0040] In one embodiment of the present invention, in step (3), the mass ratio of the extraction solvent to the refined 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; preferably, the mass ratio of the extraction solvent to the refined 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.

[0041] In one embodiment of the present invention, the total aromatic content of the extracted oil obtained in step (3) is not less than 70% by mass, and the monocyclic aromatic content is not less than 50% by mass. The extracted oil can be directly used as a feedstock for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components.

[0042] In one embodiment of the present invention, the adsorbent for the desolventizing process of the raffinate oil is selected from activated carbon and molecular sieve.

[0043] Features of the present invention:

[0044] 1. The present invention adopts a process route of first hydrofining diesel and then extracting it, which not only reduces the influence of sulfur and nitrogen impurities on the extraction solvent, but also the raffinate oil enriched by the solvent extraction method has the characteristics of low sulfur and nitrogen content, high paraffin content and low aromatic content, reduces the temperature of the cracking reaction in the process of preparing ethylene by steam cracking, reduces the coking of equipment, and prolongs the decoking cycle.

[0045] 2. The selective control method provided by the present invention can effectively remove impurities such as sulfur and nitrogen under relatively mild conditions, and minimize the deep saturation of aromatics, thereby reducing hydrogen consumption. Compared with the high temperature and low pressure conditions, the problem of easy deactivation of hydrofining catalysts is solved.

[0046] 3. The method of the present invention utilizes diesel oil to produce high-quality steam cracking ethylene raw material (ethylene material), and can provide raw materials for hydrocracking or catalytic cracking, and concurrently produce high-octane gasoline or BTX light components.

[0047] The present invention takes advantage of the integrated refining and chemical enterprises, optimizes the raw materials and process structure of the existing devices through the organic combination of diesel hydrorefining, aromatics extraction device and ethylene cracking device, not only fully utilizes various raw material resources, but also effectively solves the problem of diesel outlet and ethylene material shortage. DETAILED DESCRIPTION

[0048] The following examples will further illustrate the method provided by the present invention, but are not intended to limit the present invention.

[0049] The hydrogenation protective agent and the hydrofining catalyst used in the present invention can be prepared according to the prior art, or can be obtained commercially. For example, it can be one or more of the hydrogenation protective agent with the trade number RG-30A, RG-30B or RG-1 and the hydrofining catalyst with the trade number RS-2000, RS-2100 and RS-2200 purchased from Sinopec. In the embodiments of the present invention, RS-2200 is exemplarily used as a diesel hydrofining catalyst, which should not be understood by those skilled in the art as a limitation of the present invention.

[0050] In the Examples and Comparative Examples:

[0051] The selectivity factor is defined as follows: S = (((S f -S p ) / S f )*((N f -N p ) / N f )) / ((A f -A p ) / A f )

[0052] Where: S-selectivity factor; S p —Sulfur content of hydrofining products; S f —Sulfur content of raw materials; N p —Nitrogen content of hydrofining product; N f —Nitrogen content of raw materials; A p —Total aromatics mass content of hydrorefining product; A f —Mass content of total aromatics in raw materials.

[0053] The catalyst operation cycle is estimated based on the reaction temperature reaching 400°C and the deactivation rate of the catalyst being 1°C / month. Operation cycle = (final reaction temperature - initial reaction temperature) / 1

[0054] In the examples and comparative examples, straight-run diesel was used as the raw oil, denoted as raw oil A. The main properties of raw oil A are shown in Table 1.

[0055] Table 1 Raw oil properties

[0056] Crude oil A <![CDATA[Density (20 °C), g / cm 3 > 0.8484 Sulfur content, μg / g 12310 Nitrogen content, μg / g 259 Hydrocarbon composition, wt% Alkanes 45.7 Total cycloalkanes 28.8 Total aromatics 25.5 Total monocyclic aromatic hydrocarbons 15.8 Total bicyclic aromatic hydrocarbons 8.7 Tricyclic aromatic hydrocarbons 1.0 Distillation range, ℃ (IBP~FBP) 193～378

[0057] Example 1

[0058] The hydrofining catalyst in the fixed bed hydrogenation reactor is sulfurized. After the sulfurization is completed, the gas in the reaction system is adjusted to the activation gas, and the activation raw material is introduced into the reaction system and contacted with the hydrofining catalyst under the activation condition for 72 hours. The distillation range of the activation raw material is 150-400°C, and the mass fraction of aromatics is 50%.

[0059] After the activation is completed, the reaction conditions are adjusted to normal conditions, the activation raw material is switched to raw oil A, and the gas in the reactor is switched to hydrogen-rich gas.

[0060] The feedstock A and hydrogen-rich gas react with the selectively regulated hydrotreating catalyst at medium temperature and medium pressure. The reaction temperature is 340°C, the hydrogen partial pressure is 6.4 MPa, and the liquid hourly volume space velocity is 1.5 h -1 The standard hydrogen-to-oil volume ratio is 300:1. The effluent from the hydrotreating reaction is separated to obtain refined oil. The properties of the refined oil are shown in Table 2.

[0061] The ionic liquid of 1-heptyl-4-methylpyridinium tetrafluoroborate is used to contact the refined oil in reverse in an aromatic extraction tower for solvent extraction. The raffinate oil obtained at the top of the tower is adsorbed by activated carbon to obtain the raffinate oil. Its properties are shown in Table 3. It can be seen from Table 3 that the raffinate oil obtained can be used as a high-quality steam cracking raw material for preparing light olefins.

[0062] The rich solvent rich in aromatics and solvent obtained at the bottom of the extraction tower is sent to the distillation tower to recover the solvent, and the extracted oil rich in aromatics is obtained from the top of the distillation tower. The solvent stream with an aromatic content of less than 0.5% by mass is obtained at the bottom of the distillation tower and returned to the top of the aromatic extraction tower for recycling.

[0063] The properties of the extracted oil are shown in Table 4. The extracted oil can be directly used as a feedstock for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components.

[0064] Example 2

[0065] The hydrofining catalyst in the fixed bed hydrogenation reactor is sulfurized. After the sulfurization is completed, the gas in the reaction system is adjusted to the activation gas, and the activation raw material is introduced into the reaction system and contacted with the hydrofining catalyst under the activation condition for 48 hours. The distillation range of the activation raw material is 150-400°C, and the mass fraction of aromatics is 60%.

[0066] Then adjust to normal reaction conditions, switch the activating raw material to raw material oil A, and switch the gas in the reactor to hydrogen-rich gas.

[0067] The feedstock A and hydrogen-rich gas react with the selectively regulated hydrotreating catalyst at medium temperature and medium pressure. The reaction temperature is 360°C, the hydrogen partial pressure is 6.4 MPa, and the liquid hourly volume space velocity is 1.5 h -1 The standard hydrogen-to-oil volume ratio is 300:1. The effluent from the hydrotreating reaction is separated to obtain refined oil. The properties of the refined oil are shown in Table 2.

[0068] The ionic liquid of 1-heptyl-4-methylpyridinium hexafluoroborate is used to contact the refined oil in reverse in an aromatic extraction tower for solvent extraction. The raffinate oil obtained at the top of the tower is adsorbed by activated carbon to obtain the raffinate oil. Its properties are shown in Table 3. It can be seen from Table 3 that the raffinate oil obtained can be used as a high-quality steam cracking raw material for preparing light olefins.

[0069] The rich solvent rich in aromatics and solvent obtained at the bottom of the extraction tower is sent to the distillation tower to recover the solvent, and the extracted oil rich in aromatics is obtained from the top of the distillation tower. The solvent stream with an aromatic content of less than 0.5% by mass is obtained at the bottom of the distillation tower and returned to the top of the aromatic extraction tower for recycling. The properties of the obtained extracted oil are shown in Table 4. The extracted oil can be directly used as a raw material for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components.

[0070] Comparative Example 1

[0071] The hydrotreating catalyst in the fixed bed hydrogenation reactor was sulfurized. After the sulfurization was completed, the reaction conditions were adjusted to normal. The feedstock A and the hydrogen-rich gas reacted with the hydrotreating catalyst at high temperature and low pressure. The reaction temperature was 380°C, the hydrogen partial pressure was 3.2MPa, and the liquid hourly volume space velocity was 1.5h -1The standard hydrogen / oil volume ratio is 300:1. The effluent from the hydrotreating reaction is separated to obtain refined oil. The properties of the refined oil are shown in Table 2.

[0072] The same ionic liquid as in Example 1 was used to extract aromatics from the refined oil to obtain raffinate oil and extracted oil, and their properties are shown in Table 3 and Table 4, respectively.

[0073] Comparative Example 2

[0074] In this comparative example, the raw material oil A is hydrotreated and the obtained refined oil is directly used as the raw material for steam cracking to produce ethylene. The hydrotreatment process conditions adopted are: reaction temperature of 340°C, hydrogen partial pressure of 6.4 MPa, liquid hourly volume space velocity of 1.5 h -1 The standard hydrogen-oil volume ratio is 300:1. The effluent of the hydrofining reactor is separated into gas and liquid in the separator, and the gas phase is returned to the reactor inlet to obtain a liquid phase with sulfur and nitrogen content <100μg / g as refined oil. The properties are shown in Table 2.

[0075] Comparative Example 3

[0076] In this comparative example, the raw oil A is directly fed into the solvent extraction unit without passing through the hydrorefining unit, and the raw oil A is reversely contacted with the ionic liquid of 1-heptyl-4-methylpyridinium tetrafluoroborate in the aromatic extraction tower to perform solvent extraction. The raffinate oil obtained at the top of the tower is adsorbed by activated carbon to obtain the raffinate oil, and its properties are shown in Table 3.

[0077] The properties of the extracted oil obtained after separation of the solvent are shown in Table 4.

[0078] Comparative Example 4

[0079] The hydrotreating catalyst in the fixed bed hydrotreating reactor is sulfurized. After the sulfurization is completed, the reaction conditions are adjusted to normal. The feedstock A and the hydrogen-rich gas react with the hydrotreating catalyst at medium temperature and medium pressure. The hydrotreating process conditions are: reaction temperature of 340°C, hydrogen partial pressure of 6.4MPa, liquid hourly volume space velocity of 1.5h -1 The standard hydrogen-to-oil volume ratio is 300:1. The effluent from the hydrotreating reaction is separated to obtain refined oil. The properties of the refined oil are shown in Table 2.

[0080] The same ionic liquid as in Example 1 was used to extract aromatics from the refined oil to obtain raffinate oil and extracted oil, and their properties are shown in Table 3 and Table 4, respectively.

[0081] Table 2 Hydrorefining process conditions and refined oil properties

[0082]

[0083]

[0084] Table 3 Solvent extraction process conditions and raffinate oil properties

[0085]

[0086]

[0087] Table 4 Extracted oil properties

[0088]

[0089] As shown in Tables 2 to 4, the diesel treated according to the method of the present invention not only effectively removes sulfur and nitrogen impurities, reduces the deep hydrogenation saturation of aromatics, significantly improves the selectivity factor of the catalyst, and can effectively improve the operation cycle, reducing the deep hydrogenation saturation of aromatics. The sulfur and nitrogen contents in the obtained raffinate oil are both less than 100 μg / g, the paraffin content is not less than 55% by mass, and the aromatic content is less than 10% by mass. It can be used as a high-quality raw material for steam cracking to produce ethylene. The total aromatic content of the extracted oil is not less than 70% by mass, the content of monocyclic aromatics is not less than 50% by mass, and the content of polycyclic aromatics is less than 15% by mass. It can be directly used as a raw material for hydrocracking or catalytic cracking to produce high-octane gasoline or BTX light components.

Claims

1. A method for producing light olefin raw materials by selective desulfurization and denitrogenation of diesel, comprising: (1) Selective regulation of the hydrofining catalyst, wherein the sulfided hydrofining catalyst is contacted with an activation raw material in an activation gas atmosphere and under activation reaction conditions for 24 to 120 hours, wherein the activation gas comprises hydrogen, hydrogen sulfide and carbon monoxide, and based on the entire activation gas, the volume fraction of hydrogen is not less than 80%, and the volume fraction of the sum of hydrogen sulfide and carbon monoxide is 0.3% to 2%, the distillation range of the activation raw material is 150 to 400° C., and the total aromatic content is 50% to 90% by mass, and the activation reaction conditions are: hydrogen partial pressure of 0.5 to 8.0 MPa, reaction temperature of 300 to 450° C., and volume space velocity of 0.1 to 8.0 h / min. -1 、Hydrogen oil volume ratio 50~1000Nm 3 / m 3 ; (2) hydrorefining, wherein the diesel feedstock is contacted with the hydrorefining catalyst treated in step (1) in a hydrogen-rich gas atmosphere under hydrorefining reaction conditions to carry out a hydrorefining reaction to obtain a refined oil, wherein the volume fraction of hydrogen is at least 80% and the volume fraction of the sum of hydrogen sulfide and carbon monoxide is less than 0.05% based on the entire hydrogen-rich gas; (3) solvent extraction, the refined oil enters the extraction tower and is extracted with the extraction solvent to obtain an extracted oil rich in aromatics and a raffinate oil rich in alkanes, wherein the sulfur and nitrogen contents in the raffinate oil are both ≤10 μg / g, the paraffin content is not less than 55% by mass, and the aromatic content is less than 10% by mass. The raffinate oil is a raw material for steam cracking to produce ethylene.

2. The method according to claim 1, characterized in that: The distillation range of the diesel feedstock oil is 150-400° C., and in the diesel feedstock oil, the paraffin content is ≥30% by mass, and the total aromatic content is ≤60% by mass.

3. The method according to claim 1, characterized in that In the diesel feedstock oil, the paraffin content is ≥35% by mass, and the aromatic content is ≤45% by mass.

4. The method according to claim 1, characterized in that: The total aromatic content of the activated raw material in step (1) is 55% to 80% by mass.

5. The method according to claim 1, characterized in that: The activation reaction time in step (1) is 48 to 96 hours.

6. The method according to claim 1, characterized in that The hydrotreating reaction conditions in step (2) are: hydrogen partial pressure 0.5-10.0 MPa, reaction temperature 300-450°C, liquid hourly volume space velocity 0.2-10.0 h -1 , hydrogen oil volume ratio 50~1600Nm 3 / m 3 .

7. The method according to claim 1, characterized in that The hydrotreating reaction conditions described in step (2) are: hydrogen partial pressure 1.0-8.0 MPa, reaction temperature 320-400°C.

8. The method according to claim 1, characterized in that In step (2), based on the entire hydrogen-rich gas, the volume fraction of hydrogen is at least 85%, and the volume fraction of the sum of hydrogen sulfide and carbon monoxide is less than 0.02%.

9. The method according to claim 1, characterized in that: The hydrotreating catalyst is a supported catalyst or a non-supported catalyst comprising an active metal, and the active metal is at least one or more selected from molybdenum, tungsten, cobalt and nickel.

10. The method according to claim 9, characterized in that The active metals are cobalt and molybdenum.

11. The method according to claim 1, characterized in that: A hydrogenation protecting agent accounting for 5-20% of the total volume of the hydrogenation refining catalyst is loaded upstream of the hydrogenation refining catalyst. The hydrogenation protecting agent includes 1.0-5.0 wt% nickel oxide, 5.5-10.0 wt% molybdenum oxide and an alumina carrier with a double pore distribution.

12. The method according to claim 1, characterized in that The sulfur content in the refined oil is ≤100μg / g, the nitrogen content is ≤100μg / g, and the aromatic saturation rate is not more than 10%.

13. The method according to claim 1, characterized in that The extraction solvent described in step (3) is an ionic liquid, and the vaporization temperature of the ionic liquid under normal pressure is not less than 380°C.

14. The method according to claim 13, characterized in that The ionic liquid comprises cations and anions: the cations are alkyl-substituted imidazole or alkyl-substituted pyridine, and the anions are tetrafluoroborate or hexafluorophosphate.

15. The method according to claim 14, characterized in that The ionic liquid is selected from one or more of 1-heptyl-4-methylpyridine tetrafluoroborate, 1-heptyl-4-methylpyridine hexafluorophosphate, 1-heptyl-3-methylimidazolium tetrafluoroborate, 1-heptyl-3-methylimidazolium hexafluoroborate, 1-hexyl-4-methylpyridine tetrafluoroborate, and 1-hexyl-4-methylpyridine hexafluorophosphate.

16. The method according to claim 1, characterized in that In step (3), the mass ratio of the extraction solvent to the refined 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.

17. The method according to claim 1, characterized in that In step (3), the mass ratio of the extraction solvent to the refined 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.

18. The method according to claim 1, characterized in that The total aromatic content of the extracted oil obtained in step (3) is not less than 70% by mass, and the monocyclic aromatic content is not less than 50% by mass.

Images