Method for increasing yield of low-carbon olefins by catalytic cracking of hydrocarbons

Abstract

The invention provides a method for increasing the yield of ethylene and propylene by catalytic cracking of hydrocarbons, which comprises the following steps: introducing preheated raw oil and water vapor into a dense-phase fluidized bed reactor from the lower part of the dense-phase fluidized bed reactor, contacting and reacting with a catalyst in the dense-phase fluidized bed reactor, and separating to obtain low-carbon olefins such as ethylene and propylene, wherein the average solid content of a catalyst in the dense-phase fluidized bed reactor is 0.2-0.7, the solid content of the catalyst has a gentle gradient distribution characteristic that the solid content of the catalyst is gradually reduced from bottom to top in the axial direction, and the axial height of an area, in which the solid content of the catalyst is greater than 0.3, in the dense-phase fluidized bed reactor accounts for 1 / 10 or more of the total height of the dense-phase fluidized bed reactor. Compared with the prior art, the method provided by the invention has the advantages that the methane yield can be obviously reduced while high ethylene and propylene yields are obtained.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, and specifically to a method for catalytic cracking of hydrocarbons to produce more low-carbon olefins. Background Technology

[0002] Ethylene and propylene are important organic chemical raw materials, playing an irreplaceable role in many fields such as chemical engineering, agriculture, and medicine. Domestically and internationally, low-carbon olefins are mainly produced using light hydrocarbons or light naphtha fractions as feedstocks through steam cracking processes. Although steam cracking technology has undergone decades of development and continuous improvement, it still suffers from limitations such as high energy consumption, high production costs, large CO2 emissions, and difficulty in adjusting product structure. Catalytic cracking technology, as an important secondary crude oil processing technology, is increasingly valued for its advantages such as strong feedstock adaptability and flexible product formulation. In particular, the invention of ZSM-5 molecular sieve has driven the advancement of catalytic cracking technology in the production of low-carbon olefins.

[0003] Numerous research institutions and oil companies both domestically and internationally have developed proprietary catalytic cracking technologies for producing low-carbon olefins. Typical processes include DCC, Maxofin, and PetroFCC. Over the past few decades, researchers have continuously optimized and redesigned catalytic cracking processes and catalysts, resulting in continuously increasing yields of low-carbon olefins and decreasing yields of dry gas and coke. Patents developed during this research and development process primarily include the development of different reactor technologies, such as dual-riseer reactors, downflow reactors, riser + fluidized bed reactors, and variable-diameter riser reactors; and the development of different specialized catalyst preparation technologies, mainly including shape-selective molecular sieve ZSM-5 modification, Y zeolite, and matrix composition modification. These developed catalytic cracking technologies can achieve 2%-6% ethylene yield, 15%-25% propylene yield, and 10%-20% butene yield from heavy oil as feedstock. While existing catalytic cracking technologies can achieve high propylene and butene yields, the ethylene yield is relatively low, and research on this technology is limited.

[0004] CN1030313C discloses a method for the direct conversion of heavy hydrocarbons to ethylene. This method uses a solid particulate contact agent in a fluidized bed or plug flow reactor, particularly a riser or downflow tubular reactor, to react with the feedstock oil. The main reaction conditions are 650-900℃, pressure 0.13-0.28MPa, agent-to-oil ratio 5-35, and contact time 0.1-3.0 seconds. This method uses an aluminosilicate contact agent modified with alkaline or alkaline earth metal oxides. Under conditions not exceeding the tubular furnace pyrolysis temperature, it can achieve high yields of low-carbon olefins, with an ethylene yield of 17-27% and a total yield of ethylene, propylene, and butene of 30-40%. While this patent achieves high ethylene yields, it is difficult to control the formation of low-value byproducts such as methane and coke. Summary of the Invention

[0005] This application provides a method for catalytic cracking of hydrocarbons to produce ethylene and propylene, comprising:

[0006] Preheated feedstock oil and steam are introduced into the dense phase fluidized bed reactor from the bottom. They come into contact with the catalyst and react inside the reactor. The resulting reaction oil leaves the reactor through the conveying pipe at the top of the reactor and undergoes gas-solid separation. The separated carbonized catalyst is stripped and then introduced into the regenerator for regeneration. The regenerated catalyst is returned to the dense phase fluidized bed reactor for recycling through the regenerator conveying pipe.

[0007] The separated oil and gas products are further separated to obtain low-carbon olefins;

[0008] The average solid content of the catalyst in the dense phase fluidized bed reactor is 0.2-0.7, and the catalyst solid content has a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction. The axial height of the region in the dense phase fluidized bed reactor with a catalyst solid content greater than 0.3 accounts for 1 / 10 or more of the total height of the dense phase fluidized bed reactor.

[0009] The phrase "the catalyst solid content exhibits a gentle gradient distribution that gradually decreases from bottom to top along the axial direction" means that, in the curve of catalyst solid content G versus the ratio of the height h from the bottom of the reactor to the total height H of the reactor, within the range of h / H of 10%-90%, the difference ΔG between any two points where h / H differs by 10% is no greater than 0.2.

[0010] In one embodiment, the average solid content of the catalyst in the dense phase fluidized bed reactor is 0.3-0.5, and the axial height of the region with a catalyst solid content greater than 0.3 accounts for 1 / 5-4 / 5 of the total height of the dense phase fluidized bed reactor.

[0011] In one embodiment, the axial height of the region with a catalyst solids content > 0.5 accounts for 0 to 2 / 5 of the total height of the dense phase fluidized bed reactor, the axial height of the region with a catalyst solids content of 0.3 to 0.5 accounts for 1 / 5 to 4 / 5 of the total height of the dense phase fluidized bed reactor, and the catalyst solids content in the remaining regions is less than 0.3.

[0012] In one embodiment, the height-to-diameter ratio of the dense phase fluidized bed reactor is 0.5-20:1, preferably 2-10:1.

[0013] In one embodiment, the dense phase fluidized bed reactor is provided with a catalyst feed port and a catalyst discharge port. The catalyst feed port is located above the catalyst discharge port and is at least 1 / 2 of the total height of the dense phase fluidized bed reactor at a height above the bottom of the reactor. The catalyst discharge port is at 0-1 / 2 of the total height of the reactor at a height above the bottom of the reactor.

[0014] The catalyst is fed in through the catalyst replenishment port, a portion of the carbonized catalyst is discharged through the catalyst unloading port, and the catalyst flowing out of the catalyst unloading port is stripped and then introduced into the regenerator for regeneration.

[0015] In one embodiment, the height of the catalyst feed inlet from the bottom of the dense-phase fluidized bed reactor is 3 / 5 to 4 / 5 of the total height of the reactor; and / or

[0016] The height of the catalyst discharge port from the bottom of the dense phase fluidized bed reactor is 1 / 10 to 3 / 10 of the total height of the dense phase fluidized bed reactor.

[0017] In one embodiment, the mass ratio of the supplementary catalyst fed through the catalyst replenishment port to the regenerated catalyst fed through the regenerator delivery pipe is 0.01-1:1, preferably 0.1-0.5:1;

[0018] The flow rates of the supplementary catalyst input through the catalyst replenishment port and the catalyst flowing out through the catalyst discharge port are approximately equal.

[0019] In one embodiment, the supplementary catalyst is one or more of the following: a regenerated catalyst, a spent catalyst, a fresh catalyst, and a balanced catalyst.

[0020] Preferably, the catalyst feed port is connected to the regenerator via a catalyst feed pipe, so that the regenerated catalyst from the regenerator is fed into the dense phase fluidized bed reactor through the catalyst feed port.

[0021] In one embodiment, the reaction conditions of the dense phase fluidized bed reactor are: reaction temperature 500-750℃, reaction pressure 0.10-0.20MPa, agent-to-oil mass ratio 5-50:1, water-to-oil mass ratio 0.1-1:1, and oil-to-agent contact time 0.1-20 seconds; preferably, the reaction conditions of the dense phase fluidized bed reactor are: reaction temperature 600-700℃, reaction pressure 0.11-0.14MPa, agent-to-oil mass ratio 10-30:1, water-to-oil mass ratio 0.3-0.6:1, and oil-to-agent contact time 1-10 seconds.

[0022] In one embodiment, the catalyst comprises 10-80 wt% clay, 10-80 wt% inorganic oxide, and 10-80 wt% zeolite, wherein the clay serves as a matrix (i.e., a carrier) and is selected from one or a mixture of several of kaolinite, hydrous kaolinite, sepiolite, attapulgite, montmorillonite, and leucite; the inorganic oxide serves as a binder and is selected from one or a mixture of several of alumina, silica, amorphous aluminosilicate, and aluminum phosphophosphate sol; the zeolite is selected from one or more of ZSM series zeolites, β series zeolites, and Y series zeolites, and the zeolite is optionally modified with non-metallic elements such as phosphorus and / or metallic elements such as iron, cobalt, nickel, magnesium, calcium, and rare earth elements.

[0023] In one embodiment, the catalyst comprises 15-70 wt% clay, 15-70 wt% inorganic oxide, and 15-70 wt% zeolite, wherein the clay is preferably kaolin and / or hydrous kaolin; the inorganic oxide is preferably silicon dioxide (SiO2) and / or aluminum oxide (Al2O3); and the zeolite is preferably one or more of ZSM-5 zeolite, β-zeolite, and Y-type zeolite modified with non-metallic elements such as phosphorus and / or metallic elements such as iron, magnesium, calcium, and rare earth elements.

[0024] In one embodiment, the feedstock oil is one or more of petroleum hydrocarbons, animal and vegetable oils, synthetic oils, and biomass, wherein the petroleum hydrocarbons are petroleum hydrocarbons with a carbon number of 4 or more.

[0025] Compared with existing technologies, the method provided by this invention uses a dense-phase fluidized bed reactor. By controlling the average solid content and solid content distribution of the catalyst within the dense-phase fluidized bed reactor, the contact probability between hydrocarbon molecules and the active sites of the catalyst can be significantly increased, thereby significantly increasing the proportion of catalytic cracking reactions and reducing the degree of thermal cracking reactions. This allows for the achievement of high ethylene and propylene yields while significantly reducing methane yield. Furthermore, by setting a catalyst feed port at the top of the reactor and a catalyst discharge port at the bottom, the concentration and uniformity of the catalyst within the reactor can be flexibly adjusted, further significantly improving the yields of ethylene and propylene. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0027] Figure 1 This is a schematic diagram of a specific embodiment of the method of the present invention.

[0028] Figure 2 This is a schematic diagram of another specific embodiment of the present invention.

[0029] Figure 3 This is the distribution curve of catalyst solid content in the reactor as a function of height h / H in Example 1.

[0030] Figure 4 This is a schematic diagram illustrating the reaction mechanism of Comparative Example 2.

[0031] Figure 5 This is the distribution curve of catalyst solid content in the reactor of Comparative Example 2 as a function of height h / H.

[0032] Figure 6 This is the distribution curve of catalyst solid content in the reactor as a function of height h / H in Example 3.

[0033] Marker explanation:

[0034] 1. Dense Phase Fluidized Bed Reactor

[0035] 11 Raw material feed nozzle

[0036] 12 Pre-lift Steam Pipeline

[0037] 13 Oil Discharge Tube

[0038] 14 Catalyst replenishment inlet pipeline

[0039] 15 Catalyst outlet pipeline

[0040] 16 pre-lift pipe

[0041] 2 Regenerators

[0042] 21 Air delivery pipe

[0043] 22 Cyclone Separator

[0044] 23 Regenerated Flue Gas Conveying Pipe

[0045] 24 Regenerated Catalyst Delivery Pipe

[0046] 3 stripper

[0047] 31 Stripping Steam Conveying Pipe

[0048] 32 Catalyst Delivery Pipe

[0049] 4 settling devices

[0050] 41 Cyclone Separator

[0051] 42 Oil and gas output pipe Detailed Implementation

[0052] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0053] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0054] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0055] This application provides a method for catalytic cracking of hydrocarbons to produce ethylene and propylene, comprising:

[0056] Preheated feedstock oil and steam are introduced into the dense phase fluidized bed reactor from the bottom. They come into contact with the catalyst and react inside the reactor. The resulting reaction oil leaves the reactor through the conveying pipe at the top of the reactor and undergoes gas-solid separation. The separated carbonized catalyst is stripped and then introduced into the regenerator for regeneration. The regenerated catalyst is returned to the dense phase fluidized bed reactor for recycling through the regenerator conveying pipe.

[0057] The separated oil and gas products are further separated to obtain low-carbon olefins;

[0058] The average solid content of the catalyst in the dense phase fluidized bed reactor is 0.2-0.7, and the solid content of the catalyst exhibits a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction. Furthermore, the axial height of the region in the dense phase fluidized bed reactor with a catalyst solid content greater than 0.3 accounts for 1 / 10 or more of the total height of the dense phase fluidized bed reactor.

[0059] The method provided by this invention uses a dense-phase fluidized bed reactor for the catalytic cracking of hydrocarbon feedstock oils and controls the average solid content and solid content distribution of the catalyst in the dense-phase fluidized bed reactor. This can significantly increase the contact probability between hydrocarbon molecules and the active sites of the catalyst, thereby significantly increasing the proportion of catalytic cracking reaction and reducing the degree of thermal cracking reaction. As a result, while obtaining high ethylene and propylene yields, the methane yield can be significantly reduced.

[0060] In one embodiment, the average solid content of the catalyst in the dense phase fluidized bed reactor is 0.2-0.7, and the catalyst solid content exhibits a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction. Furthermore, the axial height of the region in the dense phase fluidized bed reactor with a catalyst solid content greater than 0.3 accounts for 1 / 10 or more of the total height of the dense phase fluidized bed reactor.

[0061] In one embodiment, the average solid content of the catalyst in the dense phase fluidized bed reactor is 0.3-0.5, and the axial height of the region with a catalyst solid content greater than 0.3 accounts for 1 / 5-4 / 5 of the total height of the dense phase fluidized bed reactor.

[0062] In one embodiment, the axial height of the region with a catalyst solids content > 0.5 accounts for 0 to 2 / 5 of the total height of the dense phase fluidized bed reactor, the axial height of the region with a catalyst solids content of 0.3 to 0.5 accounts for 1 / 5 to 4 / 5 of the total height of the dense phase fluidized bed reactor, and the catalyst solids content in the remaining regions is less than 0.3.

[0063] In this invention, the catalyst solid content = pressure difference between two points along the reactor axis measured by a differential pressure gauge ÷ distance between the two points along the axis ÷ catalyst particle density; wherein, the unit of pressure difference is kg / m³. 2 The distance between two points along the axis is measured in meters (m), and the catalyst particle density is measured in kg / m³.3 count.

[0064] The catalyst solids content in any height region within the reactor can be determined using the above method, and then the curve of catalyst solids content versus height from the bottom of the reactor can be determined. For the average catalyst solids content, the two selected axial points are the bottom and top of the reactor, respectively. The distance between them represents the height of the reactor, and the pressure difference between them represents the pressure difference between the top and bottom of the reactor.

[0065] Due to the effect of catalyst gravity, the catalyst solid content in the reactor typically decreases from bottom to top along the reactor axis. In this application, "the catalyst solid content exhibits a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction" means that, in the curve of catalyst solid content G versus the height h from the bottom of the reactor as a percentage of the total reactor height H, within the range of h / H being 10%-90%, the difference in catalyst solid content G between any two points where h / H differs by 10% is not greater than 0.2, or not greater than 0.15. For example, in the curve of catalyst solid content G versus h / H, the catalyst solid content at h1 / H is G1, and the catalyst solid content at h2 / H is G2. For any two points within the range of h / H (i.e., both h1 / H and h2 / H are within the range of 10%-90%), when (h2 / H-h1 / H = 10%), ΔG = G1-G2 ≤ 0.2 (or 0.15), where H refers to the total height of the reactor. That is, the catalyst solid content has a relatively gentle decreasing gradient, which allows the probability of contact between hydrocarbon molecules and the active sites of the catalyst to remain at a relatively high level during the reaction. This is beneficial for obtaining high ethylene and propylene yields while significantly reducing methane yield.

[0066] In one embodiment, the dense-phase fluidized bed reactor used in this application can be one or a combination of several types of fluidized beds with equal diameters and / or fluidized beds with varying diameters. In one embodiment, the dense-phase fluidized bed reactor is a fluidized bed with equal diameters, and its height-to-diameter ratio is 0.5-20:1, preferably 2-10:1. Figure 1 and Figure 2As shown, the bottom of the dense-phase fluidized bed reactor 1 is connected to the pre-lifting section 16. A pre-lifting steam pipeline is installed at the bottom of the pre-lifting section 16 for introducing the pre-lifting medium. The pre-lifting section 16 is connected to the regenerated catalyst pipeline 24, which transports the regenerated catalyst from the regenerator 2 into the pre-lifting section 16, where it moves upward under the lifting action of the pre-lifting medium and enters the dense-phase fluidized bed reactor 1. A feed oil nozzle 11 is installed on the pre-lifting section 16, located near the connection between the pre-lifting section 16 and the dense-phase fluidized bed reactor 1, for injecting feed oil and water vapor, thereby allowing the feed oil and water vapor to contact the catalyst in the dense-phase fluidized bed reactor for catalytic cracking. To facilitate the production of ethylene and propylene, the pre-lifting section 16 is typically relatively short, with a diameter ratio of 1:2-20 between the pre-lifting section 16 and the dense-phase fluidized bed reactor 1, and a height-to-diameter ratio of 2-20:1.

[0067] like Figure 1 and Figure 2 As shown, the top of the dense phase fluidized bed reactor 1 is connected to an oil outlet pipe 13, which is housed inside a settling tank 4. Its outlet is connected to a cyclone separator 41, allowing the reactant oil from the dense phase fluidized bed reactor 1 to be separated into a spent catalyst and oil / gas products in the cyclone separator 41 via the oil outlet pipe 13. The oil / gas products are then transported via an oil / gas output pipe 42 to a subsequent separation unit for further separation, yielding low-carbon olefins (e.g., ethylene and propylene). The spent catalyst is stripped in a stripper 3, using stripping steam as the stripping medium via a stripping steam delivery pipe 31. The stripped spent catalyst is then fed into a regenerator 2 via a spent catalyst delivery pipe 32 for regeneration. To minimize methane formation, the oil outlet pipe 13 also needs to be relatively short to reduce the thermal cracking of the reactant oil within the oil outlet pipe 13, which could lead to methane production. In one embodiment, the ratio of the diameter of the oil outlet pipe 13 to that of the dense phase fluidized bed reactor 1 is 1:1.5-30, and the height-to-diameter ratio of the oil outlet pipe 13 is 2-30:1.

[0068] The average solids content and solids content distribution of the catalyst within the dense-phase fluidized bed reactor can be controlled within the limits specified in this application by controlling the reactor structure (including the height-to-diameter ratio of the dense-phase fluidized bed reactor, the pre-lift section, and the oil outlet pipe, as well as the diameter ratio of the dense-phase fluidized bed reactor to the pre-lift section and the oil outlet pipe) and reaction process parameters such as the catalyst-to-oil mass ratio, the water-to-oil mass ratio, the reaction time, and the lift gas velocity. The inventors of this application have discovered that controlling the average solids content and solids content distribution of the catalyst within the dense-phase fluidized bed reactor within the limits specified in this application results in higher yields of dienes (ethylene + propylene) and lower yields of methane and coke.

[0069] In one implementation, such as Figure 2As shown, the dense phase fluidized bed reactor 1 is provided with a catalyst feed port 14 and a catalyst discharge port 15. The catalyst feed port 14 is located above the catalyst discharge port 15, and the height of the catalyst feed port 14 from the bottom of the dense phase fluidized bed reactor is more than 1 / 2 of the total height of the dense phase fluidized bed reactor. The height of the catalyst discharge port 15 from the bottom of the dense phase fluidized bed reactor is 0-1 / 2 of the total height of the dense phase fluidized bed reactor.

[0070] The catalyst is supplemented through catalyst feed port 14, a portion of the carbonized catalyst is discharged through catalyst discharge port 15, and the catalyst flowing out of catalyst discharge port 15 is stripped and then introduced into regenerator 2 for regeneration.

[0071] As set up above, a catalyst feed port 14 is provided at the top of the dense phase fluidized bed reactor 1, and a catalyst discharge port 15 is provided at the bottom of the reactor. This allows for flexible adjustment of the concentration and uniformity of the catalyst in the reactor, which can significantly improve the yield of ethylene and propylene.

[0072] In one embodiment, the catalyst feed port 14 is positioned at a height of 3 / 5 to 4 / 5 of the total height of the dense-phase fluidized bed reactor from the bottom of the reactor; and / or

[0073] The height of the catalyst discharge port 15 from the bottom of the dense phase fluidized bed reactor is 1 / 10 to 3 / 10 of the total height of the dense phase fluidized bed reactor.

[0074] In one embodiment, the mass ratio of the supplementary catalyst fed through the catalyst replenishment port to the regenerated catalyst fed through the regenerator delivery pipe is 0.01-1:1, preferably 0.1-0.5:1;

[0075] The flow rates of the supplementary catalyst input through the catalyst feed port and the catalyst outflow through the catalyst discharge port are approximately equal, thereby maintaining the material balance of the catalyst throughout the reactor.

[0076] In one embodiment, the supplementary catalyst is one or more of the following: regenerated catalyst, spent catalyst, fresh catalyst, and equilibrium catalyst; preferably, the catalyst replenishment port 14 is connected to the regenerator 2 through a catalyst replenishment pipe, so that the regenerated catalyst from the regenerator 2 is fed into the dense phase fluidized bed reactor 1 through the catalyst replenishment port 14.

[0077] In one embodiment, the reaction conditions of the dense phase fluidized bed reactor are: reaction temperature 500-750℃, reaction pressure 0.10-0.20MPa, agent-to-oil mass ratio 5-50:1, water-to-oil mass ratio 0.1-1:1, and oil-to-agent contact time 0.1-20 seconds; preferably, the reaction conditions of the dense phase fluidized bed reactor are: reaction temperature 600-700℃, reaction pressure 0.11-0.14MPa, agent-to-oil mass ratio 10-30:1, water-to-oil mass ratio 0.3-0.6:1, and oil-to-agent contact time 1-10 seconds.

[0078] The regenerator 2 is a conventional regenerator used for catalytic cracking, including an air delivery pipe 21, a cyclone separator 22, a regenerated flue gas delivery pipe 23, and is connected to the dense phase fluidized bed reactor 1 through a regenerated catalyst delivery pipe 24, for transporting the regenerated catalyst back to the dense phase fluidized bed reactor 1 for re-reaction.

[0079] In one embodiment, the catalyst comprises 10-80 wt% clay, 10-80 wt% inorganic oxide, and 10-80 wt% zeolite, wherein the clay serves as a matrix (i.e., a carrier) and is selected from one or a mixture of several of kaolinite, hydrous kaolinite, sepiolite, attapulgite, montmorillonite, and leucite; the inorganic oxide serves as a binder and is selected from one or a mixture of several of alumina, silica, amorphous aluminosilicate, and aluminum phosphophosphate sol; the zeolite is selected from one or more of ZSM series zeolites, β series zeolites, and Y series zeolites, and the zeolite is optionally modified with non-metallic elements such as phosphorus and / or metallic elements such as iron, cobalt, nickel, magnesium, calcium, and rare earth elements.

[0080] In one embodiment, the catalyst comprises 15-70 wt% clay, 15-70 wt% inorganic oxide, and 15-70 wt% zeolite, wherein the clay is preferably kaolin and / or hydrous kaolin; the inorganic oxide is preferably silicon dioxide (SiO2) and / or aluminum oxide (Al2O3); and the zeolite is preferably one or more of ZSM-5 zeolite, β-zeolite, and Y-type zeolite modified with non-metallic elements such as phosphorus and / or metallic elements such as iron, magnesium, calcium, and rare earth elements.

[0081] In one embodiment, the feedstock oil is one or more of petroleum hydrocarbons, animal and vegetable oils, synthetic oils, and biomass, wherein the petroleum hydrocarbons are petroleum hydrocarbons with a carbon number of 4 or more.

[0082] like Figure 1 In the illustrated embodiment, the hot regenerated catalyst is introduced into the pre-lifting section 16 through the regenerated catalyst delivery pipe 24 and flows upward under the action of the pre-lifting medium. Feed oil and steam are injected through the feed nozzle 11 and contact the regenerated catalyst to undergo catalytic cracking reaction in the dense phase fluidized bed reactor 1. After the reaction, the oil is separated from the catalyst in the settling tank 4 via the oil outlet pipe 13. The carbonized catalyst enters the stripper 3, where the hydrocarbon products adsorbed on the catalyst are stripped and then sent to the regenerator 2 for regeneration via the spent catalyst delivery pipe 32. The regenerated catalyst is returned to the dense phase fluidized bed reactor 1 for reuse. The separated oil and gas enter the subsequent separation system via the oil and gas outlet pipe 42 to separate target products such as low-carbon olefins like ethylene and propylene.

[0083] like Figure 2In the illustrated embodiment, the hot regenerated catalyst is introduced into the pre-lifting section 16 through the regenerated catalyst delivery pipe 24 and flows upward under the action of the pre-lifting medium. Feed oil and steam are injected through the feed nozzle 11 and contact the regenerated catalyst in the dense phase fluidized bed reactor 1 for catalytic cracking. The catalyst is replenished through the catalyst replenishment port 14 above the reactor and discharged through the catalyst discharge port 15 below the reactor. After the reaction, the oil is separated from the catalyst in the settling tank 4 via the oil discharge pipe 13. The carbonized catalyst enters the stripper 3, where the hydrocarbon products adsorbed on the catalyst are stripped and then sent to the regenerator 2 for regeneration via the spent catalyst delivery pipe 32. The regenerated catalyst is returned to the dense phase fluidized bed reactor 1 for reuse. The separated oil and gas enter the subsequent separation system via the oil and gas output pipe 42 to separate the target products, such as low-carbon olefins like ethylene and propylene.

[0084] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0085] The raw materials used in the examples and comparative examples were atmospheric residue oils, the properties of which are shown in Table 1. The properties of the catalysts used are shown in Table 2.

[0086] Table 1

[0087]

[0088] Table 2

[0089]

[0090] The molecular sieves, matrix, and binder for catalysts A and B were purchased from Sinopec Catalyst Qilu Branch. Catalyst A consisted of 30% phosphorus- and iron-modified ZSM-5 molecular sieves, 42% kaolin, and 28% Al2O3 binder. Catalyst B consisted of 35% phosphorus- and iron-modified ZSM-5 molecular sieves, 42% kaolin, and 23% SiO2 binder. The phosphorus modifier was ammonium dihydrogen phosphate, and the iron modifier was ferric nitrate. The molecular sieves, matrix, and binder were mixed and slurried, then sequentially spray-dried, washed, filtered, and dried. Catalyst A was aged at 800℃ with 100% steam for 2 hours before use, and catalyst B was aged at 800℃ with 100% steam for 17 hours before use.

[0091] Example 1

[0092] according to Figure 1The experiment was conducted using atmospheric residue oil as the feedstock and regenerated catalyst A as the catalyst. During the experiment, hot regenerated catalyst A was introduced to the bottom of the dense-phase fluidized bed reactor. Atmospheric residue oil and water vapor were sprayed into the bottom of the reactor through nozzles, contacting the regenerated catalyst A and undergoing catalytic cracking reaction in the reactor. The reacted oil was introduced into an oil separation system, and the separated reaction oil and gas entered a subsequent product separation system. The separated catalyst was stripped and then introduced into a regenerator for coke regeneration. The regenerated catalyst was returned to the dense-phase fluidized bed reactor for recycling. The unit used electric heating to maintain the temperature of the reaction and regeneration systems. The main operating conditions and results are listed in Table 3.

[0093] The structural parameters of the reactor are as follows:

[0094] The dense phase fluidized bed reactor is a constant diameter fluidized bed reactor with a height-to-diameter ratio of 6; the height-to-diameter ratio of the pre-lift section is 3, and its diameter is 1:8 compared to the diameter of the dense phase fluidized bed reactor; the height-to-diameter ratio of the oil outlet pipe is 5, and its diameter is 1:5 compared to the diameter of the dense phase fluidized bed reactor.

[0095] The average solids content of the catalyst in the dense-phase fluidized bed reactor is 0.3%, and the distribution curve of catalyst solids content with height is shown in the figure. Figure 3 As shown ( Figure 3 The horizontal axis h / H represents the ratio of the height h from the bottom of the reactor to the total height H of the reactor (the same applies below). The catalyst solid content shows a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction, and the axial height of the region with a catalyst solid content greater than 0.3 in the dense phase fluidized bed reactor accounts for 0.6 of the total height of the dense phase fluidized bed reactor.

[0096] Comparative Example 1

[0097] The raw materials and catalysts used, as well as the main implementation steps, are the same as in Example 1, except that a riser reactor is used. The main operating conditions and results are listed in Table 3.

[0098] Comparative Example 2

[0099] The raw materials, catalysts, and main implementation steps used are the same as in Example 1. The difference is that the catalyst enters the stripper directly from the bottom of the dense phase reactor, and the oil and gas leave the reactor through the conveying pipe at the top of the dense phase reactor, as detailed below. Figure 4 As shown. The hot regenerated catalyst is introduced into the dense-phase fluidized bed reactor 1 through the regenerated catalyst delivery pipe 24. Feed oil and steam are injected through the feed nozzle 11, contacting the regenerated catalyst and undergoing catalytic cracking in the dense-phase fluidized bed reactor 1. The carbonized catalyst enters the stripper 3, and stripping steam is input through the stripping steam delivery pipe 31 as the stripping medium, thereby stripping the hydrocarbon products adsorbed on the catalyst. The stripped catalyst is then sent to the regenerator 2 through the spent catalyst delivery pipe 32 for regeneration. The regeneration process is the same as... Figure 1As shown in the diagram, the regenerated catalyst is returned to the dense-phase fluidized bed reactor 1 for reuse. The reaction oil and gas enter the subsequent separation system via the oil and gas output pipe 42 to separate the target products, such as low-carbon olefins like ethylene and propylene.

[0100] The dense-phase fluidized bed reactor is a constant-diameter fluidized bed reactor with a height-to-diameter ratio of 6. The average solids content within the dense-phase fluidized bed reactor is 0.3%, and the catalyst solids content distribution curve with height is shown below. Figure 5 As shown, although the catalyst solid content also decreases from bottom to top along the axial direction, it drops sharply at h / H of 0.4-0.5.

[0101] Example 2

[0102] The raw materials and catalysts used, as well as the main implementation steps, are the same as in Example 1. The difference lies in the shape of the dense-phase fluidized bed and the operating conditions. The main operating conditions and results are listed in Table 3.

[0103] The structural parameters of the reactor are as follows:

[0104] The dense phase fluidized bed reactor is a constant diameter fluidized bed reactor with a height-to-diameter ratio of 3; the height-to-diameter ratio of the pre-lifting section is 3, and its diameter is 1:8 compared to the diameter of the dense phase fluidized bed reactor; the height-to-diameter ratio of the oil outlet pipe is 5, and its diameter is 1:5 compared to the diameter of the dense phase fluidized bed reactor.

[0105] The average solid content of the catalyst in the dense phase fluidized bed reactor is 0.35. The catalyst solid content exhibits a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction. Furthermore, the axial height of the region in the dense phase fluidized bed reactor with a catalyst solid content greater than 0.3 accounts for 0.5% of the total height of the dense phase fluidized bed reactor.

[0106] Table 3

[0107]

[0108] As shown in Table 3, although Comparative Example 2 also used a dense phase fluidized bed, the diene yield was relatively lower. It is speculated that this may be because there is a region of steep drop in catalyst solids content in the reactor. The rapid drop in catalyst solids content is not conducive to maintaining contact between the feedstock oil and the active center of the catalyst, thus leading to a decrease in diene yield.

[0109] Example 3

[0110] according to Figure 2The experiment was conducted using atmospheric residue oil as the feedstock and regenerated catalyst B as the catalyst. During the experiment, hot regenerated catalyst B was introduced to the bottom of the dense-phase fluidized bed reactor. Atmospheric residue oil and water vapor were sprayed into the bottom of the reactor through nozzles, contacting the regenerated catalyst B and undergoing catalytic cracking reaction in the reactor. A catalyst replenishment port was located above the reactor (in this embodiment, the catalyst replenishment port is connected to the regenerator for replenishing the regenerated catalyst), and a catalyst discharge port was located below. The reacted oil was introduced into an oil separation system, and the separated reaction oil and gas entered a subsequent product separation system. The separated catalyst was stripped and then introduced into the regenerator for coke regeneration. The regenerated catalyst was returned to the dense-phase fluidized bed reactor for recycling. The unit used electric heating to maintain the temperature of the reaction and regeneration systems. The main operating conditions and results are listed in Table 4.

[0111] The structural parameters of the reactor are as follows:

[0112] The dense-phase fluidized bed reactor is a constant-diameter fluidized bed reactor with a height-to-diameter ratio of 6. The pre-lift section has a height-to-diameter ratio of 3, and its diameter is 1:8 compared to the diameter of the dense-phase fluidized bed reactor. The oil outlet pipe has a height-to-diameter ratio of 5, and its diameter is 1:5 compared to the diameter of the dense-phase fluidized bed reactor. The distance from the catalyst feed port to the bottom is 7 / 10 of the fluidized bed height, and the distance from the catalyst discharge port to the bottom is 1 / 5 of the fluidized bed height.

[0113] The average solids content of the catalyst in the dense-phase fluidized bed reactor is 0.4%. The distribution curve of the catalyst solids content with height in the reactor is shown in the figure. Figure 6 As shown, the catalyst solid content exhibits a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction, and the axial height of the region with a catalyst solid content greater than 0.3 in the dense phase fluidized bed reactor accounts for 0.8% of the total height of the dense phase fluidized bed reactor.

[0114] Example 4

[0115] The raw materials and catalysts used, as well as the main implementation steps, are the same as in Example 3. The difference is that the catalyst is not replenished through the catalyst replenishment port, and a portion of the catalyst is not discharged through the catalyst discharge port. The main operating conditions and results are listed in Table 4.

[0116] The average solid content of the catalyst in the dense phase fluidized bed reactor is 0.3. The catalyst solid content exhibits a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction. Furthermore, the axial height of the region in the dense phase fluidized bed reactor with a catalyst solid content greater than 0.3 accounts for 0.5% of the total height of the dense phase fluidized bed reactor.

[0117] Example 5

[0118] The raw materials and catalysts used, as well as the main implementation steps, are the same as in Example 3. The difference lies in the location of the replenishment inlet and the amount of catalyst replenished in the dense phase fluidized bed reactor. The main operating conditions and results are listed in Table 4.

[0119] The dense-phase fluidized bed reactor is a constant-diameter fluidized bed reactor with a height-to-diameter ratio of 6. The pre-lift section has a height-to-diameter ratio of 3, and its height is 1:8 compared to the height of the dense-phase fluidized bed reactor. The oil outlet pipe has a height-to-diameter ratio of 5, and its diameter is 1:5 compared to the diameter of the dense-phase fluidized bed reactor. The distance from the catalyst feed port to the bottom is 3 / 5 of the fluidized bed height, and the distance from the catalyst discharge port to the bottom is 1 / 5 of the fluidized bed height.

[0120] The average solid content of the catalyst in the dense phase fluidized bed reactor is 0.4. The catalyst solid content exhibits a gentle gradient distribution along the axial direction, gradually decreasing from bottom to top. Furthermore, the axial height of the region with a catalyst solid content greater than 0.3 in the dense phase fluidized bed reactor accounts for 0.7% of the total height of the reactor.

[0121] Table 4

[0122]

[0123] Note: *“The mass ratio of supplementary catalyst to regenerated catalyst” refers to the mass ratio of supplementary catalyst input through the catalyst replenishment port to regenerated catalyst input through the regenerator delivery pipe.

[0124] As can be seen from the data in Tables 3 and 4, the hydrocarbon catalytic cracking method provided by this invention significantly improves the yields of ethylene and propylene while reducing the yield of methane. It should be noted that Example 4 has a lower diene yield compared to Examples 1 and 2 due to the lower activity of the catalyst used. However, as shown in Examples 3 and 5, by adding a catalyst feed port and a catalyst discharge port to the reactor, inputting a certain amount of supplementary catalyst through the catalyst feed port, and discharging approximately the same mass of catalyst through the catalyst discharge port to maintain catalyst material balance within the reactor, the diene yield can be significantly improved.

[0125] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0126] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A method for catalytic cracking of hydrocarbons to produce ethylene and propylene, comprising: Preheated feedstock oil and steam are introduced into the dense phase fluidized bed reactor from the bottom. They come into contact with the catalyst and react inside the reactor. The resulting reaction oil leaves the reactor through the conveying pipe at the top of the reactor and undergoes gas-solid separation. The separated coked catalyst is stripped and then introduced into the regenerator for regeneration. The regenerated catalyst is returned to the dense phase fluidized bed reactor for recycling through the regenerator conveying pipe. The separated oil and gas products are further separated to obtain ethylene and propylene; The average solid content of the catalyst in the dense phase fluidized bed reactor is 0.2-0.7, and the catalyst solid content has a gentle gradient distribution characteristic that gradually decreases from bottom to top along the axial direction. The axial height of the region in the dense phase fluidized bed reactor with a catalyst solid content greater than 0.3 accounts for 1 / 10 or more of the total height of the dense phase fluidized bed reactor. The phrase "the catalyst solid content exhibits a gentle gradient distribution that gradually decreases from bottom to top along the axial direction" means that, in the curve of catalyst solid content G versus the ratio of the height h from the bottom of the reactor to the total height H of the reactor, within the range of h / H of 10%-90%, the difference ΔG between any two points where h / H differs by 10% is no greater than 0.

2.

2. The method of claim 1, wherein, The average solid content of the catalyst in the dense phase fluidized bed reactor is 0.3-0.5, and the axial height of the region with a catalyst solid content greater than 0.3 accounts for 1 / 5-4 / 5 of the total height of the dense phase fluidized bed reactor.

3. The method according to claim 1, wherein, The axial height of the region with catalyst solids content > 0.5 accounts for 0 to 2 / 5 of the total height of the dense phase fluidized bed reactor, the axial height of the region with catalyst solids content 0.3 to 0.5 accounts for 1 / 5 to 4 / 5 of the total height of the dense phase fluidized bed reactor, and the catalyst solids content in the remaining regions is less than 0.

3.

4. The method according to claim 1, wherein, The height-to-diameter ratio of the dense phase fluidized bed reactor is 0.5-20:1, preferably 2-10:

1.

5. The method according to claim 1, wherein, The dense phase fluidized bed reactor is equipped with a catalyst feed port and a catalyst discharge port. The catalyst feed port is located above the catalyst discharge port, and its height from the bottom of the dense phase fluidized bed reactor is more than 1 / 2 of the total height of the dense phase fluidized bed reactor. The height from the bottom of the dense phase fluidized bed reactor is 0-1 / 2 of the total height of the dense phase fluidized bed reactor. The catalyst is fed in through the catalyst replenishment port, a portion of the carbonized catalyst is discharged through the catalyst unloading port, and the catalyst flowing out of the catalyst unloading port is stripped and then introduced into the regenerator for regeneration.

6. The method according to claim 5, wherein, The height of the catalyst feed inlet from the bottom of the dense-phase fluidized bed reactor is 3 / 5 to 4 / 5 of the total height of the reactor; and / or The height of the catalyst discharge port from the bottom of the dense phase fluidized bed reactor is 1 / 10 to 3 / 10 of the total height of the dense phase fluidized bed reactor.

7. The method according to claim 5, wherein, The mass ratio of the supplementary catalyst input through the catalyst replenishment port to the regenerated catalyst input through the regenerator delivery pipe is 0.01-1:1, preferably 0.1-0.5:1; The flow rates of the supplementary catalyst input through the catalyst replenishment port and the catalyst flowing out through the catalyst discharge port are approximately equal.

8. The method according to claim 5, wherein, The supplementary catalyst can be one or more of the following: regenerated catalyst, spent catalyst, fresh catalyst, and equilibrium catalyst. Preferably, the catalyst feed port is connected to the regenerator via a catalyst feed pipe, so that the regenerated catalyst from the regenerator is fed into the dense phase fluidized bed reactor through the catalyst feed port.

9. The method according to claim 1, wherein, The reaction conditions for the dense phase fluidized bed reactor are: reaction temperature 500-750℃, reaction pressure 0.10-0.20MPa, agent-to-oil mass ratio 5-50:1, water-to-oil mass ratio 0.1-1:1, and oil-to-agent contact time 0.1-20 seconds; the preferred reaction conditions for the dense phase fluidized bed reactor are: reaction temperature 600-700℃, reaction pressure 0.11-0.14MPa, agent-to-oil mass ratio 10-30:1, water-to-oil mass ratio 0.3-0.6:1, and oil-to-agent contact time 1-10 seconds.

10. The method according to claim 1, wherein, The catalyst comprises 10–80 wt% clay, 10–80 wt% inorganic oxides, and 10–80 wt% zeolite, wherein the clay serves as a matrix (i.e., a carrier) and is selected from one or a mixture of several of kaolinite, hydrous kaolinite, sepiolite, attapulgite, montmorillonite, and leucite; the inorganic oxides serve as a binder and are selected from one or a mixture of several of alumina, silica, amorphous aluminosilicate, and aluminum phosphophosphate sol; the zeolite is selected from one or a mixture of several of ZSM series zeolites, β series zeolites, and Y series zeolites, and the zeolite is optionally modified by non-metallic elements such as phosphorus and / or metallic elements such as iron, cobalt, nickel, magnesium, calcium, and rare earth elements.

11. The method according to claim 10, wherein, The catalyst comprises 15-70 wt% clay, 15-70 wt% inorganic oxides, and 15-70 wt% zeolite, wherein the clay is preferably kaolin and / or hydrous kaolin; the inorganic oxide is preferably silicon dioxide (SiO2) and / or aluminum oxide (Al2O3); and the zeolite is preferably one or more of ZSM-5 zeolite, β-zeolite, and Y-type zeolite modified with non-metallic elements such as phosphorus and / or metallic elements such as iron, magnesium, calcium, and rare earth elements.

12. The method according to claim 1, wherein, The raw material oil is one or more of petroleum hydrocarbons, animal and vegetable oils, synthetic oils, and biomass, wherein the petroleum hydrocarbons are petroleum hydrocarbons with a carbon number of 4 or more.

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