Catalyst for producing light aromatic hydrocarbon and preparation method and catalytic conversion method thereof

Abstract

The invention discloses a catalyst for producing light aromatic hydrocarbon and a preparation method and a catalytic conversion method thereof. Heavy raw oil is used as a raw material, two catalytic cracking processes are adopted, a gasoline cutting device and an aromatic hydrocarbon extraction device are arranged between the two catalytic cracking processes, and materials with different properties obtained through cutting or fractionation are subjected to extraction, reaction or circulation; and the second catalytic cracking catalyst is formed by simultaneously compounding a macroporous molecular sieve, alkali magnesium zeolite and a ZSM-5 molecular sieve with a carrier, so that a stepped pore structure is formed, and the selectivity and the yield of light aromatic hydrocarbon are improved.

Description

Technical Field

[0001] The invention belongs to the field of petroleum processing, and specifically relates to a catalyst for producing light aromatics, a preparation method thereof, and a catalytic conversion method. Background Art

[0002] In recent years, the rapid development of the polyester industry in China and the world has promoted the demand for terephthalic acid (PTA), polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), resulting in an increase in the market demand for paraxylene (PX). This has not only promoted the development of aromatic process technology, but also promoted the improvement of the production and operation level of aromatic units and the speed of unit construction. In the next few years, in addition to tapping the potential and expanding the capacity of existing PX units, the rational development and selection of complete sets of aromatic process technologies and the expansion of raw material sources are also urgent issues to be solved.

[0003] From 2030 to 2060, the electric revolution is unstoppable, gasoline consumption will decrease year by year, and will eventually be almost completely replaced by new energy. FCC, as a device for producing gasoline, must gradually transform into a device for producing other high value-added products. my country currently has about 180 catalytic cracking units with a total processing capacity of about 200 million tons. According to a gasoline yield of 42-45%, it can produce about 90 million tons of catalytic gasoline.

[0004] One of the raw materials for aromatics is petroleum, and there are two process routes: one is to obtain it through catalytic reforming of naphtha and extraction of aromatics; the other is to obtain low-value-added aromatic raw materials through hydrogenation and aromatic extraction of ethylene cracking gasoline, a by-product of the ethylene plant, and then convert it into high-value-added aromatic products. Catalytic cracking gasoline can be catalytically cracked again to produce more aromatics, which can expand the technology of aromatic raw materials.

[0005] Catalytic cracking gasoline is rich in aromatics, and its aromatics are mainly light aromatics such as benzene, toluene, and xylene. It is a valuable and available aromatic resource. Summary of the invention

[0006] In order to solve the problems in the prior art, the present invention uses heavy crude oil as raw material and utilizes a catalytic device combination to process excess catalytic cracking gasoline products to produce light aromatics, which has important practical significance.

[0007] The present invention provides a catalyst for the catalytic cracking process of producing light aromatics. The catalyst contains, based on the dry weight of the catalyst, 10-30wt% of a large-pore molecular sieve, 3-10wt% of ferrierite, 8-25wt% of a ZSM-5 type molecular sieve, and the rest is a carrier and a binder; wherein the large-pore molecular sieve includes a Y-type molecular sieve and / or an MCM molecular sieve; and the proportion of the large-pore molecular sieve does not exceed half of the sum of the ferrierite and the ZSM-5 molecular sieve.

[0008] The catalytic cracking process catalyst of the present invention can simultaneously take into account high raw material conversion rate and high light aromatics selectivity.

[0009] The second object of the present invention is to provide a method for preparing the above catalyst, which specifically comprises the following steps:

[0010] The inorganic oxide binder precursor is mixed with the carrier and prepared into a slurry with decationized water, and then an inorganic acid is added to adjust the pH of the slurry to 1-4, and the slurry is allowed to stand for aging, and a sol is added, and a colloid is formed by stirring, and Y-type molecular sieve, MCM-type molecular sieve, alkali magnesium zeolite and ZSM-5 molecular sieve are added to form a catalyst slurry; after continuing to stir, the slurry is spray-dried to form a microsphere catalyst; and the microsphere catalyst is then calcined, washed with ammonium sulfate, rinsed with deionized water, filtered, and dried to prepare the catalyst for the above-mentioned catalytic cracking process for producing light aromatics.

[0011] The third object of the present invention is to provide a catalytic conversion method for producing light aromatics, comprising the following steps:

[0012] (1) subjecting the heavy crude oil to a first catalytic cracking reaction in a first catalytic cracking reaction unit, and obtaining a first catalytic gasoline, a first catalytic diesel, a first liquefied gas, a first dry gas and a first oil slurry after a first fractionation;

[0013] (2) the first catalytic gasoline is cut and distilled in a gasoline cutting and distillation device to obtain a gasoline light fraction and a gasoline heavy fraction;

[0014] (3) extracting the gasoline heavy fraction in an aromatics extraction unit to obtain gasoline heavy fraction raffinate;

[0015] (4) mixing the gasoline light fraction and the gasoline heavy fraction raffinate in a second catalytic cracking reaction unit to carry out a second catalytic cracking reaction, and after a second fractionation, obtaining a second catalytic gasoline, a second catalytic diesel, a second liquefied gas, a second dry gas, and a second oil slurry;

[0016] (5) the second catalytic gasoline returns to the gasoline cutting distillation device;

[0017] (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit;

[0018] Wherein, the catalyst for the second catalytic cracking reaction in step (4) is the above catalyst or the catalyst prepared by the above preparation method.

[0019] In the catalytic conversion method of the present invention, there is no special requirement for the catalyst used in the first catalytic cracking in step (1). The above-mentioned catalyst of the present invention or a conventional catalytic cracking catalyst in the art can be used.

[0020] The present invention designs the above-mentioned catalytic conversion method route, uses heavy crude oil as raw material, adopts two catalytic cracking processes, and provides a gasoline cutting device and an aromatics extraction device between the two catalytic cracking processes, and extracts, reacts or circulates materials of different properties obtained by cutting or fractionation; and the catalyst of the second catalytic cracking reaction adopts the catalyst provided by the above-mentioned present invention, thereby realizing the rational utilization of raw materials and improving the yield and selectivity of the target product light aromatics.

[0021] Beneficial effects:

[0022] The present invention uses heavy crude oil as raw material, adopts two catalytic cracking processes, and provides a gasoline cutting device and an aromatics extraction device between the two catalytic cracking processes, so that materials of different properties obtained by cutting or fractionation are extracted, reacted or circulated; and the second catalytic cracking catalyst is a composite of a large-pore molecular sieve, an alkali magnesium zeolite and a ZSM-5 type molecular sieve and a carrier, which is beneficial to improving the selectivity and yield of light aromatics. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic flow chart of the catalytic conversion method of the present invention;

[0024] Figure 2 It is a schematic diagram of the process of the present invention with a hydrodesulfurization device. DETAILED DESCRIPTION

[0025] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0026] The present invention provides a catalyst for the catalytic cracking process of producing light aromatics. The catalyst comprises, based on the dry weight of the catalyst:

[0027] 10-30wt% macroporous molecular sieve,

[0028] 3-10wt% alkali magnesium zeolite,

[0029] 8-25wt% ZSM-5 type molecular sieve,

[0030] The rest are carrier and binder;

[0031] The large-pore molecular sieve includes Y-type molecular sieve and / or MCM molecular sieve; the proportion of the large-pore molecular sieve does not exceed half of the sum of ferrierite and ZSM-5 molecular sieve.

[0032] Preferably, the catalyst contains:

[0033] 10-30wt% macroporous molecular sieve,

[0034] 3-10wt% alkali magnesium zeolite,

[0035] 8-25wt% ZSM-5 type molecular sieve,

[0036] 25-45wt% clay, 10-20wt% alumina sol and 10-20wt% pseudo-boehmite.

[0037] More preferably, the catalyst comprises:

[0038] 12-18wt% Y-type molecular sieve,

[0039] 3-8wt% MCM type molecular sieve,

[0040] 3-10wt% alkali magnesium zeolite,

[0041] 8-22wt% ZSM-5 type molecular sieve,

[0042] The rest are carrier and binder.

[0043] More preferably,

[0044] The catalyst contains:

[0045] 12-18wt% Y-type molecular sieve,

[0046] 3-8wt% MCM type molecular sieve,

[0047] 3-10wt% alkali magnesium zeolite,

[0048] 8-22wt% ZSM-5 type molecular sieve,

[0049] 25-45wt% clay, 10-20wt% alumina sol and 10-20wt% pseudo-boehmite.

[0050] The contents of pseudo-boehmite and alumina sol are calculated based on the content of Al2O3.

[0051] In the technical solution of the present invention, light aromatics refer to BTX, namely benzene, toluene and xylene.

[0052] According to a specific embodiment of the present invention, the above catalytic cracking process comprises the following steps:

[0053] (1) subjecting the heavy crude oil to a first catalytic cracking reaction in a first catalytic cracking reaction unit, and obtaining a first catalytic gasoline, a first catalytic diesel, a first liquefied gas, a first dry gas and a first oil slurry after a first fractionation;

[0054] (2) the first catalytic gasoline is cut and distilled in a gasoline cutting and distillation device to obtain a gasoline light fraction and a gasoline heavy fraction;

[0055] (3) extracting the gasoline heavy fraction in an aromatics extraction unit to obtain gasoline heavy fraction raffinate;

[0056] (4) mixing the gasoline light fraction and the gasoline heavy fraction raffinate in a second catalytic cracking reaction unit to carry out a second catalytic cracking reaction, and after a second fractionation, obtaining a second catalytic gasoline, a second catalytic diesel, a second liquefied gas, a second dry gas, and a second oil slurry;

[0057] (5) the second catalytic gasoline returns to the gasoline cutting distillation device;

[0058] (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit;

[0059] Wherein, the second catalytic cracking in step (4) is carried out under the catalytic action of the above-mentioned catalyst.

[0060] According to a specific embodiment of the present invention, the ZSM-5 type molecular sieve is selected from one or more of hydrogen-type ZSM-5 molecular sieve and ZRP molecular sieve.

[0061] Among them, the ZRP molecular sieve is obtained by modifying the ZSM-5 molecular sieve with phosphorus.

[0062] According to a specific embodiment of the present invention, the Y-type molecular sieve is one or more of HY molecular sieve, REY molecular sieve and DASY molecular sieve.

[0063] According to a specific embodiment of the present invention, the MCM type molecular sieve is one or more of MCM-22 molecular sieve, MCM-42 molecular sieve, and MCM-48 molecular sieve.

[0064] The ferrierite is preferably a ZSM-35 molecular sieve.

[0065] According to a specific embodiment of the present invention, the carrier is selected from one or more of kaolin, montmorillonite, diatomaceous earth, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite.

[0066] The binder is one or more of aluminum sol, silica sol, phosphate aluminum sol, and peptized pseudo-boehmite.

[0067] The present invention provides a method for preparing the above catalyst, which specifically comprises the following steps:

[0068] The inorganic oxide binder precursor is mixed with the carrier, and it is prepared into a slurry with a solid content of 10-50wt% with decationized water, stirred evenly, and then an inorganic acid is added to adjust the pH of the slurry to 1-4, and the pH value is maintained. After standing and aging for 1 to 2 hours at 20-80°C, Y-type molecular sieve, MCM-type molecular sieve, alkali magnesium zeolite and ZSM-5 molecular sieve are added to form a catalyst slurry. After continued stirring, spray drying is performed to form a microsphere catalyst. The microsphere catalyst is then calcined, washed with ammonium sulfate, rinsed with deionized water, filtered, and dried.

[0069] The inorganic oxide binder precursor is one or more of pseudo-boehmite, aluminum sol, silica sol, silica-alumina sol or gel. The obtained inorganic oxide binder is silicon dioxide (SiO2) and / or aluminum oxide (Al2O3).

[0070] The purpose of washing with ammonium sulfate is to reduce the sodium content in the catalyst.

[0071] The temperature of ammonium sulfate washing is 40-70°C, preferably 60°C.

[0072] The present invention provides a catalytic conversion method for producing light aromatics. Figure 1 , including the following steps:

[0073] (1) subjecting the heavy crude oil to a first catalytic cracking reaction in a first catalytic cracking reaction unit, and obtaining a first catalytic gasoline, a first catalytic diesel, a first liquefied gas, a first dry gas and a first oil slurry after a first fractionation;

[0074] (2) the first catalytic gasoline is cut and distilled in a gasoline cutting and distillation device to obtain a gasoline light fraction and a gasoline heavy fraction;

[0075] (3) extracting the gasoline heavy fraction in an aromatics extraction unit to obtain gasoline heavy fraction raffinate;

[0076] (4) mixing the gasoline light fraction and the gasoline heavy fraction raffinate in a second catalytic cracking reaction unit to carry out a second catalytic cracking reaction, and after a second fractionation, obtaining a second catalytic gasoline, a second catalytic diesel, a second liquefied gas, a second dry gas, and a second oil slurry;

[0077] (5) the second catalytic gasoline returns to the gasoline cutting distillation device;

[0078] (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit;

[0079] Wherein, the catalyst for the second catalytic cracking reaction in step (4) is the above catalyst or the catalyst prepared by the above preparation method.

[0080] In the technical scheme of the present invention, for the process route of the present invention, the second catalytic cracking reaction uses a catalyst containing large-pore molecular sieves, alkali magnesium zeolite, and ZSM-5 type molecular sieves at the same time, especially a catalyst containing Y-type molecular sieves, MCM-type molecular sieves, alkali magnesium zeolite, and ZSM-5 type molecular sieves at the same time, which helps to improve the yield and selectivity of light aromatics in its products.

[0081] According to a specific embodiment of the present invention, in step (1), the heavy feedstock oil is selected from one or more of atmospheric residue oil, vacuum residue oil, hydrogenated residue oil, hydrogenated tail oil, and coker wax oil.

[0082] According to a specific embodiment of the present invention, step (1) specifically includes the following steps: subjecting the heavy crude oil to a first catalytic cracking reaction in a first catalytic cracking reactor to obtain a first reaction effluent; separating the first catalytic cracking reaction product and the first catalytic cracking spent catalyst in the first settling vessel of the first reaction effluent; and subjecting the separated first catalytic cracking reaction product to a first fractionation in a first fractionation tower to obtain a first catalytic gasoline, a first catalytic diesel, a first liquefied gas, a first dry gas and a first oil slurry.

[0083] According to a specific embodiment of the present invention, the first catalytic cracking reactor is one of a fixed bed reactor, a riser reactor and a fluidized bed reactor.

[0084] According to a specific embodiment of the present invention, in step (1), the conditions of the first catalytic cracking reaction include: temperature of 450-650° C.; catalyst-oil weight ratio of 1:3-20:1; reaction time of 1-15 seconds.

[0085] According to a specific embodiment of the present invention, the initial distillation point of the gasoline light fraction is 25-35°C, and the final distillation point is 75-95°C.

[0086] According to a specific embodiment of the present invention, the initial distillation point of the gasoline heavy fraction is 75-85°C, and the final distillation point is 155-195°C.

[0087] The present invention controls the initial distillation point and the final distillation point of the gasoline light fraction and the gasoline heavy fraction within the above range, which is beneficial to the rational utilization of raw materials and helps to improve the selectivity and yield of light aromatics.

[0088] According to a specific embodiment of the present invention, step (2) also includes the following steps: the first catalytic gasoline is hydrodesulfurized in a gasoline hydrodesulfurization device to obtain hydrodesulfurized gasoline; the hydrodesulfurized gasoline is cut and distilled in a gasoline cutting distillation device to obtain a gasoline light fraction and a gasoline heavy fraction.

[0089] In the technical solution of the present invention, since the raw material is heavy crude oil, the impurity sulfur content is often high. Therefore, in order to improve the quality of the product, the first catalytic gasoline can be subjected to hydrodesulfurization treatment after the first catalytic cracking reaction unit (see Figure 2 ).

[0090] According to a specific embodiment of the present invention, in step (3), the aromatics content in the gasoline heavy fraction raffinate is less than 5 wt%.

[0091] By controlling the reaction conditions of the aromatics extraction unit, the aromatics content in the gasoline heavy fraction raffinate is reduced to less than 5wt%, which is beneficial to improving the selectivity and yield of light aromatics in the final product.

[0092] According to a specific embodiment of the present invention, step (4) specifically includes the following steps: mixing the gasoline light fraction and the gasoline heavy fraction raffinate in a second catalytic cracking reactor to carry out a second catalytic cracking reaction to obtain a second reaction effluent; separating the second catalytic cracking reaction product and the second catalytic cracking spent catalyst in the second settling vessel, and performing a second fractionation of the separated second catalytic cracking reaction product in a second fractionation tower to obtain a second catalytic gasoline, a second catalytic diesel, a second liquefied gas, a second dry gas and a second oil slurry.

[0093] According to a specific embodiment of the present invention, the second catalytic cracking reactor is one of a fixed bed reactor, a riser reactor and a fluidized bed reactor.

[0094] According to a specific embodiment of the present invention, in step (4), the conditions of the second catalytic cracking reaction include: a temperature of 450-550° C., a catalyst-oil weight ratio of 1:5-30:1, and a reaction time of 1-15 seconds.

[0095] The present invention is further illustrated by examples below, but the present invention is not limited thereto. The instruments and reagents used in the examples of the present invention are all commonly used by those skilled in the art unless otherwise specified.

[0096] The properties and sources of the raw materials used in the following examples are as follows:

[0097] Kaolin (Suzhou China Kaolin Company, solid content 75wt%);

[0098] Halloysite (Sanhe white ore from Zunyi, Guizhou, solid content 75wt%);

[0099] Rectorite (Rectorite mine in Zhongxiang, Hubei, solid content 75wt%);

[0100] Montmorillonite (Hongshi Bentonite Company, Chaoyang City, Liaoning Province, solid content 75wt%);

[0101] Pseudo-boehmite (Shandong Aluminum Company, solid content 65wt%, first peptized with 31wt% hydrochloric acid, the molar ratio of hydrochloric acid to pseudo-boehmite calculated as alumina is 0.20);

[0102] Alumina sol (Qilu Catalyst Branch, alumina content 22.5wt%);

[0103] Silica sol (Qingdao Ocean Chemical Co., Ltd., silicon oxide content 25.5wt%, pH 3.0);

[0104] Phosphorus-containing aluminum sol (P content 16wt%, Al content 8wt%, pH value 2.0);

[0105] REY molecular sieve (Qilu Catalyst Branch, rare earth content (RE2O3) is 10wt%);

[0106] DASY molecular sieve (Qilu Catalyst Branch, rare earth content (RE2O3) is 1.5wt%);

[0107] ZRP molecular sieve (Qilu Catalyst Branch), P2O5 phosphorus content 6.21% by weight, NaO content 0.14% by weight, silicon-aluminum ratio 24% by weight;

[0108] MCM-42 molecular sieve: (Adamas Company) Properties: Sodium oxide content 0.02% by weight, silicon-aluminum ratio 23.5% by weight.

[0109] ZSM-35 molecular sieve: (ALFA Company) Properties: Sodium oxide content 0.02% by weight, silicon-aluminum ratio 25% by weight.

[0110] Preparation of Catalyst A:

[0111] The inorganic oxide binder precursor pseudo-boehmite and kaolin were mixed according to the raw material ratio in Table 1, and prepared into a slurry with a solid content of 30wt% with decationized water, stirred evenly, and the pH of the slurry was adjusted to 3 with hydrochloric acid, and the pH value was maintained. After standing and aging for 1 hour at room temperature, REY molecular sieve and ZRP molecular sieve were added to form a catalyst slurry (solid content was 35%wt). After continued stirring, spray drying was performed to prepare a microsphere catalyst. The microsphere catalyst was then calcined at 500°C for 1 hour, and then washed with ammonium sulfate at 60°C (ammonium sulfate: microsphere catalyst: water = 0.5:1:10) until the sodium oxide content was less than 0.25wt%, then rinsed with deionized water and filtered, and then dried at 110°C to obtain catalyst A. The specific catalyst formula is shown in Table 1 (wherein the content of pseudo-boehmite and aluminum sol is calculated as the content of Al2O3).

[0112] Preparation of Catalyst B:

[0113] The inorganic oxide binder precursor pseudo-boehmite and kaolin were mixed according to the raw material ratio in Table 1, and prepared into a slurry with a solid content of 30wt% with decationized water, stirred evenly, and the pH of the slurry was adjusted to 3 with hydrochloric acid, and the pH value was maintained. After standing and aging for 1 hour at room temperature, REY molecular sieve, MCM-42 molecular sieve, ZRP molecular sieve and ZSM-35 molecular sieve were added to form a catalyst slurry (solid content was 35%wt). After continued stirring, spray drying was performed to prepare a microsphere catalyst. The microsphere catalyst was then calcined at 500°C for 1 hour, and then washed with ammonium sulfate at 60°C (ammonium sulfate: microsphere catalyst: water = 0.5:1:10) until the sodium oxide content was less than 0.25wt%, followed by rinsing with deionized water and filtering, and then drying at 110°C to obtain catalyst B. The specific catalyst formula is shown in Table 1 (wherein the content of pseudo-boehmite and aluminum sol is calculated as the content of Al2O3).

[0114] Preparation of Catalyst C:

[0115] Other methods and raw materials are the same as those for the preparation of catalyst B, except that ZRP molecular sieve and ZSM-35 molecular sieve are not contained. The specific composition is shown in Table 1.

[0116] Preparation of Catalyst D:

[0117] Other methods and raw materials are the same as those for the preparation of catalyst B, except that it does not contain ZSM-35 molecular sieve. The specific composition is shown in Table 1.

[0118] Preparation of Catalyst E:

[0119] The other methods and raw materials are the same as those for the preparation of catalyst B, except that it does not contain ZRP molecular sieve. The specific composition is shown in Table 1.

[0120] Preparation of Catalyst M:

[0121] The other methods and raw materials are the same as those for the preparation of catalyst B, except that MCM-42 molecular sieve is not contained. The specific composition is shown in Table 1.

[0122] Preparation of Catalyst N:

[0123] Other methods and raw materials are the same as those for the preparation of catalyst B, except that REY molecular sieve is not contained. The specific composition is shown in Table 1.

[0124] Table 1 Mass ratio of catalyst formula

[0125]

[0126] Example 1

[0127] (1) Reaction in the first catalytic cracking reaction unit

[0128] Atmospheric residue oil (specific properties see Table 2) was used as raw material, and the reaction was carried out in a small fixed bed reactor. Catalyst A aged at 800°C for 12 hours was used, the reaction temperature was 510°C, the catalyst-oil ratio was 6, and the space velocity was 10h. -1 After the reaction products and the spent catalyst are separated in a settler, fractionation is performed in a fractionating tower to obtain the product distribution shown in Table 3 and the gasoline PONA composition shown in Table 4.

[0129] Table 2 Properties of atmospheric residue

[0130]

[0131]

[0132] Table 3

[0133] Yield, wt%: First dry gas 1.36 First liquefied gas 18.07 First Catalytic Gasoline 49.82 First catalytic diesel 15.79 First slurry 8.77 Coke 6.19 Conversion rate, wt% 75.44

[0134] Table 4 Composition of the first catalytic gasoline PONA

[0135] CNum nP iP O N A CSum 2 0 0 0 0 0 0 3 0 0 0 0 0 0 4 0.81 0.42 2.12 0 0 3.35 5 1.24 9.73 10.27 0 0 21.24 6 0.75 8.27 6.96 1.82 0.66 18.46 7 0.7 3.65 4.41 2.78 3.6 15.14 8 0.38 3.26 2.73 1.28 7.47 15.12 9 0.25 1.88 1.27 0.56 8.4 12.36 10 0.34 1.47 0.7 0.24 5.72 8.47 11 0.3 2.05 0.35 0.06 1.84 4.61 12 0.1 0.9 0 0 0 1 Total: 4.87 31.63 28.81 6.75 27.69 99.75

[0136] Among them, nP represents straight-chain alkanes, iP represents isoalkane, O represents olefinic hydrocarbons, N represents cycloalkaneic hydrocarbons, and A represents aromatic hydrocarbons.

[0137] (2) Gasoline cutting and distillation

[0138] The first catalytic gasoline obtained in step (1) is cut and distilled to obtain a gasoline light fraction and a gasoline heavy fraction. The properties of the two are shown in Table 5:

[0139] Table 5

[0140] Initial distillation point (℃) Final distillation point(℃) Gasoline light fraction 25 90 Gasoline heavy fraction 80 190

[0141] (3) Aromatics extraction

[0142] The heavy fraction of gasoline obtained in step (2) is subjected to aromatic extraction to obtain the PONA composition of the extracted raffinate oil as shown in Table 6:

[0143] Table 6

[0144] CNum nP iP O N A CSum 6 1.89 20.89 17.48 4.53 0.00 46.39 7 1.08 7.87 7.18 4.64 0.19 20.95 8 0.61 4.84 3.06 1.76 0.42 10.69 9 0.50 3.53 2.11 1.01 0.58 7.73 10 0.64 2.78 1.36 0.56 0.80 6.54 11 0.66 3.48 0.61 0.17 0.97 5.96 12 0.34 1.39 0.00 0.00 0.00 1.73 Total: 5.71 44.77 31.80 12.68 2.95 100.00

[0145] (4) Reaction in the second catalytic cracking reaction unit

[0146] The gasoline light fraction obtained in step (2) and the raffinate obtained in step (3) are mixed to carry out a second catalytic cracking reaction, and the catalyst B aged at 800°C for 12 hours is used to carry out the reaction in a small fixed bed reactor, the reaction temperature is 520°C, the catalyst-oil ratio is 10 weight ratio, and the weight hourly space velocity is 10h -1 The second catalytic gasoline is returned to the gasoline cutting device, and the second catalytic diesel and the second oil slurry are returned to the first catalytic cracking reaction unit. After the data is stabilized through multiple conversions, the continuous reaction in industry is simulated to obtain the product yield distribution shown in Table 7.

[0147] Example 2

[0148] The other conditions were the same as those in Example 1, except that catalyst B was replaced by catalyst M. The reaction results are shown in Table 7.

[0149] Example 3

[0150] The other conditions were the same as those in Example 1, except that catalyst B was replaced by catalyst N. The reaction results are shown in Table 7.

[0151] Comparative Example 1

[0152] The other conditions were the same as those in Example 1, except that catalyst B was replaced by catalyst C. The reaction results are shown in Table 7.

[0153] Comparative Example 2

[0154] The other conditions were the same as those in Example 1, except that catalyst B was replaced by catalyst D. The reaction results are shown in Table 7.

[0155] Comparative Example 3

[0156] The other conditions were the same as those in Example 1, except that catalyst B was replaced by catalyst E. The reaction results are shown in Table 7.

[0157] Table 7 Product distribution of the second catalytic cracking reaction

[0158]

[0159] Among them, fuel gas refers to methane, ethane, propane, butane, and hydrogen; the yield of chemical raw materials is the sum of the yields of low-carbon olefins such as ethylene, propylene and butene and the yields of light aromatics such as benzene, toluene and xylene.

[0160] By analyzing the data in Table 7, it can be seen from Examples 1-3 and Comparative Examples 1-3 that, in the process system of the present invention, the second catalytic cracking catalyst contains large-pore molecular sieves, alkali magnesium zeolite and ZSM-5 molecular sieves at the same time, which helps to improve the selectivity and yield of light aromatics; in addition, by analyzing Examples 1-3, it can be seen that when MCM molecular sieves, Y-type molecular sieves, alkali magnesium zeolite and ZSM-5 molecular sieves are contained at the same time, the selectivity and yield of light aromatics are higher.

[0161] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0162] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A catalyst for a catalytic cracking process for producing light aromatics, characterized in that: The catalyst comprises, based on the dry weight of the catalyst: 10-30wt% macroporous molecular sieve, 3-10wt% alkali magnesium zeolite, 8-25wt% ZSM-5 type molecular sieve, The rest are carrier and binder; Wherein, the large-pore molecular sieve includes Y-type molecular sieve and / or MCM molecular sieve; the proportion of the large-pore molecular sieve does not exceed half of the sum of ferrierite and ZSM-5 molecular sieve.

2. The catalytic cracking catalyst according to claim 1, characterized in that The catalyst comprises, based on the dry weight of the catalyst: 12-18wt% Y-type molecular sieve, 3-8wt% MCM type molecular sieve, 3-10wt% alkali magnesium zeolite, 8-22wt% ZSM-5 type molecular sieve, The rest are carrier and binder.

3. The catalytic cracking catalyst according to claim 1, characterized in that The catalytic cracking process comprises the following steps: (1) subjecting the heavy crude oil to a first catalytic cracking reaction in a first catalytic cracking reaction unit, and obtaining a first catalytic gasoline, a first catalytic diesel, a first liquefied gas, a first dry gas and a first oil slurry after a first fractionation; (2) the first catalytic gasoline is cut and distilled in a gasoline cutting and distillation device to obtain a gasoline light fraction and a gasoline heavy fraction; (3) extracting the gasoline heavy fraction in an aromatics extraction device to obtain gasoline heavy fraction raffinate; (4) the gasoline light fraction and the gasoline heavy fraction raffinate are mixed in a second catalytic cracking reaction unit to carry out a second catalytic cracking reaction, and after a second fractionation, a second catalytic gasoline, a second catalytic diesel, a second liquefied gas, a second dry gas, and a second oil slurry are obtained; (5) the second catalytic gasoline is returned to the gasoline cutting distillation device; (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit; Wherein, the second catalytic cracking in step (4) is carried out under the catalytic action of the catalyst.

4. The catalytic cracking catalyst according to claim 1, characterized in that The ZSM-5 type molecular sieve is selected from one or more of hydrogen-type ZSM-5 molecular sieve and ZRP molecular sieve; and / or, The Y-type molecular sieve is one or more of HY molecular sieve, REY molecular sieve, and DASY molecular sieve; and / or, The MCM type molecular sieve is one or more of MCM-22 molecular sieve, MCM-42 molecular sieve and MCM-48 molecular sieve.

5. The catalytic cracking catalyst according to claim 1, characterized in that The carrier is selected from one or more of kaolin, montmorillonite, diatomaceous earth, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite.

6. The method for preparing the catalyst according to any one of claims 1 to 5, characterized in that: The specific steps include: The inorganic oxide binder precursor is mixed with the carrier and prepared into a slurry with decationized water, and then an inorganic acid is added to adjust the pH of the slurry to 1-4, and the slurry is allowed to stand for aging, and a sol is added, and a colloid is formed by stirring, and a Y-type molecular sieve, an MCM-type molecular sieve, an alkali magnesium zeolite and a ZSM-5-type molecular sieve are added to form a catalyst slurry; The microsphere catalyst is prepared by spray drying after continued stirring; the microsphere catalyst is then calcined, washed with ammonium sulfate, rinsed with deionized water, filtered, and dried to prepare the catalyst.

7. The preparation method according to claim 6, characterized in that: The temperature of ammonium sulfate washing is 40-70°C, preferably 60°C.

8. A catalytic conversion method for producing light aromatics, characterized in that: The method comprises the following steps: (1) subjecting the heavy crude oil to a first catalytic cracking reaction in a first catalytic cracking reaction unit, and obtaining a first catalytic gasoline, a first catalytic diesel, a first liquefied gas, a first dry gas and a first oil slurry after a first fractionation; (2) the first catalytic gasoline is cut and distilled in a gasoline cutting and distillation device to obtain a gasoline light fraction and a gasoline heavy fraction; (3) extracting the gasoline heavy fraction in an aromatics extraction device to obtain gasoline heavy fraction raffinate; (4) the gasoline light fraction and the gasoline heavy fraction raffinate are mixed in a second catalytic cracking reaction unit to carry out a second catalytic cracking reaction, and after a second fractionation, a second catalytic gasoline, a second catalytic diesel, a second liquefied gas, a second dry gas, and a second oil slurry are obtained; (5) the second catalytic gasoline is returned to the gasoline cutting distillation device; (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit; Wherein, the catalyst for the second catalytic cracking reaction in step (4) is the catalyst described in any one of claims 1 to 4 or the catalyst prepared by the preparation method described in any one of claims 5 to 7.

9. The catalytic conversion method according to claim 8, characterized in that: In the step (1), the heavy feedstock oil is selected from one or more of atmospheric residue oil, vacuum residue oil, hydrogenated residue oil, hydrogenated tail oil, and coker wax oil.

10. The catalytic conversion method according to claim 8, characterized in that: The step (1) specifically comprises the following steps: subjecting the heavy crude oil to a first catalytic cracking reaction in a first catalytic cracking reaction unit to obtain a first reaction effluent; separating the first catalytic cracking reaction product and the first catalytic cracking spent catalyst in a first settler in the first reaction effluent; subjecting the separated first catalytic cracking reaction product to a first fractionation in a first fractionation tower to obtain a first catalytic gasoline, a first catalytic diesel, a first liquefied gas, a first dry gas and a first oil slurry.

11. The catalytic conversion method according to claim 8, characterized in that: In the step (1), the conditions of the first catalytic cracking reaction include: a temperature of 450 to 650° C.; a catalyst to oil weight ratio of 1:3 to 20:1; and a reaction time of 1 to 15 seconds.

12. The catalytic conversion method according to claim 8, characterized in that: The initial distillation point of the gasoline light fraction is 25-35°C, and the final distillation point is 75-95°C.

13. The catalytic conversion method according to claim 8, characterized in that: The initial distillation point of the gasoline heavy fraction is 75-85°C, and the final distillation point is 155-195°C.

14. The catalytic conversion method according to claim 8, characterized in that: The step (2) further comprises the following steps: the first catalytic gasoline is subjected to hydrodesulfurization in a gasoline hydrodesulfurization device to obtain hydrodesulfurized gasoline; the hydrodesulfurized gasoline is subjected to cutting distillation in a gasoline cutting distillation device to obtain the gasoline light fraction and the gasoline heavy fraction.

15. The catalytic conversion method according to claim 8, characterized in that: In the step (3), the aromatic content in the gasoline heavy fraction raffinate is less than 5 wt%.

16. The catalytic conversion method according to claim 8, characterized in that: The step (4) specifically comprises the following steps: the gasoline light fraction and the gasoline heavy fraction raffinate are mixed in a second catalytic cracking reaction unit to carry out a second catalytic cracking reaction to obtain a second reaction effluent; the second reaction effluent is separated from a second catalytic cracking reaction product and a second catalytic cracking spent catalyst in a second settler, and the separated second catalytic cracking reaction product is fractionated for a second time in a second fractionation tower to obtain a second catalytic gasoline, a second catalytic diesel, a second liquefied gas, a second dry gas and a second oil slurry.

17. The catalytic conversion method according to claim 8, characterized in that: In the step (4), the conditions of the second catalytic cracking reaction include: a temperature of 450 to 550° C., a catalyst to oil weight ratio of 1:5 to 30:1, and a reaction time of 1 to 15 seconds.

Images