Process for the production of low carbon olefins from catalytic cracking c4s

Abstract

This invention discloses a method for producing low-carbon olefins from catalytic cracking C4, comprising: gasifying catalytic cracking C4 in a gasifier, wherein the gasifier outlet temperature is 60-65°C and the pressure is set to 0.5-0.8 MPa to ensure that the catalytic cracking C4 is in a gasified state; and then replacing the pre-lifted dry gas with the gasified catalytic cracking C4, which enters the catalyst reactor riser from the bottom pre-lift section to contact the catalyst and react. This invention improves the catalyst particle size distribution, increases reaction efficiency, avoids excessive coking inside the riser, saves energy, and allows for continuous operation.

Description

Technical Field

[0001] This invention relates to a method for producing low-carbon olefins by catalytic cracking of C4. More specifically, this invention relates to a method for producing low-carbon olefins by catalytic cracking of C4. Background Technology

[0002] my country's petrochemical industry produces approximately 40 million tons / year of catalytic cracking C4, primarily for the production of MTBE and alkylated gasoline, with a small amount used for civilian liquefied petroleum gas (LPG). MTBE is mainly used as a gasoline blending component, with a total capacity of approximately 23 million tons / year, while alkylated gasoline has a total capacity of approximately 22 million tons / year. Existing catalytic cracking units employ dry gas extraction and catalyst dispersion, where the dry gas acts as an inert medium and does not participate in the reaction. During catalytic cracking, low-temperature dry gas is separated from the high-temperature reaction zone and reused in the subsequent stabilization absorption system, resulting in energy waste. Using steam extraction of the catalyst requires the separation of liquid water from the subsequent separation system, also leading to energy waste. How to produce low-carbon olefins through the reprocessing of catalytic cracking C4 and reduce system energy consumption is a pressing technical challenge. Summary of the Invention

[0003] This invention provides a method for producing low-carbon olefins by catalytic cracking of C4, which improves the catalyst particle size distribution, increases reaction efficiency, avoids excessive coking on the inside of the riser, saves energy, and allows for continuous operation.

[0004] To achieve these objectives and other advantages according to the present invention, a method for producing low-carbon olefins by catalytic cracking of C4 is provided, comprising: gasifying catalytic cracking C4 in a gasifier, wherein the outlet temperature of the gasifier is 60-65°C and the pressure is set to 0.5-0.8 MPa to ensure that the catalytic cracking C4 is in a gasified state; and replacing the pre-lifted dry gas with the gasified catalytic cracking C4, which enters the catalyst reactor riser pipe from the bottom pre-lift section to contact the catalyst and react.

[0005] Preferably, the catalyst reactor is a single riser reactor, and the reaction conditions are a temperature of 650-750℃, a pressure of 0.13-0.2MPa, a residence time of 1-8s, and a catalyst-to-oil ratio of 5-20:1.

[0006] Preferably, the catalyst reactor is a dual-riser reactor, in which the gasified catalytic cracking C4 is divided into two feed streams. The first feed stream accounts for 50-100% of the total feed and replaces the pre-riser dry gas. It enters the bottom pre-riser section of the first riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 650-750℃, pressure 0.13-0.2MPa, residence time 1-8s, and catalyst-to-oil ratio 5-20:1. The second feed stream replaces the pre-riser steam and enters the bottom steam stripping section of the second riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 530-650℃, pressure 0.13-0.2MPa, residence time 2-10s, and catalyst-to-oil ratio 5-30:1.

[0007] Preferably, the catalyst reactor is a dual-riser reactor, in which the gasified catalytic cracking C4 is divided into two feed streams. The first feed stream accounts for 50-100% of the total feed and replaces the pre-riser dry gas as it enters the bottom pre-riser section of the first riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 650-750℃, pressure 0.13-0.2MPa, residence time 1-8s, and catalyst-to-oil ratio 5-20:1. The second feed stream enters the dense-phase bed reaction zone after entering the top of the second riser of the catalytic reactor. The reaction conditions are: temperature 510-630℃, pressure 0.13-0.2MPa, reaction time approximately 10-40min, and catalyst-to-oil ratio 5-30:1.

[0008] Preferably, the catalyst reactor is a dual-riseer reactor, in which the gasified catalytic cracking C4 is divided into three feed streams. The first feed stream accounts for 50-100% of the total feed and replaces the pre-riseer dry gas as it enters the bottom pre-riseer section of the first riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 650-750℃, pressure 0.13-0.2MPa, residence time 1-8s, and catalyst-to-oil ratio 5-20:1. The second feed stream accounts for no more than 20% of the total feed and replaces the pre-riseer steam as it enters the catalyst. The catalyst reacts in contact with the steam stripping section at the bottom of the second riser of the catalytic reactor. The reaction conditions are: temperature 530–650℃, pressure 0.13–0.2MPa, residence time 2–10s, and catalyst-to-oil ratio 5–30:1. The feed amount of the third stream does not exceed 40% of the total feed. After entering the top of the second riser of the catalytic reactor, it enters the dense phase bed reaction zone. The reaction conditions are: temperature 510–630℃, pressure 0.13–0.2MPa, reaction time approximately 10–40min, and catalyst-to-oil ratio 5–30:1.

[0009] Preferably, the catalytic cracking C4 includes conventional catalytic cracking C4 and catalytic pyrolysis C4.

[0010] Preferably, the catalyst includes a catalytic cracking catalyst, a catalytic pyrolysis catalyst, and an additive that produces more propylene, with a specific surface area of ​​70–200 m². 2 / g, pore volume 0.18~0.26mL / g, average particle size between 40~80μm, pyrolysis activity index between 50~75%.

[0011] Preferably, the low-carbon olefins include ethylene and propylene.

[0012] The present invention has at least the following beneficial effects:

[0013] First, this invention is based on a single riser reactor. Replacing the pre-riser dry gas with the gasified C4 from catalytic cracking can improve catalyst distribution, save the use of inert medium dry gas, utilize the highest temperature range of oil-gas contact to convert C4 components, improve reaction efficiency, avoid a large amount of coking inside the riser, save energy, and enable continuous operation.

[0014] Secondly, the present invention is based on a dual riser reactor, which gasifies catalytic cracking C4 and feeds it in two streams. The first stream replaces the pre-riser dry gas, which not only improves the catalyst distribution and saves the use of inert medium dry gas, but also replaces the pre-riser steam, which can save steam and thus save energy. The high-temperature reaction zone at the bottom of the second riser is used to convert C4 components.

[0015] Third, this invention is based on a dual riser reactor. After the catalytic cracking C4 is gasified, it is fed into two streams. The first stream replaces the pre-lifted dry gas. In addition to improving the catalyst distribution and saving the use of inert medium dry gas, the second stream enters the dense phase bed reaction zone after entering the top of the second riser of the catalytic reactor. It can also take advantage of the long residence time in the dense phase bed reaction zone to convert the catalytic cracking C4 into low carbon olefins.

[0016] Fourth, this invention is based on a dual-riser reactor. After the catalytic cracking C4 is gasified, it is fed in three streams. The first stream replaces the pre-riser dry gas, which not only improves the catalyst distribution and saves the use of inert medium dry gas, but also replaces the pre-riser steam, which can save steam and thus save energy. The high-temperature reaction zone at the bottom of the second riser is used to convert C4 components. The third stream enters the dense phase bed reaction zone after entering the top of the second riser of the catalytic reactor. It can also take advantage of the long residence time in the dense phase bed reaction zone to convert catalytic cracking C4 into low-carbon olefins.

[0017] Fifth, the C4 gasification process of this invention, after entering the reaction system, can avoid sudden temperature drops and coking inside the reactor, which would affect its long-term operation and conversion efficiency. It can reduce the material and energy consumption of dry gas and steam, improve the conversion efficiency of C4 components, and extend the operating cycle. It can be modified on existing conventional catalytic cracking and catalytic pyrolysis equipment.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the three-pronged feeding process of the present invention. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0021] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0022] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are conventional methods, and the reagents and materials mentioned are commercially available. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "setting" should be interpreted broadly. For example, they can refer to fixed connection or setting, detachable connection or setting, or integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The terms "lateral," "longitudinal," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0023] <Example 1>

[0024] Step 1: Conventional catalytic cracking C4 is gasified in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60°C and the pressure is 0.5 MPa. The composition of catalytic cracking C4 is shown in Table 1.

[0025] Step 2: Divide the gasified catalytic cracking C4 into three feed streams:

[0026] The first feed stream, accounting for 50% of the total feed, replaces the pre-lifted dry gas and enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 2s, catalyst-to-oil ratio 8:1, and catalyst characteristics: specific surface area 90 μm. 2 / g, pore volume 0.19mL / g, average particle size 55μm, pyrolysis activity index 55%.

[0027] The second feed stream, comprising 20% ​​of the total feed, replaces the pre-lift steam and enters the bottom stripping section of the second riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 550℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and the catalyst has a specific surface area of ​​90 μm. 2 / g, pore volume 0.19mL / g, average particle size 55μm, pyrolysis activity index 55%.

[0028] The third feed stream, accounting for 30% of the total feed, enters the dense-phase bed reaction zone after passing through the top of the second riser of the catalytic reactor. It contacts the catalyst, and the reaction conditions are: temperature 520℃, pressure 0.14MPa, reaction time approximately 30 min, catalyst-to-oil ratio 20:1, and catalyst characteristics: specific surface area 90 μm. 2 / g, pore volume 0.19mL / g, average particle size 55μm, pyrolysis activity index 55%.

[0029] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0030] <Example 2>

[0031] Step 1: Conventional catalytic cracking C4 is gasified in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60°C and the pressure is 0.5 MPa. The composition of catalytic cracking C4 is shown in Table 1.

[0032] Step 2: Divide the gasified catalytic cracking C4 into three feed streams:

[0033] The first feed stream, accounting for 50% of the total feed, replaces the pre-lifted dry gas and enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 2s, catalyst-to-oil ratio 8:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0034] The second feed stream, comprising 20% ​​of the total feed, replaces the pre-lift steam and enters the bottom stripping section of the second riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 550℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0035] The third feed stream, accounting for 30% of the total feed, enters the dense-phase bed reaction zone after passing through the top of the second riser of the catalytic reactor. It contacts the catalyst, and the reaction conditions are: temperature 520℃, pressure 0.14 MPa, reaction time approximately 30 min, catalyst-to-oil ratio 20:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0036] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0037] <Example 3>

[0038] Step 1: The catalytic cracked C4 is vaporized in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60℃ and the pressure is 0.5 MPa. The composition of the catalytic cracked C4 is shown in Table 1.

[0039] Step 2: Divide the gasified catalytic cracked C4 into three feed streams.

[0040] The first feed stream, accounting for 50% of the total feed, replaces the pre-lifted dry gas and enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 2s, catalyst-to-oil ratio 8:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0041] The second feed stream, comprising 20% ​​of the total feed, replaces the pre-lift steam and enters the bottom stripping section of the second riser in the catalytic reactor. There, it contacts the catalyst and reacts under the following conditions: temperature 550℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1. The catalyst has the following characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0042] The third feed stream, accounting for 30% of the total feed, enters the dense-phase bed reaction zone after passing through the top of the second riser of the catalytic reactor. The reaction conditions are: temperature 520℃, pressure 0.14MPa, reaction time approximately 30 min, catalyst-to-oil ratio 20:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0043] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0044] <Example 4>

[0045] Step 1: The catalytic cracked C4 is vaporized in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60℃ and the pressure is 0.5 MPa. The composition of the catalytic cracked C4 is shown in Table 1.

[0046] Step 2: Divide the gasified catalytic cracked C4 into three feed streams.

[0047] The first feed stream, accounting for 50% of the total feed, replaces the pre-lifted dry gas and enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0048] The second feed stream, comprising 20% ​​of the total feed, replaces the pre-lift steam and enters the bottom stripping section of the second riser in the catalytic reactor. There, it contacts the catalyst and reacts under the following conditions: temperature 635℃, pressure 0.14MPa, residence time 6s, catalyst-to-oil ratio 20:1. The catalyst has the following characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0049] The third feed stream, accounting for 30% of the total feed, enters the dense-phase bed reaction zone after entering the top of the second riser of the catalytic reactor, where it contacts the catalyst. The reaction conditions are: temperature 560℃, pressure 0.14MPa, reaction time approximately 30 min, catalyst-to-oil ratio 25:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0050] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0051] <Example 5>

[0052] Step 1: The catalytic cracked C4 is vaporized in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60℃ and the pressure is 0.5 MPa. The composition of the catalytic cracked C4 is shown in Table 1.

[0053] Step 2: Divide the gasified catalytic cracked C4 into three feed streams.

[0054] The first feed stream, accounting for 80% of the total feed, replaces the pre-lifted dry gas and enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0055] The second feed stream, comprising 10% of the total feed, replaces the pre-lift steam and enters the bottom stripping section of the second riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 635℃, pressure 0.14MPa, residence time 6s, catalyst-to-oil ratio 20:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0056] The third feed stream, accounting for 10% of the total feed, enters the dense-phase bed reaction zone after passing through the top of the second riser of the catalytic reactor. The reaction conditions are: temperature 560℃, pressure 0.14 MPa, reaction time approximately 30 min, catalyst-to-oil ratio 25:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0057] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0058] <Example 6>

[0059] Step 1: The catalytic cracked C4 is vaporized in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60℃ and the pressure is 0.5 MPa. The composition of the catalytic cracked C4 is shown in Table 1.

[0060] Step 2: All the gasified catalytically cracked C4 is fed into the first reaction zone, replacing the pre-lifted dry gas. It enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0061] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0062] <Example 7>

[0063] Step 1: The catalytic cracked C4 is vaporized in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60℃ and the pressure is 0.5 MPa. The composition of the catalytic cracked C4 is shown in Table 1.

[0064] Step 2: Divide the gasified catalytic cracked C4 into two feed streams.

[0065] The first feed stream, accounting for 80% of the total feed, replaces the pre-lifted dry gas and enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0066] The second feed stream, comprising 20% ​​of the total feed, replaces the pre-lift steam and enters the bottom stripping section of the second riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 635℃, pressure 0.14MPa, residence time 6s, catalyst-to-oil ratio 20:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0067] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0068] <Example 8>

[0069] Step 1: The catalytic cracked C4 is vaporized in a gasifier. The heating medium of the gasifier is steam at 0.4-1 MPa. The outlet temperature of the gasifier is 60℃ and the pressure is 0.5 MPa. The composition of the catalytic cracked C4 is shown in Table 1.

[0070] Step 2: Divide the gasified catalytic cracked C4 into two feed streams.

[0071] The first feed stream, accounting for 80% of the total feed, replaces the pre-lifted dry gas and enters the bottom pre-lift section of the first riser in the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 700℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and catalyst characteristics: specific surface area 115 μm. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0072] The second feed stream, accounting for 20% of the total feed, enters the third reaction zone through the top of the second riser of the catalytic reactor. The reaction conditions are: temperature 560℃, pressure 0.14MPa, residence time 30min, catalyst-to-oil ratio 25:1, and catalyst characteristics: specific surface area 115m². 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0073] Step 3: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, mixed aromatic hydrocarbons, and other products. Sustainable production is possible.

[0074] <Comparative Example 1>

[0075] Step 1: Conventional catalytic cracking C4 (composition of catalytic cracking C4 is shown in Table 1) is directly mixed with fresh feedstock and introduced into the upper reaction zone of the pre-lift section of the first riser reactor through the feedstock nozzle. The reaction conditions are: temperature 550℃, pressure 0.14MPa, residence time 2s, catalyst-to-oil ratio 8:1, and catalyst characteristics: specific surface area 90m². 2 / g, pore volume 0.19mL / g, average particle size 55μm, pyrolysis activity index 55%.

[0076] Step 2: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, and mixed aromatic hydrocarbons. Production must be stopped after a 6-month operating cycle.

[0077] <Comparative Example 2>

[0078] Step 1: The catalytically cracked C4 (composition of catalytically cracked C4 is shown in Table 1) is directly mixed with fresh feedstock and introduced into the upper reaction zone of the pre-lift section of the first riser reactor through the feedstock nozzle. The reaction conditions are: temperature 550℃, pressure 0.14MPa, residence time 4s, catalyst-to-oil ratio 15:1, and catalyst characteristics: specific surface area 115m. 2 / g, pore volume 0.21mL / g, average particle size 60μm, cleavage activity index 62%.

[0079] Step 2: After passing through a settling tank, the reaction products enter a gas separation system to separate ethylene, propylene, dry gas, mixed C4 hydrocarbons, and mixed aromatic hydrocarbons. Production must be stopped after a 6-month operating cycle.

[0080] Table 1

[0081]

[0082] Material accounting was performed on Examples 1-8 and Comparative Examples 1-2. The raw material C4 was 100%, and the product component content is shown in Table 2. Among them, diene yield refers to the proportion of ethylene + propylene in the raw material, the total conversion rate is equal to 100 - the mixed C4 yield in the product, and the olefin conversion rate is the total conversion rate / the weight fraction of olefins in the raw material.

[0083] Table 2

[0084]

[0085]

[0086] As shown in Table 2, Example 1 is a conventional catalytic cracking of C4, with a diene yield of 20.10%, an overall conversion of 28.68%, and an olefin conversion of 62.35%.

[0087] Example 2 is a conventional catalytic cracking of C4, with a diene yield of 21.74%, an overall conversion of 30.77%, and an olefin conversion of 66.89%. Compared to Example 1, the olefin conversion increases with the improvement of catalyst activity.

[0088] Example 3 involved catalytic cracking of C4, with a diene yield of 31.68%, an overall conversion rate of 43.61%, and an olefin conversion rate of 67.09%. Compared to Example 2, this example showed a higher olefin content and increased diene yield, while maintaining a roughly equivalent olefin conversion rate.

[0089] Example 4 is a catalytic cracking of C4. Compared with Example 3, the reaction temperature, reactant-to-oil ratio and reaction time are higher, and the conversion rate is higher (higher reaction temperature means faster reaction rate, and a larger reactant-to-oil ratio means a larger reaction contact area and more raw materials can participate in the reaction, the same below). The diene yield is 34.31%, the total conversion rate is 50.20%, and the olefin conversion rate is 77.23%.

[0090] Example 5 is a catalytic cracking of C4. Compared with Example 4, the proportion of feedstock entering the first reaction zone is increased from 50% to 80%. Due to the high temperature in the first reaction zone, the feedstock is converted quickly in the first reaction zone, and the conversion rate is improved. The diene yield is 39.09%, the total conversion rate is 57.45%, and the olefin conversion rate is 88.38%.

[0091] Example 6 involves catalytic cracking of C4. Compared to Example 4, all the gasified catalytic cracked C4 is fed into the first reaction zone instead of the pre-lifted dry gas. Due to the high temperature in the first reaction zone, the feedstock is converted quickly in the first reaction zone, and the conversion rate is improved. The diene yield is 37.52%, the total conversion rate is 57.60%, and the olefin conversion rate is 88.62%.

[0092] Example 7 involves catalytic cracking of C4. Compared to Example 6, 80% of the gasified catalytic cracked C4 is fed into the first reaction zone to replace the pre-lifted dry gas, and 20% of the catalytic cracked C4 is fed into the second reaction zone. Since the temperature in the second reaction zone is lower than that in the first reaction zone, the olefin conversion rate is reduced, the diene yield is 37.21%, the total conversion rate is 54.04%, and the olefin conversion rate is 83.14%.

[0093] Example 8 involved catalytic cracking of C4. Compared to Example 6, 80% of the gasified catalytic cracked C4 was fed into the first reaction zone to replace the pre-lifted dry gas, and 20% of the catalytic cracked C4 was fed into the third reaction zone. Since the temperature in the third reaction zone was lower than that in the first reaction zone but the reaction time was longer, the olefin conversion rate was slightly reduced, the diene yield was 39.73%, the total conversion rate was 57.08%, and the olefin conversion rate was 87.82%.

[0094] Comparative Example 1 uses conventional catalytic cracking C4. Compared to Example 1, the conventional catalytic cracking C4 is not gasified and is directly mixed with fresh feedstock and fed directly into the riser reactor through its nozzle. This causes the reaction temperature in the feed section of the reactor to drop rapidly, affecting the atomization effect of the feedstock nozzle and resulting in coking near the feed section, which affects long-cycle operation. At the same time, the reaction takes place in a low-temperature zone, resulting in a very low conversion rate. The diene yield is 9.94%, the total conversion rate is 16.81%, and the olefin conversion rate is 36.54%.

[0095] Comparative Example 2 involved catalytic cracking of C4. Compared to Example 1, the catalytic cracked C4 was not gasified and was directly mixed with fresh feedstock before entering the riser reactor through its nozzle. This caused the reaction temperature in the feed section of the reactor to drop rapidly, affecting the atomization effect of the feedstock nozzle and resulting in coking near the feed section, which affected long-cycle operation. At the same time, the reaction was carried out in the low-temperature zone, resulting in a very low conversion rate. The diene yield was 16.31%, the total conversion rate was 25.69%, and the olefin conversion rate was 39.52%.

[0096] In summary, the technical solution of the present invention includes the following steps: after the catalytic cracking C4 is gasified and enters the reaction system, 1) the catalytic cracking C4 replaces the pre-lifted dry gas and enters the pre-lifted section of the riser reactor for reaction; 2) the catalytic cracking C4 replaces the pre-lifted steam and enters the stripping section of the second reaction zone for reaction; 3) the catalytic cracking C4 enters the dense phase bed, i.e., the third reaction zone for reaction; and 4) the catalytic cracking C4 is integrated into multiple reaction zones.

[0097] The present invention has at least the following beneficial effects: First, the catalytic cracking C4 conversion process provided by the present invention can be operated continuously and for a long period of time; Second, the method for producing low-carbon olefins from catalytic cracking C4 provided by the present invention is easy to operate and can be extended to the modification of all catalytic cracking and catalytic pyrolysis units; Third, the present invention expands the method for the efficient conversion of catalytic cracking C4 to low-carbon olefins, adapts to all current catalytic cracking and catalytic pyrolysis catalyst systems, and does not require the development of a dedicated catalyst system; Fourth, it replaces pre-lifted dry gas and pre-lifted steam, saving energy consumption; Fifth, the catalytic cracking C4 conversion rate and diene yield are high.

[0098] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0099] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for producing low-carbon olefins by catalytic cracking of C4, characterized in that, include: The catalytic cracking C4 is gasified in a gasifier with an outlet temperature of 60~65℃ and a pressure of 0.5~0.8MPa to ensure that the catalytic cracking C4 is in a gasified state. The gasified catalytic cracking C4 is then introduced into the catalyst reactor to contact the catalyst and react. The low-carbon olefins include ethylene and propylene; The catalyst reactor is a dual-riser reactor. The gasified catalytic cracking C4 is divided into two feed streams. The first feed stream accounts for 50-100% of the total feed and replaces the pre-riser dry gas. It enters the bottom pre-riser section of the first riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 650-750℃, pressure 0.13-0.2 MPa, residence time 1-8 s, and catalyst-to-oil ratio 5-20:

1. The second feed stream replaces the pre-riser steam and enters the bottom steam stripping section of the second riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 530-650℃, pressure 0.13-0.2 MPa, residence time 2-10 s, and catalyst-to-oil ratio 5-30:

1. or The catalyst reactor is a dual-riser reactor. The gasified catalytic cracking C4 is divided into two feed streams. The first feed stream accounts for 50-100% of the total feed and replaces the pre-riser dry gas. It enters the bottom pre-riser section of the first riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 650-750℃, pressure 0.13-0.2 MPa, residence time 1-8 s, and catalyst-to-oil ratio 5-20:

1. The second feed stream enters the dense phase bed reaction zone after entering the top of the second riser of the catalytic reactor. The reaction conditions are: temperature 510-630℃, pressure 0.13-0.2 MPa, reaction time approximately 10-40 min, and catalyst-to-oil ratio 5-30:

1. or The catalyst reactor is a dual-riser reactor. The gasified catalytic cracking C4 is divided into three feed streams. The first stream, comprising 50-100% of the total feed, replaces the pre-riser dry gas and enters the bottom pre-riser section of the first riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 650-750℃, pressure 0.13-0.2 MPa, residence time 1-8 s, and catalyst-to-oil ratio 5-20:

1. The second stream, not exceeding 20% ​​of the total feed, replaces the pre-riser steam and enters the bottom steam stripping section of the second riser of the catalytic reactor to contact the catalyst and react. The reaction conditions are: temperature 530-650℃, pressure 0.13-0.2 MPa, residence time 2-10 s, and catalyst-to-oil ratio 5-30:

1. The third stream, not exceeding 40% of the total feed, enters the dense-phase bed reaction zone after entering the top of the second riser of the catalytic reactor. The reaction conditions are: temperature 510-630℃, pressure 0.13-0.2 MPa, and reaction time 0.2 MPa. MPa, reaction time approximately 10-40 min, agent-to-oil ratio 5-30:

1.

2. The method for producing low-carbon olefins by catalytic cracking of C4 as described in claim 1, characterized in that, The specific surface area of ​​the catalyst is 70~200m². 2 / g, pore volume 0.18~0.26 mL / g, average particle size between 40~80 µm, pyrolysis activity index between 50~75%.

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