A process for the catalytic cracking continuous production of ethylene and propylene

Abstract

The present disclosure relates to a method for continuously producing ethylene and propylene by catalytic cracking, which comprises: contacting a carbon four or more olefin raw material with a catalytic cracking catalyst in a fluidized bed reactor to carry out a catalytic cracking reaction to obtain a reaction material; carrying out a first separation on the reaction material to obtain spent catalyst and a reaction oil gas containing ethylene and propylene; introducing the spent catalyst into a reactor receiver, and returning a first part of the spent catalyst in the reactor receiver to the fluidized bed reactor; introducing a second part of the spent catalyst into a regenerator to regenerate the spent catalyst, and then returning the regenerated catalyst to the fluidized bed reactor. By using the method of the present disclosure, the advantages of the fluidized bed reactor can be utilized to continuously produce ethylene and propylene, the regeneration and decoking process can be flexibly adjusted to help maintain the heat balance of the system, and the yield of ethylene and propylene can be stabilized.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of petroleum chemical industry, in particular, to a method for continuously producing ethylene and propylene by catalytic cracking. BACKGROUND

[0002] Ethylene and propylene play an important role in the petroleum chemical industry as basic organic chemical raw materials. At present, tubular furnace steam cracking is the traditional technology for producing ethylene and propylene. However, this process has technical drawbacks such as high energy consumption, low propylene / ethylene yield ratio, and large carbon dioxide emission, and it is almost impossible to meet the current market demand for low-carbon olefins through technological innovation. China has a large amount of light hydrocarbon resources, but the utilization efficiency is low. Catalytic cracking of low-value C4+ olefin raw materials to produce ethylene and propylene has important application prospects.

[0003] US2010022810A1 discloses a method for producing propylene by catalytic cracking of C4+ olefin raw materials, which uses an adiabatic fixed-bed reactor and silver-modified MFI molecular sieve as catalyst. The propylene yield can reach more than 26% under the conditions of a reaction temperature of 500-580℃, a hydrocarbon partial pressure of 0.05-0.3MPa, and a weight hourly space velocity of 2-20h -1

[0004] US20030062291A1 discloses a process for producing low-carbon olefins by olefin cracking, in which the raw material containing olefins passes through the catalyst beds of MFI molecular sieve and MEL molecular sieve in turn. The inlet temperature of the reactor is 500-600℃, and the process is operated using parallel switching reactors.

[0005] CN1915928A discloses a method for continuously producing propylene by switching, which uses a group of parallel multi-stage fixed-bed reactors. The catalyst bed layers have 3-5 beds, of which 1-2 beds are in a regenerated state. Each catalyst bed is operated in turn at a certain time interval to ensure that the reaction product composition entering the next process is stable. The initial propylene yield is 26.38% using etherified C4 from an ethylene plant as raw material.

[0006] Due to the characteristics of fixed-bed reactors such as close to plug flow of fluid flow, easy adjustment of residence time and reaction temperature, and simple structure, olefin catalytic cracking reactors mainly use fixed-bed reactors. The carbon deposited during the olefin cracking process leads to deactivation of the catalyst. In order to restore the activity of the catalyst, the olefin catalytic cracking process usually sets two or more reactors and adopts a frequent switching regeneration operation mode, which increases the operation difficulty and cost to some extent. SUMMARY

[0007] ​The purpose of the present disclosure is to further improve the yield of low-carbon olefins, and provide a method for continuously producing ethylene and propylene by catalytic cracking.

[0008] To achieve the above-mentioned purpose, the present disclosure provides a method for continuously producing ethylene and propylene by catalytic cracking, which comprises: contacting a carbon four or more olefin raw material with a catalytic cracking catalyst in a fluidized bed reactor to carry out a catalytic cracking reaction to obtain a reaction material; carrying out a first separation on the reaction material to obtain a spent catalyst and a reaction oil gas containing ethylene and propylene; introducing the spent catalyst into a reactor receiver, and returning a first part of the spent catalyst therein to the fluidized bed reactor; introducing a second part of the spent catalyst into a regenerator for regeneration, and then returning the obtained regenerated catalyst to the fluidized bed reactor.

[0009] Optionally, the carbon four or more olefin raw material is from one or more of a refinery catalytic cracking unit, an ethylene plant steam cracking unit, a chemical plant etherization unit, an MTO unit and an MTP unit; the olefins in the carbon four or more olefin raw material are C4-C12 olefins, preferably C4-C6 olefins.

[0010] Optionally, the content of olefins in the carbon four or more olefin raw material is 30% by weight or more, preferably 40% by weight or more; the content of dienes in the carbon four or more olefin raw material is 1% by weight or less, preferably 0.5% by weight or less.

[0011] Optionally, the ratio of the first part of the spent catalyst returned to the fluidized bed reactor to the volumetric flow rate of the spent catalyst entering the reactor receiver is 0.01-0.5, preferably 0.1-0.3.

[0012] Optionally, the fluidized bed reactor is selected from one or more of a riser reactor, a dense phase fluidized bed reactor, an upward conveying line and a downward conveying line.

[0013] Optionally, the conditions of the catalytic cracking reaction include: a reaction temperature of 500-700℃, an oil gas residence time of 0.2-5 seconds, a reaction pressure of 0.1-1MPa, and a catalyst / oil weight ratio of 4-50.

[0014] Optionally, the fluidized bed reactor is a riser reactor; the carbon four or more olefin raw material is introduced into the lower part of the riser reactor; the method further comprises injecting steam into the riser reactor, and the weight ratio of the injected steam to the carbon four or more olefin raw material is 0.1-1, preferably 0.1-0.5.

[0015] Optionally, the method further comprises: separating ethylene, propylene and a C4 or more fraction from the reaction oil gas; and optionally, returning the C4 or more fraction to the fluidized bed reactor for further reaction.

[0016] Optionally, the regeneration conditions in the regenerator include: a regeneration temperature of 600-750℃, preferably 650-700℃; a gas superficial linear velocity of 0.2-3 m / s, preferably 0.5-2 m / s; an average residence time of the spent catalyst of 0.5-3 min, preferably 0.8-2 min.

[0017] Optionally, the method further comprises: heating the first portion of the spent catalyst to above 580℃ before returning to the fluidized bed reactor.

[0018] Optionally, the catalytic cracking catalyst comprises a molecular sieve, an inorganic oxide binder and a carrier; the content of the molecular sieve is 1-60% by weight based on the total weight of the catalytic cracking catalyst; the content of the inorganic oxide binder is 5-99% by weight; the content of the carrier is 0-70% by weight; the molecular sieve is an MFI molecular sieve; the MFI structure molecular sieve is selected from a ZSM molecular sieve and / or a ZRP molecular sieve; the ZSM molecular sieve is selected from one or more of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, preferably a ZSM-5 molecular sieve; the carrier is selected from one or more of kaolin, montmorillonite, diatomite, pachnodytes, sepiolite, halloysite, hydrotalcite, bentonite and rectorite; the inorganic oxide binder is one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silicon aluminum.

[0019] Optionally, the MFI structure molecular sieve is an MFI structure molecular sieve modified by phosphorus and / or a transition metal, and the transition metal is selected from one or more of iron, cobalt and nickel.

[0020] By the above technical solution, the method of the present disclosure is adopted, and the catalytic cracking reaction is carried out by using the fluidized bed reactor, so that the reaction and regeneration cycle can be carried out, and ethylene and propylene can be continuously produced, thereby avoiding frequent switching of the regeneration operation mode of multiple fixed bed reactors, reducing the process operation difficulty and cost; the reactor receiver can control the flow of the spent catalyst into the regenerator, flexibly adjust the regeneration and coking process, and maintain the system heat balance; at the same time, the method can maintain a relatively high reaction activity of the catalytic cracking catalyst, and the yield of the product ethylene and propylene is relatively stable.

[0021] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments section. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and together with the following specific embodiments, serve to explain the present disclosure but do not constitute a limitation thereof. In the drawings:

[0023] Figure 1 is a flow diagram of one specific embodiment of the method for continuously producing ethylene and propylene by catalytic cracking provided by the present application.

[0024] Legend of reference signs

[0025] 1, riser reactor; 2, settler; 3, reactor receiver; 4, regenerator; 5, pre-lift medium; 6, C4+ olefin feedstock; 7, atomizing steam; 8, cyclone; 9, gas collection chamber; 10, reaction oil gas; 11, settler stripping section; 12, stripping steam; 13, spent catalyst; 14, second part of spent catalyst; 15, first part of spent catalyst; 16, main air; 17, cyclone; 18, regenerated catalyst. DETAILED DESCRIPTION

[0026] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0027] The present disclosure provides a method for continuously producing ethylene and propylene by catalytic cracking, which comprises: contacting a C4+ olefin feedstock with a catalytic cracking catalyst in a fluidized bed reactor to perform a catalytic cracking reaction, to obtain a reaction material; performing a first separation on the reaction material to obtain a spent catalyst and a reaction oil gas containing ethylene and propylene; introducing the spent catalyst into a reactor receiver, and returning a first part of the spent catalyst in the reactor receiver to the fluidized bed reactor; introducing a second part of the spent catalyst into a regenerator for regeneration, and then returning the obtained regenerated catalyst to the fluidized bed reactor.

[0028] By the above technical solution, the method provided by the present disclosure is used, and the catalytic cracking reaction is performed by using a fluidized bed reactor, so that the reaction and regeneration cycle can be performed, ethylene and propylene can be continuously produced, the process operation difficulty and cost are reduced by avoiding frequent switching of the regeneration operation mode of multiple fixed bed reactors; the reactor receiver can control the flow rate of the spent catalyst entering the regenerator, flexibly adjust the regeneration and coking process, and maintain the heat balance of the system; at the same time, the method can maintain a relatively high reaction activity of the catalytic cracking catalyst, and the yield of the products ethylene and propylene is relatively stable.

[0029] The inventors of the present application found in the research process that the coke yield of light olefin single-pass catalytic cracking is low, for example, the coke yield of C4 olefin single-pass catalytic cracking is less than 2%, and it is difficult to maintain the heat balance of the fluidized bed reaction system with the low coke yield; appropriately increasing the use frequency of the catalyst can still maintain a relatively high yield of ethylene and propylene, and the coke content of the catalyst is increased. Therefore, for the olefin fluidized bed catalytic cracking process, appropriately increasing the use frequency of the catalyst can not only maintain a relatively high yield of ethylene and propylene, but also help to improve the heat balance of the system.

[0030] In one embodiment, the C4+ olefin feedstock is from one or more of catalytic cracking unit of refinery, steam cracking unit of ethylene plant, etherization unit of chemical plant, MTO unit and MTP unit; the olefins in the C4+ olefin feedstock are C4-C12 olefins, preferably C4-C6 olefins.

[0031] In one embodiment, the content of olefins in the C4+ olefin feedstock is 30 wt% or more, preferably 40 wt% or more, for example, the content of C4 fraction olefins in catalytic cracking is higher than 50 wt%, the content of C4 fraction olefins in MTBE is 50 wt%; the content of dienes in the C4+ olefin feedstock is 1 wt% or less, preferably 0.5 wt% or less.

[0032] In one embodiment, when the C4+ olefin feedstock is from the steam cracking unit of ethylene plant, the C4+ olefin fraction produced by the steam cracking unit of ethylene plant is hydrotreated to reduce the content of dienes to 1 wt% or less, preferably 0.5 wt% or less.

[0033] In one embodiment, the method further comprises that the ratio of the first part of spent catalyst returned to the fluidized bed reactor to the volumetric flow rate of the spent catalyst entering the reactor receiver is 0.01-0.5, preferably 0.05-0.4, and further preferably 0.1-0.3. The ratio of the flow rate of the first part of spent catalyst to the second part of spent catalyst can be controlled by the reactor receiver, and the heat balance of the system can be further maintained.

[0034] In this embodiment, the reactor receiver has the functions of buffering and controlling, the buffering function refers to establishing a certain catalyst level in the spent catalyst receiver, and the controlling function refers to adjusting the flow of the spent catalyst into the regenerator and directly returning to the fluidized bed reactor according to the level of the catalyst in the receiver, thereby playing a role in adjusting the coking effect of the regenerator. The first part of the spent catalyst returning to the fluidized bed reactor can increase the number of times the catalyst is used, help to increase the carbon content on the surface of the catalyst, and thus can increase the reaction temperature during the regeneration of the catalyst. In order to meet the needs of the reaction conditions, the first part of the spent catalyst can be heated before entering the fluidized bed reactor, so that its temperature is not lower than 580 DEG C, for example, the first part of the spent catalyst can be heated in the regenerator external heat exchanger, specifically, the first part of the spent catalyst can be heated by heat exchange with high-temperature regenerated catalyst in the regenerator external heat exchanger, which is a conventional technical method in the art, and the present application has no limitation on this. In a further embodiment, the first part of the spent catalyst returning to the fluidized bed reactor is injected from the lower part of the fluidized bed reactor, preferably between the high-temperature regenerated catalyst and the C4+ olefin feed, which helps to further increase the temperature of the first part of the spent catalyst.

[0035] In an embodiment, the fluidized bed reactor can be at least one of a riser reactor, a dense phase fluidized bed reactor, an upflowing conveying line and a downflowing conveying line, can be a combination of the above-mentioned reactors, or can be a combination of a plurality of one kind of reactor, and the combination can be in series and / or in parallel. The riser reactor can be a conventional riser reactor with equal diameter or a riser reactor with various forms of variable diameter.

[0036] According to a preferred embodiment of the present application, the fluidized bed reactor is preferably a riser reactor, and the C4+ olefin raw material is introduced into the lower part of the riser reactor. The riser reactor sequentially includes a pre-lifting section and at least one reaction zone from bottom to top, further, the C4+ olefin raw material can be introduced into the riser reactor from the pre-lifting section, and further, the pre-lifting medium can be introduced into the riser reactor from the bottom of the pre-lifting section.

[0037] In an embodiment, the first separation is gas-solid separation, and the method for producing ethylene and propylene by catalytic cracking disclosed by the present application can comprise: performing gas-solid separation on the reaction material of the fluidized bed reactor, further separating the separated reaction oil gas to obtain ethylene, propylene, a C4 fraction and other products, and further, the separated C4 fraction can be returned to the fluidized bed reactor as a raw material for continuous reaction. The gas-solid separation process can be performed in a cyclone separator or other gas-solid separation equipment. The method for separating ethylene, propylene and a C4 fraction from the reaction products can use conventional technical methods in the art, and the present application has no limitation on this.

[0038] In one embodiment, the method further comprises injecting steam into the riser reactor, and the weight ratio of the injected steam to the C4+ olefinic feedstock is 0.1-1, preferably 0.1-0.5.

[0039] In one embodiment, the conditions of the catalytic cracking reaction include: a reaction temperature of 500-700°C, preferably 550-680°C; an oil gas residence time of 0.2-5 seconds, preferably 1-4 seconds; a reaction pressure of 0.1-1 MPa, preferably 0.1-0.5 MPa; and a catalyst / oil weight ratio of 4-50, preferably 5-40. The reaction temperature refers to the outlet temperature of the riser reactor or a reaction zone of the riser reactor, and the reaction pressure refers to the gauge pressure.

[0040] In one embodiment, the regeneration conditions of the regenerator include: a regeneration temperature of 600-750°C, preferably 650-700°C; a gas superficial linear velocity of 0.2-3 m / s, preferably 0.5-2 m / s; and an average residence time of the spent catalyst of 0.5-3 minutes, preferably 0.8-2 minutes.

[0041] In this embodiment, the regeneration of the spent catalyst can be carried out according to conventional catalyst regeneration methods in the art, for example: introducing an oxygen-containing gas (such as air) from the bottom of the regenerator, and the spent catalyst is regenerated by contact with the oxygen to produce flue gas, which is subjected to gas-solid separation in a cyclone separator of the regenerator, and then enters a subsequent energy recovery system.

[0042] In one embodiment, the method further comprises further separating the reaction oil gas into ethylene, propylene and a C4+ fraction, and optionally returning the C4+ fraction to the fluidized bed reactor for further reaction.

[0043] In one embodiment, the catalytic cracking catalyst comprises a molecular sieve, an inorganic oxide binder and a carrier; the content of the molecular sieve is 1-60 wt%, preferably 10-55 wt%, based on the total weight of the catalytic cracking catalyst; the content of the inorganic oxide binder is 5-99 wt%, preferably 10-80 wt%; the content of the carrier is 0-70 wt%, preferably 10-60 wt%; the molecular sieve is an MFI molecular sieve; the MFI structure molecular sieve is selected from a ZSM molecular sieve and / or a ZRP molecular sieve; the ZSM molecular sieve is selected from one or more of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, preferably a ZSM-5 molecular sieve; the carrier can be various clays, which are natural and / or artificially synthesized, treated or not treated by various chemical and / or physical methods, commonly used as a carrier of a cracking catalyst, selected from one or more of kaolin, montmorillonite, diatomite, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite, preferably the clay is at least one selected from kaolin, montmorillonite, diatomite and attapulgite; the inorganic oxide binder is one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silicon aluminum.

[0044] In one embodiment, the MFI structure molecular sieve is an MFI structure molecular sieve modified by phosphorus and / or a transition metal, the transition metal is selected from one or more of iron, cobalt and nickel.

[0045] In one embodiment, as shown in Figure 1 the method for continuously producing ethylene and propylene by catalytic cracking comprises: Figure 1As shown, the pre-lifting medium 5 enters from the bottom of the riser reactor 1 via a pipeline. The regenerated catalyst 18 (670-700℃) moves upwards along the riser reactor 1 under the lifting action of the pre-lifting medium 5, mixing with the first part of the spent catalyst 15. Preheated olefin feedstock 6 (C4 and above) to 350-450℃ is injected into the riser reactor 1 along with atomized steam 7, where it contacts the catalytic cracking catalyst to undergo a cracking reaction. The generated reaction oil and gas, along with the carbonized spent catalyst, enters the cyclone separator 8 in the settling tank 2, separating the spent catalyst 13 from the reaction oil and gas 10. The reaction oil and gas enters the gas collecting chamber 9, and then the reaction oil and gas 10 enters the subsequent separation system to obtain ethylene, propylene, and C4 (and above) fractions. The spent catalyst flows to the stripping section 11 of the settling tank, contacting the stripping steam 12. The stripped spent catalyst enters the reactor receiver 3. The first part of the spent catalyst 15 from the reactor receiver 3 is heated to at least 600℃ and returned to the riser reactor 1. The second part of the spent catalyst 14 enters the regenerator 4. The main air 16 from the pipeline enters the regenerator 4, burning off the coke on the second part of the catalyst 14 to be generated in the dense phase bed at the bottom of the regenerator 4. The flue gas enters the subsequent energy recovery system after passing through the cyclone separator 17. The regenerated catalyst 18 is returned to the riser reactor 1 through the regenerated catalyst conveying inclined tube.

[0046] The following embodiments will further illustrate the present invention, but are not intended to limit the invention.

[0047] Unless otherwise specified, all reagents used below are chemically pure. The raw material used in the examples was post-etherified C4 from a chemical plant, containing 46.8% by weight butene and 0.2% by weight diene. The catalytic cracking catalyst was a ZRP molecular sieve catalyst, purchased from Sinopec Catalyst Co., Ltd., Qilu Branch, and its properties are listed in Table 1. The catalyst microreactor activity was tested according to the RIPP 92-90 standard method on a standard cracking catalyst microactivity tester.

[0048] Example 1

[0049] like Figure 1 The method for continuous catalytic cracking production of ethylene and propylene is shown as follows: a pre-lifting medium is introduced from the bottom of the riser reactor through a pipeline, so that the regenerated catalyst at a temperature of 680°C is accelerated upward along the riser reactor under the lifting action of the pre-lifting medium; then, the chemical plant etherified C4, preheated to 390°C, is injected into the riser reactor together with the atomizing medium (water vapor) to contact the catalytic cracking catalyst and undergo a catalytic cracking reaction.

[0050] The generated reaction oil gas and carbon-containing spent catalyst enter a cyclone in the settler to separate the spent catalyst from the reaction oil gas. The reaction oil gas enters a gas collection chamber and then enters a subsequent separation system to separate ethylene, propylene and C4 fraction. The spent catalyst flows to the stripping section of the settler and is contacted with stripping steam for stripping treatment.

[0051] The stripped spent catalyst enters the reactor receiver, a first portion of the spent catalyst is heated to 610℃ and then returned to the riser reactor, and a second portion of the spent catalyst enters the regenerator for regeneration treatment. Main air from the pipeline enters the regenerator to burn off coke on the second portion of the spent catalyst in the dense bed at the bottom of the regenerator. The flue gas enters a subsequent energy recovery system after being separated by a cyclone, and the regenerated catalyst returns to the riser reactor through a regenerated catalyst delivery inclined pipe.

[0052] The conditions of the catalytic cracking reaction are: a reaction temperature of 650℃, an oil gas residence time of 2.0 seconds, a reaction pressure of 0.2 MPa, a weight ratio of catalyst to oil of 16, and a weight ratio of water vapor to C4+ olefin raw material of 0.25. The ratio of the volume flow rate of the first portion of the spent catalyst returned to the fluidized bed reactor to the volume flow rate of the spent catalyst entering the reactor receiver is 0.2.

[0053] The regeneration treatment conditions are: a regeneration temperature of 680℃, a gas superficial linear velocity of 1.2 m / s, and an average residence time of the spent catalyst of 2.1 minutes.

[0054] The product distribution is shown in Table 2.

[0055] Example 2

[0056] The method for continuously producing ethylene and propylene by catalytic cracking is the same as in Example 1, except that the ratio of the volume flow rate of the first portion of the spent catalyst returned to the fluidized bed reactor to the volume flow rate of the spent catalyst entering the reactor receiver is 0.1, and the first portion of the spent catalyst is heated to 630℃ and then returned to the riser reactor. The catalytic cracking reaction conditions include: a reaction temperature of 670℃, a weight ratio of catalyst to oil of 10, a reaction time of 2.2 seconds, a reaction pressure of 0.2 MPa, and a weight ratio of water vapor to C4+ olefin raw material of 0.25. The product distribution is shown in Table 2.

[0057] Example 3

[0058] The method for continuously producing ethylene and propylene by catalytic cracking is the same as in Example 1, except that the ratio of the volume flow rate of the first portion of the spent catalyst returned to the fluidized bed reactor to the volume flow rate of the spent catalyst entering the reactor receiver is 0.5. The product distribution is shown in Table 2.

[0059] Example 4

[0060] The method for continuously producing ethylene and propylene by catalytic cracking is the same as that in Example 1, except that the volume fraction of butene in the raw material is 25% by weight, and the diene content is 0.1% by weight. The product distribution is shown in Table 2.

[0061] Example 5

[0062] The method for continuously producing ethylene and propylene by catalytic cracking is the same as that in Example 1, except that the C4 fraction is returned to the riser reactor as a raw material for further cracking. The product distribution is shown in Table 2.

[0063] Comparative Example 1

[0064] The method for continuously producing ethylene and propylene by catalytic cracking is the same as that in Example 1, except that all the spent catalyst in the reactor receiver is introduced into the regenerator for regeneration, and the temperature of the regenerated catalyst is 630°C. The product distribution is shown in Table 2.

[0065] Table 1 Properties of the catalytic cracking catalyst

[0066]

[0067] Table 2 Product distribution

[0068]

[0069]

[0070] According to the data in Table 1, comparing the data in Examples 1-5 with Comparative Example 1, it can be seen that using the method of the present disclosure, ethylene and propylene can be continuously produced, and the regeneration and decoking process can be flexibly adjusted, which helps to maintain the heat balance of the system and stabilize the yield of ethylene and propylene. By comparing the data in Examples 1 and 2, it can be seen that under the catalytic cracking reaction conditions of the present method, the effect of catalytic cracking reaction can be enhanced. By comparing the data in Examples 1 and 3, it can be seen that when the ratio of the volume flow rate of the first portion of spent catalyst returned to the fluidized bed reactor to the volume flow rate of the spent catalyst entering the reactor receiver is within the preferred range of 0.1-0.3 of the present disclosure, the yield of ethylene and propylene can be further improved. By comparing the data in Examples 4 and 5, it can be seen that using the raw material provided by the present method, the backfiring of the cracking product C4 fraction can increase the production of ethylene and propylene.

[0071] The preferred embodiments of the present disclosure are described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0072] It should be further noted that various specific technical features described in the above specific embodiments can be combined in any suitable manner, and the disclosure will not be repeated here for various possible combinations.

[0073] Furthermore, various different embodiments of the disclosure can also be combined with each other, as long as it does not violate the idea of the disclosure, it should also be considered as disclosed by the disclosure.

Claims

1. A process for the catalytic cracking continuous production of ethylene and propylene, characterized in that, The method comprises: contacting a carbon four and above olefin feedstock with a catalytic cracking catalyst in a fluidized bed reactor to carry out a catalytic cracking reaction to obtain a reaction material; and carrying out a first separation on the reaction material to obtain spent catalyst and a reaction oil gas containing ethylene and propylene; introducing the spent catalyst into a reactor receiver to return a first part of the spent catalyst in the reactor receiver to the fluidized bed reactor; introducing a second part of the spent catalyst into a regenerator to regenerate the spent catalyst, and then returning the regenerated catalyst to the fluidized bed reactor; the content of olefins in the carbon four and above olefin feedstock is 30% by weight or more; and the content of di-olefins in the carbon four and above olefin feedstock is 1% by weight or less; the ratio of the first part of the spent catalyst returned to the fluidized bed reactor to the volume flow rate of the spent catalyst entering the reactor receiver is 0.01-0.

5.

2. The method of claim 1, wherein, the carbon four and above olefin feedstock is from one or more of a refinery catalytic cracking unit, an ethylene plant steam cracking unit, a chemical plant etherification unit, an MTO unit and an MTP unit; and the olefins in the carbon four and above olefin feedstock are C4-C12 olefins.

3. The method of claim 2, wherein, the olefins in the carbon four and above olefin feedstock are C4-C6 olefins.

4. The method of claim 1, wherein, the content of olefins in the carbon four and above olefin feedstock is 40% by weight or more; and the content of di-olefins in the carbon four and above olefin feedstock is 0.5% by weight or less.

5. The method of claim 1, wherein, the ratio of the first part of the spent catalyst returned to the fluidized bed reactor to the volume flow rate of the spent catalyst entering the reactor receiver is 0.1-0.

3.

6. The method of claim 1, wherein, the fluidized bed reactor is selected from one or more of a riser reactor, a dense phase fluidized bed reactor, an upflowing conveying line and a downflowing conveying line.

7. The method of claim 1, wherein, the conditions of the catalytic cracking reaction include: a reaction temperature of 500-700℃, an oil gas residence time of 0.2-5 seconds, a reaction pressure of 0.1-1 MPa, and a catalyst / oil weight ratio of 4-50.

8. The method of claim 1, wherein, the fluidized bed reactor is a riser reactor; and the carbon four and above olefin feedstock is introduced into a lower part of the riser reactor. The method further comprises injecting steam into the riser reactor, and the weight ratio of the injected steam to the carbon four and above olefin feedstock is 0.1-1.

9. The method of claim 8, wherein, The weight ratio of the injected steam to the carbon four and above olefin feedstock is 0.1-0.

5.

10. The method of claim 1, wherein, The method further comprises separating ethylene, propylene and a C4 and above fraction from the reaction oil gas.

11. The method of claim 10, wherein, The method further comprises returning the C4 and above fraction to the fluidized bed reactor for further reaction.

12. The method of claim 1, wherein, The regeneration conditions in the regenerator include: a regeneration temperature of 600-750℃; a gas superficial linear velocity of 0.2-3 meters / second; and an average residence time of the spent catalyst of 0.5-3 minutes.

13. The method of claim 12, wherein, The regeneration conditions in the regenerator include: a regeneration temperature of 650-700℃; a gas superficial linear velocity of 0.5-2 meters / second; and an average residence time of the spent catalyst of 0.8-2 minutes.

14. The method of claim 1, wherein, The method further comprises heating the first part of the spent catalyst to 580℃ or above before returning the first part of the spent catalyst to the fluidized bed reactor.

15. The method of claim 1, wherein, The catalytic cracking catalyst comprises a molecular sieve, an inorganic oxide binder and a carrier. The content of the molecular sieve is 1-60% by weight, based on the total weight of the catalytic cracking catalyst; the content of the inorganic oxide binder is 5-99% by weight; the content of the carrier is 0-70% by weight; The molecular sieve is an MFI molecular sieve; the MFI structure molecular sieve is selected from a ZSM molecular sieve and / or a ZRP molecular sieve; the ZSM molecular sieve is selected from one or more of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48; The carrier is selected from one or more of kaolin, montmorillonite, diatomite, pisolitic clay stone, sepiolite, halloysite, hydrotalcite, bentonite and rectorite; The inorganic oxide binder is one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silicon aluminum.

16. The method of claim 15, wherein, The ZSM molecular sieve is a ZSM-5 molecular sieve.

17. The method according to claim 15 or 16, characterized in that, The MFI structure molecular sieve is an MFI structure molecular sieve modified by phosphorus and / or a transition metal, the transition metal being selected from one or more of iron, cobalt and nickel. The MFI structure molecular sieve is an MFI structure molecular sieve modified by phosphorus and / or a transition metal, the transition metal being selected from one or more of iron, cobalt and nickel.

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