Device and method for producing 1-butene using carbon four fraction

Abstract

The present invention relates to a device and method for producing 1-butene using a carbon four fraction, the device including a selective hydrogenation unit, an etherification unit and a precision distillation unit arranged in sequence along a material flow direction, and further including an extraction pre-fractionation unit, wherein the extraction fractionation unit is arranged between the selective hydrogenation unit and the etherification unit, or connected after the precision distillation unit, and the extraction fractionation unit is further connected to a 2-butene isomerization unit. Compared with the prior art, the energy consumption of the present invention can be reduced by more than 20%. At the same time, the total conversion rate of 2-butene is high, more than 85%, the total yield of 1-butene is greater than 90%, the raw material has a wide range of application, and is particularly suitable for n-butane-rich carbon four raw materials.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry and relates to a method and device for producing 1-butene by utilizing carbon four fraction. Background Art

[0002] Refinery C4, cracking C4, and coal-to-olefins C4 contain significant amounts of 1-butene and 2-butene. 1-Butene, due to its active chemical properties, is a very important chemical raw material, used in the production of linear low-density polyethylene resin, high-density polyethylene, polybutene resin, decanol, and other products. It has a wide range of applications and is highly valuable. However, compared to 1-butene, most 2-butene is used as fuel and has a relatively low value. If the process of isomerizing 2-butene to 1-butene is incorporated into the fractionation system separating 1-butene and 2-butene, converting 2-butene into the industrially valuable 1-butene before further separation, the comprehensive utilization value of C4 resources can be increased, significantly boosting the economic benefits of enterprises.

[0003] As early as 1992, the American Chemical Research and Chartering Company proposed a method for increasing 1-butene production through catalytic distillation. Using etherified C4 as feedstock, the material enters the catalytic bed of a catalytic distillation column, where butadiene is selectively hydrogenated while the double bond of 2-butene isomerizes to 1-butene. However, this method has a low conversion rate and is ineffective.

[0004] The French Petroleum Institute (IFP) has proposed a technology for producing 1-butene from 2-butene using catalytic hydroisomerization. This process uses a Pd / Al2O3 catalyst. A C4 feed containing a small amount of 1-butene is first distilled through a distillation column to separate the 1-butene. High-purity 1-butene is produced at the top of the column. The 2-butene-containing feed at the bottom of the column is mixed with hydrogen in a specific ratio and then fed into a backpack hydroisomerization reactor, where most of the 2-butene is converted to 1-butene. The product is then recycled into the distillation column. This process allows for long-term continuous operation. However, this method has the disadvantages of high distillation energy consumption and the presence of a large amount of n-butane in the 2-butene, which limits the conversion rate.

[0005] Sinopec Shanghai Research Institute of Petrochemical Engineering and Zhongyuan Petrochemical Company have jointly developed a technology for increasing 1-butene production through olefin isomerization. This technology utilizes a large axial-flow fixed-bed reactor and a independently developed solid aluminosilicate catalyst. A liquid C4 olefin mixture is heated to 300-350°C before entering the reactor. Here, 2-butene undergoes double bond isomerization to 1-butene under the action of a solid acid catalyst. The product enters a distillation column for separation, yielding a high-purity 1-butene product at the top of the column. The bottoms of the column are then recycled to the reactor for further reaction. The selectivity for 1-butene exceeds 95%, and the yield reaches 16-21%. However, this method still does not address the problem of high levels of n-butane in the 2-butene isomerization feed, resulting in high energy consumption and low yields. Summary of the Invention

[0006] The purpose of the present invention is to provide a device and method for producing 1-butene using a C4 fraction, so as to reduce the energy consumption of the device, improve the total conversion rate of 2-butene isomers and the yield of 1-butene products.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] On the one hand, the present invention provides a device for producing 1-butene using a C4 fraction, comprising a selective hydrogenation unit, an etherification unit and a precision distillation unit arranged in sequence along the direction of the material flow, and also comprising an extraction pre-fractionation unit, wherein the extraction pre-fractionation unit is arranged between the selective hydrogenation unit and the etherification unit, or is connected and arranged after the precision distillation unit, and the extraction pre-fractionation unit is also connected to a 2-butene isomerization unit.

[0009] Furthermore, when the extraction fractionation unit is arranged between the selective hydrogenation unit and the etherification unit, the reaction product outlet of the 2-butene isomerization unit is also returned to connect to the extraction pre-fractionation unit.

[0010] Furthermore, when the extraction pre-fractionation unit is arranged after the precision distillation unit, the reaction product outlet of the 2-butene isomerization unit is also returned to connect to the raw material inlet of the precision distillation unit.

[0011] On the other hand, the present invention also provides a method for producing 1-butene using a C4 fraction, which is implemented using the above-mentioned device and comprises the following steps:

[0012] (1) The C4 fraction is fed into a selective hydrogenation unit, where impurities including butadiene and butyne are removed through a selective hydrogenation reaction to obtain a selective hydrogenation product;

[0013] (2) feeding the selective hydrogenation product into an extractive fractionation unit for fractionation to obtain four streams of materials: a saturated light hydrocarbon fraction or an alkane-rich fraction, a 1-butene-rich fraction, a 2-butene-rich fraction, and a heavy C4 fraction, wherein the saturated light hydrocarbon fraction or the alkane-rich fraction and the heavy C4 fraction are discharged;

[0014] (3) sending the 1-butene-rich fraction to an etherification unit for etherification reaction to obtain MTBE and ether products, wherein the MTBE is sent out;

[0015] (4) sending the obtained ether product to a precision distillation unit to obtain polymerization-grade 1-butene and recycled C4, wherein the polymerization-grade 1-butene is output as a product and the recycled C4 is returned to the 2-butene isomerization unit;

[0016] (5) The 2-butene-rich fraction is sent to the 2-butene isomerization unit to isomerize 2-butene to 1-butene, and the 1-butene-rich isomerized product is returned to the extraction fractionation unit.

[0017] Furthermore, the C4 fraction is a by-product C4 fraction of an MTO unit, a C4 fraction after etherification in an oil refinery, or a C4 fraction after butadiene extraction in an ethylene plant.

[0018] Furthermore, the precision distillation unit has a distillation tower with a sufficient number of theoretical plates, and can precisely cut the ether product fed into the distillation tower into a high-purity 1-butene component.

[0019] Furthermore, the extractive pre-fractionation unit adopts extractive distillation and / or fractionation technology, and cuts the input selective hydrogenation product into four streams of materials: saturated light hydrocarbon or alkane-rich fraction, 1-butene-rich fraction, 2-butene-rich fraction, and heavy carbon four fraction.

[0020] Furthermore, the saturated light hydrocarbon fraction or the alkane-rich fraction includes a normal butane fraction and an isobutane fraction or a small amount of other light hydrocarbon components.

[0021] In another aspect, the present invention also provides another method for producing 1-butene using a C4 fraction, wherein the method is implemented using the above-mentioned apparatus, comprising the following steps:

[0022] (1) The C4 fraction is fed into a selective hydrogenation unit, where impurities including butadiene and butyne are removed through a selective hydrogenation reaction to obtain a selective hydrogenation product;

[0023] (2) sending the selective hydrogenation product to an etherification unit for etherification reaction to obtain MTBE and ether products, wherein MTBE is sent out;

[0024] (3) sending the ether product to a precision distillation unit to obtain saturated light hydrocarbons or rich alkanes, polymerization-grade 1-butene, and C4 in the bottom of the tower, wherein the saturated light hydrocarbons or rich alkanes are sent out and the polymerization-grade 1-butene is output as a product;

[0025] (4) feeding the C4 fraction in the bottom of the tower into an extraction pre-fractionation unit for fractionation to obtain three streams of materials: a saturated hydrocarbon fraction or an alkane-rich fraction, a 2-butene-rich fraction, and a heavy C4 fraction, wherein the saturated hydrocarbon fraction or the alkane-rich fraction and the heavy C4 fraction are discharged;

[0026] (5) The 2-butene-rich fraction is sent to the 2-butene isomerization unit to isomerize 2-butene to 1-butene, and the 1-butene-rich isomerized product is sent back to the precision distillation unit.

[0027] Furthermore, the saturated light hydrocarbon fraction or the alkane-rich fraction comprises a normal butane fraction and an isobutane fraction or a small amount of other light hydrocarbon components.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) The raw material has a wide range of applications, and is particularly suitable for raw materials rich in n-butane C4.

[0030] (2) Low overall energy consumption. After the extraction pre-fractionation unit, the n-butane-rich saturated light hydrocarbons are separated from the C4, which greatly reduces the circulation flow of the 2-butene isomerization unit. At the same time, the extraction pre-fractionation unit separates the 1-butene-rich material, and most of the 2-butene and n-butane have been removed from this 1-butene-rich material. The 1-butene-rich material is deetherified and subjected to the precision distillation unit, which reduces the precision distillation load. After the extraction pre-fractionation, the material entering the 2-butene isomerization reactor is rich in 2-butene, which can reduce the energy consumption of 2-butene isomerization, achieve a large circulation ratio, and obtain a high total isomerization conversion rate. Compared with the conventional C4 2-butene isomerization process for producing high-purity 1-butene, the energy consumption is reduced by more than 20%.

[0031] (3) The 1-butene product has high purity. The purity of the 1-butene product is ≥99.3wt%.

[0032] (4) The yield of 1-butene product is high, greater than 90%.

[0033] (5) High-purity 1-butene is produced while simultaneously co-producing high-purity tetraalkanes and MTBE.

[0034] (6) It can achieve a high total conversion rate of 2-butene isomerization, and the total conversion rate can reach more than 85%.

[0035] (7) Flexible operating conditions and great operational flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the process of Example 1 of the present invention;

[0037] Figure 2 Schematic diagram of the process flow of Example 2 of the present invention;

[0038] Figure 3 This is a schematic diagram of the process flow of Comparative Example 1;

[0039] Description of the marks in the figure:

[0040] 1 is a selective hydrogenation unit, 2 is an extractive pre-fractionation unit, 3 is an etherification unit, 4 is a 2-butene isomerization unit, and 5 is a precision distillation unit. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0042] In the following embodiments, unless otherwise specified, structural equipment is generally commercially available equipment or conventional structures in the art for realizing corresponding functions. Unless otherwise specified, processing techniques are generally conventional techniques in the art.

[0043] Example 1:

[0044] like Figure 1 As shown, the raw material C4 fraction first enters the selective hydrogenation unit 1, undergoes selective hydrogenation reaction, removes impurities such as butadiene and propyne, and then is mixed with 2-butene isomerized products, and then enters the extraction pre-fractionation unit 2 to be separated into saturated hydrocarbons, 1-butene-rich fraction, 2-butene-rich fraction and heavy C4; the saturated hydrocarbons (n-butane + isobutane) are sent to the downstream cracking olefin production unit, and the heavy C4 is sold as a product; the 1-butene-rich fraction enters the etherification unit 3, extracts isobutene through etherification reaction and generates MTBE, which is discharged from the device as a product; the etherified material enters the precision distillation unit 5, separates the 1-butene product through precision distillation and sends it to the device, and the remaining material is returned to the 2-butene isomerization unit 4 as recycled C4; the 2-butene-rich fraction enters the 2-butene isomerization unit 4, converts 2-butene into 1-butene through isomerization reaction, and the isomerized product is mixed with the selective hydrogenation product and enters the extraction fractionation unit together.

[0045] Example 2:

[0046] like Figure 2 As shown, the raw C4 fraction first enters the selective hydrogenation unit 1, where it undergoes a selective hydrogenation reaction and removes impurities such as butadiene and propyne. It then enters the etherification unit 3, where isobutylene is extracted and MTBE is produced through the etherification reaction. MTBE exits the unit as a product. The etherified material enters the precision distillation unit 5, where it is separated through precision distillation into saturated hydrocarbons (isobutane), 1-butene product, and the bottom C4. The saturated hydrocarbons (isobutane) are sent to downstream equipment, while the bottom C4 enters the extraction pre-fractionation unit 2, where it is separated into an n-butane fraction, a 2-butene-rich fraction, and heavy C4. The n-butane fraction is mixed with the saturated hydrocarbons separated by the precision distillation unit 5 and then sent to downstream equipment. The 2-butene-rich fraction enters the 2-butene isomerization unit 4, where 2-butene is converted to 1-butene through an isomerization reaction. The isomerized product is mixed with the etherified material and enters the precision distillation unit 5. The heavy C4 is sent as a product out of the unit.

[0047] Comparative Example 1:

[0048] like Figure 3As shown, the raw C4 fraction first enters the selective hydrogenation unit 1 to remove impurities such as butadiene and propyne, then enters the etherification unit 3, where the etherification reaction extracts isobutylene and produces MTBE, which exits the unit as a product. The etherified material enters the precision distillation unit 5, where it is separated through precision distillation into saturated hydrocarbons (isobutane), 1-butene product, and bottom C4. The saturated hydrocarbons (isobutane) are sent to downstream units, while a portion of the bottom C4 is sent out of the unit as the heavy C4 product. The remainder enters the 2-butene isomerization unit 4, where the 2-butene is converted to 1-butene through an isomerization reaction. The isomerized product is mixed with the etherified material and then enters the precision distillation unit 5.

[0049] In summary, the process flow of the present invention in Examples 1 and 2 utilizes an extractive pre-fractionation unit to separate and remove n-butane, thus preventing its accumulation in the 2-butene isomerization fraction. This not only saves energy but also eliminates the limitations of the 2-butene fraction's cyclic isomerization, thereby increasing the overall conversion rate of 2-butene isomerization. The increased 2-butene concentration in the 2-butene isomerization fraction increases the processing capacity of the isomerization unit, reducing equipment investment. Furthermore, the use of an extractive pre-fractionation unit for preliminary separation of the 1-butene and 2-butene fractions reduces the load on the precision distillation unit and significantly reduces separation energy consumption. Compared to conventional processes such as Comparative Example 1, the process flow of this application reduces energy consumption by over 20%. Furthermore, it simultaneously maintains a high overall 2-butene conversion rate exceeding 85% and a total 1-butene yield exceeding 90%.

[0050] And as Figure 3 As shown, the C4 production of 1-butene process in Comparative Example 1 has the following major disadvantages:

[0051] 1) High energy consumption. The precision distillation and 2-butene isomerization units contain a large amount of n-butane material circulation, resulting in large circulation volume and high energy consumption.

[0052] 2) High 2-butene isomerization but low overall conversion. Because the energy consumption of the precision distillation and 2-butene isomerization units increases significantly with increasing circulation volume, this limits the circulation ratio and the overall conversion of 2-butene isomerization.

[0053] 3) The yield of 1-butene product is low.

[0054] 4) The scope of application of raw materials is small, and it is not suitable for raw materials rich in n-butane C4.

[0055] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for producing 1-butene using a C4 fraction, characterized in that: The method is based on an apparatus comprising a selective hydrogenation unit, an etherification unit and a precision distillation unit sequentially arranged along the direction of the material flow, and further comprising an extraction pre-fractionation unit, wherein the extraction pre-fractionation unit is arranged between the selective hydrogenation unit and the etherification unit, and the extraction pre-fractionation unit is further connected to a 2-butene isomerization unit; The reaction product outlet of the 2-butene isomerization unit is also returned to connect to the extraction pre-fractionation unit; The method comprises the following steps: (1) The C4 fraction is fed into a selective hydrogenation unit, where impurities including butadiene and butyne are removed through a selective hydrogenation reaction to obtain a selective hydrogenation product; (2) The selective hydrogenation product is fed into an extractive pre-fractionation unit for fractionation to obtain four streams of materials: a saturated light hydrocarbon fraction or an alkane-rich fraction, a 1-butene-rich fraction, a 2-butene-rich fraction, and a heavy C4 fraction. The saturated light hydrocarbon fraction or the alkane-rich fraction and the heavy C4 fraction are fed out; (3) The 1-butene-rich fraction is fed into an etherification unit for etherification reaction to obtain MTBE and ether products, wherein the MTBE is discharged; (4) The obtained ether product is sent to a precision distillation unit to obtain polymerization-grade 1-butene and recycled C4, wherein the polymerization-grade 1-butene is output as a product and the recycled C4 is returned to the 2-butene isomerization unit; (5) The 2-butene-rich fraction is sent to the 2-butene isomerization unit to isomerize 2-butene to 1-butene, and the 1-butene-rich isomerized product is returned to the extraction fractionation unit.

2. The method for producing 1-butene by utilizing C4 fraction according to claim 1, characterized in that: The C4 fraction is a by-product C4 fraction of an MTO device, a C4 fraction after etherification in an oil refinery, or a C4 fraction after butadiene extraction in an ethylene plant.

3. The method for producing 1-butene by utilizing C4 fraction according to claim 1, characterized in that: The precise distillation unit is a distillation tower with a sufficient number of theoretical plates, and can precisely cut out the 1-butene component from the ether product fed in.

4. The method for producing 1-butene by utilizing C4 fraction according to claim 1, characterized in that: The saturated light hydrocarbon fraction or the alkane-rich fraction includes an n-butane fraction and an isobutane fraction.

5. A method for producing 1-butene using C4 fraction, characterized in that: The method is based on an apparatus comprising a selective hydrogenation unit, an etherification unit and a precision distillation unit sequentially arranged along the direction of the material flow, and further comprising an extraction pre-fractionation unit, wherein the extraction pre-fractionation unit is connected and arranged after the precision distillation unit, and the extraction pre-fractionation unit is further connected to a 2-butene isomerization unit; The reaction product outlet of the 2-butene isomerization unit is also returned to the raw material inlet connected to the precision distillation unit; The method comprises the following steps: (A) feeding the C4 fraction into a selective hydrogenation unit, removing impurities including butadiene and butyne through a selective hydrogenation reaction to obtain a selective hydrogenation product; (B) feeding the selective hydrogenation product into an etherification unit for etherification reaction to obtain MTBE and ether products, wherein the MTBE is discharged; (C) sending the etherification products to a precision distillation unit to obtain saturated light hydrocarbons or alkane-rich hydrocarbons, polymerization-grade 1-butene and C4 in the bottom of the tower, wherein the saturated light hydrocarbons or alkane-rich hydrocarbons are sent out and the polymerization-grade 1-butene is output as a product; (D) feeding the C4 fraction from the bottom of the tower into an extraction pre-fractionation unit for fractionation to obtain three streams of materials: a saturated hydrocarbon fraction or an alkane-rich fraction, a 2-butene-rich fraction, and a heavy C4 fraction, wherein the saturated hydrocarbon fraction or the alkane-rich fraction and the heavy C4 fraction are discharged; (E) The 2-butene-rich fraction is fed to a 2-butene isomerization unit to isomerize 2-butene to 1-butene, and the 1-butene-rich isomerized product is fed back to the precision distillation unit.

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