Process for the conversion of aromatics and olefins containing gasoline

Abstract

The present application belongs to the technical field of olefin preparation, and relates to a method for converting an aromatic hydrocarbon and olefin-containing gasoline, which comprises the following steps: firstly, extracting aromatic hydrocarbons from the aromatic hydrocarbon and olefin-containing gasoline to obtain raffinate oil; secondly, separating the raffinate oil into an alkane-rich fraction and an olefin-rich fraction through alkane-olefin separation; and thirdly, converting the alkane-rich fraction and the olefin-rich fraction under different conditions respectively. The method can produce low-carbon olefins from the aromatic hydrocarbon and olefin-containing gasoline, and the proportion of ethylene and propylene can be adjusted.

Description

Technical Field

[0001] This invention belongs to the field of low-carbon olefin preparation technology, and relates to a method for obtaining olefins by converting gasoline containing aromatics and olefins. Background Technology

[0002] In recent years, the rapid development of the polyester industry in China and the world has driven demand for terephthalic acid (PTA), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT), leading to increased market demand for paraxylene (PX). This has not only promoted the development of aromatics process technology but also accelerated the improvement of production and operation levels and the construction speed of aromatics plants. In the coming years, in addition to tapping the potential and expanding the capacity of existing PX plants, it is crucial to rationally develop and select complete aromatics process technologies to broaden raw material sources.

[0003] One of the feedstocks for aromatics is petroleum, and there are two process routes: one is to obtain aromatics from naphtha through catalytic reforming and aromatic extraction; the other is to obtain low-value-added aromatic feedstock from ethylene cracked gasoline, a byproduct of ethylene plants, through hydrogenation and aromatic extraction, and then convert it into high-value-added aromatic products. Catalytic cracked gasoline is rich in aromatics, mainly light aromatics such as benzene, toluene, and xylene, making it a valuable and usable aromatic resource. Further catalytic cracking of catalytic cracked gasoline to produce more aromatics can broaden the feedstock sources for aromatics.

[0004] Ethylene and propylene are important basic chemical raw materials with a rich downstream industrial chain and a large market size. In recent years, in particular, driven by demand from downstream industries, the demand for ethylene and propylene has grown rapidly both domestically and internationally.

[0005] With the development of new energy vehicles, transportation fuels produced by the oil refining industry, especially catalytic cracking gasoline, are gradually being replaced by new energy sources, and their market share is gradually shrinking. It is projected that gasoline consumption will decrease year by year from 2030 to 2060, eventually being almost completely replaced by new energy sources, while the demand for ethylene and propylene is rising rapidly, and the demand for PX is still increasing. Therefore, the transformation of oil refining towards chemical production has become the mainstream trend in the industry. FCCs, as gasoline production units, must gradually transform into units producing other high-value-added products. my country currently has approximately 180 catalytic cracking units, with a total processing capacity of about 200 million tons. Based on a gasoline yield of 42-45%, this can produce approximately 90 million tons of catalytic gasoline. However, due to the large-scale development of catalytic cracking units, the positioning of small and medium-sized catalytic crackers has become blurred, and their functions are weaker. Utilizing small catalytic crackers to process excess gasoline and produce chemical products has significant practical implications. FCCs will remain the main unit for gasoline production for some time, while also producing basic chemical raw materials such as ethylene and propylene.

[0006] Existing technologies for producing new low-carbon olefins, primarily using light feedstock oils, mainly employ straight-run naphtha, whose composition is predominantly alkanes and cycloalkanes. In contrast, catalytic cracking gasoline contains alkanes, olefins, and aromatics, resulting in a significant compositional difference between the two. In recent years, to meet the development needs of the low-carbon olefins industry, numerous scientists have dedicated themselves to developing novel catalytic cracking processes, hoping to improve the yield of low-carbon olefins and enhance the adjustability of propylene / ethylene ratios.

[0007] Catalytic cracked gasoline contains aromatics. If directly converted, these aromatics are prone to condensation or hydrogen transfer reactions, leading to the loss of light aromatics. Therefore, removing or partially removing aromatics from the gasoline before conversion can be considered. However, converting gasoline fractions after aromatic removal suffers from low yields of ethylene and propylene. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for producing low-carbon olefins (ethylene, propylene) from gasoline containing olefins and aromatics, wherein the propylene / ethylene ratio of the method is adjustable.

[0009] Therefore, the present invention provides the following technical solution.

[0010] Technical Solution 1: A method for converting gasoline containing olefins and aromatics, comprising:

[0011] (1) Aromatic extraction and separation of olefin and aromatic gasoline is carried out to obtain extracted oil and raffinate oil, wherein the aromatic concentration in the extracted oil is higher than that in the raffinate oil.

[0012] (2) The raffinate is subjected to alkane-olefin separation to obtain alkane-rich gasoline fraction and olefin-rich gasoline fraction;

[0013] (3) The alkane-rich gasoline fraction is contacted with the first catalytic cracking catalyst to carry out the first catalytic cracking reaction;

[0014] (4) The olefin-rich gasoline fraction is contacted with the second catalytic cracking catalyst to carry out the second catalytic cracking reaction.

[0015] In this invention, the terms "first," "second," and "third" are used to distinguish the names of terms in different schemes or steps.

[0016] The present invention provides a gasoline containing olefins and aromatics that comprises olefins, aromatics, and alkanes (including alkanes and cycloalkanes). Optionally, the gasoline containing olefins and aromatics contains 12-52% by mass of olefins, 8-40% by mass of aromatics, and 8-80% by mass of alkanes.

[0017] The raffinate is the gasoline fraction remaining after most of the aromatic components have been extracted from the gasoline fraction via aromatics extraction. The extracted oil is the gasoline fraction containing the main aromatics extracted from the aromatics.

[0018] Technical Solution 2: According to the method of Technical Solution 1, wherein in step (1), the aromatic content of the raffinate is preferably less than 5% by mass.

[0019] The aromatic hydrocarbon extraction and separation can be performed using existing aromatic hydrocarbon extraction and separation methods. One embodiment includes the step of contacting the aromatic hydrocarbon and olefin-containing gasoline with an extraction solvent in an extraction column; optionally, the solvent used for aromatic hydrocarbon extraction (extraction solvent) is, for example, one or a mixture of several of sulfolane, tetraethylene glycol, or n-formylmorpholine. Optionally, one embodiment employs an extraction-solvent recovery process, wherein the solvent ratio in the extraction column is 3–6, the number of theoretical plates in the extraction column is 3–10, and the operating temperature is 60–140°C; the number of theoretical plates in the recovery column is 10–30, the bottom temperature is 170–190°C, and the reflux ratio is 0.5–2.

[0020] Technical Solution 3: The method for converting olefin- and aromatic gasoline according to Technical Solution 1 or 2, wherein, optionally, in step (2), the olefin mass fraction in the alkane-rich gasoline fraction (or the first gasoline alkane) is less than 10% by mass, for example, 2-10% by mass, and the alkane mass fraction is not less than 80% by mass, for example, 80-95% by mass. Optionally, the total aromatic content in the alkane-rich gasoline fraction does not exceed 10% by mass, for example, 0-9% by mass, 2-5% by mass, or less than 2% by mass.

[0021] Technical Solution 4: According to any of the above technical solutions, in the method for converting olefin- and aromatic gasoline, in step (2), the olefin-rich gasoline fraction (referred to as the first gasoline olefin) has an alkane mass fraction of less than 10% by mass, for example, 2-5% by mass, a total aromatic content of no more than 10% by mass, and an olefin content of not less than 85% by mass, for example, 85-95% by mass. Optionally, the total aromatic content in the olefin-rich gasoline fraction does not exceed 10% by mass, for example, 2-9% by mass or 3-6% by mass.

[0022] Technical Solution 5: According to any of the above technical solutions, the method for converting gasoline containing olefins and aromatics, in one embodiment, the alkane-olefin separation method includes contacting the raffinate with a solvent for alkane-olefin separation (referred to as alkane-olefin separation solvent) in a liquid-liquid extraction tower to obtain a component rich in olefins and solvent and a component rich in alkanes; the component rich in olefins and solvent is separated, for example, in an extraction distillation tower, to obtain an alkane-olefin separation solvent and an olefin-rich gasoline fraction; the component rich in alkanes is further separated by removing a small amount of the alkane-olefin separation solvent, for example, by fractional distillation, to obtain an alkane-rich gasoline fraction and solvent.

[0023] The solvent used for alkane-olefin separation is, for example, one or a mixture of amide compounds, glycol compounds, glycol ether compounds, lactone compounds, and sulfone compounds; the amide compounds include, for example, one or more of N,N-dimethylformamide, N-formylmorpholine, 1,3-dimethyl-2-imidazolinone, and N-methylpyrrolidone; the glycol compounds include, for example, one or more of diethylene glycol, triethylene glycol, and tetraethylene glycol; the glycol ether compounds include, for example, one or more of diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, and tetraethylene glycol monomethyl ether; the lactone compounds include, for example, one or more of γ-butyrolactone, γ-valerolactone, and δ-valerolactone; and the sulfone compounds include, for example, one or more of sulfolane, 3-methylsulfolane, dimethyl sulfone, and dimethyl sulfoxide.

[0024] In one embodiment, the alkane-alkene separation employs a liquid-liquid extraction-extractive distillation-solvent recovery process. The liquid-liquid extraction column has a top temperature of 50-90°C, a solvent ratio of 4-12 (mass ratio), and 8-30 theoretical plates. The extractive distillation column has a top temperature of 70-90°C, a bottom temperature of 120-160°C, a solvent ratio of 2-4, and 20-50 theoretical plates. The solvent recovery column has a top temperature of 55-80°C, a bottom temperature of 160-180°C, a reflux ratio of 0.3-0.6, and 8-40 theoretical plates.

[0025] Optionally, methods and apparatus for separating alkane and olefin are described in Chinese patent applications CN202311432968.7 (Method and Apparatus for Separating and Purifying Alkanes and Olefins from a Mixture of Hydrocarbons) and CN202311436058.6 (Method and Apparatus for Separating and Purifying Aromatic Hydrocarbons, Alkanes and Olefins). These are incorporated herein by reference.

[0026] Technical Solution 6: In the conversion method of olefin- and aromatic gasoline according to any of the above technical solutions, the first catalytic cracking catalyst and the second catalytic cracking catalyst can be the same catalytic cracking catalyst or different catalytic cracking catalysts.

[0027] Technical Solution 7: According to any of the above technical solutions, the conversion method for olefin- and aromatic gasoline, based on dry weight, the first catalytic cracking catalyst or the second catalytic cracking catalyst each contains: 0.01 to 40% by mass, for example 10 to 40% by mass, of mesoporous zeolite, and 0.01 to 80% by mass, for example 40 to 75% by mass or 50 to 70% by mass, preferably 60 to 80% by mass, of a support.

[0028] Technical Solution 8: According to any of the above technical solutions, the method for converting olefin- and aromatic gasoline comprises, respectively, 0.01–10% by mass (preferably 5–10% by mass) of macroporous zeolite and 0.01–40% by mass (preferably 20–30% by mass) of mesoporous zeolite, and 0.01–80% by mass (preferably 50–70% by mass) of support. This can result in higher yields of low-carbon olefins (ethylene, propylene) and / or higher yields of aromatics.

[0029] In one embodiment, the content of mesoporous zeolite in the first catalytic cracking catalyst and / or the second catalytic cracking catalyst is greater than the content of macroporous zeolite, for example, the mass ratio of mesoporous zeolite to macroporous zeolite is 1 to 25:1, for example, 10 to 20:1 or 2:1 to 3:1.

[0030] Technical Solution 9: According to any of the above technical solutions, the method for converting olefin- and aromatic gasoline, optionally, the first catalytic cracking catalyst contains: 0.01-10% by mass, preferably 5-10% by mass, macroporous zeolite and / or 0.01-40% by mass, preferably 20-30% by mass, mesoporous zeolite, and 0.01-80% by mass, preferably 50-70% by mass, support; preferably, the mass ratio of mesoporous zeolite to macroporous zeolite is 10-20:1.

[0031] Technical Solution 10: A method for converting olefin- and aromatic gasoline according to any of the above technical solutions, wherein the first or second catalytic cracking catalyst contains: 0.01–40% by mass, for example, 10–40% by mass, of mesoporous zeolite; 0.01–80% by mass, preferably 50–80% by mass or 60–90% by mass, of support; and does not contain macroporous zeolite. In this case, a lower coke yield may be achieved.

[0032] Technical Solution 11: The conversion method for olefin- and aromatic gasoline according to any of the above technical solutions, wherein the olefin- and aromatic gasoline is catalytic cracking gasoline and / or catalytic cracking gasoline after desulfurization. The sulfur content in the olefin- and aromatic gasoline fraction preferably does not exceed 10 ppm by mass. In one embodiment, the olefin- and aromatic gasoline is a heavy gasoline fraction with an initial boiling point greater than 50°C (e.g., an initial boiling point of 50–70°C), for example, the olefin- and aromatic gasoline has a boiling range between 50 and 220°C.

[0033] Technical Solution 12: The method for converting olefin- and aromatic gasoline according to any of the above technical solutions, wherein the olefin- and aromatic gasoline is obtained by subjecting heavy oil feedstock to catalytic cracking reaction (referred to as heavy oil catalytic cracking reaction), and separating the products of the heavy oil catalytic cracking reaction in a fractionation unit (referred to as the third fractionation unit) and optionally performing desulfurization treatment; the catalytic cracked gasoline obtained in the third fractionation unit contains olefins and aromatics, and the catalytic cracked gasoline can be directly subjected to aromatic extraction, or the catalytic cracked gasoline can be desulfurized and then subjected to aromatic extraction to obtain the olefin- and aromatic gasoline; the desulfurization treatment is, for example, hydrodesulfurization or adsorption desulfurization, and the desulfurized catalytic cracked gasoline is obtained after the desulfurization treatment.

[0034] In one embodiment, the reaction conditions for the catalytic cracking reaction of the heavy oil feedstock include: a reaction temperature of 450–650°C, for example, 480–530°C; a catalyst-to-oil ratio (mass ratio) of 3–20:1, for example, 4–10; and a reaction time of 1–15 seconds, for example, 1.5–5 seconds. The heavy oil feedstock may be one or more of atmospheric wax oil, atmospheric residue oil, vacuum wax oil, and vacuum residue oil.

[0035] The separation of the catalytic cracking reaction products can be carried out by fractionation. Fractionation is usually carried out in a fractionation unit and can be carried out by fractionation methods well known to those skilled in the art. The fractions obtained by fractionation may include gasoline (referred to as third catalytic gasoline in this invention), diesel (referred to as third catalytic diesel in this invention), liquefied petroleum gas (referred to as third liquefied petroleum gas in this invention), dry gas (referred to as third dry gas in this invention) and oil slurry (referred to as third oil slurry in this invention).

[0036] Technical Solution 13. According to any of the above technical solutions, in one embodiment of the method for converting olefin- and aromatic gasoline, the heavy oil feedstock undergoes catalytic cracking reaction. Based on a dry basis, the heavy oil catalytic cracking catalyst contains 0.01–40% by mass, preferably 20–35% by mass, of macroporous zeolite and / or 0.01–30% by mass, for example, 1–15% by mass, of mesoporous zeolite, and 0.01–80% by mass, for example, 60–80% by mass, of a support. In another embodiment, the content of mesoporous zeolite in the heavy oil catalytic cracking catalyst is less than the content of macroporous zeolite, for example, the mass ratio of mesoporous zeolite to macroporous zeolite is 1:3 to 1:5.

[0037] Technical Solution 14: In the conversion method for olefin- and aromatic gasoline according to any of the above technical solutions, the carrier in each of the first catalytic cracking catalyst, the second catalytic cracking catalyst, and the heavy oil catalytic cracking catalyst comprises clay and a binder. The clay is, for example, one or more of kaolin, hydrous kaolin, montmorillonite, diatomaceous earth, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite, and rettoiter. The binder is, for example, one or more of alumina sol, silica sol, phosphoalumina sol, and colloidal boehmite.

[0038] Technical Solution 15: According to any of the above technical solutions, the conversion method of olefin- and aromatic gasoline, wherein the macroporous zeolite (or macroporous molecular sieve) is one or more of Y-type molecular sieve and MCM molecular sieve, preferably Y-type molecular sieve; the mesoporous zeolite (or mesoporous molecular sieve) is one or more of ZSM-5 molecular sieve, IM-5 molecular sieve and β molecular sieve, preferably ZSM-5 molecular sieve.

[0039] The Y-type molecular sieve is one or more of REY molecular sieve, HY molecular sieve, REHY molecular sieve, USY molecular sieve, and REUSY molecular sieve; the ZSM-5 molecular sieve is one or more of HZSM-5 molecular sieve, rare earth-containing ZSM-5 molecular sieve such as ZRP molecular sieve, phosphorus and Fe-containing ZSM-5 molecular sieve such as ZSP molecular sieve, and phosphorus-modified ZSM-5 molecular sieve.

[0040] Technical Solution 16. In one embodiment of the conversion method for olefin- and aromatic gasoline according to any of the above technical solutions, a gasoline fraction is separated from the reaction product of the first catalytic cracking, referred to as the first gasoline fraction; a gasoline fraction is separated from the reaction product of the second catalytic cracking, referred to as the second gasoline fraction; the first gasoline fraction and the second gasoline fraction are used as part of the olefin- and aromatic gasoline fraction for aromatic extraction.

[0041] Technical Solution 17. In one embodiment of the conversion method for olefin- and aromatic gasoline according to any of the above technical solutions, the reaction products of the first catalytic cracking and the reaction products of the second catalytic cracking are mixed and then a gasoline fraction is separated. The separated gasoline fraction is used as part of the olefin- and aromatic gasoline fraction for aromatic extraction.

[0042] According to any of the above technical solutions, in one embodiment of the conversion method for olefin- and aromatic gasoline, the reaction products of the first catalytic cracking and the reaction products of the second catalytic cracking are mixed with the reaction products of the heavy oil catalytic cracking and then separated in the fractionation unit (third fractionation unit) of the heavy oil catalytic cracking to obtain olefin- and aromatic gasoline fractions.

[0043] Technical Solution 18: According to any of the above technical solutions, the preferred method for converting olefin- and aromatic gasoline includes the following conditions for the first catalytic cracking reaction: a reaction temperature of 550–750°C, preferably 580–680°C, for example 580–620°C; an agent-to-oil ratio (mass ratio) of 5–30:1, preferably 15–25; and a reaction time of 1–15 seconds, preferably 3–10 seconds.

[0044] Technical Solution 19: According to any of the above technical solutions, the preferred method for converting olefin- and aromatic gasoline includes the following conditions for the second catalytic cracking: a reaction temperature of 350–650°C, for example, 400–450°C, 450–620°C, 520–610°C, 550–610°C, or 580–610°C; an agent-to-oil ratio (mass ratio) of 5–20:1, preferably 5–10; and a reaction time of 1–15 seconds, preferably 2–8 seconds.

[0045] Technical Solution 20: A method for converting olefin- and alkane-containing hydrocarbon oil, comprising separating the olefin- and alkane-containing hydrocarbon oil into alkane-rich fractions and olefin-rich fractions, and then converting the alkane-rich fractions and olefin-rich fractions separately in different reactors. This method can achieve better ethylene and propylene yields than non-separation conversion. Optionally, the boiling range of the olefin- and alkane-containing hydrocarbon oil is 50-220°C; in one embodiment, the boiling range of the olefin- and alkane-containing hydrocarbon oil is 50-80°C.

[0046] Technical solution 21: The present invention also provides a heavy oil catalytic conversion device, comprising:

[0047] (1) A heavy oil catalytic cracking unit may include: a reactor for carrying out heavy oil catalytic cracking, such as a heavy oil riser reactor (third riser reactor); a settling device for separating the oil (oil gas and catalyst mixture) leaving the heavy oil riser reactor, referred to as the third settling device; and a third fractionating tower for separating the oil gas obtained from the oil separation in the third settling device, wherein the third fractionating tower can fractionate to obtain catalytic cracked gasoline.

[0048] (2) An optional catalytic cracking gasoline desulfurization unit, such as a hydrodesulfurization unit or an adsorption desulfurization unit, preferably a hydrodesulfurization unit;

[0049] (3) An aromatic extraction unit for extracting aromatics from the catalytic cracking gasoline and / or the desulfurized catalytic cracking gasoline from a desulfurization unit such as a hydrodesulfurization unit, to obtain raffinate and extracted oil.

[0050] (4) Alkylene separation unit, used to separate alkane and alkene from raffinate oil to obtain olefin-rich gasoline fraction and alkane-rich gasoline fraction;

[0051] (5) An apparatus for catalytic cracking of alkane-rich gasoline fractions, comprising: a reactor, such as a riser reactor referred to as a first riser reactor; a settling device for separating oil from the first riser reactor referred to as a first settling device; and optionally, a first fractionating tower for separating oil and gas from the first settling device.

[0052] (6) An apparatus for catalytic cracking of olefin-rich gasoline fractions, comprising: a reactor, such as a riser reactor referred to as a second riser reactor; a second settling tank for oil-gas separation from the second riser reactor; and optionally, a second fractionating tower for oil-gas separation from the second settling tank.

[0053] The catalytic conversion device provided by the present invention can be used in a process that includes the conversion method of olefin- and aromatic gasoline described in any of the above technical solutions, producing low-carbon olefins and aromatics from heavy oil.

[0054] The method for converting olefin- and aromatic gasoline provided by this invention can utilize catalytic processing of excess gasoline to produce chemical products, while also yielding aromatics and low-carbon olefins, with a high yield of low-carbon olefins. The ratio of ethylene to propylene products can be adjusted, for example, by changing the ratio of alkane-rich and olefin-rich gasoline fractions obtained from alkane-olefin separation. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of a heavy oil catalytic conversion device provided by the present invention, wherein...

[0056] 1. Heavy oil catalytic cracking unit; 2. Alkane-rich gasoline fraction catalytic cracking unit; 3. Olefin-rich gasoline fraction catalytic cracking unit; 4. Gasoline hydrodesulfurization unit; 5. Aromatics extraction unit; 6. Alkane-olefin separation unit; 7. First fractionation tower (for oil and gas fractionation of unit 2 (for catalytic cracking of alkane-rich gasoline fraction) and unit 3 (for catalytic cracking of olefin-rich gasoline fraction). Detailed Implementation

[0057] The following is in conjunction with the appendix Figure 1 The heavy oil catalytic conversion apparatus provided by this invention further illustrates the method of using heavy oil conversion to produce aromatics and low-carbon olefins:

[0058] At Figure 1In the heavy oil catalytic cracking unit 1, heavy oil feedstock is contacted with heavy oil catalytic cracking catalyst in a riser reactor (also called the third riser reactor) to carry out catalytic cracking reaction, obtaining an oil-catalyst mixture containing oil-gas reaction products and spent catalyst. The oil-catalyst mixture is separated from the spent catalyst and oil-gas reaction products in a settling tank (called the third settling tank), obtaining spent catalyst and oil-gas. The oil-gas is fractionated in a third fractionation tower, and the fractionation results include fractions of catalytic cracked gasoline (called third catalytic gasoline), diesel (called third catalytic diesel), liquefied petroleum gas (called third liquefied petroleum gas), dry gas (called third dry gas), and oil slurry (called third oil slurry). The third liquefied petroleum gas can be further separated to obtain propylene and butene, and the third dry gas can be further separated to obtain ethylene. The spent catalyst is stripped and then enters a regenerator for regeneration.

[0059] Optionally, the third catalytic gasoline is hydrodesulfurized in the catalytic cracking gasoline hydrodesulfurization unit 4 or adsorbed in the adsorption desulfurization unit to obtain desulfurized catalytic cracking gasoline (or desulfurized third catalytic gasoline).

[0060] The third catalytic gasoline or the desulfurized third catalytic gasoline obtained is extracted and separated in the aromatics extraction unit 5 to obtain extracted oil (mainly aromatics, with an aromatics concentration higher than that of the third catalytic gasoline) and raffinate oil (mainly non-aromatics, with an aromatics concentration lower than that of the third catalytic gasoline). The extracted oil is mainly composed of aromatics, and its aromatics content is higher than that of the raffinate oil. The raffinate oil is mainly composed of non-aromatics, and the aromatics content in the raffinate oil is preferably no more than 5% by mass. Existing methods can be used for aromatics extraction.

[0061] The resulting raffinate is separated in alkane-olefin separation unit 6 to obtain an alkane-rich gasoline fraction called first gasoline alkane and an olefin-rich gasoline fraction called first gasoline olefin. Alkane-olefin separation can be performed using a combination of liquid-liquid extraction and extractive distillation processes, which usually also include solvent recovery.

[0062] The first gasoline alkane (obtained as an alkane-rich gasoline fraction from the alkane-alkene separation unit 6) is catalytically cracked in the riser reactor (referred to as the first riser reactor) of the alkane-rich gasoline fraction catalytic cracking unit 2, where it contacts the first catalytic cracking catalyst to form a mixture including oil gas and carbonized catalyst. This mixture is then separated in the first settling tank to separate the oil gas reaction products from the catalyst. The separated oil gas is further separated in a fractionation unit to obtain gasoline, ethylene, propylene, and butene. For example, the separated oil gas can be introduced into a third fractionation tower for separation, or it can be separated in the first fractionation tower, preferably in the first fractionation tower 7. The catalyst, after stripping, enters a regenerator for regeneration.

[0063] The first gasoline olefin undergoes catalytic cracking in the second riser reactor 3, yielding a reaction effluent comprising oil and gas reaction products and a precursor catalyst. The reaction effluent is then separated from the oil and gas reaction products and the precursor catalyst in the second settling tank. The separated oil and gas are further separated in a fractionation unit to obtain gasoline, ethylene, propylene, and butene. For example, fractionation can be carried out in the first, second, or third fractionation tower, preferably in the first fractionation tower 7. Fractionation yields gasoline, diesel, liquefied petroleum gas (LPG), dry gas, and slurry oil. The LPG and dry gas can be further separated to obtain ethylene, propylene, and butene. The gasoline can be introduced into the aromatics extraction unit to extract aromatic components. The diesel and slurry oil can be reintroduced into the third riser reactor for further processing.

[0064] Preferably, the heavy oil catalytic conversion unit includes a third fractionation tower. The oil and gas separated by the first settling tank and the oil and gas separated by the second settling tank are both introduced into the first fractionation tower 7 for first fractionation. The gasoline fraction obtained from the first fractionation is returned to the aromatics extraction unit for extraction. The diesel and slurry obtained from the first fractionation are returned to the heavy oil riser reactor for recycling and further conversion.

[0065] According to the present invention, the catalytic cracking catalyst (first catalytic cracking catalyst, second catalytic cracking catalyst, heavy oil catalytic cracking catalyst) can be prepared according to existing methods. For example, in one embodiment, one or more of the precursors of an inorganic oxide binder, such as boehmite, aluminum sol, silica-alumina sol, and silica-alumina gel, are mixed with clay and decationized water to form a slurry with a solid content of 10-50% by mass. An inorganic acid, such as hydrochloric acid, nitric acid, phosphoric acid, or sulfuric acid, is introduced into the slurry to adjust the pH to 1-4, preferably 2-4. The pH is maintained, and the slurry is aged at 20-80°C for 0-2 hours. Optionally, a sol binder, such as aluminum sol and / or phosphorus-alumina sol, is added, and the mixture is stirred for 0.5-1.5 hours to form a colloid. Molecular sieves (or zeolites) are added to form a catalyst slurry. After continued stirring, the mixture is spray-dried to form microsphere catalysts, which are then calcined, washed, and dried.

[0066] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto. Unless otherwise specified, the instruments and reagents used in the embodiments of the present invention are instruments and reagents commonly used by those skilled in the art.

[0067] The following examples illustrate the catalyst and its preparation method provided by the present invention, wherein the properties of the raw materials used are as follows: kaolin (Suzhou China Kaolin Co., Ltd., solid content 75% by mass), boehmite (Shandong Branch of Aluminum Corporation of China, solid content 65% by mass, first dissolved in 31% hydrochloric acid, the molar ratio of hydrochloric acid (calculated as HCl) to boehmite (calculated as alumina) is 0.20), alumina sol (Qilu Branch of Sinopec Catalyst, alumina content 22.5% by mass), REY molecular sieve (Qilu Branch of Sinopec Catalyst, rare earth (calculated as RE2O3) content 10% by mass); ZRP molecular sieve (Qilu Catalyst Branch, silicon-aluminum ratio (SiO2 / Al2O3 molar ratio) 24.

[0068] Catalyst Preparation Examples 1-3

[0069] Boehmite and kaolin were mixed according to the raw material ratio in Table 1, and prepared into a slurry with a solid content of 28% by mass using decationized water. The mixture was stirred evenly, and the pH of the slurry was adjusted to 2-4 with hydrochloric acid. After maintaining this pH value, the mixture was allowed to stand and age at 60°C for 1 hour. Aluminum sol was then added, and the mixture was stirred for 0.5 hours to form a colloid. Molecular sieve slurry was then added to form a catalyst slurry (solid content of 35% by mass). After continued stirring, the mixture was spray-dried to prepare microsphere catalysts. The microsphere catalysts were then calcined at 500°C for 1 hour, and then washed at 60°C with ammonium sulfate (ammonium sulfate:microsphere catalyst:water = 0.5:1:10) until the sodium oxide content was less than 0.25% by mass. The catalysts were then rinsed with deionized water and filtered, and then dried at 110°C to obtain catalysts A, D, and E, respectively. The specific catalyst formulations are shown in Table 1.

[0070] Table 1. Mass ratio of catalyst formulation (on a dry basis)

[0071] Catalyst number A D E REY molecular sieve 30 2 ZRP molecular sieve 10 30 35 Kaolin 30 38 35 Aluminum Sol 15 15 15 pseudoboehmite 15 15 15

[0072] Example 4,

[0073] The catalytic cracked gasoline, taken from an industrial plant, has the following composition as shown in Table 2, with an initial boiling point of 50°C and a final boiling point of 210°C.

[0074] Table 2

[0075]

[0076] The gasoline described above was extracted in a small laboratory aromatics extraction apparatus and then fractionated to obtain raffinate and extracted oil, the composition of which is shown in Table 3.

[0077] Table 3

[0078] Element Alkanes Olefins Total aromatics BTX Aromatics Composition of extracted oil content, by mass % 0.12 0.01 99.70 32.80 Composition of residual oil content, by mass % 67.54 29.67 2.34 0.34

[0079] The raffinate oil is then subjected to alkane-alkene separation, using the following method:

[0080] The raffinate oil and extraction solvent were subjected to countercurrent liquid-liquid extraction to obtain a first raffinate oil and a first rich solvent (a solvent rich in olefins and some alkanes). The solvent used was a mixture of N-methylpyrrolidone and 3-methylcyclobutane sulfone (mass ratio 8:2). The extraction column had 20 trays, a solvent ratio of 8 by mass, and a column top temperature of 75°C. Then, the first rich solvent and the lean solvent (the above solvent) were subjected to countercurrent extraction distillation to obtain a second raffinate oil and a second rich solvent (a solvent rich in olefins). The extraction column had 30 trays, a solvent ratio of 4 by mass, and a column top temperature of 85°C. The second raffinate oil was mixed with the first raffinate oil, and the resulting raffinate oil was washed with water to obtain an alkane-rich oil (alkane-rich gasoline). The second rich solvent was then distilled to obtain an olefin-rich oil (olefin-rich gasoline). The alkane-olefin separation results are shown in Table 4.

[0081] Table 4

[0082] Composition Alkanes Olefins Total aromatics Among them, BTX aromatics Alkane-rich gasoline fraction, by mass % 90.92 9.08 0 0 Olefin-rich gasoline fraction, % by mass 7.43 84.21 8.36 1.21

[0083] The alkanes in Tables 3 and 4 include n-alkanes, isoalkanes, and cycloalkanes.

[0084] Example 5

[0085] The alkane-rich gasoline fraction was subjected to catalytic cracking reaction in a fixed fluidized bed device using catalysts D and E, which had been aged at 800℃ and 100% vol% steam for 12 hours. The reaction results are shown in Table 5.

[0086] Example 6

[0087] The olefin-rich gasoline fraction was subjected to catalytic cracking reaction in a fixed fluidized bed device using catalysts D and E that had been aged at 800℃ and 100% vol% steam for 12 hours. The reaction results are shown in Table 5.

[0088] Table 5

[0089]

[0090] As can be seen from Table 5, the method provided by the present invention has a high yield of low-carbon olefins, and in particular, a significantly higher yield of BTX aromatics.

[0091] Comparative Example 1

[0092] The raffinate fraction was subjected to catalytic cracking reaction on a fixed fluidized bed device using catalysts D and E, which had been aged at 800℃ and 100% vol% steam for 12 hours. The reaction results are shown in Table 5.

[0093] Comparative Example 2

[0094] The catalytic cracking reaction was carried out directly using the catalytic cracking gasoline described above, with catalysts D and E aged at 800°C and 100% vol% steam for 12 hours. The reaction results are shown in Table 5.

[0095] Example 7

[0096] The atmospheric residue oil as described in Table 6 was reacted in a small fixed-bed reactor using catalyst A aged at 800℃ for 12 hours, at a reaction temperature of 510℃, a catalyst-to-oil ratio of 6 by mass, and a mass hourly space velocity of 10 h⁻¹. -1 .

[0097] Table 6 Properties of Atmospheric Residue Oil

[0098] <![CDATA[Density at 20°C, kg / m 3 > 909.1 Freezing point, ℃ 34 Saturated hydrocarbons, % (w) 72.8 Aromatics, % (w) 24.7 Gel, % (w) 2.5 Asphalt, % (w) 0 Residual char, % (w) 0.22 Viscosity at 80℃, mm² / s 4.748 Viscosity at 100℃, mm² / s 6.417 molecular weight 374 alkaline nitrogen, mg / kg 284 Aniline point, ℃ 84.5 Initial boiling point, ℃ 294 5% (φ), ℃ 354 10% (φ), ℃ 370 30% (φ), ℃ 409 50% (φ), ℃ 437 70% (φ), ℃ 462 Sulfur content, % (w) 1.8 Nitrogen content, % (w) 0.0972 Carbon content, % (w) 85.8 Hydrogen content, % (w) 12.39

Claims

1. A method for converting gasoline containing olefins and aromatics, comprising: (1) Aromatic extraction and separation of olefin and aromatic gasoline is carried out to obtain extracted oil and raffinate oil, wherein the aromatic concentration in the extracted oil is higher than that in the raffinate oil. (2) The raffinate is subjected to alkane-olefin separation to obtain an alkane-rich gasoline fraction and an olefin-rich gasoline fraction. (3) The alkane-rich gasoline fraction is contacted with the first catalytic cracking catalyst to carry out the first catalytic cracking reaction; (4) The olefin-rich gasoline fraction is contacted with the second catalytic cracking catalyst to carry out the second catalytic cracking reaction.

2. The method according to claim 1, wherein, In step (1), the aromatic content of the raffinate is preferably less than 5% by mass; In one embodiment, the aromatic hydrocarbon extraction and separation includes the step of contacting the aromatic hydrocarbon and olefin-containing gasoline with an extraction solvent in an extraction tower; optionally, the extraction solvent used for aromatic hydrocarbon extraction is one or a mixture of multiples of sulfolane, tetraethylene glycol, or n-formylmorpholine; in another embodiment, an extraction-solvent recovery process is adopted, wherein the extraction tower has 3 to 10 theoretical plates, an operating temperature of 60 to 140°C, and a solvent ratio of 3 to 6; the recovery tower has 10 to 30 theoretical plates, a bottom temperature of 170 to 190°C, and a reflux ratio of 0.5 to 2.

3. The method according to claim 1 or 2, wherein, In step (2), the alkane-rich gasoline fraction has an olefin mass fraction of less than 10% by mass, for example, 2-10% by mass, and an alkane mass fraction of not less than 80% by mass, for example, 80-95% by mass. Optionally, the total aromatic content does not exceed 10% by mass, for example, 2-5% by mass. The olefin-rich gasoline fraction (referred to as the first gasoline olefin) has an alkane mass fraction of less than 10% by mass, for example, 2-5% by mass, a total aromatic content of not more than 10% by mass, and an olefin content of not less than 85% by mass, for example, 85-95% by mass. Optionally, the total aromatic content does not exceed 10% by mass, for example, 3-6% by mass. In one embodiment, the method for alkane-alkene separation includes contacting the raffinate with an alkane-alkene separation solvent in a liquid-liquid extraction tower to obtain a component rich in olefins and solvent, and a component rich in alkanes; the component rich in olefins and solvent is further separated, for example, by extractive distillation in an extractive distillation tower, to obtain an alkane-alkene separation solvent and an olefin-rich gasoline fraction; the component rich in alkanes is further separated by removing the alkane-alkene separation solvent, for example by fractional distillation, to obtain an alkane-rich gasoline fraction and solvent; the solvent used for alkane-alkene separation is, for example, an amide compound, a glycol compound, a glycol ether compound, or a lactone compound. The alkane-alkene separation comprises one or a mixture of sulfone compounds; in one embodiment, the alkane-alkene separation employs a liquid-liquid extraction-extractive distillation-solvent recovery process; the liquid-liquid extraction column has a top temperature of 50-90°C, a solvent ratio of 4-12 (mass ratio), and 8-30 theoretical plates; the extractive distillation column has a top temperature of 70-90°C, a bottom temperature of 120-160°C, a solvent ratio of 2-4, and 20-50 theoretical plates; the solvent recovery column has a top temperature of 55-80°C, a bottom temperature of 160-180°C, a reflux ratio of 0.3-0.6, and 8-40 theoretical plates. The amide compounds include one or more of N,N-dimethylformamide, N-formylmorpholine, 1,3-dimethyl-2-imidazolinone, and N-methylpyrrolidone; the glycol compounds include one or more of diethylene glycol, triethylene glycol, and tetraethylene glycol; glycol ether compounds include one or more of diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, and tetraethylene glycol monomethyl ether; lactone compounds include one or more of γ-butyrolactone, γ-valerolactone, and δ-valerolactone; and sulfone compounds include one or more of sulfolane, 3-methylsulfolane, dimethyl sulfone, and dimethyl sulfoxide.

4. The method according to claim 1, characterized in that, The first catalytic cracking catalyst and the second catalytic cracking catalyst can be the same catalyst or different catalysts; In one embodiment, the first catalytic cracking catalyst and the second catalytic cracking catalyst each contain (on a dry basis by weight): 0.01 to 40% by mass, for example, 10 to 40% by mass, of mesoporous zeolite, and 0.01 to 80% by mass, preferably 60 to 90% by mass, of a support; Preferably, the first catalytic cracking catalyst and the second catalytic cracking catalyst each contain (on a dry basis by weight): 0.01–10% by mass, preferably 5–10% by mass, macroporous zeolite and / or 0.01–40% by mass, preferably 20–30% by mass, mesoporous zeolite and 0.01–80% by mass, preferably 50–70% by mass, support; in one embodiment, in the first catalytic cracking catalyst and / or the second catalytic cracking catalyst, the content of mesoporous zeolite is greater than the content of macroporous zeolite, for example, the mass ratio of mesoporous zeolite to macroporous zeolite is 1–25:1, for example 10–20:1 or 2:1–3:

1.

5. The method according to claim 1, characterized in that, The olefin- and aromatic gasoline is catalytic cracked gasoline and / or catalytic cracked gasoline after desulfurization; the sulfur content in the olefin- and aromatic gasoline fraction is preferably no more than 10 ppm by mass; in one embodiment, the olefin- and aromatic gasoline is a heavy gasoline fraction with an initial boiling point greater than 50°C (e.g., an initial boiling point of 50–70°C), for example, the olefin- and aromatic gasoline has a boiling range between 50 and 220°C.

6. The method according to claim 1 or 5, characterized in that, The olefin- and aromatic gasoline is obtained by catalytic cracking of heavy oil feedstock, and by separating the products of the heavy oil catalytic cracking reaction in a fractionation unit and optionally by desulfurization treatment. In one embodiment, the reaction conditions for the catalytic cracking reaction of the heavy oil feedstock include: a reaction temperature of 450–650°C, for example, 480–530°C; a catalyst-to-oil ratio of 3–20:1 (mass ratio), for example, 4–10:1; and a reaction time of 1–15 seconds, for example, 1.5–5 seconds; wherein the heavy oil feedstock is one or more of atmospheric wax oil, atmospheric residue oil, vacuum wax oil, and vacuum residue oil. Optionally, the heavy oil catalytic cracking reaction using heavy oil feedstock uses a heavy oil catalytic cracking catalyst (based on dry weight) containing 0.01–40% by mass, preferably 20–35% by mass, of macroporous zeolite and / or 0.01–30% by mass, for example 1–15% by mass, of mesoporous zeolite and 0.01–80% by mass, for example 60–80% by mass, of a support; in one embodiment, the content of mesoporous zeolite in the heavy oil catalytic cracking catalyst is less than the content of macroporous zeolite, for example, the mass ratio of mesoporous zeolite to macroporous zeolite is 1:3 to 1:

5.

7. The method according to any one of claims 4 to 6, characterized in that, Each of the first catalytic cracking catalyst, the second catalytic cracking catalyst, and the heavy oil catalytic cracking catalyst includes a support; the support includes clay and a binder, wherein the clay is one or more of the following: kaolin, hydrous kaolin, montmorillonite, diatomaceous earth, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite, and rettoiter; and the binder is one or more of the following: alumina sol, silica sol, phosphoalumina sol, and colloidal boehmite. The macroporous zeolite is one or more of Y-type molecular sieves and MCM molecular sieves; the mesoporous zeolite is one or more of ZSM-5 molecular sieves, IM-5 molecular sieves, and β molecular sieves; the Y-type molecular sieve is one or more of REY molecular sieves, HY molecular sieves, REHY molecular sieves, USY molecular sieves, and REUSY molecular sieves; the ZSM-5 molecular sieve is one or more of HZSM-5 molecular sieves, rare earth-containing ZSM-5 molecular sieves such as ZRP molecular sieves, phosphorus and Fe-containing ZSM-5 molecular sieves such as ZSP molecular sieves, and phosphorus-modified ZSM-5 molecular sieves.

8. The method according to any one of claims 1 to 7, characterized in that, The reaction products of the first catalytic cracking are separated to obtain a first gasoline fraction; the reaction products of the second catalytic cracking are separated to obtain a second gasoline fraction; the olefin- and aromatic-containing gasoline fraction includes the first gasoline fraction and the second gasoline fraction; or... The reaction products of the first catalytic cracking and the reaction products of the second catalytic cracking are mixed to separate a gasoline fraction (referred to as the fourth gasoline fraction), and the olefin- and aromatic gasoline fraction includes the separated fourth gasoline fraction; or, The reaction products of the first catalytic cracking and the second catalytic cracking are separated from the reaction products of the heavy oil catalytic cracking in the fractionation unit (first fractionation unit) to obtain the gasoline fraction containing olefins and aromatics.

9. The method according to any one of claims 1 to 8, characterized in that, The conditions for the first catalytic cracking reaction include: a reaction temperature of 550–750°C, preferably 580–680°C; a catalyst-to-oil ratio (mass ratio) of 5–30:1, preferably 15–25; and a reaction time of 1–15 seconds, preferably 3–10 seconds. The conditions for the second catalytic cracking include: a reaction temperature of 350-650℃, preferably 450-620℃ or 520-610℃; an agent-to-oil ratio (mass ratio) of 5-20:1, preferably 5-10; and a reaction time of 1-15 seconds, preferably 2-8 seconds.

10. A method for converting olefin- and alkane-containing hydrocarbon oil, comprising separating the olefin- and alkane-containing hydrocarbon oil into alkane-rich fractions and olefin-rich fractions, and then converting the alkane-rich fractions and olefin-rich fractions separately in different reactors. This method can achieve better ethylene and propylene yields than non-separation conversion; optionally, the olefin- and alkane-containing hydrocarbon oil has a boiling range of 50-220°C, and in one embodiment, the boiling range of the olefin- and alkane-containing hydrocarbon oil is 50-80°C.

11. A heavy oil catalytic conversion unit, comprising: (1) A heavy oil catalytic cracking unit, comprising: a heavy oil riser reactor for carrying out heavy oil catalytic cracking, a settling device for separating oil from the heavy oil riser reactor, referred to as the third settling device, and a third fractionating tower for separating the oil and gas separated by the third settling device, wherein the third fractionating tower can fractionate to obtain catalytic cracked gasoline. (2) Optional catalytic cracking gasoline desulfurization unit; (3) An aromatic extraction unit for extracting aromatics from the catalytic cracking gasoline and / or the desulfurized catalytic cracking gasoline from a desulfurization unit such as a hydrodesulfurization unit, to obtain raffinate and extracted oil. (4) Alkylene separation unit, used to separate alkane and alkene from raffinate oil to obtain olefin-rich gasoline fraction and alkane-rich gasoline fraction; (5) An apparatus for catalytic cracking of alkane-rich gasoline fractions, for carrying out a first catalytic cracking, in one manner comprising: a riser reactor, referred to as a first riser reactor; a settling tank for separating oil from the first riser reactor, referred to as a first settling tank; and optionally, a first fractionating tower for separating oil and gas from the first settling tank. (6) An apparatus for catalytic cracking of olefin-rich gasoline fractions, for carrying out a second catalytic cracking, one embodiment comprising: a riser reactor, referred to as a second riser reactor, a second settling tank for oil-gas separation from the second riser reactor, and optionally, a second fractionating tower for oil-gas separation from the second settling tank.

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