A method and system for producing light olefins through catalytic cracking

Abstract

The present invention relates to a method and system for producing light olefins by catalytic cracking, the method comprising: (1) contacting a feedstock oil with a first catalyst in a down-flow reactor to carry out a first catalytic cracking reaction to obtain a first oil-agent mixture; (2) contacting the first reaction oil gas with a second catalyst in an up-flow reactor to carry out a second catalytic cracking reaction to obtain a second oil-agent mixture; (3) separating the second oil-agent mixture to obtain a second reaction oil gas and a second catalyst to be regenerated, and separating the second reaction oil gas to obtain light olefins. In the method and system for producing light olefins by catalytic cracking of the present invention, the feedstock oil and the first catalyst first enter the down-flow reactor to carry out a first catalytic cracking reaction, and then a second catalytic cracking reaction at a higher temperature is carried out in the up-flow reactor. In particular, the outlet temperature of the up-flow reactor is controlled to be 10-100°C higher than the outlet temperature of the down-flow reactor, thereby significantly improving the yield and selectivity of light olefins.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum refining and petrochemical processing, and in particular to a method and system for producing light olefins through catalytic cracking. Background Art

[0002] As an important secondary crude oil processing technology, catalytic cracking technology holds an irreplaceable position in the production of clean oil products and light olefins, characterized by its wide feedstock adaptability, high heavy oil conversion rate, and flexible product solutions. Recent development and trends in catalytic cracking technology for chemical feedstock production indicate that major oil companies and research institutions have shifted their focus from increasing light olefin yields to improving light olefin selectivity. In this process, researchers are developing new processes based on optimally matching hydrocarbon cracking performance with reaction temperature, reaction time, and catalyst performance.

[0003] The catalytic cracking unit is a self-heating device, where heat is transferred between the reaction and regeneration systems via the supported catalyst. This makes the regulation of reaction temperature inseparable from the circulation of the catalyst. In addition to providing the heat required for the catalytic cracking reaction, the catalyst also plays a crucial role in providing active centers for the reaction. As the cracking reaction occurs, the heat capacity of the catalyst particles decreases in tandem with the active centers. However, as the cracking reaction progresses, further cracking of small hydrocarbon molecules requires higher reaction temperatures. Researchers have also investigated how to best match reaction temperature and catalyst activity to the cracking properties of hydrocarbon molecules.

[0004] CN107557063 discloses a method for catalytic conversion of low-quality crude oil. This method utilizes a two-stage riser reactor. A portion of the spent catalyst is removed through a central expansion section, while a portion of the regenerated catalyst is added. This method allows for segmented control of the reaction depth and optimizes catalyst activity. However, this method uses a method that reduces the linear velocity and extends the reaction time in the expansion section to remove the catalyst. This increases the residence time of the oil and gas in the expansion section, significantly increases side reactions, and reduces the selectivity of the target product.

[0005] CN105368493 discloses a catalytic conversion method for producing high-octane gasoline. This method involves initially cracking the crude oil with a cooled regeneration agent at a relatively low temperature for a relatively short time. Subsequently, a higher temperature regeneration agent is added, and the cracking reaction is continued at a temperature 5-100°C higher than that in the initial reaction zone for a longer reaction time. This method controls the cracking depth by separately controlling the reaction severity in each riser reactor reaction zone. However, in this method, the carbonized catalyst after reaction in the initial reaction zone is completely transferred to the main reaction zone, which increases the proportion of hydrocarbons reacting on the deactivated catalyst and reduces the selectivity of the target product.

[0006] CN107337574 discloses a catalytic conversion method for producing olefins by cracking light hydrocarbons. This method uses spent catalyst drawn from a stripper or reacted catalyst drawn from a reactor to return to a pre-contact zone. After the light hydrocarbon feedstock is vaporized in the pre-contact zone, it enters the main reaction zone where it contacts the regenerated catalyst for high-temperature cracking. This method combines low-temperature pre-gasification with high-temperature cracking, optimizing the reactor's temperature distribution. However, due to the low reaction temperature in the pre-contact zone, this method not only vaporizes the light hydrocarbons but also hinders cracking reactions. This significantly reduces the catalyst-to-oil ratio in the main reaction zone, resulting in a low yield of low-carbon olefins from the cracking of the light hydrocarbons.

[0007] CN110240932 discloses a multi-stage fluidized catalytic reaction method and reactor for petroleum hydrocarbons. This method involves contacting and reacting feedstock oil and regenerated catalyst in a first reaction zone. After some of the catalyst is swirled out, the oil and gas continue through a delivery pipe to a second reaction zone where they react with a second catalyst replenished in a third reaction zone. The oil and gas in the first reaction zone continue to undergo cracking reactions under the new catalyst. Light hydrocarbons and light cycle oil react with the second catalyst in the third reaction zone, and the resulting oil enters the second reaction zone where it continues to undergo catalytic cracking. This method enables catalyst replacement, gradient control of the reaction temperature, and control of the carbon content of the regenerated catalyst. However, because the third reaction zone is located below the second reaction zone, the oil and gas in the first reaction zone can undergo severe thermal cracking reactions as they pass through the high-temperature third reaction zone, resulting in the production of large amounts of dry gas.

[0008] CN108753356 discloses a multi-stage countercurrent catalytic cracking / cracking system and method. This method utilizes at least two descending fluidized bed reactors and at least two gas-solid rapid separation devices arranged in a stepped configuration. The discharge port of each descending fluidized bed reactor is connected to the gas-solid mixed phase inlet of the corresponding gas-solid rapid separation device, and the gas outlet of the corresponding gas-solid rapid separation device of each descending fluidized bed reactor is connected to the feed port of the corresponding descending fluidized bed reactor of the previous stage. This method can provide different temperature fields and catalyst activity fields for each stage of the reaction, which is beneficial for improving the selectivity of hydrocarbon catalytic cracking / cracking. However, this method cannot flexibly control the temperature and catalyst activity according to the hydrocarbon cracking performance, which has significant operational limitations.

[0009] In the process of catalytic cracking of hydrocarbons to produce light olefins, how to match the cracking properties of hydrocarbon molecules and flexibly regulate the reaction temperature and catalyst activity to improve the yield and selectivity of light olefins is a technical problem that needs to be solved urgently. Summary of the Invention

[0010] The object of the present invention is to provide a method and system for producing light olefins by catalytic cracking, wherein the catalytic cracking is carried out in a descending reactor and an ascending reactor in sequence and the temperature difference between the two reactors is controlled simultaneously to improve the yield and selectivity of light olefins.

[0011] In a first aspect, the present invention relates to a method for producing light olefins by catalytic cracking, the method comprising: (1) contacting a feedstock oil with a first catalyst in a down-flow reactor to carry out a first catalytic cracking reaction to obtain a first oil-agent mixture, wherein the first oil-agent mixture comprises a first reaction oil gas and a first catalyst to be regenerated; (2) contacting the first reaction oil gas with a second catalyst in an up-flow reactor to carry out a second catalytic cracking reaction to obtain a second oil-agent mixture; (3) separating the second oil-agent mixture to obtain a second reaction oil gas and a second catalyst to be regenerated, and separating the second reaction oil gas to obtain light olefins; wherein the outlet temperature of the up-flow reactor is 10-100°C higher than the outlet temperature of the down-flow reactor.

[0012] Optionally, the downward reactor and the upward reactor are directly connected through an oil agent delivery pipe, and the first oil agent mixture containing the first reaction oil gas is directly delivered to the upward reactor through the oil agent delivery pipe, so that the first reaction oil gas contacts the second catalyst in the upward reactor to carry out the second catalytic cracking reaction.

[0013] Optionally, the method further comprises: stripping and regenerating the second spent catalyst; and the first catalyst and the second catalyst are each independently selected from a regenerated catalyst and / or a cooled regenerated catalyst.

[0014] Optionally, a gas-solid quick separation device is provided between the downward reactor and the upward reactor, and the first oil agent mixture is separated into the first reaction oil gas and the first catalyst to be generated through the gas-solid quick separation device; the first reaction oil gas is transported to the upward reactor so that the first reaction oil gas contacts the second catalyst in the upward reactor to carry out the second catalytic cracking reaction.

[0015] Optionally, the method further includes: stripping and regenerating the first spent catalyst separated by the gas-solid quick separation equipment; stripping and regenerating the second spent catalyst; the second catalyst is a regenerated catalyst and / or a cooled regenerated catalyst.

[0016] Optionally, the first catalyst is selected from a combination of one or more of a regenerated catalyst, a cooled regenerated catalyst and the second catalyst to be regenerated; preferably, the first catalyst is a combination of the regenerated catalyst and the second catalyst to be regenerated; further preferably, the first catalyst is the second catalyst to be regenerated.

[0017] Optionally, the residence time of the first oil-agent mixture in the gas-solid quick separation device is less than 0.05 s; preferably, the residence time of the first oil-agent mixture in the gas-solid quick separation device is less than 0.03 s.

[0018] Optionally, in step (1), the outlet temperature of the down-type reactor is 500-650°C, the oil and gas residence time is 0.1-2s; the weight ratio of the first catalyst to the feedstock oil is (1-50):1; preferably, the outlet temperature of the down-type reactor is 530-600°C, the oil and gas residence time is 0.5-1.0s; the weight ratio of the first catalyst to the feedstock oil is (10-30):1.

[0019] Optionally, in step (2), the outlet temperature of the upward reactor is 550-700° C., the oil and gas residence time is 0.5-10 s; the weight ratio of the second catalyst to the feedstock oil is (5-50):1;

[0020] Preferably, the outlet temperature of the upward reactor is 560-650° C., the oil and gas residence time is 1-5 s; and the weight ratio of the second catalyst to the feedstock oil is (10-30):1.

[0021] Optionally, the feedstock oil is selected from a combination of one or more of crude oil, atmospheric wax oil, vacuum wax oil, atmospheric residue oil, vacuum residue oil, deasphalted oil, hydrogenated heavy oil and coker wax oil; or is selected from a combination of partial fractions or full fractions of one or more of coal liquefaction oil, oil sands oil, shale oil, synthetic oil, animal and plant oils and fats.

[0022] In a second aspect, the present invention relates to a system for producing light olefins by catalytic cracking, the system comprising a downward reactor and an upward reactor; the oil agent outlet of the downward reactor is fluidically connected to the oil agent inlet of the upward reactor; the top of the downward reactor is respectively provided with a raw oil feed nozzle and a first catalyst delivery pipe; the bottom of the upward reactor is provided with a second catalyst delivery pipe, and the top of the upward reactor is provided with an oil agent output pipe; the top of the upward reactor is provided with an oil agent separation device, the oil agent inlet of the oil agent separation device is connected to the oil agent output pipe, and the oil agent separation device is provided with an oil and gas output pipe and a second catalyst output pipe to be generated; the oil and gas output pipe is connected to the oil and gas separation device; the downward reactor and the upward reactor are configured so that the outlet temperature of the upward reactor is 10-100°C higher than the outlet temperature of the downward reactor.

[0023] Optionally, the oil agent outlet of the downward reactor and the oil agent inlet of the upward reactor are connected by an oil agent delivery pipe; the second catalyst output pipe to be regenerated is connected to the first stripper and the first regenerator; the first catalyst delivery pipe and the second catalyst delivery pipe are respectively connected to the catalyst outlet of the first regenerator.

[0024] Optionally, the system is further provided with a gas-solid quick separation device, the inlet of the gas-solid quick separation device is connected to the oil agent outlet of the downward reactor, and the gas outlet of the gas-solid quick separation device is connected to the oil agent inlet of the upward reactor; preferably, the system is further provided with a second stripper and a second regenerator, the second stripper is provided with a stripping steam input pipe and a first catalyst to be regenerated output pipe, the solid outlet of the gas-solid quick separation device is connected to the solid inlet of the second stripper, and the outlet of the first catalyst to be regenerated output pipe is connected to the inlet of the second regenerator; the second catalyst to be regenerated output pipe is connected to a third stripper and a third regenerator; the inlet of the second catalyst delivery pipe is respectively connected to the catalyst outlet of the second regenerator and the catalyst outlet of the third regenerator.

[0025] Optionally, the inlet of the first catalyst delivery pipe is respectively connected to the second catalyst output pipe to be regenerated, the catalyst outlet of the second regenerator and the catalyst outlet of the third regenerator.

[0026] Optionally, the down-flow reactor is a straight pipe of constant or variable diameter, and the up-flow reactor is a single or composite reactor selected from a riser of constant or variable diameter, a fluidized bed and a fast bed.

[0027] Beneficial effects:

[0028] In the method and system for producing light olefins by catalytic cracking of the present invention, the feedstock oil and the first catalyst first enter the down-flow reactor to carry out the first catalytic cracking reaction, and then the second catalytic cracking reaction at a higher temperature is carried out in the up-flow reactor. At the same time, the second catalyst is introduced into the up-flow reactor, and in particular, the outlet temperature of the up-flow reactor is controlled to be 10-100°C higher than the outlet temperature of the down-flow reactor, thereby significantly improving the yield and selectivity of light olefins. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a structural schematic diagram of a specific embodiment of a system for producing light olefins through catalytic cracking provided by the present invention;

[0030] Figure 2 This is a schematic structural diagram of another specific embodiment of a system for producing light olefins by catalytic cracking provided by the present invention;

[0031] Description of Reference Numerals

[0032] 1 downward reactor; 2 upward reactor; 3 oil agent delivery pipe; 4 second stripper;

[0033] 11 crude oil feed nozzle; 12 first catalyst delivery pipe; 13 gas-solid quick separation equipment;

[0034] 21 second catalyst delivery pipe; 22 oil agent output pipe;

[0035] 41 is a stripping steam input pipe; 42 is a first catalyst output pipe. DETAILED DESCRIPTION

[0036] The present application will be further described in detail below through the accompanying drawings and examples, through which the features and advantages of the present application will become more clear and distinct.

[0037] The word "exemplary" is used exclusively herein to mean "serving as an example, example, 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 indicated.

[0038] 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.

[0039] In a first aspect, the present invention relates to a method for producing light olefins by catalytic cracking, the method comprising: (1) contacting a feedstock oil with a first catalyst in a down-flow reactor to carry out a first catalytic cracking reaction to obtain a first oil-agent mixture, wherein the first oil-agent mixture comprises a first reaction oil gas and a first catalyst to be regenerated; (2) contacting the first reaction oil gas with a second catalyst in an up-flow reactor to carry out a second catalytic cracking reaction to obtain a second oil-agent mixture; (3) separating the second oil-agent mixture to obtain a second reaction oil gas and a second catalyst to be regenerated, and separating the second reaction oil gas to obtain light olefins; wherein the outlet temperature of the up-flow reactor is 10-100°C higher than the outlet temperature of the down-flow reactor.

[0040] It should be noted that in the method for producing light olefins by catalytic cracking of the present invention, the feedstock oil and the first catalyst first enter the downward reactor for a first catalytic cracking reaction, and then enter the upward reactor for a second catalytic cracking reaction at a higher temperature. At the same time, the second catalyst is introduced into the upward reactor, and in particular, the outlet temperature of the upward reactor is controlled to be 10-100°C higher than the outlet temperature of the downward reactor, thereby significantly improving the yield and conversion rate of light olefins.

[0041] According to the first embodiment of the first aspect of the present invention, the downward reactor and the upward reactor are directly connected through an oil agent delivery pipe, and the first oil agent mixture containing the first reaction oil gas is directly delivered to the upward reactor through the oil agent delivery pipe, so that the first reaction oil gas and the second catalyst contact in the upward reactor to carry out the second catalytic cracking reaction.

[0042] It should be noted that, in this embodiment, the first oil mixture (comprising the first reaction oil gas and the first regenerated catalyst) obtained by the reaction of the feedstock oil and the first catalyst in the downward reactor is not separated and directly enters the upward reactor to continue catalytic cracking to obtain the second reaction oil gas and the second regenerated catalyst, and the obtained second reaction oil gas is subjected to product separation to obtain dry gas, liquefied gas, gasoline, diesel and oil slurry, and the obtained second regenerated catalyst is stripped and regenerated to obtain a regenerated catalyst.

[0043] It should be noted that, during the catalytic cracking process, heavy components such as colloids and asphaltenes in the crude oil are preferentially adsorbed on the active centers of the catalyst, but these colloids and asphaltenes often cover the active centers in the form of coke, resulting in reduced catalyst activity and reduced selectivity for cracking of other hydrocarbons. The present invention first converts hydrocarbons once in a high-temperature, short-residence-time downward reactor to generate a large amount of olefin-rich intermediate components, and at the same time, introduces a second catalyst, and uses a higher reaction temperature to further convert the intermediate components into light olefins with high selectivity. This embodiment adopts a downward and upward combined reactor type, and at the same time introduces a high-temperature, highly active second catalyst into the upward reactor, which can flexibly adjust the reaction temperature and catalyst activity, and can match the cracking performance of different hydrocarbon molecules in the catalytic cracking process, which is beneficial to improving the yield and selectivity of light olefins.

[0044] According to a first embodiment of the first aspect of the present invention, the method further comprises: stripping and regenerating the second spent catalyst; the first catalyst and the second catalyst are each independently selected from a regenerated catalyst and / or a cooled regenerated catalyst.

[0045] It should be noted that in this embodiment, the regenerated catalyst serving as the first or second catalyst can be the regenerated catalyst obtained by stripping and regenerating the second spent catalyst. Using the regenerated catalyst as the first or second catalyst not only effectively provides reactive sites but also introduces heat to maintain a high temperature in the downflow reactor or upflow reactor for catalytic cracking of hydrocarbons to produce light olefins, thus forming a highly effective self-circulating system.

[0046] According to a second embodiment of the first aspect of the present invention, a gas-solid quick separation device is provided between the downward reactor and the upward reactor, and the first oil agent mixture is separated into the first reaction oil and gas and the first catalyst to be generated via the gas-solid quick separation device; the first reaction oil and gas is transported to the upward reactor so that the first reaction oil and gas contact the second catalyst in the upward reactor to carry out the second catalytic cracking reaction.

[0047] It should be noted that this embodiment is the preferred embodiment. It uses a gas-solid rapid separation device to separate the first spent catalyst from the first oil mixture, allowing only the first reaction oil and gas to enter the ascending reactor to contact the second catalyst for further catalytic cracking. The second catalyst has greater catalytic activity than the first spent catalyst, allowing the first reaction oil and gas to undergo better catalytic cracking in the ascending reactor, resulting in the second reaction oil and gas, significantly improving the yield and selectivity of light olefins.

[0048] During the catalytic cracking process, heavy components such as colloids and asphaltenes in the feedstock oil are preferentially adsorbed on the active centers of the catalyst, but these colloids and asphaltenes often cover the active centers in the form of coke, resulting in reduced catalyst activity and reduced selectivity for cracking of other hydrocarbons. This embodiment first converts hydrocarbons in a high-temperature, short-residence downward reactor to generate a large amount of olefin-rich intermediate components, namely the first reaction oil and gas, and separates the severely deactivated first catalyst from the first oil mixture, so that the separated first reaction oil and gas enters the upward reactor and undergoes a catalytic cracking reaction at a higher temperature. A higher temperature and higher density catalyst can be introduced, or external heating can be used to further convert the intermediate components into light olefins with high selectivity. In the method provided by the present invention, the reaction temperature, reaction time and catalyst activity better match the cracking performance of different hydrocarbon molecules in the catalytic cracking process, and the yield and selectivity of light olefins are higher.

[0049] According to a second embodiment of the first aspect of the present invention, the method further includes: stripping and regenerating the first spent catalyst separated by the gas-solid quick separation equipment; stripping and regenerating the second spent catalyst; the second catalyst is a regenerated catalyst and / or a cooled regenerated catalyst.

[0050] It should be noted that, in this embodiment, the regenerated catalyst used for the second catalyst may be the regenerated catalyst obtained by stripping and regenerating the first spent catalyst, or the regenerated catalyst obtained by stripping and regenerating the second spent catalyst.

[0051] According to a second embodiment of the first aspect of the present invention, the first catalyst is selected from a combination of one or more of a regenerated catalyst, a cooled regenerated catalyst and the second catalyst to be regenerated; preferably, the first catalyst is a combination of the regenerated catalyst and the second catalyst to be regenerated; further preferably, the first catalyst is the second catalyst to be regenerated.

[0052] It should be noted that, in this embodiment, the regenerated catalyst obtained by stripping and regenerating the first spent catalyst and / or the regenerated catalyst obtained by stripping and regenerating the second spent catalyst can be used as the first catalyst.

[0053] It should be noted that, as a preferred embodiment, the regenerated catalyst obtained by stripping and regenerating the first spent catalyst can be returned to the catalytic cracking reaction system for recycling, for example, it can be introduced into the ascending reactor as the second catalyst to catalyze the cracking reaction. Simultaneously, the second spent catalyst is introduced into the descending reactor as the first catalyst to catalyze the cracking reaction. In this preferred embodiment, the catalyst forms two complete closed loops for circulation, thereby improving the yield and selectivity of light olefins.

[0054] It should be noted that it is a more preferred embodiment to use the second catalyst to be regenerated as the first catalyst. The second catalyst to be regenerated is the catalyst after the second catalyst is catalytically cracked with the first reaction oil and gas in the upward reactor. Because the first reaction oil and gas is the oil and gas that has undergone the first catalytic cracking reaction in the downward reactor, the heavy components contained in the components are reduced, and the heavy components such as colloids and asphaltene produced in the upward reactor are significantly reduced. Therefore, the second catalyst to be regenerated still has a certain good catalytic activity and has a certain temperature. Directly using the second catalyst to be regenerated as the first catalyst to catalyze the catalytic cracking in the downward reactor can further enable the catalytic cracking reaction to proceed better.

[0055] According to a second embodiment of the first aspect of the present invention, the residence time of the first oil mixture in the gas-solid fast separation device is less than 0.05s; preferably, the residence time of the first oil mixture in the gas-solid fast separation device is less than 0.03s.

[0056] It should be noted that the gas-solid quick separation equipment can be a separation device such as a cyclone quick separation that can quickly separate oil, gas and catalyst. Within the above-mentioned residence time, the first oil agent mixture can be well separated into catalyst and oil and gas.

[0057] According to the first or second embodiment of the first aspect of the present invention, in step 1, the outlet temperature of the down-type reactor is 500-650°C, and the oil and gas residence time is 0.1-2s; the weight ratio of the first catalyst to the feed oil is (1-50):1; preferably, the outlet temperature of the down-type reactor is 530-600°C, and the oil and gas residence time is 0.5-1.0s; the weight ratio of the first catalyst to the feed oil is (10-30):1.

[0058] It should be noted that by controlling the outlet temperature of the down-flow reactor, the oil and gas residence time, and the weight ratio of the first catalyst to the feedstock oil within the aforementioned parameter ranges, the feedstock oil and the first catalyst can be better contacted in the down-flow reactor to produce an olefin-rich intermediate component, namely the first reaction oil and gas, thereby increasing the olefin content in the first reaction oil and gas. The temperature inside and at the outlet of the down-flow reactor can be maintained by electrical heating and / or controlled by the temperature of the introduced first catalyst.

[0059] According to the first or second embodiment of the first aspect of the present invention, in step 2, the outlet temperature of the upward reactor is 550-700°C, and the oil and gas residence time is 0.5-10s; the weight ratio of the second catalyst to the feedstock oil is (5-50):1; preferably, the outlet temperature of the upward reactor is 560-650°C, and the oil and gas residence time is 1-5s; the weight ratio of the second catalyst to the feedstock oil is (10-30):1.

[0060] It should be noted that by controlling the outlet temperature, oil and gas residence time, and the weight ratio of the second catalyst to the feedstock oil of the ascending reactor within the aforementioned parameter ranges, the first reaction oil and gas can be better converted into the second reaction oil and gas, further improving the yield and selectivity of light olefins. The internal and outlet temperatures of the ascending reactor can be maintained by electrical heating and / or controlled by the temperature of the introduced second catalyst.

[0061] According to the first or second embodiment of the first aspect of the present invention, the feedstock oil is selected from a combination of one or more of crude oil, atmospheric wax oil, vacuum wax oil, atmospheric residue oil, vacuum residue oil, deasphalted oil, hydrogenated heavy oil and coker wax oil; or is selected from a combination of partial fractions or full fractions of one or more of coal liquefaction oil, oil sands oil, shale oil, synthetic oil, and animal and plant oils and fats.

[0062] It should be noted that crude oil, atmospheric gas oil, vacuum gas oil, etc. are petroleum hydrocarbons, while coal liquefaction oil, oil sands oil, shale oil, etc. are mineral oils. The method of producing light olefins by catalytic cracking of the present invention has wide applicability, can effectively catalytically crack a variety of feedstock oils to obtain high light olefin yields and selectivities, and does not require pre-separation of the feedstock oils. The method is simple and energy-efficient.

[0063] In a second aspect, the present invention relates to a system for producing light olefins by catalytic cracking, such as Figure 1 As shown in or 2, the system includes a downward reactor 1 and an upward reactor 2; the oil agent outlet of the downward reactor 1 is fluidically connected to the oil agent inlet of the upward reactor 2; the top of the downward reactor 1 is respectively provided with a raw oil feed nozzle 11 and a first catalyst delivery pipe 12; the bottom of the upward reactor 2 is provided with a second catalyst delivery pipe 21, and the top of the upward reactor 2 is provided with an oil agent output pipe 22; the top of the upward reactor 2 is provided with an oil agent separation device, the oil agent inlet of the oil agent separation device is connected to the oil agent output pipe 22, and the oil agent separation device is provided with an oil and gas output pipe and a second catalyst output pipe to be generated; the oil and gas output pipe is connected to the oil and gas separation device; the downward reactor 1 and the upward reactor 2 are configured so that the outlet temperature of the upward reactor 2 is 10-100°C higher than the outlet temperature of the downward reactor 1.

[0064] The catalytic cracking system of the present invention enables catalytic cracking to be carried out according to the method of the first aspect of the present invention, or in other words, the method of the first aspect of the present invention can be implemented by the system of the second aspect of the present invention.

[0065] It should be noted that in this system, the feedstock is fed into the downward reactor 1 through the feedstock feed nozzle 11 and the first catalyst is fed into the first catalyst delivery pipe 12 from the top, thereby producing a first oil-agent mixture comprising the first reaction oil gas and the first spent catalyst. The second catalyst enters the bottom of the upward reactor 2 through the second catalyst delivery pipe 21 and then contacts the first reaction oil gas (the first oil-agent mixture comprising the first reaction oil gas and the first spent catalyst, or the separated first reaction oil gas) to continue the cracking reaction at a higher reaction temperature. The second oil-agent mixture after the reaction in the upward reactor 2 is discharged through the oil-agent discharge pipe 22 to the oil-agent separation unit for gas-solid separation, thereby producing the second reaction oil gas and the second spent catalyst. The resulting second reaction oil gas is further separated in the oil-gas separation unit, i.e., the fractionation unit, to produce dry gas, liquefied gas, gasoline, diesel, and slurry oil. The resulting second spent catalyst is then introduced into a stripper for stripping. The stripped catalyst is then introduced into a regenerator for regeneration and then recycled back into the catalytic cracking system for producing light olefins.

[0066] According to a first embodiment of the second aspect of the present invention, Figure 1 As shown, the oil agent outlet of the downward reactor 1 and the oil agent inlet of the upward reactor 2 are connected through an oil agent delivery pipe 3; the second catalyst output pipe to be regenerated is connected to the first stripper and the first regenerator; the first catalyst delivery pipe 12 and the second catalyst delivery pipe 21 are respectively connected to the catalyst outlet of the first regenerator.

[0067] It should be noted that the first embodiment of the system of the present invention is applicable to the first embodiment of the method of the present invention, or in other words, the first embodiment of the method of the present invention can be implemented through the first embodiment of the system of the present invention.

[0068] It should be noted that, in this embodiment, the first oil-agent mixture obtained by the reaction in the down-type reactor 1 is directly transported to the up-type reactor 2 through the oil-agent delivery pipe 3 without separation to continue catalytic cracking; the regenerated catalyst obtained in the first regenerator can enter the down-type reactor 1 through the first catalyst delivery pipe 12 for recycling, and can enter the up-type reactor 2 through the second catalyst delivery pipe 21 for recycling.

[0069] According to a second embodiment of the second aspect of the present invention, Figure 2 As shown, the system is further provided with a gas-solid quick separation device 13, the inlet of the gas-solid quick separation device 13 is connected to the oil agent outlet of the downward reactor 1, and the gas outlet of the gas-solid quick separation device 13 is connected to the oil agent inlet of the upward reactor 2; preferably, the system is further provided with a second stripper 4 and a second regenerator, the second stripper 4 is provided with a stripping steam input pipe 41 and a first catalyst to be regenerated output pipe 42, the solid outlet of the gas-solid quick separation device 13 is connected to the solid inlet of the second stripper 4, and the outlet of the first catalyst to be regenerated output pipe 42 is connected to the inlet of the second regenerator; the second catalyst to be regenerated output pipe is connected to a third stripper and a third regenerator; the inlet of the second catalyst delivery pipe 21 is respectively connected to the catalyst outlet of the second regenerator and the catalyst outlet of the third regenerator.

[0070] It should be noted that the second embodiment of the system of the present invention is applicable to the second embodiment of the method of the present invention, or in other words, the second embodiment of the method of the present invention can be implemented through the second embodiment of the system of the present invention.

[0071] It should be noted that the first oil mixture in the downward reactor 1 enters the gas-solid quick separation device 13 to separate the catalyst and oil gas to obtain the first reaction oil gas and the first catalyst to be regenerated. The first reaction oil gas enters the upward reactor 2 through the gas outlet of the gas-solid quick separation device 13 and the oil agent inlet of the upward reactor 2 to continue catalytic cracking. The first catalyst to be regenerated enters the second stripper 4 through the solid outlet of the gas-solid quick separation device 13 for stripping. The stripping steam input pipe 41 inputs water vapor into the second stripper 4. The water vapor removes the hydrocarbon substances adsorbed in the catalyst. After completing the stripping process, the catalyst enters the second regenerator through the first regenerated catalyst output pipe 42 for regeneration. The regenerated catalyst obtained in the second regenerator and / or the regenerated catalyst obtained in the third regenerator can enter the upward reactor 2 through the second catalyst delivery pipe 21 and be used as the second catalyst. The second regenerator and the third regenerator can be the same regenerator or different regenerators. The regenerated catalysts obtained in the second regenerator and the third regenerator can be returned to the system for recycling.

[0072] According to a second embodiment of the second aspect of the present invention, Figure 2 As shown, the inlet of the first catalyst delivery pipe 12 is respectively connected to the second catalyst outlet pipe to be regenerated, the catalyst outlet of the second regenerator and the catalyst outlet of the third regenerator.

[0073] It should be noted that, in this embodiment, the first catalyst may be selected from one or more combinations of the second catalyst to be regenerated, the regenerated catalyst obtained from the second regenerator, and the regenerated catalyst obtained from the third regenerator.

[0074] According to the first or second embodiment of the second aspect of the present invention, Figure 1 Or as shown in 2, the downward reactor is a straight pipe of constant diameter or variable diameter, and the upward reactor is a single or composite reactor selected from a riser of constant diameter or variable diameter, a fluidized bed and a fast bed.

[0075] It should be noted that in the method or system of the present invention, a downflow reactor may refer to a reactor in which the oil solution flows downward, and an upflow reactor may refer to a reactor in which the oil solution flows upward. Downflow reactors are not limited to straight pipes of constant or variable diameters; any reactor capable of downward oil solution flow may be used. Upflow reactors are also not limited to the types specified above; any reactor capable of upward oil solution flow may be used.

[0076] The present invention is further described in detail below by way of examples, which are not intended to limit the present invention.

[0077] The catalytic cracking catalyst used in the following examples and comparative examples was produced by the Qilu Branch of Sinopec Catalyst Co., Ltd., under the trade designation EP-3B. This catalyst contains a ZSP molecular sieve with an average pore size of less than 0.7 nanometers and an ultrastable Y-type molecular sieve. Prior to use, the catalyst was hydrothermally aged at 800°C with saturated steam for 17 hours. The main physicochemical properties of the catalyst are shown in Table 1. The properties of the feedstock oils used in the examples and comparative examples are listed in Table 2.

[0078] In the following examples and comparative examples, the calculation method and the like are described as follows:

[0079] The product distribution values of dry gas, liquefied gas and gasoline in the table represent mass fractions; among them, the dry gas yield is the sum of the mass fractions of H2, CH4 and C2 hydrocarbons in the product; the liquefied gas yield is the sum of the mass fractions of C3 and C4 hydrocarbons in the product; the gasoline yield is the yield of liquids with a boiling point less than 221°C in the product; the diesel yield is the yield of liquids with a boiling point of 221°C to 331°C in the product; and the slurry oil yield is the yield of liquids with a boiling point greater than 331°C in the product.

[0080] Conversion rate (%) = 100% - diesel yield - slurry yield;

[0081] Triene yield (%) = ethylene yield + propylene yield + butene yield;

[0082] Triene selectivity = triene yield ÷ conversion rate.

[0083] Table 1

[0084]

[0085] Table 2

[0086]

[0087] Example 1

[0088] The experiment was carried out using a modified medium-sized unit with continuous reaction-regeneration operation, such as Figure 1As shown in the figure. In this medium-sized device, the down-flow reactor 1 is a straight tube with an inner diameter of 30 mm and a length of 1200 mm. The riser reactor, serving as the ascending reactor 2, has an inner diameter of 36 mm and a length of 4600 mm. Down-flow reactor 1 and ascending reactor 2 are directly connected by an oil delivery pipe 3. A 670°C high-temperature regenerated catalyst is introduced into the top of down-flow reactor 1 via a first catalyst delivery pipe 12. Preheated feedstock, after being atomized with steam, enters down-flow reactor 1 through feedstock feed nozzle 11, where it contacts the hot regenerated catalyst for catalytic cracking. The reacted oil is then directly introduced into the bottom of the riser reactor via oil delivery pipe 3, where it contacts the 670°C high-temperature regenerated catalyst introduced via a second catalyst delivery pipe 21 for further cracking. The reacted oil is then introduced into an oil separation system. The separated reaction oil gas is then introduced into a product separation system for separation into gaseous and liquid products. The separated catalyst is then stripped and introduced into a regenerator for char regeneration. The regenerated catalyst is then returned to the reactor for recycling via the first and second catalyst delivery pipes 12 and 21. Medium-sized devices use electric heating to maintain the temperature of the reaction-regeneration system.

[0089] The main operating conditions and results are listed in Table 3.

[0090] Comparative Example 1

[0091] The test was conducted using the apparatus and method of Example 1, with the difference from Example 1 being that the outlet temperature of the riser reactor was lower than the outlet temperature of the downcomer reactor (see Table 3 for details).

[0092] The main operating conditions and results are listed in Table 3.

[0093] Table 3

[0094]

[0095]

[0096] Note: The reaction time of the down-type reactor and the reaction time of the riser reactor refer to the residence time of oil and gas in the reactor respectively.

[0097] As can be seen from the data in Table 3, Example 1 uses the method and system for producing light olefins by catalytic cracking provided by the present invention, which not only has a high triene yield but also a high triene selectivity.

[0098] Example 2

[0099] The experiment was carried out using a modified medium-sized unit with continuous reaction-regeneration operation, such as Figure 2As shown in the figure, this medium-sized unit features a straight tube with an inner diameter of 30 mm and a length of 1200 mm for the downstream reactor 1. The riser reactor serving as the ascending reactor 2 has an inner diameter of 36 mm and a length of 4600 mm. A cyclonic rapid separation is used between the downstream and ascending reactors 1 and 2 to separate the oil and liquid.

[0100] The 670°C high-temperature regenerated catalyst is introduced into the top of the down-type reactor 1 via the first catalyst delivery pipe 12. The preheated feedstock, after being atomized with water vapor, enters the down-type reactor 1 through the feedstock oil feed nozzle 11, where it contacts the hot regenerated catalyst for a catalytic cracking reaction. The reacted oil is separated into the reaction oil gas and the regenerated catalyst through a cyclonic fast separation (residence time of 0.03s). The regenerated catalyst is then stripped and introduced into the regenerator for charring and regeneration. The reaction oil gas immediately enters the bottom of the riser reactor, where it contacts the 670°C high-temperature regenerated catalyst introduced via the second catalyst delivery pipe 21 to continue the cracking reaction. The reacted oil is introduced into the oil separation system, and the separated reaction oil gas is introduced into the product separation system for separation into gaseous and liquid products. The separated catalyst (the second regenerated catalyst) is also stripped and introduced into the regenerator for charring and regeneration.

[0101] The regenerated catalyst is returned to the reactor for recycling via the first catalyst delivery pipe 12 and the second catalyst delivery pipe 21. The medium-sized device uses electric heating to maintain the temperature of the reaction-regeneration system.

[0102] The main operating conditions and results are listed in Table 4.

[0103] Example 3

[0104] Using the device of Example 2 ( Figure 2 ) and method were tested, which differed from Example 2 in that:

[0105] The first catalyst used in the downward reactor 1 is all the catalyst (second catalyst to be regenerated) separated after the reaction in the upward reactor 2 riser reactor. The temperature of the second catalyst to be regenerated entering the downward reactor is 620°C, the outlet temperature of the riser reactor is 620°C, and the catalyst-oil mass ratio of the riser reactor is 15.

[0106] The main operating conditions and results are listed in Table 4.

[0107] Comparative Example 2

[0108] Using the device of Example 2 ( Figure 2 ) and method were tested, which differed from Example 2 in that:

[0109] The outlet temperature of the riser reactor of the upward reactor 2 is lower than the outlet temperature of the downward reactor 1.

[0110] The main operating conditions and results are listed in Table 4.

[0111] Table 4

[0112]

[0113]

[0114] Note: The reaction time of the down-type reactor and the reaction time of the riser reactor refer to the residence time of oil and gas in the reactor respectively.

[0115] As can be seen from the data in Table 4, Examples 2 and 3 use the method and system for producing light olefins by catalytic cracking provided by the present invention, which not only has a high triene yield but also a high triene selectivity. In particular, in Example 3, the first catalyst used in the down-flow reactor 1 is entirely the catalyst (second to-be-generated catalyst) obtained by separation after the reaction in the riser reactor of the up-flow reactor 2. The temperature and activity of the second to-be-generated catalyst allow the feedstock in the down-flow reactor 1 to undergo the first catalytic cracking reaction more effectively, thereby obtaining a first reaction oil gas with a higher olefin content. Furthermore, after the second catalytic cracking reaction is carried out in the up-flow reactor 2, the yield of propylene and butene in the second reaction oil gas obtained by the reaction is higher, and in particular, the triene yield and triene selectivity are significantly improved.

[0116] In the description of this application, it should be noted that the terms "upper", "lower", "inside", "outside", "front", "back", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships in the working state of this application. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on this application.

[0117] In the description of this application, it should be noted that, unless otherwise specified or limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0118] The present application has been described above in conjunction with preferred embodiments, but these embodiments are merely exemplary and serve only as an illustrative example. On this basis, various replacements and improvements can be made to the present application, all of which fall within the scope of protection of the present application.

Claims

1. A method for producing light olefins by catalytic cracking, wherein: The method includes: (i) contacting a feedstock oil with a first catalyst in a down-flow reactor to perform a first catalytic cracking reaction to obtain a first oil-agent mixture, wherein the first oil-agent mixture comprises a first reaction oil gas and a first spent catalyst; (ii) contacting the first reaction oil and gas with a second catalyst in an ascending reactor to perform a second catalytic cracking reaction to obtain a second oil mixture; (iii) separating the second oil mixture to obtain a second reaction oil gas and a second spent catalyst, and separating the second reaction oil gas to obtain light olefins; The outlet temperature of the upward reactor is 10-100°C higher than the outlet temperature of the downward reactor, and wherein a gas-solid quick separation device is provided between the downward reactor and the upward reactor, and the first oil agent mixture is separated into the first reaction oil gas and the first catalyst to be generated via the gas-solid quick separation device; the first reaction oil gas is transported to the upward reactor so that the first reaction oil gas contacts the second catalyst in the upward reactor to perform the second catalytic cracking reaction, and the residence time of the first oil agent mixture in the gas-solid quick separation device is less than 0.05s, wherein the gas-solid quick separation device is a cyclone-type quick separation device, and The first spent catalyst separated by the gas-solid quick separation device is stripped and regenerated to obtain a regenerated catalyst, and the regenerated catalyst enters the upward reactor as the second catalyst. At the same time, the second spent catalyst enters the downward reactor as the first catalyst.

2. The method according to claim 1, wherein The method further comprises: stripping and regenerating the second spent catalyst; The second catalyst is a regenerated catalyst and / or a cooled regenerated catalyst.

3. The method according to claim 2, wherein: The first catalyst is selected from a combination of a regenerated catalyst and the second catalyst to be regenerated, a combination of a cooled regenerated catalyst and the second catalyst to be regenerated, and a combination of a regenerated catalyst, a cooled regenerated catalyst and the second catalyst to be regenerated.

4. The method according to claim 3, wherein: The first catalyst is a combination of the regenerated catalyst and the second catalyst to be regenerated.

5. The method according to claim 1, wherein The residence time of the first oil agent mixture in the gas-solid quick separation equipment is less than 0.03s.

6. The method according to claim 1, wherein In step (1), the outlet temperature of the downward reactor is 500-650° C., the oil and gas residence time is 0.1-2 s; and the weight ratio of the first catalyst to the feedstock oil is (1-50):

1.

7. The method according to claim 6, wherein: The outlet temperature of the downward reactor is 530-600° C., and the oil and gas residence time is 0.5-1.0 s. The weight ratio of the first catalyst to the feedstock oil is (10-30):

1.

8. The method according to claim 1, wherein In step (2), the outlet temperature of the upward reactor is 550-700° C., the oil and gas residence time is 0.5-10 s; and the weight ratio of the second catalyst to the feedstock oil is (5-50):

1.

9. The method according to claim 8, wherein The outlet temperature of the upward reactor is 560-650° C., and the oil and gas residence time is 1-5 s. The weight ratio of the second catalyst to the feedstock oil is (10-30):

1.

10. The method according to claim 1, wherein The raw oil is selected from one or more combinations of crude oil, atmospheric wax oil, vacuum wax oil, atmospheric residue oil, vacuum residue oil, deasphalted oil, hydrogenated heavy oil and coker wax oil; or is selected from one or more partial fractions or full fractions of coal liquefaction oil, oil sand oil, shale oil, synthetic oil, animal and plant oils and fats.

11. A system for producing light olefins by catalytic cracking, wherein: The system comprises a down-flow reactor (1) and an up-flow reactor (2); an oil agent outlet of the down-flow reactor (1) is fluidically connected to an oil agent inlet of the up-flow reactor (2); The top of the downward reactor (1) is provided with a raw oil feed nozzle (11) and a first catalyst delivery pipe (12); the bottom of the upward reactor (2) is provided with a second catalyst delivery pipe (21); and the top of the upward reactor (2) is provided with an oil agent output pipe (22); An oil separation device is provided at the top of the upward reactor (2); the oil inlet of the oil separation device is connected to the oil output pipe (22); the oil separation device is provided with an oil and gas output pipe and a second catalyst output pipe to be generated; the oil and gas output pipe is connected to the oil and gas separation device; The down-flow reactor (1) and the up-flow reactor (2) are configured such that the outlet temperature of the up-flow reactor (2) is 10-100° C. higher than the outlet temperature of the down-flow reactor (1). The system is further provided with a gas-solid quick separation device (13), the inlet of the gas-solid quick separation device (13) is connected to the oil agent outlet of the downward reactor (1), and the gas outlet of the gas-solid quick separation device (13) is connected to the oil agent inlet of the upward reactor (2), wherein the first oil agent mixture from the oil agent outlet of the downward reactor (1) has a residence time of less than 0.05s in the gas-solid quick separation device and is separated into a first reaction oil gas and a first catalyst to be generated by the gas-solid quick separation device, and the gas-solid quick separation device is a cyclone-type quick separation device. The system is configured to strip and regenerate the first spent catalyst to obtain a regenerated catalyst, and the regenerated catalyst enters the upward reactor as the second catalyst, while the second spent catalyst enters the downward reactor as the first catalyst.

12. The system according to claim 11, further comprising a second stripper (4) and a second regenerator, wherein the second stripper (4) is provided with a stripping steam input pipe (41) and a first catalyst output pipe (42) to be regenerated, the solid outlet of the gas-solid quick separation device (13) is connected to the solid inlet of the second stripper (4), and the outlet of the first catalyst output pipe (42) to be regenerated is connected to the inlet of the second regenerator; The second catalyst output pipe to be regenerated is connected to a third stripper and a third regenerator; The inlet of the second catalyst delivery pipe (21) is respectively connected to the catalyst outlet of the second regenerator and the catalyst outlet of the third regenerator.

13. The system according to claim 12, wherein: The inlet of the first catalyst delivery pipe (12) is respectively connected to the second catalyst output pipe to be regenerated, the catalyst outlet of the second regenerator and the catalyst outlet of the third regenerator.

14. The system according to claim 11 or 12, characterized in that The down-flow reactor is a straight pipe of constant or variable diameter, and the up-flow reactor is a single or composite reactor selected from a riser of constant or variable diameter, a fluidized bed and a fast bed.

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