Processing method of high-sulfur high-nitrogen inferior diesel oil

Abstract

The invention discloses a high-sulfur high-nitrogen inferior diesel oil processing method, which comprises: (1) in the presence of hydrogen, mixing an inferior diesel oil raw material with an alkali metal, and feeding into an alkali metal treatment reaction zone; (2) feeding the reaction effluent obtained in the step (1) into a separation unit to obtain a liquid-phase material flow; (3) mixing the liquid-phase material flow in the step (2) with an oxidizing agent, and enabling the mixture to enter an oxidation reaction zone for reaction; and (4) the reaction effluent obtained in the step (3) enters an extraction unit, and a final clean diesel oil product is obtained under the action of an extraction agent. According to the method, the inferior diesel oil is processed by adopting a non-hydrogenation technical means, and the clean diesel oil with low sulfur, low nitrogen and high cetane number can be directly produced.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and relates to a processing method of high-sulfur and high-nitrogen inferior diesel, and specifically relates to a method of processing high-sulfur and high-nitrogen inferior diesel to produce clean diesel. Background Art

[0002] The main secondary processed diesel in my country is catalytic cracking diesel and delayed coking diesel. As the degree of heavy and inferior crude oil in the world continues to increase and the degree of heavy oil conversion continues to deepen, the properties of secondary processed diesel in my country have further deteriorated, mainly manifested in the further increase of impurity content such as sulfur content and nitrogen content, and the further decrease of cetane number.

[0003] On the other hand, with the continuous improvement of environmental protection requirements, countries around the world have higher and higher requirements for automotive fuels. From July 1, 2023, the 6b stage of the National VI Emission Standard will be fully implemented in my country, which will strictly control diesel indicators, require the sulfur content to be reduced to below 0.035wt%, and make fuel index requirements for automotive lubricity and acid methyl esters, reduce the polycyclic aromatic hydrocarbons index to 7wt%, and further increase the cetane number to 49. The low-quality characteristics of high-sulfur, high-nitrogen, and inferior diesel have caused a great contradiction with the increasingly improved diesel product indicators. It can be seen that how to produce clean diesel from high-sulfur, high-nitrogen, and inferior diesel is a major problem facing oil refining companies.

[0004] In view of the above situation, the prior art generally adopts hydrogenation technology to treat low-quality diesel with high sulfur and high nitrogen to produce clean diesel that meets environmental protection requirements. CN106554815A discloses a method for producing clean diesel: the reaction product of the low-quality diesel with high sulfur and nitrogen and the second hydrogenation reaction zone is mixed with the hydrogen-containing stream and then reacted in the first hydrogenation reaction zone to obtain the hydrofining reaction product, and the product is separated and fractionated to obtain a refined diesel fraction and a heavy diesel fraction, and at least part of the heavy diesel fraction and the hydrogen-containing stream are introduced into the second hydrogenation reaction zone, the product of the second hydrogenation reaction zone is introduced into the first hydrogenation reaction zone, and the refined diesel fraction is mixed with the remaining part of the heavy diesel fraction to obtain clean diesel, wherein the sulfur content in the low-quality diesel with high sulfur and nitrogen is higher than 5000 μg / g, the nitrogen content is higher than 700 μg / g, and the aromatic content is higher than 50% by weight.

[0005] CN111286360A discloses a diesel hydrorefining device and method, which uses a pre-fractionation tower to separate diesel raw materials into light and heavy fractions, so that the light fraction contains almost no dibenzothiophene and its derivatives, while the heavy fraction contains almost all dibenzothiophene and its derivatives that are difficult to desulfurize by hydrodesulfurization. The sulfides in the light fraction are mainly mercaptans, disulfides, thiophenes and benzothiophene sulfides, which can be removed under a lower reaction severity; the heavy fraction mainly contains sulfides and polycyclic aromatic hydrocarbons that are difficult to remove dibenzothiophene sulfides. In order to reduce the sulfur content of the heavy diesel product to below 10ppm, the content of polycyclic aromatic hydrocarbons is strictly controlled, and the reaction severity is slightly higher than that of a general diesel hydrorefining reactor.

[0006] However, the hydrogenation technology in the above patent has relatively strict requirements on reaction conditions, and it is difficult to deeply remove nitrogen-containing compounds and sulfur-containing compounds in diesel; and the production cost of hydrogenation technology is relatively high, which limits the further application of this technology in the field of low-quality diesel processing. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a method for processing high-sulfur and high-nitrogen low-quality diesel. The method uses non-hydrogenation technology to process low-quality diesel and can directly produce clean diesel with low sulfur, low nitrogen and high cetane number.

[0008] A method for processing high-sulfur, high-nitrogen low-quality diesel, the method comprising the following steps: (1) In the presence of hydrogen, the low-quality diesel feedstock is mixed with alkali metal and then enters the alkali metal treatment reaction zone; (2) The reaction effluent obtained in step (1) enters a separation unit to obtain a liquid phase stream; (3) The liquid phase stream in step (2) is mixed with the oxidant and enters the oxidation reaction zone for reaction; (4) The reaction effluent obtained in step (3) enters the extraction unit, and the final clean diesel product is obtained under the action of the extractant.

[0009] Furthermore, in the above-mentioned method for processing high-sulfur and high-nitrogen low-quality diesel, the low-quality diesel feedstock in step (1) has a sulfur content higher than 6000 μg / g, preferably 8000-15000 μg / g; and a nitrogen content higher than 800 μg / g, preferably 1000-2500 μg / g.

[0010] Furthermore, in the above-mentioned method for processing high-sulfur, high-nitrogen low-quality diesel, the alkali metal in step (1) belongs to Group IA elements in the periodic table, including one or more of lithium, sodium, potassium, rubidium, and cesium, preferably one or more of lithium, sodium and potassium, and more preferably sodium.

[0011] Furthermore, in the above-mentioned method for processing high-sulfur and high-nitrogen low-quality diesel, the molar ratio of the alkali metal to the sulfur content of the low-quality diesel feedstock in step (1) is 1.5-3.5, preferably 2.0-3.0.

[0012] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, the alkali metal in step (1) is mixed with a dispersion medium to obtain an alkali metal dispersion; the alkali metal dispersion is then mixed with the low-quality diesel feedstock and then enters the alkali metal treatment reaction zone.

[0013] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, the dispersion medium in step (1) can be any dispersion medium that does not react with alkali metals and has a boiling point higher than the melting point of alkali metals, including one or more of n-pentadecane, n-hexadecane, benzene, toluene and xylene; the mass ratio of the alkali metal to the dispersion medium is 1:(1-3).

[0014] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, the alkali metal and the dispersion medium in step (1) can be mixed by any means in the prior art that can achieve liquid-liquid mixing. Specifically, in the present invention, one or more of the high-speed stirring method, pump jet method, colloid mill method and ultrasonic method can be used. Preferably, the high-speed stirring method is used. It is further preferred to use the high-speed stirring method under appropriate temperature, time and stirring rate conditions; the temperature is 70-150°C, preferably 100-130°C; the time is 10-60min, preferably 20-40min; the stirring rate is 2000-10000r / min, preferably 4000-8000r / min.

[0015] Furthermore, in the above-mentioned method for processing high-sulfur, high-nitrogen low-quality diesel, the diameter distribution range of the alkali metal particles in the alkali metal dispersion in step (1) is 5-100 μm, preferably 10-30 μm.

[0016] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, in step (1), the alkali metal treatment reaction zone is provided with 1-3 alkali metal treatment reactors, preferably 1 alkali metal treatment reactor; the alkali metal treatment reactor is any one of a kettle reactor, a tubular reactor and a jet reactor, preferably a kettle reactor, and more preferably a kettle reactor with stirring.

[0017] Furthermore, in the above-mentioned method for processing high-sulfur and high-nitrogen low-quality diesel, the operating conditions of the alkali metal treatment reaction zone in step (1) are: reaction temperature 200-380°C, reaction pressure 2.0-20.0MPa, residence time 5-40min, hydrogen-to-oil volume ratio 100-2000Nm 3 / m 3The preferred operating conditions are: reaction temperature 280-340°C, reaction pressure 5.0-15.0MPa, residence time 10-25min, hydrogen to oil volume ratio 500-1500Nm 3 / m 3 .

[0018] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, the separation unit in step (2) is solid-liquid separation, and there is no limitation on the method of solid-liquid separation, and any technology that can achieve solid-liquid two-phase separation in the prior art can be used. Specifically in the present invention, solid-liquid separation can be carried out by at least one of decantation, filtration, centrifugal separation and gravity sedimentation, preferably centrifugal separation.

[0019] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, the oxidant in step (3) includes at least one of an organic peroxy acid, an inorganic peroxy acid and a peroxy salt, preferably hydrogen peroxide (30wt%)-organic acid, and the organic acid includes at least one of formic acid, acetic acid and propionic acid; the volume ratio of the organic acid to hydrogen peroxide (30wt%) is (0.5-4.0):1, preferably (1.5-2.5):1.

[0020] Furthermore, in the above-mentioned method for processing high-sulfur, high-nitrogen, low-quality diesel, the volume ratio of the oxidant in step (3) to the liquid phase logistics in step (2) is (0.1-0.3):1.

[0021] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, in step (3), 1 to 3 oxidation reactors are arranged in the oxidation reaction zone, preferably 1 oxidation reactor is arranged; the oxidation reactor can adopt a reactor capable of realizing liquid-liquid two-phase reaction in the prior art of the present invention, such as a kettle reactor and / or a tubular reactor.

[0022] Furthermore, in the above-mentioned method for processing high-sulfur, high-nitrogen low-quality diesel, the operating conditions of the oxidation reaction zone in step (3) are as follows: oxidation temperature is 30-80°C, preferably 40-70°C; oxidation time is 10-50min, preferably 20-40min.

[0023] Furthermore, in the above-mentioned processing method of high-sulfur, high-nitrogen low-quality diesel, the reaction effluent obtained in step (3) enters the extraction unit, and the final clean diesel product is obtained under the action of the extractant, which specifically includes the following contents: S1. The reaction effluent obtained in step (3) is divided into two streams, a first stream and a second stream; S2, the first material obtained in step S1 enters the extraction unit, and the final clean diesel product is obtained under the action of the extractant; S3. The second material obtained in step S1 is circulated to the alkali metal treatment reaction zone.

[0024] Furthermore, in step S1, the mass ratio of the first material to the second material is 1:(0.1-0.3).

[0025] Furthermore, the second material obtained in step S1 is circulated to the alkali metal treatment reaction zone in the following manner: the second material is mixed with the alkali metal and the dispersion medium to obtain an alkali metal dispersion; or the second material is circulated to any alkali metal treatment reactor in the alkali metal treatment zone.

[0026] Furthermore, in the above-mentioned processing method of high-sulfur, high-nitrogen low-quality diesel, the extractant in step (4) is a polar solvent, including one or more of ethanol, furfural, diethylene glycol, dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF).

[0027] Furthermore, in the above-mentioned method for processing high-sulfur, high-nitrogen, low-quality diesel, the volume ratio of the extractant in step (4) to the reaction effluent obtained in step (3) is 0.5-0.9.

[0028] Furthermore, in the above-mentioned processing method of high-sulfur and high-nitrogen low-quality diesel, the extraction in step (4) adopts single-stage extraction or multi-stage extraction, preferably multi-stage extraction; the multiple extraction stages are any one of primary, secondary, tertiary, quaternary and fifth stages, preferably three and / or four stages.

[0029] Furthermore, in the above-mentioned method for processing high-sulfur, high-nitrogen low-quality diesel, the extraction operating conditions in step (4) are as follows: extraction temperature 40-90°C, extraction time 1-10 min.

[0030] The inventor found in the research process that for alkali metal treatment technology, the molecular structure will affect the collision probability of alkali metal molecules with sulfur-containing and nitrogen-containing compounds, and is a key factor affecting the desulfurization efficiency and denitrification efficiency. It can be seen from this that: first, compared with sulfur-containing compounds, most of the nitrogen-containing compounds in heavy oil are pyridine and pyrrole nitrogen heterocycles, most of which also form very stable structures with aromatic rings, and the structure is more complex, resulting in a smaller collision probability between alkali metal molecules and nitrogen-containing compound molecules, so the denitrification efficiency is significantly lower than the desulfurization efficiency; second, the more complex the molecular structure of the sulfur-containing compound, the greater the difficulty of removal, among which 4,6-dimethyldibenzothiophene sulfides are the most difficult to remove, because the two alkyl groups at the β position of this type of sulfide have a very strong steric hindrance effect, so the removal of the above sulfides is the key to achieving low-sulfur diesel production. However, if nitrogen-containing compounds and 4,6-dimethyldibenzothiophene sulfides are removed by alkali metal treatment technology, more harsh reaction conditions must be adopted, which goes against the original intention of alkali metal treatment technology. Therefore, the method of the present invention adopts a combined process of alkali metal treatment technology and oxidative extraction technology to process low-quality diesel with high sulfur and high nitrogen, wherein the alkali metal treatment reaction zone only needs to complete the removal of most sulfides under mild conditions, while the oxidative extraction technology is used to remove nitrogen-containing compounds and 4,6-dimethyldibenzothiophene sulfides, thereby realizing the production of ultra-low sulfur and low nitrogen clean diesel.

[0031] Furthermore, in the alkali metal treatment reaction zone, the alkali metal and the sulfur-containing compound react to form alkali metal sulfides such as sodium sulfide. The above substances have a high melting point (taking sodium sulfide as an example, the melting point is 1180°C). Therefore, alkali metal sulfides such as sodium sulfide will be coated on the surface of the alkali metal droplets, making it difficult for the alkali metal inside the alkali metal droplets to contact and react with the sulfur-containing compound. Therefore, it is necessary to suppress the aggregation of alkali metals and reduce the size of alkali metal droplets. In the method of the present invention, the nitrogen-containing compounds and part of the sulfide-containing compounds in the oxidation reaction zone are oxidized to obtain nitrogen oxides and sulfur oxides, and their polarity increases exponentially. Therefore, part of the reaction effluent from the oxidation reaction zone is circulated to the alkali metal treatment reaction zone. According to the principle of like dissolves like, the aggregation of alkali metals can be effectively suppressed, and the utilization efficiency of alkali metals can be improved.

[0032] Compared with the prior art, the advantages of the present invention are: 1. The method of the present invention adopts a combined process of alkali metal treatment technology and oxidative extraction technology to process low-quality diesel with high sulfur and high nitrogen, wherein the alkali metal treatment reaction zone only needs to remove most of the sulfides under mild conditions, and then the oxidative extraction technology is used to remove nitrogen-containing compounds and 4,6-dimethyldibenzothiophene sulfides, thereby achieving the production of ultra-low sulfur and low nitrogen clean diesel.

[0033] 2. The method of the present invention recycles part of the reaction effluent from the oxidation reaction zone to the alkali metal treatment reaction zone. According to the principle of like dissolves like, it can effectively inhibit the aggregation of alkali metals and improve the utilization efficiency of alkali metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a schematic diagram of the process flow of a method for processing high-sulfur, high-nitrogen, low-quality diesel.

[0035] Among them, 1 is hydrogen, 2 is low-quality diesel feedstock, 3 is alkali metal, 4 is auxiliary agent, 5 is mixing device, 6 is alkali metal dispersion, 7 is alkali metal treatment reactor, 8 is alkali metal treatment reactor reaction effluent, 9 is separation device, 10 is liquid phase flow, 11 is solid phase flow, 12 is oxidant, 13 is oxidation reactor, 14 is extractant, 15 is oxidation reactor reaction effluent, 16 is raffinate, 17 is final clean diesel product, and 18 is extraction device.

[0036] Figure 2 The figure is a schematic diagram of the process flow of another method for processing high-sulfur, high-nitrogen low-quality diesel of the present invention.

[0037] Among them, 1 is hydrogen, 2 is low-quality diesel feedstock, 3 is alkali metal, 4 is additive, 5 is mixing device, 6 is alkali metal dispersion, 7 is alkali metal treatment reactor, 8 is alkali metal treatment reactor reaction effluent, 9 is separation device, 10 is liquid phase logistics, 11 is solid phase logistics, 12 is oxidant, 13 is oxidation reactor, 14 is extractant, 15 is first logistics, 16 is raffinate, 17 is final clean diesel product, 18 is extraction device, and 19 is second logistics. Implementation

[0038] The method provided by the present invention is described below in conjunction with the accompanying drawings.

[0039] like Figure 1 As shown, alkali metal 3 and auxiliary agent 4 enter into a mixing device to obtain alkali metal dispersion 6, which is then mixed with hydrogen 1 and inferior diesel feedstock 2 and enters into alkali metal treatment reactor 7 for reaction, reaction effluent 8 enters into separation device 9 for solid-liquid separation to obtain liquid phase stream 10 and solid phase stream 11, liquid phase stream 10 and oxidant 12 enter into oxidation reactor 13 for oxidation reaction, reaction effluent 15 enters into extraction device 18, and under the action of extraction agent 14, final clean diesel product 17 and raffinate 16 are obtained.

[0040] like Figure 2As shown, alkali metal 3 and auxiliary agent 4 enter into a mixing device to obtain alkali metal dispersion 6, which is then mixed with hydrogen 1 and inferior diesel feedstock 2 and enters into alkali metal treatment reactor 7 for reaction, reaction effluent 8 enters into separation device 9 for solid-liquid separation to obtain liquid phase stream 10 and solid phase stream 11, liquid phase stream and oxidant 12 enter into oxidation reactor 13 for oxidation reaction, reaction effluent is divided into first material 15 and second material 19, wherein first material 15 enters into extraction unit, enters into extraction device 18, and under the action of extractant 14, obtains final clean diesel product 17 and raffinate 16; second material 19 is circulated to alkali metal treatment reaction zone.

[0041] The following examples and comparative examples will further illustrate the method provided by the present invention, but are not intended to limit the present invention.

[0042] The properties of the inferior diesel raw materials used in the examples and comparative examples are shown in Table 1.

[0043] Table 1 Properties of low-quality diesel raw materials

[0044] Example 1 Example 1 uses Figure 1 The specific operation process is as follows: (1) Sodium and benzene are mixed by high-speed stirring to obtain a sodium dispersion, in which the diameter distribution range of sodium particles is 10-85 μm; the operating conditions are as follows: the mass ratio of sodium to benzene is 1:2, the temperature is 110°C, the time is 20 min, and the stirring rate is 3500 r / min; (2) The low-quality diesel raw material is mixed with the sodium dispersion and then enters the alkali metal treatment reactor for reaction; the alkali metal treatment reactor adopts a stirred tank reactor with a rotation speed set at 800r / min; (3) The reaction effluent obtained in step (2) enters a high-speed centrifuge for solid-liquid separation to obtain a liquid phase flow, and the speed of the high-speed centrifuge is 10000r / min; (4) The liquid phase stream in step (3) is mixed with hydrogen peroxide (30 wt%)-formic acid and enters into an oxidation reactor for reaction; the volume ratio of formic acid to hydrogen peroxide (30 wt%) is 2.5:1; the oxidation reactor is a stirred tank reactor, and the rotation speed is set to 800 r / min; (5) The reaction effluent obtained in step (4) enters the extraction unit and is subjected to three-stage extraction using furfural as an extractant to obtain a final clean diesel product.

[0045] Example 2 Compared with Example 1, the sodium dispersion is not synthesized in Example 2, but is directly mixed with the low-quality diesel raw material. The specific operation process is as follows: (1) After the low-quality diesel raw material is mixed with sodium, it enters the alkali metal treatment reactor for reaction; the alkali metal treatment reactor adopts a stirred tank reactor with a rotation speed set at 2500r / min; (2) The reaction effluent obtained in step (1) enters a high-speed centrifuge for solid-liquid separation to obtain a liquid phase flow, and the speed of the high-speed centrifuge is 10000r / min; (3) The liquid phase stream in step (2) is mixed with hydrogen peroxide (30 wt%)-formic acid and enters an oxidation reactor for reaction; the volume ratio of formic acid to hydrogen peroxide (30 wt%) is 1.5:1; the oxidation reactor is a stirred tank reactor, and the rotation speed is set to 800 r / min; (4) The reaction effluent obtained in step (3) enters an extraction unit and is subjected to three-stage extraction using furfural as an extractant to obtain a final clean diesel product.

[0046] Example 3 Compared with Example 1, Example 3 adds a process flow of recycling materials to the alkali metal treatment reaction zone. The specific operation process is as follows: (1) Potassium and toluene are mixed by high-speed stirring to obtain a potassium dispersion, wherein the potassium particles in the potassium dispersion have a diameter distribution range of 5-45 μm; the operating conditions are as follows: a mass ratio of potassium to toluene of 1:2, a temperature of 120°C, a time of 30 minutes, and a stirring rate of 5000 r / min; (2) The inferior diesel raw material is mixed with the potassium dispersion and then enters the alkali metal treatment reactor for reaction; the alkali metal treatment reactor adopts a stirred tank reactor with a rotation speed set at 800r / min; (3) The reaction effluent obtained in step (2) enters a high-speed centrifuge for solid-liquid separation to obtain a liquid phase flow, and the speed of the high-speed centrifuge is 10000r / min; (4) The liquid phase stream in step (3) is mixed with hydrogen peroxide (30 wt%)-formic acid and enters into an oxidation reactor for reaction; the volume ratio of formic acid to hydrogen peroxide (30 wt%) is 2.5:1; the oxidation reactor is a stirred tank reactor, and the rotation speed is set to 800 r / min; (5) The reaction effluent obtained in step (4) is divided into two streams, a first material and a second material, with a mass ratio of 1:0.1; (6) The first material obtained in step (5) enters an extraction unit and undergoes four-stage extraction using furfural as an extractant to obtain a final clean diesel product; (7) The second material obtained in step (5) is circulated to the alkali metal treatment reactor and mixed with the low-quality diesel feedstock for co-feeding.

[0047] Example 4 Example 4 uses Figure 2 The specific operation process is as follows: (1) Potassium and n-hexadecane are mixed by high-speed stirring to obtain a potassium dispersion, wherein the potassium particles in the potassium dispersion have a diameter distribution range of 5-25 μm; the operating conditions are as follows: a mass ratio of potassium to n-hexadecane of 1:1, a temperature of 125°C, a time of 40 minutes, and a stirring rate of 7500 r / min; (2)-(4) Same as Example 3; (5) The reaction effluent obtained in step (4) is divided into two streams, a first material and a second material, with a mass ratio of 1:0.3; (6) Same as Example 3; (7) The second material obtained in step (5) is circulated to the alkali metal treatment reaction zone and mixed with potassium and n-hexadecane to obtain a potassium dispersion.

[0048] Example 5 The process is the same as in Example 4. The specific operation process is as follows: (1)-(7) are the same as in Example 4.

[0049] The operating conditions of Examples 1-5 are shown in Table 2, and the test results are shown in Table 3.

[0050] Table 2 Operating conditions of Examples 1-5

[0051] Table 3 Test results of Examples 1-5

[0052] Comparative Example 1 1) Sodium and benzene are mixed by high-speed stirring to obtain a sodium dispersion, in which the diameter distribution range of sodium particles is 10-85 μm; the operating conditions are as follows: the mass ratio of sodium to benzene is 1:2, the temperature is 110°C, the time is 20 minutes, and the stirring rate is 3500 r / min; (2) After the inferior diesel feedstock is mixed with the sodium dispersion, it enters two alkali metal treatment reactors arranged in series for reaction, namely the first reactor and the second reactor; the two alkali metal treatment reactors are both stirred tank reactors, and the rotation speed is set to 800r / min; (3) The reaction effluent obtained in step (2) enters a high-speed centrifuge for solid-liquid separation to obtain the final product. The speed of the high-speed centrifuge is 10000 r / min.

[0053] The operating conditions and test results of Comparative Example 1 are shown in Table 4.

[0054] Table 4 Operating conditions and test results of Comparative Example 1

[0055] From the data in the table, it can be seen that the combined process of alkali metal treatment technology and oxidation extraction technology to process low-quality diesel with high sulfur and high nitrogen content can give full play to the advantages of each technology and directly produce ultra-low sulfur and low nitrogen clean diesel.

Claims

1. A method for processing high-sulfur, high-nitrogen low-quality diesel, characterized in that: The method comprises the following steps: (1) In the presence of hydrogen, low-quality diesel feedstock is mixed with alkali metal and then enters the alkali metal treatment reaction zone; (2) The reaction effluent obtained in step (1) enters a separation unit to obtain a liquid phase stream; (3) The liquid phase stream in step (2) is mixed with the oxidant and enters the oxidation reaction zone for reaction; (4) The reaction effluent obtained in step (3) enters the extraction unit, and the final clean diesel product is obtained under the action of the extractant.

2. The method according to claim 1, characterized in that: The low-quality diesel feedstock in step (1) has a sulfur content higher than 6000 μg / g, preferably 8000-15000 μg / g; and a nitrogen content higher than 800 μg / g, preferably 1000-2500 μg / g.

3. The method according to claim 1, characterized in that: The alkali metal in step (1) belongs to Group IA elements in the periodic table, including one or more of lithium, sodium, potassium, rubidium, and cesium, preferably one or more of lithium, sodium and potassium, and more preferably sodium.

4. The method according to claim 1, characterized in that: In step (1), the molar ratio of alkali metal to sulfur content of the low-quality diesel feedstock is 1.5-3.5, preferably 2.0-3.

0.

5. The method according to claim 1, characterized in that: In step (1), the alkali metal is mixed with a dispersion medium to obtain an alkali metal dispersion; the alkali metal dispersion is then mixed with a low-quality diesel feedstock and then enters an alkali metal treatment reaction zone.

6. The method according to claim 5, characterized in that: In step (1), the dispersion medium includes one or more of n-pentadecane, n-hexadecane, benzene, toluene and xylene; and the mass ratio of the alkali metal to the dispersion medium is 1:(1-3).

7. The method according to claim 5, characterized in that: In step (1), the alkali metal and the dispersion medium are mixed by one or more of a high-speed stirring method, a pump jet method, a colloid mill method and an ultrasonic method, preferably a high-speed stirring method, and further preferably a high-speed stirring method under appropriate temperature, time and stirring rate conditions; the temperature is 70-150° C., preferably 100-130° C.; the time is 10-60 min, preferably 20-40 min; the stirring rate is 2000-10000 r / min, preferably 4000-8000 r / min.

8. The method according to claim 5, characterized in that: The diameter distribution range of the alkali metal particles in the alkali metal dispersion in step (1) is 5-100 μm, preferably 10-30 μm.

9. The method according to claim 1, characterized in that: In step (1), the alkali metal treatment reaction zone is provided with 1 to 3 alkali metal treatment reactors, preferably 1 alkali metal treatment reactor; the alkali metal treatment reactor is any one of a kettle reactor, a tubular reactor and a jet reactor, preferably a kettle reactor, and more preferably a kettle reactor with stirring.

10. The method according to claim 1, characterized in that: The operating conditions of the alkali metal treatment reaction zone in step (1) are: reaction temperature 200-380°C, reaction pressure 2.0-20.0 MPa, residence time 5-40 min, hydrogen to oil volume ratio 100-2000 Nm 3 / m 3 The preferred operating conditions are: reaction temperature 280-340°C, reaction pressure 5.0-15.0MPa, residence time 10-25min, hydrogen to oil volume ratio 500-1500Nm 3 / m 3 .

11. The method according to claim 1, characterized in that: The separation unit in step (2) is solid-liquid separation, and at least one of decantation, filtration, centrifugation and gravity sedimentation is used, preferably centrifugation.

12. The method according to claim 1, characterized in that: In step (3), the oxidant comprises at least one of an organic peroxy acid, an inorganic peroxy acid and a peroxy salt, preferably hydrogen peroxide (30 wt%)-organic acid, the organic acid comprises at least one of formic acid, acetic acid and propionic acid; the volume ratio of the organic acid to hydrogen peroxide (30 wt%) is (0.5-4.0):1, preferably (1.5-2.5):

1.

13. The method according to claim 1, characterized in that: The volume ratio of the oxidant in step (3) to the liquid phase flow in step (2) is (0.1-0.3):

1.

14. The method according to claim 1, characterized in that: In step (3), the oxidation reaction zone is provided with 1 to 3 oxidation reactors, preferably 1 oxidation reactor; the oxidation reactor is a kettle reactor and / or a tubular reactor.

15. The method according to claim 1, characterized in that: The operating conditions of the oxidation reaction zone in step (3) are as follows: oxidation temperature is 30-80°C, preferably 40-70°C; oxidation time is 10-50 min, preferably 20-40 min.

16. The method according to claim 1, characterized in that: The reaction effluent obtained in step (3) enters the extraction unit, and the final clean diesel product is obtained under the action of the extractant, which specifically includes the following contents: S1. The reaction effluent obtained in step (3) is divided into two streams, a first stream and a second stream; S2, the first material obtained in step S1 enters the extraction unit, and the final clean diesel product is obtained under the action of the extractant; S3. The second material obtained in step S1 is circulated to the alkali metal treatment reaction zone.

17. The method according to claim 16, characterized in that: In step S1, the mass ratio of the first material to the second material is 1:(0.1-0.3).

18. The method according to claim 16, characterized in that: The second material obtained in step S1 is circulated to the alkali metal treatment reaction zone in the following manner: the second material is mixed with the alkali metal and the dispersion medium to obtain an alkali metal dispersion; or the second material is circulated to any alkali metal treatment reactor in the alkali metal treatment zone.

19. The method according to claim 1, characterized in that: In step (4), the extractant is a polar solvent, including one or more of ethanol, furfural, diethylene glycol, dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF).

20. The method according to claim 1, characterized in that: The volume ratio of the extractant in step (4) to the reaction effluent obtained in step (3) is 0.5-0.

9.

21. The method according to claim 1, characterized in that: The extraction in step (4) adopts single-stage extraction or multi-stage extraction, preferably multi-stage extraction; the multiple extraction stages are any one of primary, secondary, tertiary, quaternary and quinary, preferably tertiary and / or quaternary.

22. The method according to claim 1, characterized in that: The extraction operating conditions in step (4) are as follows: extraction temperature 40-90°C, extraction time 1-10 min.

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