A process for the production of ethylene and propylene by catalytic cracking of light hydrocarbons

Abstract

The present disclosure relates to a method for preparing ethylene and propylene by catalytic cracking of light hydrocarbon, a mixture of high-temperature heat carrier and catalytic cracking catalyst is flowed into a riser reactor to contact with light hydrocarbon raw material to carry out catalytic cracking reaction; a product mixture obtained by the reaction is subjected to gas-solid separation to obtain a solid stream and a gas stream containing ethylene and propylene; the solid stream is introduced into a separator to separate to obtain spent heat carrier and spent catalyst; the generated spent heat carrier is introduced into a first regenerator to carry out coke-burning regeneration to obtain the high-temperature heat carrier; the spent catalyst is introduced into a second regenerator to carry out coke-burning regeneration to obtain regenerated catalyst; and the high-temperature heat carrier and the regenerated catalyst are returned to the riser reactor to continue the reaction. By using the method of the present disclosure, the heat of the reaction-regeneration system can be balanced; the service life of the catalyst can be prolonged; the reaction conversion rate of the light hydrocarbon and the yield of ethylene and propylene can be improved.

Description

TECHNICAL FIELD

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

[0002] Ethylene and propylene are important organic chemical raw materials. Tubular furnace steam cracking is a traditional technology for producing ethylene and propylene, but its reaction temperature is as high as 800℃, energy consumption accounts for 40% of the entire petroleum chemical industry, and the yield ratio of propylene to ethylene is low. Catalytic cracking, by introducing an acidic catalyst, not only reduces the reaction temperature, but also helps to improve the product distribution, and has attracted great attention.

[0003] US10550333 discloses a method for producing ethylene and propylene from naphtha, using Ti or alkaline earth metal modified, and then P modified HZSM-5 molecular sieve. Under the evaluation conditions of a reaction temperature of 650℃, a weight ratio of water vapor to naphtha of 0.5, a mass space velocity of 6.1h -1 -1, and a distillation range of 48.3-88.4℃, the light naphtha is contacted with the catalyst to react, and the yield of ethylene and propylene is higher than 45%.

[0004] CN102531821A discloses a method for catalytic cracking reaction of methanol coupling naphtha using a modified ZSM-5 molecular sieve catalyst. The modified ZSM-5 molecular sieve catalyst contains 2.2-6.0 wt% of lanthanum and 1.0-2.8 wt% of phosphorus. Naphtha and methanol pass through the catalyst bed at the same time, under the conditions of a reaction temperature of 550-670℃, a mass ratio of methanol to naphtha of 0.05-0.8, and a total mass space velocity of naphtha and methanol of 1.0-5h -1 -1. The ethylene and propylene yield of the method is higher than 35%.

[0005] From the existing disclosed methods, it can be seen that the reaction performance of light hydrocarbon catalytic cracking is low, and in order to improve the reaction conversion rate, a higher reaction temperature is required. The coke yield of light hydrocarbon catalytic cracking is low, which cannot meet the heat demand of the heat balance fluidized bed reaction regeneration system, which becomes the main factor restricting the industrial application of naphtha catalytic cracking.

[0006] CN102746873A discloses a method for preparing ethylene and propylene by catalytic cracking of light hydrocarbon. The preheated raw material enters an inner-embedded riser reactor, and is contacted with the catalyst at a temperature of 570-720℃ to generate a low-carbon olefin product. Using FCC light gasoline as the raw material, the ethylene and propylene yield is 15.13% and 25.61% respectively at a reaction temperature of 700℃. The technology embeds the main reaction zone of the riser reactor inside the regenerator, which has difficulty in industrial implementation.

[0007] The prior art cannot effectively solve the contradiction between high reaction temperature and insufficient heat supply for coking regeneration in the process of catalytic cracking of light hydrocarbons. SUMMARY

[0008] The purpose of the present disclosure is to develop a method for producing ethylene and propylene by catalytic cracking of light hydrocarbons, to solve the heat balance problem of the reaction regeneration system, and to improve the reaction performance of light hydrocarbons and the yield of low-carbon olefins.

[0009] To achieve the above-mentioned purpose, the present disclosure provides a method for producing ethylene and propylene by catalytic cracking of light hydrocarbons, which comprises: flowing a mixture of high-temperature heat carriers and catalytic cracking catalyst into a riser reactor to contact with light hydrocarbon raw materials to carry out catalytic cracking reaction; carrying out gas-solid separation on the product mixture obtained by reaction to obtain a solid stream and a gas stream containing ethylene and propylene; introducing the solid stream into a separator to separate to obtain spent heat carriers and spent catalyst; wherein the separator utilizes the difference in average particle size of the spent heat carriers and the spent catalyst to separate; introducing the spent heat carriers into a first regenerator for coking regeneration to obtain the high-temperature heat carriers; introducing the spent catalyst into a second regenerator for coking regeneration to obtain regenerated catalyst; returning the high-temperature heat carriers and the regenerated catalyst to the riser reactor for continuous reaction.

[0010] Optionally, the heat carrier is a porous microspherical inorganic substance; the heat carrier is selected from one or more of silica sand, alumina, aluminum silicate, calcium silicate, magnesium silicate, magnesium-aluminum spinel and pseudo-boehmite.

[0011] Optionally, the average particle size of the heat carrier is 100-300 μm.

[0012] Optionally, the catalytic cracking catalyst contains 15-65 wt% of natural mineral, 10-30 wt% of oxide and 25-75 wt% of zeolite, the zeolite being one of ZSM molecular sieve, ZRP molecular sieve, Y molecular sieve, USY molecular sieve, β molecular sieve, SAPO-34 molecular sieve and MOR molecular sieve, or being a composite molecular sieve formed by at least two of them; preferably being a molecular sieve modified by phosphorus, non-metallic elements and optional transition metal elements; the transition metal elements including one or more of iron, cobalt and nickel; the natural mineral including one or more of kaolin, montmorillonite, diatomite, pachnodyctite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite; the oxide being one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silicon-aluminum.

[0013] Optionally, the average particle size of the catalytic cracking catalyst is 50-90 μm.

[0014] Optionally, the weight ratio of the heat carrier to the catalytic cracking catalyst is 0.1-2.

[0015] Optionally, the high-temperature heat carrier obtained from the first regenerator has a temperature of 650-1000℃; optionally, the method further comprises supplementing a combustion medium into the first regenerator, the combustion medium comprising fuel oil and / or fuel gas.

[0016] Optionally, the light hydrocarbon feedstock has a final boiling point of 220℃ or lower, preferably, the light hydrocarbon feedstock is selected from one or more of mixed C4, topped oil, raffinate oil, straight-run naphtha, catalytic cracking gasoline, catalytic cracking gasoline, coking gasoline, thermal cracking gasoline, and hydrocracking naphtha.

[0017] Optionally, the regenerated catalyst obtained from the second regenerator has a temperature of 600-750℃, preferably 630-720℃.

[0018] Optionally, the catalytic cracking reaction has a reaction temperature of 550-750℃, an oil gas residence time of 0.2-5 seconds, a reaction pressure of 0.1-1 MPa, a weight ratio of catalyst to oil of 4-50, and a weight ratio of water to oil of 0.1-1.

[0019] By the above technical solution, the method of the present disclosure uses high-temperature heat carriers as heat transfer media, and the mixture of heat carriers and catalysts can provide sufficient heat for the reaction system, thereby balancing the heat of the reaction and regeneration systems, solving the contradiction between high reaction temperature and insufficient heat supply for regeneration and coking in the light hydrocarbon riser catalytic cracking process; coking and regeneration of the catalytic cracking catalyst under conventional conditions can avoid catalyst deactivation under high-temperature hydrothermal conditions, thereby improving the service life of the catalyst; at the same time, the method can also improve the reaction conversion rate of light hydrocarbons, thereby increasing the yield of ethylene and propylene.

[0020] Other features and advantages of the present disclosure will be described in detail in the following detailed description section. BRIEF DESCRIPTION OF DRAWINGS

[0021] 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 detailed description, serve to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0022] Figure 1 is a flow diagram of one specific embodiment of the method for producing ethylene and propylene by catalytic cracking of light hydrocarbons provided by the present disclosure.

[0023] LEGEND OF THE DRAWINGS

[0024] 1, riser reactor; 2, settler; 3, disengager; 4, first regenerator; 5, second regenerator; 6, pre-lift medium; 7, atomized steam; 8, light hydrocarbon feedstock; 9, cyclone; 10, head chamber; 11, gaseous stream; 12, settler stripping section; 13, solid stream; 14, spent hot carrier; 15, spent catalyst; 16, first regenerator cyclone; 17, second regenerator cyclone; 18, mixture stream of regenerated catalyst and high-temperature hot carrier. DETAILED DESCRIPTION

[0025] 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 merely intended to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0026] The present disclosure provides a method for preparing ethylene and propylene by catalytic cracking of light hydrocarbon, which comprises: contacting a mixture stream of high-temperature hot carrier and catalytic cracking catalyst with light hydrocarbon feedstock in a riser reactor to perform catalytic cracking reaction; performing gas-solid separation on the product mixture obtained by the reaction to obtain a solid stream and a gaseous stream containing ethylene and propylene; separating the solid stream in a disengager to obtain spent hot carrier and spent catalyst; wherein the disengager separates the spent hot carrier and the spent catalyst by virtue of the difference in average particle size; feeding the spent hot carrier into a first regenerator for coking regeneration to obtain the high-temperature hot carrier; feeding the spent catalyst into a second regenerator for coking regeneration to obtain regenerated catalyst; and returning the high-temperature hot carrier and the regenerated catalyst to the riser reactor for continuous reaction.

[0027] By the above technical solution, the method of the present disclosure uses high-temperature hot carrier as heat transfer medium, and the mixture stream of hot carrier and catalyst can provide sufficient heat for the reaction system, thereby balancing the heat of the reaction regeneration system; coking regeneration of the catalytic cracking catalyst under conventional conditions can avoid deactivation of the catalyst under high-temperature hydrothermal conditions, thereby improving the service life of the catalyst; at the same time, the method can also improve the reaction conversion rate of light hydrocarbon, thereby increasing the yield of ethylene and propylene.

[0028] In one embodiment, the hot carrier is a porous microspherical inorganic substance; the hot carrier is selected from one or more of silica sand, alumina, aluminum silicate, calcium silicate, magnesium silicate, magnesium-aluminum spinel and pseudo-boehmite. Further, the BET specific surface area of the hot carrier can be 300-1000 m 2 / g, preferably 320-800 m 2 / g.

[0029] In this embodiment, the heat carrier has good hydrothermal stability and will not decompose at 1000°C, and has high heat transfer capacity, so that the heat of the reaction-regeneration system can be further balanced by selecting the heat carrier.

[0030] In one embodiment, the average particle size of the heat carrier is 100-300 μm, preferably 120-200 μm.

[0031] In one embodiment, the weight ratio of the heat carrier to the catalytic cracking catalyst is 0.1-2, preferably 0.2-1. Within the above preferred weight ratio range, the heat of the reaction-regeneration system can be further balanced and the product distribution can be optimized.

[0032] In the method of the present disclosure, the separator separates the heat carrier from the catalytic cracking catalyst by virtue of the difference in particle size, and in one embodiment, the separator is one or more of a centrifugal settler, a cyclone separator and a gravity settler.

[0033] In one embodiment, the catalytic cracking catalyst contains 15-65 wt% of a natural mineral, 10-30 wt% of an oxide and 25-75 wt% of a zeolite, the zeolite being one of ZSM molecular sieve, ZRP molecular sieve, Y molecular sieve, USY molecular sieve, β molecular sieve, SAPO-34 molecular sieve and MOR molecular sieve, or being a composite molecular sieve formed by at least two of them; the zeolite is preferably a molecular sieve modified by phosphorus, a non-metallic element and optionally a transition metal element; wherein the transition metal element includes one or more of iron, cobalt and nickel.

[0034] In one embodiment, the ZRP molecular sieve is selected from ZRP molecular sieves prepared by conventional methods in the art, and can also be selected from commercially available ZRP molecular sieves; the ZSM molecular sieve is selected from a mixture of one or more of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48 and other similar structure molecular sieves; the ZSM-5 molecular sieve is also selected from ZSM-5 molecular sieves prepared by conventional methods in the art, and can also be selected from commercially available ZSM-5 molecular sieves.

[0035] In one embodiment, the natural mineral includes one or more of kaolin, montmorillonite, diatomite, pisolite, sepiolite, halloysite, hydrotalcite, bentonite and rectorite.

[0036] In one embodiment, the oxide is one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide and amorphous silicon aluminum.

[0037] According to a preferred embodiment of the present application, the average particle size of the catalytic cracking catalyst is 50-90 μm, preferably 60-85 μm; and the proportion of the catalytic cracking catalyst having a particle size of 40-105 μm in the total weight of the catalytic cracking catalyst is more than 60% by weight.

[0038] In the above embodiment, the activity of the catalytic cracking catalyst can be enhanced by selecting the conditions of the catalytic cracking catalyst; and in order to further enhance the activity of the catalyst, the composition, content and average particle size of the catalytic cracking catalyst are preferably selected.

[0039] In one embodiment, the catalytic cracking reaction conditions include: the reaction temperature is 550-750°C, preferably 580-720°C, and more preferably 600-700°C; the residence time of the oil gas is 0.2-5 seconds, preferably 1-4 seconds; the reaction pressure is 0.1-1 MPa, preferably 0.1-0.5 MPa; the weight ratio of the agent to the oil is 4-50, preferably 8-40; and the weight ratio of the water to the oil is 0.1-1, preferably 0.2-0.6.

[0040] In the above embodiment, 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.

[0041] Optionally, the light hydrocarbon feedstock is introduced into the lower part of the riser reactor. The riser reactor comprises, from bottom to top, a pre-lifting section and at least one reaction zone.

[0042] In one embodiment, the high-temperature heat carrier obtained from the first regenerator has a temperature of 650-1000°C, preferably 700-900°C; and the method further comprises: supplementing a combustion medium into the first regenerator; the combustion medium comprises fuel oil and / or fuel gas; the fuel oil is selected from one or more of gasoline, diesel, reformed oil, oil slurry and heavy oil; and the fuel gas is selected from one or more of dry gas, gas, natural gas and C1-C4 mixed gas.

[0043] In one embodiment, the regeneration process of the spent catalyst can be carried out according to the conventional catalyst regeneration method in the art, for example: introducing an oxygen-containing gas (such as air) into the bottom of the regenerator, and the spent catalyst is regenerated by contact with oxygen; the generated flue gas is subjected to gas-solid separation by a cyclone separator of the regenerator, and then enters a subsequent energy recovery system. The regeneration conditions of the spent catalyst (i.e. the operating conditions of the second regenerator) can be: the regeneration temperature is 600-750°C, preferably 630-720°C; the apparent linear velocity of the gas is 0.2-3 meters / second, preferably 0.5-2 meters / second; and the average residence time of the spent catalyst is 0.5-3 minutes, preferably 0.8-2 minutes.

[0044] In one embodiment, the light hydrocarbon feedstock is a mixture of hydrocarbons having an end point of less than 220°C.

[0045] In this embodiment, the light hydrocarbon feedstock has a carbon number distribution range of C4 to C12, and can be selected from one or more of a mixture of C4, a draw-off oil, a raffinate oil, a straight-run naphtha, a catalytic cracking gasoline, a catalytic cracking gasoline, a coking gasoline, a thermal cracking gasoline, and a hydrocracking naphtha.

[0046] In one embodiment, the light hydrocarbon feedstock is preheated to a temperature of 200 to 450°C, preferably 300 to 420°C. The present application can introduce the entire light hydrocarbon feedstock into the reactor at one feed location, or can introduce the light hydrocarbon feedstock into the reactor at at least two different feed locations.

[0047] In one embodiment, as shown in Fig. 1, the method for producing ethylene and propylene by catalytic cracking of a light hydrocarbon feedstock includes: Figure 1

[0048] The pre-lift medium 6 is introduced into the bottom of the riser reactor 1 via a pipe line, and the mixture stream 18 of regenerated catalyst and high-temperature heat carrier moves upward along the riser reactor 1 under the lifting action of the pre-lift medium 6. The preheated light hydrocarbon feedstock 8 is injected into the riser reactor 1 via a pipe line together with the atomization medium 7, and is contacted with the fluidized mixture stream 18 of regenerated catalyst and high-temperature heat carrier to undergo a catalytic cracking reaction, and the generated reaction products and the carbon-containing catalyst and heat carrier enter the cyclone separator 9 in the settler 2, the reaction products enter the gas collection chamber 10, and then the gas stream 11 enters a subsequent separation system to be separated to obtain ethylene and propylene. The spent solid stream in the settler 2 enters the stripping section 12, the stripped solid stream 13 enters the separator 3, and the separation of the catalyst and the heat carrier is realized according to the difference in particle size between the two; the spent heat carrier 14 enters the first regenerator 4, and supplemental combustion oil and / or combustion gas are burned to burn off the coke on the heat carrier under the action of air, and the gas-solid stream is separated via the first regenerator cyclone separator 16; the spent catalyst 15 enters the second regenerator 5 via a pipe line, and air is used to burn off the coke on the spent catalyst in the dense bed layer to regenerate the spent catalyst, and the gas-solid stream is separated via the second regenerator cyclone separator 17; the regenerated heat carrier is fully mixed with the regenerant to increase the temperature of the regenerant, and then the mixture stream 18 of regenerated catalyst and high-temperature heat carrier is returned to the riser reactor 1.

[0049] The following examples will further illustrate the present application, but are not intended to limit the present application.

[0050] The reagents used in the following examples are all of chemical purity, unless otherwise specified. The light hydrocarbon feedstocks used in the examples are light naphtha and straight-run naphtha, and their properties are listed in Table 1.

[0051] Example 1​

[0052] The heat carrier is alumina porous microspheres (commercially available), and the catalytic cracking catalyst is ZRP molecular sieve catalyst, which is purchased from Qilu Branch of Sinopec Catalyst Co., Ltd. The properties of both are listed in Table 2.

[0053] The mixture stream of regenerated catalyst and high-temperature heat carrier is accelerated upward along the riser reactor under the lifting action of the pre-lifting medium, and light naphtha preheated to 400°C is injected into the riser reactor together with atomized medium steam to contact the fluidized mixture stream of regenerated catalyst and high-temperature heat carrier to occur catalytic cracking reaction. The generated reaction products and spent catalyst with carbon and heat carrier enter the cyclone separator in the settler, the reaction products enter the gas collection chamber, and then the gas stream enters the subsequent separation system to obtain ethylene and propylene. The spent solid stream in the settler enters the stripping section, and the stripped solid stream enters the gravity settling separator to realize separation of the catalyst and heat carrier according to the particle size difference; the spent heat carrier enters the first regenerator, and supplemental combustion oil and / or combustion gas are added to burn off the coke on the heat carrier under the action of air, and the gas-solid stream is separated by the cyclone separator of the first regenerator. The temperature of the regenerated heat carrier is 760°C, and the weight ratio of heat carrier to catalytic cracking catalyst is 0.2. The spent catalyst enters the second regenerator through the pipeline, and air is used to burn off the coke on the spent catalyst in the dense bed to regenerate the deactivated spent catalyst, and the gas-solid is separated by the cyclone separator. The temperature of the regenerated catalyst is 660°C; the regenerated heat carrier and the regenerated catalyst are fully mixed to increase the temperature of the regenerated catalyst, and then the mixture stream of regenerated catalyst and high-temperature heat carrier is returned to the riser reactor.

[0054] The operating conditions and product distribution are shown in Table 3.

[0055] The calculation method of light hydrocarbon conversion rate is the mass of converted light hydrocarbon divided by the mass of light hydrocarbon participating in the reaction multiplied by 100%; the test of catalyst micro-reaction activity is carried out on the standard cracking catalyst micro-activity tester according to the standard method RIPP92-90.

[0056] Example 2

[0057] The method for preparing ethylene and propylene by catalytic cracking of light hydrocarbons is the same as in Example 1, except that the reaction raw material is straight-run naphtha (properties are listed in Table 2), the temperature of the regenerated heat carrier is 790°C, and the weight ratio of heat carrier to catalytic cracking catalyst is 0.3. The operating conditions and product distribution are shown in Table 3.

[0058] Example 3

[0059] The process for the catalytic cracking of light hydrocarbons to ethylene and propylene is the same as in Example 1, except that the weight ratio of heat carrier to catalytic cracking catalyst is 3. The operating conditions and product distribution are shown in Table 3.

[0060] Example 4

[0061] The process for the catalytic cracking of light hydrocarbons to ethylene and propylene is the same as in Example 1, except that the temperature of the heat carrier after regeneration is 630°C. The operating conditions and product distribution are shown in Table 3.

[0062] Example 5

[0063] The process for the catalytic cracking of light hydrocarbons to ethylene and propylene is the same as in Example 1, except that heat carrier B, which is a pseudoboehmite (commercially available), is used. The operating conditions and product distribution are shown in Table 3.

[0064] Comparative Example 1

[0065] The process for the catalytic cracking of light hydrocarbons to ethylene and propylene is the same as in Example 1, except that no heat carrier is used, and the spent catalyst obtained from the gas-solid separation is fed into the second regenerator for regeneration. The operating conditions and product distribution are shown in Table 3.

[0066] Comparative Example 2

[0067] The process for the catalytic cracking of light hydrocarbons to ethylene and propylene is the same as in Example 1, except that the spent heat carrier is not fed into the first regenerator, and the solid stream obtained from the gas-solid separation is directly fed into the second regenerator for regeneration. The operating conditions and product distribution are shown in Table 3.

[0068] Comparative Example 3

[0069] The process for the catalytic cracking of light hydrocarbons to ethylene and propylene is the same as in Example 1, except that the spent catalyst is not fed into the second regenerator, and the solid stream obtained from the gas-solid separation is directly fed into the first regenerator for regeneration. The operating conditions and product distribution are shown in Table 3.

[0070] Table 1 Properties of the light hydrocarbon feedstock

[0071]

[0072]

[0073] Table 2 Properties of the heat carrier and catalytic cracking catalyst

[0074]

[0075] Table 3 Operating conditions and product distribution

[0076]

[0077]

[0078] According to the data in Table 3, the data comparison of Examples 1-5 and Comparative Examples 1-3 shows that, by using the method of the present disclosure and taking high-temperature heat carrier as heat transfer medium, the heat of the reaction-regeneration system can be balanced, the reaction conversion rate of light hydrocarbon and the yield of ethylene and propylene can be increased, and the catalyst and the heat carrier can be regenerated separately, which can avoid the deactivation of the catalyst under high-temperature hydrothermal conditions. According to the data comparison of Example 1 and Example 3, when the weight ratio of the heat carrier to the catalytic cracking catalyst is in the preferred range of 0.1-2, the heat of the reaction-regeneration system can be further balanced, and the yield of low-carbon olefins is higher. According to the data comparison of Example 1, Example 4 and Example 5, the use of the preferred heat carrier of the present disclosure helps to enhance the catalytic cracking reaction performance of light hydrocarbon.

[0079] The preferred embodiments of the present disclosure are described in detail above in combination with the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0080] In addition, it should be noted that each specific technical feature described in the above-described specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0081] In addition, various different embodiments of the present disclosure can also be combined in any appropriate manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed by the present disclosure.

Claims

1. A method for producing ethylene and propylene by catalytic cracking of light hydrocarbons, characterized in that, The method includes: A mixture of a high-temperature heat carrier and a catalytic cracking catalyst is flowed into a riser reactor and brought into contact with light hydrocarbon feedstock to carry out a catalytic cracking reaction. The product mixture obtained from the reaction is subjected to gas-solid separation to obtain a solid stream and a gas stream containing ethylene and propylene; the solid stream is then fed into a separator to obtain a heat transfer medium and a catalyst to be generated; wherein the separator utilizes the difference in average particle size between the heat transfer medium and the catalyst to perform separation. The heat carrier to be generated is sent to the first regenerator for coking and regeneration to obtain the high-temperature heat carrier; the catalyst to be generated is sent to the second regenerator for coking and regeneration to obtain the regenerated catalyst; the high-temperature heat carrier and the regenerated catalyst are returned to the riser reactor to continue the reaction. The average particle size of the catalytic cracking catalyst is 50–90 μm; the average particle size of the heat carrier is 100–300 μm. The weight ratio of the heat carrier to the catalytic cracking catalyst is 0.1 to 2.

2. The method according to claim 1, characterized in that, The heat carrier is a porous microsphere-shaped inorganic material; the heat carrier is selected from one or more of silica sand, alumina, aluminum silicate, calcium silicate, magnesium silicate, magnesium aluminum spinel and pseudoboehmite.

3. The method according to claim 1, characterized in that, The catalytic cracking catalyst contains 15-65% by weight of natural minerals, 10-30% by weight of oxides and 25-75% by weight of zeolite. The zeolite is one of ZSM molecular sieve, ZRP molecular sieve, Y molecular sieve, USY molecular sieve, β molecular sieve, SAPO-34 molecular sieve and MOR molecular sieve, or a composite molecular sieve formed from at least two of them; The natural minerals mentioned include one or more of the following: kaolin, montmorillonite, diatomite, attapulgite, sepiolite, halloysite, hydrotalcite, bentonite, and rettoite. The oxide is one or more of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, and amorphous aluminum silicate.

4. The method according to claim 3, characterized in that, The zeolite is a molecular sieve modified with phosphorus, non-metallic elements and optional transition metal elements; the transition metal elements include one or more of iron, cobalt and nickel.

5. The method according to claim 1, characterized in that, The temperature of the high-temperature heat transfer fluid obtained from the first regenerator is 650–1000°C.

6. The method according to claim 5, characterized in that, The method further includes: replenishing the first regenerator with a combustion medium, the combustion medium including fuel oil and / or fuel gas.

7. The method according to claim 1, characterized in that, The final boiling point of the light hydrocarbon feedstock is below 220°C.

8. The method according to claim 7, characterized in that, The light hydrocarbon feedstock is selected from one or more of the following: mixed C4, topping oil, raffinate oil, straight-run naphtha, catalytic cracking gasoline, catalytic cracking gasoline, coking gasoline, thermal cracking gasoline, and hydrocracking naphtha.

9. The method according to claim 1, characterized in that, The temperature of the regenerated catalyst obtained from the second regenerator is 600–750°C.

10. The method according to claim 9, characterized in that, The temperature of the regenerated catalyst obtained from the second regenerator is 630–720°C.

11. The method according to claim 1, characterized in that, The conditions for the catalytic cracking reaction include: a reaction temperature of 550–750°C, an oil-gas residence time of 0.2–5 seconds, a reaction pressure of 0.1–1 MPa, an agent-to-oil weight ratio of 4–50, and a water-to-oil weight ratio of 0.1–1.

Images