A method for producing low-carbon olefins by catalytic cracking of light oil

Abstract

The present invention provides a method for producing light olefins by catalytic cracking of light oil. The method comprises preparing light olefins using light oil as a raw material and a heat storage catalyst as a catalyst; based on 100% dry basis of the heat storage catalyst, the catalyst contains at least the following components in weight percentage: 10%-50% molecular sieve, 10%-40% heat storage material, and 40%-80% carrier; the heat storage material has a thermal conductivity of 20-500 W / m·K and a specific heat capacity of 600-1200 J / kg·K. The present invention electrically heats the heat storage catalyst to supplement heat for the regenerator and provide energy for the cracking reaction, replacing the existing method of adding fuel oil or pulverized coal for supplementary heat. This avoids local overheating that causes structural deactivation of the catalyst, helps slow the rate of catalyst activity reduction, reduces catalyst consumption, and eliminates additional carbon emissions.

Description

Technical Field

[0001] The present invention relates to the field of petrochemical industry, and in particular to a method for preparing low-carbon olefins by catalytic cracking of light oil. Background Art

[0002] Existing catalytic cracking processes are widely used in the petrochemical industry. As market demand shifts, catalytic cracking processes are beginning to use light oils such as naphtha or diesel to crack and produce light olefins (such as ethylene, propylene, and butenes). Light olefins are the building blocks for the production of various polymers and other value-added chemicals, and are widely used in various chemical industries, including pharmaceuticals, food, and dyes. However, catalytic cracking is a highly endothermic reaction that requires high temperatures. However, the amount of coke produced by the light oil reaction is relatively low, resulting in insufficient heat within the regenerator, making it difficult to maintain the required high temperatures.

[0003] During the operation of traditional regenerators, the method of spraying fuel oil into the catalyst bed is often used to supplement heat through the self-ignition of the fuel oil. Although this method can provide a large amount of heat in a short period of time, the combustion of fuel oil on the catalyst surface will cause the local temperature of the catalyst surface to be too high, which in turn causes the catalyst pores to collapse and the particles to break, seriously affecting the service life and reaction efficiency of the catalyst. Secondly, the catalytic cracking reaction is a highly endothermic reaction. Due to the low thermal conductivity of the catalyst, there will be a significant temperature gradient on the bed, which reduces the utilization rate of the catalyst and increases the risk of carbon deposition in the reaction center. In order to ensure uniform temperature in the reactor, combustion needs to be maintained at extremely high temperatures to ensure sufficient inward heat flow. The maximum temperature of the reactor wall is 100-150°C higher than the temperature of the catalyst in the reactor, which results in significant energy waste.

[0004] To address this issue, patent CN100337736C introduces continuous or intermittent addition of pulverized coal with a particle size between 10 and 140 μm into the catalyst regenerator. This method saves significant amounts of light fuel oil, reduces equipment costs, and improves economic efficiency. However, pulverized coal is prone to blockage and uneven distribution during transportation, resulting in incomplete combustion. Combustion of pulverized coal also generates additional pollutants, complicating the flue gas treatment process. Furthermore, the resulting ash can adsorb onto the catalyst surface or accumulate within the regenerator, impacting operational efficiency and catalyst activity.

[0005] Patent CN115305107A discloses an external electric heater for regenerator heating in a fluidized bed light hydrocarbon processing unit. This device is designed to address issues such as insufficient regenerator reheating capacity in older units, inadequate flue gas treatment systems, or insufficient main fan power. This electric heater utilizes green electricity, significantly reducing carbon emissions and enabling more precise control of heating. However, this invention fails to fully consider the thermal conductivity and heat storage capacity of the catalyst, resulting in the catalyst still not achieving ideal operating conditions during the electrical heating process. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing light olefins by catalytic cracking of light oil.

[0007] To achieve the above-mentioned object, the present invention provides a method for preparing light olefins by catalytic cracking of light oil, wherein the method comprises preparing light olefins using light oil as a raw material and a heat storage catalyst as a catalyst;

[0008] Taking the dry basis of the thermal storage catalyst as 100%, the catalyst (final product) contains at least the following components in weight percentage: 10%-50% molecular sieve, 10%-40% thermal storage material, and 40%-80% carrier;

[0009] The thermal conductivity of the heat storage material is 20-500 W / m·K, and the specific heat capacity is 600-1200 J / kg·K.

[0010] According to some specific embodiments of the present invention, the heat storage material is selected from at least one of magnesium oxide, silicon carbide, aluminum nitride, silicon nitride and boron nitride.

[0011] According to some specific embodiments of the present invention, the thermal conductivity of magnesium oxide is 40-60 W / m·K, and the specific heat capacity is 1000 J / kg·K.

[0012] According to some specific embodiments of the present invention, the specific surface area of ​​magnesium oxide is 30 to 200 m 2 / g, specific pore volume 0.1~0.3cm 3 / g.

[0013] According to some specific embodiments of the present invention, the thermal conductivity of silicon carbide is 120-200 W / m·K, and the specific heat capacity is 750 J / kg·K.

[0014] According to some specific embodiments of the present invention, the specific surface area of ​​silicon carbide is 50 to 200 m 2 / g, specific pore volume 0.1~0.3cm 3 / g.

[0015] According to some specific embodiments of the present invention, the thermal conductivity of aluminum nitride is 140-180 W / m·K, and the specific heat capacity is 740 J / kg·K.

[0016] According to some specific embodiments of the present invention, the specific surface area of ​​aluminum nitride is 10 to 100 m 2 / g, specific pore volume 0.05~0.2cm 3 / g.

[0017] According to some specific embodiments of the present invention, the thermal conductivity of silicon nitride is 20-30 W / m·K, and the specific heat capacity is 700 J / kg·K.

[0018] According to some specific embodiments of the present invention, the specific surface area of ​​silicon nitride is 10 to 100 m 2 / g, specific pore volume 0.1~0.4cm 3 / g.

[0019] According to some specific embodiments of the present invention, the thermal conductivity of boron nitride is 200-400 W / m·K, and the specific heat capacity is 750 J / kg·K.

[0020] According to some specific embodiments of the present invention, the specific surface area of ​​boron nitride is 50 to 200 m 2 / g, specific pore volume 0.2~0.5cm 3 / g.

[0021] According to some specific embodiments of the present invention, the particle size of the thermal storage material is 100-200 mesh.

[0022] According to some specific embodiments of the present invention, the shape of the heat storage material is at least one of spherical, sheet-like or columnar.

[0023] According to some specific embodiments of the present invention, the carrier is SiO2 and / or Al2O3.

[0024] According to some specific embodiments of the present invention, SiO2 is derived from a silicon-containing binder and / or silicon-containing clay; Al2O3 is derived from an aluminum-containing binder and / or aluminum-containing clay.

[0025] The silicon-containing clay is selected from a combination of one or more of kaolin, sepiolite, attapulgite, rectorite, montmorillonite and diatomite; the aluminum-containing clay is selected from a combination of one or more of attapulgite, rectorite and montmorillonite;

[0026] The silicon-containing binder is selected from silica sol and / or sodium silicate-acid mixed slurry; the aluminum-containing binder is selected from pseudo-boehmite-acid mixed slurry and / or aluminum sol.

[0027] According to some specific embodiments of the present invention, the kaolin has a thermal conductivity of 0.25 to 0.35 W / m·K and a specific heat capacity of 920 J / kg·K.

[0028] According to some specific embodiments of the present invention, the kaolin has a specific surface area of ​​10 to 30 m 2 / g, specific pore volume 0.05~0.1cm 3 / g.

[0029] According to some specific embodiments of the present invention, the thermal conductivity of the sepiolite is 0.15-0.3 W / m·K, and the specific heat capacity is 900 J / kg·K.

[0030] According to some specific embodiments of the present invention, the sepiolite has a specific surface area of ​​200 to 400 m 2 / g, specific pore volume 0.3~0.5cm 3 / g.

[0031] According to some specific embodiments of the present invention, the attapulgite has a thermal conductivity of 0.1 to 0.2 W / m·K and a specific heat capacity of 850 J / kg·K.

[0032] According to some specific embodiments of the present invention, the attapulgite has a specific surface area of ​​125 to 200 m 2 / g, specific pore volume 0.2~0.4cm 3 / g.

[0033] According to some specific embodiments of the present invention, the thermal conductivity of the rectorite is 0.2-0.3 W / m·K, and the specific heat capacity is 800 J / kg·K.

[0034] According to some specific embodiments of the present invention, the specific surface area of ​​the rectorite is 250 to 400 m 2 / g, specific pore volume 0.4~0.6cm 3 / g.

[0035] According to some specific embodiments of the present invention, the thermal conductivity of the montmorillonite is 0.25-0.5 W / m·K, and the specific heat capacity is 850 J / kg·K.

[0036] According to some specific embodiments of the present invention, the specific surface area of ​​the montmorillonite is 200 to 800 m 2 / g, specific pore volume 0.4~0.6cm 3 / g.

[0037] According to some specific embodiments of the present invention, the diatomaceous earth has a thermal conductivity of 0.1 to 0.2 W / m·K and a specific heat capacity of 800 J / kg·K.

[0038] According to some specific embodiments of the present invention, the diatomaceous earth has a specific surface area of ​​20 to 30 m 2 / g, specific pore volume 0.1~0.2cm 3 / g.

[0039] According to some specific embodiments of the present invention, the mass concentration of the pseudo-boehmite in the pseudo-boehmite-acid mixed slurry is 20-55 wt %.

[0040] According to some specific embodiments of the present invention, the mass concentration of sodium silicate in the sodium silicate-acid mixed slurry is 20-30 wt%.

[0041] According to some specific embodiments of the present invention, the content of aluminum oxide in the aluminum sol is 10-40 wt%.

[0042] According to some specific embodiments of the present invention, the content of silicon oxide in the silica sol is 10-40 wt %.

[0043] According to some specific embodiments of the present invention, the acid is at least one of nitric acid, hydrochloric acid, citric acid, oxalic acid or sulfuric acid.

[0044] According to some specific embodiments of the present invention, the pH of the binder is 3-5.

[0045] According to some specific embodiments of the present invention, the molecular sieve is at least one selected from Y-type molecular sieve, β-type molecular sieve and MFI molecular sieve.

[0046] According to some specific embodiments of the present invention, the molecular sieve is at least one selected from REY molecular sieve, USY molecular sieve, REUSY molecular sieve, HY molecular sieve, REHY molecular sieve and ZSM-5 molecular sieve.

[0047] According to some specific embodiments of the present invention, the average crystal size of the molecular sieve is 0.2-10 μm.

[0048] According to some specific embodiments of the present invention, the relative crystallinity of the molecular sieve is 90-99%.

[0049] According to some specific embodiments of the present invention, the thermal storage catalyst is prepared by a method comprising the following steps:

[0050] The step of preparing slurry A by mixing clay, a binder and water; the mass ratio of clay to binder is (0.5-0.9): (0.1-0.2), and the water is 1-2 times the total solid mass of this step;

[0051] a step of mixing molecular sieve, clay, binder and water to obtain slurry B, wherein the mass ratio of molecular sieve, clay and binder is (0.3-1.5):(0.1-0.3):(0.1-0.4), and water is 1-2 times the total solid mass of this step;

[0052] a step of mixing a thermal storage material, clay, a binder and water to obtain a slurry C, wherein the mass ratio of the thermal storage material, clay and binder is (0.3-1.2):(0.1-0.65):(0.05-0.25), and the water is 1-2 times the total solid mass of this step;

[0053] The catalyst is obtained by uniformly mixing slurry A, slurry B and slurry C in a mass ratio of 1:(0.7-1.4):(0.4-1.6), spray drying the mixture and then calcining the mixture.

[0054] According to some specific embodiments of the present invention, in the step of preparing slurry A, the mass ratio of clay to binder is (0.8-0.9):(0.1-0.2).

[0055] According to some specific embodiments of the present invention, the clay is selected from at least one of kaolin, sepiolite, attapulgite, rectorite, montmorillonite and diatomaceous earth.

[0056] According to some specific embodiments of the present invention, the binder is selected from at least one of pseudo-boehmite-acid mixed slurry, aluminum sol, silica sol and sodium silicate-acid mixed slurry.

[0057] According to some specific embodiments of the present invention, the calcination temperature is 500-700°C.

[0058] According to some specific embodiments of the present invention, the calcination temperature is 500-600°C.

[0059] According to some specific embodiments of the present invention, the calcination time is 3-10 hours.

[0060] According to some specific embodiments of the present invention, the calcination time is 3 to 5 hours.

[0061] According to some specific embodiments of the present invention, the drying temperature is 80-140°C.

[0062] According to some specific embodiments of the present invention, the drying temperature is 80-100°C.

[0063] According to some specific embodiments of the present invention, the temperature of the reaction chamber for preparing light olefins (reaction tube temperature) is 600-750°C.

[0064] According to some specific embodiments of the present invention, the temperature of the reaction chamber for preparing light olefins is 600-700°C.

[0065] According to some specific embodiments of the present invention, the reaction time for preparing light olefins is 0.3-8s.

[0066] According to some specific embodiments of the present invention, the reaction time for preparing light olefins is 1-2.5 s.

[0067] According to some specific embodiments of the present invention, the agent-oil ratio for preparing light olefins is 4-50.

[0068] According to some specific embodiments of the present invention, the agent-oil ratio for preparing light olefins is 7-15.

[0069] According to some specific embodiments of the present invention, the weight hourly space velocity for preparing light olefins is 0.1-30h -1 .

[0070] According to some specific embodiments of the present invention, the light oil is naphtha.

[0071] According to some specific embodiments of the present invention, the light oil is straight-run naphtha.

[0072] According to some specific embodiments of the present invention, the content of saturated hydrocarbons in the straight-run naphtha is not less than 65 wt %.

[0073] According to some specific embodiments of the present invention, the low-carbon olefin is selected from at least one of ethylene, propylene and butene.

[0074] According to some specific embodiments of the present invention, the method further comprises a step of regenerating the thermal storage catalyst by an electric heating method.

[0075] According to some specific embodiments of the present invention, the catalytic cracking device used in the method includes a reactor 1, a regenerator 7 and a supplementary heat device 8;

[0076] The reactor 1 includes, from top to bottom, a settler 3, a stripping section 4 and a reaction tube 5;

[0077] The reactor 1 is connected to the lower end of the regenerator 7 through the spent agent pipe 14 provided at the lower end of the stripping section 4, and is connected to the middle section of the regenerator 7 through the regeneration agent pipe 15 provided at the lower end of the reaction tube 5;

[0078] The reheater 8 is connected to the middle section of the regenerator 7 through a reheating catalyst inlet 19 provided at the upper end, and is connected to the lower end of the regenerator through a reheating catalyst outlet 21 provided at the bottom end.

[0079] During the catalytic cracking process, in order to allow the catalyst and reaction system to reach the reaction and regeneration temperatures required for operation, the catalyst can be heated for supplementary heat, preferably electrically, so that the catalyst circulates in the catalytic cracking system to increase the temperature. Secondly, by adopting a heating method, the problem of small coke production during the reaction and low regenerator temperature is solved. The heating method, especially the electric heating method, is highly compatible with thermal storage catalysts. Thermal storage catalysts can quickly absorb and evenly distribute the heat provided by the electric heating system, ensuring precise temperature control during the reaction and reducing the impact of temperature fluctuations on catalyst performance.

[0080] According to some specific embodiments of the present invention, the number of the supplementary heat devices 8 is 1-5.

[0081] The supplementary heater heats the catalyst evenly through the heating element and can also serve as a catalyst storage tank from which fresh catalyst is added.

[0082] According to some specific embodiments of the present invention, a raw material inlet 10 is opened at the bottom of the reaction tube 5 .

[0083] According to some specific embodiments of the present invention,

[0084] A first cyclone separator 2 is provided inside the upper end of the reactor, and a product outlet 12 is provided at the top;

[0085] A second steam inlet 16 is provided at the bottom of the stripping section;

[0086] The second cyclone separator 6 is provided inside the upper end of the regenerator 7, a regeneration flue gas outlet 13 is provided at the top, a first main air distribution pipe 9 is provided inside the lower end, and an air inlet 11 is provided at the bottom end.

[0087] According to some specific embodiments of the present invention, 5-50 columnar electric heating units 24 are arranged inside the reheater 8, a reheating catalyst inlet 19 is arranged at the upper end of the reheater 8, a fresh catalyst inlet 17 is arranged at the top, and a reheating catalyst outlet 20 is arranged at the bottom.

[0088] According to some specific embodiments of the present invention, the spacing between the electric heating units 24 is 1.5 to 2 times the diameter of the electric heating units.

[0089] According to some specific embodiments of the present invention, a second main air distribution pipe 23 is provided at the bottom of the reheater 8 .

[0090] According to some specific embodiments of the present invention, a gas outlet 18 is provided on the upper side wall of the reheater 8 .

[0091] According to some specific embodiments of the present invention, the electric heating unit 24 is mainly composed of an electric heating tube 25 and a sleeve 27 wrapped around the outside of the electric heating tube, and a heat transfer fin 26 is coiled on the outer surface of the electric heating tube.

[0092] According to some specific embodiments of the present invention, the electric heating tube 25 is fixedly disposed inside the sleeve 27 via a support structure 28 .

[0093] According to some specific embodiments of the present invention, the support structure 28 is disposed at the bottom of the electric heating tube 25 .

[0094] According to some specific embodiments of the present invention, the heat transfer fins 26 are spirally coiled and arranged on the outer surface of the electric heating tube.

[0095] According to some specific embodiments of the present invention, the spiral winding angle of the heat transfer fins 26 is 15 to 45 degrees.

[0096] According to some specific embodiments of the present invention, the electric heating tube 25 is fixed in the inner cavity of the reheater 8 by at least one fixing clamp 22 .

[0097] According to some specific embodiments of the present invention, there are two fixing splints 22, which are respectively arranged at the upper end and the lower end of the inner cavity of the reheater 8.

[0098] According to some specific embodiments of the present invention, a junction box 21 is provided at the upper end of the supplementary heat device 8 , and the junction box is electrically connected to the electric heating tube 25 and the control system 30 via cables 29 .

[0099] According to some specific embodiments of the present invention, the cable 29 is a high-temperature explosion-proof cable.

[0100] Each heating tube of the present invention can be controlled independently to adjust the heating power and uniformity, and the overall temperature can be controlled from the local temperature.

[0101] According to some specific embodiments of the present invention, the controlled temperature in the supplementary heat device 8 is 600-900°C.

[0102] According to some specific embodiments of the present invention, the electric heating tube is a resistance heating tube.

[0103] According to some specific embodiments of the present invention, the material of the resistance heating tube is nickel-chromium alloy and / or iron-chromium-aluminum alloy.

[0104] According to some specific embodiments of the present invention, the heating temperature of the resistance heating tube can reach 1200°C.

[0105] The catalyst and catalytic cracking device of the present invention uniformly heat the catalyst through an electric heating element, thereby increasing the internal energy density of the catalyst. The method of the present invention can optimize the heat management of the regenerator and reactor, thereby increasing the yield of light olefins and the service life of the catalyst, and avoiding the problem of local overheating of the catalyst caused by spontaneous combustion of fuel oil or coal powder in traditional methods.

[0106] According to some specific embodiments of the present invention, the sleeve 27 is a ceramic wear-resistant sleeve.

[0107] According to some specific embodiments of the present invention, the sleeve 27 has a temperature resistance of above 1400°C.

[0108] In summary, the present invention provides a method for producing light olefins by catalytic cracking of light oil. The method of the present invention has the following advantages:

[0109] (1) Reduce catalyst loss. The present invention electrically heats the thermal storage catalyst to supplement heat for the regenerator and provide energy for the cracking reaction, replacing the existing method of adding fuel oil or coal powder for supplementary heat. This avoids local overheating that causes structural deactivation of the catalyst, helps slow down the rate of catalyst activity reduction, reduces catalyst consumption, and eliminates additional carbon emissions.

[0110] (2) Optimize heat utilization. During the regeneration process, the coke on the catalyst surface releases heat, and the close proximity between the heat storage material and the catalyst enhances heat transfer, reduces energy loss, and improves heat utilization efficiency.

[0111] (3) Enhance reaction stability. During the reaction process, the heated heat storage material provides uniform heat in the reactor, providing heat for the cracking reaction in a timely manner, making the heat of the catalyst in the riser more uniform, reducing the temperature gradient difference of the catalyst bed, and ensuring the stability and consistency of the reaction process.

[0112] (4) Improve yield and selectivity, optimize heat management, maintain the optimal temperature for low-carbon olefin yield and selectivity, reduce side reactions caused by uneven temperature, and increase the output of high value-added products.

[0113] (5) Flexible operation, environmental friendliness, and improved safety. The electric heating system can precisely control the heating temperature and power, has high operational flexibility, and can adapt to different process conditions and production requirements. Using electric heating instead of fuel oil spontaneous combustion reduces pollution emissions during the combustion process and avoids the risk of fire caused by fuel oil spontaneous combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0114] Figure 1 This is a schematic diagram of the catalytic cracking device according to Example 1 of the present invention.

[0115] Figure 2 This is a schematic diagram of the supplementary heat device described in Example 1 of the present invention.

[0116] Figure 3 This is a schematic diagram of the structure of the electric heating tube of the heat replenisher in Example 1 of the present invention.

[0117] Description of main figures:

[0118] Reactor 1, first cyclone separator 2, settler 3, stripping section 4, reaction tube 5, second cyclone separator 6, regenerator 7, supplementary heat device 8, first main air distribution pipe 9, raw material inlet 10, air inlet 11, product outlet 12, regenerated flue gas outlet 13, regenerated agent pipe 14, regenerated agent pipe 15, second steam inlet 16, fresh catalyst inlet 17, gas outlet 18, supplementary heat catalyst inlet 19, supplementary heat catalyst outlet 20, junction box 21, fixing splint 22, second main air distribution pipe 23, electric heating unit 24, electric heating pipe 25, heat transfer fins 26, wear-resistant ceramic pipe sleeve 27, support structure 28, high-temperature explosion-proof cable 29. DETAILED DESCRIPTION

[0119] The following describes in detail the implementation process of the present invention and the beneficial effects produced by it through specific examples, which is intended to help readers better understand the essence and characteristics of the present invention and is not intended to limit the scope of implementation of this case.

[0120] Example 1

[0121] Use Figure 1 The catalytic cracking reaction-regeneration device shown produces light olefins (reheater such as Figure 2 and Figure 3 The device includes a reactor 1, a regenerator 7 and a supplementary heat device 8. The process includes:

[0122] The catalyst employed was the ZSM-5 / magnesium oxide-based catalyst with heat storage function disclosed herein. Catalyst preparation process: 900g of kaolin, 100g of pseudo-boehmite-hydrochloric acid solution (pH 3), and 1800g of deionized water were uniformly mixed under stirring to obtain slurry A. 1500g of ZSM-5 molecular sieve, 300g of kaolin, 100g of aluminum sol (alumina content: 10 wt%), and 2000g of deionized water were slurried and stirred for 1 hour to obtain slurry B. 100g of kaolin, 400g of magnesium oxide, 100g of aluminum sol, and 600g of deionized water were slurried and stirred for 1 hour to obtain slurry C. Slurries A, B, and C were mixed, homogenized, spray-formed, and calcined at 500°C for 5 hours. Deionized water was then added, stirred, washed at 80°C for 20 minutes, and filtered to obtain catalyst FCC-1.

[0123] Reaction process: Naphtha is sprayed into the reaction tube 5 through an atomizing nozzle, where it comes into contact with the high-temperature regenerated catalyst from the regenerator 7, and is then vaporized and reacts. The reaction product passes through the first cyclone separator 2 to separate the entrained catalyst, leaves the settler 3, and leaves the device through the product outlet 12. The regenerated catalyst falls from the settler 3 into the stripping section 4 below. The stripping section is equipped with multiple layers of herringbone baffles. After being stripped by stripping steam (from the second steam inlet 16), it is sent to the regenerator 7 through the regenerated catalyst pipe 14 for regeneration.

[0124] Regeneration Process: The regenerated catalyst enters the regenerator 7 through the air inlet 11 and is regenerated in the regenerator 7 by the combustion of the regeneration air passing through the first main air distribution pipe 9. The regenerated flue gas is separated from the entrained catalyst by the second cyclone 6, passes through the second cyclone separator, and then exits the device as regenerated flue gas 13. The regenerated catalyst enters the reactor bottom through the regeneration agent pipe 15, where it comes into contact with the naphtha feedstock.

[0125] Reheating process: fresh catalyst enters the reheater from the fresh catalyst inlet 17, and regenerated catalyst enters the reheater from the regenerator 7 through the reheating catalyst inlet 19. The heat storage material of the catalyst replenishes heat in the electric heating element, and the reheated catalyst returns to the regenerator 7 through the reheating catalyst outlet 20.

[0126] Example 2

[0127] The catalyst used is the ZSM-5 / silicon carbide matrix catalyst with heat storage function of the present invention. Catalyst preparation process: 900g of sepiolite, 100g of pseudo-boehmite-nitric acid solution (pH 5), and 1800g of deionized water were uniformly mixed under stirring to obtain slurry A. 300g of ZSM-5 molecular sieve, 300g of sepiolite, 400g of aluminum sol (aluminum content of 40wt%), and 1200g of deionized water were mixed and slurried for 1 hour to obtain slurry B. 200g of sepiolite, 550g of silicon carbide, 250g of aluminum sol, and 1600g of deionized water were mixed and slurried for 1 hour to obtain slurry C. Slurries A, B, and C were mixed, homogenized, spray-formed, and calcined at 700°C for 6 hours. Deionized water was then added, stirred, washed at 100°C for 20 minutes, and filtered to obtain catalyst FCC-2. The specific process steps are the same as in Example 1.

[0128] Example 3

[0129] The catalyst employed the ZSM-5 / aluminum nitride matrix catalyst with heat storage function of the present invention. Catalyst preparation process: 800g of attapulgite, 100g of pseudo-boehmite-citric acid solution (pH 4), and 1600g of deionized water were uniformly mixed under stirring to obtain slurry A. 500g of ZSM-5 molecular sieve, 100g of attapulgite, 100g of aluminum sol (40wt% alumina content), and 1200g of deionized water were slurried and stirred for 1 hour to obtain slurry B. 100g of attapulgite, 1200g of aluminum nitride, 100g of aluminum sol, and 2400g of deionized water were slurried and stirred for 1 hour to obtain slurry C. Slurries A, B, and C were mixed, homogenized, spray-formed, and calcined at 550°C for 8 hours. Deionized water was then added, stirred, washed at 140°C for 20 minutes, and filtered to obtain catalyst FCC-3.

[0130] The specific process steps are the same as those in Example 1.

[0131] Example 4

[0132] The catalyst used is the ZSM-5 / silicon nitride matrix catalyst with heat storage function of the present invention. Catalyst preparation process: Under stirring conditions, 800g of rectorite, 200g of sodium silicate-oxalic acid solution (pH 5), and 1600g of deionized water are uniformly mixed to obtain slurry A. 700g of ZSM-5 molecular sieve, 100g of rectorite, 100g of silica sol (silicon oxide content is 40wt%), and 1600g of deionized water are mixed and beaten, and stirred for 1 hour to obtain slurry B. 100g of rectorite, 800g of silicon nitride, 100g of silica sol, and 1800g of deionized water are mixed and beaten, and stirred for 1 hour to obtain slurry C. Slurries A, B, and C are mixed, homogenized, spray-formed, and calcined at 600°C for 10 hours. Deionized water is then added, stirred evenly, washed at 100°C for 20 minutes, and filtered to obtain catalyst FCC-4. The specific process steps are the same as those in Example 1.

[0133] Example 5

[0134] The catalyst employed the ZSM-5 / boron nitride matrix catalyst with heat storage function of the present invention. Catalyst preparation process: 850g of montmorillonite, 150g of sodium silicate-sulfuric acid solution (pH 4), and 1500g of deionized water were uniformly mixed under stirring to obtain slurry A. 500g of ZSM-5 molecular sieve, 300g of diatomaceous earth, 200g of silica sol (10wt% silicon oxide), and 1600g of deionized water were mixed and slurried for 1 hour to obtain slurry B. 650g of montmorillonite, 300g of boron nitride, 50g of silica sol, and 1900g of deionized water were mixed and slurried for 1 hour to obtain slurry C. Slurries A, B, and C were mixed, homogenized, spray-formed, and calcined at 600°C for 3 hours. Deionized water was then added, stirred uniformly, washed at 120°C for 20 minutes, and filtered to obtain catalyst FCC-5.

[0135] The specific process steps are the same as those in Example 1.

[0136] Comparative Example 1

[0137] The catalyst used was a ZSM-5 / kaolin-based catalyst. Catalyst preparation process: 800g of kaolin, 200g of sodium silicate-oxalic acid solution (pH 5), and 1600g of deionized water were uniformly mixed under stirring to obtain slurry A. 700g of ZSM molecular sieve, 100g of kaolin, 100g of silica sol (silicon oxide content: 40wt%), and 1600g of deionized water were mixed and beaten, and stirred for 1 hour to obtain slurry B. 900g of kaolin, 100g of silica sol, and 1800g of deionized water were mixed and beaten, and stirred for 1 hour to obtain slurry C. Slurries A, B, and C were mixed, homogenized, spray-formed, and calcined at 600°C for 10 hours. Deionized water was then added, stirred, washed at 100°C for 20 minutes, and filtered to obtain the comparative catalyst FCC-6.

[0138] The specific process steps are the same as those in Example 1.

[0139] Comparative Example 2

[0140] The catalyst used was a ZSM-5 / kaolin-based catalyst, and the catalyst preparation process was the same as that of Comparative Example 1.

[0141] The specific operating steps of Comparative Example 2 are as follows:

[0142] Reaction process: Naphtha is sprayed into the reaction tube 5 through an atomizing nozzle, where it comes into contact with the high-temperature regenerated catalyst from the regenerator 7, and is then vaporized and reacts. The reaction product passes through the first cyclone separator 2 to separate the entrained catalyst, leaves the settler 3, and leaves the device through the product outlet 12. The regenerated catalyst falls from the settler 3 into the stripping section 4 below. The stripping section is equipped with multiple layers of herringbone baffles. After being stripped by stripping steam (from the second steam inlet 16), it is sent to the regenerator 7 through the regenerated catalyst pipe 14 for regeneration.

[0143] Regeneration Process: The regenerated catalyst enters the regenerator 7 through the air inlet 11 and is regenerated in the regenerator 7 by the combustion of regeneration air passing through the first main air distribution pipe 9. Insufficient heat is provided by fuel oil, which is sprayed from the bottom of the regenerator. The fuel-coated regenerated catalyst comes into contact with the air and combusts. The regenerated flue gas passes through the second cyclone 6 to separate the entrained catalyst, then passes through the second cyclone and exits the device as regenerated flue gas 13. The regenerated catalyst enters the reactor bottom through the regeneration agent pipe 15 to come into contact with the naphtha feedstock for reaction.

[0144] The physical properties of the naphtha used in the examples and comparative examples of the present invention are shown in Table 1.

[0145] Table 1

[0146] Naphtha property parameters <![CDATA[Density (20 °C), g / cm 3 > 0.7408 Group composition, w% normal alkanes 35.62 Isoalkanes 29.41 Olefins 0.34 Cycloalkanes 25.45 Aromatics 9.18 Distillation range, ℃ IBP 44 10％ 87 30％ 108 50％ 121 70％ 131 90％ 154 95％ 160

[0147] The evaluation results of the catalytic cracking system of the present invention are shown in Table 2.

[0148] Table 2

[0149]

[0150]

[0151] The catalyst provided by this invention is well compatible with the electric heating system. The electric heating system does not increase carbon emissions, heats quickly, and can be precisely controlled, avoiding the hysteresis associated with the combustion temperature of fuel oil or pulverized coal. The catalyst's high thermal conductivity and high specific heat capacity allow it to absorb the heat energy from the electric heating system more quickly and replenish the required heat during the reaction, thereby maintaining the catalyst's optimal reaction temperature. This method effectively reduces the rate of side reactions caused by excessively high or low temperatures, improving reaction efficiency and product selectivity.

[0152] See Table 3, which shows the temperatures at different positions of the reactor and regenerator bed in the naphtha catalytic cracking reaction to produce light olefins in Example 2 and Comparative Example 1.

[0153] Table 3

[0154] Bed location Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Bed entrance 669℃ 662℃ 659℃ 662℃ 665℃ 690℃ Middle of the bed 650℃ 650℃ 650℃ 650℃ 650℃ 650℃ upper part of bed 640℃ 641℃ 645℃ 644℃ 642℃ 630℃ regenerate upper part 700℃ 700℃ 700℃ 700℃ 700℃ 700℃ Regeneration of Central 687℃ 693℃ 694℃ 692℃ 688℃ 676℃ Next section of regeneration 677℃ 685℃ 682℃ 682℃ 680℃ 650℃

[0155] Without the aid of a thermal storage material, in a comparison between Example 3 and Comparative Example 1, the catalyst using the thermal storage material exhibited a 14°C temperature difference between the bed inlet and outlet (the upper portion of the bed) when the central temperature was maintained at 650°C. This difference, however, was 60°C for the catalyst in Comparative Example 1. This increased temperature difference can increase the rate of side reactions, reduce catalyst activity and selectivity, and lower the yield of light olefins.

[0156] Table 4 is the catalyst particle size volume distribution table before and after the reaction of the reaction device

[0157] Table 4

[0158]

[0159] As shown in Table 4, using fuel oil for supplemental heating often results in large temperature differences inside and outside the catalyst due to its uneven properties, leading to thermal collapse and fragmentation due to thermal stress. This fragmentation alters the catalyst's particle size distribution, increasing the proportion of catalyst particles below 20 μm and shortening the catalyst's operating life. As the fine particle content increases, these small particles are difficult to separate in the cyclone separator, causing catalyst loss and catalyst runaway, resulting in decreased catalyst activity and altered reaction depth. However, using electric heating combined with thermal storage materials provides stable and uniform heat, avoiding catalyst thermal collapse caused by localized overheating. Thermal storage materials have improved thermal conductivity and heat storage properties, effectively storing and releasing heat during the electric heating process, ensuring uniform heat transfer when in contact with the catalyst. This process reduces the temperature difference between the catalyst's interior and surface, minimizing the risk of fragmentation due to thermal stress and maintaining the catalyst's particle size distribution and stability. This extends the catalyst's operating life, reduces the fines content, and enhances the overall stability and efficiency of the reaction system.

Claims

1. A method for producing light olefins by catalytic cracking of light oil, wherein: The method comprises the steps of using light oil as a raw material and a heat storage catalyst as a catalyst to prepare light olefins; Taking the dry basis of the thermal storage catalyst as 100%, the catalyst contains at least the following components in weight percentage: 10%-50% molecular sieve, 10%-40% thermal storage material, and 40%-80% carrier; The thermal conductivity of the heat storage material is 20-500 W / (m·K), and the specific heat capacity is 600-1200 J / (kg·K), and the heat storage material is selected from at least one of magnesium oxide, silicon carbide, aluminum nitride, silicon nitride, and boron nitride; The carrier is SiO2 and / or Al2O3; The molecular sieve is at least one selected from Y-type molecular sieve, β-type molecular sieve and MFI molecular sieve; The method further comprises the step of regenerating the thermal storage catalyst by an electric heating method; The catalytic cracking device used in the method includes a reactor (1), a regenerator (7) and a supplementary heat device (8); The reactor (1) comprises, from top to bottom, a settler (3), a stripping section (4) and a reaction tube (5); The reactor (1) is connected to the lower end of the regenerator (7) through a spent agent pipe (14) provided at the lower end of the stripping section (4), and is connected to the middle section of the regenerator (7) through a regeneration agent pipe (15) provided at the lower end of the reaction tube (5); The reheater (8) is connected to the middle section of the regenerator (7) through a reheating catalyst inlet (19) provided at the upper end, and is connected to the lower end of the regenerator through a reheating catalyst outlet (20) provided at the lower end; 5-50 columnar electric heating units (24) are arranged inside the reheater (8), a reheating catalyst inlet (19) is arranged at the upper end of the reheater (8), a fresh catalyst inlet (17) is arranged at the top, and a reheating catalyst outlet (20) is arranged at the bottom.

2. The method according to claim 1, wherein The particle size of the heat storage material is 100-200 meshes.

3. The method according to claim 1, wherein The temperature of the reaction chamber for preparing light olefins is 600-750°C.

4. The method according to claim 1, wherein The reaction time for preparing light olefins is 0.5-8 s.

5. The method according to claim 1, wherein The agent-oil ratio for preparing light olefins is 4-50.

6. The method according to claim 1, wherein The light oil is naphtha; The low-carbon olefin is selected from at least one of ethylene, propylene and butene.

7. The method according to claim 1, wherein The light oil is straight-run naphtha.

8. The method according to claim 7, wherein The content of saturated hydrocarbons in the straight-run naphtha is not less than 65 wt %.

9. The method according to claim 1, wherein: A first cyclone separator (2) is provided inside the upper end of the reactor, and a product outlet (12) is provided at the top end; A second steam inlet (16) is provided at the bottom of the stripping section; A second cyclone separator (6) is provided inside the upper end of the regenerator (7), a regeneration flue gas outlet (13) is provided at the top end, a first main air distribution pipe (9) is provided inside the lower end, and an air inlet (11) is provided at the bottom end.

10. The method according to claim 1, wherein A second main air distribution pipe (23) is provided at the bottom of the interior of the reheater (8).

11. The method according to claim 1, wherein The electric heating unit (24) is mainly composed of an electric heating tube (25) and a sleeve (27) wrapped around the outside of the electric heating tube, and a heat transfer fin (26) is coiled around the outer surface of the electric heating tube.

12. The method according to claim 11, wherein A junction box (21) is provided at the upper end of the supplementary heater (8), and the junction box is electrically connected to the electric heating tube (25) and the control system (30).

13. The method according to any one of claims 1 to 12, wherein The control temperature in the supplementary heater (8) is 600-900°C.

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