Method for preparing low-carbon olefin through catalytic cracking of light oil

Abstract

The invention provides a method for preparing low-carbon olefin by catalytic cracking of light oil. The method comprises the following steps: preparing the low-carbon olefin by taking light oil as a raw material and a heat storage type catalyst as a catalyst; on the basis that the dry basis of the heat storage type catalyst is 100%, the catalyst at least comprises the following components in percentage by weight: 10%-50% of a molecular sieve, 10%-40% of a heat storage material and 40%-80% of a carrier, the heat conductivity coefficient of the heat storage material is 20-500 W / m.K, and the specific heat capacity of the heat storage material is 600-1200 J / kg.K. According to the invention, the heat storage type catalyst is electrically heated, heat is supplemented for the regenerator, energy is provided for the cracking reaction, the existing method for supplementing heat by adding fuel oil or pulverized coal is replaced, the structural inactivation of the catalyst caused by local overheating is avoided, the reduction rate of the activity of the catalyst is favorably slowed down, the consumption of the catalyst is reduced, and no extra carbon emission is generated.

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] The existing catalytic cracking process is widely used in the petrochemical industry. With the change of market demand, the catalytic cracking process began to use light oil such as naphtha or diesel to crack and produce low-carbon olefins (such as ethylene, propylene and butene). Low-carbon olefins are the basic raw materials for the production of various polymers and other value-added chemicals, and are widely used in various chemical industries such as pharmaceuticals, food and dyes. However, the catalytic cracking reaction is a strong endothermic reaction that needs to be carried out under high temperature conditions, but the amount of coke generated by the light oil reaction is small, resulting in insufficient heat in the regenerator, making it difficult to maintain the required high temperature.

[0003] In the traditional regenerator operation process, the method of spraying fuel oil into the catalyst bed is often used to supplement heat through the spontaneous combustion 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 will cause the catalyst pores to collapse and particles to break, seriously affecting the service life and reaction efficiency of the catalyst. Secondly, the catalytic cracking reaction is a strong 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 causes significant energy waste.

[0004] In order to solve this problem, patent CN100337736C adds coal powder with a particle size of 10 to 140 μm to the catalyst regenerator continuously or intermittently. This method can save a lot of light fuel oil, reduce equipment costs, and improve economic benefits. However, the pulverized coal is prone to blockage and uneven distribution during transportation, resulting in incomplete combustion; additional pollutants are generated while burning the pulverized coal, complicating the flue gas treatment process. In addition, the coal ash produced after combustion may be adsorbed on the catalyst surface or accumulated in the regenerator, affecting the operating efficiency and catalyst activity.

[0005] Patent CN115305107A discloses an external supplementary heat electric heater device for the regenerator of a fluidized bed light hydrocarbon processing device, which is used to solve the problems of insufficient supplementary combustion capacity of the regenerator of old devices, imperfect flue gas treatment system or insufficient power of the main fan. The electric heater uses green electricity energy, significantly reduces carbon emissions, and can more accurately control the amount of supplementary heat. However, the invention does not fully consider the thermal conductivity and heat storage capacity of the catalyst, so that during the electric heating supplementary heat process, the catalyst may still not reach the ideal working conditions. Summary of the invention

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

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

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

[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; and Al2O3 is derived from an aluminum-containing binder and / or aluminum-containing clay.

[0025] The silicon-containing clay is selected from one or more combinations of kaolin, sepiolite, attapulgite, rectorite, montmorillonite and diatomite; the aluminum-containing clay is selected from one or more combinations 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 thermal conductivity of the kaolin is 0.25-0.35 W / m·K, and the specific heat capacity is 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 rectorite has a specific surface area of ​​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 montmorillonite has a specific surface area of ​​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 0.1-0.2 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 pseudo-boehmite in the pseudo-boehmite-acid mixed slurry is 20-55wt%.

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

[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 of a Y-type molecular sieve, a β-type molecular sieve and an 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 mixing clay, a binder and water to prepare a slurry A; the mass ratio of clay to binder is (0.5-0.9):(0.1-0.2), and 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 the binder is (0.3-1.2):(0.1-0.65):(0.05-0.25), and water is 1-2 times the total solid mass of this step;

[0053] The step of 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 and then calcining to obtain the catalyst.

[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 the 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 a settler 3, a stripping section 4 and a reaction tube 5 from top to bottom;

[0077] The reactor 1 is connected to the lower end of the regenerator 7 through the spent agent pipe 14 arranged 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 arranged 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 arranged at the upper end, and is connected to the lower end of the regenerator through a reheating catalyst outlet 21 arranged at the bottom end.

[0079] In the catalytic cracking process, in order to make the catalyst and the reaction system reach the reaction and regeneration temperature 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 the heating method, the problem of small coke production in the reaction and low temperature in the regenerator is solved. The heating method, especially the electric heating method, is highly compatible with the heat storage catalyst. The heat storage catalyst can quickly absorb and evenly distribute the heat provided by the electric heating system, ensuring accurate control of the temperature during the reaction and reducing the impact of temperature fluctuations on the catalyst performance.

[0080] According to some specific embodiments of the present invention, the number of supplementary heat devices 8 is 1 to 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 disposed inside the upper end of the reactor, and a product outlet 12 is disposed 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 arranged inside the upper end of the regenerator 7, a regeneration smoke outlet 13 is arranged at the top, a first main air distribution pipe 9 is arranged inside the lower end, and an air inlet 11 is arranged 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 supplementary heat device 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 supporting 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 supplementary heat device 8 by at least one fixing clamp 22 .

[0097] According to some specific embodiments of the present invention, there are two fixing clamps 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 through 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 independently controlled so as to adjust the heating power and uniformity, and control the overall temperature 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 to increase the internal energy density of the catalyst. The method of the present invention can optimize the heat management of the regenerator and the 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 preparing low-carbon 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 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 coal powder for supplementary heat, avoiding local overheating and causing structural deactivation of the catalyst, which is beneficial to slowing down the rate of catalyst activity reduction, reducing catalyst consumption, and no additional carbon emissions.

[0110] (2) Optimize heat utilization. During the regeneration process, the coke on the catalyst surface releases heat, and the heat storage material and catalyst are in close proximity to enhance heat transfer, reduce energy loss, and improve 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 accurately control the heating temperature and power, has high operational flexibility, and is adaptable to different process conditions and production requirements. Using electric heating instead of fuel oil spontaneous combustion can reduce pollution emissions during the combustion process and avoid 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 supplementary heater of 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, supporting structure 28, high temperature explosion-proof cable 29. DETAILED DESCRIPTION

[0119] The implementation process of the present invention and the beneficial effects produced are described in detail below through specific embodiments, 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 the present invention.

[0120] Example 1

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

[0122] The catalyst adopts the ZSM-5 / magnesium oxide matrix catalyst with heat storage function of the present invention. Catalyst preparation process: Under stirring conditions, 900g kaolin, 100g pseudo-boehmite-hydrochloric acid solution (pH is 3) and 1800g deionized water are uniformly mixed to obtain slurry A. 1500g ZSM-5 molecular sieve, 300g kaolin, 100g aluminum sol (aluminum oxide content is 10wt%) and 2000g deionized water are mixed and slurried, stirred for 1h to obtain slurry B. 100g kaolin, 400g magnesium oxide, 100g aluminum sol and 600g deionized water are mixed and slurried, stirred for 1h to obtain slurry C. Slurries A, B and C are mixed, and the slurry is sprayed after homogenization, and then roasted at 500℃ for 5h. Then deionized water is added, stirred evenly, washed at 80℃ for 20min, and filtered to obtain catalyst FCC-1.

[0123] Reaction process: Naphtha is sprayed into the reaction tube 5 through an atomizing nozzle, where it contacts the high-temperature regenerated catalyst from the regenerator 7, and then vaporizes 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 catalyst to be regenerated enters the regenerator 7 through the air inlet 11 and is regenerated in the regenerator 7 under the combustion of the regeneration air passing through the first main air distribution pipe 9. After the regenerated flue gas passes through the second cyclone separator 6 to separate the entrained catalyst, it passes through the second cyclone separator and leaves the device through the regeneration flue gas 13. The regenerated catalyst enters the bottom of the reactor through the regeneration agent pipe 15 to contact and react with the naphtha raw material.

[0125] Reheating process: fresh catalyst enters the reheater from the fresh catalyst inlet 17, 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 adopts the ZSM-5 / silicon carbide matrix catalyst with heat storage function of the present invention. Catalyst preparation process: Under stirring conditions, 900g of sepiolite, 100g of pseudo-boehmite-nitric acid solution (pH is 5) and 1800g of deionized water are uniformly mixed to obtain slurry A. 300g of ZSM-5 molecular sieve, 300g of sepiolite, 400g of aluminum sol (alumina content is 40wt%) and 1200g of deionized water are mixed and slurried, stirred for 1h to obtain slurry B. 200g of sepiolite, 550g of silicon carbide, 250g of aluminum sol and 1600g of deionized water are mixed and slurried, stirred for 1h to obtain slurry C. Slurries A, B and C are mixed, and the slurry is homogenized, spray-formed, and then roasted at 700°C for 6h. Then deionized water is added, stirred evenly, washed at 100°C for 20min, and filtered to obtain catalyst FCC-2. The specific process steps are the same as those in Example 1.

[0128] Example 3

[0129] The catalyst adopts the ZSM-5 / aluminum nitride matrix catalyst with heat storage function of the present invention. Catalyst preparation process: Under stirring conditions, 800g of attapulgite, 100g of pseudo-boehmite-citric acid solution (pH is 4) and 1600g of deionized water are uniformly mixed to obtain slurry A. 500g of ZSM-5 molecular sieve, 100g of attapulgite, 100g of aluminum sol (aluminum oxide content is 40wt%) and 1200g of deionized water are mixed and slurried, stirred for 1h to obtain slurry B. 100g of attapulgite, 1200g of aluminum nitride, 100g of aluminum sol and 2400g of deionized water are mixed and slurried, stirred for 1h to obtain slurry C. Slurries A, B and C are mixed, and the slurry is homogenized, spray-formed, and then calcined at 550°C for 8h. Then deionized water is added, stirred evenly, washed at 140°C for 20min, 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 adopts 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 is 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 (the content of silicon oxide is 40wt%) and 1600g of deionized water are mixed and slurried, stirred for 1h to obtain slurry B. 100g of rectorite, 800g of silicon nitride, 100g of silica sol and 1800g of deionized water are mixed and slurried, stirred for 1h to obtain slurry C. Slurries A, B and C are mixed, and the slurry is sprayed after homogenization, and then calcined at 600℃ for 10h. Then deionized water is added, stirred evenly, washed at 100℃ for 20min, 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 adopts the ZSM-5 / boron nitride matrix catalyst with heat storage function of the present invention. Catalyst preparation process: Under stirring conditions, 850g of montmorillonite, 150g of sodium silicate-sulfuric acid solution (pH is 4) and 1500g of deionized water are uniformly mixed to obtain slurry A. 500g of ZSM-5 molecular sieve, 300g of diatomaceous earth, 200g of silica sol (the content of silicon oxide is 10wt%) and 1600g of deionized water are mixed and slurried, stirred for 1h to obtain slurry B. 650g of montmorillonite, 300g of boron nitride, 50g of silica sol and 1900g of deionized water are mixed and slurried, stirred for 1h to obtain slurry C. Slurries A, B and C are mixed, and the slurry is sprayed after homogenization, and then roasted at 600℃ for 3h. Then deionized water is added, stirred evenly, washed at 120℃ for 20min, 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 uses a ZSM-5 / kaolin matrix catalyst. Catalyst preparation process: Under stirring conditions, 800g kaolin, 200g sodium silicate-oxalic acid solution (pH 5) and 1600g deionized water are uniformly mixed to obtain slurry A. 700g ZSM molecular sieve, 100g kaolin, 100g silica sol (silicon oxide content is 40wt%) and 1600g deionized water are mixed and slurried, stirred for 1h to obtain slurry B. 900g kaolin, 100g silica sol and 1800g deionized water are mixed and slurried, stirred for 1h to obtain slurry C. Slurries A, B and C are mixed, and the slurry is homogenized, spray-formed, and then calcined at 600°C for 10h. Then deionized water is added, stirred evenly, washed at 100°C for 20min, 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 matrix catalyst. 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 contacts the high-temperature regenerated catalyst from the regenerator 7, and then vaporizes 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 catalyst to be regenerated enters the regenerator 7 through the air inlet 11 and is regenerated in the regenerator 7 under the combustion of the regeneration air passing through the first main air distribution pipe 9. The insufficient heat is provided by the fuel oil, which is sprayed from the bottom of the regenerator. The catalyst to be regenerated coated with the fuel oil contacts and burns with the air. After the regenerated flue gas is separated from the entrained catalyst by the second cyclone separator 6, it passes through the second cyclone separator and then leaves the device through the regenerated flue gas 13. The regenerated catalyst enters the bottom of the reactor through the regeneration agent pipe 15 to contact and react with the naphtha raw material.

[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 properties 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 the present invention has good compatibility with the electric heating supplementary heat device. The electric heating supplementary heat system does not increase carbon emissions, has a fast heating speed, can be accurately controlled, and avoids the hysteresis of the combustion temperature of fuel oil or coal powder. Catalysts with high thermal conductivity and high specific heat capacity can absorb the heat energy of the electric heating system faster and replenish the required heat energy in time during the reaction process, thereby maintaining the optimal reaction temperature of the catalyst. This method effectively reduces the rate of side reactions caused by excessively high or low temperatures, and improves 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 position Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Bed entrance 669℃ 662℃ 659℃ 662℃ 665℃ 690℃ Middle of 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 help of heat storage material, in the comparison between Example 3 and Comparative Example 1, when the catalyst using heat storage material maintains the middle temperature at 650°C, the temperature difference between the bed inlet and outlet (upper part of the bed) is 14°C; while the temperature difference between the bed inlet and outlet of the catalyst in Comparative Example 1 is 60°C. Such an increase in temperature difference will increase the reaction rate of side reactions, reduce catalyst activity and selectivity, and reduce 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, when using fuel oil for supplementary heating, due to its unevenness, it often causes a large temperature difference between the inside and outside of the catalyst, resulting in thermal collapse and crushing under the action of thermal stress. This crushing changes the particle size distribution of the catalyst, increases the proportion of catalysts below 20μm, and shortens the operating cycle of the catalyst. As the content of fine particles increases, these small particles are not easily separated by the cyclone separator, which causes catalyst loss and runaway, resulting in a decrease in catalyst activity and a change in reaction depth. The process of using electric heating to supplement heat with heat storage materials can provide stable and uniform heat to avoid catalyst thermal collapse caused by local overheating. The heat storage material has better thermal conductivity and heat storage performance, can effectively store and release heat during the electric heating process, and can ensure uniform heat transfer when in contact with the catalyst. This process reduces the temperature difference between the inside and surface of the catalyst, reduces the risk of crushing due to thermal stress, and maintains the particle size distribution and stability of the catalyst. The service life of the catalyst is extended, the content of fine powder is reduced, and the overall reaction system is more stable and efficient.

Claims

1. A method for preparing low-carbon olefins by catalytic cracking of light oil, wherein: The method comprises using light oil as a raw material and a heat storage catalyst as a catalyst to prepare low-carbon olefins; Taking the dry basis of the heat storage catalyst as 100%, the catalyst contains at least the following weight percentage components: 10%-50% of molecular sieve, 10%-40% of heat storage material, and 40%-80% of 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. Preferably, the heat storage material is selected from at least one of magnesium oxide, silicon carbide, aluminum nitride, silicon nitride, and boron nitride; Preferably, the particle size of the thermal storage material is 100-200 mesh.

2. The method according to claim 1, wherein: The carrier is SiO2 and / or Al2O3; The molecular sieve is at least one of a Y-type molecular sieve, a β-type molecular sieve and an MFI molecular sieve.

3. The method according to claim 1 or 2, wherein: The temperature of the reaction chamber for preparing light olefins is 600-750°C (preferably the reaction time is 0.5-8s) (preferably the catalyst-oil ratio is 4-50).

4. The method according to any one of claims 1 to 3, wherein: The light oil is naphtha (preferably straight-run naphtha, more preferably the content of saturated hydrocarbons in the straight-run naphtha is not less than 65wt%); The low-carbon olefin is selected from at least one of ethylene, propylene and butene.

5. The method according to any one of claims 1 to 4, wherein: The method further comprises the step of regenerating the thermal storage catalyst by using an electric heating method.

6. The method according to claim 5, wherein: The catalytic cracking device used in the method comprises 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) arranged 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) arranged 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) arranged at the upper end, and is connected to the lower end of the regenerator through a reheating catalyst outlet (21) arranged at the bottom end.

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

8. The method according to claim 6 or 7, wherein: 5 to 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 (preferably, a second main air distribution pipe (23) is arranged at the bottom of the reheater (8)).

9. The method according to claim 8, 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 arranged on the outer surface of the electric heating tube (preferably, a junction box (21) is arranged 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)).

10. The method according to any one of claims 6 to 9, wherein: The control temperature in the supplementary heat device (8) is 600-900°C.

Images