Method and device for preparing low-carbon olefin

Abstract

The invention discloses a method and a device for preparing low-carbon olefin, which can realize high-selectivity conversion of olefin and methanol into low-carbon olefin, solve the problem of overhigh yield of methanol cracking methane, furthest obtain ethylene and propylene, improve the selectivity of methane and coke and realize efficient utilization of methanol and fossil resources.

Description

A method and apparatus for preparing low-carbon olefins Technical Field

[0001] This application belongs to the field of petroleum processing, specifically relating to a method and apparatus for preparing low-carbon olefins, and particularly to a method for catalytically converting methyl tert-butyl ether compounds into low-carbon olefins. Background Technology

[0002] With the rapid development of the national economy, environmental pollution has received increasing attention, and environmental regulations have become increasingly stringent, leading to a continued slowdown in the growth rate of refined oil demand. In the near future, demand for low-carbon olefins will remain strong, making the transformation of oil refining towards chemical production inevitable. Ethylene and propylene are two high-value basic organic chemical raw materials. Ethylene is an important basic organic chemical raw material, mainly used in the production of polyethylene, ethylene propylene rubber, polyvinyl chloride, ethanol, ethylene oxide, ethylene glycol, acetaldehyde, acetic acid, propionaldehyde, propionic acid and their derivatives, and other basic organic synthetic raw materials; it is widely used in the pharmaceutical and chemical industries. Propylene is an important basic chemical raw material for the production of propylene derivatives (such as polypropylene, acrylonitrile, and propylene oxide). Methyl tert-butyl ether has a high octane number and is widely used globally as a gasoline octane number blender. Similarly, catalytic light gasoline ether chemistry reacts reactive C5 and C6 olefins in catalytic cracking light gasoline with alcohols to produce alkyl tert-alkyl ethers, reducing the olefin content and vapor pressure of catalytic gasoline, while simultaneously converting low-value methanol into high-value gasoline products. This is a clean gasoline production process with considerable economic benefits.

[0003] CN102451674B discloses a catalyst for the cracking of methyl tert-butyl ether to isobutylene, its preparation method, and its application, with the aim of producing high-purity isobutylene. This method utilizes a catalyst prepared for the cracking of methyl tert-butyl ether to isobutylene, enabling the reaction to be completed under relatively high pressure, achieving high conversion and selectivity, and extending the equipment's operating cycle.

[0004] CN109225349A discloses a method for preparing a catalyst for the cracking of methyl tert-butyl ether to isobutylene. The catalyst prepared by this method can reduce the temperature required for the cracking reaction of methyl tert-butyl ether, has high selectivity for isobutylene and methanol, and also has a high conversion rate. It does not require the addition of inert substances such as water to the reaction system, has low energy consumption, and high equipment utilization.

[0005] Most of the catalysts or processes disclosed in existing patents or literature for the cracking of methyl tert-butyl ether to produce olefins are used to produce high-purity olefins with four or more carbon atoms. For example, methyl tert-butyl ether cracking is used to prepare high-purity isobutylene. There are very few reports on the use of methyl tert-butyl ether to produce low-carbon olefins such as ethylene and propylene. Summary of the Invention

[0006] One objective of this application is to provide a method for maximizing the production of low-carbon olefins from methyl tert-butyl ether, which can convert methyl tert-butyl ether into low-carbon olefins, improve the yield and selectivity of ethylene and propylene, reduce the yield of methane, and minimize the methanol content in the product, thereby achieving low-cost methanol-to-low-carbon olefin conversion.

[0007] A first aspect of the present invention provides a method for preparing low-carbon olefins, comprising:

[0008] S1 allows methyl tert-butyl ether to be contacted with a catalytic conversion catalyst in a catalytic conversion reactor to undergo a catalytic conversion reaction, yielding the catalytic conversion reaction product;

[0009] S2 separates the catalytic conversion reaction products to obtain ethylene, propylene, a first-cycle olefin stream containing butene, and / or a C5-containing stream. + The second-cycle olefin stream;

[0010] S3 introduces at least a portion of the first cycle olefin stream and / or at least a portion of the second cycle olefin stream, along with optional externally sourced olefins, into the etherification unit, where they are contacted with methanol under etherification conditions to yield a cycle of methyl tert-butyl ether and post-etherified olefins.

[0011] S4 allows the recycled methyl tert-butyl ether and optional etherified olefins to be recycled back to the catalytic conversion reactor for catalytic conversion reactions;

[0012] At least a portion of the etherified olefins obtained in step S3 (S5) enter the isomerization unit, where they are contacted with an isomerization catalyst to undergo an isomerization reaction to obtain isomerized olefins. The isomerized olefins are then returned to the etherification unit for further reaction.

[0013] According to the method of the first aspect, in step S1, the catalytic conversion reaction conditions include:

[0014] The reaction temperature is 460-750℃, preferably 500-700℃, more preferably 520-700℃, and most preferably 550-680℃;

[0015] The reaction time is 0.01-15 seconds, preferably 0.05-10 seconds, more preferably 0.1-8.0 seconds, and most preferably 0.15-7.0 seconds; and / or

[0016] The weight ratio of the agent to oil is 1-50, preferably 5-40, and more preferably 6-30.

[0017] According to the method of the first aspect, in step S1, the catalytic conversion catalyst is selected from amorphous silica-alumina catalysts and / or zeolite catalysts, wherein the zeolite in the zeolite catalyst is selected from Y-type macroporous molecular sieves, β-type macroporous zeolite molecular sieves, ZSM-type mesoporous molecular sieves, and SAPO-type microporous molecular sieves.

[0018] According to the method of the first aspect, the zeolite in the catalytic conversion catalyst is selected from ZSM series molecular sieves, preferably from ZSM-5, ZSM-11 molecular sieves and hierarchical porous molecular sieves, wherein the silicon-aluminum molar ratio of the molecular sieve SiO2 / AlO3 is 50-1000, preferably 80-800, and most preferably 100-800.

[0019] Preferably, the ZSM-type molecular sieve in the catalytic conversion catalyst is a high-silica zeolite containing phosphorus and transition metals, and its anhydrous chemical expression, based on the mass of the oxide, is (0-0.3)Na₂O·(0.3-5)Al₂O₃·(1-10)P₂O₅·(0.7-20)M x O y ·(70-95)SiO2, where element M is selected from one or more of rare earth elements, alkali metals and alkaline earth metals, Fe, Co, Ni, Cu, Zn, Mo and Mn, x is the oxidation state of oxygen, and y is the oxidation state of element M.

[0020] According to the method of the first aspect, in step S3, the etherification reaction conditions include:

[0021] The reaction temperature is 20-120℃, preferably 30-80℃, more preferably 35-75℃; and / or

[0022] The reaction pressure is 0-5.0 MPa, preferably 0.2-2.0 MPa, and more preferably 0.5-1.5 MPa.

[0023] According to the method of the first aspect, the isomerization reaction conditions include:

[0024] The reaction temperature is 150-500℃, preferably 250-480℃, more preferably 300-450℃, and most preferably 350-450℃; and / or

[0025] Heavy hourly space velocity is approximately 1-30 h. -1 Preferably about 2-20 hours -1 More preferably, about 5-15 hours -1 .

[0026] According to the method of the first aspect, the isomerization catalyst comprises a support and a modified oxide, wherein:

[0027] The carrier comprises a zeolite molecular sieve and a binder. Preferably, the carrier comprises 50-99% by mass of molecular sieve and 1-50% by mass of binder. The molecular sieve is a molecular sieve with MFI, FER, TON and AEL structures, and the binder is alumina.

[0028] The modified oxide is a polyol, and the mass ratio of the modified oxide to the carrier is preferably 0.01 to 0.3:1. Preferably, the polyol is a C2 to C7 polyol, and more preferably one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, glycerol, trimethylolethane, pentaerythritol, xylitol and sorbitol.

[0029] According to the method of the first aspect, the catalytic conversion reaction product obtained in step S1 has the following characteristics:

[0030] The product contains no more than about 5.0% methane by mass, preferably no more than about 2.0%, and most preferably no more than 1.0%.

[0031] The mass ratio of ethylene to methane is not less than 4.0, preferably not less than about 8.0, and most preferably not less than 12.0;

[0032] The mass fraction ratio of propylene to propane in the product is not less than 10, preferably not less than 15, and most preferably not less than 30.

[0033] A second aspect of the present invention provides an apparatus for preparing low-carbon olefins, comprising:

[0034] A catalytic conversion reactor is used to bring methyl tert-butyl ether into contact with a catalytic conversion catalyst to carry out a catalytic conversion reaction, thereby obtaining the catalytic conversion reaction product;

[0035] A separation unit, connected to a catalytic conversion reactor, is used to separate the catalytic conversion products from the reactor, yielding ethylene and propylene, and a first recycled olefin stream containing butene and / or containing C5. + The second-cycle olefin stream;

[0036] An etherification unit, connected to a separation unit, allows at least a portion of the first and / or second recycled olefin streams, as well as optional externally sourced olefins, to enter the etherification unit and contact it with methanol under etherification conditions to obtain recycled methyl tert-butyl ether and post-etherified olefins.

[0037] An isomerization unit is connected to the etherification unit, such that at least a portion of the post-etherified olefin enters the isomerization unit and contacts the isomerization catalyst to obtain the isomerization product, which is then returned to the etherification unit for recycling.

[0038] The etherification unit is also connected to the catalytic conversion reactor for recycling recycled methyl tert-butyl ether and optional post-etherified olefins back to the catalytic conversion reactor for catalytic conversion reaction.

[0039] According to the apparatus of the second aspect, the catalytic conversion reactor is selected from any one and / or a combination of two or more reactor types, namely, fixed bed, moving bed and fluidized bed reactors;

[0040] Preferably, the fixed bed reactor consists of two or more reactors connected in series or parallel, and the fluidized bed reactor consists of one or more reactors connected in series or parallel, such as equal diameter riser, constant linear velocity riser, variable diameter riser, fluidized bed, composite reactor composed of equal diameter riser and fluidized bed, upward conveyor line, and downward conveyor line.

[0041] Specifically, the method of this application has at least one of the following technical effects compared with the prior art:

[0042] 1. Methyl tert-butyl ether is prepared from olefins and alcohols, and alcohols can be produced at low cost from coal, low-quality high-sulfur coal and coke oven gas, as well as biomass (such as wood, organic waste, etc.), thereby achieving low-cost production of low-carbon olefins.

[0043] 2. Biomass is the process by which plants fix carbon dioxide using solar energy and store it in the form of chemical energy. It can be used to produce alcohols, further obtain methyl tert-butyl ethers, and finally convert them into low-carbon olefins, thus realizing the recycling of carbon resources.

[0044] 3. It can achieve highly selective conversion of olefins and methanol into low-carbon olefins, while solving the problem of excessively high methane yield from methanol cracking, maximizing the production of ethylene and propylene, and improving the selectivity of methane and coke, thus achieving efficient utilization of methanol and fossil resources. Attached Figure Description

[0045] Figure 1 shows a schematic diagram of an apparatus for preparing low-carbon olefins according to the present invention.

[0046] Figure 2 shows a device diagram of a specific embodiment of the present invention.

[0047] Figure 3 shows a device diagram of a comparative example of the present invention.

[0048] Explanation of reference numerals in the attached figures:

[0049] 100. Catalytic conversion reactor; 200. Separation unit; 300. Etherification unit; 400. Isomerization unit; 101. Methyl tert-butyl ether; 102. Catalytic conversion reaction product; 103. Ethylene; 104. Propylene; 105. First circulating olefin stream; 106. Second circulating olefin stream; 107. Externally sourced olefins; 108. Methanol; 109. Circulating methyl tert-butyl ether; 110. Post-etherification olefins; 111. Non-olefin components; 112. Isomeric olefins; 113. Post-etherification olefin return line;

[0050] 1. Pre-lifting medium pipeline; 2. Variable diameter fluidized bed reactor; 3. Methyl tert-butyl ether stream; 4. Atomized steam; 5. Cooling agent stream; 6. Settler; 7. First reaction zone; 8. Second reaction zone; 9. Stripping section; 10. Stripping steam; 11. Regenerator inclined tube; 12. Regenerator; 13. Main air pipeline; 14. Flue gas pipeline; 15. Regeneration inclined tube; 16. Large oil and gas stream pipeline; 17. Fractionation, absorption-stabilization unit; 18. Dry gas stream pipeline; 19. 20. Liquefied petroleum gas (LPG) pipeline; 21. Gasoline pipeline; 22. Diesel fuel pipeline; 23. Heavy oil pipeline; 24. Gas separation unit; 25. Propylene pipeline; 26. Other olefins pipeline; 27. Etherification unit; 28. Post-etherification olefins pipeline; 29. ​​Alcohols pipeline (e.g., methanol); 30. Non-olefin components pipeline; 31. Isomerization unit; 32. Ethers pipeline; 33. Post-etherification olefins return pipeline; 44. Logistics pipeline. Detailed Implementation

[0051] 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.

[0052] 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.

[0053] 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.

[0054] This invention provides a method for preparing low-carbon olefins, comprising:

[0055] S1 allows methyl tert-butyl ether to be contacted with a catalytic conversion catalyst in a catalytic conversion reactor to undergo a catalytic conversion reaction, yielding the catalytic conversion reaction product;

[0056] S2 separates the catalytic conversion reaction products to obtain a first recycled olefin stream containing ethylene, propylene, butene, and / or C5... + The second-cycle olefin stream;

[0057] S3 introduces at least a portion of the first cycle olefin stream and / or at least a portion of the second cycle olefin stream, along with optional externally sourced olefins, into the etherification unit, where they are contacted with methanol under etherification conditions to yield a cycle of methyl tert-butyl ether and post-etherified olefins.

[0058] S4 allows the recycled methyl tert-butyl ether and optional etherified olefins to be recycled back to the catalytic conversion reactor for catalytic conversion reactions;

[0059] At least a portion of the etherified olefins obtained in step S3 (S5) enter the isomerization unit, where they are contacted with an isomerization catalyst to undergo an isomerization reaction to obtain isomerized olefins. The isomerized olefins are then returned to the etherification unit for further reaction.

[0060] The method of this application includes: introducing at least a portion of the post-etherified olefins into an isomerization unit for isomerization in the presence of an isomerization catalyst to obtain isomerized olefins. The inventors of this application have discovered that, compared to isomerized olefins, the conversion rate of normal-type olefins to ethers via condensation reactions with alcohols is lower, resulting in a higher proportion of normal-type olefins in the post-etherified olefins after etherification. Simultaneously, ethers generated from the condensation reaction of isomerized olefins with alcohols are more readily converted into low-carbon olefins such as ethylene and propylene in catalytic conversion reactions. Therefore, at least a portion of the post-etherified olefins can be introduced into an isomerization unit for isomerization in the presence of an isomerization catalyst to obtain isomerized olefins; and, as described above, these isomerized olefins are further converted into corresponding ether compounds as part of the olefin feedstock supplied to the etherification unit. The method of this invention, by producing low-carbon olefins such as ethylene and propylene from methyl tert-butyl ether, can maximize the production of low-carbon olefins.

[0061] In one embodiment, in step S1, the catalytic conversion reaction conditions include:

[0062] The reaction temperature is 460-750℃, preferably 500-700℃, more preferably 520-700℃, and most preferably 550-680℃;

[0063] The reaction time is 0.01-15 seconds, preferably 0.05-10 seconds, more preferably 0.1-8.0 seconds, and most preferably 0.15-7.0 seconds; and / or

[0064] The weight ratio of the agent to oil is 1-50, preferably 5-40, and more preferably 6-30.

[0065] In this application, reaction time refers to the residence time of the feedstock oil in the reactor. The catalyst-to-oil weight ratio refers to the weight ratio of the catalyst to the feedstock oil entering the reactor.

[0066] The inventors of this application have discovered that when the temperature is below 200°C, ethers are converted into alcohols and olefins, with a low selectivity for low-carbon olefins (the total amount of ethylene and propylene), below 10%, which is not conducive to maximizing the production of low-carbon olefins. However, when the reaction temperature is increased to above 460°C, especially above 550°C, the selectivity for low-carbon olefins (the total amount of ethylene and propylene) in the product increases significantly, particularly the ethylene selectivity, and the ethylene / methane mass ratio decreases significantly, thereby maximizing the production of high-value-added low-carbon olefins.

[0067] In one embodiment, in step S1, the catalytic cracking catalyst is selected from amorphous silica-alumina catalysts and / or zeolite catalysts. The zeolite in the zeolite catalyst is selected from Y-type macroporous molecular sieves, β-type macroporous zeolite molecular sieves, ZSM-type mesoporous molecular sieves, and SAPO-type microporous molecular sieves. The SAPO-type microporous molecular sieves include, but are not limited to, SAPO-34 and SAPO-18 molecular sieves.

[0068] In one embodiment, the zeolite in the catalytic conversion catalyst is selected from ZSM-type molecular sieves, preferably from ZSM-5, ZSM-11 molecular sieves and hierarchical porous molecular sieves, wherein the silicon-aluminum molar ratio SiO2 / AlO3 of the molecular sieve is 50-1000, preferably 80-800, and most preferably 100-800.

[0069] Preferably, the ZSM-type molecular sieve in the catalytic conversion catalyst is a high-silica zeolite containing phosphorus and transition metals, and its anhydrous chemical expression, based on the mass of the oxide, is (0-0.3)Na₂O·(0.3-5)Al₂O₃·(1-10)P₂O₅·(0.7-20)M x O y ·(70-95)SiO2, where element M is selected from one or more of rare earth elements, alkali metals and alkaline earth metals, Fe, Co, Ni, Cu, Zn, Mo and Mn, x is the oxidation state of oxygen, and y is the oxidation state of element M.

[0070] In one embodiment, in step S3, the etherification reaction conditions include:

[0071] The reaction temperature is 20-120℃, preferably 30-80℃, more preferably 35-75℃; and / or

[0072] The reaction pressure is 0-5.0 MPa, preferably 0.2-2.0 MPa, and more preferably 0.5-1.5 MPa.

[0073] In one embodiment, the isomerization reaction conditions include:

[0074] The reaction temperature is 150-500℃, preferably 250-480℃, more preferably 300-450℃, and most preferably 350-450℃; and / or

[0075] Heavy hourly space velocity is approximately 1-30 h. -1 Preferably about 2-20 hours -1 More preferably, about 5-15 hours -1 .

[0076] In one embodiment, the isomerization catalyst comprises a support and a modified oxide, wherein:

[0077] The carrier comprises a zeolite molecular sieve and a binder. Preferably, the carrier comprises 50-99% by mass of molecular sieve and 1-50% by mass of binder. The molecular sieve is a molecular sieve with MFI, FER, TON and AEL structures, and the binder is alumina.

[0078] The modified oxide is a polyol, and the mass ratio of the modified oxide to the carrier is preferably 0.01 to 0.3:1. Preferably, the polyol is a C2 to C7 polyol, and more preferably one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, glycerol, trimethylolethane, pentaerythritol, xylitol and sorbitol.

[0079] The inventors of this application have discovered that, under appropriate catalytic conversion conditions, ether feedstocks can be readily cracked into C2 and C3 olefins (i.e., ethylene and propylene), as well as C4 or C5 olefins. + The above-mentioned alkenes. As described later, these are C4 or C5. + The above-mentioned alkenes can be converted into corresponding ether compounds through etherification reactions. These ether compounds can then undergo repeated catalytic conversion reactions to convert C4 or C5 alkenes into C5 alkenes. + The above olefins are further converted into low-carbon olefins such as ethylene and propylene.

[0080] The catalytic conversion products obtained above can be divided into dry gas components (mainly including ethylene, methane, ethane, etc.), liquefied petroleum gas components (mainly including propylene, as well as propane, butane, butene, etc.) and gasoline components (mainly including C5) according to their distillation range. + (The above-mentioned olefins, etc.). In this application, the proportion of non-olefin products such as methane, ethane, and propane in the catalytic conversion reaction products is low.

[0081] In one embodiment, the catalytic conversion reaction product obtained in step S1 has the following characteristics:

[0082] The product contains no more than about 5.0% methane by mass, preferably no more than about 2.0%, and most preferably no more than 1.0%.

[0083] The mass ratio of ethylene to methane is not less than 4.0, preferably not less than about 8.0, and most preferably not less than 12.0;

[0084] The mass fraction ratio of propylene to propane in the product is not less than 10, preferably not less than 15, and most preferably not less than 30.

[0085] The present invention also provides an apparatus for preparing low-carbon olefins, comprising:

[0086] A catalytic conversion reactor is used to bring methyl tert-butyl ether into contact with a catalytic conversion catalyst to carry out a catalytic conversion reaction, thereby obtaining the catalytic conversion reaction product;

[0087] A separation unit, connected to a catalytic conversion reactor, is used to separate the catalytic conversion products from the reactor, yielding ethylene and propylene, and a first recycled olefin stream containing butene and / or containing C5. + The second-cycle olefin stream;

[0088] An etherification unit, connected to a separation unit, allows at least a portion of the first and / or second recycled olefin streams, as well as optional externally sourced olefins, to enter the etherification unit and contact it with methanol under etherification conditions to obtain recycled methyl tert-butyl ether and post-etherified olefins.

[0089] An isomerization unit is connected to the etherification unit, such that at least a portion of the post-etherified olefin enters the isomerization unit and contacts the isomerization catalyst to obtain the isomerization product, which is then returned to the etherification unit for recycling.

[0090] The etherification unit is also connected to the catalytic conversion reactor for recycling recycled methyl tert-butyl ether and optional post-etherified olefins back to the catalytic conversion reactor for catalytic conversion reaction.

[0091] In one embodiment, the catalytic conversion reactor is selected from any one and / or a combination of two or more reactor types, namely fixed bed, moving bed and fluidized bed reactors.

[0092] Preferably, the fixed bed reactor consists of two or more reactors connected in series or parallel, and the fluidized bed reactor consists of one or more reactors connected in series or parallel, such as equal diameter riser, constant linear velocity riser, variable diameter riser, fluidized bed, composite reactor composed of equal diameter riser and fluidized bed, upward conveyor line, and downward conveyor line.

[0093] In this invention, the catalytic conversion reactor is selected from any one and / or a combination of two or more reactor types, such as fixed bed, moving bed, and fluidized bed reactors; preferably, the fixed bed reactor is selected from two or more reactors connected in series or parallel; optionally, the fluidized bed reactor is selected from one or more reactors connected in series or parallel, such as constant diameter riser, constant linear velocity riser, variable diameter riser, fluidized bed and composite reactor composed of constant diameter riser and fluidized bed, upward conveying line, and downward conveying line.

[0094] In one specific embodiment, the catalytic conversion reactor can be a fluidized bed reactor of various forms, such as a single fluidized bed reactor or a composite reactor obtained by combining multiple fluidized bed reactors in series or parallel. In some preferred embodiments, the fluidized bed reactor can be a constant-diameter riser reactor or a fluidized bed reactor of various variable diameter forms, such as the reactor disclosed in Chinese Patent CN112569875A.

[0095] The separation unit of the present invention can be a common separation device in the art, such as a fractionation tower, which can separate the components into different components according to their distillation range. For example, catalytic cracking reaction products can be separated into dry gas components, liquefied petroleum gas components, gasoline components, diesel components, and slurry components in a fractionation tower, and then ethylene components can be separated from the dry gas components in another separation device, propylene components can be separated from the liquefied petroleum gas components in another separation device, and FGO components can be separated from the slurry components.

[0096] In the etherification unit of this invention, olefin feedstock and methanol can react in the presence of a catalyst to obtain the corresponding ether. This etherification reaction can be carried out using processes known in the art.

[0097] For example, in the presence of an acid catalyst, olefin feedstock can be contacted with methanol to undergo a condensation reaction, thereby generating the corresponding ether. Commonly used acid catalysts include sulfuric acid, phosphoric acid, and aluminum trichloride.

[0098] In the presence of an alkaline catalyst, olefin feedstocks can be contacted with methanol to undergo a condensation reaction, thereby generating the corresponding ethers. Commonly used alkaline catalysts include sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0099] Alternatively, in the presence of a metal catalyst, olefin feedstock can be contacted with methanol to undergo a condensation reaction, thereby generating the corresponding ether. Commonly used metal catalysts include copper, iron, and palladium. Figure 1 shows a schematic diagram of an apparatus for preparing low-carbon olefins according to the present invention, comprising:

[0100] Catalytic conversion reactor 100 is used to react methyl tert-butyl ether with a catalytic conversion catalyst in the catalytic conversion reactor to obtain catalytic conversion reaction products;

[0101] Separation unit 200, connected to catalytic conversion reactor 100, is used to separate the catalytic conversion reaction products from the reactor to obtain ethylene and propylene, as well as a first recycled olefin stream containing butene and / or containing C5. + The second-cycle olefin stream;

[0102] Etherification unit 300, which is connected to separation unit 200, such that the first and / or second olefin streams react with methanol in the etherification unit to obtain cyclic methyl tert-butyl ether and post-etherified olefins;

[0103] Isomerization unit 400 is connected to etherification unit 300, so that the etherified olefin enters the isomerization unit and reacts with the isomerization catalyst, and the resulting isomerization product is returned to etherification unit 300 for further reaction.

[0104] The etherification unit 300 is also connected to the catalytic conversion reactor 100, so that the recycled methyl tert-butyl ether from the etherification unit enters the catalytic conversion reactor for reaction.

[0105] Methyl tert-butyl ether 101 is fed into catalytic conversion reactor 100 and reacted with catalytic conversion catalyst to obtain catalytic conversion product 102. Catalytic conversion product 102 is then separated in separation unit 200 to obtain ethylene 103 (the target product), propylene 104, a first recycled olefin stream 105 (containing butene), and a C5+ stream. + The second cycle olefin stream 106 contains olefins; the first cycle olefin stream 105 contains butene and C5... + The second recycled olefin stream 106 and optional externally sourced olefins 107 enter the etherification unit 300 and react with methanol 108 to produce recycled methyl tert-butyl ether 109 and post-etherified olefins 110. Recycled methyl tert-butyl ether 109 is returned to the catalytic conversion reactor 100 for further reaction, and the post-etherified olefins 110 enter the isomerization unit 400 for isomerization. The resulting isomerized olefins 112 are returned to the etherification unit 300 for further reaction, and the non-olefin component 111 is sent downstream. A portion of the post-etherified olefins is returned to the catalytic conversion reactor 100 via the post-etherified olefins return line 113 for further reaction.

[0106] In one specific embodiment, the apparatus of the present invention may not include the etherification unit 300 and the isomerization unit 400, and the separation unit separates the target products ethylene and propylene, while other olefins are not further processed.

[0107] The following description, in conjunction with Figure 2, illustrates a specific implementation of the method of this application, but does not limit the scope of this application.

[0108] The pre-lifting medium enters from the bottom of the variable-diameter fluidized bed reactor 2 (e.g., the reactor disclosed in Chinese Patent CN112569875A) via pipeline 1. The methyl tert-butyl ether mixture, along with atomized steam from pipeline 4, is injected through pipeline 3 into the bottom of the first reaction zone 7 of the variable-diameter fluidized bed reactor 2 via nozzles. It contacts the regenerated catalyst from the regeneration inclined tube 15 within the reactor and moves upwards into the second reaction zone 8 of the variable-diameter fluidized bed reactor 2 to continue the reaction. The generated oil and gas, along with the deactivated catalyst, enters the cyclone separator in the settling tank 6 to separate the catalyst from the oil and gas. The reacted oil and gas enters the main oil and gas pipeline 16, while the catalyst fines are returned to the settling tank 6 via the cyclone separator feed leg. The catalyst in the settling tank 6 flows to the stripping section 9, where it contacts the stripping steam from pipeline 10. The oil and gas stripped from the catalyst enters the main oil and gas pipeline 16 after passing through the cyclone separator. After stripping, the spent catalyst enters the regenerator 12 through the spent catalyst inclined tube 11. The main air enters the regenerator through pipeline 13 to burn off the coke on the spent catalyst, thus regenerating the deactivated spent catalyst. The flue gas is then led out through pipeline 14. The regenerated catalyst enters the variable diameter fluidized bed reactor 2 through the regeneration inclined tube 15 for recycling.

[0109] The reaction oil and gas pass through the large oil and gas pipeline 16 and enter the fractionation, absorption-stabilization unit 17. The separated dry gas is led out through pipeline 18 and separated to obtain ethylene. The liquefied gas is led out through pipeline 19 and separated into propylene through gas separation unit 23 and sent out through pipeline 24. Other olefins are sent to the etherification unit 26 through pipeline 25 along with gasoline from pipeline 20. Some of the unreacted etherified olefins are sent to the isomerization unit 30 through pipeline 27 and methanol from pipeline 28. The non-olefin components that have not reacted after the etherification reaction are sent to the downstream unit through pipeline 29. The methyl tert-butyl ether obtained from etherification is returned to reactor 2 through pipelines 31 and 33 to react. Some of the unreacted etherified olefins are returned to reactor 2 through pipelines 32 and 33 to increase the production of low-carbon olefins.

[0110] In one specific embodiment, as shown in Figure 3, the etherification unit and isomerization unit may not be set up. The reaction oil and gas enter the fractionation, absorption-stabilization unit 17 through the large oil and gas pipeline 16. The dry gas obtained by separation is led out through pipeline 18 and separated to obtain the target product ethylene. The liquefied gas is led out through pipeline 19 and separated into the target product propylene through the gas separation unit 23 and sent out through pipeline 24.

[0111] Example

[0112] The present application will be further described below with reference to the embodiments, but this does not limit the present application. The properties of the feedstock oils used in the embodiments and comparative examples are shown in Table 1. The catalysts used in the embodiments and comparative examples are commercially available catalytic conversion catalysts with the brand name TCC-1, manufactured by Sinopec Catalyst Qilu Branch. The isomerization catalysts used in the embodiments are commercially available catalysts with the brand name FI-15, manufactured by Sinopec Petrochemical Research Institute. The catalysts used in the etherification units in the embodiments are consistent with the catalysts used in the embodiments, namely CN101245255B.

[0113] Table 1. Properties of raw materials in examples and comparative examples.

[0114] Raw material oil name: Methyl tert-butyl ether Molecular formula: C5H 12 O density (20℃), g / cm³ 3 0.7 molecular weight, 78 boiling point, 55 °C surface

[0115] Comparative Example 1

[0116] The experiment was conducted according to the process shown in Figure 3. The specific structure of the variable-diameter fluidized bed reactor is shown in Example 1 of CN112569875A. The feedstock was methyl tert-butyl ether, and TCC-1 was used as the catalyst. The experiment was conducted on a variable-diameter fluidized bed reactor catalytic cracking unit. The unit did not include an etherification unit, and other olefin components and gasoline components obtained from liquefied gas separation were not etherified or isomerized. The target products, ethylene and propylene, were obtained. The reaction conditions and product distribution are listed in Table 2.

[0117] Comparative Example 2

[0118] The experiment was conducted using the variable-diameter fluidized bed reactor (see Example 1 of CN112569875A) according to the flow chart shown in Figure 3. The feedstock was methyl tert-butyl ether, and TCC-1 was used as the catalyst. The experiment was carried out on a variable-diameter fluidized bed reactor catalytic cracking unit, which did not include an etherification unit. Other olefin components and gasoline components obtained from liquefied petroleum gas separation were not etherified or isomerized. The target products, ethylene and propylene, were obtained. The reaction conditions and product distribution are listed in Table 2. The difference from Example 1 is that the reaction temperature was 450°C.

[0119] Example 1

[0120] The experiment was conducted according to the flow chart shown in Figure 2. The specific structure of the variable-diameter fluidized bed reactor is as described in Example 1 of CN112569875A. The feedstock was methyl tert-butyl ether, and TCC-1 was used as the catalyst. The experiment was carried out on a variable-diameter fluidized bed reactor catalytic cracking unit. The target products, ethylene and propylene, were obtained. The reaction conditions and product distribution are listed in Table 2. The difference from Example 1 is that after the isobutylene product underwent etherification and isomerization, the ethers were returned to the variable-diameter fluidized bed reactor catalytic cracking unit.

[0121] Table 2. Reaction conditions and product distribution of the examples and comparative examples.

[0122]

[0123]

[0124] The results above show that the method of the present invention can achieve highly selective conversion of olefins and methanol into low-carbon olefins, while solving the problem of excessively high methane yield from methanol cracking, maximizing the production of ethylene and propylene, and improving the selectivity of methane and coke, thus achieving efficient utilization of methanol and fossil resources.

[0125] The preferred embodiments of this application have been described in detail above. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0126] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

[0127] 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 preparing low-carbon olefins, comprising: S1 involves contacting methyl tert-butyl ether with a catalytic conversion catalyst in a catalytic conversion reactor to undergo a catalytic conversion reaction, yielding the catalytic conversion reaction product; S2 separates the catalytic conversion reaction product to obtain ethylene, propylene, a first circulating olefin stream containing butene, and / or a C5-containing stream. + The second recycled olefin stream of olefins; S3 allows at least a portion of the first recycled olefin stream and / or at least a portion of the second recycled olefin stream, along with optional externally sourced olefins, to enter the etherification unit, where they are contacted with methanol under etherification conditions to yield recycled methyl tert-butyl ether and post-etherified olefins; S4 recycles the methyl tert-butyl ether and optional post-ether olefins back to the catalytic conversion reactor for catalytic conversion; S5 at least a portion of the post-ether olefins obtained in step S3 enters the isomerization unit, contacts the isomerization catalyst to undergo an isomerization reaction to obtain isomerized olefins, which are then returned to the etherification unit for further reaction.

2. The method according to claim 1, wherein, In step S1, the catalytic conversion reaction conditions include: a reaction temperature of 460-750℃, preferably 500-700℃, more preferably 520-700℃, and most preferably 550-680℃; a reaction time of 0.01-15 seconds, preferably 0.05-10 seconds, more preferably 0.1-8.0 seconds, and most preferably 0.15-7.0 seconds; and / or an agent-oil weight ratio of 1-50, preferably 5-40, and more preferably 6-30.

3. The method according to claim 1, wherein, In step S1, the catalytic conversion catalyst is selected from amorphous silica-alumina catalysts and / or zeolite catalysts, and the zeolite in the zeolite catalyst is selected from Y-type macroporous molecular sieves, β-type macroporous zeolite molecular sieves, ZSM-type mesoporous molecular sieves, and SAPO-type microporous molecular sieves.

4. The method according to claim 3, wherein, The zeolite in the catalytic conversion catalyst is selected from ZSM-type molecular sieves, preferably ZSM-5, ZSM-11 molecular sieves, and hierarchical porous molecular sieves. The silica-alumina molar ratio (SiO2 / AlO3) of the molecular sieve is 50-1000, preferably 80-800, and most preferably 100-800. Preferably, the ZSM-type molecular sieve in the catalytic conversion catalyst is a high-silica zeolite containing phosphorus and transition metals, and its anhydrous chemical expression, based on the mass of the oxides, is (0-0.3)Na2O·(0.3-5)Al2O3·(1-10)P2O5·(0.7-20)M x O y ·(70-95)SiO2, where element M is selected from one or more of rare earth elements, alkali metals and alkaline earth metals, Fe, Co, Ni, Cu, Zn, Mo and Mn, x is the oxidation state of oxygen, and y is the oxidation state of element M.

5. The method according to claim 1, wherein, In step S3, the etherification reaction conditions include: a reaction temperature of 20-120℃, preferably 30-80℃, more preferably 35-75℃; and / or a reaction pressure of 0-5.0MPa, preferably 0.2-2.0MPa, more preferably 0.5-1.5MPa.

6. The method according to claim 1, wherein, The isomerization reaction conditions include: a reaction temperature of 150-500℃, preferably 250-480℃, more preferably 300-450℃, and most preferably 350-450℃; and / or a heavy hourly space velocity of about 1-30 h⁻¹. -1 Preferably about 2-20 hours -1 More preferably, about 5-15 hours -1 .

7. The method according to claim 1, wherein, The isomerization catalyst comprises a support and a modified oxide, wherein: the support comprises a zeolite molecular sieve and a binder, preferably, the support comprises 50-99% by mass of molecular sieve and 1-50% by mass of binder; the molecular sieve is a molecular sieve having an MFI structure, FER structure, TON structure and AEL structure, and the binder is alumina; the modified oxide is a polyol, and the mass ratio of the modified oxide to the support is preferably 0.01-0.3:1, preferably, the polyol is a C2-C7 polyol, more preferably one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, glycerol, trimethylolethane, pentaerythritol, xylitol and sorbitol.

8. The method according to any one of claims 1 to 7, wherein, The catalytic conversion product obtained in step S1 has the following characteristics: the mass percentage of methane in the product is not greater than about 5.0%, preferably not greater than about 2.0%, and most preferably not greater than 1.0%; the mass ratio of ethylene to methane is not less than 4.0, preferably not less than about 8.0, and most preferably not less than 12.0; the mass fraction ratio of propylene to propane in the product is not less than 10, preferably not less than 15, and most preferably not less than 30.

9. An apparatus for preparing low-carbon olefins, comprising: A catalytic conversion reactor is used to bring methyl tert-butyl ether into contact with a catalytic conversion catalyst to carry out a catalytic conversion reaction, thereby obtaining the catalytic conversion reaction product; A separation unit, connected to a catalytic conversion reactor, is used to separate the catalytic conversion products from the reactor, yielding ethylene and propylene, and a first recycled olefin stream containing butene and / or containing C5. + The second-cycle olefin stream; An etherification unit, connected to a separation unit, allows at least a portion of the first and / or second recycled olefin streams, as well as optional externally sourced olefins, to enter the etherification unit and contact it with methanol under etherification conditions to obtain recycled methyl tert-butyl ether and post-etherified olefins. An isomerization unit is connected to the etherification unit, such that at least a portion of the post-etherified olefins enter the isomerization unit and contact with the isomerization catalyst to obtain isomerization products, which are then returned to the etherification unit for recycling. The etherification unit is also connected to the catalytic conversion reactor for recycling recycled methyl tert-butyl ether and optionally post-etherified olefins back to the catalytic conversion reactor for catalytic conversion reactions.

10. Any one and / or two or more reactor types according to claim 9; preferably, the fixed bed reactor is selected from two or more reactors connected in series / parallel, and the fluidized bed reactor is selected from one or more reactors connected in series or parallel, such as constant diameter riser, constant linear velocity riser, variable diameter riser, fluidized bed and composite reactor composed of constant diameter riser and fluidized bed, upward conveying line, downward conveying line.

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