Process and system for mixing c4's to produce 1-butene

Abstract

This invention relates to the field of C4 separation, specifically to a method and system for producing 1-butene from mixed C4 streams. The method includes: S1. Distilling the mixed C4 streams to obtain a 1-butene-rich stream, a butadiene-containing stream, and a heavy C4 stream; S2. Removing light components from the 1-butene-rich stream to obtain a 1-butene product stream; S3. Selectively hydrogenating the butadiene-containing stream to obtain a selectively hydrogenated product stream; S4. Performing a double bond isomerization reaction on at least a portion of the heavy C4 stream to obtain a double bond isomerization product stream; wherein the selectively hydrogenated product stream and the double bond isomerization product stream are returned to step S1 for the distillation separation. This invention simplifies the process flow, reduces investment, lowers system energy consumption, and achieves efficient recovery of 1-butene and efficient utilization of 2-butene.

Description

Technical Field

[0001] This invention relates to the field of C4 separation, and more specifically to a method and system for producing 1-butene from mixed C4 atoms. Background Technology

[0002] In recent years, my country's oil refining scale, reaching tens of millions of tons, has been continuously expanding, leading to a rapid increase in by-product C4 resources. C4 fractions mainly include: 1) gas-derived C4 from the gas separation unit of a refinery's catalytic cracking unit; 2) raffinate C4 from ethylene steam cracking units after butadiene extraction; and 3) by-product C4 from MTO units. The raffinate C4 from ethylene cracking units is typically processed by an MTBE / 1-butene separation unit to produce MTBE and 1-butene. However, the utilization rate of refinery gas-derived C4 and MTO by-product C4 is relatively low; they are mainly converted to MTBE through etherification with methanol and isobutene, thus generating a large amount of post-etherified C4.

[0003] One way to utilize post-etherified C4 is to separate 1-butene products via a 1-butene precision distillation unit. However, post-etherified C4 contains not only 1-butene but also a large amount of 2-butene, with the 2-butene content being more than twice that of 1-butene. If only the 1-butene is separated using a 1-butene separation unit, it will lead to a significant waste of 2-butene resources. One solution is to convert 2-butene to 1-butene through butene double bond isomerization, thereby increasing the production of 1-butene.

[0004] CN101514135A discloses a method for the catalytic isomerization of a C4 mixture to produce 1-butene. This method involves mixing a C4 mixture rich in 2-butene with recycled material, gasifying it, and then heating it to 300-350°C. A solid acid catalyst (80% SiO2 and 20% Al2O3) is used to carry out a catalytic isomerization reaction. The reaction product is separated by a concentration tower to obtain a mixture rich in 1-butene. This 1-butene-rich mixture is then used in an existing 1-butene separation unit for 1-butene separation, achieving the goal of converting 2-butene to increase 1-butene production. Through 1-butene separation / 2-butene isomerization, the utilization rate of 2-butene can be significantly improved, thus increasing the yield of 1-butene.

[0005] CN218280600U discloses an apparatus for increasing the production of high-purity 1-butene. The apparatus includes a first distillation column, a second distillation column, an isomerization reactor, and a concentration column. This apparatus can effectively process post-etherification C4 feedstock. The post-etherification C4 feedstock is first separated at the top of the first distillation column to obtain a light component containing isobutane, propane, and water. The bottom feed, consisting of intermediate C4 components (containing 1-butene, n-butane, and 2-butene), is fed into the second distillation column. From the top of the second distillation column, 1-butene is separated, and the bottom feed yields a heavy C4 component containing n-butane and 2-butene. The heavy C4 component is fed into the isomerization reactor, and the reaction product is fed into the concentration column. In the concentration column, light and heavy components are separated. The top of the concentration column yields a high-concentration crude 1-butene (containing 1-butene, n-butane, etc.), while the bottom feed contains heavy C4 containing 2-butene and n-butane, which is discharged from the apparatus. Crude 1-butene is recycled to the inlet of the first distillation column, and the isomerized 1-butene produced by the first and second distillation columns is separated out.

[0006] The above process has two disadvantages: 1) Since crude butene-1 contains n-butane, this part of n-butane will circulate in the first distillation column-second distillation column-isomerization reactor-butene concentration column system, resulting in increased system equipment size and energy consumption; 2) Although the concentration column reduces the flow rate of crude butene-1 returned to the first distillation column to a certain extent, it leads to a complex process flow, more distillation columns, and large investment.

[0007] CN112707783A discloses another process for producing 1-butene via isomerization. This method first converts 1-butene to 2-butene through hydroisomerization, then converts 2-butene back to 1-butene through double bond isomerization, and finally separates the 1-butene product through precision distillation. The advantage of this method is that it removes isobutene from the feedstock without etherification through hydroisomerization and a pretreatment tower. However, this method is not suitable for processing the large quantities of C4 ethers already de-isobutene-containing by etherification in the market. This is because hydroisomerization and the pretreatment tower inevitably lead to the loss of 1-butene. Furthermore, due to the limited single-pass conversion rate of the double bond isomerization reaction (below 20%), to achieve a comparable 1-butene production capacity, the scale of the double bond isomerization and precision distillation process would be larger and more energy-intensive than the method disclosed in CN218280600U.

[0008] In summary, all existing technologies suffer from problems such as long processes, large investments, and high energy consumption. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems of long process, large investment and high energy consumption in the existing mixed C4 production of 1-butene, and to provide a method and system for mixed C4 production of 1-butene, which has the advantages of short process, small investment and low energy consumption.

[0010] To achieve the above objectives, a first aspect of the present invention provides a method for producing 1-butene by mixing C4 molecules, the method comprising: S1 mixed C4 stream was separated by distillation to obtain 1-butene-rich stream, butadiene-containing stream and heavy C4 stream; S2 1-Butene-rich stream is degraded by removing light components to obtain 1-butene product stream; S3 butadiene-containing stream is selectively hydrogenated to obtain selectively hydrogenated product stream; S4 at least part of the heavy C4 stream undergoes a double bond isomerization reaction to obtain the double bond isomerization product stream; The hydrogenation product stream and the double bond isomerization reaction product stream are selected and returned to step S1 for the distillation separation.

[0011] A second aspect of the present invention provides a system for producing 1-butene from mixed C4 streams. The system includes: a distillation unit, a light-weight removal unit, a selective hydrogenation unit, and a double bond isomerization unit. The distillation unit is provided with a mixed C4 stream inlet, a 1-butene-rich stream outlet, a butadiene-containing stream outlet, a heavy C4 stream outlet, a selective hydrogenation product inlet, and a double bond isomerization reaction product inlet. The light-weight removal unit is provided with a 1-butene-rich stream inlet and a 1-butene product outlet, which are connected. The selective hydrogenation unit is provided with a butadiene-containing stream inlet and a selective hydrogenation product outlet, which are connected. The double bond isomerization unit is provided with a heavy C4 stream inlet and a double bond isomerization reaction product outlet, with at least one indirect pipeline connected to the heavy C4 stream inlet. The selective hydrogenation product outlet is cyclically connected to the selective hydrogenation product inlet, and the double bond isomerization reaction product outlet is cyclically connected to the double bond isomerization reaction product inlet.

[0012] Through the above technical solution, the method for producing 1-butene from mixed C4 atoms provided by this invention can separate light and heavy C4 atoms to obtain qualified 1-butene products, achieving efficient recovery of 1-butene and efficient utilization of 2-butene; the side-stream hydrogenation process effectively controls the butadiene content, ensuring product quality; the double bond isomerization reaction product stream is returned to the distillation unit for separation, simplifying the process flow, reducing investment, and lowering system energy consumption. Attached Figure Description

[0013] Figure 1 This is a flowchart of the method for preparing 1-butene in Comparative Example 1; Figure 2 This is a flowchart of the method for preparing 1-butene in Comparative Example 2; Figure 3 This is a flowchart of the method for preparing 1-butene in Comparative Example 3; Figure 4This is a flowchart of a preferred embodiment of the method for preparing 1-butene according to the present invention; Figure 5 This is a flowchart of a preferred embodiment of the present invention for preparing 1-butene.

[0014] Explanation of reference numerals in the attached figures Detailed Implementation

[0015] 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.

[0016] The first aspect of the present invention provides a method for producing 1-butene by mixing C4 molecules, the method comprising: S1 mixed C4 stream was separated by distillation to obtain 1-butene-rich stream, butadiene-containing stream and heavy C4 stream; S2 1-Butene-rich stream is degraded by removing light components to obtain 1-butene product stream; S3 butadiene-containing stream is selectively hydrogenated to obtain selectively hydrogenated product stream; S4 at least part of the heavy C4 stream undergoes a double bond isomerization reaction to obtain the double bond isomerization product stream; The hydrogenation product stream and the double bond isomerization reaction product stream are selected and returned to step S1 for the distillation separation.

[0017] Existing processes typically involve first feeding the double bond isomerization reaction product stream into an enrichment column, and then returning the enriched 1-butene-rich material to the 1-butene distillation process. This not only makes the process more lengthy and increases investment in the enrichment column, but also results in higher overall energy consumption for the same 1-butene production capacity due to separation losses in the enrichment column itself. In this invention, the butadiene-containing stream is separated and selectively hydrogenated to effectively control the butadiene content. Selective hydrogenation inevitably leads to the formation of some n-butane, which can be separated as C4 heavy hydrocarbons, avoiding the impact of hydrogenation-generated n-butane on the 1-butene product quality and ensuring product quality. Furthermore, returning the double bond isomerization reaction product stream to step S1 for distillation simplifies the process. Specifically, the process of this invention is short and requires low investment; generally, only two process columns and 3-4 actual distillation columns are needed to obtain polymer-grade 1-butene. Therefore, the method of this invention further reduces energy consumption while ensuring product quality.

[0018] Those skilled in the art will know that distillation separation is generally carried out in a distillation column. According to a preferred embodiment of the present invention, along the vertical direction of the distillation column where the distillation separation takes place: the butadiene-containing stream is collected above the return location of the selected hydrogenation product stream. Using the aforementioned embodiment, better overall results can be achieved, especially ensuring that the butadiene content in the system is controlled, thereby ensuring that the butadiene index of the product 1-butene meets the requirements.

[0019] According to a preferred embodiment of the present invention, the return position of the selected hydrogenation product stream is located above the feed position of the mixed C4 stream. By employing the aforementioned embodiment, better overall results can be achieved, especially ensuring that the butadiene content in the system is controlled, thereby ensuring that the butadiene index of the product 1-butene meets the requirements.

[0020] According to a preferred embodiment of the present invention, the difference in theoretical plate number between the butadiene-containing stream extraction location and the selected hydrogenation product stream return location is 1-5, for example, 1, 2, 3, 4, or 5. By employing the aforementioned embodiment, product quality can be further guaranteed and energy consumption reduced.

[0021] According to a preferred embodiment of the present invention, the difference in theoretical plate number between the return position of the selected hydrogenation product stream and the feed position of the mixed C4 stream is 15-25, for example, 15, 18, 20, 23, or 25. By employing the aforementioned embodiment, product quality can be further guaranteed and energy consumption reduced.

[0022] According to the present invention, as long as the purpose of the present invention can be achieved, the position of the double bond isomerization reaction product stream returning to the distillation column is not particularly limited. Preferably, it is along the vertical direction of the distillation column where the distillation separation is carried out: the return position of the double bond isomerization reaction product stream is located below the feed position of the mixed C4 stream. More preferably, the difference between the theoretical number of plates of the return position of the double bond isomerization reaction product stream and the feed position of the mixed C4 stream is 5-25, for example, 5, 8, 10, 12, 15, 18, 20, 23 or 25.

[0023] According to a preferred embodiment of the present invention, the butadiene-containing stream is collected at a position of 3 / 8 to 1 / 2 of the total theoretical plates in the distillation column where the distillation separation is performed. In this invention, a stream of butadiene-containing material is collected from the side stream of the distillation column for selective hydrogenation. The selectively hydrogenated product is then returned to the distillation column for further distillation separation, which can further ensure product quality and reduce energy consumption.

[0024] According to the present invention, as long as the purpose of the present invention can be achieved, there is no special limitation on the number of theoretical plates of the distillation column for distillation separation. It can be selected according to the composition of the initial mixed C4 stream. In one embodiment, the number of theoretical plates of the distillation column for distillation separation is 120-200.

[0025] According to a preferred embodiment of the present invention, the 1-butene-rich stream is drawn from the top of a distillation column where distillation separation is performed.

[0026] According to a preferred embodiment of the present invention, the heavy C4 stream is collected from the bottom of a distillation column where distillation separation is performed.

[0027] According to a preferred embodiment of the present invention, the butadiene content in the butadiene-containing stream is 50 ppm.

[0028] According to a preferred embodiment of the present invention, the mass flow rate of the butadiene-containing stream is 2 to 6 times that of the mass flow rate of the 1-butene-rich stream, for example, 2 times, 3 times, 4 times, 5 times or 6 times.

[0029] According to the present invention, as long as the purpose of the present invention can be achieved, the conditions for distillation separation are not particularly limited and can be selected according to the composition of the mixed C4 stream. During distillation separation: the preferred operating pressure is 0.4-0.6 MPaG; the preferred theoretical plate number is 120-200; the preferred top temperature is 40-65°C; and the preferred reflux ratio is 15-35.

[0030] According to the present invention, the 1-butene-rich stream may contain other components lower than 1-butene, such as isobutane. The present invention employs any method in the art to remove isobutane and lighter components. In one embodiment, the method for removing light components includes: performing light component separation in a light component removal tower.

[0031] According to the present invention, the conditions for separation of light components are not selected based on the content of light components in the 1-butene-rich stream. For 1-butene-rich streams with a low content of light components, separation conditions with a lower theoretical plate number can be selected; for 1-butene-rich streams with a high content of light components, separation conditions with a lower theoretical plate number can be selected. In a preferred embodiment, during distillation separation: the preferred operating pressure is 0.4-0.6 MPaG; the preferred theoretical plate number is 40-160; the preferred top temperature is 30-50°C; and the preferred reflux ratio is 15-25.

[0032] According to the present invention, selective hydrogenation mainly involves the selective hydrogenation of polyolefins into monoolefins. Preferably, the selective hydrogenation is carried out in the presence of a selective hydrogenation catalyst, wherein the selective hydrogenation catalyst can be any selective hydrogenation catalyst in the art that can selectively hydrogenate polyolefins into monoolefins, generally a noble metal catalyst. In this invention, a palladium catalyst is used as an example to illustrate the advantages of the present invention, but the present invention is not limited thereto.

[0033] According to the present invention, specific selective hydrogenation conditions can be selected according to actual needs. Preferably, the selective hydrogenation conditions include: a reaction temperature of 35-55°C; a reaction pressure of 1.5-2.2 MPaG; a hydrogen to diene molar ratio of 5-20; and a reaction weight hourly space velocity of 6-10 hr. -1 .

[0034] According to the present invention, the operating temperature of general distillation separation is below 80°C, and the hydrogenation reaction is carried out in the temperature range of 35-55°C. The butadiene-containing stream introduced in the present invention is a liquid-phase reaction, and there is no phase change of the material. Therefore, the energy consumption of the hydrogenation unit is very low.

[0035] According to a preferred embodiment of the present invention, based on the total mass flow rate of the C4 stream, the proportion of the C4 stream undergoing the double bond isomerization reaction is no more than 85%, preferably 70-85 wt%, liru. The C4 stream mainly contains n-butane, trans-2-butene, and cis-2-butene, etc. In this invention, 2-butene in the C4 stream is selectively converted to 1-butene, and the isomerization reaction product is returned to the distillation separation step, which can better ensure product quality and reduce energy consumption.

[0036] According to the present invention, the purpose of the double bond isomerization reaction is to convert 2-butene in C4 heavy carbon with high selectivity to 1-butene. The double bond isomerization reaction is carried out in the presence of an isomerization catalyst, which can be a conventional catalyst in the art capable of converting 2-butene with high selectivity to 1-butene. Generally, it is a solid acid catalyst commonly used in the art. In this invention, the same solid acid catalyst is used as an example to illustrate the advantages of the present invention, but the present invention is not limited thereto.

[0037] According to the present invention, the conditions for the double bond isomerization reaction can be selected to favor the highly selective conversion of 2-butene to 1-butene, preferably a reaction temperature of 280-360°C; a reaction pressure of 0.45-0.9 MPaG; and a reaction weight hourly space velocity of 2-6 hr. -1 .

[0038] According to the present invention, the mixed C4 stream refers to individual streams mainly composed of various isomers of C4, and preferably, the source of the mixed C4 stream includes post-etherified C4 feedstock.

[0039] The method of this invention is particularly suitable for processing post-etherification C4 feedstock. The isobutylene content of post-etherification C4 feedstock is very low, therefore, no specific pretreatment is required to ensure the isobutylene content of the 1-butene product meets the standards. According to my country's petrochemical industry standard SH / T 1546-2009, the content of (isobutylene + 2-butene) in the superior grade is ≤0.4wt%, and the content of (isobutylene + 2-butene) in the first grade is ≤0.6wt%. To address the high 1-butene content in post-etherification C4 feedstocks (especially MTO post-etherification C4), the method described in this invention first separates the light and heavy C4 components. Specifically, the light C4, containing isobutane, isobutene, and 1-butene, is separated from the top of the butene distillation column, while the bottom of the column contains the heavy C4, containing n-butane, trans-2-butene, and cis-2-butene. Then, the light C4 undergoes a light-removal treatment to remove isobutane and lighter components, thereby obtaining a qualified 1-butene product. Furthermore, the post-etherification C4 has a high 2-butene content. By incorporating double bond isomers to convert 2-butene into 1-butene, the yield and production of 1-butene can be effectively improved, promoting the high-value-added utilization of 2-butene in post-etherification C4.

[0040] According to a preferred embodiment of the present invention, the mixed C4 stream contains: isobutene 0-0.2wt%, 1-butene 10-35wt%, 2-butene 25-65wt%, butadiene 0-0.02wt%, isobutane 0-41%, and n-butane 1-15wt%.

[0041] A second aspect of the present invention provides a system for producing 1-butene from mixed C4 streams. The system includes: a distillation unit, a light-weight removal unit, a selective hydrogenation unit, and a double-bond isomerization unit. The light-weight removal unit is provided with a mixed C4 stream inlet, a 1-butene-rich stream outlet, a butadiene-containing stream outlet, a heavy C4 stream outlet, a selective hydrogenation product inlet, and a double-bond isomerization reaction product inlet. The light-weight removal unit has a 1-butene-rich stream inlet and a 1-butene product outlet, which are connected. The selective hydrogenation unit has a butadiene-containing stream inlet and a selective hydrogenation product outlet, which are connected. The double-bond isomerization unit has a heavy C4 stream inlet and a double-bond isomerization reaction product outlet, with at least one indirect pipeline connected to the heavy C4 stream inlet. The selective hydrogenation product outlet is cyclically connected to the selective hydrogenation product inlet, and the double-bond isomerization reaction product outlet is cyclically connected to the double-bond isomerization reaction product inlet.

[0042] The system provided by this invention has the advantages of low investment, simplified process flow and reduced system energy consumption. The system of this invention generally only requires two process towers and 3-4 actual distillation towers to obtain polymer-grade 1-butene. That is, the system of this invention can achieve efficient recovery of 1-butene and efficient utilization of 2-butene while further reducing energy consumption.

[0043] According to the present invention, specifically, when using the system of the present invention to produce 1-butene from mixed C4 streams, the mixed C4 stream enters the distillation unit from the mixed C4 stream inlet for distillation separation to obtain a 1-butene-rich stream, a butadiene-containing stream, and a heavy C4 stream; the 1-butene-rich stream is drawn out from the 1-butene-rich stream outlet and then enters the light-weight removal unit from the 1-butene-rich stream inlet for light-weight removal treatment, and then the 1-butene product stream is drawn out from the 1-butene product stream outlet; the butadiene-containing stream enters the selective hydrogenation unit from the butadiene-containing stream outlet for selective hydrogenation to obtain selective... The hydrogenation product stream, after exiting the selected hydrogenation product stream outlet, enters the rectification unit through the selected hydrogenation product stream inlet for further rectification separation; a portion of the heavy C4 stream enters the double bond isomerization unit through at least one indirect pipeline between the heavy C4 stream outlet and the heavy C4 stream inlet to undergo a double bond isomerization reaction, yielding a double bond isomerization reaction product stream. After exiting the double bond isomerization reaction product stream outlet, the double bond isomerization reaction product stream enters the rectification unit through the double bond isomerization reaction product stream inlet for further rectification separation.

[0044] According to a preferred embodiment of the present invention, the distillation unit includes a distillation column.

[0045] The distillation column in this invention can be a conventional distillation column in the art, and its structure is not particularly limited. In specific processes, although theoretically it may be a single process column due to the large number of total trays, it may need to be split into two columns in actual production: a distillation column (upper column) and a distillation column (lower column). The upper column is equipped with a top condenser, a reflux tank, and a reflux pump at its top. The bottom of the upper column is equipped with an intermediate bottom pump to feed the material from the bottom of the upper column into the top of the lower column. Simultaneously, the vapor phase from the lower column enters the bottom of the upper column through a pipeline from the top of the lower column. The lower column is equipped with a reboiler and an intermediate bottom pump. This configuration is within the scope of known technology in the art. Similarly, other separation devices with a large number of total trays also need to be configured as upper and lower columns during engineering implementation.

[0046] According to a preferred embodiment of the present invention, along the vertical direction of the distillation column: the selective hydrogenation product inlet is located between the butadiene-containing stream outlet and the mixed C4 stream inlet. The aforementioned system for producing 1-butene from mixed C4 streams achieves better overall results, especially ensuring that the butadiene content in the system is controlled, thereby guaranteeing that the butadiene content of the 1-butene product meets the required standards.

[0047] According to a preferred embodiment of the present invention, along the vertical direction of the distillation column, the inlet of the double bond isomerization reaction product is located below the inlet of the mixed C4 stream. In the aforementioned system, the production of 1-butene from mixed C4 streams selectively converts 2-butene in the heavy C4 stream to 1-butene, further ensuring product quality and reducing energy consumption.

[0048] According to a preferred embodiment of the present invention, along the vertical direction of the distillation column, the butadiene-containing stream outlet is located at 3 / 8 to 1 / 2 of the theoretical plate number of the distillation column. In the system of the present invention, the distillation column has a side stream capable of selectively hydrogenating a butadiene-containing stream. The selectively hydrogenated product is then returned to the distillation column for further distillation separation, which further ensures product quality and reduces energy consumption.

[0049] According to a preferred embodiment of the present invention, based on the theoretical plate number of the distillation column, the height difference between the butadiene-containing stream outlet and the selective hydrogenation product inlet is 1-5. Performing the mixed C4 production of 1-butene in the aforementioned system further ensures product quality and reduces energy consumption.

[0050] According to a preferred embodiment of the present invention, based on the theoretical plate number of the distillation column, the height difference between the selected hydrogenation product inlet and the mixed C4 stream inlet is 15-25 mm. Performing the mixed C4 production of 1-butene in the aforementioned system further ensures product quality and reduces energy consumption.

[0051] According to a preferred embodiment of the present invention, based on the theoretical number of plates of the distillation column, the height difference between the inlet of the double bond isomerization reaction product and the inlet of the mixed C4 stream is 5-25.

[0052] The production of 1-butene by mixing C4 molecules in the aforementioned system can further ensure product quality and reduce energy consumption.

[0053] The light-light removal unit in this invention can be a conventional light-light removal tower in the art. Similar to the aforementioned distillation tower, in actual production, the light-light removal tower can also be divided into an upper tower and a lower tower. This configuration is well known in the art and will not be elaborated further here.

[0054] The selective hydrogenation unit in this invention can be a selective hydrogenation reactor in the art.

[0055] The double bond isomerization unit in this invention can be a conventional double bond isomerization reactor in the art.

[0056] According to a preferred embodiment of the present invention, a method for producing 1-butene by mixing C4 molecules is provided, wherein the method is in Figure 4 The process is carried out as shown. When describing this method, the present invention does not specifically describe the inlet or outlet of the stream. Those skilled in the art will understand that the corresponding stream flows in from the inlet or outlet of the corresponding device. The mixed C4 stream 1 enters the butene distillation column (lower column) F2 for distillation separation. At the top of the butene distillation column (upper column) F1, a 1-butene-rich stream 9 is obtained. The 1-butene-rich stream 9 is sent to the light component removal column E1 to remove the light component 2. Poly-1-butene product is obtained from the bottom of the light component removal column E1. Stream 3; The butadiene-containing stream is taken from the side stream of the butene distillation column (upper column) F1 and sent to the selective hydrogenation reactor for selective hydrogenation to obtain the selective hydrogenation product stream; The selective hydrogenation product stream is returned to the butene distillation column (upper column) F1; The heavy C4 stream 4 (bottom liquid) of the butene distillation column (lower column) F2 is divided into two streams, one of which is sent to the double bond isomerization reactor R1 for double bond isomerization reaction to obtain the double bond isomerization reaction product stream; The other stream is discharged from the system as an external discharge C4 6; The double bond isomerization reaction product stream enters the butene distillation column (lower column) F2.

[0057] According to a preferred embodiment of the present invention, a method for producing 1-butene by mixing C4 molecules is provided, wherein the method is in Figure 5 As shown, the method is carried out in this way. In describing this method, the present invention does not specifically describe the inlet or outlet of the stream. Those skilled in the art will understand that the corresponding stream flows in from the inlet or outlet of the corresponding device. The mixed C4 stream 1 enters the butene distillation column (lower column) F2 for distillation separation. At the top of the butene distillation column (upper column) F1, a 1-butene-rich stream 9 is obtained. After the light component 2 is removed in the light component removal columns (upper column) E11 and E12, the 1-butene-rich stream 9 exits from the light component removal column (lower column) E12. The bottom of the column yields 1-butene product stream 3; a butadiene-containing stream is collected from the side stream of butene distillation column (upper column) F1 and sent to the selective hydrogenation reactor for selective hydrogenation to obtain a selective hydrogenation product stream; the selective hydrogenation product stream is returned to butene distillation column (upper column) F1; the heavy C4 stream 4 (bottom liquid) of butene distillation column (lower column) F2 is divided into two streams, one of which is sent to the double bond isomerization reactor R1 for double bond isomerization reaction to obtain a double bond isomerization reaction product stream; the other stream is discharged from the system as an external C4 6; the double bond isomerization reaction product stream enters butene distillation column (lower column) F2.

[0058] The present invention will be described in detail below through embodiments. The following embodiments include: Example 1 like Figure 4As shown, mixed C4 stream 1, with a flow rate of 10 tons / hour, enters the butene distillation column (lower column) F2 from the 85th tray (the theoretical tray number of the process column, numbered from top to bottom; the theoretical tray number of butene distillation column (upper column) F1 is 1-70, and the theoretical tray number of butene distillation column (lower column) F2 is 71-140; the same below) for distillation separation. 1-Butene-rich stream 9 (1-butene concentration of 98.9 wt%) is obtained at the top of the butene distillation column (upper column) F1, with a flow rate of 5.1 tons / hour. 1-Butene-rich stream 9 is fed from tray 30 into light component removal column E1 for light component removal 2. 1-Butene product stream 3 is obtained from the bottom of light component removal column E1. A butadiene-containing stream, at a flow rate of approximately 15 tons / hour, is collected from the side stream of tray 66 of butene distillation column (upper column) F1 and fed into selective hydrogenation reactor R3 for selective hydrogenation to obtain a selectively hydrogenated product stream. The selective hydrogenation conditions are: reaction temperature 40°C, reaction pressure 2 MPaG, hydrogen / diene molar ratio 10, and reaction space velocity 9 hr. -1 The hydrogenation catalyst was selected as a palladium-based noble metal catalyst. The hydrogenation product stream was returned to the butene distillation column (upper column) F1 from the 67th tray. The butadiene content of the materials before and after hydrogenation was selected to be 76 ppm and 6 ppm, respectively. The heavy C4 stream (bottom liquid) from the butene distillation column (lower column) F2 was split into two streams. One stream, with a flow rate of approximately 16 tons / hour, was fed into the double bond isomerization reactor R1 to obtain the double bond isomerization product stream. The conditions for the double bond isomerization reaction were: reaction temperature 320℃, reaction pressure 0.55 MPaG, and reaction space velocity 5hr. -1 The isomerization reaction catalyst is a solid acid molecular sieve catalyst; another stream serves as the external discharge system for C4-6, with a flow rate of approximately 4.9 tons / hour; the double bond isomerization reaction product stream enters the butene distillation column (lower column) F2 from the 92nd tray.

[0059] The conditions for light component removal and distillation separation are shown in the table below:

[0060] As can be seen from the above, the total heat load of the butene distillation column and the light component removal column is 14.2MW.

[0061] The main logistics information is shown in the table below:

[0062] Example 2 like Figure 5As shown, mixed C4 stream 1, with a flow rate of 10 tons / hour, enters butene distillation column (lower column) F2 from the 80th tray (the theoretical tray number of the process column, numbered from top to bottom; theoretical tray number 1-70 for butene distillation column (upper column) F1, and theoretical tray number 71-140 for butene distillation column (lower column) F2; the same applies below) for distillation separation. At the top of butene distillation column (upper column) F1, a 1-butene-rich stream 9 (with a 1-butene concentration of 41.6 wt% and an isobutane concentration of 58.0 wt%) is obtained, with a flow rate of 6.9 tons / hour; 1-butene-rich stream 9... 1-Butene product stream 9 is obtained from the 65-plate light component removal column (upper column) E11. After removing light component 2 in both the upper and lower light component removal columns E11 and E12, 1-butene product stream 3 is obtained from the bottom of the lower light component removal column E12. A butadiene-containing stream is collected from the side stream of the 56th plate of the butene distillation column (upper column) F1 at a flow rate of approximately 15 tons / hour and fed into the selective hydrogenation reactor R3 for selective hydrogenation to obtain the selectively hydrogenated product stream. The selective hydrogenation conditions are: reaction temperature 52°C, reaction pressure 1.6 MPaG, hydrogen / diene molar ratio 15, and reaction space velocity 6 h⁻¹. -1 The hydrogenation catalyst was selected as a palladium-based noble metal catalyst. The hydrogenation product stream was returned from the 57th tray to the butene distillation column (upper column) F1. The butadiene content of the materials before and after hydrogenation was selected to be 128 ppm and 10 ppm, respectively. The heavy C4 stream (bottom liquid) from the butene distillation column (lower column) F2 was split into two streams. One stream, with a flow rate of approximately 16 tons / hour, was fed into the double bond isomerization reactor R1 to obtain the double bond isomerization product stream. The conditions for the double bond isomerization reaction were: reaction temperature 300℃, reaction pressure 0.6 MPaG, and reaction space velocity 5hr. -1 The isomerization reaction catalyst is a solid acid catalyst; another stream serves as the external discharge system for C4-6, with a flow rate of approximately 3.1 tons / hour; the double bond isomerization reaction product flows from the 100th tray into the butene distillation column (lower column) F2.

[0063] The conditions for light fraction removal and distillation separation are shown in the table below:

[0064] As shown above, the total heat load of the butene distillation column and the light component removal column is 19.1 MW.

[0065] The main logistics information is shown in the table below.

[0066]

[0067] Example 3 The method differs from that in Example 1 in that: A butadiene-containing stream was collected from the side stream of tray 83 of the butene distillation column (upper column) F1; the hydrogenated product stream was selected to be returned to the butene distillation column (upper column) F1 from tray 87, and the final 1-butene product stream contained 85 ppm of butadiene.

[0068] Example 4 The method differs from that in Example 1 in that: A butadiene-containing stream was collected from the side stream of the 70th tray of the butene distillation column (upper column) F1; the hydrogenated product stream was selected to be returned to the butene distillation column (upper column) F1 from the 80th tray, and the final butadiene content in the 1-butene product stream was 52 ppm.

[0069] Example 5 The method differs from that in Example 1: the product stream of the double bond isomerization reaction enters the butene distillation column (lower column) from the 80th tray, and the final 1-butene product stream contains 62 ppm of butadiene.

[0070] Comparative Example 1 like Figure 1 As shown, the mixed C4 stream 1 (same as in Example 1) is fed from the 69th tray into the first distillation column (upper column) A1. Light components 2 are removed in the first distillation column (upper column) A1 and the first distillation column (lower column) A2. Then, it is fed from the 87th tray into the second distillation column (lower column) B2. Second distillation separation is carried out in the second distillation column (upper column) B1 and the second distillation column (lower column) B2 to obtain 1-butene product stream 3 at the top of the column, which is about 2.9 tons / hour. The bottom liquid of the second distillation column (lower column) B2 is discharged as C4 6, and the discharge C4 flow rate is about 7 tons / hour.

[0071] The operating parameters for the light component removal process and the second distillation separation are shown in the table below:

[0072] As shown above, the total heat load of the first and second distillation columns is 9.2 MW. The main logistics information is shown in the table below:

[0073] As shown in the table above, this comparative example separates 1-butene from the raw materials through refining, but the production capacity is small. However, the butadiene content in the final product is too high, and the product cannot meet the industry's first-grade standard.

[0074] Comparative Example 2 like Figure 2As shown, the mixed C4 stream 1 (same as in Example 1) at a flow rate of 10 tons / hour is mixed with the selective hydrogenation product stream, totaling 14.6 tons / hour. This mixture is fed into the first distillation column (upper column) A1 on the 69th tray. Light components are removed in both the first distillation column (upper column) A1 and the first distillation column (lower column) A2. Then, it is fed into the second distillation column (lower column) B2 from the 87th tray. The mixture is then processed in both the second distillation column (upper column) B1 and the second distillation column (lower column) B2. Distillation separation was performed, yielding approximately 5 tons / hour of 1-butene product stream 3 from the top of the second distillation column (upper column) B1. Heavy C4 stream 4 (bottom liquid) from the second distillation column (lower column) B2 was mixed with recycled material 5, totaling 20.2 tons / hour, and fed into the double bond isomerization reactor R1 to obtain the double bond isomerization product stream. The conditions for the double bond isomerization reaction were: reaction temperature 320℃, reaction pressure 0.55 MPaG, and reaction space velocity 5 h⁻¹. -1 The isomerization reaction catalyst is a solid acid catalyst. The product stream from the double bond isomerization reaction is fed into the concentration column C1 from the 18th tray. At the top of the concentration column C1, 1-butene-rich isomeric C4 11 is obtained. The bottom material of the concentration column C1 is divided into two parts: one part is returned to the inlet of the double bond isomerization reactor R1 as recycled material 5, with a flow rate of 11 tons / hour; the other part is discharged as effluent C4 6, with a flow rate of approximately 4.7 tons / hour. The 1-butene-rich isomeric C4 11 collected from the top of the concentration column C1 contains approximately 94 ppm butadiene. If left untreated, this would lead to excessive butadiene content in the 1-butene product. Therefore, the isomeric C4 11 is fed into the selective hydrogenation reactor R3 for selective hydrogenation to obtain a selectively hydrogenated product stream. The selective hydrogenation reaction conditions are: reaction temperature 40℃, reaction pressure 2.0 MPaG, hydrogen / diene molar ratio 10, and reaction space velocity 9 h⁻¹. -1 The hydrogenation catalyst was selected as a palladium-based noble metal catalyst. After selective hydrogenation, the butadiene content was reduced to 8 ppm. Then, the selected hydrogenation product stream and the mixed C4 stream 1 were mixed and sent to the first distillation column (upper column) A1.

[0075] The operating parameters for each tower are shown in the table below:

[0076] As can be seen from the above, the total heat load of the three towers is 19.7MW.

[0077] The main logistics information is shown in the table below:

[0078] Comparative Example 3 like Figure 3As shown, mixed C4 stream 1 (same as in Example 1), with a flow rate of 10 tons / hour, is fed into hydroisomerization reactor R2. Under reaction conditions of 65°C, 1.5 MPaG, nickel-based catalyst, and space velocity 5, the 1-butene conversion rate is 75%. The reaction product in hydroisomerization reactor R2 is fed from the 30th tray into pretreatment column (upper column) D1. Isobutene is removed in pretreatment column (upper column) D1 and pretreatment column (lower column) 2. The 2-butene recovery rate in the pretreatment column is 96%. The heavy C4 stream 4 (bottom liquid, a stream rich in 2-butene) obtained from pretreatment column (lower column) 2 is mixed with recycled material 5 at a flow rate of approximately 8.9 tons / hour, totaling 38.9 tons / hour, and fed into double bond isomerization reactor R1. Under reaction conditions of 320°C, 0.55 MPaG, and space velocity 5hr, the reaction product is fed into pretreatment column (upper column) D1. -1 The double bond isomerization reaction is carried out under reaction conditions using a solid acid catalyst. The double bond isomerization product is fed into a selective hydrogenation reactor R3 for selective hydrogenation to obtain a selectively hydrogenated product stream. The selective hydrogenation conditions are: temperature 45℃, pressure 2.0 MPaG, and space velocity 8hr. -1 The butadiene content is reduced from 35 ppm to 13 ppm. Then, it is fed from the 14th tray into the light component removal tower E1 to remove light components 2, such as propylene and excess hydrogen, which are byproducts of isomerization (and mixed with the light components collected from the top of the pre-separation tower before exiting the unit boundary). The bottom material is fed from the 65th tray into the butene distillation tower (upper tower) F1, and 1-butene product stream 3 is obtained from the top of the tower. Part of the bottom material of the butene distillation tower (lower tower) is returned to the inlet of the double bond isomerization reactor R1 as recycled material 5. The flow rate of recycled material 5 is 30 tons / hour. The remaining part is discharged as C4 6, with a flow rate of about 4.7 tons / hour.

[0079] The operating parameters for each tower are shown in the table below:

[0080] As can be seen from the above, the total heat load of the three towers is 26.6MW.

[0081] The main logistics information is shown in the table below:

[0082] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing 1-butene from mixed C4 molecules, characterized in that, The method includes: S1 mixed C4 stream was separated by distillation to obtain 1-butene-rich stream, butadiene-containing stream and heavy C4 stream; S2 1-Butene-rich stream is degraded by removing light components to obtain 1-butene product stream; S3 butadiene-containing stream is selectively hydrogenated to obtain selectively hydrogenated product stream; S4 at least part of the heavy C4 stream undergoes a double bond isomerization reaction to obtain the double bond isomerization product stream; In this process, the hydrogenation product stream and the double bond isomerization reaction product stream are selected and returned to step S1 for the distillation separation.

2. The method according to claim 1, wherein, Along the vertical direction of the distillation column where the distillation separation takes place: The butadiene-containing stream is collected above the selected return location of the hydrogenation product stream; and / or The return location of the selected hydrogenation product stream is located above the feed location of the mixed C4 stream; Preferably, The difference in theoretical plate number between the butadiene-containing stream extraction location and the selected hydrogenation product stream return location is 1-5; and / or The theoretical plate number difference between the return location of the selected hydrogenation product stream and the feed location of the mixed C4 stream is 15-25.

3. The method according to claim 1 or 2, wherein, Along the vertical direction of the distillation column where the distillation separation takes place: the return position of the double bond isomerization reaction product stream is located below the feed position of the mixed C4 stream; preferably, the difference in theoretical plate number between the return position of the double bond isomerization reaction product stream and the feed position of the mixed C4 stream is 5-25; and / or The butadiene-containing stream is collected at a position between 3 / 8 and 1 / 2 of the total theoretical plates in the distillation column where the distillation separation is performed; and / or The theoretical number of plates in a distillation column used for rectification is 120-200. and / or The 1-butene-rich stream is collected from the top of a distillation column where the distillation separation is performed; and / or The heavy C4 stream is collected from the bottom of the distillation column where it is separated by distillation.

4. The method according to any one of claims 1-3, wherein, The butadiene-containing stream contains 50-150 ppm of butadiene; and / or The mass flow rate of the butadiene-containing stream is 2-6 times that of the 1-butene-rich stream; and / or The conditions for the distillation separation include: an operating pressure of 0.4-0.6 MPaG; and / or a theoretical plate number of 120-200; and / or a top temperature of 40-65°C; and / or a reflux ratio of 15-35.

5. The method according to any one of claims 1-4, wherein, The method for removing light components includes: performing light component separation in a light component removal tower; Preferably, the conditions for light component separation include: operating pressure of 0.4-0.6 MPaG; and / or theoretical plate number of 40-160; and / or top temperature of 30-50°C; and / or reflux ratio of 15-25.

6. The method according to any one of claims 1-5, wherein, The selective hydrogenation is carried out in the presence of a selective hydrogenation catalyst; and / or The conditions for selective hydrogenation include: a reaction temperature of 35-55℃; a reaction pressure of 1.5-2.2 MPaG; a hydrogen to diene molar ratio of 5-20; and a reaction weight hourly space velocity of 6-10 hr. -1 .

7. The method according to any one of claims 1-6, wherein, Based on the total mass flow rate of heavy C4 stream, the proportion of heavy C4 stream undergoing double bond isomerization reaction shall not exceed 85%; and / or The double bond isomerization reaction is carried out in the presence of an isomerization catalyst; and / or The conditions for the double bond isomerization reaction include: a reaction temperature of 280-360℃; and / or a reaction pressure of 0.45-0.9 MPaG; and / or the reaction weight hourly space velocity is 2-6 hr -1 .

8. The method according to any one of claims 1-7, wherein, The source of the mixed C4 stream includes post-etherified C4 feedstock; and / or The mixed C4 stream contains: 0-0.2 wt% isobutene, 10-35 wt% 1-butene, 25-65 wt% 2-butene, 0-0.02 wt% butadiene, 0-41% isobutane, and 1-15 wt% n-butane.

9. A system for producing 1-butene by mixing C4 compounds, characterized in that, The system includes: a distillation unit, a light-weight removal unit, a selective hydrogenation unit, and a double-bond isomerization unit; The distillation unit is equipped with a mixed C4 stream inlet, a 1-butene-rich stream outlet, a butadiene-containing stream outlet, a heavy C4 stream outlet, a selective hydrogenation product inlet, and a double bond isomerization reaction product inlet. The light-removal unit is provided with a 1-butene-rich stream inlet and a 1-butene product stream outlet, and the 1-butene-rich stream inlet and the 1-butene-rich stream outlet are connected. The selective hydrogenation unit is provided with a butadiene-containing stream inlet and a selective hydrogenation product stream outlet, and the butadiene-containing stream inlet and the butadiene-containing stream outlet are connected. The double bond isomerization unit is provided with a C4 stream inlet and a double bond isomerization reaction product stream outlet, and the C4 stream outlet is provided with at least one indirect pipeline connected to the C4 stream inlet. The selective hydrogenation product outlet is circulatedly connected to the selective hydrogenation product inlet, and the double bond isomerization reaction product outlet is circulatedly connected to the double bond isomerization reaction product inlet.

10. The system according to claim 9, wherein, The distillation unit includes a distillation column; Preferably, along the vertical direction of the distillation column: The butadiene-containing stream outlet is located above the selective hydrogenation product inlet; and / or The selected hydrogenation product inlet is located above the mixed C4 stream inlet; and / or The inlet for the double bond isomerization reaction product is located below the inlet for the mixed C4 stream; The butadiene-containing stream outlet is located at 3 / 8-1 / 2 of the theoretical plate number of the distillation column; More preferably, the theoretical number of plates of the distillation column is used as a reference: The height difference between the butadiene-containing stream outlet and the selective hydrogenation product inlet is 1-5; and / or The height difference between the selected hydrogenation product inlet and the mixed C4 stream inlet is 15-25; and / or The height difference between the inlet of the double bond isomerization reaction product and the inlet of the mixed C4 stream is 5-25.

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