Method for removing C7 tertiary carbon olefin in Fischer-Tropsch synthesis component

Abstract

The invention relates to the field of Fischer-Tropsch product refining, and discloses a method for removing C7 tertiary carbon olefin in Fischer-Tropsch synthesis components. According to the method, a covalent organic framework compound prepared by taking sym-tribenzaldehyde and o-sulfonic acid p-phenylenediamine as raw materials is used as an etherification catalyst, has rich sulfonic acid groups connected by covalent bonds, can stably and efficiently catalyze an etherification reaction of C7 tertiary carbon olefin and low carbon alcohol to generate high-boiling-point ether substances, and is convenient for subsequent separation. According to the etherification reaction tower used in the method, the distributor is used, the porcelain ball layer and the quartz sand layer with specific particle sizes are arranged at the upper part and the lower part of the catalyst bed layer, and the supporting and filtering device is arranged, so that the loss of the etherification catalyst is effectively avoided, the reaction efficiency and stability are improved, the service life of the catalyst bed layer is prolonged, and the generation of acid waste liquid is reduced; the method has the positive significance of high efficiency, greenness and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of Fischer-Tropsch product refining, and more specifically to a method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components. Background Technology

[0002] Coal liquefaction to synthesize oil (direct liquefaction and indirect liquefaction) is one of the important ways to alleviate the supply and demand contradiction of oil and gas resources, and can improve the comprehensive utilization value of coal. Coal indirect liquefaction technology is a relatively mature and widely used coal-to-oil technology. Its core reaction is the Fischer-Tropsch synthesis reaction, which is characterized by a wide distribution and complex composition of product mixtures, covering various products with carbon atoms from C1 to C100. The main products include α-olefins, n-alkanes, inner alkenes, and oxygen-containing compounds such as alcohols, ketones, aldehydes, esters, and acids. The content of α-olefins is 30-70%, the content of inner alkenes is 1-20%, and the content of oxides is 1-20%. For further utilization, effective separation of products is required.

[0003] With the development of the polyolefin industry, high-end materials such as low-density linear polyethylene, high-density polyethylene, and polyolefin elastomers have experienced rapid growth. The production capacity of high-carbon α-olefins, their raw materials, has also increased accordingly, primarily from ethylene oligomerization. However, the products of ethylene oligomerization are mostly even-numbered carbon olefins, limiting the use of odd-numbered carbon α-olefins such as 1-heptene. Currently, 1-heptene is mainly obtained from paraffin cracking and the separation of Fischer-Tropsch synthesis products. Separating 1-heptene from Fischer-Tropsch synthesis oil has the advantages of a shorter process and lower cost. However, due to the complexity of Fischer-Tropsch synthesis products, which contain near-boiling C7 tertiary carbon olefins of 1-heptene, ordinary distillation techniques cannot separate high-purity 1-heptene. Although methods exist to convert shorter-chain even-numbered carbon tertiary carbon olefins into high-boiling-point ethers through etherification, thus reducing separation difficulty, the longer carbon chains of C7 tertiary carbon olefins and their varying reaction patterns necessitate the design of matching etherification catalysts and reactors. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of poor etherification reaction performance, low reaction efficiency, and easy loss of catalyst activity in existing Fischer-Tropsch synthesis components, and to provide a method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components. This method is carried out in a designed etherification reactor, which includes a catalyst bed containing a covalent organic framework compound. This covalent organic framework compound contains abundant sulfonic acid groups linked by covalent bonds, possesses a large number of acidic sites, and efficiently catalyzes the etherification reaction. The sulfonic acid groups are firmly linked by covalent bonds, making them difficult to detach and lose, thus avoiding the generation of acidic waste liquid and facilitating long-term stable use. The etherification reactor used in this method uses a distributor at the top of the tower to ensure uniform contact between the raw material and the catalyst bed, preventing direct impact of the raw material flow on the catalyst and thus preventing catalyst damage. The catalyst bed has a multi-layer structure, consisting of multiple layers of quartz sand and ceramic balls arranged above and below the etherification catalyst layer containing covalent organic framework compounds, with designed particle sizes for the quartz sand and ceramic balls. This ensures that the raw material can pass through the catalyst bed quickly while preventing catalyst loss. A support filter device is installed below the catalyst bed, which further prevents catalyst loss with the reaction flow by setting a pre-reserved opening and a filter cap that only allows the product mixture to pass through.

[0005] To achieve the above objectives, the present invention provides a method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components, comprising the following steps: (S1) The Fischer-Tropsch synthesis component containing a C7 tertiary olefin is mixed with a lower alcohol to obtain a mixed feedstock. (S2) The mixed raw materials are fed into the etherification reaction tower for etherification reaction, wherein the catalyst bed in the etherification reaction tower contains a covalent organic framework compound, which is the reaction product of mestobenzoaldehyde and p-phenylenediamine o-sulfonic acid under the catalysis of trifluoroacetic acid. Wherein, the lower alcohol is a C1-C6 fatty alcohol, and the C7 tertiary olefin is at least one of 2-methyl-1-hexene, 2-methyl-2-hexene, 3-methyl-2-hexene, and 3-methyl-3-hexene.

[0006] Preferably, the lower alcohol is a C1-C4 fatty alcohol.

[0007] Preferably, the catalyst bed comprises, from top to bottom, a first ceramic ball layer, an etherified catalyst layer, a quartz sand layer, and a second ceramic ball layer, wherein the etherified catalyst layer contains the covalent organic framework compound.

[0008] Preferably, the first ceramic ball layer comprises two layers of ceramic balls with different particle sizes. More preferably, the particle size of the upper ceramic ball layer is 26-35 mm, and the particle size of the lower ceramic ball layer is 16-25 mm.

[0009] Preferably, the second ceramic ball layer comprises three layers of ceramic balls with different particle sizes. More preferably, the particle size of the upper ceramic ball layer is 8-13 mm, the particle size of the middle ceramic ball layer is 16-25 mm, and the particle size of the lower ceramic ball layer is 26-35 mm.

[0010] Preferably, the quartz sand layer comprises three layers of quartz sand with different particle sizes. More preferably, the particle size of the upper layer of quartz sand is 1.5~2.5mm, the particle size of the middle layer of quartz sand is 2.6~3.5mm, and the particle size of the lower layer of quartz sand is 3.6~4.5mm.

[0011] Preferably, in step (S1), the content of C7 tertiary olefins in the Fischer-Tropsch synthesis component is 0.01~1wt%.

[0012] Preferably, in step (S1), the molar ratio of the Fischer-Tropsch synthesis component, calculated as a C7 tertiary olefin, to the lower alcohol is 1:1 to 5.

[0013] Preferably, in step (S2), the conditions for the etherification reaction include: a temperature of 15~120℃ and a pressure of 0.1~1MPa.

[0014] Preferably, the method further includes preparing the covalent organic framework compound by mixing triphenylaldehyde, p-phenylenediamine o-sulfonic acid and trifluoroacetic acid, and reacting them under sealed conditions at 0.1~0.5 MPa and 150~200°C for 18~36 h.

[0015] Preferably, the etherification reaction tower includes a tower body and, from top to bottom, a feeding device, a catalyst bed, a support and filtration device, and a discharging device, wherein, The tower body includes an upper end cap, a cylindrical body, and a lower end cap. The feeding device is used to feed the mixed raw materials into the tower and spray them evenly onto the catalyst bed. The supporting filtration device is connected to the cylindrical body and is used to support the catalyst bed and filter the product mixture obtained from the etherification reaction.

[0016] Preferably, the feeding device includes a feeding pipe and a distributor connected thereto. The feeding pipe is located in the middle of the upper end cap. The bottom surface of the distributor is provided with a plurality of nozzles arranged sequentially from the center to the edge for uniformly spraying the mixed raw materials onto the catalyst bed.

[0017] Preferably, the supporting filter device has several reserved openings, and the reserved openings are fitted with filter caps that only allow the product mixture to pass through.

[0018] Preferably, the discharge device includes a discharge pipe and a liquid collector. The liquid collector is located in the middle of the lower end cap and its bottom is connected to the discharge pipe. It is used to collect the filtered product mixture and discharge it.

[0019] The method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components according to the present invention is carried out in a designed etherification reactor. The etherification reactor includes a catalyst bed containing a covalent organic framework compound. This covalent organic framework compound contains abundant sulfonic acid groups linked by covalent bonds, possessing numerous acidic sites and efficiently catalyzing the etherification reaction. The sulfonic acid groups are firmly linked by covalent bonds, making them less prone to detachment and loss, thus avoiding the generation of acidic waste liquid and facilitating long-term stable use. The etherification reactor used in this method uses a distributor at the top of the tower to ensure uniform contact between the raw material and the catalyst bed, preventing direct impact from the raw material stream on the catalyst and causing catalyst damage. The catalyst bed has a multi-layered structure, with multiple layers of quartz sand and ceramic balls arranged above and below the etherification catalyst layer containing the covalent organic framework compound, and the designed particle size of the quartz sand and ceramic balls ensures rapid passage of the raw material through the catalyst bed while preventing catalyst loss. A support filter device is installed below the catalyst bed, further preventing catalyst loss with the reaction stream by setting pre-reserved openings and filter caps that only allow the product mixture to pass through. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the etherification reaction tower provided by the present invention.

[0021] Figure 2 This is a schematic diagram of the distributor of the etherification reaction tower provided by the present invention.

[0022] Figure 3 This is a schematic diagram of the supporting filtration device for the etherification reaction tower provided by the present invention.

[0023] Explanation of reference numerals in the attached figures 1. Feeding device; 11. Feed pipe; 12. Distributor; 121. Nozzle; 2. Catalyst bed; 21. First ceramic ball layer; 22. Etherification catalyst layer; 23. Quartz sand layer; 24. Second ceramic ball layer; 3. Support filter device; 31. Filter cap; 4. Discharge device; 41. Discharge pipe; 42. Liquid collector; 5. Tower body; 51. Upper head; 52. Cylinder body; 53. Lower head. Detailed Implementation

[0024] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] This invention provides a method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components, comprising the following steps: (S1) The Fischer-Tropsch synthesis component containing a C7 tertiary olefin is mixed with a lower alcohol to obtain a mixed feedstock. (S2) The mixed raw materials are fed into the etherification reaction tower for etherification reaction, wherein the catalyst bed in the etherification reaction tower contains a covalent organic framework compound, which is the reaction product of mestobenzoaldehyde and p-phenylenediamine o-sulfonic acid under the catalysis of trifluoroacetic acid. Wherein, the lower alcohol is a C1-C6 fatty alcohol, and the C7 tertiary olefin is at least one of 2-methyl-1-hexene, 2-methyl-2-hexene, 3-methyl-2-hexene, and 3-methyl-3-hexene.

[0027] In the method of the present invention, preferably, the lower alcohol is a C1-C4 fatty alcohol.

[0028] In specific embodiments of the present invention, non-limiting examples of C1-C6 fatty alcohols include: methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol, n-pentanol, isopentanol, tert-pentanol, neopentanol, and n-hexanol. Non-limiting examples of C1-C4 fatty alcohols include: methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, and tert-butanol. In the present invention, the reaction of fatty alcohols with lower carbon atoms with C7 tertiary olefin components is more controllable, which can improve the separation efficiency after etherification.

[0029] In this invention, due to the longer carbon chain of C7 tertiary olefins, they follow different etherification reaction rules than C4 and C6 tertiary olefins. Compared to C4 and C6 tertiary olefins, they have greater steric hindrance, making etherification reactions more difficult. Furthermore, the competition for 1-heptene isomerization with the etherification reaction is more intense. Therefore, the reaction process must maintain the conversion rate of C7 tertiary olefins while minimizing the impact of olefin isomerization reactions. After the reaction, C7 tertiary olefins generate ethers mainly composed of alkyl tertiary hexyl ethers such as methyl tertiary hexyl ether, ethyl tertiary hexyl ether, and propyl tertiary hexyl ether. These ethers generally have boiling points above 120°C, higher than that of 1-heptene, allowing for effective separation and collection of 1-heptene through subsequent distillation. By employing a catalyst bed containing covalent organic framework compounds rich in sulfonic acid groups, not only are more acidic sites provided for efficient catalysis of the etherification reaction, but the sulfonic acid groups are also firmly connected to the catalyst via covalent bonds, preventing catalytic activity loss and extending the catalyst's lifespan.

[0030] In a preferred embodiment of the present invention, the covalent organic framework compound has a structure as shown in formula (I). Formula (I) Using covalent organic framework compounds with the above structure as catalysts for etherification reactions can provide a large number of acidic sulfonic acid groups as active sites, thereby improving the efficiency of the catalytic reaction. The sulfonic acid groups are connected by covalent bonds, which greatly improves the stability of the sulfonic acid groups and avoids the loss of catalyst activity. Compared with supported sulfonic acid modified resins, it has better catalyst stability.

[0031] In the method of the present invention, in a preferred embodiment, the catalyst bed comprises a first ceramic ball layer 21, an etherification catalyst layer 22, a quartz sand layer 23, and a second ceramic ball layer 24 arranged sequentially from top to bottom.

[0032] In the method of the present invention, preferably, the first ceramic ball layer 21 comprises two layers of ceramic balls with different particle sizes. More preferably, the particle size of the upper ceramic ball layer is 26-35 mm, more preferably 27-33 mm; and the particle size of the lower ceramic ball layer is 16-25 mm, more preferably 17-23 mm. In the present invention, using ceramic balls with a larger particle size in the upper layer and a smaller particle size in the lower layer facilitates the rapid penetration of the mixed raw materials into the catalyst bed for etherification reaction.

[0033] In the method of the present invention, preferably, the second ceramic ball layer 24 comprises three layers of ceramic balls with different particle sizes. More preferably, the particle size of the upper ceramic ball layer is 8-13 mm, more preferably 9-12 mm; the particle size of the middle ceramic ball layer is 16-25 mm, more preferably 17-23 mm; and the particle size of the lower ceramic ball layer is 26-35 mm, more preferably 27-33 mm. In the present invention, the second ceramic ball layer 24 located below the catalyst bed adopts a three-layer design with the particle size increasing from top to bottom. This is beneficial to prevent covalent organic framework compounds from flowing out of the catalyst bed with the reaction mixture, causing a loss of catalyst activity. The pores formed by the ceramic balls increase from top to bottom, creating a filter pore structure similar to that used in mechanical filtration components. This facilitates the reduction of flow resistance of the reaction mixture and avoids the accumulation and blockage of small solid particles that may be carried by the reaction mixture during long-term use.

[0034] In the method of the present invention, preferably, the quartz sand layer 23 comprises three layers of quartz sand with different particle sizes. More preferably, the particle size of the upper layer of quartz sand is 1.5~2.5 mm, the particle size of the middle layer of quartz sand is 2.6~3.5 mm, and the particle size of the lower layer of quartz sand is 3.6~4.5 mm. More preferably, the particle size of the upper layer of quartz sand is 1.7~2.3 mm, the particle size of the middle layer of quartz sand is 2.7~3.3 mm, and the particle size of the lower layer of quartz sand is 3.7~4.3 mm. In the present invention, the decreasing particle size of the quartz sand from top to bottom can reduce the flow resistance of the reaction mixture and avoid clogging.

[0035] In a specific embodiment of the present invention, a wire mesh, preferably a corrosion-resistant wire mesh made of stainless steel, is provided between the quartz sand layer 23 and the second ceramic ball layer 24 to fix and isolate the quartz sand layer, so as to prevent the quartz sand layer with smaller particle size from mixing with the ceramic ball layer under the impact of the reaction material for a long time, which would lead to poor flow of the reaction material.

[0036] In the method of the present invention, preferably, in step (S1), the content of C7 tertiary olefins in the Fischer-Tropsch synthesis component is 0.01~1 wt%. More preferably, the content of C7 tertiary olefins in the Fischer-Tropsch synthesis component is 0.1~0.7 wt%.

[0037] In the method of the present invention, preferably, in step (S1), the molar ratio of the Fischer-Tropsch synthesis component (based on C7 tertiary olefins) to the lower alcohol is 1:1 to 5. More preferably, it is 1:2 to 4. In the present invention, the above-mentioned proportion of raw materials ensures that the lower alcohol reacts fully with the C7 tertiary olefins in the Fischer-Tropsch synthesis component to obtain high-boiling-point ethers, and reduces the content of C7 tertiary olefins in the 1-heptene obtained after separation.

[0038] In the method of the present invention, preferably, in step (S2), the etherification reaction conditions include: a temperature of 15-120°C and a pressure of 0.1-1 MPa. More preferably, the etherification reaction conditions include: a temperature of 50-100°C and a pressure of 0.1-0.5 MPa. In the present invention, the above etherification reaction conditions enable the efficient conversion of C7 tertiary olefins into high-boiling-point ethers, which is beneficial for the subsequent separation and recovery of 1-heptene.

[0039] In a preferred embodiment of the method of the present invention, the method further includes preparing the covalent organic framework compound by reacting mesitylene formaldehyde with p-phenylenediamine o-sulfonate under the catalysis of trifluoroacetic acid.

[0040] In the method of the present invention, preferably, the reaction is carried out under sealed conditions, at 0.1~0.5MPa and 150~200°C for 18~36h.

[0041] In a specific embodiment of the present invention, the preparation method of the covalent organic framework compound includes the following steps: mixing triphenylmethane and p-phenylenediamine o-sulfonic acid at a molar ratio of 1:1~2, then adding trifluoroacetic acid (the molar volume ratio of triphenylmethane to trifluoroacetic acid is 1 mol: 8~12 mL), and then letting the resulting mixture stand for 18~36 h under sealed conditions, 0.1~0.5 MPa and 150~200 °C.

[0042] In the method of the present invention, preferably, the etherification reaction tower includes a tower body 5 and, from top to bottom, a feeding device 1, a catalyst bed 2, a support and filtration device 3, and a discharging device 4, wherein, The tower body 5 includes an upper end cap 51, a cylinder 52, and a lower end cap 53. The feeding device 1 is used to feed the mixed raw materials into the tower and spray them evenly onto the catalyst bed 2. The support and filtration device 3 is connected to the cylinder 52 and is used to support the catalyst bed 2 and filter the product mixture obtained from the etherification reaction.

[0043] In a specific embodiment of the present invention, the upper end cap 51 is also provided with lifting lugs and tower top lifting columns to facilitate hoisting and disassembly.

[0044] In the method of the present invention, preferably, the feeding device 1 includes a feed pipe 11 and a distributor 12 connected thereto. The feed pipe is located at the middle position of the upper end cap 51. The bottom surface of the distributor 12 has a plurality of nozzles 121 arranged sequentially from the center to the edge for uniformly spraying the mixed raw materials onto the catalyst bed 2. In the present invention, by designing and using a dedicated distributor 12, the mixed raw materials can be uniformly distributed in the reaction tower, avoiding flow deviation and 1-heptene isomerization caused by uneven reaction.

[0045] In the method of the present invention, preferably, the supporting filter device 3 has a plurality of reserved openings, and the reserved openings are fitted with filter caps 31 that only allow the product mixture to pass through. In the present invention, the filter caps 31 can effectively prevent the etherification catalyst from being lost with the reaction stream, thereby avoiding a decrease in the overall activity of the catalyst bed due to leakage.

[0046] In the method of the present invention, in a preferred embodiment, the discharge device 4 includes a discharge pipe 41 and a liquid collector 42. The liquid collector 42 is located in the middle of the lower end cap 53 and its bottom is connected to the discharge pipe 41. It is used to collect the filtered product mixture and discharge it.

[0047] In a specific embodiment of the present invention, the side wall of the cylinder 52 may also be provided with several temperature measuring ports that are in contact with the catalyst for real-time monitoring of changes in reaction temperature, so as to facilitate control of the reaction; the lower side of the cylinder 52 may also be provided with a catalyst discharge port for replacing the catalyst; all components in the etherification reaction tower that are in contact with the reactants are preferably made of corrosion-resistant materials. Specifically, the internal components of the tower are preferably made of 316L steel, and the inner wall of the tower is preferably made of corrosion-resistant composite material.

[0048] In a specific embodiment of the present invention, the method of the present invention is as follows: Figure 1 The etherification reaction is carried out in the etherification tower shown. The etherification reaction tower includes a tower body 5 and, from top to bottom, a feed device 1, a catalyst bed 2, a support filter device 3, and a discharge device 4. The tower body 5 includes an upper end cap 51, a cylindrical body 52, and a lower end cap 53; The feeding device 1 includes a feed pipe 11 and a distributor 12 connected thereto. The feed pipe is located at the middle position of the upper end cap 51 and is used to feed the mixed raw materials into the tower. The bottom surface of the distributor 12 is as follows: Figure 2 As shown, a plurality of nozzles 121 are arranged sequentially from the center to the edge, for uniformly spraying the mixed raw materials onto the catalyst bed 2; The catalyst bed 2 comprises, from top to bottom, a first ceramic ball layer 21, an etherification catalyst layer 22, a quartz sand layer 23, and a second ceramic ball layer 24. The first ceramic ball layer 21 comprises two layers of ceramic balls with different particle sizes: the upper layer has a particle size of 26-35 mm, and the lower layer has a particle size of 16-25 mm. The quartz sand layer 23 comprises three layers of quartz sand with different particle sizes: the upper layer has a particle size of 1.5-2.5 mm, the middle layer has a particle size of 2.6-3.5 mm, and the lower layer has a particle size of 3.6-4.5 mm. The second ceramic ball layer 24 comprises three layers of ceramic balls with different particle sizes: the upper layer has a particle size of 8-13 mm, the middle layer has a particle size of 16-25 mm, and the lower layer has a particle size of 26-35 mm. The etherification catalyst layer 22 contains a covalent organic framework compound as shown in formula (I). Formula (I) The support and filtration device 3 is connected to the cylindrical body 52 and is used to support the catalyst bed 2 and filter the product mixture obtained from the etherification reaction. The support and filtration device 3 has the following features: Figure 3 The diagram shows several reserved openings, each of which is fitted with a filter cap 31 that only allows the product mixture to pass through; The discharge device 4 includes a discharge pipe 41 and a liquid collector 42. The liquid collector 42 is located in the middle of the lower end cap 53 and its bottom is connected to the discharge pipe 41. It is used to collect the filtered product mixture and discharge it.

[0049] In a specific embodiment of the present invention, the etherification catalyst filled in the etherification catalyst layer 22 is a covalent organic framework compound COF-SO3H obtained by molding, preferably in a spherical shape. The specific molding process includes: adding the covalent organic framework compound COF-SO3H to 15% of its mass of hydroxypropyl methylcellulose and 15% of the pore-forming agent NH4HCO3 and mixing them evenly, then mixing them with an ethanol aqueous solution (water:ethanol volume ratio of 7:3) in a disc granulator for granulation, the granulation particle size is 0.5~3mm, and then vacuum drying the obtained spherical particles at 60~80℃ for 3~5h to obtain the etherification catalyst filled in the etherification catalyst layer 22.

[0050] The method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components according to the present invention is carried out in a designed etherification reactor. The etherification reactor includes a catalyst bed containing a covalent organic framework compound. This covalent organic framework compound contains abundant covalently linked sulfonic acid groups, possessing numerous acidic sites and efficiently catalyzing the etherification reaction. The sulfonic acid groups are firmly linked by covalent bonds, making them less prone to detachment and loss, thus avoiding the generation of acidic waste liquid and facilitating long-term stable use. The etherification reactor used in this method uses a distributor at the top of the tower to ensure uniform contact between the raw material and the catalyst bed, preventing direct impact from the raw material stream on the catalyst and causing catalyst damage. The catalyst bed has a multi-layered structure, with multiple layers of quartz sand and ceramic balls arranged above and below the etherification catalyst layer containing the covalent organic framework compound, and the designed particle size of the quartz sand and ceramic balls ensures rapid passage of the raw material through the catalyst bed while preventing catalyst loss. A support filter device is installed below the catalyst bed, further preventing catalyst loss with the reaction stream by setting pre-reserved openings and filter caps that only allow the product mixture to pass through.

[0051] The following examples further illustrate a method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0052] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0053] In the embodiments and comparative examples of the present invention, the etherification catalyst layer 22 of the present invention contains an etherification catalyst, which contains a covalent organic framework compound COF-SO3H, and the COF-SO3H is prepared by the method shown in formula (A). Formula (A) The specific steps are as follows: First, mix 0.01 mol of triphenylformaldehyde and 0.015 mol of o-sulfonic acid p-phenylenediamine evenly in a glass reaction tube, and then add 0.1 mL of trifluoroacetic acid; then, seal the glass reaction tube and let it stand at 180°C for 24 h; finally, after the solid in the glass reaction tube cools to room temperature, take out the obtained solid, grind and pulverize it, and wash it with DMF and ethanol in sequence, and then dry it under vacuum at 50°C. The obtained solid powder is denoted as COF-SO3H.

[0054] The etherification catalyst is obtained by molding a covalent organic framework compound COF-SO3H. The molding process includes: adding 15% of COF-SO3H by mass of hydroxypropyl methylcellulose and 15% of pore-forming agent NH4HCO3 and mixing them evenly; then mixing them with an ethanol-water solution (water:ethanol volume ratio of 7:3) in a disc granulator for granulation, with a particle size of 2.5 mm; and then vacuum drying the resulting spherical particles at 75°C for 4 h to obtain the etherification catalyst.

[0055] In the embodiments and comparative examples of the present invention, the method of the present invention for removing C7 tertiary olefins from Fischer-Tropsch synthesis components is as follows: Figure 1 The etherification reaction is carried out in the etherification tower shown. This apparatus includes a tower body 5 and, from top to bottom, a feed device 1, a catalyst bed 2, a support filter device 3, and a discharge device 4. The tower body 5 includes an upper end cap 51, a cylindrical body 52, and a lower end cap 53; The feeding device 1 includes a feeding pipe 11 and a distributor 12 connected thereto. The feeding pipe is located in the middle of the upper end cap 51. The bottom surface of the distributor 12 is provided with a plurality of nozzles 121 from the center to the edge. The catalyst bed 2 comprises, from top to bottom, a first ceramic ball layer 21, an etherification catalyst layer 22, a quartz sand layer 23, and a second ceramic ball layer 24. The first ceramic ball layer 21 comprises two layers of ceramic balls with different particle sizes, the upper layer having a particle size of 30 mm and the lower layer having a particle size of 20 mm. The quartz sand layer 23 comprises three layers of quartz sand with different particle sizes, the upper layer having a particle size of 2 mm, the middle layer having a particle size of 3 mm, and the lower layer having a particle size of 4 mm. The second ceramic ball layer 24 comprises three layers of ceramic balls with different particle sizes, the upper layer having a particle size of 10 mm, the middle layer having a particle size of 20 mm, and the lower layer having a particle size of 30 mm. The etherification catalyst layer 22 contains an etherification catalyst, which contains the aforementioned covalent organic framework compound COF-SO3H. The supporting filter device 3 is connected to the cylinder 52. The supporting filter device 3 has several reserved openings, and the reserved openings are equipped with filter caps 31 that only allow the product mixture to pass through. The discharge device 4 includes a discharge pipe 41 and a liquid collector 42. The liquid collector 42 is located in the middle of the lower end cap 53 and its bottom is connected to the discharge pipe 41. It is used to collect the filtered product mixture and discharge it.

[0056] In the embodiments and comparative examples of the present invention, the Fischer-Tropsch synthesis components containing C7 tertiary carbon olefins used are mainly derived from the Fischer-Tropsch synthesis reaction and obtained by distillation as a mixed component containing C7. The components mainly contain 0.1-1% C7 tertiary carbon olefins, 30-70% 1-heptene, 30-70% heptane, and 0.1-3% pentanol and pentanal, etc., which are oxygen-containing organic compounds. The main components of the C7 tertiary carbon olefins are 0.1-1% 2-methyl-1-hexene, 0-0.1% 2-methyl-2-hexene, 0-0.1% 3-methyl-2-hexene, and 0-0.1% 3-methyl-3-hexene.

[0057] Example 1 (S1) The Fischer-Tropsch synthesis component containing 1 wt% C7 tertiary olefin was mixed with methanol at a molar ratio of C7 tertiary olefin to methanol of 1:3 to obtain a mixed feedstock; (S2) The mixed raw materials are fed into the upper head 51 of the etherification reaction tower through the feed pipe 11 and evenly sprayed onto the catalyst bed 2 through the distributor 12. Then, they flow through the first ceramic ball layer 21 and come into contact with the covalent organic framework compound COF-SO3H in the etherification catalyst layer 22. The reaction is carried out at 70°C and 0.3MPa. The resulting product mixture flows through the quartz sand layer 23 and the second ceramic ball layer 24 in sequence. It enters the lower head 53 through the reserved port on the support filter device 3 and is finally collected by the liquid collector 42 and leaves the etherification reaction tower through the discharge pipe 41.

[0058] Example 2 The method of Example 1 is adopted, except that methanol is replaced with ethanol, and the particle size of the upper ceramic ball of the first ceramic ball layer 21 is adjusted to 26 mm and the particle size of the lower ceramic ball is adjusted to 23 mm; the particle size of the upper quartz sand of the quartz sand layer 23 is adjusted to 1.5 mm, the particle size of the middle quartz sand is adjusted to 2.8 mm, and the particle size of the upper quartz sand is adjusted to 4.4 mm; the particle size of the upper ceramic ball of the second ceramic ball layer 24 is adjusted to 8 mm, the particle size of the middle ceramic ball is adjusted to 18 mm, and the particle size of the lower ceramic ball is adjusted to 35 mm.

[0059] Example 3 The method of Example 1 is adopted, except that methanol is replaced with propanol, and the particle size of the upper ceramic ball of the first ceramic ball layer 21 is adjusted to 35 mm and the particle size of the lower ceramic ball is adjusted to 16 mm; the particle size of the upper quartz sand of the quartz sand layer 23 is adjusted to 2.5 mm, the particle size of the middle quartz sand is adjusted to 3.3 mm, and the particle size of the upper quartz sand is adjusted to 3.8 mm; the particle size of the upper ceramic ball of the second ceramic ball layer 24 is adjusted to 13 mm, the particle size of the middle ceramic ball is adjusted to 24 mm, and the particle size of the lower ceramic ball is adjusted to 28 mm.

[0060] Example 4 The method of Example 1 was adopted, except that when preparing the covalent organic framework compound, the amount of methyltriphenylaldehyde was adjusted to 0.015 mol and the amount of p-phenylenediamine o-sulfonic acid was 0.015 mol; the Fischer-Tropsch synthesis component containing 0.8% C7 tertiary olefin was mixed with methanol at a molar ratio of C7 tertiary olefin to methanol of 1:5 to obtain the mixed raw material.

[0061] Example 5 The method of Example 1 was adopted, except that when preparing the covalent organic framework compound, the amount of methyltriphenylaldehyde was adjusted to 0.01 mol and the amount of p-phenylenediamine o-sulfonic acid was 0.02 mol; a Fischer-Tropsch synthesis component containing 0.5% C7 tertiary olefin was mixed with isopropanol at a molar ratio of C7 tertiary olefin to methanol of 1:4 to obtain a mixed raw material.

[0062] Example 6 The method of Example 1 was adopted, except that the amount of trifluoroacetic acid was adjusted to 0.08 mL when preparing the covalent organic framework compound; a Fischer-Tropsch synthesis component containing 1% C7 tertiary olefin was mixed with tert-butanol at a molar ratio of C7 tertiary olefin to methanol of 1:3 to obtain a mixed raw material.

[0063] Example 7 The method of Example 1 was adopted, except that the amount of trifluoroacetic acid was adjusted to 0.11 mL when preparing the covalent organic framework compound; the Fischer-Tropsch synthesis component containing 1% C7 tertiary olefin was mixed with hexanol at a molar ratio of C7 tertiary olefin to methanol of 1:3 to obtain the mixed raw material.

[0064] Example 8 The method of Example 1 was used, except that the mixed raw materials were contacted with the covalent organic framework compound COF-SO3H and reacted at 80°C and 0.2 MPa.

[0065] Example 9 The method of Example 2 was used, except that the mixed raw materials were contacted with the covalent organic framework compound COF-SO3H and reacted at 90°C and 0.6 MPa.

[0066] Example 10 The method of Example 3 was used, except that the mixed raw materials were contacted with the covalent organic framework compound COF-SO3H and reacted at 60°C and 1 MPa.

[0067] Example 11 The method of Example 1 is adopted, except that the positions of the upper and lower ceramic balls in the first ceramic ball layer 21 are exchanged, the positions of the upper and lower quartz sand layers in the quartz sand layer 23 are exchanged, and the positions of the upper and lower ceramic balls in the second ceramic ball layer 24 are exchanged. That is, the particle size of the ceramic balls in the first ceramic ball layer 21 increases from top to bottom, and the particle size of the quartz sand in the quartz sand layer 23 and the particle size of the ceramic balls in the second ceramic ball layer 24 decreases from top to bottom.

[0068] Example 12 The method of Embodiment 1 is adopted, except that the filter cap 31 provided on the reserved port of the support filter device 3 is removed.

[0069] Comparative Example 1 The method of Example 1 was used, except that the covalent organic framework compound COF-SO3H was replaced with a macroporous sulfonic acid resin catalyst.

[0070] Comparative Example 2 The method of Example 1 was used, except that the covalent organic framework compound COF-SO3H was replaced with a ZSM-5 molecular sieve catalyst.

[0071] Comparative Example 3 The method of Example 1 was used, except that the covalent organic framework compound COF-SO3H was replaced with a heteropolyacid catalyst.

[0072] Test Example 1 Samples of the mixed raw materials and product mixtures of Examples 1-12 and Comparative Examples 1-3 were taken at the feed pipe 11 and the discharge pipe 41, respectively. The contents of C7 tertiary olefins, 1-hepten, lower alcohols, and ethers (ethers in the mixed raw materials were essentially zero and are not detailed in Table 1) in the sampled samples were analyzed by gas chromatography. The sampling time was 100 hours after the reaction. The results are shown in Table 1. Table 1

[0073] As shown in Table 1, the method for removing C7 tertiary olefins from the Fischer-Tropsch synthesis components described in this invention can effectively convert C7 tertiary olefins into higher-boiling-point ethers. The conversion rate of C7 tertiary olefins is generally higher than 90%, and 1-heptene is almost unaffected in the etherification reaction, facilitating subsequent distillation to obtain high-purity 1-heptene and improving the efficiency of 1-heptene extraction. The content of lower alcohols in the Fischer-Tropsch synthesis components is slightly reduced, proving that the reaction does indeed consume lower alcohols and undergo etherification with C7 tertiary olefins. Compared with the test results of Comparative Examples 1-3, the covalent organic framework compound COF-SO3H used in the method of this invention has significantly better catalytic effect, effectively improving the conversion rate of C7 tertiary olefins into ethers via etherification. The method of this invention uses a distributor design to ensure uniform catalyst distribution and utilizes the flow distribution of the first ceramic ball layer to ensure uniform entry of the mixed raw materials into the catalyst bed for etherification, making the reaction more uniform and controllable, reducing the loss caused by the isomerization reaction of 1-heptene, and extending the overall service life of the catalyst bed.

[0074] Test Example 2 Using the sampling and testing methods of Test Example 1, samples were taken from mixtures of products from Examples 1-12 and Comparative Examples 1-3, and the contents of C7 tertiary olefins, 1-heptene, lower alcohols, and ethers in the product mixtures were tested. Sampling times were 1000 h and 2000 h after the reaction. The results are shown in Table 2. Table 2

[0075] As shown in Table 2, the method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components described in this invention can stably and effectively convert C7 tertiary olefins into higher-boiling-point ethers over a relatively long operating time. This indicates that the covalent organic framework compound used as a catalyst for the etherification reaction has good stability. This is because the sulfonic acid groups that play a catalytic role are connected by covalent bonds and are not easily lost during the catalytic etherification reaction. In addition, the use of a distributor and a first ceramic ball layer above the catalyst bed effectively disperses the reaction stream, reducing the impact of the reaction stream on the catalyst bed, thereby reducing the loss of catalyst activity. The uniform stream also avoids excessive local activity loss caused by uneven reaction. The support and filtration device set below the catalyst bed further prevents the loss of a very small number of detached or broken catalysts with the reaction stream, further extending the overall life of the catalyst bed. As a result, compared with the comparative example, the embodiments of this invention can still maintain good etherification reaction efficiency and prevent catalyst leakage after a long operating time.

[0076] Furthermore, visual testing with pH test paper showed that the pH value of the product mixture prepared by the method of the present invention did not decrease significantly after 1000 hours of operation, indicating that almost no sulfonic acid groups in the catalyst were detached. This is because the sulfonic acid groups in the etherification catalyst of the present invention are connected by covalent bonds, exhibiting good stability. This maintains the catalytic etherification reaction efficiency during long-term use and reduces the corrosion of equipment and the resulting acidic wastewater discharge caused by detached sulfonic acid groups, making it more environmentally friendly. Filtering and visually inspecting the product mixture after 1000 hours of reaction revealed that the product mixture of Example 12 contained a small amount of solid particles, while those of Examples 1-11 did not. This indicates that the filter cap effectively intercepted a very small amount of catalyst and solid impurities, reducing the potential safety risk of interfering with subsequent distillation extraction of 1-heptene.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for removing C7 tertiary olefins from Fischer-Tropsch synthesis components, characterized in that, The method includes the following steps: (S1) The Fischer-Tropsch synthesis component containing C7 tertiary olefins is mixed with a lower alcohol to obtain a mixed feedstock; (S2) The mixed raw materials are fed into an etherification reaction tower for etherification reaction, wherein the catalyst bed in the etherification reaction tower contains a covalent organic framework compound, which is the reaction product of mestribenzaldehyde and p-phenylenediamine o-sulfonic acid under the catalysis of trifluoroacetic acid. Wherein, the lower alcohol is a C1-C6 fatty alcohol, and the C7 tertiary olefin is at least one of 2-methyl-1-hexene, 2-methyl-2-hexene, 3-methyl-2-hexene, and 3-methyl-3-hexene.

2. The method according to claim 1, characterized in that, The lower alcohols are C1-C4 fatty alcohols.

3. The method according to claim 1 or 2, characterized in that, The catalyst bed comprises, from top to bottom, a first ceramic ball layer (21), an etherified catalyst layer (22), a quartz sand layer (23), and a second ceramic ball layer (24), wherein the etherified catalyst layer (22) contains the covalent organic framework compound; The first ceramic ball layer (21) includes two layers of ceramic balls with different particle sizes. Preferably, the particle size of the upper ceramic ball is 26-35 mm and the particle size of the lower ceramic ball is 16-25 mm. The second ceramic ball layer (24) includes three layers of ceramic balls with different particle sizes. Preferably, the particle size of the upper ceramic ball layer is 8~13mm, the particle size of the middle ceramic ball layer is 16~25mm, and the particle size of the lower ceramic ball layer is 26~35mm. The quartz sand layer (23) comprises three layers of quartz sand with different particle sizes. Preferably, the upper layer of quartz sand has a particle size of 1.5~2.5mm, the middle layer of quartz sand has a particle size of 2.6~3.5mm, and the lower layer of quartz sand has a particle size of 3.6~4.5mm.

4. The method according to any one of claims 1-3, characterized in that, In step (S1), the content of C7 tertiary olefins in the Fischer-Tropsch synthesis component is 0.01~1wt%.

5. The method according to any one of claims 1-4, characterized in that, In step (S1), the molar ratio of the Fischer-Tropsch synthesis component, calculated as a C7 tertiary olefin, to the lower alcohol is 1:1 to 5.

6. The method according to any one of claims 1-5, characterized in that, In step (S2), the conditions for the etherification reaction include: a temperature of 15~120℃ and a pressure of 0.1~1MPa.

7. The method according to any one of claims 1-6, characterized in that, The method further includes preparing the covalent organic framework compound by mixing triphenylaldehyde, p-phenylenediamine o-sulfonic acid and trifluoroacetic acid, and reacting them under sealed conditions at 0.1~0.5 MPa and 150~200°C for 18~36 h.

8. The method according to any one of claims 1-7, characterized in that, The etherification reaction tower includes a tower body (5) and, from top to bottom, a feeding device (1), a catalyst bed (2), a support and filtration device (3), and a discharge device (4), wherein, The tower body (5) includes an upper end cap (51), a cylinder (52) and a lower end cap (53). The feeding device (1) is used to feed the mixed raw materials into the tower and spray them evenly on the catalyst bed (2). The support and filtration device (3) is connected to the cylinder (52) and is used to support the catalyst bed (2) and filter the product mixture obtained from the etherification reaction.

9. The method according to claim 8, characterized in that, The feeding device (1) includes a feed pipe (11) and a distributor (12) connected thereto. The feed pipe is located in the middle of the upper end cap (51). The bottom surface of the distributor (12) is provided with a number of nozzles (121) from the center to the edge, which are used to spray the mixed raw materials evenly onto the catalyst bed (2).

10. The method according to claim 8 or 9, characterized in that, The supporting filter device (3) has several reserved openings, and the reserved openings are equipped with filter caps (31) that only allow the product mixture to pass through.

11. The method according to any one of claims 8-10, characterized in that, The discharge device (4) includes a discharge pipe (41) and a liquid collector (42). The liquid collector (42) is located in the middle of the lower end cap (53) and its bottom is connected to the discharge pipe (41). It is used to collect the filtered product mixture and discharge it.

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