Crude oil direct catalytic cracking method and system for improving heat balance

Abstract

The invention discloses a crude oil direct catalytic cracking method and system for improving heat balance, and the method comprises the following steps: enabling a reduced high-temperature regenerated catalyst to enter the lower part of a first reactor to be in contact with crude oil, sequentially entering the first reactor and a second reactor of a catalytic cracking reactor to carry out catalytic cracking reaction, and carrying out gas-solid separation on a reaction product and a spent catalyst, the spent catalyst is sequentially subjected to steam stripping and scorching regeneration to obtain a regenerated catalyst, and the regenerated catalyst is subjected to reduction activation and then returns to the reactor for recycling; and separating the reaction products to obtain ethylene, propylene, difficult-to-convert components and other products, wherein the difficult-to-convert components enter the third reactor to further react to obtain chemical raw materials such as ethylene and propylene. When the catalytic cracking method and system are used for crude oil catalytic cracking reaction, the crude oil processing flow is further shortened, the utilization rate of crude oil carbon atoms is increased, the yield of chemical raw materials is high, and meanwhile the problem of heat balance is solved.

Description

Technical Field

[0001] The present application relates to the field of petrochemical industry, and in particular, to a method and system for producing chemical raw materials by direct catalytic cracking of crude oil with improved thermal balance. Background Art

[0002] Ethylene, propylene and BTX (benzene-toluene-xylene) are important basic organic chemical raw materials, which can be used to produce a variety of organic chemical products, including many important high-end organic chemicals, which are closely related to people's food, clothing, housing and transportation. The existing technical route for producing propylene and BTX from petroleum is developed on the basis of the traditional petroleum refining process that mainly produces oil products. There are problems such as long production process, low chemical yield and insignificant economic benefits. The technical measure to solve this problem is to develop key core technologies that mainly produce chemicals and can direct the conversion of crude oil hydrocarbon molecules into chemicals. Therefore, in recent years, petrochemical companies at home and abroad have been actively exploring the technical route of directly producing chemicals from crude oil, so as to make the processing path from crude oil to low-carbon olefins and BTX and other chemicals shorter, with lower energy consumption and smaller investment.

[0003] WO2005113722A3 and CN200780047937.2 disclose a process for producing crude oil directly into chemicals, wherein the crude oil directly enters a steam cracking furnace, and is flash evaporated to separate light components and heavy components, the light components (gaseous components) enter the steam cracking furnace for cracking, and the heavy components (liquid components) are used as refinery raw materials.

[0004] CN 201380015214.X discloses a process for producing olefins and aromatics from crude oil by integrating hydroprocessing, steam cracking and catalytic cracking processes. After the crude oil is hydroprocessed, impurities such as sulfur and high-boiling substances are removed, and the hydrogenated products are separated by distillation. The light components enter the steam cracking unit, and the heavy components are subjected to the catalytic cracking unit to maximize the production of olefins.

[0005] CN201780078199.1 discloses a method and system for converting crude oil into petrochemicals and fuel products by integrating steam cracking and fluid catalytic cracking. Crude oil is separated into straight-run naphtha and lighter component fractions, one or more intermediate distillate fractions, and atmospheric residue fractions. Vacuum distillate oil is then separated from the atmospheric residue fraction as a catalytic cracking feedstock. The light fraction is hydrogenated and used as naphtha and diesel fuel oil.

[0006] The above crude oil processing routes all use steam cracking as the main technical means to produce light olefins. Due to the high energy consumption of steam cracking technology and the poor flexibility of product solutions, researchers are also actively developing technical solutions for producing light olefins by catalytic cracking.

[0007] The method for preparing low-carbon olefins and aromatics by catalytic cracking of crude oil disclosed in CN20181189551.1 and CN201811190135.3 comprises the following steps: after desalting and dehydrating the crude oil, the crude oil is divided into light and heavy components, and the light component, i.e., light feed, and the heavy component, i.e., heavy feed, are respectively placed in two catalytic cracking reactors, and are contacted with a high-temperature catalyst under a steam atmosphere to react to produce low-carbon olefins and aromatics. Alternatively, the light component and the heavy component react in different reaction zones of the same reactor.

[0008] CN 201810523356.1 discloses a method for processing a whole fraction of crude oil. The method separates the whole fraction of crude oil to obtain light distillate oil, middle distillate oil and heavy distillate oil. The middle distillate oil and the heavy distillate oil are reacted in a first riser, and the light distillate oil is reacted in a fluidized bed reactor connected in series with the riser. The reaction conditions in the reactor vary according to the properties of the raw materials.

[0009] Existing crude oil catalytic cracking technologies all use crude oil distillation to separate fractions, and still do not avoid the crude oil flash distillation process, failing to achieve a true crude oil direct catalytic cracking technology route. Summary of the invention

[0010] The purpose of this application is to provide a method and system for directly catalytic cracking crude oil to produce chemical raw materials with improved thermal balance based on the current catalytic cracking technology, which can not only improve the yield and selectivity of catalytic cracking of crude oil to produce chemical raw materials such as ethylene and propylene, but also solve the potential problem of insufficient heat in the catalytic cracking reaction of crude oil.

[0011] The first aspect of the present invention provides a method for direct catalytic cracking of crude oil with improved heat balance, comprising:

[0012] (1) A first raw material and a first reduced regenerated catalyst from a catalyst reducer enter a first reactor and a second reactor in sequence to undergo a catalytic cracking reaction;

[0013] (2) The second reduced regenerated catalyst and the fresh catalyst from the catalyst reducer are respectively injected into the pre-lifting section at the bottom of the third reactor, and move upward from the bottom under the action of the pre-lifting medium. The second raw material enters the third reactor through the feeding section of the third reactor, mixes with the existing flow in the reactor and undergoes a cracking reaction. The reaction oil mixture enters the second reactor to continue the cracking reaction;

[0014] (3) The reaction product and the catalyst to be produced obtained in the second reactor enter the oil separation device for gas-solid separation, and the separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, difficult-to-convert components and other products;

[0015] (4) The separated catalyst to be regenerated enters the regenerator for carbonization reaction regeneration, and the regenerated catalyst is sent to the reducer;

[0016] (5) The regenerated catalyst contacts the reducing agent in the reducer to undergo a reduction reaction and release energy to obtain a reduced regenerated catalyst, a first portion of the reduced regenerated catalyst is returned to the first reactor for recycling, and a second portion of the reduced regenerated catalyst is returned to the third reactor for reaction;

[0017] Wherein, the first raw material is selected from one or more of paraffin-based crude oil, paraffin-intermediate-based crude oil and intermediate-paraffin-based crude oil;

[0018] The second raw material is produced by the device and / or other difficult-to-convert components, and the difficult-to-convert components are light hydrocarbons and / or light distillate oils with a final boiling point of less than 280-360°C. The light hydrocarbons are preferably C4 fractions, and the content of C4 olefins in the C4 fractions is greater than 50% by weight.

[0019] The method according to the first aspect, wherein the catalytic cracking reaction conditions in the first reactor are:

[0020] The reaction temperature is 550-650°C;

[0021] The reaction time is 0.1-5 seconds; and / or

[0022] The weight ratio of agent to oil is (5-30):1;

[0023] Preferably, the first raw material enters the first reactor after being preheated and steam atomized, the preheating temperature is 180-350° C., and the water-oil weight ratio is (0.05-0.5):1.

[0024] According to the method of the first aspect, the catalytic cracking reaction conditions in the second reactor are:

[0025] The reaction temperature is 450-600°C; and / or

[0026] Weight hourly space velocity is 1-20 hours -1 .

[0027] According to the method of the first aspect, the catalytic cracking reaction conditions in the third reactor are:

[0028] The reaction temperature is 600-720°C;

[0029] Response time is 0.1-3 seconds; and / or

[0030] The weight ratio of agent to oil is (5-50):1;

[0031] Preferably, the second raw material is introduced into the third reactor after being steam atomized, and the weight ratio of water to oil is (0.05-0.5):1.

[0032] The method according to the first aspect, wherein the weight ratio of the fresh catalyst injected into the third reactor to the reduced regenerated catalyst is 0.005-0.3:1.

[0033] The method according to the first aspect, wherein the third reactor is provided with a main reaction section and one or more second raw material feeding sections;

[0034] Preferably, the one or more second raw material feeding sections are each independently arranged in the middle and upstream of the third reactor; and / or

[0035] Preferably, the catalyst density in each of the second raw material feed sections is 120-290 kg / m 3 .

[0036] According to the method of the first aspect, wherein, in the catalyst reducer, the reduction temperature is 550-700° C. and / or the reduction time is 2-20 minutes.

[0037] The method according to the first aspect, wherein the catalyst comprises 0.01-5 wt%, preferably 0.005-3 wt%, of a metal oxide based on the dry weight of the catalyst, wherein the metal in the metal oxide is selected from one or more of the following: tin, cobalt, iron, molybdenum, manganese, copper, barium and chromium;

[0038] Preferably, the catalyst comprises:

[0039] 0-70 parts by weight, preferably 5-60 parts by weight, more preferably 10-50 parts by weight of clay,

[0040] 5-99 parts by weight, preferably 10-80 parts by weight, more preferably 20-70 parts by weight of a binder,

[0041] 1-60 parts by weight, preferably 5-45 parts by weight, more preferably 10-40 parts by weight of zeolite, and

[0042] 0.001-5 parts by weight, preferably 0.005-2 parts by weight of a metal oxide,

[0043] The total weight of the catalyst is 100 parts by weight;

[0044] Wherein, the binder is an inorganic oxide binder, preferably silicon dioxide and / or aluminum oxide;

[0045] The zeolite comprises a medium-pore zeolite and an optional large-pore zeolite, wherein the medium-pore zeolite is a ZSM series zeolite and / or a ZRP zeolite, and the large-pore zeolite is one or more selected from rare earth Y-type zeolite, rare earth hydrogen Y-type zeolite, ultrastable Y-type zeolite and high-silicon Y-type zeolite. Preferably, the medium-pore zeolite accounts for 5-100% by weight, preferably 50-90% by weight, and more preferably 20-50% by weight of the total weight of the zeolite;

[0046] The clay is preferably kaolin and / or halloysite.

[0047] A second aspect of the present invention provides a catalytic cracking system, comprising:

[0048] The catalytic cracking reaction unit comprises:

[0049] The first reactor is provided with a pre-lifting medium inlet, a first reduction regeneration catalyst inlet, a first raw material inlet, and a first oil agent outlet in order from bottom to top;

[0050] The second reactor is provided with a first oil-agent mixture inlet and a third oil-agent mixture inlet, and the first oil-agent outlet of the first reactor extends to the interior of the second reactor through the first oil-agent mixture inlet of the second reactor;

[0051] a third reactor, which is provided with a pre-lifting section, a feed section, a main reaction section and an outlet section in order from bottom to top, wherein a second reduction regeneration catalyst inlet, a fresh catalyst inlet and a pre-lifting medium inlet are provided at the bottom of the pre-lifting section, a difficult-to-convert raw material inlet, a circulating catalyst inlet and an optional catalyst outlet are provided at the feed section, and the outlet section of the third reactor extends to the interior of the second reactor through the third oil-agent mixture inlet of the second reactor; and

[0052] An oil agent separation device is provided with an oil agent inlet, a catalyst outlet and a reaction product outlet, wherein the oil agent inlet of the oil agent separation device is connected to the second reactor, so that the oil agent mixture from the second reactor is separated into reaction oil gas and catalyst to be generated by the oil agent separation device;

[0053] A settler, the settler is arranged in the second reactor, and is used for settling and collecting the spent catalyst separated by the oil agent separation device, a stripping section is arranged below the settler, and is used for stripping the spent catalyst, and the stripping section is provided with a spent catalyst outlet and a stripping medium inlet;

[0054] A reaction product separation unit, the reaction product separation unit is connected to the oil agent separation device and is used to separate the reaction oil gas separated by the oil agent separation device;

[0055] A regenerator, wherein the regenerator is provided with an inlet for a catalyst to be regenerated, an inlet for an oxygen-containing gas, a gas distributor, a cyclone separator, a regenerated flue gas pipeline and an outlet for a regenerated catalyst; the inlet for the catalyst to be regenerated of the regenerator is fluidically connected to the outlet for the catalyst to be regenerated of the stripping section; and

[0056] A catalyst reducer, wherein the catalyst reducer is provided with a reducing medium inlet, a regenerated catalyst inlet and at least one reduced regenerated catalyst outlet; the regenerated catalyst inlet of the catalyst reducer is connected with the regenerated catalyst outlet of the regenerator, so that the regenerated catalyst from the regenerator is reduced in the catalyst reducer; one reduced regenerated catalyst outlet of the catalyst reducer is fluidically connected with the first reduced regenerated catalyst inlet of the first reactor, so that a part of the reduced regenerated catalyst is circulated back to the first reactor; one reduced regenerated catalyst outlet of the catalyst reducer is fluidically connected with the second reduced regenerated catalyst inlet of the third reactor, so that a part of the reduced regenerated catalyst is circulated back to the third reactor.

[0057] According to the system of the second aspect, the feed section of the third reactor comprises a first feed section and a second feed section, and an external catalyst circulation pipeline connecting the first feed section and the second feed section is provided between the first feed section and the second feed section;

[0058] Preferably, the ratio of the diameters of the first feed section and the second feed section of the third reactor to the main reaction section is independently 1.2-1.5:1.

[0059] According to the system of the second aspect, the third reactor comprises two feed sections connected in sequence, the first feed section is connected to the pre-lifting section, the second feed section is connected to the main reaction section, and an external catalyst circulation pipeline connecting the two feed sections is provided between the first feed section and the second feed section;

[0060] Preferably, the distance between the connection port of the external catalyst circulation pipe on the first feed section and the bottom of the first feed section is 0 to 10% of the height of the second feed section; and / or the distance between the catalyst outlet on the second feed section and the bottom of the second feed section is 5% to 20% of the height of the second feed section.

[0061] Compared with the prior art, the method and system of the present invention have the following beneficial effects:

[0062] 1) It can realize direct catalytic cracking of crude oil, reduce the crude oil distillation process, simplify the process and reduce operating costs.

[0063] 2) In the process of catalytic cracking of crude oil, the single-pass conversion rate is not pursued. The light distillate oil that is difficult to convert is recycled. By setting up specific reaction zones, a higher overall conversion rate and higher target product selectivity can be achieved.

[0064] 3) According to the reaction performance of the difficult-to-convert component, it is introduced into the reactor in a specific feed section of the third reactor. The higher catalyst density and higher catalyst activity in the feed section are beneficial to improving the reaction conversion rate and catalytic reaction selectivity of the difficult-to-convert component.

[0065] 4) The catalyst in the second feed section can be selectively returned to the first feed section to improve the catalyst-oil ratio of the first feed section, and can also be selectively removed from the reactor according to the degree of carbonization of the catalyst, which helps to improve the catalyst activity in the reactor.

[0066] 5) The catalyst contains variable valence metals, which store and release energy through the gain and loss of electrons or the shift of common electron pairs between the metal and the metal oxide, provide heat for the reaction, and can solve or improve the problem of insufficient heat balance during the reaction process.

[0067] By adopting the catalytic cracking method of the present application, chemical raw materials such as ethylene and propylene can be efficiently produced directly from crude oil, which not only further shortens the crude oil processing process, helps refineries transform, develop and extend from oil refining to chemical raw material production, but also improves the economic benefits of refineries. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present application but do not constitute a limitation to the present application. In the accompanying drawings:

[0069] Figure 1 A schematic diagram of a process for producing chemical raw materials by direct catalytic cracking of crude oil according to an embodiment of the present application.

[0070] Description of reference numerals:

[0071] 100, first reactor; 101, first pre-lift medium pipeline; 102, first feed pipeline; 104, first reactor outlet; 200, settler; 201, stripping section; 202, stripping medium; 203, waiting inclined pipe; 204, oil agent separation device; 205, gas collecting chamber; 206, large oil and gas pipeline; 207, second reactor; 300, third reactor; 301, second pre-lift medium pipeline; 302, fresh catalyst pipeline; 303, second feed pipeline; 304, third feed pipeline; 305, fourth feed pipeline; 306, Catalyst circulation pipe; 307, catalyst outlet pipe; 308, third reactor outlet section; 309, third reactor pre-lifting section; 310, third reactor main reaction section; 311, third reactor first feed section; 312, third reactor second feed section; 400, regenerator; 401, oxygen-containing gas inlet; 402, main air distributor; 403, regenerated catalyst outlet; 404, cyclone separator; 405, regenerated flue gas pipeline; 500, reducer; 501, reducing medium inlet; 502, second regeneration inclined tube; 503, first regeneration inclined tube. DETAILED DESCRIPTION

[0072] The present application is further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present application will become clearer and more specific.

[0073] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0074] Any specific numerical value (including the endpoint of the numerical range) disclosed in this application is not limited to the exact value of the numerical value, but should be understood to also cover values ​​close to the exact value, such as all possible values ​​within the range of ±5% of the exact value. In addition, for the disclosed numerical range, the endpoint values ​​of the range, the endpoint values ​​and the specific point values ​​in the range, and the specific point values ​​can be arbitrarily combined to obtain one or more new numerical ranges, and these new numerical ranges should also be regarded as specifically disclosed herein.

[0075] In the present application, the terms "upstream" and "downstream" are based on the flow direction of the reactants. For example, when the reactants flow from bottom to top, "upstream" means the position below, while "downstream" means the position above.

[0076] In this article, low-carbon olefins are a general term for ethylene, propylene and butene, and light aromatics (BTX) are a general term for benzene (BTX), toluene (T) and xylene (X).

[0077] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0078] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0079] The present invention provides a method for direct catalytic cracking of crude oil with improved heat balance, comprising:

[0080] (1) A first raw material and a first reduced regenerated catalyst from a catalyst reducer enter a first reactor and a second reactor in sequence to undergo a catalytic cracking reaction;

[0081] (2) The second reduced regenerated catalyst and the fresh catalyst from the catalyst reducer are respectively injected into the pre-lifting section at the bottom of the third reactor, and move upward from the bottom under the action of the pre-lifting medium. The second raw material enters the third reactor through the feeding section of the third reactor, mixes with the existing flow in the reactor and undergoes a cracking reaction. The reaction oil mixture enters the second reactor to continue the cracking reaction;

[0082] (3) The reaction product and the catalyst to be produced obtained in the second reactor enter the oil separation device for gas-solid separation, and the separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, difficult-to-convert components and other products;

[0083] (4) The separated catalyst to be regenerated enters the regenerator for carbonization reaction regeneration, and the regenerated catalyst is sent to the reducer;

[0084] (5) The regenerated catalyst contacts the reducing agent in the reducer to undergo a reduction reaction and release energy to obtain a reduced regenerated catalyst, a first portion of the reduced regenerated catalyst is returned to the first reactor for recycling, and a second portion of the reduced regenerated catalyst is returned to the third reactor for reaction;

[0085] Wherein, the first raw material is selected from one or more of paraffin-based crude oil, paraffin-intermediate-based crude oil and intermediate-paraffin-based crude oil;

[0086] The second raw material is produced by the device and / or other difficult-to-convert components, and the difficult-to-convert components are light hydrocarbons and / or light distillate oils with a final boiling point of less than 280-360°C. The light hydrocarbons are preferably C4 fractions, and the content of C4 olefins in the C4 fractions is greater than 50% by weight.

[0087] The present application will be further described below with reference to the preferred implementation modes shown in the accompanying drawings, but the present application is not limited thereby.

[0088] Figure 1A preferred embodiment of the catalytic cracking method of the present application is provided, wherein the catalytic cracking reactor comprises a first reactor 100, a second reactor 207 and a third reactor 300. The third reactor 300 is provided with a pre-lifting section 309, a first feed section 311, a second feed section 312, a main reaction section 310 and an outlet section 308.

[0089] The pre-lifting medium enters the bottom of the first reactor 100 through the first pre-lifting medium pipeline 101. The lifting medium can be dry gas, water vapor or a mixture thereof. The reduced regenerated catalyst from the first regeneration inclined tube 503 enters the bottom of the first reactor 100, moves upward and mixes under the lifting effect of the pre-lifting medium. The reaction raw materials such as preheated crude oil and atomized steam are injected into the bottom of the first reactor 100 through the first feed pipeline 102, mixed and contacted with the existing oil gas and catalyst in the catalytic cracking reactor, and catalytic cracking reaction is carried out in the process of passing through the first reactor 100 from bottom to top. The reaction oil gas and catalyst flow upward through the first reactor outlet 104 into the second reactor 207, and continue to carry out catalytic cracking reaction. The catalyst with coke generated by the reaction and the reaction oil and gas enter the oil agent separation device 204 such as a cyclone separator for gas-solid separation. The separated reaction oil and gas are led out of the device through the gas collecting chamber 205 and the large oil and gas pipe 206 and enter the subsequent separation system; the separated catalyst with coke to be regenerated enters the lower part of the settler 200 and enters the regenerator 400 through the inclined pipe 203 to be regenerated.

[0090] The pre-lifting medium enters the bottom of the third reactor 300 through the second pre-lifting medium pipeline 301. The lifting medium can be dry gas, water vapor or a mixture thereof. The reduced regenerated catalyst from the first regeneration inclined tube 503 enters the bottom of the third reactor 300, mixes with the fresh catalyst from the fresh catalyst pipeline 302 and moves upward.

[0091] Part of the difficult-to-convert raw materials and atomized steam are injected into the lower part of the first feed section 311 of the third reactor through the second feed pipeline 303, mixed and contacted with the existing catalyst in the catalytic cracking reactor, and the oil-agent mixture moves upward and is mixed with part of the difficult-to-convert components injected through the third feed pipeline 304 and enters the bottom of the second feed section 312. Optionally, part of the difficult-to-convert raw materials enters the upper part of the second feed section through pipeline 305, and the oil-agent mixture enters the main reaction section 310, where the cracking reaction fully occurs, and the reaction products enter the second reactor 207 through the outlet section.

[0092] The catalyst-to-oil ratio and activity of the catalyst in the first feed section 311 and the second feed section 312 can be adjusted according to the reaction requirements by adjusting the flow rates of the external catalyst circulation pipeline 306 and the catalyst outlet pipeline 307 .

[0093] The catalyst with carbon coke enters the regenerator 400, contacts with the oxygen-containing gas injected through the oxygen-containing gas inlet 401 and the main air distributor 402, undergoes a complete combustion reaction, and completely releases heat. The regenerated catalyst is sent to the reducer through the regenerated catalyst outlet 403.

[0094] The regenerated catalyst contacts the reducing medium injected from the bottom of the reducer 500 through the reducing medium inlet 501 in the reducer, and the metal oxide in the catalyst is activated. A part of the reduced regenerated catalyst is circulated to the first reactor through the first regeneration inclined tube 503, and a part of the regenerated catalyst is supplied to the third reactor through the second regeneration inclined tube 502. The regenerated flue gas is separated from the entrained catalyst by the cyclone separator 404 and then enters the energy recovery system through the regeneration flue gas pipeline 405.

[0095] The crude oil applicable to the catalytic cracking method provided in the present application is selected from paraffin-based crude oil, paraffin-intermediate-based crude oil and intermediate-paraffin-based crude oil. The first key component of the paraffin-based crude oil and any component in the second key group belong to paraffin-based properties; the first key component of the paraffin-intermediate-based crude oil is paraffin-based and the second key group is intermediate-based; the first key component of the intermediate-paraffin-based crude oil is intermediate-based and the second key group is paraffin-based.

[0096] In one embodiment, the crude oil has a characteristic factor K value of not less than 12.0 and a relative density of 780-900 kg / m 3 .

[0097] In the present application, the difficult-to-convert component is a light hydrocarbon such as a C4 fraction or a light distillate oil with a final boiling point of less than 280-360°C, or a mixture thereof.

[0098] In one embodiment, the C4 fraction refers to low molecular hydrocarbons that exist in gaseous form at room temperature and pressure with C4 fraction as the main component, including alkanes, olefins and alkynes with 4 carbon atoms in the molecule. It includes gaseous hydrocarbon products rich in C4 fraction produced by the device of the present invention, and may also include gaseous hydrocarbons rich in C4 fraction produced by other device processes, among which the C4 fraction produced by the device of the present invention is preferred. The C4 hydrocarbons are preferably C4 fractions rich in olefins, wherein the content of C4 olefins is greater than 50% by weight, preferably greater than 60% by weight, and preferably above 70% by weight.

[0099] In one embodiment, the light distillate oil with a final boiling point of less than 280-360°C includes light distillate oils of various distillation ranges with a final boiling point of less than 280-360°C produced by the device of the present invention, such as light gasoline, light diesel, etc. It can also include a mixture of one or more of primary processed straight-run naphtha, straight-run kerosene, and straight-run diesel; a mixed oil of one or more of secondary processed topped oil, raffinate oil, hydrocracking light naphtha, pentane oil, coker gasoline, Fischer-Tropsch synthetic oil, catalytic cracking light gasoline, hydrogenated gasoline, and hydrogenated diesel.

[0100] In one embodiment, the catalytic cracking reaction conditions in the first reactor are:

[0101] The reaction temperature is 550-650°C;

[0102] The reaction time is 0.1-5 seconds; and / or

[0103] The weight ratio of agent to oil is (5-30):1;

[0104] Preferably, the first raw material enters the first reactor after being preheated and steam atomized, the preheating temperature is 180-360° C., and the water-oil weight ratio is (0.05-0.5):1.

[0105] In the present application, the catalytic cracking reaction temperature of the first reactor refers to the reactor outlet temperature.

[0106] In one embodiment, the catalytic cracking reaction conditions in the second reactor are:

[0107] The reaction temperature is 450-600°C;

[0108] Weight hourly space velocity is 1-20 hours -1 ; and / or

[0109] In the present application, the catalytic cracking reaction temperature of the second reactor refers to the bed temperature of the second reactor.

[0110] In one embodiment, the catalytic cracking reaction conditions in the third reactor are:

[0111] The reaction temperature is 600-720°C;

[0112] Response time is 0.1-3 seconds; and / or

[0113] The weight ratio of agent to oil is (5-50):1;

[0114] Preferably, the second raw material is introduced into the third reactor after being steam atomized, and the weight ratio of water to oil is (0.05-0.5):1.

[0115] In the present application, the catalytic cracking reaction temperature of the third reactor refers to the reactor outlet temperature.

[0116] In one embodiment, the weight ratio of the fresh catalyst injected into the third reactor to the reduced regenerated catalyst is 0.005-0.3:1.

[0117] In one embodiment, the third reactor is provided with a main reaction section and one or more second raw material feeding sections;

[0118] Preferably, the one or more second raw material feeding sections are each independently arranged in the middle and upstream of the third reactor; and / or

[0119] Preferably, the catalyst density in each of the second raw material feed sections is 120-290 kg / m 3 .

[0120] In one embodiment, one or more of the difficult-to-convert components may be fed into at least one or more identical positions in the feed section of the third reactor, or may be fed into different positions.

[0121] In one embodiment, in the catalyst reducer, the reduction temperature is 550-700° C. and / or the reduction time is 2-20 minutes.

[0122] In one embodiment, the temperature in the regenerator is 550-750°C, more preferably 600-730°C, and further preferably 650-700°C; the gas superficial linear velocity is 0.3-3 m / s, preferably 0.5-2.5 m / s, and more preferably 0.6-1.5 m / s; the average residence time of the catalyst to be regenerated is 0.6-8 minutes, preferably 0.8-6 minutes, and more preferably 1-5 minutes.

[0123] In one embodiment, the catalyst comprises 0.01-5wt%, preferably 0.005-2wt% of a metal oxide, based on the dry weight of the catalyst, wherein the metal in the metal oxide is selected from one or more of the following: tin, cobalt, iron, molybdenum, manganese, copper, barium and chromium;

[0124] Preferably, the catalyst comprises:

[0125] 0-70 parts by weight, preferably 5-60 parts by weight, more preferably 10-50 parts by weight of clay,

[0126] 5-99 parts by weight, preferably 10-80 parts by weight, more preferably 20-70 parts by weight of a binder,

[0127] 1-60 parts by weight, preferably 5-45 parts by weight, more preferably 10-40 parts by weight of zeolite, and

[0128] 0.001-5 parts by weight, preferably 0.005-2 parts by weight of a metal oxide,

[0129] The total weight of the catalyst is 100 parts by weight;

[0130] Wherein, the binder is an inorganic oxide binder, preferably silicon dioxide and / or aluminum oxide;

[0131] The zeolite comprises a medium-pore zeolite and an optional large-pore zeolite, wherein the medium-pore zeolite is a ZSM series zeolite and / or a ZRP zeolite, and the large-pore zeolite is one or more selected from rare earth Y-type zeolite, rare earth hydrogen Y-type zeolite, ultrastable Y-type zeolite and high-silicon Y-type zeolite. Preferably, the medium-pore zeolite accounts for 5-100% by weight, preferably 50-90% by weight, and more preferably 20-50% by weight of the total weight of the zeolite;

[0132] The clay is preferably kaolin and / or halloysite.

[0133] In the catalyst used in the present invention, clay is used as a catalyst matrix (ie, a carrier) and an inorganic oxide is used as a binder.

[0134] In the present application, medium-pore zeolite and large-pore zeolite follow the conventional definition in the art, that is, the average pore diameter of medium-pore zeolite is about 0.5-0.6 nm, and the average pore diameter of large-pore zeolite is about 0.7-1.0 nm.

[0135] As an example, the large-pore zeolite can be selected from one or more of rare earth Y (REY) type zeolite, rare earth hydrogen Y (REHY) type zeolite, ultrastable Y type zeolite obtained by different methods and high silicon Y type zeolite. The medium-pore zeolite can be selected from zeolites with MFI structure, such as ZSM series zeolites and / or ZRP zeolites. Optionally, the above-mentioned medium-pore zeolites can also be modified with non-metallic elements such as phosphorus and / or transition metal elements such as iron, cobalt, and nickel. A more detailed description of ZRP zeolite can be found in U.S. Patent No. 5,232,675A. ZSM series zeolites are preferably selected from one or more mixtures of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48 and other zeolites of similar structure. A more detailed description of ZSM-5 can be found in U.S. Patent No. 3,702,886A.

[0136] The catalyst of the present invention contains variable valence metals, which store and release energy through the gain and loss of electrons or the offset of common electron pairs between the metal and the metal oxide, and provide heat for the catalytic cracking reaction of the difficult-to-convert components, thereby solving the problem of high heat demand for the reaction of the difficult-to-convert components.

[0137] The present invention arranges a catalyst reducer in the reaction system, and the catalyst portion regenerated by the regenerator enters the reducer and is mixed with a fresh catalyst. Under the action of a reducing medium (such as refinery dry gas and / or small molecule alkanes), the variable valence metal oxide in the mixed catalyst is reduced and releases energy, and the reduced and regenerated catalyst carries the energy into the second reactor to participate in the reaction, thereby providing heat for the catalytic cracking reaction of the difficult-to-convert components in the second reactor, thereby solving the problem of high heat demand for the reaction of the difficult-to-convert components in the second reactor.

[0138] In the method provided by the present invention, the catalyst preparation method adopts the preparation method of conventional catalytic cracking catalyst, which is a preparation method well known to those skilled in the art. The metal can be loaded on the catalyst by impregnation method or slurry method, preferably impregnation method, which are well known to those skilled in the art.

[0139] According to the present application, the separation of the reaction product and the catalyst to be produced is well known to those skilled in the art, for example, it can be carried out using a cyclone separator in a settler, and the method of further separating the reaction oil and gas to obtain dry gas, liquefied gas, light distillate oil in difficult-to-convert components, and cracked heavy oil is also well known to those skilled in the art. The dry gas and liquefied gas can be further separated by conventional separation means in the art to obtain target products such as ethylene and propylene and a C4 fraction.

[0140] The present invention also provides a catalytic cracking system, comprising:

[0141] The catalytic cracking reaction unit comprises:

[0142] The first reactor is provided with a pre-lifting medium inlet, a first reduction regeneration catalyst inlet, a first raw material inlet, and a first oil agent outlet in order from bottom to top;

[0143] The second reactor is provided with a first oil-agent mixture inlet and a third oil-agent mixture inlet, and the first oil-agent outlet of the first reactor extends to the interior of the second reactor through the first oil-agent mixture inlet of the second reactor;

[0144] a third reactor, which is provided with a pre-lifting section, a feed section, a main reaction section and an outlet section in order from bottom to top, wherein a second reduction regeneration catalyst inlet, a fresh catalyst inlet and a pre-lifting medium inlet are provided at the bottom of the pre-lifting section, a difficult-to-convert raw material inlet, a circulating catalyst inlet and an optional catalyst outlet are provided at the feed section, and the outlet section of the third reactor extends to the interior of the second reactor through the third oil-agent mixture inlet of the second reactor; and

[0145] An oil agent separation device is provided with an oil agent inlet, a catalyst outlet and a reaction product outlet, wherein the oil agent inlet of the oil agent separation device is connected to the second reactor, so that the oil agent mixture from the second reactor is separated into reaction oil gas and catalyst to be generated by the oil agent separation device;

[0146] A settler, the settler is arranged in the second reactor, and is used for settling and collecting the spent catalyst separated by the oil agent separation device, a stripping section is arranged below the settler, and is used for stripping the spent catalyst, and the stripping section is provided with a spent catalyst outlet and a stripping medium inlet;

[0147] A reaction product separation unit, the reaction product separation unit is connected to the oil agent separation device and is used to separate the reaction oil gas separated by the oil agent separation device;

[0148] A regenerator, wherein the regenerator is provided with an inlet for a catalyst to be regenerated, an inlet for an oxygen-containing gas, a gas distributor, a cyclone separator, a regenerated flue gas pipeline and an outlet for a regenerated catalyst; the inlet for the catalyst to be regenerated of the regenerator is fluidically connected to the outlet for the catalyst to be regenerated of the stripping section; and

[0149] A catalyst reducer, wherein the catalyst reducer is provided with a reducing medium inlet, a regenerated catalyst inlet and at least one reduced regenerated catalyst outlet; the regenerated catalyst inlet of the catalyst reducer is connected with the regenerated catalyst outlet of the regenerator, so that the regenerated catalyst from the regenerator is reduced in the catalyst reducer; one reduced regenerated catalyst outlet of the catalyst reducer is fluidically connected with the first reduced regenerated catalyst inlet of the first reactor, so that a part of the reduced regenerated catalyst is circulated back to the first reactor; one reduced regenerated catalyst outlet of the catalyst reducer is fluidically connected with the second reduced regenerated catalyst inlet of the third reactor, so that a part of the reduced regenerated catalyst is circulated back to the third reactor.

[0150] In one embodiment, the feed section of the third reactor includes a first feed section and a second feed section, and an external catalyst circulation pipeline connecting the first feed section and the second feed section is arranged between the first feed section and the second feed section;

[0151] Preferably, the ratio of the diameters of the first feed section and the second feed section of the third reactor to the main reaction section is independently 1.2-1.5:1.

[0152] In one embodiment, the third reactor comprises two feed sections connected in sequence, the first feed section is connected to the pre-lifting section, the second feed section is connected to the main reaction section, and an external catalyst circulation pipeline connecting the two feed sections is provided between the first feed section and the second feed section;

[0153] Preferably, the distance between the connection port of the external catalyst circulation pipe on the first feed section and the bottom of the first feed section is 0 to 10% of the height of the second feed section; and / or the distance between the catalyst outlet on the second feed section and the bottom of the second feed section is 5% to 20% of the height of the second feed section.

[0154] The height of the second feeding section is H1 as shown in the figure.

[0155] In the present application, a catalyst distribution plate can be arranged at the position where the catalyst enters the bottom of the regenerator, for example, at the outlet end of the auxiliary regenerator. According to the present application, the catalyst distribution plate can be a distribution plate of various types commonly used in the industry, for example, one or more of a flat plate, an arch, a dish, an annular shape and an umbrella shape. The use of a catalyst distribution plate helps to make the catalyst uniformly contact with the oxygen-rich gas in the axial direction of the regenerator for a charring reaction, improve the charring efficiency, and reduce the occurrence of local hot spots in the catalyst bed.

[0156] According to the present application, the oil agent separation equipment and the reaction product separation equipment are both well known to those skilled in the art. For example, the oil agent separation equipment may include a cyclone separator, a settler and a stripper, etc., and the reaction product separation equipment may be a distillation tower, etc.

[0157] Example

[0158] The following examples will further illustrate the present application, but are not intended to limit the present application.

[0159] The raw oil used in the following examples and comparative examples is Subei crude oil from Jiangsu Oilfield, and its properties are shown in Table 1. The comparative catalyst used is a commercial catalytic cracking catalyst purchased from the Catalyst Branch of Sinopec, and the trade name is DMMC-1. The catalyst used in the examples is a DMMC-1 catalyst containing CuO, and the amount of CuO used is 1.0 weight % based on the total weight of the catalyst.

[0160] Example 1

[0161] Using the feedstock oil shown in Table 1 and the DMMC-1 catalyst containing CuO, Figure 1 The experiment was carried out on the pilot plant shown in the figure, wherein the structure of the reactor used is as follows:

[0162] The total height of the conventional riser reactor (first reactor) connected in series with the fluidized bed reactor (second reactor) is 7 meters. The third reactor is 5 meters high and has an inner diameter of 0.2 meters. Two feed sections are arranged at the bottom. Each feed section is 0.2 meters high and has an inner diameter of 0.3 meters. One feed inlet is arranged in the first feed section, and two feed inlets are arranged in the second feed section.

[0163] The reduced hot regenerated catalyst in the first regeneration inclined tube 503 enters the lower part of the first reactor, contacts the existing oil-agent mixture in the reactor and moves upward. The preheated crude oil and atomized steam are injected into the first reactor through the first feed pipeline 102, and the water-oil weight ratio is 0.2:1, and the catalyst is mixed and contacted with the existing catalyst in the catalytic cracking reactor. The catalytic cracking reaction is carried out in the process of passing through the first reactor and the second reactor from bottom to top. The obtained catalyst with coke and the reaction oil and gas enter the oil-agent separation device 204 such as a cyclone separator for gas-solid separation. The reaction oil and gas obtained by separation are led out of the device through the gas collecting chamber 205 and the large oil and gas pipe 206, and enter the subsequent separation system; the separated catalyst with coke enters the lower part of the settler 200, and enters the regenerator 400 through the waiting inclined tube 203.

[0164] The hot regenerated catalyst of the second regeneration inclined tube 502 and the fresh catalyst of the first feed pipeline 102 enter the third reactor III, and move upward under the lifting effect of the pre-lifting medium injected through the first pre-lifting medium pipeline 101. The C4 fraction and light fraction oil from the separation system enter the lower part of the first feed section through the second feed pipeline 303, contact with the mixed catalyst at a water-oil weight ratio of 0.2:1 and move upward, and fully react in the main reaction section. The reaction products and catalyst enter the second reactor through the outlet section.

[0165] The catalyst with coke enters the regenerator and undergoes a complete combustion reaction when in contact with air. The regenerated catalyst enters the reducer and undergoes a reduction activation reaction when in contact with dry gas. The reduced regenerated catalyst is divided into two parts. One part of the catalyst returns to the first reactor via the first regeneration inclined tube 503 for recycling, and another part of the regenerated catalyst returns to the third reactor via the second regeneration inclined tube 502 for recycling. The regenerated flue gas enters the energy recovery system via the regeneration flue gas pipeline 405.

[0166] The operating conditions and product distribution are listed in Table 2 and Table 3. As can be seen from Table 2, the ethylene yield of this embodiment reaches 7.55% by weight, the propylene yield reaches 24.52% by weight, and the total yield of ethylene, propylene and light aromatics reaches 42.44%.

[0167] Example 2

[0168] Using the feedstock oil shown in Table 1 and the DMMC-2 catalyst containing CuO, Figure 1 The experiment was carried out on the pilot plant shown in the figure, in which the structure of the reactor used was the same as that in Example 1.

[0169] The reduced hot regenerated catalyst in the first regeneration inclined tube 503 enters the lower part of the first reactor, contacts the existing oil-agent mixture in the reactor and moves upward. The preheated crude oil and atomized steam are injected into the first reactor through the first feed pipeline 102, with a water-oil weight ratio of 0.2:1, and are mixed and contacted with the existing catalyst in the catalytic cracking reactor. The catalytic cracking reaction is carried out in the process of passing through the first reactor and the second reactor from bottom to top. The obtained catalyst with coke and the reaction oil and gas enter the oil-agent separation device 204 such as a cyclone separator for gas-solid separation. The reaction oil and gas obtained by separation are led out of the device through the gas collecting chamber 205 and the large oil and gas pipe 206, and enter the subsequent separation system; the separated catalyst with coke enters the lower part of the settler 200, and enters the regenerator 400 through the waiting inclined tube 203.

[0170] The hot regenerated catalyst of the second regeneration inclined tube 502 and the fresh catalyst of the first feed pipeline 102 enter the third reactor III, and move upward under the lifting effect of the pre-lifting medium injected through the first pre-lifting medium pipeline 101. The C4 fraction from the separation system enters the lower part of the first feed section through the second feed pipeline 303, and the light distillate oil enters the lower part of the second feed section through the third feed pipeline 304. The water-oil weight ratio is 0.2:1, contacts with the mixed catalyst and moves upward, and fully reacts in the main reaction section. The reaction product and the catalyst enter the second reactor through the outlet section.

[0171] The catalyst with coke enters the regenerator and undergoes a complete combustion reaction when in contact with air. The regenerated catalyst enters the reducer and undergoes a reduction activation reaction when in contact with dry gas. The reduced regenerated catalyst is divided into two parts. One part of the catalyst returns to the first reactor via the first regeneration inclined tube 503 for recycling, and another part of the regenerated catalyst returns to the third reactor via the second regeneration inclined tube 502 for recycling. The regenerated flue gas enters the energy recovery system via the regeneration flue gas pipeline 405.

[0172] The operating conditions and product distribution are listed in Table 2 and Table 3. As can be seen from Table 2, the ethylene yield of this embodiment reaches 8.77% by weight, the propylene yield reaches 26.51% by weight, and the total yield of ethylene, propylene and light aromatics reaches 44.84%.

[0173] Comparative Example 1

[0174] The crude oil and DMMC-1 catalyst shown in Table 1 were used to conduct the test on a medium-sized device. The reactors were a conventional riser reactor (first reactor) connected in series with a fluidized bed reactor (second reactor), and a third reactor connected to the second reactor. The preheated crude oil entered the riser reaction zone and the fluidized bed reactor in turn to contact with the catalytic cracking catalyst for catalytic cracking reaction. After the reaction, the logistics entered the subsequent oil agent separation device and product separation equipment. The separated C4 fraction and light gasoline returned to the bottom of the third reactor to contact with the regenerated catalyst for reaction. The oil agent mixture generated by the reaction entered the second reactor; the separated catalyst to be regenerated entered the lower part of the regenerator and contacted with the air distributed into the regenerator through the main air distributor to cause a scorching reaction. The fuel oil was injected into the catalyst dense phase bed layer. The fuel oil was scorched after contacting the high-temperature air and released heat; the regenerated catalyst returned to the reactor for recycling. The operating conditions and product distribution are listed in Tables 2 and 3.

[0175] It can be seen from the results in Table 2 that the ethylene yield of this comparative example is only 5.72% by weight, the propylene yield is only 21.22% by weight, and the total yield of ethylene, propylene and light aromatics is 37.29%.

[0176] It can be seen from the results of the above examples and comparative examples that when the catalytic cracking method and system of the present application are used for catalytic cracking of crude oil, the utilization rate of crude oil atoms is high, and the yield of chemical raw materials such as ethylene and propylene is significantly improved. The temperature field distribution in the reactor is significantly improved, which alleviates the thermal balance problem to a certain extent.

[0177] The preferred embodiments of the present application are described in detail above; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0178] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0179] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the content invented by the present application.

[0180] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect" and "connect" should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0181] The present application has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, various replacements and improvements may be made to the present application, all of which fall within the scope of protection of the present application.

[0182] Table 1 Properties of crude oil used

[0183]

[0184] Table 2 Comparison of reaction conditions between the embodiments and comparative examples

[0185]

[0186]

[0187] Table 3 Comparison of reaction results between examples and comparative examples

[0188] Comparative Example 1 Example 1 Example 2 Product distribution, weight % gas 51.32 50.97 56.74 Ethylene 5.72 7.55 8.77 Of which propylene 21.22 24.52 26.51 gasoline 23.34 23.59 21.56 Coke 8.08 8.28 8.70 total 100.00 100.00 100.00 Ethylene+propylene+BTX 37.29 42.44 44.84 Low carbon olefins + light aromatics 51.84 49.39 52.74

Claims

1. A method for direct catalytic cracking of crude oil with improved thermal balance, comprising: (1) A first raw material and a first reduced regenerated catalyst from a catalyst reducer enter a first reactor and a second reactor in sequence to undergo a catalytic cracking reaction; (2) The second reduced regenerated catalyst and the fresh catalyst from the catalyst reducer are respectively injected into the pre-lifting section at the bottom of the third reactor, and move upward from the bottom under the action of the pre-lifting medium. The second raw material enters the third reactor through the feeding section of the third reactor, mixes with the existing flow in the reactor and undergoes a cracking reaction. The reaction oil mixture enters the second reactor to continue the cracking reaction; (3) The reaction product and the catalyst to be produced obtained in the second reactor enter the oil separation device for gas-solid separation, and the separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, difficult-to-convert components and other products; (4) The separated catalyst to be regenerated enters the regenerator for carbonization reaction regeneration, and the regenerated catalyst is sent to the reducer; (5) The regenerated catalyst contacts the reducing agent in the reducer to undergo a reduction reaction and release energy to obtain a reduced regenerated catalyst, a first portion of the reduced regenerated catalyst is returned to the first reactor for recycling, and a second portion of the reduced regenerated catalyst is returned to the third reactor for reaction; Wherein, the first raw material is selected from one or more of paraffin-based crude oil, paraffin-intermediate-based crude oil and intermediate-paraffin-based crude oil; The second raw material is produced by the device and / or other difficult-to-convert components, and the difficult-to-convert components are light hydrocarbons and / or light distillate oils with a final boiling point of less than 280-360°C. The light hydrocarbons are preferably C4 fractions, and the content of C4 olefins in the C4 fractions is greater than 50% by weight.

2. The method according to claim 1, characterized in that The catalytic cracking reaction conditions in the first reactor are: The reaction temperature is 550-650°C; The reaction time is 0.1-5 seconds; and / or The weight ratio of agent to oil is (5-30):1; Preferably, the first raw material enters the first reactor after being preheated and steam atomized, the preheating temperature is 180-350° C., and the water-oil weight ratio is (0.05-0.5):

1.

3. The method according to claim 1, characterized in that The catalytic cracking reaction conditions in the second reactor are: The reaction temperature is 450-600°C; and / or Weight hourly space velocity is 1-20 hours -1 .

4. The method according to claim 1, characterized in that: The catalytic cracking reaction conditions in the third reactor are: The reaction temperature is 600-720°C; Response time is 0.1-3 seconds; and / or The weight ratio of agent to oil is (5-50):1; Preferably, the second raw material is introduced into the third reactor after being steam atomized, and the weight ratio of water to oil is (0.05-0.5):

1.

5. The method according to claim 1, characterized in that The weight ratio of the fresh catalyst injected into the third reactor to the reduced regenerated catalyst is 0.005-0.3:

1.

6. The method according to claim 1, characterized in that The third reactor is provided with a main reaction section and one or more second raw material feeding sections; Preferably, the one or more second raw material feeding sections are independently arranged in the middle and upstream of the third reactor; and / or Preferably, the catalyst density in each of the second raw material feed sections is 120-290 kg / m 3 .

7. The method according to claim 1, characterized in that In the catalyst reducer, the reduction temperature is 550-700° C. and / or the reduction time is 2-20 minutes.

8. The method according to claim 1, characterized in that Based on the dry weight of the catalyst, the catalyst comprises 0.01-5 wt%, preferably 0.005-3 wt% of a metal oxide, wherein the metal in the metal oxide is selected from one or more of the following: tin, cobalt, iron, molybdenum, manganese, copper, barium and chromium; Preferably, the catalyst comprises: 0-70 parts by weight, preferably 5-60 parts by weight, more preferably 10-50 parts by weight of clay, 5-99 parts by weight, preferably 10-80 parts by weight, more preferably 20-70 parts by weight of a binder, 1-60 parts by weight, preferably 5-45 parts by weight, more preferably 10-40 parts by weight of zeolite, and 0.001-5 parts by weight, preferably 0.005-2 parts by weight of a metal oxide, The total weight of the catalyst is 100 parts by weight; Wherein, the binder is an inorganic oxide binder, preferably silicon dioxide and / or aluminum oxide; The zeolite comprises a medium-pore zeolite and an optional large-pore zeolite, wherein the medium-pore zeolite is a ZSM series zeolite and / or a ZRP zeolite, and the large-pore zeolite is one or more selected from rare earth Y-type zeolite, rare earth hydrogen Y-type zeolite, ultrastable Y-type zeolite and high-silicon Y-type zeolite. Preferably, the medium-pore zeolite accounts for 5-100% by weight, preferably 50-90% by weight, and more preferably 20-50% by weight of the total weight of the zeolite; The clay is preferably kaolin and / or halloysite.

9. A catalytic cracking system comprising: The catalytic cracking reaction unit comprises: The first reactor is provided with a pre-lifting medium inlet, a first reduction regeneration catalyst inlet, a first raw material inlet, and a first oil agent outlet in order from bottom to top; The second reactor is provided with a first oil-agent mixture inlet and a third oil-agent mixture inlet, and the first oil-agent outlet of the first reactor extends to the interior of the second reactor through the first oil-agent mixture inlet of the second reactor; a third reactor, which is provided with a pre-lifting section, a feed section, a main reaction section and an outlet section in order from bottom to top, wherein a second reduction regeneration catalyst inlet, a fresh catalyst inlet and a pre-lifting medium inlet are provided at the bottom of the pre-lifting section, a difficult-to-convert raw material inlet, a circulating catalyst inlet and an optional catalyst outlet are provided at the feed section, and the outlet section of the third reactor extends to the interior of the second reactor through the third oil-agent mixture inlet of the second reactor; and An oil agent separation device is provided with an oil agent inlet, a catalyst outlet and a reaction product outlet, wherein the oil agent inlet of the oil agent separation device is connected to the second reactor, so that the oil agent mixture from the second reactor is separated into reaction oil gas and catalyst to be generated by the oil agent separation device; A settler, the settler is arranged in the second reactor, and is used for settling and collecting the spent catalyst separated by the oil agent separation device, a stripping section is arranged below the settler, and is used for stripping the spent catalyst, and the stripping section is provided with a spent catalyst outlet and a stripping medium inlet; A reaction product separation unit, the reaction product separation unit is connected to the oil agent separation device and is used to separate the reaction oil gas separated by the oil agent separation device; A regenerator, wherein the regenerator is provided with an inlet for a catalyst to be regenerated, an inlet for an oxygen-containing gas, a gas distributor, a cyclone separator, a regenerated flue gas pipeline and an outlet for a regenerated catalyst; the inlet for the catalyst to be regenerated of the regenerator is fluidically connected to the outlet for the catalyst to be regenerated of the stripping section; and A catalyst reducer, wherein the catalyst reducer is provided with a reducing medium inlet, a regenerated catalyst inlet and at least one reduced regenerated catalyst outlet; the regenerated catalyst inlet of the catalyst reducer is connected with the regenerated catalyst outlet of the regenerator, so that the regenerated catalyst from the regenerator is reduced in the catalyst reducer; one reduced regenerated catalyst outlet of the catalyst reducer is fluidically connected with the first reduced regenerated catalyst inlet of the first reactor, so that a part of the reduced regenerated catalyst is circulated back to the first reactor; one reduced regenerated catalyst outlet of the catalyst reducer is fluidically connected with the second reduced regenerated catalyst inlet of the third reactor, so that a part of the reduced regenerated catalyst is circulated back to the third reactor.

10. The catalytic cracking system according to claim 9, characterized in that: The feed section of the third reactor includes a first feed section and a second feed section, and an external catalyst circulation pipeline connecting the first feed section and the second feed section is arranged between the first feed section and the second feed section; Preferably, the ratio of the diameters of the first feed section and the second feed section of the third reactor to the main reaction section is independently 1.2-1.5:

1.

11. The catalytic cracking system according to claim 9, characterized in that: The third reactor comprises two feed sections connected in sequence, the first feed section is connected to the pre-lifting section, the second feed section is connected to the main reaction section, and an external catalyst circulation pipeline connecting the two feed sections is arranged between the first feed section and the second feed section; Preferably, the distance between the connection port of the external catalyst circulation pipe on the first feed section and the bottom of the first feed section is 0 to 10% of the height of the second feed section; and / or the distance between the catalyst outlet on the second feed section and the bottom of the second feed section is 5% to 20% of the height of the second feed section.

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