A catalytic cracking process for the production of ethylene and propylene

Abstract

The present application relates to a kind of catalytic cracking method for preparing ethylene and propylene, which comprises the following steps: introducing catalytic cracking catalyst before reaction into reactor to contact with hydrocarbon oil raw material to carry out catalytic cracking reaction, then gas-solid separation is carried out, to obtain catalytic cracking catalyst after reaction and oil gas product.The temperature of the catalytic cracking catalyst before reaction is above 650 DEG C, and specific heat capacity is 1.1~2.5J / (g·K);The temperature difference between the catalytic cracking catalyst after reaction and the temperature of the catalytic cracking catalyst before reaction is 20~100 DEG C.By using catalytic cracking catalyst with high specific heat capacity, the present application effectively inhibits the problem of excessive temperature drop on the surface of catalyst during catalytic cracking reaction, weakens the influence of temperature drop on the cracking reaction process of light raw material, promotes the monomolecular cracking of raw material, improves the yield of ethylene and propylene in product, and promotes the efficient use of raw material.

Description

Technical Field

[0001] This invention belongs to the field of petroleum processing, specifically relating to a catalytic cracking method for producing ethylene and propylene. Background Technology

[0002] Low-carbon olefins are important petrochemical feedstocks. Common technologies for producing low-carbon olefins include steam cracking, catalytic cracking, olefin cracking, and methanol-to-olefins (MTO). The operation of a catalytic cracking unit involves a heat balance between periodic heating and heat extraction. During the catalytic cracking reaction, the coke deposited on the catalyst is burned in the regenerator to generate heat, which is carried by the regenerated catalyst to the reactor to heat the feedstock and provide the heat for the cracking reaction.

[0003] Catalytic cracking is a strongly endothermic process, with a conventional calorimetric reaction heat of approximately 180–300 kJ / kg feedstock. However, catalytic cracking technologies for producing low-carbon olefins, such as deep catalytic cracking (DCC) and catalytic thermal cracking (CPP), require even greater heat, reaching 600–800 kJ / kg feedstock. Smaller molecules in the feedstock typically result in a higher calorimetric reaction heat; for example, producing low-carbon olefins from naphtha or olefins with no more than 12 carbon atoms requires a higher calorimetric reaction heat. To meet the required calorimetric reaction heat, existing technologies typically increase the catalyst-to-oil ratio. However, a high catalyst-to-oil ratio usually leads to increased coke production and dry gas yield. In response, those skilled in the art have proposed replacing some conventional catalytic cracking catalysts with inert supports. For example, CN101580733A uses amorphous aluminum silicate, pulverized coal, and spent catalytic cracking catalyst as heat carriers; CN107868675A uses a mixture of silica, titanium oxide, and alumina as a heat carrier to partially replace the catalyst. There are also some methods that focus on meeting the overall heat requirements of catalytic cracking reactors. For example, US6558530 uses the method of gasifying the feedstock before injecting it into the reactor; US7572362 uses sand as a heat carrier to pre-treat the feedstock and then deliver it into the reactor.

[0004] In actual production, after the heat carried by the regenerated catalyst supplies the raw materials with heat of heating and reaction, its temperature drops below the optimal temperature required for the conversion of the raw materials. If the temperature of the spent catalyst is further increased, the temperature of the regenerated catalyst in the initial stage of reaction with the raw materials will be higher than the optimal temperature, increasing by-products. Summary of the Invention

[0005] The purpose of this invention is to improve the yield of ethylene and propylene in the catalytic cracking products of light feedstocks.

[0006] To achieve the above objectives, the present invention provides a catalytic cracking method for producing ethylene and propylene, the method comprising the following steps:

[0007] The pre-reaction catalytic cracking catalyst is introduced into the reactor and contacted with the hydrocarbon feedstock for catalytic cracking reaction, followed by gas-solid separation to obtain the post-reaction catalytic cracking catalyst and oil and gas products; the temperature of the pre-reaction catalytic cracking catalyst is above 650℃ and the specific heat capacity is 1.1~2.5J / (g·K); the temperature difference between the post-reaction catalytic cracking catalyst and the pre-reaction catalytic cracking catalyst is 20~100℃.

[0008] Optionally, the temperature of the catalytic cracking catalyst before the reaction is above 680°C and the specific heat capacity is 1.2 to 2.0 J / (g·K); the temperature difference between the catalytic cracking catalyst after the reaction and the temperature of the catalytic cracking catalyst before the reaction is 30 to 90°C.

[0009] Optionally, the conditions for the catalytic cracking reaction include: a reaction temperature of 580–800°C, preferably 600–720°C; a reaction pressure of 0.05–1 MPa, preferably 0.1–0.8 MPa; a reaction time of 0.1–80 s, preferably 0.5–70 s; and a mass ratio of the catalytic cracking catalyst to the feedstock of (3–180):1, preferably (10–150):1.

[0010] Optionally, the reaction stream after catalytic cracking in the reactor is rapidly cooled to below 530°C before gas-solid separation.

[0011] Optionally, the catalytic cracking catalyst comprises mesoporous zeolite, a support, and an additive component; the additive component is an inert inorganic compound; on a dry basis and based on the total weight of the catalytic cracking catalyst, the catalytic cracking catalyst comprises 1-50% by weight of mesoporous zeolite, 5-89% by weight of the additive component, and 10-70% by weight of the support; the mesoporous zeolite is selected from at least one of ZSM-5 series zeolite and ZRP zeolite; the support comprises clay and inorganic oxides; the clay is selected from at least one of kaolinite, hydrous kaolinite, montmorillonite, diatomaceous earth, soapstone, retardant, sepiolite, attapulgite, hydrotalcite, and bentonite; the inorganic oxide is selected from at least one of silica and alumina.

[0012] Optionally, the inert inorganic compound includes at least one of silicon dioxide, titanium dioxide, aluminum oxide, silicon carbide, aluminum nitride, boron nitride, boron oxide, manganese oxide, silicon nitride, and mullite.

[0013] Optionally, the preparation method of the catalytic cracking catalyst includes the following steps: mixing the support, mesoporous zeolite and auxiliary components evenly, spray drying, and calcining.

[0014] Optionally, the hydrocarbon feedstock is fed in the gas phase after heat exchange and gasification, and the feed temperature of the hydrocarbon feedstock is 100-400°C, preferably 150-300°C; the hydrocarbon feedstock is a C4-C8 olefin or a mixture containing C4-C8 olefins; the content of C4-C8 olefins in the mixture containing C4-C8 olefins is 50-100 wt%, preferably 80-100 wt%.

[0015] Optionally, the reactor is selected from one or a combination of two of the following: a riser, a fluidized bed with constant linear velocity, a fluidized bed with constant diameter, an upward conveyor line, and a downward conveyor line; the riser is a riser reactor with constant diameter or a fluidized bed reactor with variable diameter.

[0016] Optionally, the method further includes the steps of: regenerating the catalytic cracking catalyst after the reaction by coking to obtain a regenerated catalytic cracking catalyst; returning the regenerated catalytic cracking catalyst to the reactor after replenishing heat by fuel combustion; the coking regeneration of the catalytic cracking catalyst after the reaction is carried out in an oxygen-containing atmosphere, and the reaction temperature of the coking regeneration is 600-800°C; the oxygen content in the oxygen-containing atmosphere is not higher than 28% by volume.

[0017] Through the above technical solution, the present invention effectively suppresses the phenomenon of significant temperature drop on the catalyst surface during the catalytic cracking reaction by using a catalytic cracking catalyst with high specific heat capacity, weakens the impact of temperature drop on the cracking reaction process of light feedstock, promotes the single-molecule cracking of feedstock, improves the yield of ethylene and propylene in the products, and promotes the efficient utilization of feedstock.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a schematic diagram of the catalytic cracking process according to an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures

[0022] 1. Pipeline 2. Reactor 3. Pipeline

[0023] 4 pipelines, 5 pipelines, 6 pipelines

[0024] 7. Outlet section; 8. Settler; 9. Gas collection chamber

[0025] 10 Stripping section, 11 Pipeline, 12 Inclined pipe awaiting production

[0026] 13 Regenerator 14 Pipeline 15 Cyclone Separation System

[0027] 16 Pipeline 17 Energy Recovery System 18 Heat Extractor

[0028] 19 Regeneration Inclined Tubes; 20 Large Oil and Gas Pipelines; 21 Product Fractionation Unit Detailed Implementation

[0029] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0030] In the process of producing low-carbon olefins from low-carbon olefins and / or alkanes, the catalyst temperature drops significantly during the reaction due to the lack of an external heating source in the catalytic cracking reactor, thus reducing the yield of the target product. Through experimentation, the inventors discovered that the decrease in target product yield is due to the catalyst temperature reduction affecting the cracking mechanism of the feedstock. Furthermore, they found that inhibiting or delaying the catalyst temperature decrease can promote the selective cracking of feedstock molecules, thereby increasing the yield of ethylene and propylene in the products. Therefore, the present invention is proposed.

[0031] This invention provides a catalytic cracking method for producing ethylene and propylene, the method comprising the following steps:

[0032] The pre-reaction catalytic cracking catalyst is introduced into the reactor and contacted with the hydrocarbon feedstock for catalytic cracking reaction, followed by gas-solid separation to obtain the post-reaction catalytic cracking catalyst and oil and gas products; the temperature of the pre-reaction catalytic cracking catalyst is above 650℃ and the specific heat capacity is 1.1~2.5J / (g·K); the temperature difference between the post-reaction catalytic cracking catalyst and the pre-reaction catalytic cracking catalyst is 20~100℃.

[0033] This invention effectively suppresses the significant temperature drop during the catalytic cracking reaction by employing a catalytic cracking catalyst with high specific heat capacity, thereby reducing the impact of temperature drop on the cracking process of light feedstocks, promoting the unimolecular cracking of feedstocks, increasing the yield of ethylene and propylene in the products, and promoting the efficient utilization of feedstocks.

[0034] The temperature of the catalytic cracking catalyst before the reaction is above 680℃, and the specific heat capacity is 1.2 to 2.0 J / (g·K).

[0035] In a specific embodiment of the present invention, the temperature difference between the catalytic cracking catalyst after the reaction and the catalytic cracking catalyst before the reaction can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C or any value within the aforementioned range.

[0036] Preferably, the temperature difference between the catalytic cracking catalyst after the reaction and the catalytic cracking catalyst before the reaction is 30–90°C.

[0037] The present invention uses the above-mentioned catalytic cracking catalyst, which can reduce the amount of catalytic cracking catalyst used while meeting the overall heat requirements of the reaction system, thereby reducing costs. It can also avoid the phenomenon of increased coke and dry gas yield under high catalyst-to-oil ratio conditions, which is conducive to improving the utilization rate of petrochemical products.

[0038] The catalytic cracking reaction conditions include: a reaction temperature of 580–800℃, preferably 600–720℃; a reaction pressure of 0.05–1 MPa, preferably 0.1–0.8 MPa; a reaction time of 0.1–80 s, preferably 0.5–70 s; and a mass ratio of the catalytic cracking catalyst to the feedstock of (3–180):1, preferably (10–150):1. By adopting the above reaction conditions, the cracking reaction of light feedstock can be ensured to proceed smoothly. By using a catalytic cracking catalyst with high specific heat capacity, high catalyst-to-oil ratio reaction conditions can be avoided, thereby preventing an increase in the yield of coke and dry gas in the products.

[0039] It should be noted that the above reaction conditions can be adjusted depending on the type of reactor.

[0040] In this invention, the hydrocarbon feedstock is gasified via heat exchange and then fed into the gas phase. The feed temperature of the hydrocarbon feedstock is 100–400°C, preferably 150–300°C. Preheating the hydrocarbon feedstock to a suitable reaction temperature and feeding it into the gas phase promotes the unimolecular cracking of light feedstocks. Before performing gas-solid separation on the reaction stream after the catalytic cracking reaction in the reactor, the reaction stream is rapidly cooled to below 530°C. It should be noted that in this invention, "rapid cooling" refers to cooling to the target temperature within 2 seconds or even less.

[0041] The catalytic cracking catalyst comprises mesoporous zeolite, a support, and an auxiliary component; the auxiliary component is an inert inorganic compound.

[0042] In a specific embodiment of the present invention, on a dry basis and based on the total weight of the catalytic cracking catalyst, the catalytic cracking catalyst comprises 1-50% by weight of mesoporous zeolite, 5-89% by weight of auxiliary components, and 10-70% by weight of support; the mesoporous zeolite is selected from at least one of ZSM-5 series zeolite and ZRP zeolite; the support comprises clay and inorganic oxides; the clay is selected from at least one of kaolinite, hydrous kaolinite, montmorillonite, diatomite, soapstone, retardant, sepiolite, attapulgite, hydrotalcite, and bentonite; the inorganic oxide is selected from at least one of silicon dioxide and aluminum oxide.

[0043] In this invention, the active component of the catalytic cracking catalyst is mixed with an inert inorganic compound with high specific heat capacity and then formed. The inert inorganic compound is evenly distributed, which is more conducive to heat conduction. The active component of the catalytic cracking catalyst is mesoporous zeolite, while other components have lower activity and will not adversely affect the catalytic cracking reaction of light feedstocks.

[0044] The inert inorganic compound includes at least one of silicon dioxide, titanium dioxide, aluminum oxide, silicon carbide, aluminum nitride, boron nitride, boron oxide, manganese oxide, silicon nitride, and mullite. By selecting the above-mentioned inert inorganic compounds with high specific heat capacity, the greater heat demand of low-carbon-number feedstock catalytic cracking reactions can be met, the phenomenon of a significant drop in the temperature of the catalytic cracking catalyst can be significantly suppressed, the selective cracking of feedstock molecules can be promoted, and thus the yields of ethylene and propylene can be improved.

[0045] The preparation method of the catalytic cracking catalyst includes the following steps: mixing the support, mesoporous zeolite, and auxiliary components evenly, spray drying, and calcining. For example, in a specific embodiment of the present invention, a certain amount of kaolin, boehmite, and hydrochloric acid can be mixed evenly, aged, and then a certain amount of inert inorganic compound with high specific heat capacity and zeolite can be added. After stirring the slurry evenly, it is spray dried to obtain the catalytic cracking catalyst.

[0046] The hydrocarbon feedstock is a C4-C8 olefin or a mixture containing C4-C8 olefins; the C4-C8 olefin content in the mixture is 50-100 wt%, preferably 80-100 wt%. Particularly preferably, the hydrocarbon feedstock is pure olefin. It should be noted that C4-C8 olefins refer to olefins with 4 to 8 carbon atoms.

[0047] The reactor is selected from one or a combination of two of the following: a riser, a fluidized bed with constant linear velocity, a fluidized bed with constant diameter, an upward conveyor line, and a downward conveyor line; the riser is a riser reactor with constant diameter or a fluidized bed reactor with variable diameter.

[0048] In specific embodiments, the aforementioned catalytic cracking catalyst with high specific heat capacity can be added to the reaction zone as needed. For example, the reactor is a variable-diameter fluidized bed reactor, including a first reaction zone and a second reaction zone. In specific implementations, the catalytic cracking catalyst can be introduced into the first reaction zone or the second reaction zone, or introduced into the first reaction zone and the second reaction zone respectively, depending on the situation. The mass ratio of catalyst to inert inorganic compound can also be adjusted as needed to enhance the catalytic cracking catalyst's ability to provide heat for the reaction and reduce the temperature drop during the reaction.

[0049] The method further includes the steps of: regenerating the catalytic cracking catalyst after the reaction by coking to obtain a regenerated catalytic cracking catalyst; returning the regenerated catalytic cracking catalyst to the reactor after replenishing heat by fuel combustion; the coking regeneration of the catalytic cracking catalyst after the reaction is carried out in an oxygen-containing atmosphere, and the reaction temperature of the coking regeneration is 600-800℃; the oxygen content in the oxygen-containing atmosphere is not higher than 28% by volume.

[0050] Figure 1 A schematic flow diagram of a catalytic cracking method provided by the present invention is shown below. Figure 1 As shown, the pre-lifting medium is introduced into reactor 2 via pipeline 1. The pre-catalytic cracking catalyst from the regeneration inclined tube 19 rises under the action of the pre-lifting medium. Preheated and gasified hydrocarbon feedstock from pipeline 3 and atomized steam from pipeline 4 are injected into the lower part of reactor 2, contacting the pre-catalytic cracking catalyst to undergo a catalytic cracking reaction and moving upwards along reactor 2. The reacted oil and gas products and the reacted catalytic cracking catalyst enter the cyclone separator of settling tank 8 through the outlet section 7 of reactor 2 to separate the reacted catalytic cracking catalyst and oil and gas products. The oil and gas products enter the gas collecting chamber 9, and the reacted oil and gas in the gas collecting chamber 9 enters the subsequent product fractionation unit 21 via the large oil and gas pipeline 20.

[0051] It should be noted that the oil and gas products and the catalytic cracking catalyst after the reaction are rapidly cooled to below 530°C by a heat exchange medium before leaving reactor 2.

[0052] After the reaction, the catalytic cracking catalyst is returned to the settling tank 8 via the feed leg and enters the stripping section 10. In the stripping section 10, the stripping medium introduced via pipeline 11 strips the adsorbed reaction oil and gas, and then enters the regenerator 13 through the regeneration inclined tube 12 to contact the oxygen-containing gas from pipeline 14 to burn off the coke it is loaded with. The coked regenerated catalyst and flue gas enter the cyclone separator 15 for separation. The separated flue gas enters the flue gas energy recovery system 17 via pipeline 16 to recover energy. The regenerated catalyst returns to the bottom of the regenerator 13 and is replenished with heat by the heat exchanger 18 before returning to the reactor 2 via the regeneration inclined tube 19.

[0053] In another embodiment of the present invention, the reactor is a variable diameter fluidized bed reactor. For example, reactor 2 includes a first reaction zone I and a second reaction zone II. Hot regeneration catalyst can be introduced into the reactor through the side of the first reaction zone or the second reaction zone. For example, hot regeneration catalyst from pipeline 5 enters the second reaction zone under the action of the medium from pipeline 6 and mixes with the catalyst to supplement the heat of the reaction system.

[0054] The present invention is further described in detail below through examples, but is not intended to limit the scope of the invention in any way. All raw materials used in the examples are commercially available. Specifically, the raw material used in the examples and comparative examples is 1-hexene.

[0055] ZRP-1 molecular sieve was produced by the catalyst plant of Qilu Petrochemical Company, with SiO2 / Al2O3 = 30 and rare earth content RE2O3 = 2.0% by weight.

[0056] Watery kaolin is an industrial product produced by Suzhou Porcelain Clay Company, with a solid content of 71.6% by weight.

[0057] Boehmite is an industrial product of Shandong Aluminum Plant, with a solid content of 63% by weight.

[0058] The aluminum sol was produced by the catalyst plant of Qilu Petrochemical Company, with an Al2O3 content of 21.7% by weight.

[0059] Example 1

[0060] This embodiment prepares catalytic cracking catalyst D1, and the preparation method includes the following steps:

[0061] (1) Preparation of mesoporous molecular sieves with MFI structure

[0062] S1. Weigh 20g of NH4Cl and dissolve it in 1000g of water. Then add 100g (dry basis) of crystallized ZRP-1 molecular sieve to the NH4Cl solution. After exchanging at 90℃ for 0.5 hours, filter to obtain filter cake.

[0063] S2. Weigh 4.0g of H3PO4 (concentration of 85% by weight) and 4.5g of Fe(NO3)3 and dissolve them in 90g of water to obtain a mixed solution containing phosphorus and iron.

[0064] S3. The filter cake was impregnated with the mixed solution containing phosphorus and iron, and then dried; subsequently, it was calcined at 550℃ for 2 hours to obtain a phosphorus and iron-containing MFI mesoporous molecular sieve. The elemental analysis chemical composition of the obtained molecular sieve is: 0.1Na2O·5.1Al2O3·2.4P2O5·1.5Fe2O3·3.8RE2O3·88.1SiO2.

[0065] (2) Weigh 75.4 kg of water-rich kaolin and slurry it with 250 kg of deionized water. Add 54.8 kg of pseudoboehmite and stir evenly. Adjust the pH to 2-4 with hydrochloric acid and let it stand at 60-70°C for 1 hour while maintaining the pH at 2-4. Then, lower the temperature of the slurry to below 60°C and add 41.5 kg of aluminum sol to the slurry. Stir for 40 minutes to obtain a mixed slurry.

[0066] (3) Add the phosphorus- and iron-containing MFI mesoporous molecular sieve (24.5 kg dry basis) prepared in step (1) to the mixed slurry obtained in step (2), stir evenly, spray dry to form, and wash away free Na with ammonium dihydrogen phosphate solution (phosphorus content 1% by weight). + After drying, the catalytic conversion catalyst D1 is obtained.

[0067] Based on the total dry weight of catalyst D1, the dry composition of the catalyst includes: 20% by weight of phosphorus and iron-containing MFI mesoporous molecular sieve, 28% by weight of pseudoboehmite and 8% by weight of aluminum sol, with the balance being kaolin.

[0068] Example 2

[0069] The method for preparing the catalytic cracking catalyst C1 in this embodiment is the same as in Example 1, except that:

[0070] In step (3), the phosphorus- and iron-containing MFI mesoporous molecular sieve (24.5 kg dry basis) and inert inorganic compound prepared in step (1) are added to the mixed slurry obtained in step (2), stirred evenly, spray-dried and shaped, and free Na is washed away with ammonium dihydrogen phosphate solution (phosphorus content 1% by weight). + After drying, the catalytic conversion catalyst C1 is obtained. The chemical composition of the inert inorganic compound includes: 30% manganese oxide, 15% aluminum oxide, 5% titanium dioxide, 10% boron oxide, and 40% silicon dioxide.

[0071] Based on the total dry weight of catalyst C1, the dry composition of the catalyst includes: 17 wt% phosphorus and iron-containing MFI mesoporous molecular sieve, 15 wt% pseudoboehmite, 8 wt% aluminum sol and 16 wt% inert inorganic compounds, with the balance being kaolin.

[0072] Example 3

[0073] The method for preparing the catalytic cracking catalyst C2 in this embodiment is the same as in Example 1, except that:

[0074] In step (3), the phosphorus- and iron-containing MFI mesoporous molecular sieve (24.5 kg dry basis) and inert inorganic compound prepared in step (1) are added to the mixed slurry obtained in step (2), stirred evenly, spray-dried and shaped, and free Na is washed away with ammonium dihydrogen phosphate solution (phosphorus content 1% by weight). + After drying, the catalytic conversion catalyst C2 is obtained. The chemical composition of the inert inorganic compound includes: 30% manganese oxide, 15% aluminum oxide, 5% titanium dioxide, 10% boron oxide, and 40% silicon dioxide.

[0075] Based on the total dry weight of catalyst C2, the dry composition of the catalyst includes: 14 wt% phosphorus and iron-containing MFI mesoporous molecular sieve, 10 wt% pseudoboehmite, 8 wt% aluminum sol and 24 wt% inert inorganic compounds, with the balance being kaolin.

[0076] Example 4

[0077] The experiment in this embodiment is... Figure 1 The process illustrated is carried out in a riser reactor medium-sized unit. 1-Hexene and high-temperature catalytic cracking catalyst C1 are contacted in the riser reactor to undergo catalytic cracking. The post-reaction stream and the post-reaction catalytic cracking catalyst are cooled and then enter a cyclone separator for gas-solid separation. The separated reaction oil and gas are then introduced into a subsequent product fractionation unit. The post-reaction catalyst is introduced into a regenerator for coke burn-off regeneration and then returned to the riser reactor to continue participating in the reaction. The reaction conditions and product distribution are shown in Table 1.

[0078] Example 5

[0079] The experiment in this embodiment follows... Figure 1 The process shown is the same as in Example 4, except that the catalyst used is C2, which was prepared in Example 3. The reaction conditions and product distribution are shown in Table 1.

[0080] Comparative Example 1

[0081] The experiment of Comparative Example 1 was conducted according to Figure 1 The process shown is the same as in Example 4, except that the catalyst used is catalyst D1 prepared in Example 1. The reaction conditions and product distribution are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] As shown in Table 1, the method of the present invention for the catalytic cracking of light feedstocks to prepare low-carbon olefins significantly suppresses the temperature drop during the catalytic cracking reaction due to the use of a high specific heat capacity catalytic cracking catalyst. This weakens the impact of temperature drop on the cracking reaction of light feedstocks, enhances the single-molecule cracking of feedstocks, improves the yield of ethylene and propylene, and promotes the efficient utilization of feedstocks.

[0086] At the same time, the method provided by this invention can reduce the amount of catalytic cracking catalyst while meeting the overall heat requirements of the reaction system. On the one hand, it can reduce costs, and on the other hand, it can avoid the increase in coke and dry gas yield caused by high catalyst-to-oil ratio conditions, thereby improving the utilization rate of petrochemical resources.

[0087] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0088] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0089] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A catalytic cracking method for producing ethylene and propylene, characterized in that, The method includes the following steps: The pre-reaction catalytic cracking catalyst is introduced into the reactor and contacted with the hydrocarbon feedstock for catalytic cracking reaction, followed by gas-solid separation to obtain the post-reaction catalytic cracking catalyst and oil and gas products; the temperature of the pre-reaction catalytic cracking catalyst is above 650℃ and the specific heat capacity is 1.1~2.5 J / (g·K); the temperature difference between the post-reaction catalytic cracking catalyst and the pre-reaction catalytic cracking catalyst is 20~100℃; On a dry basis and based on the total weight of the catalytic cracking catalyst, the catalytic cracking catalyst comprises 1-50% by weight of mesoporous zeolite, 5-89% by weight of promoter components, and 10-70% by weight of support; the promoter components are inert inorganic compounds; the inert inorganic compounds include at least one selected from silicon dioxide, titanium dioxide, alumina, silicon carbide, aluminum nitride, boron nitride, boron oxide, manganese oxide, silicon nitride, and mullite; The hydrocarbon feedstock is a C4-C8 olefin or a mixture containing C4-C8 olefins; The C4-C8 olefin content in the mixture is 50-100 wt%.

2. The catalytic cracking method according to claim 1, wherein, The temperature of the catalytic cracking catalyst before the reaction is above 680℃, and the specific heat capacity is 1.2~2.0 J / (g·K); The temperature difference between the catalytic cracking catalyst after the reaction and the catalytic cracking catalyst before the reaction is 30~90 °C.

3. The catalytic cracking method according to claim 1, wherein, The conditions for the catalytic cracking reaction include: a reaction temperature of 580~800 ℃; The reaction pressure is 0.05~1 MPa; The reaction time is 0.1~80s; The mass ratio of the catalytic cracking catalyst to the feedstock is (3~180):

1.

4. The catalytic cracking method according to claim 3, wherein, The conditions for the catalytic cracking reaction include: a reaction temperature of 600~720 ℃; The reaction pressure is 0.1~0.8 MPa; The reaction time is 0.5~70 s; The mass ratio of the catalytic cracking catalyst to the feedstock is (10~150):

1.

5. The catalytic cracking method according to claim 1, wherein, Before performing gas-solid separation on the reaction stream after catalytic cracking in the reactor, the reaction stream is rapidly cooled to below 530°C.

6. The catalytic cracking method according to claim 1, wherein, The mesoporous zeolite is selected from at least one of the ZSM-5 series zeolites and ZRP zeolites; The carrier includes clay and inorganic oxides; The clay is selected from at least one of kaolin, hydrous kaolin, montmorillonite, diatomite, soapstone, rettoite, sepiolite, attapulgite, hydrotalcite, and bentonite. The inorganic oxide is selected from at least one of silicon dioxide and aluminum oxide.

7. The catalytic cracking method according to claim 6, wherein, The preparation method of the catalytic cracking catalyst includes the following steps: mixing the support, mesoporous zeolite and auxiliary components evenly, spray drying, and calcining.

8. The catalytic cracking method according to claim 1, wherein, The hydrocarbon oil feedstock is fed in the gas phase after being heat-exchanged and vaporized, and the feed temperature of the hydrocarbon oil feedstock is 100~400 ℃; The C4-C8 olefin content in the mixture is 80-100 wt%.

9. The catalytic cracking method according to claim 8, wherein, The feed temperature of the hydrocarbon oil feedstock is 150~300℃.

10. The catalytic cracking method according to claim 1, wherein, The reactor is selected from one or a combination of two of the following: riser, constant linear velocity fluidized bed, constant diameter fluidized bed, upward conveyor line, and downward conveyor line. The riser is either a constant diameter riser reactor or a variable diameter fluidized bed reactor.

11. The catalytic cracking method according to claim 1, wherein, The method further includes the following steps: The catalytic cracking catalyst after the reaction is regenerated by coking to obtain a regenerated catalytic cracking catalyst; the regenerated catalytic cracking catalyst is returned to the reactor after being replenished with heat by fuel combustion; The coke regeneration of the catalytic cracking catalyst after the reaction is carried out in an oxygen-containing atmosphere, and the reaction temperature of the coke regeneration is 600~800 ℃; the oxygen content in the oxygen-containing atmosphere is not higher than 28% by volume.

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