Catalytic cracking catalyst capable of increasing yield of low-carbon olefins, preparation method of catalytic cracking catalyst and catalytic conversion method of catalytic cracking catalyst

Abstract

The invention discloses a catalytic cracking catalyst for increasing the yield of low-carbon olefins, 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 simultaneously contains ferrierite and ZSM-5 molecular sieves which are compounded with the carrier, so that high conversion rate and high selectivity can be taken into account, and the selectivity and yield of low-carbon olefins can be improved.

Description

Technical Field

[0001] The invention belongs to the field of petroleum processing, and specifically relates to a catalytic cracking catalyst capable of producing more low-carbon olefins, a preparation method thereof, and a catalytic conversion method. Background Art

[0002] As important basic chemical raw materials, ethylene and propylene have a rich downstream industrial chain and a large market scale. In recent years, driven by the demand of downstream industries, the demand for ethylene and propylene has grown rapidly at home and abroad. At the same time, under the background of accelerating energy transformation driven by the "dual carbon" goal, transportation fuels produced by the refining industry, especially catalytic cracking gasoline, are gradually being replaced by new energy, and their market share is gradually shrinking. Therefore, the transformation of refining to chemical industry has become the mainstream trend of the industry.

[0003] Before 2030, the number of traditional fuel vehicles will still be very large, and the corresponding apparent consumption of gasoline and diesel will remain at a high level. Gasoline consumption will peak in 2025 and then gradually decrease. Diesel consumption will slowly decline, ethylene and propylene demand will rise rapidly, and PX demand will still increase. FCC will still be the main device for gasoline production for a period of time, and will also produce basic chemical raw materials such as ethylene and propylene.

[0004] In recent years, in order to meet the development needs of the low-carbon olefin industry, many foreign scientists have been committed to developing new catalytic cracking processes, hoping to improve the yield of low-carbon olefins, enhance the adjustability of propylene / ethylene, reduce energy consumption, and reduce coking during the cracking process. Among the new low-carbon olefin preparation technologies based on light crude oil, the more representative foreign technology is the naphtha catalytic cracking process (K-COT) jointly developed by SK Chemical of South Korea and KBR Engineering of the United States. This process mainly uses a coaxial parallel fluidized catalytic cracking reactor system and a proprietary ZSM-5 molecular sieve catalyst. Compared with the traditional steam cracking process, it can significantly improve the yield of ethylene and propylene, and at the same time ensure that the ratio of propylene to ethylene is about 1:1. However, the raw material type used in this process is mainly straight-run naphtha, and its family composition is mainly paraffin and cycloalkanes, which is still a certain distance from the composition of catalytic cracking gasoline.

[0005] my country currently has about 180 catalytic cracking units with a total processing capacity of about 200 million tons. Based on a gasoline yield of 42-45%, it can produce about 90 million tons of catalytic gasoline. Summary of the invention

[0006] In order to overcome the problems of the prior art, the present invention provides a catalyst for a catalytic cracking process for producing light olefins and combines it with a combined process method, which can realize the processing of excess gasoline to produce chemical products, and has important practical significance.

[0007] The present invention provides a catalyst for a catalytic cracking process for producing light olefins. The catalyst comprises, based on the dry weight of the catalyst:

[0008] 5-30wt% ferrierite,

[0009] 15-40wt% ZSM-5 type molecular sieve,

[0010] The rest are carrier and binder;

[0011] wherein the weight percentage of ferrierite does not exceed the weight percentage of ZSM-5 molecular sieve;

[0012] Preferably, the ferrierite is ZSM-35 molecular sieve.

[0013] The catalytic cracking process catalyst of the present invention takes into account both high conversion rate and high selectivity, and is beneficial to improving the selectivity and yield of light olefins.

[0014] The second object of the present invention is to provide a method for preparing the above catalyst, which specifically comprises the following steps:

[0015] The inorganic oxide binder precursor is mixed with the carrier and prepared into a slurry with decationized water, the solid content of the slurry is preferably 5-40% by weight, then the slurry pH is adjusted to 2-4 by adding an inorganic acid, and the sol is added and stirred to form a colloid, and ferrierite and ZSM-5 molecular sieve are added to form a catalyst slurry; after continued stirring, the slurry is spray-dried to form a microsphere catalyst; the microsphere catalyst is then calcined, washed with ammonium sulfate, rinsed with deionized water, filtered, and dried to prepare the above catalyst. The inorganic oxide binder precursor is preferably pseudo-boehmite and aluminum sol.

[0016] A third object of the present invention is to provide a catalytic conversion method for producing light olefins, comprising the following steps:

[0017] (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;

[0018] (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;

[0019] (3) extracting the gasoline heavy fraction in an aromatics extraction unit to obtain gasoline heavy fraction raffinate;

[0020] (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;

[0021] (5) the second catalytic gasoline returns to the gasoline cutting distillation device;

[0022] (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit;

[0023] 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.

[0024] 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.

[0025] 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 olefins.

[0026] Beneficial effects:

[0027] 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, and extracts, reacts or circulates materials of different properties obtained by cutting or fractionation; and the second catalytic cracking catalyst contains ferrierite and ZSM-5 type molecular sieve composited with a carrier, taking into account high conversion rate and high selectivity, which is beneficial to improving the selectivity and yield of light olefins. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic flow chart of the catalytic conversion method of the present invention;

[0029] Figure 2 It is a schematic diagram of the process of the present invention with a hydrodesulfurization device. DETAILED DESCRIPTION

[0030] 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.

[0031] The present invention provides a catalyst for a catalytic cracking process for producing light olefins. The catalyst comprises, based on the dry weight of the catalyst:

[0032] 5-30wt% ferrierite,

[0033] 15~40wt% ZSM-5 type molecular sieve,

[0034] The rest are carrier and binder;

[0035] wherein the weight percentage of ferrierite does not exceed the weight percentage of ZSM-5 molecular sieve;

[0036] Preferably, the ferrierite is ZSM-35 molecular sieve.

[0037] More preferably, the catalyst comprises:

[0038] 5-15wt% ferrierite,

[0039] 15~25wt% ZSM-5 type molecular sieve,

[0040] The rest are carrier and binder.

[0041] Further preferably, the catalyst contains:

[0042] 5-15wt% ferrierite,

[0043] 15~25wt% ZSM-5 type molecular sieve,

[0044] 30-50wt% of kaolin, 10-20wt% of aluminum sol and 5-10wt% of pseudo-boehmite.

[0045] According to a specific embodiment of the present invention, the weight ratio of ZSM-5 zeolite to ferrierite, calculated on a dry basis, is (1-5):1, preferably 2:1.

[0046] In the technical solution of the present invention, low-carbon olefins refer to C2-C4 olefins.

[0047] According to a specific embodiment of the present invention, the above catalytic cracking process comprises the following steps:

[0048] (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;

[0049] (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;

[0050] (3) extracting the gasoline heavy fraction in an aromatics extraction unit to obtain gasoline heavy fraction raffinate;

[0051] (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;

[0052] (5) the second catalytic gasoline returns to the gasoline cutting distillation device;

[0053] (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit;

[0054] Wherein, the second catalytic cracking in step (4) is carried out under the catalytic action of the above-mentioned catalyst.

[0055] In the technical solution of the present invention, for the process route of the present invention, the second catalytic cracking reaction uses a catalyst containing both ferrierite and ZSM-5 molecular sieves, which helps to improve the yield and selectivity of light olefins in its products.

[0056] 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.

[0057] Among them, the ZRP molecular sieve is obtained by modifying the ZSM-5 molecular sieve with phosphorus.

[0058] According to a specific embodiment of the present invention, the carrier is selected from one or more of kaolin, montmorillonite, diatomite, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite. The binder is one or more of alumina sol, silica sol, phosphate aluminum sol and peptized pseudo-boehmite.

[0059] The carrier is preferably kaolin, and the preferred binders are pseudo-boehmite and alumina sol. Preferably, the catalyst contains 15-25 wt% ZSM-5 zeolite, 5-15 wt% ferrierite, 30-50 wt% kaolin, 10-20 wt% alumina sol and 5-10 wt% pseudo-boehmite on a dry basis. The weight ratio of ZSM-5 zeolite to ferrierite is 1 to 5:1 on a dry basis, preferably 1.5 to 2.5:1, and more preferably 2:1, and the weight ratio of alumina sol to pseudo-boehmite is preferably 0.8 to 1.2:1, for example 1:1 on a dry basis. The ZSM-5 molecular sieve is, for example, a ZRP molecular sieve.

[0060] The present invention provides a method for preparing the above catalyst, which specifically comprises the following steps:

[0061] 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, and stirred evenly, and then an inorganic acid is added to adjust the pH of the slurry to 2-4, preferably to 3-4, and the pH value is maintained. After standing and aging for 1-2 hours at 20-80°C, ferriterite 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.

[0062] 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).

[0063] The purpose of washing with ammonium sulfate is to reduce the sodium content in the catalyst.

[0064] The temperature of ammonium sulfate washing is 40-70°C, preferably 60°C.

[0065] The present invention provides a catalytic conversion method for producing light olefins. Figure 1 , including the following steps:

[0066] (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;

[0067] (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;

[0068] (3) extracting the gasoline heavy fraction in an aromatics extraction unit to obtain gasoline heavy fraction raffinate;

[0069] (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;

[0070] (5) the second catalytic gasoline returns to the gasoline cutting distillation device;

[0071] (6) the second catalytic diesel and the second slurry oil are returned to the first catalytic cracking reaction unit;

[0072] 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.

[0073] In the technical solution of the present invention, since aromatic hydrocarbons are mainly concentrated in the heavy fraction, cutting first and then extracting and mixing can reduce the processing capacity of the extraction device compared to directly extracting the product without cutting.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] According to a specific embodiment of the present invention, in 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.

[0078] According to a specific embodiment of the present invention, the first catalytic cracking reaction makes the gasoline contain 20-30 wt% of C5-C8 olefins and no more than 15 wt% of C7-C8 aromatics. In one embodiment, the heavy oil catalytic cracking catalyst used for the heavy oil catalytic cracking reaction includes Y-type molecular sieve and ZSM-5 molecular sieve. For example, based on dry weight, the heavy oil cracking catalyst includes 25-35 wt% of Y-type molecular sieve, 8-15 wt% of ZSM-5 molecular sieve, 25-45 wt% of clay, 10-20 wt% of aluminum sol and 10-20 wt% of pseudo-boehmite.

[0079] 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.

[0080] 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.

[0081] 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 olefins.

[0082] 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.

[0083] 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 ).

[0084] 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%.

[0085] 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 olefins in the final product.

[0086] 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 riser reactor to carry out a second catalytic cracking reaction to obtain a second reaction effluent; separating the second reaction effluent from the second catalytic cracking reaction product and the second catalytic cracking spent catalyst in a second settler, 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.

[0087] According to a specific embodiment of the present invention, in step (4), the conditions of the second catalytic cracking reaction include: a temperature of 450-580° C., a catalyst-oil weight ratio of 1:5-30:1, and a reaction time of 1-15 seconds.

[0088] 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.

[0089] The properties and sources of the raw materials used in the following examples are as follows:

[0090] Kaolin (Suzhou China Kaolin Company, solid content 75wt%);

[0091] Halloysite (Sanhe white ore from Zunyi, Guizhou, solid content 75wt%);

[0092] Rectorite (Rectorite mine in Zhongxiang, Hubei, solid content 75wt%);

[0093] Montmorillonite (Hongshi Bentonite Company, Chaoyang City, Liaoning Province, solid content 75wt%);

[0094] 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);

[0095] Alumina sol (Qilu Catalyst Branch, alumina content 22.5wt%);

[0096] Silica sol (Qingdao Ocean Chemical Co., Ltd., silicon oxide content 25.5wt%, pH 3.0);

[0097] Phosphorus-containing aluminum sol (P content 16wt%, Al content 8wt%, pH value 2.0);

[0098] 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.

[0099] ZSM-35 molecular sieve: (ALFA Company), sodium oxide content 0.02% by weight, silicon-aluminum ratio 25% by weight.

[0100] Preparation of Catalyst A:

[0101] The inorganic oxide binder precursor pseudo-boehmite, aluminum sol 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).

[0102] Preparation of Catalyst F:

[0103] The inorganic oxide binder precursor pseudo-boehmite, aluminum sol 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, 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 F. 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).

[0104] Preparation of Catalyst E:

[0105] The other methods and raw materials are the same as those for the preparation of catalyst F, except that the contents of ZRP molecular sieve and ZSM-35 molecular sieve are different. The specific composition is shown in Table 1.

[0106] Preparation of Catalyst G:

[0107] The other methods and raw materials are the same as those for the preparation of catalyst F, except that the contents of ZRP molecular sieve and ZSM-35 molecular sieve are different. The specific composition is shown in Table 1.

[0108] Preparation of Catalyst H:

[0109] Other methods and raw materials are the same as those for the preparation of catalyst F, except that it does not contain ZRP molecular sieve. The specific composition is shown in Table 1.

[0110] Preparation of Catalyst K:

[0111] Other methods and raw materials are the same as those for the preparation of catalyst F, except that it does not contain ZSM-35 molecular sieve. The specific composition is shown in Table 1.

[0112] Table 1 Catalyst formulation mass ratio

[0113]

[0114] Example 1

[0115] (1) Reaction in the first catalytic cracking reaction unit

[0116] 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℃ for 12h was used, the reaction temperature was 510℃, 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.

[0117] Table 2 Properties of atmospheric residue

[0118]

[0119]

[0120] Table 3

[0121] 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

[0122] Table 4 Composition of the first catalytic gasoline PONA

[0123] 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

[0124] Among them, nP represents straight-chain alkanes, iP represents isomeric alkanes, O represents olefins, N represents cycloalkanes, A represents aromatic hydrocarbons; CNum represents the molecular carbon number.

[0125] (2) Gasoline cutting and distillation

[0126] 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:

[0127] Table 5

[0128]

[0129]

[0130] (3) Aromatics extraction

[0131] 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:

[0132] Table 6

[0133] 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

[0134] (4) Reaction in the second catalytic cracking reaction unit

[0135] The gasoline light fraction obtained in step (2) and the raffinate obtained in step (3) are mixed to carry out a second riser reaction, and the reaction is carried out in a small fixed bed reactor using catalyst F, the reaction temperature is 560°C, the catalyst-oil ratio is 10, and the 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.

[0136] Example 2

[0137] The other conditions were the same as those in Example 1, except that catalyst F was replaced by catalyst E. The reaction results are shown in Table 7.

[0138] Example 3

[0139] The other conditions were the same as those in Example 1, except that catalyst F was replaced by catalyst G. The reaction results are shown in Table 7.

[0140] Comparative Example 1

[0141] The other conditions were the same as those in Example 1, except that catalyst F was replaced by catalyst H. The reaction results are shown in Table 7.

[0142] Comparative Example 2

[0143] The other conditions were the same as those in Example 1, except that catalyst F was replaced by catalyst K. The reaction results are shown in Table 7.

[0144] Table 7 Product distribution of the second catalytic cracking reaction unit

[0145] Product composition Triene yield Ethylene Propylene Butene Fuel gas BTX gasoline Coke Example 1 46.07 9.23 24.62 12.22 4.89 12.16 36.04 0.84 Example 2 44.09 9.56 19.75 14.78 8.88 11.35 34.67 1.01 Example 3 40.53 7.91 21.17 11.45 3.23 9.57 45.72 0.95 Comparative Example 1 18.33 0.02 12.13 6.18 0.08 8.36 73.12 0.11 Comparative Example 2 39.2 9.87 14.12 15.21 10.6 15.75 29.28 5.17

[0146] The fuel gas is methane, ethane, propane, butane and hydrogen; the triene yield is the yield of low-carbon olefins such as ethylene, propylene and butene.

[0147] By analyzing the data in Table 7, it can be seen from Example 1 and Comparative Examples 1-2 that in the process system of the present invention, the second catalytic cracking catalyst contains both alkali magnesium zeolite and ZSM-5 molecular sieve, which helps to improve the selectivity and yield of light olefins.

[0148] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0149] 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 olefins, characterized in that: Based on the dry weight of the catalyst, the catalyst contains 5-30wt% ferrierite, 15~40wt% ZSM-5 type molecular sieve, The rest are carrier and binder; wherein the weight percentage of ferrierite does not exceed the weight percentage of ZSM-5 molecular sieve; Preferably, the ferrierite is ZSM-35 molecular sieve.

2. The catalytic cracking catalyst according to claim 1, characterized in that The weight ratio of ZSM-5 zeolite to ferrierite, calculated on a dry basis, is (1-5):1, preferably 2:

1.

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.

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 sol is added and stirred to form a colloid, and then 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 olefins, 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 5 or the catalyst prepared by the preparation method described in any one of claims 6 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 reactor 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 reactor 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 settling vessel, 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 580° C., a catalyst-oil weight ratio of 1:5 to 30:1, and a reaction time of 1 to 15 seconds.

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