Method and system for preparing low-carbon olefin by utilizing microwave cracking and catalytic cracking and application

Abstract

The invention relates to the technical field of crude oil cracking, and discloses a method and a system for preparing low-carbon olefin by utilizing microwave cracking and catalytic cracking and application, the method comprises the following steps: fractionating raw oil to obtain a gas phase fraction and a liquid phase fraction; under the condition of microwave cracking, mixing the gas-phase fraction with first water vapor, and then carrying out first contact with an electromagnetic wave absorber; carrying out second contact on the liquid-phase fraction and a catalyst under a catalytic cracking condition; and separating the first contact product and / or the second contact product to obtain the low-carbon olefin. According to the method, microwave cracking is adopted and is matched with fractionation and catalytic cracking, so that the problem that a heavy cracking raw material is easy to coke during cracking reaction can be effectively solved, the yield of low-carbon olefin is increased, and the operation period is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of crude oil cracking, and in particular to a method and system for preparing light olefins by utilizing microwave cracking and catalytic cracking, and applications thereof. Background Art

[0002] Crude oil contains saturated components and heavy components (such as aromatic components, colloids and asphaltene, etc.). The heavy components in crude oil entering the cracking furnace will aggravate the coking of the heavy components during the cracking process and affect the yield of olefins.

[0003] CN1041967A discloses a method for decomposing and treating low-grade raw materials. The method comprises the following steps: when thermally decomposing and treating low-grade raw materials containing heavy fractions in a decomposition furnace, the low-grade raw materials are extracted from the preheater of the decomposition furnace, the heavy fractions are separated and removed from the low-grade raw materials by a gas-liquid separation method, and then the low-grade raw materials are returned to the preheater for thermal decomposition reaction. Before the raw materials are cracked, the flash evaporation method is used to treat the crude oil for gas-liquid separation, and the gas phase enters the radiation section for cracking. However, after the raw materials are flashed, at least 5% of the hydrocarbon raw materials remain in the liquid, which affects the yield of light olefins. Moreover, the separated liquid phase is directly used as fuel oil, resulting in a waste of raw materials. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of easy coking and low yield of light olefins in the crude oil cracking process in the prior art, and to provide a method and system for preparing light olefins by microwave cracking and catalytic cracking and their application.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for preparing light olefins by using microwave cracking and catalytic cracking, the method comprising: fractionating crude oil to obtain a gas phase fraction and a liquid phase fraction; under microwave cracking conditions, the gas phase fraction is mixed with a first water vapor and then brought into first contact with an electromagnetic wave absorber; under catalytic cracking conditions, the liquid phase fraction is brought into second contact with a catalyst; and then the first contact product and / or the second contact product are separated to obtain light olefins.

[0006] The second aspect of the present invention provides a system for preparing light olefins by using microwave cracking and catalytic cracking, the system comprising: a fractionation unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit; wherein:

[0007] The fractionation unit is used to fractionate the crude oil to obtain a gas phase fraction and a liquid phase fraction;

[0008] The microwave cracking unit is used to bring the gas phase fraction and the first water vapor into first contact with the electromagnetic wave absorber under microwave cracking conditions;

[0009] The catalytic cracking unit is used to bring the liquid fraction into second contact with the catalyst under catalytic cracking conditions;

[0010] The cracking gas separation unit is used to separate the first contact product and / or the second contact product to obtain light olefins.

[0011] The third aspect of the present invention provides the use of the above-mentioned system in the preparation of light olefins, especially in the preparation of light olefins by direct cracking of crude oil.

[0012] A fourth aspect of the present invention provides the above-described method and / or application of the above-described system in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

[0013] The present invention has achieved the following beneficial effects:

[0014] (1) The present invention adopts microwave cracking, and cooperates with fractionation and catalytic cracking, which can effectively solve the problem of easy coking during the cracking reaction of heavy cracking raw materials, while improving the yield of light olefins and extending the operation cycle.

[0015] (2) The heat source of the present invention can be electrically heated, and the microwave reactor uses electrical energy, which can effectively save energy and reduce carbon emissions.

[0016] (3) Compared with conventional thermal cracking, the microwave cracking of the present invention can improve the selectivity of light olefins and reduce the cracking temperature; at the same time, it can also reduce carbon emissions and energy consumption. In a preferred case, the preferred microwave absorbing material (such as silicon carbide) of the present invention can further reduce the cracking temperature, while promoting the rapid cracking of light components, so that more light components are converted into light olefins.

[0017] (4) In a preferred embodiment, the present invention can further improve the yield of light olefins by obtaining a vapor phase fraction by microwave cracking using a specific fractionation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an implementation of a system for preparing light olefins provided by the present invention.

[0019] Description of Reference Numerals

[0020] 1- fractionation unit, 2- microwave cracking unit, 3- fluidized bed reactor, 4- catalyst regenerator, 5- catalytic cracking unit. DETAILED DESCRIPTION

[0021] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0022] In the present invention, unless otherwise specified, "crude oil" refers to unrefined petroleum. API value (also called API gravity) can usually be used to characterize the relative density of petroleum (crude oil) and petroleum products (such as refined petroleum, etc.). As the API value increases, the relative density of crude oil decreases.

[0023] In the present invention, unless otherwise specified, "low-carbon olefins" refer to olefins with carbon atoms of 4 or less, including ethylene, propylene, butene and butadiene.

[0024] The first aspect of the present invention provides a method for preparing light olefins by using microwave cracking and catalytic cracking, the method comprising: fractionating crude oil to obtain a gas phase fraction and a liquid phase fraction; under microwave cracking conditions, the gas phase fraction is mixed with a first water vapor and then brought into first contact with an electromagnetic wave absorber; under catalytic cracking conditions, the liquid phase fraction is brought into second contact with a catalyst; and then the first contact product and / or the second contact product are separated to obtain light olefins.

[0025] According to the present invention, preferably, the feedstock oil is crude oil; more preferably, the API of the feedstock oil is greater than 23 (for example, 23, 25, 29, 30, 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 300, 400, and a range formed by any two of the above points), preferably 25-45, and more preferably 25-42.

[0026] According to the present invention, preferably, the feedstock oil includes at least one of light naphtha, naphtha, diesel, hydrogenated tail oil, light crude oil, crude oil with a final distillation point higher than 600°C and lower than 700°C, and dehydrated crude oil. More preferably, the feedstock oil includes diesel, hydrogenated tail oil, light crude oil, dehydrated crude oil with a final distillation point higher than 600°C and lower than 700°C.

[0027] According to the present invention, the conditions for the fractionation can be carried out in a wide range, but in order to improve the yield of microwave cracking, preferably, the conditions for the fractionation are such that the boiling point of the gas phase fraction is less than 500° C. (for example, the boiling point is less than 490° C., 450° C., 430° C., 420° C., 410° C., 400° C., 380° C., 350° C., 300° C., 200° C., 100° C., 50° C.); further preferably, the boiling point of the gas phase fraction is less than 450° C. It can be understood that the gas phase fraction is a mixture, and the boiling point of the gas phase fraction is the final boiling point of the gas phase fraction.

[0028] In the present invention, the remaining portion after the crude oil is fractionated into the gas phase fraction is the liquid phase fraction. Usually, the gas phase fraction mainly includes light components in the crude oil, while the liquid phase fraction mainly includes heavy components (such as colloids and asphaltenes) in the crude oil.

[0029] According to the present invention, preferably, the fractionation temperature is 150-500° C. In the present invention, unless otherwise specified, the fractionation temperature refers to the temperature corresponding to when the crude oil is heated and a gas phase fraction is generated. In the present invention, there is no particular limitation on the fractionation device, and a conventional fractionation device, such as a fractionation tower, can be used.

[0030] According to the present invention, preferably, the conditions of the fractionation include: fractionation is carried out in a fractionation tower, the top temperature of the fractionation tower is 380-500°C (for example, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, and the range composed of any two of the above points), the bottom temperature is 150-280°C (for example, 150°C, 170°C, 180°C, 190°C, 200°C, 240°C, 280°C, and the range composed of any two of the above points), and the operating pressure is 0.1-0.5MPa (0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, and the range composed of any two of the above points). More preferably, the top temperature of the fractionation tower is 450-500°C, the bottom temperature is 180-240°C, and the operating pressure is 0.2-0.3MPa. In the present invention, unless otherwise specified, pressure is gauge pressure. A gas phase fraction is obtained at the top of the fractionation tower, and a liquid phase fraction is obtained at the bottom of the tower.

[0031] According to the present invention, in order to make the fractionation process easier and improve the yield of light olefins by microwave cracking, preferably, the method also includes: before fractionation, mixing the second water vapor with the preheated feedstock oil and heating it to 320-550°C (for example, 320°C, 330°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 550°C, and a range consisting of any two of the above points).

[0032] According to the present invention, preferably, the weight ratio of the second steam to the preheated feedstock oil is 0.4-1.5:1 (for example, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.5:1, and a range consisting of any two of the above). The weight ratio of the second steam to the preheated feedstock oil is limited within the above range to further improve the yield of light olefins.

[0033] According to the present invention, preferably, the temperature of the preheated feedstock oil is 150-200°C (for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, and a range consisting of any two of the above points).

[0034] According to the present invention, preferably, the temperature of the second water vapor is 180-240° C. (for example, 180° C., 190° C., 200° C., 220° C., 240° C., and a range consisting of any two of the above points).

[0035] In the present invention, unless otherwise specified, the external heating heat source in each step adopts electric energy. The use of green electricity can achieve zero carbon emission of the production device.

[0036] According to the present invention, preferably, the conditions for microwave pyrolysis include: the temperature of the first contact is 350-750°C (for example, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, and a range consisting of any two of the above, more preferably 600-750°C); the residence time is 0.05-1s (for example, 0.05s, 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 10s, and a range consisting of any two of the above); The weight ratio of the first water vapor to the gas phase fraction is 0.2-2.2:1, more preferably 0.5-1.6:1; the power of the microwave is 6-10000KW (for example, 6KW, 100KW, 1000KW, 2000KW, 3000KW, 4000KW, 5000KW, 6000KW, 7000KW, 8000KW, 9000KW, 10000KW, and the range composed of any two points above), more preferably 300-9000KW. In the present invention, in order to achieve the above power, different magnetrons can be combined. The greater the microwave power, the more magnetrons need to be combined. Microwave power refers to the total microwave power provided by the microwave cracking device to the reactor.

[0037] In the present invention, unless otherwise specified, the temperature of the first contacting refers to the temperature at the outlet of the reactor.

[0038] According to the present invention, preferably, the frequency of the microwaves used in the microwave lysis is 100-3500 MHz (e.g., 100 MHz, 500 MHz, 1000 MHz, 1500 MHz, 2000 MHz, 2500 MHz, 3000 MHz, and a range consisting of any two of the above), more preferably 1000-2500 MHz.

[0039] According to the present invention, preferably, the temperature of the first water vapor is 100-650° C. (for example, 100° C., 150° C., 180° C., 200° C., 220° C., 250° C., 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., and a range consisting of any two of the above), preferably 180-520° C. In the present invention, unless otherwise specified, when the temperature of the water vapor is higher than 100° C., the water vapor is high-pressure water vapor, that is, the temperature of the water vapor is the saturation temperature of water vapor under high pressure.

[0040] In a preferred embodiment, the present invention can obtain a gas phase fraction with a boiling point of <500°C by sending the preheated crude oil and the second water vapor into a fractionation device, and by adjusting the preheating temperature and the ratio of the crude oil to the second water vapor, the desired higher boiling point fraction (almost excluding colloid and asphalt phase) enters the gas phase fraction, and then is sent to a microwave reactor for cracking reaction. In this way, when the crude oil cracking performance meets the requirements, the proportion of crude oil entering the microwave reactor can be increased, thereby obtaining more light olefins and improving the overall benefits.

[0041] According to the present invention, preferably, the dielectric constant of the electromagnetic wave absorber is 1-20 Farads / meter, more preferably 5-15 Farads / meter. More preferably, the electromagnetic wave absorber is selected from at least one of silicon carbide, composite ferrite, ultrafine metal particles and organic polymer (functional polymer) nanomaterials.

[0042] In the present invention, unless otherwise specified, the dielectric constant refers to the relative dielectric constant. The relative dielectric constant of silicon carbide used in the present invention is usually 9-11 Farad / m.

[0043] According to the present invention, preferably, the average particle size of the absorbing material is 2-20 mm, more preferably 5-14 mm, and further preferably 5-10 mm.

[0044] The present invention can further process the heavy components in the crude oil through catalytic cracking, so as to make full use of the heavy components and improve the yield of light olefins.

[0045] According to the present invention, preferably, the conditions for catalytic cracking include: the temperature of catalytic cracking is 500-650°C; the catalyst is a solid acid selective molecular sieve catalyst, more preferably, the catalyst includes at least one of MMC-1 catalyst, MMC-2 catalyst, CHP-1 catalyst, CHP-2 catalyst, CRP-1 catalyst, CHP-S catalyst, CIP-1 catalyst, CIP-2 catalyst, CIP-3 catalyst, CIP-4 catalyst, CIP-5 catalyst and CIP-S catalyst. The different types of catalysts listed above are all industrialized catalysts and can be obtained commercially. The catalyst-oil ratio can be 0.5-20:1 (for example, 0.5:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, 20:1, and the range of any two of the above points), preferably 0.8-15:1.

[0046] According to the present invention, preferably, catalytic cracking is carried out in a fluidized reactor, wherein the fluidized reactor comprises a riser and a bed reactor, more preferably comprises a first riser, a second riser, a bed reactor and a stripper. The fluidized reactor in the present invention can refer to the reactor disclosed in CN201684585U.

[0047] In the present invention, preferably, the bed reactor, the first riser and the second riser are all filled with catalyst.

[0048] According to the present invention, preferably, the outlet temperature of the first riser is 520-580°C (for example, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, and a range formed by any two of the above points), preferably 525-570°C.

[0049] According to the present invention, preferably, the outlet temperature of the second riser is 600-650°C (for example, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, and a range formed by any two of the above points), preferably 605-645°C.

[0050] According to the present invention, preferably, the product of the first riser, the product of the second riser and the steam generated by the stripper enter the bed reactor together; preferably, the space velocity of the bed reactor is 2h -1 -10h -1 .

[0051] According to the present invention, the first contact product and the second contact product can be mixed for separation, or can be separated separately. Preferably, the process of separating the first contact product and / or the second contact product includes: sequentially entering the contact product into a quencher and a cracking gas separation system to obtain products such as hydrogen, methane, ethylene, propylene, butadiene, gasoline, fuel oil and diesel. The cracking separation system can be a separation process commonly used in the art, such as a sequential separation process of LUMMUS.

[0052] According to the present invention, in order to further improve the yield of light olefins, preferably, the contact product is first heat exchanged, and then enters the quencher (heat exchanger) and the cracking gas separation system in sequence. The contact product is first heat exchanged to reduce the coking phenomenon of the cracking gas during cooling and separation.

[0053] The second aspect of the present invention provides a system for preparing light olefins by using microwave cracking and catalytic cracking, the system comprising: a fractionation unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit; wherein:

[0054] The fractionation unit is used to fractionate the crude oil to obtain a gas phase fraction and a liquid phase fraction;

[0055] The microwave cracking unit is used to bring the gas phase fraction and the first water vapor into first contact with the electromagnetic wave absorber under microwave cracking conditions;

[0056] The catalytic cracking unit is used to bring the liquid fraction into second contact with the catalyst under catalytic cracking conditions;

[0057] The cracking gas separation unit is used to separate the first contact product and / or the second contact product to obtain light olefins.

[0058] According to the present invention, preferably, the microwave cracking unit comprises a tubular reactor and a microwave generator fixed outside the tubular reactor, wherein the tubular reactor can be arranged along the fluid direction.

[0059] According to the present invention, the fractionation unit may be a distillation device or a fractionation device commonly used in the art. Preferably, the fractionation unit is a fractionation tower.

[0060] According to the present invention, preferably, the catalytic cracking unit comprises a fluidized reactor, wherein the fluidized reactor comprises a riser and a bed reactor, preferably comprises a first riser, a second riser, a bed reactor and a stripper.

[0061] According to the present invention, preferably, the catalytic cracking unit further comprises a catalyst regenerator, and the catalyst regenerator is used to regenerate the catalyst.

[0062] The third aspect of the present invention provides the use of the above-mentioned system in the preparation of light olefins, especially in the preparation of light olefins by direct cracking of crude oil.

[0063] A fourth aspect of the present invention provides the above-described method and / or application of the above-described system in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

[0064] According to a particularly preferred embodiment of the present invention, a method for preparing light olefins by microwave cracking and catalytic cracking comprises:

[0065] (1) The dehydrated and desalted crude oil (API of the crude oil is 30-35) is electrically heated to 180°C to obtain preheated crude oil, and water vapor is sent into a preheater to be preheated to 200°C. The preheated crude oil is mixed with a second water vapor and heated to 320-350°C. The weight ratio of the second water vapor to the crude oil is 0.5-0.7:1.

[0066] (2) The heated crude oil and water vapor mixture is then sent to a fractionation device (fractionation tower), where the crude oil forms a gas phase fraction and a liquid phase fraction, wherein the gas phase fraction is a fraction with a boiling point of <415°C, and the liquid phase fraction is a fraction with a boiling point of >415°C; the top temperature of the fractionation tower is 400-420°C, the bottom temperature is 180-200°C, the operating pressure is 0.2-0.3MPa; and the crude oil vaporization rate is 65-75%.

[0067] (3) The gas phase fraction and the first water vapor are sent to a microwave cracking unit for microwave cracking to obtain microwave cracking gas. The microwave cracking unit includes a tubular reactor and a microwave generator. The tubular reactor is filled with an electromagnetic wave absorber, and the gas phase fraction is cracked in the presence of the electromagnetic wave absorber. The electromagnetic wave absorber is silicon carbide, the temperature of the microwave cracking reaction is 720-750°C, the residence time is 0.5-0.6s, the weight ratio of the first water vapor to the gas phase fraction is 1-1.5:1, the microwave power is 5000-5500KW; the temperature of the first water vapor is 200-240°C.

[0068] (4) The liquid phase is sent to a catalytic cracking unit for steam catalytic cracking to obtain catalytic cracking gas. The catalyst used in the catalytic cracking unit is a solid acid molecular sieve catalyst CHP-1 catalyst, and the catalyst-to-oil ratio is 11-13. The catalytic cracking unit includes a first riser, a second riser, a steam stripper and a bed reactor. The liquid phase is divided into two parts and enters the first riser and the second riser respectively. The steam stripper produces water vapor, and the products of the first riser and the second riser enter the bed reactor together with the water vapor. Among them, the outlet temperature of the first riser is 560-568°C, the outlet temperature of the second riser is 606-620°C, and the air velocity of the bed reactor is 5-6.2h-1 .

[0069] (5) After the microwave cracking gas is mixed with the catalytic cracking gas, it passes through a quencher and a cracking gas separation system to separate hydrogen, light olefins, cracking gasoline, cracking diesel and cracking fuel oil.

[0070] The present invention will be described in detail below by way of examples. In the following examples,

[0071] The average particle size of silicon carbide is 9 mm.

[0072] The cracking furnace described in the comparative example of the present invention is a CBL-III cracking furnace (purchased from Sinopec Group Corporation).

[0073] The composition of the crude oil (API of the crude oil is 33.5) used in the following examples and comparative examples is shown in Table 1, and the composition is measured according to the ASTM D5307 method.

[0074] Table 1

[0075]

[0076]

[0077] Example 1

[0078] use Figure 1 The system shown is used to crack crude oil to produce light olefins.

[0079] (1) The dehydrated and desalted crude oil is electrically heated to 180°C to obtain preheated crude oil, and water vapor is simultaneously sent into a preheater to be preheated to 200°C. The preheated crude oil is mixed with a second water vapor and heated to 320°C. The weight ratio of the second water vapor to the crude oil is 0.5:1.

[0080] (2) The heated crude oil and water vapor mixture is then sent to a fractionation device (fractionation tower), where the crude oil forms a gas phase fraction and a liquid phase fraction, wherein the gas phase fraction is a fraction with a boiling point <415°C, and the liquid phase fraction is a fraction with a boiling point >415°C; the top temperature of the fractionation tower is 400°C, the bottom temperature is 180°C, the operating pressure is 0.2MPa, and the crude oil vaporization rate is 70%.

[0081] (3) The gas phase fraction and the first water vapor are sent to a microwave cracking unit for microwave cracking to obtain microwave cracking gas. The microwave cracking unit includes a tubular reactor and a microwave generator. The tubular reactor is filled with an electromagnetic wave absorber, and the gas phase fraction is cracked in the presence of the electromagnetic wave absorber. The electromagnetic wave absorber is silicon carbide, the temperature of the microwave cracking reaction is 750°C, the residence time is 0.6s, the weight ratio of the first water vapor to the gas phase fraction is 1:1, the microwave power is 5500KW, and the microwave frequency is 2500MHz; the temperature of the first water vapor is 200°C.

[0082] (4) The liquid phase is sent to the catalytic cracking unit for steam catalytic cracking to obtain catalytic cracking gas. The catalyst used in the catalytic cracking unit is a solid acid molecular sieve catalyst CHP-1 catalyst with a catalyst-to-oil ratio of 11.8. The catalytic cracking unit includes a first riser, a second riser, a steam stripper and a bed reactor. The liquid phase is divided into two parts and enters the first riser and the second riser respectively. The steam stripper produces water vapor, and the products of the first riser and the second riser enter the bed reactor together with the water vapor. Among them, the outlet temperature of the first riser is 568°C, the outlet temperature of the second riser is 606°C, and the air velocity of the bed reactor is 6.2h -1 .

[0083] (5) After the microwave cracking gas is mixed with the catalytic cracking gas, it passes through a quencher and a cracking gas separation system (using the LUMMUS sequential separation process) to separate hydrogen, light olefins, cracking gasoline, cracking diesel and cracking fuel oil.

[0084] Among them, the yield of ethylene was 26.47 wt%, the yield of propylene was 15.14 wt%, the yield of 1,3-butadiene was 4.56 wt%, and the total yield of the above trienes was 46.27 wt%.

[0085] The operation cycle of the microwave cracking unit (tubular reactor) is 50 days.

[0086] Comparative Example 1

[0087] In this comparative example 1, only a conventional cracking furnace was used for cracking.

[0088] The dehydrated and desalted crude oil is directly sent to the cracking furnace, and after passing through the convection section, it directly enters the radiation section. The operating parameters of the radiation section are the furnace tube outlet temperature of 760℃, the residence time of 0.1s, and the water-oil ratio of 1:1; cracking is carried out. The cracking gas adopts the LUMMUS sequential separation process.

[0089] Analysis of the steam cracking reaction products revealed that the yield of ethylene was 21.49 wt%, the yield of propylene was 13.29 wt%, the yield of 1,3-butadiene was 4.03 wt%, and the yield of triene was 38.81 wt%.

[0090] The operating cycle is 5 days.

[0091] It can be seen from the results of the embodiments and comparative examples that, with the conventional cracking device, the crude oil can only be put into use for a 5-day operation cycle, while the present invention can ensure that the crude oil can be normally put into use in the cracking device, and can effectively reduce the occurrence of coking, with an operation cycle of 50 days; and improve the yield of light olefins.

[0092] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing light olefins by microwave cracking and catalytic cracking, characterized in that: The method comprises: fractionating crude oil to obtain a gas phase fraction and a liquid phase fraction; under microwave cracking conditions, mixing the gas phase fraction with a first water vapor and then bringing the mixture into first contact with an electromagnetic wave absorber; under catalytic cracking conditions, bringing the liquid phase fraction into second contact with a catalyst; and then separating the first contact product and / or the second contact product to obtain light olefins.

2. The method according to claim 1, wherein: The feedstock oil is crude oil; and / or, the API of the feedstock oil is greater than 23, preferably 25-45, more preferably 25-42; Preferably, the feedstock oil includes at least one of light naphtha, naphtha, diesel, hydrogenated tail oil, light crude oil, crude oil with a final distillation point higher than 600° C. and lower than 700° C., and dehydrated and desalted crude oil.

3. The method according to claim 1, wherein: The distillation conditions are such that the boiling point of the gas phase fraction is less than 500°C; Preferably, the fractionation temperature is 150-500°C; More preferably, the conditions for the fractionation include: performing fractionation in a fractionation tower, the top temperature of the fractionation tower is 380-500° C., the bottom temperature of the tower is 150-280° C., and the operating pressure is 0.1-0.5 MPa.

4. The method according to claim 1, wherein: The method further comprises: before fractionation, mixing the second steam with the preheated feedstock oil and heating the mixture to 320-550° C.; Preferably, the weight ratio of the second steam to the preheated crude oil is 0.4-1.5:

1.

5. The method according to claim 1, wherein: The conditions for microwave cracking include: the temperature of the first contact is 350-750°C; the residence time is 0.05-1s, preferably 0.1-0.7s; the weight ratio of the first water vapor to the gas phase fraction is 0.2-2.2:1, preferably 0.5-1.6:1; the power of the microwave is 6-10000KW, preferably 300-9000KW.

6. The method according to claim 1, wherein: The temperature of the first water vapor is 100-650°C, preferably 180-520°C; And / or, the electromagnetic wave absorber is selected from at least one of silicon carbide, composite ferrite, ultrafine metal particles, and organic high molecular polymer nanomaterials.

7. The method according to claim 1, wherein: The conditions for catalytic cracking include: the temperature of catalytic cracking is 500-650° C.; the catalyst is a solid acid selective molecular sieve catalyst; the catalyst-oil ratio is 0.5-20:1, preferably 0.8-15:

1.

8. The method according to claim 1, wherein: The catalytic cracking is carried out in a fluidized reactor, wherein the fluidized reactor comprises a riser and a bed reactor, preferably comprises a first riser, a second riser, a bed reactor and a stripper.

9. The method according to claim 8, wherein: The outlet temperature of the first riser is 520-580°C, preferably 525-570°C; and / or, the outlet temperature of the second riser is 600-650° C., preferably 605-645° C.; And / or, the product of the first riser, the product of the second riser and the steam generated by the stripper enter the bed reactor together; preferably, the space velocity of the bed reactor is 2h -1 -10h -1 .

10. A system for preparing light olefins by using microwave cracking and catalytic cracking, characterized in that: The system includes: a fractionation unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit; wherein, The fractionation unit is used to fractionate the crude oil to obtain a gas phase fraction and a liquid phase fraction; The microwave cracking unit is used to bring the gas phase fraction and the first water vapor into first contact with the electromagnetic wave absorber under microwave cracking conditions; The catalytic cracking unit is used to bring the liquid fraction into second contact with the catalyst under catalytic cracking conditions; The cracking gas separation unit is used to separate the first contact product and / or the second contact product to obtain light olefins.

11. Use of the system according to claim 10 in the preparation of light olefins, especially in the preparation of light olefins by direct cracking of crude oil.

12. Use of the method according to any one of claims 1 to 9, and / or the system according to claim 10, in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

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