A method for hydroconversion of catalytic cracked diesel fuel

Abstract

This invention discloses a method for hydroconversion of catalytic cracking diesel, the method comprising the following steps: (1) catalytic cracking diesel is fractionated to obtain light fraction and heavy fraction of catalytic cracking diesel; (2) the heavy fraction of catalytic cracking diesel first enters the hydrorefining reaction zone and is contacted with the hydrorefining catalyst in the presence of hydrogen to carry out the hydrorefining reaction. When the bed temperature of the hydrorefining reaction zone increases by 40°C to 100°C compared with the inlet temperature of the hydrorefining reaction zone, the light fraction of catalytic cracking diesel is introduced and mixed with the heavy fraction of catalytic cracking diesel after the hydrorefining reaction to continue the hydrorefining reaction; (3) the stream after the hydrorefining reaction in step (2) enters the hydrocracking reaction zone and is contacted with the hydrocracking catalyst to carry out the hydrocracking reaction; (4) the stream obtained in step (3) is separated to obtain light naphtha, heavy naphtha and tail oil. The heavy naphtha is extracted with aromatics to obtain BTX. The method can effectively reduce the loss of aromatics in catalytic cracked diesel during the hydrogenation process and increase the content of BTX components in the hydrogenation products.

Description

Technical Field

[0001] This invention relates to a method for hydroconversion of catalytic cracked diesel, and more specifically to a method for hydroconverting catalytic cracked diesel to produce more BTX. Background Technology

[0002] Light aromatic hydrocarbons such as benzene, toluene, and xylene are important basic chemical raw materials. With industrial development and improved living standards, the synthetic fiber, synthetic plastics, and synthetic rubber industries have grown rapidly, leading to a year-on-year increase in demand for bicyclic aromatic hydrocarbons (BTX), resulting in a supply shortage. Using hydrocracking to convert bicyclic aromatic hydrocarbons in catalytic diesel into light aromatic hydrocarbons (such as BTX) is an ideal way to address the diesel surplus and low-carbon aromatic hydrocarbon shortage. During hydrocracking, bicyclic aromatic hydrocarbons first undergo partial hydrogenation to form tetrahydronaphthalene compounds, followed by ring-opening and side-chain breaking to generate short-chain BTX aromatic hydrocarbons.

[0003] CN201510761954.9 discloses a method for grading hydrocracking catalysts and a catalytic diesel hydroconversion process. The grading method includes the following steps: dividing the hydrocracking reactor into 2-8 equal reaction zones along the material flow direction; each reaction zone is loaded with a hydrocracking catalyst containing a regenerator; based on the weight of the hydrocracking catalyst, the regenerator content in the hydrocracking catalyst is 10wt%-90wt%, with the regenerator content gradually increasing in each reaction zone along the material flow direction. This invention also provides a catalytic diesel hydroconversion process incorporating this hydrocracking catalyst grading method. By grading and loading catalysts with different reactivity within the cracking reactor, the hydrogenation selectivity of diesel / gasoline components during the conversion process is improved, and the yield of high-octane gasoline products is increased.

[0004] CN201711118958.0 discloses a method for producing high-quality gasoline and diesel from catalytic diesel, comprising the following steps: (1) high-aromatic catalytic diesel is mixed with circulating hydrogen and enters the I hydrorefining reaction zone for reaction; (2) the generated oil obtained in step (1) is mixed with circulating hydrogen and enters the II hydrorefining reaction zone for reaction, the reaction temperature being 30~120℃ higher than that of the I hydrorefining reaction zone; (3) the generated oil obtained in step (2) is cut into light components and heavy components; (4) the light components obtained in step (3) are mixed with circulating hydrogen and enter the hydrorefining reaction zone, the generated oil is separated to obtain gasoline fraction and diesel fraction; (5) the heavy components obtained in step (3) are mixed with circulating hydrogen and enter the hydroconversion reaction zone, the generated oil is separated by a separation system to obtain gas, gasoline and diesel fractions; (6) the gasoline obtained in step (4) is mixed with the gasoline obtained in step (5) to obtain qualified gasoline product, the diesel obtained in step (4) is mixed with the diesel obtained in step (5) to obtain qualified diesel product. This method can produce high-quality fuel oil products, and compared with other technologies, it has the advantages of low chemical hydrogen consumption and flexible product structure adjustment.

[0005] CN201711118979.2 discloses a method for catalytic diesel hydroconversion, comprising the following steps: (1) high-aromatic catalytic diesel is mixed with recycled hydrogen and enters the I hydrorefining reaction zone for reaction; (2) the product oil obtained in step (1) is mixed with recycled hydrogen and enters the II hydrorefining reaction zone for further reaction, the reaction temperature being 30~120℃ higher than that of the I hydrorefining reaction zone, and the liquid hourly space velocity being 0.2~1.5h-1 lower than that of the I hydrorefining reaction zone; (3) the product oil obtained in step (2) is mixed with recycled hydrogen and enters the hydrocracking reaction zone for hydrocarbon hydroconversion reaction; (4) the product oil obtained in step (3) is separated and fractionated by a separation and distillation system to obtain gas, light naphtha, heavy naphtha, and diesel fractions, with part of the diesel being recycled back to the II hydrorefining reaction zone and part of the diesel exiting the unit. The catalytic diesel hydroconversion method provided by this method can effectively increase the production of aromatics.

[0006] CN201811264072.1 This invention discloses a method for producing high-quality gasoline by catalytic diesel hydroconversion, comprising the following steps: (1) High-aromatic catalytic diesel is mixed with recycled hydrogen and enters a hydrorefining reaction zone for reaction, wherein the hydrorefining reaction zone is provided with at least two catalyst beds, and the sulfidation degree of the catalyst decreases along the flow direction; (2) The product oil obtained in step (1) enters a hydrocracking reaction zone and contacts at least two sulfidated hydrocracking catalysts to carry out a ring-opening conversion reaction of polycyclic aromatic hydrocarbons; (3) The product oil obtained in step (2) is separated by a separation system to obtain gas, gasoline, and diesel fractions. The method solves the problem of long initial adjustment period and low octane number of the main target product, gasoline fraction, during the production process.

[0007] CN201611045476.2 discloses a method for processing catalytic diesel fuel. The method involves separating the catalytic diesel feedstock into light and heavy components; the light components undergo hydrorefining and hydromodification reactions to obtain gasoline and diesel components; the heavy components undergo hydrorefining and hydroconversion to obtain gasoline and diesel components; the two gasoline and diesel components are mixed to obtain a gasoline product, and the two diesel components are mixed to obtain a diesel product. This invention, through a rational separation and processing procedure, allows for selective processing of different types of feedstocks, thereby enabling the efficient production of qualified gasoline and diesel products from inferior catalytic cracking diesel fuel.

[0008] CN201310540464.7 discloses a method for the hydroconversion of catalytic cracked diesel. Catalytic diesel is mixed with hydrogen and first fed into a hydrorefining reactor for hydrorefining. The effluent from the hydrorefining reaction directly enters a hydrocracking reactor, where it reacts with a graded catalyst bed. The hydrocracking reactor contains at least two cracking catalyst beds, and the hydrocracking catalyst activity decreases according to the flow direction of the reactants. The hydrocracking effluent is then separated and fractionated to obtain naphtha and diesel. This method can reduce excessive hydrogenation and secondary cracking of cracked naphtha while ensuring the effectiveness of diesel hydrocracking, thereby reducing chemical hydrogen consumption and improving the octane number and liquid yield of naphtha.

[0009] CN201811264066.6 discloses a method for catalytic diesel hydroconversion to maximize the production of aromatics, comprising the following steps: (1) high-aromatic catalytic diesel is mixed with recycled hydrogen and enters a hydrorefining reaction zone for reaction, wherein the hydrorefining reaction zone is provided with at least two catalyst beds, and the sulfidation degree of the catalyst decreases along the flow direction; (2) the product oil obtained in step (1) enters a hydrocracking reaction zone and contacts at least two sulfidation state hydrocracking catalysts to carry out a ring-opening conversion reaction of polycyclic aromatics; (3) the product oil obtained in step (2) is separated by a separation system to obtain gas, gasoline and diesel fractions, and all diesel fractions are recycled back to the hydrorefining reaction zone; (4) the naphtha obtained in step (3) enters an aromatics extraction unit and is extracted by solvent to obtain BTX product. This invention solves the problem of long initial adjustment cycle and low octane number of gasoline fraction, the main target product, in the application of the technology by using hydrorefining catalysts with different sulfidation degrees to balance the initial activity of the catalyst.

[0010] The catalytic diesel hydroconversion process first involves hydrogenating the catalytic diesel to convert polycyclic aromatic hydrocarbons (PAHs) into monocyclic aromatic hydrocarbons (MAHs), followed by ring-opening and cracking reactions. Current technologies generally suffer from low BTX (bicyclic aromatic hydrocarbon) yields in catalytic diesel hydroconversion. Developing a catalytic diesel hydroconversion process with high BTX yields is a pressing issue that needs to be addressed. Summary of the Invention

[0011] Through in-depth research, the inventors discovered that the hydrogenation saturation of aromatics at lower reaction temperatures is mainly influenced by kinetic reactions. Specifically, in the kinetic reaction zone, the aromatic saturation rate gradually increases with increasing reaction temperature. This process also exacerbates the conversion of monocyclic aromatics to cycloalkanes, leading to aromatic loss. At higher reaction temperatures, the saturation is mainly influenced by thermodynamic reactions. Specifically, in the thermodynamic reaction zone, the aromatic saturation rate gradually decreases with increasing reaction temperature. While this process effectively reduces aromatic loss, it also inhibits the conversion of polycyclic aromatics to monocyclic aromatics, resulting in an increase in the polycyclic aromatic content in the hydrorefined product. Since polycyclic aromatics are difficult to ring-open and crack, this process also inhibits the hydrocracking of monocyclic aromatics, leading to a decrease in the BTX component content in the product. To address the shortcomings of existing technologies, this invention provides a method for the hydroconversion of catalytic cracking diesel fuel. This method can effectively reduce aromatic loss during the hydrogenation process of catalytic cracking diesel fuel and increase the BTX component content in the hydrogenation product.

[0012] A method for hydroconversion of catalytic cracked diesel fuel, the method comprising the following steps:

[0013] (1) Catalytic cracked diesel is fractionated to obtain light fraction and heavy fraction of catalytic cracked diesel;

[0014] (2) The heavy fraction of catalytic cracking diesel first enters the hydrorefining reaction zone and comes into contact with the hydrorefining catalyst in the presence of hydrogen to carry out the hydrorefining reaction. When the bed temperature of the hydrorefining reaction zone increases by 40°C to 100°C compared with the inlet temperature of the hydrorefining reaction zone, preferably by 60°C to 80°C, the light fraction of catalytic cracking diesel is introduced into the bed position and mixed with the heavy fraction of catalytic cracking diesel after the hydrorefining reaction to continue the hydrorefining reaction.

[0015] (3) The stream after the hydrorefining reaction in step (2) enters the hydrocracking reaction zone and comes into contact with the hydrocracking catalyst to carry out the hydrocracking reaction;

[0016] (4) The stream obtained in step (3) is separated to obtain light naphtha, heavy naphtha and tail oil. The heavy naphtha is extracted with aromatics to obtain BTX.

[0017] In the method of the present invention, the initial boiling point of the catalytic cracked diesel oil in step (1) is generally 60℃~220℃, preferably 170℃~210℃; the density is generally 0.90g / cm³. -3 ~0.99 g / cm -3 The nitrogen content is generally 0.03m%~0.2m%; the aromatic content is generally 50m%~90m%, preferably 65m%~85m%.

[0018] In the method of the present invention, the final boiling point of the light distillate of the catalytic cracked diesel in step (1) is 210℃~240℃, preferably 220℃~230℃; the mass content of bicyclic aromatic hydrocarbons is 3wt%~15wt%, preferably 5wt%~10wt%.

[0019] In the method of the present invention, the reaction conditions in the hydrorefining reaction zone in step (2) are generally: reaction pressure 3.0–15.0 MPa, preferably 5.0–12.0 MPa; liquid hourly space velocity 0.1–15.0 h⁻¹. -1 Preferably 0.2–3.0 h -1 .

[0020] The hydrorefining catalyst in step (2) of the present invention has the following properties: the hydrorefining catalyst includes a support and a hydrorefining active metal; wherein the support is an inorganic refractory oxide, generally selected from one or more of alumina, amorphous aluminum silicate, silica, or titanium dioxide; the hydrorefining active metal includes Group VIB and / or Group VIII metal components. In the hydrorefining catalyst, Group VIB components are selected from tungsten and / or molybdenum, with a content of 5%–30% by mass of the oxide in the catalyst, preferably 10%–20%; Group VIII components are selected from nickel and / or cobalt, with a content of 1%–6% by mass of the oxide in the catalyst, preferably 1.5%–5%.

[0021] In the method of this invention, step (2) divides the hydrorefining reaction zone into an upper low-temperature hydrorefining reaction zone and a lower high-temperature hydrorefining reaction zone, based on the location where the light fraction of catalytic cracked diesel is introduced. The average reaction temperature of the low-temperature hydrorefining reaction zone is 300℃~360℃, preferably 330℃~350℃, and the average reaction temperature of the high-temperature hydrorefining reaction zone is 370℃~420℃, preferably 380℃~400℃. Preferably, the average reaction temperature of the high-temperature hydrorefining reaction zone is 20℃~100℃ higher than that of the low-temperature hydrorefining reaction zone, preferably 30℃~50℃ higher.

[0022] In the method of this invention, the hydrocracking catalyst in step (3) typically comprises a cracking component, a hydrogenation component, and a binder. The catalyst can be a commercially available product or prepared according to existing technology. The cracking component is a Y-type molecular sieve. The binder is typically alumina or silica. The hydrogenation active metal component is a Group VIB and / or Group VIII metal component, such as one or more of Co, Ni, Mo, and W. Based on the weight of the hydrocracking catalyst, the hydrogenation component content is typically 3–20 wt%, and the cracking component content is 30%–80 wt%, preferably 40%–70 wt%.

[0023] In step (3) of the above method, the reaction conditions in the hydrocracking reaction zone are generally: reaction pressure 3.0–15.0 MPa, preferably 5.0–12.0 MPa; liquid hourly space velocity 0.1–15.0 h⁻¹. -1 Preferably 0.2–3.0 h -1 The average reaction temperature in the hydrocracking reaction zone is 300℃~450℃, preferably 380℃~420℃.

[0024] In step (3) of the above method, the aromatic extraction can be carried out using existing technology. Conventional aromatic extraction methods mainly include liquid-liquid extraction or extractive distillation. This invention selects liquid-liquid extraction, and the extraction solvent is one or more of di(tri)ethylene glycol, tetraethylene glycol, sulfolane, N-methylpyrrolidone, and dimethyl sulfoxide. The extraction temperature is 20℃~200℃, preferably 50℃~150℃; the solvent: heavy naphtha mass ratio is 1:1~8:1, preferably 3:1~5:1; the pressure is 0MPa~2MPa, preferably 0.1~0.5MPa.

[0025] Compared with the prior art, the advantages of the catalytic cracking diesel hydroconversion method of the present invention are as follows:

[0026] In catalytic diesel, polycyclic aromatic hydrocarbons (PAHs) first enter the kinetic reaction zone. As the reaction temperature gradually increases, the conversion of PAHs to monocyclic aromatic hydrocarbons (MOHs) is promoted. When the reaction temperature reaches the thermodynamic reaction zone temperature range, MOHs are introduced. While carrying out the hydrodenitrification reaction, the hydrogenation saturation of MOHs is reduced, effectively reducing the loss of aromatic hydrocarbons during the hydrorefining process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the principle flow of a catalytic cracking diesel hydroconversion method used in an embodiment of the present invention.

[0028] Wherein, 1 is catalytic cracked diesel, 2 is fractionation tower, 3 is heavy fraction of catalytic cracked diesel, 4 is light fraction of catalytic cracked diesel, 5 is hydrogen, 6 is hydrorefining reaction zone, 7 is hydrorefining reaction effluent, 8 is hydrocracking reaction zone, 9 is hydrocracking reaction effluent, 10 is separator, 11 is the separated gas phase, 12 is the separated liquid phase, 13 is fractionation tower, 14 is gas, 15 is light naphtha, 16 is heavy naphtha, 17 is tail oil, 18 is aromatics extraction zone, 19 is BTX component, and 20 is raffinate. Detailed Implementation

[0029] The following examples further illustrate the function and effect of the present invention, but the following examples do not constitute a limitation on the method of the present invention. Unless otherwise specified, all percentages in this application are mass percentages.

[0030] like Figure 1The catalytic cracked diesel 1 shown enters the fractionation tower 2 to separate into catalytic cracked diesel heavy fraction 3 and catalytic cracked diesel light fraction 4. The catalytic cracked diesel heavy fraction 3 is mixed with hydrogen 5 and enters the hydrorefining reaction zone 6 from the top. The catalytic cracked diesel light fraction enters the hydrorefining reaction zone 6 from the middle. The hydrorefining reaction effluent 7 enters the hydrocracking reaction zone 8. The hydrocracking reaction effluent 9 enters the separator 10. The separated gas phase 11 is recycled. The liquid phase 12 enters the fractionation tower 13 to separate into gas 14, light naphtha 15, heavy naphtha 16 and tail oil 17. The heavy naphtha 16 enters the aromatics extraction zone 18 to separate into BTX component 19 and raffinate oil 20.

[0031] In this embodiment of the invention, the catalyst used in the hydrorefining reaction zone is FF-66 hydrorefining catalyst, with a composition of 22 wt% MoO3, 5 wt% NiO, and the balance being alumina. The catalyst used in the hydrocracking reaction zone is FC-70A hydrocracking catalyst, with a composition of 12 wt% MoO3, 3 wt% NiO, 60 wt% Y-type molecular sieve, and the balance being alumina. The catalysts are all manufactured by Sinopec Catalyst Co., Ltd.

[0032] In the embodiments and comparative examples of the present invention, the process conditions using sulfolane as the extraction solvent are as follows: extraction temperature 80°C; solvent: heavy naphtha mass ratio of 4:1; pressure of 0.3 MPa.

[0033] Table 1 shows the properties of catalytic diesel oil, Table 2 shows the reaction conditions and results of the examples, and Table 3 shows the reaction conditions and results of the comparative examples.

[0034] Table 1

[0035]

[0036] Table 2

[0037]

[0038] Comparative Example 1

[0039] Catalytic cracked diesel first enters the hydrorefining reaction zone for hydrosaturation reaction. The hydrorefining reaction zone is filled with FF-66 hydrorefining catalyst. The effluent from the hydrorefining reaction zone enters the hydrocracking reaction zone for hydrocracking reaction. The hydrocracking reaction zone is filled with FC-70A hydrocracking catalyst.

[0040] Table 3

[0041]

[0042] As can be seen from the above examples, the method of the present invention can effectively improve the BTX yield in catalytic diesel products.

Claims

1. A catalytic cracking gas oil hydroconversion process characterized in that: The method comprises the following steps: (1) obtaining a catalytic cracking diesel light fraction and a catalytic cracking diesel heavy fraction after fractionation treatment of catalytic cracking diesel; the catalytic cracking diesel light fraction has a final boiling point of 210-240 DEG C; the mass content of bicyclic aromatic hydrocarbons is 3-15 wt%; (2) the catalytic cracking diesel heavy fraction first enters a hydrofining reaction zone to contact with a hydrofining catalyst to perform a hydrofining reaction in the presence of hydrogen; the catalytic cracking diesel light fraction is introduced into the hydrofining reaction zone at a bed layer position where the bed layer temperature of the hydrofining reaction zone is increased by 40-100 DEG C compared with the inlet temperature of the hydrofining reaction zone to mix with the catalytic cracking diesel heavy fraction after the hydrofining reaction to continue the hydrofining reaction; (3) the stream after the hydrofining reaction in step (2) enters a hydrocracking reaction zone to contact with a hydrocracking catalyst to perform a hydrocracking reaction; (4) the stream obtained in step (3) is separated to obtain light naphtha, heavy naphtha and tail oil, and the heavy naphtha is extracted to obtain BTX; In step (2), the hydrofining reaction zone is divided into a low-temperature hydrofining reaction zone in the upper part and a high-temperature hydrofining reaction zone in the lower part based on the position where the catalytic cracking diesel light fraction is introduced; the average reaction temperature of the low-temperature hydrofining reaction zone is 300-360 DEG C, and the average reaction temperature of the high-temperature hydrofining reaction zone is 370-420 DEG C; the average reaction temperature of the high-temperature hydrofining reaction zone is higher than that of the low-temperature hydrofining reaction zone by 20-100 DEG C.

2. The method of claim 1, wherein: In step (2), the catalytic cracking diesel light fraction is introduced into the hydrofining reaction zone at a bed layer position where the bed layer temperature of the hydrofining reaction zone is increased by 60-80 DEG C compared with the inlet temperature of the hydrofining reaction zone to mix with the catalytic cracking diesel heavy fraction after the hydrofining reaction to continue the hydrofining reaction.

3. The method of claim 1, wherein: The initial boiling point of the catalytically cracked diesel in step (1) is 60°C to 220°C; the density is 0.90 g / cm -3 ~0.99 g / cm -3 ; the nitrogen content is 0.03 m% to 0.2 m%; and the aromatic hydrocarbon content is 50 m% to 90 m%.

4. The method of claim 3, wherein: In step (1), the initial boiling point of the catalytic cracking diesel is 170-210 DEG C; the aromatic hydrocarbon content is 65-85 m%.

5. The method of claim 1, wherein: In step (1), the final boiling point of the catalytic cracking diesel light fraction is 220-230 DEG C; the mass content of bicyclic aromatic hydrocarbons is 5-10 wt%.

6. The method of claim 1, wherein: The reaction conditions of the hydrofining reaction zone in step (2) are as follows: reaction pressure 3.0-15.0 MPa; liquid hourly space velocity 0.1-15.0 h -1 .

7. The method of claim 1, wherein: The reaction conditions of the hydrofining reaction zone in step (2) are as follows: reaction pressure 5.0-12.0 MPa; liquid hourly space velocity 0.2-3.0 h -1 .

8. The method of claim 1, wherein: The average reaction temperature of the low-temperature hydrofining reaction zone is 330-350 DEG C, and the average reaction temperature of the high-temperature hydrofining reaction zone is 380-400 DEG C; the average reaction temperature of the high-temperature hydrofining reaction zone is higher than that of the low-temperature hydrofining reaction zone by 30-50 DEG C.

9. The method of claim 1, wherein: In step (3), the reaction conditions of the hydrocracking reaction zone are as follows: reaction pressure 3.0-15.0 MPa, liquid hourly space velocity 0.1-15.0 h -1 The average reaction temperature of the hydrocracking reaction zone is 300℃-450℃.

10. The method of claim 1, wherein: In step (3), the reaction conditions of the hydrocracking reaction zone are as follows: the reaction pressure is 5.0-12.0 MPa, the liquid hourly space velocity is 0.2-3.0 h -1 -1, and the average reaction temperature of the hydrocracking reaction zone is 380℃-420℃.

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