A method and system for reconstitution and cracking of light gasoline fractions

Abstract

This invention provides a method and system for the reconstitution and cracking of light gasoline fractions. The reconstitution and cracking method includes first subjecting the light gasoline fraction to a homopolymerization reaction, then removing alkanes and / or aromatics from the homopolymerization stream, and finally subjecting the homopolymer stream (after impurity removal) to a cracking reaction to obtain C2-C4 olefins. This invention significantly increases the yield of C2-C4 olefins by performing homopolymerization and impurity removal operations before the cracking reaction.

Description

Technical Field

[0001] This invention relates to the field of light gasoline processing technology, specifically to a light gasoline fraction recombination and cracking method and system. Background Technology

[0002] Catalytic light gasoline has a high olefin content (generally 30%–50% by volume) and a low aromatic content (generally 10%–25% by volume). Light gasoline etherification technology involves reacting active tertiary olefins (2-methyl-1-butene, 2-methyl-2-butene, and some C6 tertiary olefins) in light gasoline with methanol to produce ethers such as methyl tert-amyl ether and methyl tert-hexyl ether, under the action of a macroporous, strongly acidic cationic resin catalyst. This etherification process reduces olefin content while increasing the octane number of automotive gasoline, reducing the volatilization of light hydrocarbons that contribute to smog and low-altitude ozone formation, and decreasing CO and CXHY emissions from vehicle exhaust, resulting in significant economic and social benefits. With the promotion of national ethanol gasoline policies, new ethanol standards require that no other oxygen-containing compounds be artificially added to ethanol gasoline. Therefore, etherified components such as MTBE and tAME (Temperature Ammonium Ester) cannot be used as gasoline blending components, and light gasoline C5 / C6 olefins face new application and utilization bottlenecks.

[0003] CN108283938A discloses a strong acid cationic resin catalyst and its application in the oligomerization of C5 / C6 olefins in light gasoline. The strong acid cationic resin catalyst is prepared by suspension copolymerization of styrene and divinylbenzene monomers under the action of a porogen and surfactants including triethanolamine soap, sulfated castor oil, sodium lauryl sulfate, and sodium glycocholate to obtain copolymer white spheres, which are then purified by pore treatment and sulfonated. This technical solution provides a safe and simple catalyst preparation method, exhibiting high activity and stability specifically for the catalytic reaction of C5 / C6 olefin oligomerization in light gasoline, achieving isopentenene conversion rates of over 75% and isohexene conversion rates of over 40%.

[0004] CN109336726A discloses a process for producing propylene and ethylene by coupled catalytic cracking of C4 hydrocarbons, light oils (including naphtha, stabilized light hydrocarbons, straight-run gasoline, raffinate, gasoline, etc.), and methanol. The process includes a feedstock pretreatment unit, a catalytic cracking reaction-regeneration unit, a separation unit, and a dry gas aromatization unit.

[0005] CN101691496A discloses a method for catalytic gasoline reforming and reducing olefins. The method involves first splitting catalytic gasoline into light gasoline and heavy gasoline. Then, using the light gasoline as feedstock, in a fixed-bed reactor equipped with cation exchange resin, the olefins in the light gasoline undergo an esterification reaction with acetic acid. After esterification, unreacted acetic acid is separated from the light gasoline, which is then mixed with unesterified heavy gasoline to obtain reformed gasoline. The reaction conditions include a temperature of 90–180°C, a pressure of 0.6–1.5 MPa, and a space velocity of 0.3–0.8 h⁻¹. -1 The olefin molar ratio is 1.5–10. This invention is simple to implement and increases the octane number of gasoline while reducing the olefin content of catalytic gasoline.

[0006] However, as exemplified above, existing technologies suffer from problems such as low yield of low-carbon olefins (C2-C4 olefins) and low propylene / ethylene ratio, resulting in poor economic benefits. Summary of the Invention

[0007] In view of the problems existing in the prior art, one of the objectives of the present invention is to provide a method for reconstituted cracking of light gasoline fractions, which can increase the production of C2-C4 olefins.

[0008] The second objective of this invention is to provide a light gasoline fraction recombination and cracking system.

[0009] The third objective of this invention is to provide an application of a light gasoline fraction recombination and cracking system corresponding to the second objective mentioned above.

[0010] To achieve one of the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for reorganizing and cracking light gasoline fractions, comprising:

[0012] S1. A feed stream comprising a light gasoline fraction is contacted with an oligomerization catalyst, thereby causing homopolymerization of the C5 and / or C6 olefins in the light gasoline fraction to obtain a reaction stream containing C... 10 ~C 20 At least one of the homopolymers;

[0013] S2. The reaction stream is subjected to a first separation process to obtain a first separated stream and a second separated stream, wherein the first separated stream contains alkanes and / or aromatics, and the second separated stream is rich in C. 10 ~C 20 At least one of the homopolymers;

[0014] S3. Contact the second separated stream with the cracking catalyst to obtain a cracked stream, wherein the cracked stream contains at least one of C2 to C4 olefins;

[0015] S4. The pyrolysis stream is subjected to a second separation process to obtain a third and a fourth separated stream, wherein the third separated stream is rich in at least one of C2-C4 olefins, and the fourth separated stream is rich in C... 10 ~C 20 At least one of the homopolymers; and

[0016] Optionally, S5. The fourth separated stream is recycled to step S3.

[0017] According to the present invention, in step S2, the term "rich" refers to the concentration of C in the second separated stream relative to the reaction stream. 10 ~C 20 The content of at least one homopolymer increases; in step S4, the term "rich" refers to an increase in the content of C2-C4 olefins in the third separation stream relative to the pyrolysis stream, and an increase in the content of C4 olefins in the fourth separation stream. 10 ~C 20 The content of at least one homopolymer increases.

[0018] According to the present invention, both C5 olefins and C6 olefins refer to monoolefins.

[0019] In some preferred embodiments of the present invention, in step S1, the type of homopolymerization reaction includes one or more of dimerization, trimerization, and tetramerization, preferably including dimerization, trimerization, and tetramerization.

[0020] According to the present invention, the type and content of homopolymers in the reaction stream are determined by the raw materials and the type of homopolymerization reaction. For example, if the raw materials contain C5 and C6 olefins, and the homopolymerization reaction occurs uniformly in the form of dimerization, trimerization, and tetramerization, then the reaction stream contains C5 olefins and C6 olefins. 10 Homopolymer, C 12 Homopolymer, C 15 Homopolymer, C 18 Homopolymer and C 20 Homopolymer. It should be noted that as the chain length increases, the polymerizability of monoolefins decreases, so the probability of tetramerization of C6 olefins is very small, and the product essentially contains no C6 atoms. 24 Homopolymer.

[0021] In some preferred embodiments of the present invention, in step S1, the light gasoline fraction comprises, by mass percentage:

[0022]

[0023] According to the present invention, the light gasoline fractions obtained from crude oil from different origins and from different refining methods will vary slightly. Those skilled in the art will understand that the light gasoline fractions with the specific compositions described above are only one type of existing light gasoline fractions, and the present invention is not intended to protect only the cracking methods when using the light gasoline fractions with the specific compositions described above as feedstock.

[0024] According to the present invention, light gasoline fraction is a conventional fraction in the art, and those skilled in the art know what kind of logistics light gasoline fraction refers to.

[0025] In some preferred embodiments of the present invention, in step S1, the raw material stream is a light gasoline fraction, preferably a light gasoline fraction with a distillation range of 70°C to 80°C, and more preferably, the light gasoline fraction is a mixture of one or more of catalytic cracking light gasoline, catalytic pyrolysis light gasoline, coking light gasoline, thermal pyrolysis gasoline, thermal cracking gasoline and coal liquefaction light gasoline.

[0026] In some preferred embodiments of the present invention, in step S1, the oligomer catalyst is a resin catalyst or a molecular sieve catalyst; preferably, the resin catalyst is selected from macroporous strong acid cation exchange resins, more preferably from one or more of styrene-based macroporous sulfonic acid resins, acrylic-based macroporous sulfonic acid resins, epoxy-based macroporous sulfonic acid resins and phenolic-based macroporous sulfonic acid resins.

[0027] In some preferred embodiments of the present invention, when the resin catalyst is used, the contact conditions include: a temperature of 15°C to 100°C, preferably 25°C to 90°C; a pressure of 0.4 MPa to 1.5 MPa, preferably 0.5 MPa to 0.8 MPa; and a feed mass hourly space velocity of 0.5 h⁻¹. -1 ~5.0h -1 1.5h is preferred -1 ~4.0h -1 When using the molecular sieve catalyst, the contact conditions include: a temperature of 70℃~200℃, preferably 90℃~160℃; a pressure of 0.4MPa~1.5MPa, preferably 0.5MPa~0.8MPa; and a feed space velocity of 0.5h⁻¹. -1 ~5.0h -1 1.5h is preferred -1 ~4.0h -1 .

[0028] In some preferred embodiments of the present invention, in step S3, the pyrolysis catalyst includes a support and an active component. The support is selected from molecular sieves, preferably Y, ZSM-5, ZSM-35, MCM-22, mordenite, MCM-41, SAPO-11, and SAPO-41. The active component is selected from transition metals, preferably at least one of Ni, Cu, Pb, and Pt, more preferably Pb. Preferably, the loading of the active component is 10 ppm to 200 ppm, more preferably 20 ppm to 150 ppm.

[0029] According to the present invention, the molecular sieve is preferably a hydrogen-type molecular sieve.

[0030] In some preferred embodiments of the present invention, in step S3, the contact conditions include: a temperature of 300°C to 650°C, preferably 350°C to 500°C; a pressure of 0.02 MPa to 0.15 MPa, preferably 0.05 MPa to 0.1 MPa; and a feed mass hourly space velocity of 0.5 h⁻¹. -1 ~5.0h -1 1.5h is preferred -1 ~3.0h -1 .

[0031] According to the present invention, both the first separation process and the second separation process are conventional techniques in the art, and will not be described in detail here. Exemplarily, both the first separation process and the second separation process are carried out in a separation tower, and the specific separation conditions are based on obtaining two streams that meet the component requirements.

[0032] To achieve the second objective mentioned above, the technical solution adopted by the present invention is as follows:

[0033] A light gasoline fraction recombining and cracking system includes a first reactor, a first separation tower, a second reactor, and a second separation tower connected in sequence. Preferably, the first reactor is an oligomer reactor, and the second reactor is a cracking reactor. More preferably, the bottom outlet of the second separation tower is connected to the inlet of the second reactor.

[0034] To achieve the third objective mentioned above, the technical solution adopted by the present invention is as follows:

[0035] Application of a light gasoline fraction reconstitution cracking system according to any one of the above embodiments in the processing of light gasoline.

[0036] In some preferred embodiments of the present invention, light gasoline is processed in the light gasoline fraction reconstitution cracking system described in any one of the above embodiments using the method described in any one of the above embodiments.

[0037] The beneficial effects of this invention are at least in the following aspects:

[0038] Firstly, the light gasoline fraction recombination and cracking process of the present invention is easy to operate and suitable for industrial promotion.

[0039] Secondly, the yield of C2-C4 olefins in the light gasoline fraction recombination cracking process of the present invention is greater than 80%, which has high economic benefits. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the process flow of Embodiment 1 of the present invention.

[0041] Explanation of reference numerals in the attached diagram: 1-Light gasoline feedstock, 2-Oligomerization reactor, 3-First separation tower, 4-Crack reactor, 5-Second separation tower, 6-Light hydrocarbon product, 7-Unreacted inert component. Detailed Implementation

[0042] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0043] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0044] In the following embodiments, the feedstock used is catalytic cracking light gasoline, which has the following composition: 10 wt% C5-C6 straight-chain alkanes; 45 wt% C5-C6 branched alkanes; 4 wt% C5-C6 cycloalkanes; 15 wt% aromatics; 18 wt% C5 olefins; and 8 wt% C6 olefins.

[0045] The oligomerization catalyst was Amberlyst-35 resin catalyst, purchased from Dandong Mingzhu Resin Factory.

[0046] The cracking catalysts include MCM-22 molecular sieve and ZSM-35, which are produced by Nankai University Catalyst Factory.

[0047] Example 1

[0048] The feedstock used was catalytic cracking light gasoline, which was pumped into the oligomer reactor via a metering pump. The reactor contained 50 ml of Amberlyst-35 resin catalyst, and the temperature was 40°C, the pressure was 0.5 MPa, and the feed space velocity was 1.0 h⁻¹. -1 Under these conditions, an oligomerization reaction occurs, and C5 and C6 olefins oligomerize into C6 olefins. 10 ~C 20Oligomers. The product enters the first separation column, where unreacted alkanes, cycloalkanes, aromatics, and other inert components are separated at the top, and the oligomer product is obtained at the bottom. The oligomer product obtained at the bottom is metered into the cracking reactor, which is loaded with 25 ml of cracking catalyst. The reaction temperature is 350℃, the pressure is 0.05 MPa, and the feed space velocity is 0.5 h⁻¹. -1 Under the action of a cracking catalyst, C 10 ~C 20 The oligomers undergo pyrolysis to produce low-carbon olefins. The products from the pyrolysis reactor are separated by a second separation column. The low-carbon olefin product is obtained at the top of the column, while the unreacted oligomers at the bottom are returned to the pyrolysis inlet to continue pyrolysis. The composition of the low-carbon olefins is shown in Table 1.

[0049] As shown in Table 1, the cracking temperature is 350℃, the propylene / ethylene ratio is 8.08, and the yield of low-carbon olefins reaches 87.92%.

[0050] Example 2

[0051] The same reaction apparatus, raw materials, and procedures as in Example 1 were used. The difference lies in the oligomerization reaction temperature (70°C) and pressure (0.7 MPa), and the pyrolysis reaction temperature (450°C). The composition of the low-carbon olefins is shown in Table 1. Table 1 shows that at a pyrolysis temperature of 450°C, with a propylene / ethylene ratio of 7.48, the yield of low-carbon olefins reached 85.11%.

[0052] Example 3

[0053] The same reaction apparatus, raw materials, and procedures as in Example 1 were used. The differences were that the oligomerization catalyst was ZSM-35, the reaction temperature was 100°C, and the pressure was 0.7 MPa. The pyrolysis catalyst was mordenite, and the pyrolysis reaction temperature was 400°C. The composition of the low-carbon olefins is shown in Table 1. From Table 1, it can be seen that at a pyrolysis temperature of 400°C, the propylene / ethylene ratio was 8.59, and the yield of low-carbon olefins reached 88.14%.

[0054] Example 4

[0055] The same reaction apparatus, raw materials, and procedures as in Example 1 were used. The differences were that the oligomerization reaction temperature was 140°C and the pressure was 0.7 MPa. The pyrolysis reaction temperature was 450°C. The composition of the low-carbon olefins is shown in Table 1. From Table 1, it can be seen that at a pyrolysis temperature of 450°C, the propylene / ethylene ratio was 8.10, and the yield of low-carbon olefins reached 85.3%.

[0056] Comparative Example 1

[0057] The raw materials used were the same as in Example 1. In this comparative example, the light gasoline feedstock was directly fed into the cracking reactor without passing through the oligomerization reactor to undergo the cracking reaction. The reactor was loaded with 25 ml of MCM-22 molecular sieve cracking catalyst, and the reaction temperature was 450°C, the pressure was 0.05 MPa, and the space velocity was 0.5 h⁻¹. -1 Under the action of a cracking catalyst, olefin oligomers undergo cracking to generate low-carbon olefins. The product from the cracking reactor is separated by a separation column; the low-carbon olefin product is obtained at the top of the column, while the unreacted oligomers at the bottom are returned to the cracking reaction inlet to continue cracking. The composition of the low-carbon olefins is shown in Table 1. From Table 1, it can be seen that at a cracking temperature of 450℃, a propylene / ethylene ratio of 3.27, and a low-carbon olefin yield of 76.03%, the yield is achieved.

[0058] Comparative Example 2

[0059] The raw materials used were the same as in Example 1. In this comparative example, the light gasoline feedstock was directly fed into the cracking reactor without passing through the oligomerization reactor to undergo the cracking reaction. The reactor was loaded with 25 ml of ZSM-35 molecular sieve cracking catalyst, and the reaction temperature was 480°C, the pressure was 0.05 MPa, and the space velocity was 0.5 h⁻¹. -1 Under the action of a cracking catalyst, olefin oligomers undergo cracking to generate low-carbon olefins. The product from the cracking reactor is separated by a separation column; the low-carbon olefin product is obtained at the top of the column, while the unreacted oligomers at the bottom are returned to the cracking reaction inlet to continue cracking. The composition of the low-carbon olefins is shown in Table 1. From Table 1, it can be seen that at a cracking temperature of 480℃, a propylene / ethylene ratio of 2.90, and a low-carbon olefin yield of 74.27%, the yield is achieved.

[0060] Table 1

[0061]

[0062] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for reorganizing and cracking light gasoline fractions, comprising: S1. A feed stream comprising a light gasoline fraction is contacted with an oligomerization catalyst, thereby causing homopolymerization of the C5 and / or C6 olefins in the light gasoline fraction to obtain a reaction stream containing C... 10 ~C 20 At least one of the homopolymers; S2. The reaction stream is subjected to a first separation process to obtain a first separated stream and a second separated stream, wherein the first separated stream contains alkanes and / or aromatics, and the second separated stream is rich in C. 10 ~C 20 At least one of the homopolymers; S3. Contact the second separated stream with the cracking catalyst to obtain a cracked stream, wherein the cracked stream contains at least one of C2-C4 olefins; S4. The pyrolysis stream is subjected to a second separation process to obtain a third and a fourth separated stream, wherein the third separated stream is rich in at least one of C2-C4 olefins, and the fourth separated stream is rich in C... 10 ~C 20 At least one of the homopolymers; and Optionally, S5. The fourth separated stream is recycled to step S3; In step S1, the type of homopolymerization reaction includes one or more of dimerization, trimerization, and tetramerization; Both C5 and C6 alkenes refer to monoolefins.

2. The recombination and pyrolysis method according to claim 1, characterized in that, In step S1, the homopolymerization reaction includes dimerization, trimerization, and tetramerization.

3. The recombination and pyrolysis method according to claim 1 or 2, characterized in that, In step S1, the light gasoline fraction comprises, by mass percentage: C5-C6 straight-chain alkanes 5wt%~15wt%; C5-C6 branched alkanes 40wt%~55wt%; C5-C6 cycloalkanes 1wt%~10wt%; Aromatic hydrocarbons 10wt%~25wt%; C5 olefins 8wt%~20wt%; C6 olefins 1 wt%~10 wt%.

4. The recombination and pyrolysis method according to claim 3, characterized in that, In step S1, the light gasoline fraction comprises, by mass percentage: C5-C6 straight-chain alkanes: 6wt%~12wt%; C5-C6 branched alkanes 45wt%~55wt%; C5-C6 cycloalkanes 2wt%~8wt%; Aromatic hydrocarbons 15wt%~20wt%; C5 olefins 10wt%~18wt%; C6 olefins 2wt%~8wt%.

5. The recombination and pyrolysis method according to claim 1 or 2, characterized in that, In step S1, the raw material stream is a light gasoline fraction.

6. The recombination and pyrolysis method according to claim 5, characterized in that, In step S1, the light gasoline fraction is a light gasoline fraction with a distillation range of 70℃~80℃.

7. The recombination and pyrolysis method according to claim 6, characterized in that, In step S1, the light gasoline fraction is a mixture of one or more of the following: catalytic cracking light gasoline, catalytic pyrolysis light gasoline, coking light gasoline, and coal liquefaction light gasoline.

8. The recombination and pyrolysis method according to claim 6, characterized in that, In step S1, the light gasoline is distilled into thermally cracked gasoline.

9. The recombination and pyrolysis method according to claim 6, characterized in that, In step S1, the light gasoline is distilled into thermally cracked gasoline.

10. The recombination and pyrolysis method according to claim 1 or 2, characterized in that, In step S1, the oligomerization catalyst is a resin catalyst or a molecular sieve catalyst.

11. The recombination and pyrolysis method according to claim 10, characterized in that, The resin catalyst is selected from macroporous strong acid cation exchange resins.

12. The recombination and pyrolysis method according to claim 11, characterized in that, The resin catalyst is selected from one or more of styrene-based macroporous sulfonic acid resins, acrylic-based macroporous sulfonic acid resins, epoxy-based macroporous sulfonic acid resins, and phenolic-based macroporous sulfonic acid resins.

13. The recombination and pyrolysis method according to claim 10, characterized in that, When using the resin catalyst, the contact conditions include: temperature 15℃~100℃, pressure 0.4MPa~1.5MPa, and feed mass hourly space velocity 0.5h. -1 ~5.0h -1 When using the molecular sieve catalyst, the contact conditions include: temperature 70℃~200℃, pressure 0.4MPa~1.5MPa, and feed space velocity 0.5h. -1 ~5.0h -1 .

14. The recombination and pyrolysis method according to claim 13, characterized in that, When using the resin catalyst, the contact conditions include: temperature 25℃~90℃, pressure 0.5MPa~0.8MPa, and feed mass hourly space velocity 1.5h. -1 ~4.0h -1 When using the molecular sieve catalyst, the contact conditions include: temperature 90℃~160℃, pressure 0.5MPa~0.8MPa, and feed space velocity 1.5h. -1 ~4.0h -1 .

15. The recombination and pyrolysis method according to claim 1 or 2, characterized in that, In step S3, the cracking catalyst includes a support and an active component, wherein the support is selected from molecular sieves and the active component is selected from transition metals.

16. The recombination and pyrolysis method according to claim 15, characterized in that, The carrier is Y, ZSM-5, ZSM-35, MCM-22, mordenite, MCM-41, SAPO-11, or SAPO-41, and the active component is at least one of Ni, Cu, Pb, and Pt.

17. The recombination and pyrolysis method according to claim 16, characterized in that, The active component is Pb.

18. The recombination and pyrolysis method according to claim 17, characterized in that, The loading of the active component is 10ppm to 200ppm.

19. The recombination and pyrolysis method according to claim 18, characterized in that, The loading of the active component is 20ppm to 150ppm.

20. The recombination and pyrolysis method according to claim 1 or 2, characterized in that, In step S3, the contact conditions include: temperature 300℃~650℃, pressure 0.02MPa~0.15MPa, and feed mass hourly space velocity 0.5h. -1 ~5.0h -1 .

21. The recombination and pyrolysis method according to claim 20, characterized in that, In step S3, the contact conditions include: temperature 350℃~500℃, pressure 0.05MPa~0.1MPa, and feed mass hourly space velocity 1.5 h⁻¹. -1 ~3.0 h -1 .

22. The recombination and pyrolysis method according to claim 1 or 2, characterized in that, The recombination pyrolysis method is carried out in a light gasoline fraction recombination pyrolysis system, which includes a first reactor, a first separation tower, a second reactor, and a second separation tower connected in sequence. The first reactor is an oligomerization reactor, and the second reactor is a pyrolysis reactor.

23. The recombination and pyrolysis method according to claim 22, characterized in that, The bottom outlet of the second separation tower is connected to the inlet of the second reactor.

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