A processing method for high-sulfur, high-nitrogen inferior diesel oil

Abstract

This invention discloses a processing method for high-sulfur, high-nitrogen inferior diesel fuel. The method includes the following steps: (1) In the presence of hydrogen, the inferior diesel fuel is mixed with an alkali metal and then enters an 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 an oxidant and enters an oxidation reaction zone for reaction; (4) The reaction effluent obtained in step (3) enters an extraction unit, and the final clean diesel fuel product is obtained under the action of an extractant. The method uses non-hydrogenation technology to process inferior diesel fuel and can directly produce clean diesel fuel with low sulfur, low nitrogen, and high cetane number.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology and relates to a method for processing high-sulfur and high-nitrogen inferior diesel fuel, specifically a method for processing high-sulfur and high-nitrogen inferior diesel fuel into clean diesel fuel. Background Technology

[0002] my country's main secondary processed diesel fuels are catalytic cracking diesel and delayed coking diesel. With the increasing severity and deterioration of crude oil worldwide, and the deepening of heavy oil conversion, the properties of my country's secondary processed diesel fuels have further deteriorated, primarily manifested in increased sulfur and nitrogen content, and a further decrease in cetane number.

[0003] On the other hand, with increasingly stringent environmental protection requirements, countries worldwide are placing higher demands on vehicle fuels. Since July 1, 2023, my country has fully implemented the National VI emission standard (stage 6b), imposing strict controls on diesel fuel indicators. This includes requiring sulfur content to be reduced to below 0.035 wt%, setting fuel indicator requirements for vehicle lubricity and methyl esters, reducing the polycyclic aromatic hydrocarbon index to 7 wt%, and further increasing the cetane number to 49. The low-quality characteristics of high-sulfur, high-nitrogen diesel fuel create a significant contradiction with the increasingly stringent diesel product standards. Therefore, how to produce clean diesel fuel from high-sulfur, high-nitrogen diesel fuel is a major challenge facing oil refining enterprises.

[0004] To address the above situation, existing technologies generally employ hydrogenation technology to treat high-sulfur and high-nitrogen inferior diesel fuel, producing clean diesel fuel that meets environmental protection requirements. CN106554815A discloses a method for producing clean diesel fuel: high-sulfur and high-nitrogen inferior diesel fuel is mixed with the reaction products of a second hydrogenation reaction zone and reacted in a first hydrogenation reaction zone to obtain a hydrogenation refining reaction product. This product is then separated and fractionated to obtain a refined diesel fuel fraction and a heavy diesel fuel fraction. At least a portion of the heavy diesel fuel fraction and the hydrogen-containing stream are introduced into a second hydrogenation reaction zone, the products of the second hydrogenation reaction zone are introduced into a first hydrogenation reaction zone, and the refined diesel fuel fraction is mixed with the remaining portion of the heavy diesel fuel fraction to obtain clean diesel fuel. The high-sulfur and high-nitrogen inferior diesel fuel contains more than 5000 μg / g of sulfur, more than 700 μg / g of nitrogen, and more than 50% by weight of aromatics.

[0005] CN111286360A discloses a diesel hydrorefining apparatus and method. The method separates diesel feedstock into light and heavy fractions using a pre-fractionation tower. The light fraction contains almost no dibenzothiophene or its derivatives, while the heavy fraction contains almost all of the difficult-to-hydrodesulfurize dibenzothiophene and its derivatives. The sulfides in the light fraction are mainly thiols, disulfides, thiophenes, and benzothiophene sulfides, which can be removed under relatively low reaction severity. The heavy fraction mainly contains sulfides of difficult-to-remove dibenzothiophene sulfides and polycyclic aromatic hydrocarbons. To reduce the sulfur content of the heavy diesel product to below 10 ppm, the content of polycyclic aromatic hydrocarbons is strictly controlled, and the reaction severity is slightly higher than that of a typical diesel hydrorefining reactor.

[0006] However, the hydrogenation technology in the aforementioned patents has strict requirements for reaction conditions, making it difficult to deeply remove nitrogen-containing and sulfur-containing compounds from diesel fuel; moreover, the production cost of hydrogenation technology is high, which limits its further application in the processing of inferior diesel fuel. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for processing high-sulfur, high-nitrogen inferior diesel fuel. The method employs non-hydrogenation technology to process the inferior diesel fuel, directly producing clean diesel fuel with low sulfur, low nitrogen, and high cetane number.

[0008] A method for processing high-sulfur, high-nitrogen, low-quality diesel fuel, the method comprising the following steps:

[0009] (1) In the presence of hydrogen, inferior diesel feedstock is mixed with alkali metal and then enters the alkali metal treatment reaction zone;

[0010] (2) The reaction effluent obtained in step (1) enters the separation unit to obtain a liquid phase stream;

[0011] (3) The liquid phase stream in step (2) is mixed with the oxidant and enters the oxidation reaction zone to react;

[0012] (4) The reaction effluent obtained in step (3) enters the extraction unit and is used by the extractant to obtain the final clean diesel product.

[0013] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the sulfur content of the inferior diesel oil raw material in step (1) is higher than 6000 μg / g, preferably 8000-15000 μg / g; the nitrogen content is higher than 800 μg / g, preferably 1000-2500 μg / g.

[0014] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the alkali metal mentioned 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.

[0015] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the molar ratio of alkali metal to sulfur content of inferior diesel oil raw material in step (1) is 1.5-3.5, preferably 2.0-3.0.

[0016] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel, the alkali metal in step (1) is mixed with the dispersion medium to obtain an alkali metal dispersion; the alkali metal dispersion is then mixed with the inferior diesel raw material and enters the alkali metal treatment reaction zone.

[0017] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, 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).

[0018] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the mixing of alkali metal and dispersion medium in step (1) can be achieved by any of the existing technologies that can achieve liquid-liquid mixing. Specifically, in this invention, one or more of the following methods can be used: high-speed stirring, pump injection, colloid milling, and ultrasonic methods. High-speed stirring is preferred, and it is even more preferred to use high-speed stirring under suitable temperature, time, and stirring rate conditions. The temperature is 70-150℃, preferably 100-130℃; the time is 10-60min, preferably 20-40min; and the stirring rate is 2000-10000r / min, preferably 4000-8000r / min.

[0019] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the diameter distribution range of alkali metal particles in the alkali metal dispersion in step (1) is 5-100 μm, preferably 10-30 μm.

[0020] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, in step (1), 1-3 alkali metal treatment reactors are set in the alkali metal treatment reaction zone, preferably 1 alkali metal treatment reactor; the alkali metal treatment reactor is any one of a batch reactor, a tubular reactor and a jet reactor, preferably a batch reactor, and even more preferably a batch reactor with stirring.

[0021] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the operating conditions of the alkali metal treatment reaction zone in step (1) are: reaction temperature 200-380℃, reaction pressure 2.0-20.0MPa, residence time 5-40min, and hydrogen-to-oil volume ratio 100-2000Nm. 3 / m 3The preferred operating conditions are: reaction temperature 280-340℃, reaction pressure 5.0-15.0 MPa, residence time 10-25 min, and hydrogen-to-oil volume ratio 500-1500 Nm³. 3 / m 3 .

[0022] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the separation unit in step (2) is a solid-liquid separation. There are no restrictions on the method of solid-liquid separation, and any of the existing technologies in the art that can achieve solid-liquid two-phase separation can be used. Specifically, in this invention, solid-liquid separation can be achieved by at least one of decantation, filtration, centrifugation, and gravity sedimentation, with centrifugation being preferred.

[0023] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the oxidant in step (3) includes at least one of organic peroxy acid, inorganic peroxy acid and peroxy salt, preferably hydrogen peroxide (30wt%)-organic acid, the organic acid including at least one of formic acid, acetic acid and propionic acid; the volume ratio of organic acid to hydrogen peroxide (30wt%) is (0.5-4.0):1, preferably (1.5-2.5):1.

[0024] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the volume ratio of oxidant in step (3) to liquid phase stream in step (2) is (0.1-0.3):1.

[0025] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, 1-3 oxidation reactors are set in the oxidation reaction zone in step (3), preferably 1 oxidation reactor; the oxidation reactor can be a reactor that can realize liquid-liquid two-phase reaction in the prior art, such as a batch reactor and / or a tubular reactor.

[0026] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the operating conditions of the oxidation reaction zone in step (3) are as follows: the oxidation temperature is 30-80℃, preferably 40-70℃; the oxidation time is 10-50min, preferably 20-40min.

[0027] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the reaction effluent obtained in step (3) enters the extraction unit, and under the action of the extractant, the final clean diesel oil product is obtained, specifically including the following:

[0028] S1. The reaction effluent obtained in step (3) is divided into two streams: the first material and the second material.

[0029] S2. The first material obtained in step S1 enters the extraction unit and is used by the extractant to obtain the final clean diesel product.

[0030] S3. The second material obtained in step S1 is recycled to the alkali metal treatment reaction zone.

[0031] Furthermore, in step S1, the mass ratio of the first material to the second material is 1:(0.1-0.3).

[0032] Furthermore, the second material obtained in step S1 is recycled to the alkali metal treatment reaction zone in the following ways: the second material is mixed with alkali metal and dispersion medium to obtain an alkali metal dispersion; or the second material is recycled to any alkali metal treatment reactor in the alkali metal treatment zone.

[0033] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, 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).

[0034] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the volume ratio of extractant in step (4) to oil in the reaction effluent obtained in step (3) is 0.5-0.9.

[0035] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the extraction in step (4) adopts single-stage extraction or multi-stage extraction, preferably multi-stage extraction; the number of extraction stages is any one of first-stage, second-stage, third-stage, fourth-stage and fifth-stage, preferably third-stage and / or fourth-stage.

[0036] Furthermore, in the above-mentioned processing method for high-sulfur and high-nitrogen inferior diesel oil, the extraction operation conditions in step (4) are as follows: extraction temperature 40-90℃, extraction time 1-10min.

[0037] During their research, the inventors discovered that for alkali metal treatment technology, molecular structure affects the collision probability between alkali metal molecules and sulfur- and nitrogen-containing compounds, which is a key factor influencing desulfurization and denitrification efficiency. Therefore: First, compared to sulfur-containing compounds, the majority of nitrogen-containing compounds in heavy oil are pyridine and pyrrole nitrogen heterocycles, many of which form very stable structures with aromatic rings, resulting in more complex structures. This leads to a lower collision probability between alkali metal molecules and nitrogen-containing compound molecules, thus the denitrification efficiency is significantly lower than the desulfurization efficiency. Second, the more complex the molecular structure of sulfur-containing compounds, the greater the difficulty of removal. 4,6-Dimethyldibenzothiophene sulfides are the most difficult to remove because the two alkyl groups at the β-position of these sulfides have a strong steric hindrance effect. Therefore, the removal of these sulfides is crucial for achieving low-sulfur diesel production. However, removing nitrogen-containing compounds and 4,6-dimethyldibenzothiophene sulfides using alkali metal treatment technology requires relatively harsh reaction conditions, which contradicts the original intention of alkali metal treatment technology. Therefore, the method of the present invention uses a combination of alkali metal treatment technology and oxidative extraction technology to process high-sulfur and high-nitrogen inferior diesel. 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, which can achieve the production of ultra-low sulfur and low-nitrogen clean diesel.

[0038] Furthermore, in the alkali metal treatment reaction zone, alkali metals react with sulfur-containing compounds to generate alkali metal sulfides such as sodium sulfide. These substances have high melting points (e.g., sodium sulfide has a melting point of 1180°C). Therefore, alkali metal sulfides such as sodium sulfide coat the surface of the alkali metal droplets, making it difficult for the alkali metal inside the droplets to react with the sulfur-containing compounds. Thus, it is necessary to suppress alkali metal aggregation and reduce the size of the alkali metal droplets. In the method of this invention, nitrogen-containing compounds and some sulfur-containing compounds in the oxidation reaction zone are oxidized to obtain nitrogen oxides and sulfur oxides, whose polarity increases exponentially. Therefore, part of the reaction effluent from the oxidation reaction zone is recycled to the alkali metal treatment reaction zone. Based on the principle of "like dissolves like," this effectively suppresses alkali metal aggregation and improves the utilization efficiency of alkali metals.

[0039] Compared with the prior art, the advantages of the present invention are:

[0040] 1. The method of the present invention uses a combination of alkali metal treatment technology and oxidative extraction technology to process high-sulfur and high-nitrogen inferior diesel. The alkali metal treatment reaction zone only needs to complete the removal of most sulfides under mild conditions. Then, the oxidative extraction technology is used to remove nitrogen-containing compounds and 4,6-dimethyldibenzothiophene sulfides, which can achieve the production of ultra-low sulfur and low nitrogen clean diesel.

[0041] 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. Based on the principle of like dissolves like, it can effectively inhibit the aggregation of alkali metals and improve the utilization efficiency of alkali metals. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the process flow for a method of processing high-sulfur, high-nitrogen inferior diesel oil according to the present invention.

[0043] 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 effluent from alkali metal treatment reactor, 9 is separation device, 10 is liquid stream, 11 is solid stream, 12 is oxidant, 13 is oxidation reactor, 14 is extractant, 15 is effluent from oxidation reactor, 16 is raffinate, 17 is final clean diesel product, and 18 is extraction device.

[0044] Figure 2 This is a schematic diagram of the process flow for another method of processing high-sulfur, high-nitrogen inferior diesel oil according to the present invention.

[0045] 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 effluent from alkali metal treatment reactor, 9 is separation device, 10 is liquid phase stream, 11 is solid phase stream, 12 is oxidant, 13 is oxidation reactor, 14 is extractant, 15 is first stream, 16 is raffinate, 17 is final clean diesel product, 18 is extraction device, and 19 is second stream. Implementation

[0046] The method provided by the present invention will now be described with reference to the accompanying drawings.

[0047] like Figure 1 As shown, alkali metal 3 and additive 4 enter a mixing device to obtain alkali metal dispersion 6, which is then mixed with hydrogen 1 and inferior diesel feedstock 2 and then enters alkali metal treatment reactor 7 for reaction. The reaction effluent 8 enters a separation device 9 for solid-liquid separation to obtain liquid stream 10 and solid stream 11. Liquid stream 10 and oxidant 12 enter oxidation reactor 13 for oxidation reaction. The reaction effluent 15 enters an extraction device 18, where, under the action of extractant 14, the final clean diesel product 17 and raffinate 16 are obtained.

[0048] like Figure 2As shown, alkali metal 3 and additive 4 enter the mixing device to obtain alkali metal dispersion 6, which is then mixed with hydrogen 1 and inferior diesel feedstock 2 and enters the alkali metal treatment reactor 7 for reaction. The reaction effluent 8 enters the separation device 9 for solid-liquid separation to obtain liquid stream 10 and solid stream 11. The liquid stream and oxidant 12 enter the oxidation reactor 13 for oxidation reaction. The reaction effluent is divided into two streams: first material 15 and second material 19. The first material 15 enters the extraction unit and then the extraction device 18. Under the action of the extractant 14, the final clean diesel product 17 and raffinate 16 are obtained. The second material 19 is recycled to the alkali metal treatment reaction zone.

[0049] The following examples and comparative examples will further illustrate the method provided by the present invention, but are not intended to limit the invention.

[0050] The properties of the inferior diesel feedstock used in the examples and comparative examples are shown in Table 1.

[0051] Table 1 Properties of Inferior Diesel Feedstock

[0052]

[0053] Example 1

[0054] Example 1 uses Figure 1 The process flow is shown below. The specific operation procedure is as follows:

[0055] (1) Sodium and benzene were mixed by high-speed stirring to obtain a sodium dispersion. The sodium particle diameter distribution range in the sodium dispersion was 10-85 μm. The operating conditions were as follows: the mass ratio of sodium to benzene was 1:2, the temperature was 110℃, the time was 20 min, and the stirring rate was 3500 r / min.

[0056] (2) The inferior diesel feedstock is mixed with sodium dispersion and then fed into the alkali metal treatment reactor for reaction; the alkali metal treatment reactor is a stirred tank reactor with a rotation speed of 800 r / min;

[0057] (3) The reaction effluent obtained in step (2) is fed into a high-speed centrifuge for solid-liquid separation to obtain a liquid phase stream. The speed of the high-speed centrifuge is 10000 r / min.

[0058] (4) The liquid phase stream in step (3) is mixed with hydrogen peroxide (30wt%) and formic acid and then fed into the oxidation reactor for reaction; the volume ratio of formic acid to hydrogen peroxide (30wt%) is 2.5:1; the oxidation reactor is a stirred tank reactor with a rotation speed of 800 r / min.

[0059] (5) The reaction effluent obtained in step (4) enters the extraction unit and is subjected to three-stage extraction with furfural as the extractant to obtain the final clean diesel product.

[0060] Example 2

[0061] In Example 2, compared to Example 1, sodium was not synthesized into a sodium dispersion but was directly mixed with low-quality diesel feedstock. The specific operation process is as follows:

[0062] (1) The inferior diesel feedstock is mixed with sodium and then fed into the alkali metal treatment reactor for reaction; the alkali metal treatment reactor is a stirred tank reactor with a rotation speed of 2500 r / min;

[0063] (2) The reaction effluent obtained in step (1) is fed into a high-speed centrifuge for solid-liquid separation to obtain a liquid phase stream. The speed of the high-speed centrifuge is 10000 r / min.

[0064] (3) The liquid phase stream in step (2) is mixed with hydrogen peroxide (30wt%) and formic acid and then fed into the oxidation reactor for reaction; the volume ratio of formic acid to hydrogen peroxide (30wt%) is 1.5:1; the oxidation reactor is a stirred tank reactor with a rotation speed of 800 r / min.

[0065] (4) The reaction effluent obtained in step (3) enters the extraction unit and is subjected to three-stage extraction with furfural as the extractant to obtain the final clean diesel product.

[0066] Example 3

[0067] Compared with Example 1, Example 3 adds a process flow of material recycling to the alkali metal treatment reaction zone. The specific operation process is as follows:

[0068] (1) Potassium and toluene were mixed by high-speed stirring to obtain a potassium dispersion. The potassium particle diameter distribution range in the potassium dispersion was 5-45 μm. The operating conditions were as follows: the mass ratio of potassium to toluene was 1:2, the temperature was 120℃, the time was 30 min, and the stirring rate was 5000 r / min.

[0069] (2) The inferior diesel feedstock is mixed with potassium dispersion and then fed into the alkali metal treatment reactor for reaction; the alkali metal treatment reactor is a stirred tank reactor with a rotation speed of 800 r / min.

[0070] (3) The reaction effluent obtained in step (2) is fed into a high-speed centrifuge for solid-liquid separation to obtain a liquid phase stream. The speed of the high-speed centrifuge is 10000 r / min.

[0071] (4) The liquid phase stream in step (3) is mixed with hydrogen peroxide (30wt%) and formic acid and then fed into the oxidation reactor for reaction; the volume ratio of formic acid to hydrogen peroxide (30wt%) is 2.5:1; the oxidation reactor is a stirred tank reactor with a rotation speed of 800 r / min.

[0072] (5) The reaction effluent obtained in step (4) is divided into two streams, the first material and the second material, with a mass ratio of 1:0.1;

[0073] (6) The first material obtained in step (5) enters the extraction unit and is subjected to four-stage extraction with furfural as the extractant to obtain the final clean diesel product.

[0074] (7) The second material obtained in step (5) is recycled to the alkali metal treatment reactor and fed together with the inferior diesel feedstock.

[0075] Example 4

[0076] Example 4 adopts Figure 2 The process flow is shown below. The specific operation procedure is as follows:

[0077] (1) Potassium and n-hexadecane were mixed by high-speed stirring to obtain a potassium dispersion. The potassium particle diameter distribution range in the potassium dispersion was 5-25 μm. The operating conditions were as follows: the mass ratio of potassium to n-hexadecane was 1:1, the temperature was 125℃, the time was 40 min, and the stirring rate was 7500 r / min.

[0078] (2)-(4) Same as Example 3;

[0079] (5) The reaction effluent obtained in step (4) is divided into two streams, the first material and the second material, with a mass ratio of 1:0.3;

[0080] (6) Same as Example 3;

[0081] (7) The second material obtained in step (5) is recycled to the alkali metal treatment reaction zone and mixed with potassium and n-hexadecane to obtain a potassium dispersion.

[0082] Example 5

[0083] The process flow is the same as in Example 4. The specific operation procedure is as follows:

[0084] (1)-(7) Same as Example 4.

[0085] The operating conditions for Examples 1-5 are shown in Table 2, and the experimental results are shown in Table 3.

[0086] Table 2 Operating conditions for Examples 1-5

[0087]

[0088] Table 3. Test results of Examples 1-5

[0089]

[0090] Comparative Example 1

[0091] 1) Sodium and benzene were mixed by high-speed stirring to obtain a sodium dispersion. The sodium particle diameter distribution range in the sodium dispersion was 10-85 μm. The operating conditions were as follows: the mass ratio of sodium to benzene was 1:2, the temperature was 110℃, the time was 20 min, and the stirring rate was 3500 r / min.

[0092] (2) The inferior diesel feedstock is mixed with sodium dispersion and then fed into two alkali metal processing reactors set in series for reaction, namely the first reactor and the second reactor; both alkali metal processing reactors are stirred tank reactors with a rotation speed of 800 r / min.

[0093] (3) The reaction effluent obtained in step (2) is fed into a high-speed centrifuge for solid-liquid separation to obtain the final product. The speed of the high-speed centrifuge is 10000 r / min.

[0094] The operating conditions and test results of Comparative Example 1 are shown in Table 4.

[0095] Table 4 Operating conditions and test results of Comparative Example 1

[0096]

[0097] The data in the table shows that using a combination of alkali metal treatment and oxidative extraction technologies to process high-sulfur and high-nitrogen inferior diesel can fully leverage 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 oil, characterized in that: The method includes the following steps: (1) In the presence of hydrogen, inferior 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 the 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 to react; (4) The reaction effluent obtained in step (3) enters the extraction unit and is used by the extractant to obtain the final clean diesel product; Operating conditions in the alkali metal treatment reaction zone in step (1): reaction temperature 280-340℃, residence time 5-40min; The reaction effluent obtained in step (3) enters the extraction unit, where it is treated with an extractant to obtain the final clean diesel product, which includes the following: S1. The reaction effluent obtained in step (3) is divided into two streams: the first material and the second material. S2. The first material obtained in step S1 enters the extraction unit and is used by the extractant to obtain the final clean diesel product. S3. The second material obtained in step S1 is recycled to the alkali metal treatment reaction zone. In step S1, the mass ratio of the first material to the second material is 1:(0.1-0.3). The inferior diesel feedstock mentioned in step (1) has a sulfur content higher than 6000 μg / g and a nitrogen content higher than 800 μg / g; The alkali metal mentioned in step (1) includes one or more of lithium, sodium, potassium, rubidium, and cesium; In step (1), the molar ratio of alkali metals to sulfur content in low-quality diesel feedstock is 1.5-3.5; The alkali metal in step (1) is mixed with the dispersion medium to obtain an alkali metal dispersion; the alkali metal dispersion is then mixed with inferior diesel feedstock and then enters the alkali metal treatment reaction zone. In step (1), the dispersion medium includes 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).

2. The method according to claim 1, characterized in that: The inferior diesel feedstock mentioned in step (1) has a sulfur content of 8000-15000 μg / g and a nitrogen content of 1000-2500 μg / g.

3. The method according to claim 1, characterized in that: The alkali metals mentioned in step (1) include one or more of lithium, sodium and potassium.

4. The method according to claim 1, characterized in that: The alkali metal mentioned in step (1) is sodium.

5. The method according to claim 1, characterized in that: In step (1), the molar ratio of alkali metal to sulfur content of inferior diesel feedstock is 2.0-3.

0.

6. The method according to claim 1, characterized in that: In step (1), the alkali metal is mixed with the dispersion medium using one or more of the following methods: high-speed stirring, pump injection, colloid milling, and ultrasonic mixing.

7. The method according to claim 6, characterized in that: In step (1), the alkali metal and the dispersion medium are mixed by high-speed stirring.

8. The method according to claim 6, characterized in that: In step (1), the alkali metal and the dispersion medium are mixed under suitable temperature, time and stirring rate conditions using a high-speed stirring method. The temperature is 70-150℃, the time is 10-60min, and the stirring rate is 2000-10000r / min.

9. The method according to claim 8, characterized in that: In step (1), the alkali metal and the dispersion medium are mixed under suitable temperature, time and stirring rate conditions using a high-speed stirring method. The temperature is 100-130℃, the time is 20-40min, and the stirring rate is 4000-8000r / min.

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

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

12. The method according to claim 1, characterized in that: In step (1), 1-3 alkali metal treatment reactors are set up in the alkali metal treatment reaction zone; the alkali metal treatment reactor is any one of a batch reactor, tubular reactor and jet reactor.

13. The method according to claim 12, characterized in that: In step (1), one alkali metal treatment reactor is set up in the alkali metal treatment reaction zone; the alkali metal treatment reactor is a batch reactor.

14. The method according to claim 12, characterized in that: The alkali metal treatment reactor mentioned in step (1) is a stirred tank reactor.

15. The method according to claim 1, characterized in that: Operating conditions in the alkali metal treatment reaction zone in step (1): reaction pressure 2.0-20.0 MPa, hydrogen-to-oil volume ratio 100-2000 Nm³ 3 / m 3 .

16. The method according to claim 15, characterized in that: Operating conditions in the alkali metal treatment reaction zone in step (1): reaction pressure 5.0-15.0 MPa, residence time 10-25 min, hydrogen-to-oil volume ratio 500-1500 Nm³. 3 / m 3 .

17. The method according to claim 1, characterized in that: In step (2), the separation unit is a solid-liquid separation, which employs at least one of the following methods: decantation, filtration, centrifugation, and gravity sedimentation.

18. The method according to claim 17, characterized in that: In step (2), the separation unit is a solid-liquid separation unit, which uses centrifugal separation.

19. The method according to claim 1, characterized in that: The oxidant in step (3) includes at least one of organic peroxy acid, inorganic peroxy acid and peroxy salt.

20. The method according to claim 19, characterized in that: In step (3), the oxidant is 30wt% hydrogen peroxide-organic acid, and the organic acid includes at least one of formic acid, acetic acid and propionic acid; the volume ratio of organic acid to 30wt% hydrogen peroxide is (0.5-4.0):

1.

21. The method according to claim 20, characterized in that: In step (3), the volume ratio of organic acid to 30wt% hydrogen peroxide is (1.5-2.5):

1.

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

1.

23. The method according to claim 1, characterized in that: In step (3), 1-3 oxidation reactors are set up in the oxidation reaction zone; the oxidation reactors are batch reactors and / or tubular reactors.

24. The method according to claim 23, characterized in that: In step (3), one oxidation reactor is set up in the oxidation reaction zone.

25. The method according to claim 1, characterized in that: The operating conditions for the oxidation reaction zone in step (3) are as follows: oxidation temperature is 30-80℃; oxidation time is 10-50min.

26. The method according to claim 25, characterized in that: The operating conditions for the oxidation reaction zone in step (3) are as follows: oxidation temperature is 40-70℃; oxidation time is 20-40min.

27. The method according to claim 1, characterized in that: The second material obtained in step S1 is recycled to the alkali metal treatment reaction zone in the following way: the second material is mixed with alkali metal and dispersion medium to obtain alkali metal dispersion.

28. 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 and N,N-dimethylformamide.

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

9.

30. The method according to claim 1, characterized in that: In step (4), extraction can be performed using single-stage extraction or multi-stage extraction.

31. The method according to claim 30, characterized in that: In step (4), multi-stage extraction is used; the number of stages in the multi-stage extraction is any one of two, three, four or five stages.

32. The method according to claim 30, characterized in that: The multi-stage extraction stage mentioned in step (4) is three and / or four stages.

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

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