Catalytic cracking method for preparing low-carbon olefin

Abstract

A catalytic cracking method for preparing a low-carbon olefin. The method comprises the following steps: contacting a hydrocarbon raw material with a catalyst at a temperature of 600°C-800°C in a catalytic cracking reactor, and performing a catalytic cracking reaction to obtain a reactant fluid containing a low-carbon olefin-containing reaction oil gas and a spent catalyst; cooling the reactant fluid after reaction to 450°C-530°C in a cooling zone; and separating the cooled reactant fluid to obtain a low-carbon olefin. The temperature drop of the reactant fluid in the reaction process is controlled, so that the impact of the temperature drop on the raw material cracking reaction process is weakened, single-molecule cracking of the raw material is promoted, and the yield of the low-carbon olefin in the product is increased, thereby achieving efficient utilization of the raw material.

Description

Catalytic cracking method for preparing light olefins Technical Field

[0001] The present invention belongs to the field of petroleum processing, and in particular, relates to a catalytic cracking method for preparing ethylene, and more particularly, to a method for increasing the production of light olefins by controlling temperature changes in a catalytic cracking reaction. Background Art

[0002] Light olefins are important petrochemical feedstocks. Common technologies for producing light olefins include steam cracking, catalytic cracking, olefin cracking, and methanol-to-olefins. The operation of a catalytic cracking unit involves a heat balance of periodic heat supply and heat removal. During the catalytic cracking reaction, coke deposited on the catalyst burns in the regenerator, generating heat. This heat is carried by the regenerated catalyst to the reactor, where it is used to heat the feedstock and provide heat for the cracking reaction.

[0003] Catalytic cracking reaction is a strong endothermic process. Conventional catalytic cracking reaction heat is about 180 to 300 kJ / kg of crude oil. Catalytic cracking technology for producing light olefins, such as deep catalytic cracking process (DCC) and catalytic thermal cracking process (CPP), has a greater demand for heat, and the cracking reaction heat can reach 600-800 kJ / kg of raw material. On the other hand, the smaller the molecules in the raw material, the heat required for the reaction will increase accordingly. For example, when producing light olefins using naphtha or olefins with a carbon number not higher than 12, a higher heat of reaction is required. In order to meet the required heat of reaction, the method commonly used in the prior art is to increase the catalyst-to-oil ratio. However, a high catalyst-to-oil ratio usually brings about the problem of increasing the production of coke and dry gas yield. To this end, those skilled in the art propose to replace some conventional catalytic cracking catalysts with inert carriers, such as using amorphous aluminum silicate, coal powder and catalytic cracking waste catalyst as heat carriers in CN101580733A. There are also some methods that focus on meeting the overall heat demand of the catalytic cracking reactor. For example, US6558530 adopts the method of gasifying the raw materials before injecting them into the reactor; US7572362 uses sand as a heat carrier to pretreat the raw materials before feeding them into the reactor.

[0004] During actual production, after the heat carried by the regenerated catalyst contributes to the feedstock heating and reaction heat, its temperature drops below the optimal temperature required for feedstock conversion. At this point, if the initial temperature of the regenerated catalyst is raised to maintain the reaction temperature, the initial catalytic cracking reaction will occur when the regenerated catalyst contacts the feedstock, causing the reaction temperature to rise above the optimal temperature again, increasing byproducts. Therefore, in the production of light olefins, maintaining the catalyst within the optimal temperature range for feedstock conversion during the reaction is crucial, as it impacts the reaction type and corresponding product distribution in the actual process.

[0005] Summary of the Invention

[0006] In the face of the above-mentioned existing technical problems, the inventors of the present invention have conducted in-depth research and found that by controlling the temperature history during the catalytic cracking reaction, especially controlling the changes in temperature drop during the reaction, the hydrocarbon raw materials can be kept in the optimal temperature range during the catalytic cracking reaction, thereby improving the yield of light olefins and reducing the generation of by-products such as dry gas, thereby solving the above-mentioned technical problems. Furthermore, the inventors of the present invention have found that while controlling the changes in temperature drop during the reaction, by cooling the post-reaction reaction flow at a specific position and controlling the temperature of the reaction flow, the thermal cracking reaction occurring in the post-reaction reaction flow can be further suppressed, and the generation of by-products such as dry gas can be further reduced. Thus, the present invention is completed. In order to achieve the above-mentioned purpose, the present invention provides a catalytic cracking method for preparing light olefins, which comprises the following steps:

[0007] In the catalytic cracking reactor, the hydrocarbon feedstock is brought into contact with the catalyst at a temperature of 600-800°C to produce a catalytic cracking reaction, thereby obtaining a reaction stream containing reaction oil and gas containing light olefins and a spent catalyst.

[0008] The reactant flow after the reaction is cooled to 450-530°C in a cooling zone, and the cooled reactant flow is separated to obtain light olefins, wherein the length from the position where the hydrocarbon feedstock starts to contact the catalyst to the starting position of the cooling zone is evenly divided into n sections (n ​​is 5 or more, preferably 10 or more, more preferably 15 or more, and particularly preferably 20 or more), and according to the direction of the reactant flow, when the reactant flow passes through the xth section (2≤x≤n) of the n sections, the temperature drop ΔTx of the reactant flow in the xth section satisfies ΔTx≤ΔTx-1, and the temperature drop of the reactant flow in the first section ΔT1≤150 / n, preferably ΔT1≤100 / n, further preferably ΔT1≤80 / n, and more preferably ΔT1≤50 / n.

[0009] Optionally, in the present invention, according to the direction of the reactant flow, the total temperature drop ΔT1+ΔT2 of the reactant flow when passing through the first and second sections of the n sections is ≤280°C / n, preferably the total temperature drop ΔT1+ΔT2≤180°C / n, further preferably the total temperature drop ΔT1+ΔT2≤150°C / n, and more preferably the total temperature drop ΔT1+ΔT2≤80°C / n.

[0010] Optionally, in the present invention, the difference between the temperature of the reactant stream when entering the cooling zone and the initial temperature of the reactant feed when contacting the catalyst is 20-100°C, preferably the temperature difference is 30-90°C.

[0011] Optionally, in the present invention, the conditions for the catalytic cracking reaction include: at a catalyst density of 100-700 kg / m 3 , preferably 300-600kg / m3 , more preferably 400-500kg / m 3 A catalytic cracking reaction is carried out in a dense phase fluidized bed; and / or

[0012] Setting a cooling zone at a position where the catalyst density is reduced to 80% to 20% of the catalyst density in the dense fluidized bed, preferably setting a cooling zone at a position where the catalyst density is reduced to 70% to 30% of the catalyst density in the dense fluidized bed; and / or

[0013] In the cooling zone, a cooling medium distributor is used for cooling; or a heat collector is used for cooling, and the cooling medium in the cooling medium distributor or the heat collector is at least one selected from liquefied gas, crude gasoline, stabilized gasoline, diesel, heavy diesel and water.

[0014] Through the above technical solution, the present invention has the following beneficial effects:

[0015] (1) The present invention can effectively control the reaction temperature drop during the catalytic cracking reaction, especially the period from when the catalyst contacts the reaction feed to when the reactant stream is cooled. The temperature drop of the catalytic cracking reaction can be controlled within a specific range. Thus, the bimolecular cracking and hydrogen transfer reactions caused by excessive catalyst temperature drop during the catalytic cracking reaction are effectively suppressed, the yield of light olefins, especially ethylene, in the product is increased, and the efficient utilization of the feedstock is promoted.

[0016] (2) In the present invention, by rapidly cooling the stream after the catalytic cracking reaction in the cooling zone, the control of the catalytic cracking reaction and the thermal cracking reaction is optimized, the thermal cracking reaction during the reaction process can be effectively suppressed, the generation of by-products such as methane is reduced, and the yield and selectivity of light olefins are improved;

[0017] (3) In the present invention, the logistics after the catalytic reaction enters the cooling step at a specific position for cooling, which effectively inhibits the thermal cracking reaction during the reaction process and reduces the generation of by-products such as methane, thereby improving the yield and selectivity of light olefins.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0020] FIG1 is a schematic diagram of a catalytic cracking process according to an embodiment of the present invention.

[0021] Description of Reference Numerals

[0022] 1 pipeline 2 reactor 3 pipeline

[0023] 4 pipelines 5 pipelines 6 pipelines

[0024] 7 outlet section 8 settler 9 gas collecting chamber

[0025] 10 stripping section 11 pipeline 12 waiting for production inclined pipe

[0026] 13 regenerator 14 pipeline 15 cyclone separation system

[0027] 16 pipeline 17 energy recovery system 18 heat exchanger

[0028] 19 Regeneration inclined tube 20 Large oil and gas pipeline 21 Product fractionation unit DETAILED DESCRIPTION

[0029] Hereinafter, specific embodiments of the present invention will be described in detail. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the appended claims.

[0030] In the context of this specification, except for the contents explicitly stated, any matters or issues not mentioned are directly applicable to those known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are considered part of the original disclosure or original description of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0031] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless the weight basis does not conform to the general understanding of those skilled in the art.

[0032] The specific embodiments of the present invention are described in detail below. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0033] In the context of the present invention, unless otherwise specified, the physical properties of a substance (such as boiling point) are all measured values ​​at normal temperature (25° C.) and normal pressure (101325 Pa).

[0034] After extensive research, the inventors discovered that in processes for producing light olefins from hydrocarbon feedstocks (particularly olefin-rich feedstocks), the highly endothermic nature of the catalytic cracking reaction prevents the reaction temperature from being maintained within the optimal temperature range. Increasing the initial temperature of the regenerated catalyst also results in excessively high initial reaction temperatures, leading to an increase in side reaction products. Furthermore, as the reaction proceeds, the temperature of the reactants gradually drops below the optimal reaction temperature. When the temperature drops significantly, the olefin feedstock is susceptible to polymerization, and the cracking pattern of the light feedstock gradually shifts from a unimolecular cracking pathway to a bimolecular cracking pathway. This results in a decrease in the yield of ethylene and other products, while increasing the yield of high-carbon olefins.

[0035] Therefore, the inventors of the present invention have controlled the temperature history during the reaction process, particularly the reaction temperature drop from the time the catalyst contacts the reaction raw materials to the time the reaction stream is cooled, so that the temperature drop meets the specific range of the present invention. This allows the reaction raw materials to be maintained within an optimal temperature range during the catalytic cracking reaction, particularly during the critical initial period of the catalytic cracking reaction, thereby increasing the yield of light olefins and reducing the formation of by-products such as dry gas. Furthermore, the inventors of the present invention have discovered that while controlling the temperature drop during the reaction process, by controlling the temperature of the post-reaction reaction stream, causing the post-reaction reaction stream to rapidly cool in the cooling zone, the thermal cracking reaction occurring in the post-reaction reaction stream can be further suppressed, further reducing the formation of by-products such as dry gas.

[0036] Specifically, the present invention provides a catalytic cracking method for preparing ethylene, which comprises the following steps:

[0037] In the catalytic cracking reactor, the hydrocarbon feedstock is brought into contact with the catalyst at a temperature of 600-800°C to produce a catalytic cracking reaction, thereby obtaining a reaction stream containing reaction oil and gas containing light olefins and a spent catalyst.

[0038] The reaction flow after the reaction is cooled to 450-530°C in a cooling zone, and the cooled reaction flow is separated to obtain light olefins, wherein the length from the position where the hydrocarbon raw material (also referred to as the reaction raw material in the present invention) starts to contact the catalyst to the starting position of the cooling zone is evenly divided into n sections (n ​​is 5 or more, preferably 10 or more, more preferably 15 or more, and particularly preferably 20 or more), according to the direction of the reaction flow, when the reaction flow passes through the xth section (2≤x≤n) of the n sections, the temperature drop ΔTx of the reaction flow in the xth section satisfies ΔTx≤ΔTx-1, and the temperature drop of the reaction flow in the first section ΔT1≤150 / n, preferably ΔT1≤100 / n, further preferably ΔT1≤80 / n, and more preferably ΔT1≤50 / n.

[0039] In the present invention, by regulating the temperature drop of the reactant flow from the position where the reaction raw materials start to contact the catalyst to the starting position of the cooling zone, the catalytic cracking reaction can be kept in a suitable temperature range, thereby achieving the purpose of the present invention.

[0040] In the present invention, the length from the point where the reaction raw materials begin to contact the catalyst to the starting point of the cooling zone (this length is sometimes referred to as the reaction length in the present invention) is divided into n sections. By controlling the temperature drop in each section, especially the temperature drop during the critical initial period of the catalytic cracking reaction, the catalytic cracking reaction can be maintained within the optimal temperature range, the type of reaction can be regulated, and the yield of light olefins, especially the yield of ethylene, can be increased.

[0041] In the present invention, the reaction length is divided into n sections, wherein n is 5 or more, preferably 8 or more, more preferably 10 or more, more preferably 15 or more, and particularly preferably 20 or more. According to the direction of the reactant flow, when the reactant flow passes through the xth section (2≤x≤n) in the n sections, the temperature drop of the reactant flow in the xth section is ΔTx. At this time, the temperature drop ΔTx is the difference between the temperature of the starting point of the xth section and the temperature of the end point of the xth section. In the present invention, a temperature monitoring device can be set at the starting point of the xth section and the end point of the xth section to detect the temperature. Therefore, the larger n is, the more interval segments are divided. In theory, the larger n is, the more preferred, but from a practical point of view, n can be less than 50, less than 30 or less than 25.

[0042] The method for measuring the starting and ending temperatures of each segment in the reaction length is not particularly limited and can be employed by methods known in the art. For example, a temperature probe or temperature sensor can be positioned at a point that divides the reaction length into n equal segments, and the temperature at that point can be measured. Alternatively, a temperature probe or temperature sensor can be positioned at the n+1th dividing point, and the difference between the temperatures measured at two adjacent dividing points defining a segment can be taken as the temperature drop for that segment.

[0043] In the present invention, temperature control during the initial stage of contact between the catalyst and the reaction raw materials is particularly important. Therefore, in one embodiment of the present invention, the temperature drop of the reactant stream during passage through the first of the n stages is ΔT1 ≤ 150 / n, preferably ΔT1 ≤ 100 / n, more preferably ΔT1 ≤ 80 / n, and even more preferably ΔT1 ≤ 50 / n, depending on the direction of the reactant stream.

[0044] Because temperature control is particularly important in the initial stage of contact between the catalyst and the reaction raw materials, in one embodiment of the present invention, according to the direction of the reactant flow, the total temperature drop ΔT1+ΔT2 when the reactant flow passes through the first and second sections of the n sections is ≤280°C / n, preferably the total temperature drop ΔT1+ΔT2 is ≤180°C / n, further preferably the total temperature drop ΔT1+ΔT2 is ≤150°C / n, and more preferably the total temperature drop ΔT1+ΔT2 is ≤80°C / n.

[0045] On the other hand, the inventors discovered that during the high-temperature cracking reaction of hydrocarbon feedstocks, catalytic cracking and thermal cracking are competing reactions. By inhibiting the thermal cracking reaction, the formation of dry gas, represented by methane, in the product can be effectively suppressed, and the proportion of light olefins in the product can be increased. Therefore, by using a dense-phase fluidized bed and maintaining it at a specific reaction temperature, the occurrence of thermal cracking can be effectively suppressed, the formation of byproducts such as methane can be reduced, and the yield and selectivity of light olefins can be improved.

[0046] Furthermore, the inventors of the present invention have discovered that by providing a cooling zone at a specific location in the reactor to cool the reactant stream after the catalytic cracking reaction, the thermal cracking reaction during the reaction process can be effectively suppressed, thereby improving the yield and selectivity of light olefins. Specifically, after in-depth research, the inventors of the present invention have discovered that when the cooling zone is located too upstream after the catalytic cracking reaction, the cooling zone may intrude into the catalytic cracking reaction zone, affecting the temperature of the catalytic cracking reaction, resulting in the formation of large molecular olefin products, and affecting the selectivity and yield of light olefin products. On the other hand, when the cooling zone is located too downstream after the catalytic cracking reaction, the reactant stream in the catalyst dilute phase region is at a high temperature, but is not in sufficient contact with the catalyst, resulting in insufficient suppression of the thermal cracking reaction, thereby affecting the yield and selectivity of light olefins.

[0047] The inventors of the present invention have conducted in-depth research and exploration on this issue and found that when the catalyst density is 100-700 kg / m 3Downstream of the dense fluidized bed, a cooling zone is provided at a position where the catalyst density is reduced to 80% to 20% of the catalyst density in the dense fluidized bed, preferably to 70% to 30% of the catalyst density in the dense fluidized bed, to cool the reactant stream after the reaction (this cooling step is sometimes also referred to as a cooling step in the present invention). This effectively suppresses thermal cracking reactions in the reactant stream after the catalytic cracking reaction, thereby improving the yield and selectivity of light olefins.

[0048] In other words, in the present invention, the catalytic cracking reactor includes a catalyst having a density of 100-700 kg / m 3 A cooling zone is set in the bed layer of the dense fluidized bed along the downstream position of the dense fluidized bed in the direction of the reactant flow, at a position where the catalyst density is reduced to 80%-20% of the catalyst density in the bed layer of the dense fluidized bed, preferably to 70%-30% of the catalyst density in the bed layer of the dense fluidized bed, and the flow from the dense fluidized bed after the catalytic cracking reaction is cooled to 450-530°C, preferably to 480-500°C.

[0049] In the present invention, a cooling zone is set at a position where the catalyst density drops to a specific range. The reactant flow after the reaction enters the cooling zone and is cooled. After being cooled to 450-530°C, the thermal cracking reaction of the reactant flow is fully suppressed.

[0050] Therefore, in the present invention, "providing a cooling zone at a location where the catalyst density drops to a specific range" means providing a cooling zone at any location within the region where the catalyst density drops to a specific range, rather than defining that region as the cooling zone. In fact, in the present invention, there is no intended limitation on the length of the cooling zone in the direction of the reactant flow; as long as the temperature can be rapidly reduced (e.g., within 0.5-2 seconds, or within 0.5-1 second) to cool the reactant flow to 450-530°C (preferably 480-500°C), it will suffice.

[0051] As used herein, a "dense-phase fluidized bed" refers to the catalyst reservoir region in a catalytic cracking reactor. A lifting medium is used to concentrate the catalyst in this region. The position of this bed can be varied by varying the lifting medium flow rate, the reactant flow rate, the amount of catalyst, and the like. Based on common knowledge in the art, those skilled in the art can readily identify a dense-phase fluidized bed.

[0052] As used herein, "catalyst density in a dense fluidized bed" refers to the catalyst density in the catalyst inventory region of a catalytic cracking reactor. In this catalyst inventory region, the balance between the feed of catalyst and / or regenerated catalyst and the discharge of spent catalyst entrained in the post-reaction stream maintains a substantially constant catalyst inventory. Therefore, the catalyst density in the dense fluidized bed remains substantially constant. Those skilled in the art can adjust the catalyst density in the dense fluidized bed as needed by methods known in the art. For example, the catalyst density in the dense fluidized bed can be adjusted based on the catalyst dosage, the flow rate of the lift medium, the diameter / height ratio of the fluidized bed section, and the like.

[0053] In the present invention, the light olefin is at least one of ethylene and propylene. The reaction oil gas containing light olefins of the present invention generally comprises a mixture of ethylene and propylene. In addition, in the present invention, butene can also be optionally used as a kind of light olefin, particularly when using an olefin raw material with a higher number of carbon atoms (e.g., an olefin above C5). On the other hand, butene can also be optionally used as a kind of hydrocarbon raw material, particularly when preparing a lower number of olefins (e.g., ethylene and propylene). Those skilled in the art will make the selection according to the actual situation.

[0054] In one embodiment of the present invention, the difference between the temperature of the reactant stream when entering the cooling zone and the initial temperature of the reaction raw materials when contacting the catalyst (i.e., the temperature of the catalyst entering the reactor) is 20-100°C, preferably 30-90°C.

[0055] In one embodiment of the present invention, the difference between the temperature of the reactant stream when entering the cooling zone and the initial temperature of the reaction raw materials when contacting the catalyst can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C or any value within the foregoing range.

[0056] In one embodiment of the present invention, the conditions for the catalytic cracking reaction include: the raw material and the catalyst are in contact at a temperature of 620-720° C. to cause catalytic cracking.

[0057] In one embodiment of the present invention, the reaction pressure of the catalytic cracking reaction is 0.05 to 1 MPa, preferably 0.1 to 0.8 MPa.

[0058] In one embodiment of the present invention, the reaction time of the catalytic cracking reaction is 0.1 to 80 seconds, preferably 0.5 to 70 seconds.

[0059] In one embodiment of the present invention, the mass ratio of the catalytic cracking catalyst to the raw material is (3-180):1, preferably (10-150):1. By adopting the above reaction conditions, the cracking reaction of the light raw material can be ensured to proceed smoothly.

[0060] It should be noted that the above reaction conditions can be adjusted according to needs (eg, different types of reactors).

[0061] In one embodiment of the present invention, the reaction flow containing reaction oil and gas containing light olefins and the catalyst to be generated after the catalytic cracking reaction in the reactor is cooled in a cooling zone to below 530°C in 0.5-2 seconds, preferably in 0.5-1 second, preferably to 450-530°C, and further preferably to 480-500°C.

[0062] In the method for producing light olefins from hydrocarbon feedstocks of the present invention, the temperature reduction performed in the cooling zone is also referred to as a cooling step.

[0063] In the cooling step of the present invention, there is no limitation on the means for cooling the temperature, and means known in the art may be used, such as cooling the temperature using a heat exchanger, cooling the temperature by introducing a cooling medium, etc.

[0064] In one embodiment of the present invention, in the cooling step, the temperature is lowered by using a cooling medium distributor.

[0065] In one embodiment of the present invention, in the cooling step, a heat extractor is used for cooling.

[0066] In one embodiment of the present invention, in the cooling step, the cooling medium in the cooling medium distributor or the heat extractor is at least one selected from liquefied gas, crude gasoline, stabilized gasoline, diesel, heavy diesel and water.

[0067] In one embodiment of the present invention, in the cooling zone, the cooling medium distributor is arranged in a ring shape along the circumference of the catalytic cracking reactor, and the cooling step is implemented through the cooling medium distributor.

[0068] In one embodiment of the present invention, in the cooling zone, a heat extractor is provided in an annular shape along the circumference of the catalytic cracking reactor, and the cooling step is performed through the heat extractor.

[0069] As a cooling method using a cooling medium distributor, physical cooling by spraying cooling medium can be used, or the above-mentioned cooling medium can be used as a second raw material to undergo cracking reaction in the cooling zone to absorb heat, so as to quickly cool the post-reaction logistics.

[0070] In the present invention, a cooling step is implemented in a cooling zone at a specific location in the catalytic cracking reactor to rapidly cool the stream after the catalytic cracking reaction to a target temperature (e.g., 450-530°C, preferably 480-500°C) in a short period of time, thereby effectively suppressing the thermal cracking reaction in the reactant stream after the catalytic cracking reaction and improving the yield and selectivity of light olefins.

[0071] In the present invention, a cooling zone is provided at a position where the catalyst density drops to 80% to 20% of the catalyst density in the dense fluidized bed, preferably at a position where the catalyst density drops to 70% to 30% of the catalyst density in the dense fluidized bed, to cool the reactant stream after the reaction. Thus, cooling of the reactant stream after the reaction begins at a position where the catalyst density drops to 80% to 20% of the catalyst density in the dense fluidized bed, preferably at a position where the catalyst density drops to 70% to 30% of the catalyst density in the dense fluidized bed, allowing the stream to be cooled rapidly.

[0072] In one embodiment of the present invention, cooling zones are provided at positions where the catalyst density is reduced to 80%, 70%, 60%, 50%, 40%, 30%, or 20% of the catalyst density in the dense fluidized bed.

[0073] In one embodiment of the present invention, the reaction stream is cooled to 450-530°C, preferably 480-500°C, by the cooling zone of the catalytic cracking reactor. In the present invention, if the temperature of the reaction stream after the cooling step in the cooling zone exceeds 530°C, possible thermal cracking reactions in the reaction stream are not fully suppressed, resulting in a decrease in the yield and selectivity of light olefins. If the temperature of the reaction stream after the cooling step in the cooling zone is lower than 450°C, the energy consumption of the cooling zone will be excessively increased, and the energy consumption required for subsequent catalyst regeneration will also increase.

[0074] In one embodiment of the present invention, in the cooling step in the cooling zone, the reacted logistics is cooled to the target temperature (450-530°C, preferably 480-500°C) within 0.5-2 seconds, preferably within 0.5-1 second.

[0075] In other words, the cooling step of the present invention must be performed rapidly. If the cooling time is too long, the cooling rate is insufficient, and possible thermal cracking reactions in the reactant stream are not fully suppressed, resulting in a decrease in the yield and selectivity of light olefins. On the other hand, if the cooling time is too short, an excessive amount of cooling medium or high-power heat extraction is required, resulting in unnecessary waste.

[0076] In one embodiment of the present invention, the conditions for the catalytic cracking reaction include: 3 In one embodiment of the present invention, the density of the dense phase fluidized bed is 300-600 kg / m 3 , more preferably 400-500kg / m 3 If the density of the catalyst is too low, the contact between the reaction raw materials and the catalyst is insufficient, and the reaction raw materials are prone to thermal cracking reaction.

[0077] In one embodiment of the present invention, the catalyst comprises catalytically active components, which, on a dry basis and based on the total weight of the catalytically active components, include 1-50 wt% of a medium-pore zeolite, 5-99 wt% of an inorganic oxide, and 0-70 wt% of a clay.

[0078] In one embodiment of the present invention, the medium-pore zeolite is at least one selected from the group consisting of ZSM-5 series zeolites, ZRP zeolites and SAPO series zeolites.

[0079] In one embodiment of the present invention, the medium-pore zeolite is preferably a medium-pore ZSM-5 series zeolite, more preferably at least one selected from ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, SAPO-34, SAPO-11 and SAPO-47.

[0080] In one embodiment of the present invention, the silicon to aluminum ratio of the zeolite is 10-1000.

[0081] In one embodiment of the present invention, the inorganic oxide is one or more selected from silicon dioxide and aluminum oxide.

[0082] In one embodiment of the present invention, the clay is one or more selected from kaolin, halloysite, montmorillonite, diatomaceous earth, saponite, rectorite, sepiolite, attapulgite, hydrotalcite and bentonite.

[0083] In one embodiment of the present invention, the catalyst is a mixed catalyst comprising a catalyst active component and an auxiliary component, and the mass ratio of the catalyst active component to the auxiliary component is 1:(0.1-3), preferably 1:(0.5-2).

[0084] In one embodiment of the present invention, the auxiliary component is at least one selected from silicon dioxide, titanium dioxide, aluminum oxide, silicon carbide, aluminum nitride, boron nitride, manganese oxide, boron oxide, and silicon nitride, preferably at least one of manganese oxide, boron nitride, and boron oxide.

[0085] When the catalyst is a mixed catalyst comprising a catalytically active component and an auxiliary component, the auxiliary component can be mixed with the catalytically active component and then introduced into the reactor as a catalyst; alternatively, the auxiliary component and the catalytically active component can be independently introduced into the reactor, mixed in the reactor, and then used as a catalyst.

[0086] In the present invention, the temperature drop of the catalytic cracking reaction of the present invention can be controlled to be within the range of the present invention by using an auxiliary component together with the catalyst active component. In this case, the catalyst active component and the auxiliary component are mixed and used as a catalyst.

[0087] In one embodiment of the present invention, the catalyst active component and the auxiliary component are mixed, heated to 600-800° C., and then fed into the reactor as a hot catalyst.

[0088] In one embodiment of the present invention, the catalyst active component and the auxiliary component are heated to 600-800° C. respectively, fed into a reactor, and mixed to form a catalyst.

[0089] In one embodiment of the present invention, the additive component is incorporated into the catalyst during its preparation. This allows the catalyst, containing the additive component, to control the temperature drop during the catalytic cracking reaction. In this case, the catalyst is heated to 600-800°C and then fed into the reactor as a hot catalyst.

[0090] That is, in one embodiment of the present invention, the catalyst comprises 1 to 50 wt% of medium pore zeolite, 5 to 89 wt% of auxiliary component and 10 to 70 wt% of carrier on a dry basis and based on the total weight of the catalyst.

[0091] In one embodiment of the present invention, the medium-pore zeolite is at least one selected from the group consisting of ZSM-5 series zeolites, ZRP zeolites, and SAPO series zeolites.

[0092] In one embodiment of the present invention, the medium pore zeolite is preferably a medium pore ZSM-5 series zeolite, more preferably at least one selected from ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, SAPO-34, SAPO-11 and SAPO-47.

[0093] In one embodiment of the present invention, the silicon to aluminum ratio of the zeolite is 10-1000.

[0094] In one embodiment of the present invention, the carrier comprises clay and an inorganic oxide; the clay is at least one selected from kaolin, halloysite, montmorillonite, diatomaceous earth, saponite, rectorite, sepiolite, attapulgite, hydrotalcite and bentonite; and the inorganic oxide is at least one selected from silicon dioxide and aluminum oxide.

[0095] In one embodiment of the present invention, the catalyst preparation method comprises the following steps: uniformly mixing a carrier, a medium-porous zeolite, and an auxiliary component in a proportioned manner, spray drying, and calcining. For example, in one specific embodiment of the present invention, a certain amount of kaolin, pseudo-boehmite, and hydrochloric acid can be uniformly mixed and aged, and then a certain amount of auxiliary component and zeolite can be added. The slurry can be uniformly stirred and then spray dried to obtain the catalyst of the present invention.

[0096] In one embodiment of the present invention, the auxiliary component is microspherical solid particles; the particle size of the auxiliary component is not higher than 500 μm, preferably not higher than 400 μm.

[0097] In a more preferred embodiment of the present invention, when the catalyst is a mixed catalyst comprising a catalytically active component and an auxiliary component, the auxiliary component can be prepared into particles smaller or larger than the particle size of the catalytically active component for easy separation, and the amount of the auxiliary component can be increased or decreased to adapt to different raw materials.

[0098] In one embodiment of the present invention, in the mixed catalyst, at least a part of the components of the auxiliary component is the same as at least a part of the inorganic oxide of the catalyst active component; or in the catalyst containing the auxiliary component, at least a part of the components of the auxiliary component is the same as at least a part of the carrier, thereby facilitating heat transfer.

[0099] In a preferred embodiment of the present invention, based on the total weight of the auxiliary component, the auxiliary component includes 35-55 weight % of silicon dioxide, 3-10 weight % of titanium dioxide, 10-35 weight % of aluminum oxide, 10-40% of manganese oxide, and 5-20% of boron oxide.

[0100] In a preferred embodiment of the present invention, based on the total weight of the auxiliary component, the auxiliary component comprises 35-55 wt% of silicon dioxide, 5-15 wt% of titanium dioxide, 25-35 wt% of aluminum oxide, and 5-25 wt% of boron nitride.

[0101] In one embodiment of the present invention, heat is added to the catalyst bed (in the present invention, this step is also referred to as a heat-addition step) to control the reaction temperature to fall within the specific range of the present invention.

[0102] By supplementing heat to the catalyst bed, the temperature drop of the hydrocarbon feedstock after contact with the catalyst can be controlled within the specific range of the present invention, thereby significantly inhibiting the polymerization reaction of olefin molecules caused by the cooling of the reaction materials during the reaction, reducing the formation of large molecular olefin products, and at the same time improving the selectivity and yield of light olefins in the product, especially ethylene products, thereby obtaining high-quality and highly selective target products.

[0103] In the supplementary heating step of the present invention, there is no limitation on the means of supplementary heating, and various supplementary heating means known in the art may be used, such as supplementary heating using a heat exchanger, supplementary heating using an electric heater, etc.

[0104] In one embodiment of the present invention, in the heating supplement step, heating is performed by an instant heat supplement system.

[0105] In one embodiment of the present invention, the instant heat replenishment system comprises a catalyst replenishment pipe for introducing additional hot catalyst and / or hot regenerated catalyst into the catalyst bed.

[0106] In one embodiment of the present invention, the instant heat supplement system includes a heat supplier disposed in the catalyst bed of the reactor.

[0107] In one embodiment of the present invention, the heat exchange in the heater is at least one of high-temperature steam and steam cracking gas.

[0108] In one embodiment of the present invention, the hydrocarbon feedstock is gasified by heat exchange and fed in a vapor phase, and the feed temperature of the feedstock is 100-400° C., preferably 150-300° C. Preheating the hydrocarbon feedstock to a suitable reaction temperature and feeding it in a vapor phase can promote unimolecular cracking of the light feedstock.

[0109] In one embodiment of the present invention, the hydrocarbon feedstock is C4-C8 olefins or a mixture containing C4-C8 olefins; the content of C4-C8 olefins in the mixture containing C4-C8 olefins is 50-100 wt%, preferably 80-100 wt%.

[0110] In one embodiment of the present invention, the hydrocarbon feedstock is at least one selected from the group consisting of a C4 or higher fraction produced by an alkane dehydrogenation unit, a C4 or higher fraction produced by a catalytic cracking unit in a refinery, a C4 or higher fraction produced by a steam cracking unit in an ethylene plant, a C4 or higher olefin-rich fraction produced as a by-product of an MTO (methanol to light olefins process), and a C4 or higher olefin-rich fraction produced as a by-product of an MTP (methanol to propylene process).

[0111] In one embodiment of the present invention, when the hydrocarbon feedstock of the present invention is produced by alkane dehydrogenation, the alkane feedstock used is not particularly limited. For example, it can be at least one of naphtha, aromatic raffinate, and other light hydrocarbons. In addition, alkane products produced by other petrochemical plants can also be used as the feedstock.

[0112] In the present invention, the method for separating the light olefins from the reactant stream is not particularly limited and can be performed using methods known in the art. For example, the light olefins (at least one of ethylene, propylene, and butene) of the present invention can be obtained by performing conventional separation operations such as gas-solid separation on the reactant stream and fractionating the resulting reaction oil gas containing the light olefins.

[0113] More specifically, in one embodiment of the present invention, the method further includes the following steps: performing gas-solid separation on the reaction flow containing reaction oil and gas containing light olefins and the catalyst to be regenerated after cooling to obtain reaction oil and gas containing light olefins and the catalyst to be regenerated, then performing a charring regeneration treatment on the regenerated catalyst, and returning it to the catalytic cracking reactor as a regenerated catalyst, and performing separation means such as distillation and fractionation on the first reaction oil and gas containing light olefins to obtain the light olefins and olefin-rich hydrocarbon stream of the present invention.

[0114] In addition, in one embodiment of the present invention, the separated olefin-rich hydrocarbon stream is refluxed as a hydrocarbon feedstock.

[0115] In one embodiment of the present invention, the reactor is selected from one or a series combination of a riser, a fluidized bed with a constant linear velocity, a fluidized bed with a constant diameter, an upward conveying line and a downward conveying line; the riser is a constant diameter riser reactor or a variable diameter fluidized bed reactor.

[0116] In one embodiment of the present invention, the catalyst after the reaction is charred and regenerated to obtain a regenerated catalyst; the regenerated catalyst is returned to the reactor after fuel combustion to supplement heat.

[0117] In one embodiment of the present invention, the catalyst is subjected to char regeneration in an oxygen-containing atmosphere at a temperature of 650-800° C.; and the oxygen content in the oxygen-containing atmosphere is not higher than 28% by volume.

[0118] FIG1 is a schematic flow diagram of a catalytic cracking method of the present invention. As shown in FIG1 , a pre-lifting medium is introduced into the reactor 2 via pipeline 1. The pre-reaction catalytic cracking catalyst from the regeneration inclined tube 19 moves upward under the action of the pre-lifting medium. The preheated gasified raw material from pipeline 3 and the atomized steam from pipeline 4 are injected into the bottom of the reactor 2 together, contacting the pre-reaction catalytic cracking catalyst to cause a catalytic cracking reaction and moving upward along the reactor 2. The reacted oil and gas products and the reacted catalytic cracking catalyst enter the cyclone separator of the settler 8 through the outlet section 7 of the reactor 2 to separate the reacted catalytic cracking catalyst and the oil and gas products. The oil and gas products enter the gas collecting chamber 9, and the reaction oil and gas in the gas collecting chamber 9 enter the subsequent product fractionation device 21 through the large oil and gas pipeline 20.

[0119] It should be noted that the oil and gas products after the reaction and the catalytic cracking catalyst after the reaction are rapidly cooled to below 530° C. in the cooling zone before leaving the reactor 2 .

[0120] The catalytic cracking catalyst after the reaction returns to the settler 8 from the feed leg and enters the stripping section 10. The stripping medium introduced in the stripping section 10 through the pipeline 11 strips out the adsorbed reaction oil and gas. Then, the catalyst enters the regenerator 13 through the regeneration inclined pipe 12 to be regenerated and contacts with the oxygen-containing gas from the pipeline 14 to burn off the coke carried by the catalyst. The burnt regenerated catalyst and the flue gas enter the cyclone separator 15 for separation. The separated flue gas enters the flue gas energy recovery system 17 through the pipeline 16 to recover energy. The regenerated catalyst returns to the bottom of the regenerator 13 and is supplemented with heat by the heat extractor 18, and then returns to the reactor 2 through the regeneration inclined pipe 19.

[0121] In another embodiment of the present invention, the reactor is a variable diameter fluidized bed reactor, for example, the reactor 2 includes a first reaction zone I and a second reaction zone II, and the hot regenerated catalyst can be introduced into the reactor through the side of the first reaction zone or the second reaction zone. For example, the hot regenerated catalyst from pipeline 5 enters the second reaction zone under the action of the medium from pipeline 6 and mixes with the catalyst to supplement heat for the reaction system (catalyst bed).

[0122] The present invention may optionally include the following embodiments.

[0123] Optionally, in the present invention, a high-temperature thermal catalyst with a temperature greater than 650°C is introduced into the reactor, contacted with an olefin-rich hydrocarbon feedstock and undergoes a cracking reaction. The temperature during the contact reaction between the feedstock and the catalyst is between 600 and 800°C. The difference between the catalyst temperature at the completion of the reaction and the temperature when the feedstock and the catalyst are in contact is 20-100°C. Gas-solid separation is then performed to obtain a catalytic cracking catalyst and oil and gas products after the reaction.

[0124] Optionally, the temperature of the catalyst before the reaction is above 680°C, and the specific heat capacity is higher than 1.5 J / (g·K); the difference between the temperature of the catalyst after the reaction and the temperature of the catalyst before the reaction is 30-90°C.

[0125] Optionally, the conditions for the catalytic cracking reaction include: the temperature at which the raw material contacts the catalyst is preferably 620-720°C;

[0126] The reaction pressure is 0.05-1 MPa, preferably 0.1-0.8 MPa;

[0127] The reaction time is 0.1 to 80 seconds, preferably 0.5 to 70 seconds;

[0128] The mass ratio of the catalyst to the raw material is (3-180):1, preferably (10-150):1.

[0129] Optionally, the reaction flow in the reactor is quickly cooled to below 530° C. before gas-solid separation is performed on the reaction flow after the reaction.

[0130] Alternatively, the catalyst may be prepared by uniformly mixing a medium-porous zeolite, an auxiliary component and a carrier in a certain proportion and molding the mixture together.

[0131] Optionally, on a dry basis and based on the total weight of the catalyst, the catalyst comprises 1 to 50 weight percent of a medium-pore zeolite, 5 to 89 weight percent of an auxiliary component, and 10 to 70 weight percent of a carrier; the medium-pore zeolite is selected from at least one of a ZSM-5 series zeolite and a ZRP zeolite; the carrier comprises clay and an inorganic oxide; the clay is selected from at least one of kaolin, halloysite, montmorillonite, diatomaceous earth, saponite, rectorite, sepiolite, attapulgite, hydrotalcite, and bentonite; and the inorganic oxide is selected from at least one of silicon dioxide and aluminum oxide.

[0132] Optionally, the preparation method of the catalyst comprises the following steps: uniformly mixing the carrier, the medium-pore zeolite and the auxiliary component, spray drying, and calcining.

[0133] Alternatively, the catalyst is a mixed catalyst comprising a catalytically active component and an auxiliary component. The mixed catalyst may be prepared by first preparing the auxiliary component into solid particles, which are then physically and uniformly mixed with the catalytically active component to obtain the mixed catalyst. In this case, the mass ratio of the catalytically active component to the auxiliary component is 1:(0.1-3), preferably 1:(0.5-2).

[0134] Optionally, the auxiliary component is a microspherical solid particle; the particle size of the solid particle is not higher than 500 μm, preferably not higher than 400 μm; in the mixed catalyst, at least a part of the components of the auxiliary component is the same as at least a part of the inorganic oxide of the catalytic active component; or in the catalyst containing the auxiliary component, at least a part of the components of the auxiliary component is the same as at least a part of the carrier.

[0135] Optionally, based on the total weight of the catalyst active components, the catalyst active components include 1-50 weight % of medium-pore zeolite, 5-99 weight % of inorganic oxide and 0-70 weight % of clay; the medium-pore zeolite is at least one selected from ZSM-5 series zeolites and ZRP zeolites; the inorganic oxide is one or more selected from silica and alumina; the clay is one or more selected from kaolin, halloysite, montmorillonite, diatomaceous earth, saponite, rectorite, sepiolite, attapulgite, hydrotalcite and bentonite; the auxiliary agent components include but are not limited to silica, titanium dioxide, aluminum oxide, silicon carbide, aluminum nitride, boron nitride, manganese oxide, boron oxide, silicon nitride, and at least contain one of manganese oxide, boron nitride or boron oxide.

[0136] Optionally, the olefin-rich raw material is fed in gaseous phase after heat exchange gasification, and the feed temperature of the raw material is 100-400°C, preferably 150-300°C; the raw material is C4-C8 olefin or a mixture containing C4-C8 olefin; the content of C4-C8 olefin in the mixture containing C4-C8 olefin is 50-100wt%, preferably 80-100wt%.

[0137] Optionally, the reactor is selected from one or two series combinations of a riser, a fluidized bed with constant linear velocity, a fluidized bed with constant diameter, an upward conveying line and a downward conveying line, and the riser is a constant diameter riser reactor or a variable diameter fluidized bed reactor; preferably, the reactor is a variable diameter fluidized bed reactor and the reactor includes a first reaction zone and a second reaction zone; wherein, when the auxiliary component is first made into solid particles and then mixed with the catalyst active component, the auxiliary component before the reaction is mixed with the catalyst active component before the reaction and then introduced into the reactor as a catalyst, or the auxiliary component before the reaction is introduced into the reactor through the side of the first reaction zone and / or the second reaction zone, mixed with the catalyst active component, and used as a catalyst.

[0138] Optionally, the method further comprises the steps of:

[0139] The catalyst after the reaction is charred and regenerated to obtain a regenerated catalyst; the regenerated catalyst is returned to the reactor after fuel combustion to supplement heat; the charred regeneration of the catalyst is carried out in an oxygen-containing atmosphere at a temperature of 650 to 800° C.; the oxygen content in the oxygen-containing atmosphere is not higher than 28% by volume.

[0140] Example

[0141] The present invention is further described in detail below by way of examples, but is not limited thereto. The raw materials used in the examples and comparative examples can all be obtained through commercial sources. The raw materials used in the examples and comparative examples are 1-pentene or 1-hexene.

[0142] ZRP-1 zeolite is produced by the catalyst plant of Qilu Petrochemical Company, wherein SiO2 / Al2O3=30 and rare earth content RE2O3=2.0 wt%.

[0143] Halloysite kaolin is an industrial product produced by Suzhou Porcelain Clay Company, with a solid content of 71.6% by weight.

[0144] Pseudoboehmite is an industrial product of Shandong Aluminum Plant, with a solid content of 63% by weight.

[0145] The aluminum sol was produced by the catalyst plant of Qilu Petrochemical Company and had an Al2O3 content of 21.7% by weight.

[0146] Example 1

[0147] In this embodiment, catalytic cracking catalyst D1 is prepared, and its preparation method includes the following steps:

[0148] (1) Preparation of medium-pore zeolite with MFI structure

[0149] S1. Weigh 20 g of NH4Cl and dissolve it in 1000 g of water. Then, add 100 g (dry basis) of the crystallized ZRP-1 zeolite to the NH4Cl solution, exchange at 90°C for 0.5 hour, and filter to obtain a filter cake.

[0150] S2. Weigh 4.0 g of H3PO4 (85 wt %) and 4.5 g of Fe(NO3)3 and dissolve them in 90 g of water to obtain a mixed solution containing phosphorus and iron;

[0151] S3. The filter cake is impregnated with the phosphorus- and iron-containing mixed solution, dried, and then calcined at 550°C for 2 hours to obtain an MFI medium-porous zeolite containing phosphorus and iron. The elemental analysis chemical composition of the obtained zeolite is: 0.1 Na2O·5.1 Al2O3·2.4 P2O5·1.5 Fe2O3·3.8 RE2O3·88.1 SiO2.

[0152] (2) 75.4 kg of halloysite was weighed and slurried with 250 kg of decationized water, 54.8 kg of pseudo-boehmite was added, and the mixture was stirred evenly. The pH was adjusted to 2-4 with hydrochloric acid, and the mixture was allowed to stand at 60-70°C for 1 hour while maintaining the pH at 2-4. The temperature of the slurry was then lowered to below 60°C, 41.5 kg of aluminum sol was added to the slurry, and the mixture was stirred for 40 minutes to obtain a mixed slurry.

[0153] (3) The phosphorus- and iron-containing MFI medium-pore zeolite (24.5 kg on a dry basis) prepared in step (1) was added to the mixed slurry obtained in step (2), stirred evenly, spray-dried and formed, and washed with ammonium dihydrogen phosphate solution (phosphorus content of 1 wt%) to remove free Na + , and dried to obtain catalytic conversion catalyst D1.

[0154] Based on the total dry weight of catalyst D1, the dry composition of the catalyst includes: 20 wt% of MFI medium-pore zeolite containing phosphorus and iron, 28 wt% of pseudo-boehmite and 8 wt% of aluminum sol, and the balance is kaolin.

[0155] Example 2

[0156] The method for preparing the mixed catalytic cracking catalyst C1 in this example is carried out with reference to Example 1, and the difference between this method and Example 1 is that:

[0157] In step (3), the phosphorus and iron-containing MFI medium-pore zeolite (24.5 kg on a dry basis) prepared in step (1) and a certain amount of auxiliary components are added to the mixed slurry obtained in step (2), stirred evenly, spray-dried to form, and washed with ammonium dihydrogen phosphate solution (phosphorus content of 1 wt%) to remove free Na + and dried to obtain a mixed catalytic conversion catalyst C1. The chemical composition of the auxiliary component is: 30% by mass of manganese oxide, 15% by mass of aluminum oxide, 5% by mass of titanium dioxide, 10% by mass of boron oxide, and 40% by mass of silicon dioxide.

[0158] Based on the total dry weight of catalyst C1, the dry basis composition of the catalyst includes: 17 wt% of phosphorus- and iron-containing MFI medium-pore zeolite, 15 wt% of pseudo-boehmite, 8 wt% of aluminum sol and 16 wt% of an auxiliary component, with the balance being kaolin.

[0159] The catalytic cracking test of this embodiment was carried out on a medium-sized riser reactor of the process shown in Figure 1. 1-Hexene and a high-temperature mixed catalytic cracking catalyst C1 were heated in the riser reactor at a catalyst density of about 550 kg / m 3 The catalytic cracking reaction is carried out under the conditions of contact. The flow after the reaction is reduced to about 180kg / m 3During the reaction, the cooling medium in the heat exchanger cools to 520°C in 1.0 second and then enters a cyclone separator for gas-solid separation. The resulting reaction oil and gas are then introduced into the subsequent product fractionation unit. The post-reaction catalyst is then introduced into a regenerator for char regeneration and then returned to the riser reactor to continue the reaction. Six temperature measurement points were evenly spaced from the initial contact reaction between the catalyst and feedstock to the reactor cooling zone. The temperature drops at adjacent measurement points along the direction of material flow were ΔT1, ΔT2, ΔT3, ΔT4, and ΔT5, respectively. The reaction conditions and product distribution are shown in Table 1.

[0160] Example 3

[0161] The method for preparing the mixed catalytic cracking catalyst C2 in this example is carried out with reference to Example 1, and the difference between this method and Example 1 is that:

[0162] In step (3), the phosphorus and iron-containing MFI medium-pore zeolite (24.5 kg on a dry basis) prepared in step (1) and a certain amount of auxiliary components are added to the mixed slurry obtained in step (2), stirred evenly, spray-dried to form, and washed with ammonium dihydrogen phosphate solution (phosphorus content of 1 wt%) to remove free Na + The mixed catalytic conversion catalyst C2 is obtained by drying. The chemical composition of the auxiliary component is: 30% by mass of manganese oxide, 15% by mass of aluminum oxide, 5% by mass of titanium dioxide, 10% by mass of boron oxide and 40% by mass of silicon dioxide.

[0163] Based on the total dry weight of catalyst C2, the dry basis composition of the catalyst includes: 14 wt% of phosphorus and iron-containing MFI medium-pore zeolite, 10 wt% of pseudo-boehmite, 8 wt% of aluminum sol and 24 wt% of auxiliary component, and the balance is kaolin.

[0164] The experiment of this example was carried out according to the process shown in Figure 1. The difference between this example and Example 2 is that the catalyst used was mixed catalyst C2. The reaction conditions and product distribution are shown in Table 1.

[0165] Comparative Example 1

[0166] The experiment of Comparative Example 1 was carried out according to the process shown in Figure 1. The difference between it and Example 3 is that the catalyst used is catalyst D1 prepared in Example 1. The reaction conditions and product distribution are shown in Table 1.

[0167] The preparation methods and properties of the catalysts used in Examples 4 and 5 are as follows:

[0168] 969 g of halloysite was weighed and slurried in 4300 g of decationized water. 781 g of pseudo-boehmite and 144 mL of hydrochloric acid (30% by weight, specific gravity 1.56) were added to the resulting slurry and stirred evenly. The pH was maintained at 2-4. The slurry was aged at 60 ° C for 1 hour and then cooled to room temperature. Then, 5000 g of a slurry of a high silicon-aluminum ratio medium-pore shape-selective ZSM-5 zeolite containing chemical water was added to the aged slurry. The mixture was stirred evenly and spray-dried to wash away free Na + After steam aging, the steam aging process will wash away the free Na + The catalyst was aged in water vapor at 800°C for 15 h. The properties of the obtained catalyst A are shown in Table 2.

[0169] Example 4

[0170] In this example, the catalytic cracking reaction of a light feedstock was conducted in a medium-sized riser reactor unit according to the flow chart shown in Figure 1. 1-Pentene and a high-temperature mixed catalyst (the weight ratio of Catalyst A to the auxiliary component was 1:0.2) were contacted in the riser reactor to conduct the catalytic cracking reaction. The auxiliary component, based on the total weight of the auxiliary component, was composed of: 50% by mass silica, 10% by mass titanium dioxide, 30% by mass aluminum oxide, and 10% by mass boron nitride.

[0171] The catalyst density is about 550 kg / m 3 The catalytic cracking reaction is carried out under the conditions of contact. The flow after the reaction is reduced to about 180kg / m 3 The cooling medium in the heat exchanger is cooled to 520°C in 1.0 second, and the reaction products separated by the cyclone separator are sent to the subsequent product fractionation device. The mixed catalyst to be regenerated is introduced into the regenerator for char regeneration and then returns to the riser reactor to continue participating in the reaction.

[0172] The reaction conditions and product distribution are shown in Table 3.

[0173] Example 5

[0174] Example 5 was conducted according to the method of Example 4. The difference from Example 4 was that the weight ratio of the catalyst to the auxiliary component was different, wherein the weight ratio of Catalyst A to the auxiliary component was 1:0.5. The reaction conditions and product distribution are shown in Table 3.

[0175] Comparative Example 2

[0176] Comparative Example 2 was tested according to the method of Example 4, except that no auxiliary component was introduced into the reaction system. The reaction conditions and product distribution are shown in Table 3.

[0177] Table 1

[0178] Table 2

[0179] Table 3

[0180] As can be seen from Tables 1 and 3, when the method of the present invention is used to catalytically crack hydrocarbon feedstocks to prepare light olefins, since the extent of temperature reduction is controlled during the catalytic cracking reaction, the effect of the temperature drop on the feedstock cracking reaction process is weakened, the unimolecular cracking of the feedstock is enhanced, the yield of light olefins such as ethylene and propylene is increased, and the efficient utilization of the feedstock is promoted.

[0181] At the same time, the method provided by the present invention can also reduce the amount of catalytic cracking catalyst used while meeting the overall heat demand of the reaction system. On the one hand, it can reduce costs, and on the other hand, it can avoid the increase in coke and dry gas yields caused by high catalyst-to-oil ratio conditions, thereby improving the utilization rate of petrochemical resources.

[0182] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0183] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0184] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A catalytic cracking method for preparing light olefins, characterized in that: The method comprises the following steps: In the catalytic cracking reactor, the hydrocarbon feedstock is brought into contact with the catalyst at a temperature of 600-800°C to cause a catalytic cracking reaction, thereby obtaining a reaction stream containing reaction oil gas containing light olefins and a catalyst to be produced. The reaction flow after the reaction is cooled to 450-530°C in a cooling zone, and the cooled reaction flow is separated to obtain light olefins, wherein the length from the position where the hydrocarbon feedstock starts to contact the catalyst to the starting position of the cooling zone is evenly divided into n sections (n ​​is 5 or more, preferably 8 or more, more preferably 10 or more, further preferably 15 or more, and particularly preferably 20 or more), and according to the direction of the reaction flow, when the reaction flow passes through the xth section (2≤x≤n) among the n sections, the temperature drop ΔTx of the reaction flow in the xth section satisfies ΔTx≤ΔTx-1, and the temperature drop of the reaction flow in the first section ΔT1≤150 / n, preferably ΔT1≤100 / n, further preferably ΔT1≤80 / n, and more preferably ΔT1≤50 / n.

2. The catalytic cracking method according to claim 1, wherein: According to the direction of the reactant flow, the total temperature drop ΔT1+ΔT2≤280℃ / n when the reactant flow passes through the first and second sections of the n sections. Preferably, the total temperature drop ΔT1+ΔT2≤180℃ / n, further preferably, the total temperature drop ΔT1+ΔT2≤150℃ / n, and more preferably, the total temperature drop ΔT1+ΔT2≤80℃ / n.

3. The catalytic cracking method according to claim 1 or 2, wherein: The difference between the temperature of the reactant stream when entering the cooling zone and the initial temperature of the reactant feed when contacting the catalyst is 20-100°C, preferably the temperature difference is 30-90°C.

4. The catalytic cracking method according to any one of claims 1 to 3, wherein: The conditions of the catalytic cracking reaction include: at a catalyst density of 100-700 kg / m 3 , preferably 300-600kg / m 3 , more preferably 400-500kg / m 3 A catalytic cracking reaction is carried out in a dense phase fluidized bed; and / or A cooling zone is provided at a position where the catalyst density is reduced to 80% to 20% of the catalyst density in the dense fluidized bed, preferably a cooling zone is provided at a position where the catalyst density is reduced to 70% to 30% of the catalyst density in the dense fluidized bed; and / or In the cooling zone, a cooling medium distributor is used for cooling; or a heat collector is used for cooling, and the cooling medium in the cooling medium distributor or the heat collector is at least one selected from liquefied gas, crude gasoline, stabilized gasoline, diesel, heavy diesel and water.

5. The catalytic cracking method according to any one of claims 1 to 4, wherein: The conditions of the catalytic cracking reaction include: the raw material and the catalyst are in contact at a temperature of 620-720°C; and / or The reaction pressure is 0.05 to 1 MPa, preferably 0.1 to 0.8 MPa; and / or The reaction time is 0.1 to 80 s, preferably 0.5 to 70 s; and / or The mass ratio of the catalyst to the raw material is (3-180):1, preferably (10-150):

1.

6. The catalytic cracking method according to any one of claims 1 to 5, wherein: The method comprises the following steps: in a cooling zone, cooling the reaction flow to 450-530° C., preferably to 480-500° C., within 0.5-2 seconds, preferably within 0.5-1 second.

7. The catalytic cracking method according to any one of claims 1 to 6, wherein: The catalyst comprises a catalyst active component, which, on a dry basis and based on the total weight of the catalyst active component, comprises 1-50 wt% of a medium-pore zeolite, 5-99 wt% of an inorganic oxide and 0-70 wt% of a clay; and / or The medium-pore zeolite is at least one selected from ZSM-5 series zeolites, ZRP zeolites and SAPO series zeolites; preferably medium-pore ZSM-5 series zeolites, more preferably at least one selected from ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, SAPO-34, SAPO-11 and SAPO-47; and / or The silicon to aluminum ratio of the zeolite is 10-1000; and / or The inorganic oxide is one or more selected from silicon dioxide and aluminum oxide; and / or The clay is one or more selected from kaolin, halloysite, montmorillonite, diatomaceous earth, saponite, rectorite, sepiolite, attapulgite, hydrotalcite and bentonite.

8. The catalytic cracking method according to any one of claims 1 to 7, wherein: The catalyst is a mixed catalyst comprising a catalyst active component and an auxiliary component, wherein the mass ratio of the catalyst active component to the auxiliary component is 1:(0.05-3), preferably 1:(0.1-2), and the auxiliary component is at least one selected from silicon dioxide, titanium dioxide, aluminum oxide, silicon carbide, aluminum nitride, boron nitride, manganese oxide, boron oxide, and silicon nitride, and preferably comprises at least one of manganese oxide, boron nitride, and boron oxide. Preferably, when the catalyst is a mixed catalyst comprising a catalyst active component and an auxiliary component, the auxiliary component is mixed with the catalyst active component and then introduced into the reactor as a catalyst; Alternatively, the auxiliary agent component and the catalyst active component are introduced into the reactor independently, mixed in the reactor, and then used as a catalyst.

9. The catalytic cracking method according to any one of claims 1 to 6, wherein: On a dry basis and based on the total weight of the catalyst, the catalyst comprises 1 to 50 weight percent of a medium-pore zeolite, 5 to 89 weight percent of an auxiliary component and 10 to 70 weight percent of a carrier, and / or The medium-pore zeolite is at least one selected from ZSM-5 series zeolites, ZRP zeolites and SAPO series zeolites; preferably medium-pore ZSM-5 series zeolites, more preferably at least one selected from ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, SAPO-34, SAPO-11 and SAPO-47; and / or The silicon to aluminum ratio of the zeolite is 10-1000; and / or The carrier comprises clay and inorganic oxide; the clay is at least one selected from kaolin, halloysite, montmorillonite, diatomaceous earth, saponite, rectorite, sepiolite, attapulgite, hydrotalcite and bentonite; the inorganic oxide is at least one selected from silicon dioxide and aluminum oxide; The auxiliary component is at least one selected from silicon dioxide, titanium dioxide, aluminum oxide, silicon carbide, aluminum nitride, boron nitride, manganese oxide, boron oxide, and silicon nitride, and preferably contains at least one of manganese oxide, boron nitride, and boron oxide.

10. The catalytic cracking method according to claim 8, wherein: The auxiliary agent component is a microspherical solid particle; the particle size of the auxiliary agent component is not higher than 500 μm, preferably not higher than 400 μm; and / or In the mixed catalyst, at least a portion of the auxiliary agent component is the same as at least a portion of the inorganic oxide of the catalyst active component; Alternatively, in the catalyst comprising an auxiliary component, at least a part of the auxiliary component is the same as at least a part of the carrier.

11. The catalytic cracking method according to any one of claims 1 to 10, wherein: During the reaction, heat is added to the catalyst; preferably, the heat is added using a heat exchange medium and / or a hot catalyst; the heat exchange medium is at least one of high-temperature steam and steam cracking gas.

12. The catalytic cracking method according to any one of claims 1 to 11, wherein: The hydrocarbon raw material is fed in gas phase after heat exchange gasification, and the feed temperature of the raw material is 100-400° C., preferably 150-300° C.; and / or The hydrocarbon feedstock is C4-C8 olefin or a mixture containing C4-C8 olefin; the content of C4-C8 olefin in the mixture containing C4-C8 olefin is 50-100wt%, preferably 80-100wt%; and / or The hydrocarbon feedstock is selected from at least one of the C4 and above fractions produced by an alkane dehydrogenation unit, the C4 and above fractions produced by a catalytic cracking unit in an oil refinery, the C4 and above fractions produced by a steam cracking unit in an ethylene plant, the C4 and above olefin-rich fractions produced as a by-product of MTO, and the C4 and above olefin-rich fractions produced as a by-product of MTP.

13. The catalytic cracking method according to any one of claims 1 to 12, wherein: The reactor is selected from a riser, a fluidized bed with a constant linear velocity, a fluidized bed with a constant diameter, an upward conveying line and a downward conveying line, or a series combination of two of them. Preferably, the riser is a riser reactor with a constant diameter or a fluidized bed reactor with a variable diameter.

14. The catalytic cracking method according to any one of claims 1 to 13, wherein: The method further comprises the following steps: The catalyst to be regenerated is charred to obtain a regenerated catalyst; preferably, the regenerated catalyst is returned to the reactor after fuel combustion to supplement heat; and / or The catalyst is regenerated by burning in an oxygen-containing atmosphere at a temperature of 650-800° C. The oxygen content in the oxygen-containing atmosphere is not higher than 28% by volume.

15. The catalytic cracking method according to any one of claims 1 to 14, wherein: The method further comprises the following steps: The cooled reaction stream is subjected to gas-solid separation to obtain reaction oil gas containing light olefins and a regenerated catalyst, and the regenerated catalyst is subjected to charring and regeneration treatment and then returned to the reactor as a regenerated catalyst; Fractionating the reaction oil gas containing light olefins to obtain light olefins and an olefin-rich hydrocarbon stream; The olefin-rich hydrocarbon stream is refluxed as a hydrocarbon feedstock.

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