Method and system for preparing isomeric C8 olefin through selective superposition of C4 olefin

Abstract

The invention relates to the field of olefin superimposition, and discloses a method and a system for preparing isomeric C8 olefin through selective superimposition of C4 olefin. The method comprises the following steps: (1) in the presence of a reaction regulator, carrying out a superposition reaction on a C4 raw material; (2) in the presence of a separation regulator, performing first separation on a material obtained by the superposition reaction in the step (1) in a residual raw material separation tower to obtain residual raw materials, a reaction regulator, the separation regulator, isomeric C8 olefin and a superposition product at the tower bottom; (3) sequentially introducing the bottom material of the residual raw material separation tower into a regulator recovery tower and an isomerized C8 separation tower, and carrying out second separation and third separation to obtain an isomerized C8 olefin gas phase; and (4) carrying out first heat exchange on the isomeric C8 olefin gas phase obtained in the step (3) and the residual raw material separation tower side draw-out material. By adopting the method disclosed by the invention, the purpose of further reducing the separation energy consumption can be achieved.

Description

Technical Field

[0001] This invention relates to the field of olefin fusion, and more specifically to a method and system for the selective fusion of C4 olefins to produce isomeric C8 olefins. Background Technology

[0002] The mixed C4 fraction produced by the catalytic cracking or catalytic pyrolysis units of oil refineries is mainly composed of C4 alkanes and olefins such as n-butane, isobutane, isobutene, 1-butene, cis-2-butene, and trans-2-butene. Typically, this fraction is used as feedstock for alkylation units to produce high-octane gasoline after isobutene is removed by a methyl tert-butyl ether (MTBE) unit.

[0003] The mixed C4 fraction extracted from the ethylene cracking unit of chemical enterprises, after removing butadiene, is mainly composed of C4 alkanes and alkenes such as n-butane, isobutane, isobutene, 1-butene, cis-2-butene, and trans-2-butene. However, its C4 alkanes content is very low, and it is mainly composed of C4 alkenes. Usually, this fraction is used to remove isobutene in an MTBE unit to produce high-purity 1-butene.

[0004] With the rapid development of China's new energy industry, refineries and chemical companies need to find higher-value processing routes for their C4 resources. Selective C4 olefin alkylation technology is a promising C4 processing technology. Its main characteristic is that isobutylene in mixed C4 fractions selectively alkylates into alkylation products with isooctene as the main component under the action of an alkylation catalyst. The resulting alkylation product is C8-C4. 12 The olefins are further separated to obtain isooctene, which is used as a chemical raw material. The remaining mixed C4 fraction after the reaction can still be processed using the original process flow. The selective alkylation of C4 olefins to produce isooctene, followed by the production of isononol from isooctene, is an important route for the production of isononol. Isononol is a high-performance organic compound with excellent temperature resistance, chemical resistance, electrical insulation, and lubricity, and is widely used in electronic components, pharmaceuticals, fragrances, cosmetics, and other fields. Therefore, this method has broad application prospects.

[0005] In the selective polymerization reaction of C4 olefins, isobutylene polymerization is prone to occur, causing the dry point of the polymerized gasoline to exceed the standard. Therefore, a reaction regulator needs to be introduced into the C4 olefin selective polymerization reaction system to control the polymerization reaction of isobutylene. The reaction regulator is basically not consumed during the reaction and needs to be recycled through separation. This separation process usually requires a high reflux ratio and has high energy consumption. CN108976102A discloses a method and system for recovering isobutylene polymerization inhibitors. This application proposes to connect a catalytic distillation column after the isobutylene polymerization reactor, and to recover and reuse the inhibitor through a side extraction line 10 to 12 trays below the feed inlet of the catalytic distillation column, or to add a rectification column after the catalytic distillation column as an inhibitor recovery column to complete the inhibitor recovery. However, this method has a high reflux ratio in the catalytic distillation column and high energy consumption of the device. In addition, the temperature of the bottom of the catalytic distillation column is high, and a high-temperature heat source is required to provide the heat required for separation. CN109354567A discloses an isobutylene fusion system and fusion process method derived from a methyl tert-butyl ether (MTBE) unit. The isobutylene fusion system comprises a feeding unit, a fusion unit, a catalytic distillation unit, and an inhibitor recovery unit. The inhibitor recovery unit consists of an inhibitor extraction tower and an inhibitor rectification recovery tower connected together. The mixture and inhibitor undergo pre-reaction in the fusion reactor, followed by deep fusion reaction in the catalytic distillation tower, and then inhibitor recovery and fusion product extraction are completed via the inhibitor extraction tower and inhibitor rectification recovery tower. This method has a high reflux ratio in the catalytic distillation tower, resulting in high energy consumption. Furthermore, the high temperature at the bottom of the catalytic distillation tower necessitates the use of a high-temperature heat source to provide the heat required for separation.

[0006] On the other hand, the product of the C4 selective squaring reaction is C8-C. 12 Olefins, including isooctene which can be used to produce isononol, have boiling points close to those of other C8 olefin isomers. Separating isooctene from the composite products requires a high reflux ratio, resulting in high energy consumption during the isooctene separation process.

[0007] In conclusion, it is essential to develop a method for the selective fusion of C4 olefins to produce isomeric C8 olefins that features a simple process, high product separation accuracy, and lower energy consumption. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem of high energy consumption in product separation in the prior art, and to provide a method and system for selectively synthesizing C4 olefins to produce isomeric C8 olefins, so as to further reduce separation energy consumption.

[0009] To achieve the above objectives, the present invention provides a method for selectively assembling C4 olefins to prepare isomeric C8 olefins, the method comprising:

[0010] (1) In the presence of a reaction regulator, the C4 raw materials are subjected to a superposition reaction;

[0011] (2) In the presence of a separation regulator, the material obtained by the superposition reaction in step (1) is first separated in a residual raw material separation tower, and the residual raw material, reaction regulator, separation regulator, isomeric C8 olefin and superposition product are obtained at the bottom of the tower.

[0012] (3) The bottom material of the remaining raw material separation tower is sequentially introduced into the regulator recovery tower and the isomeric C8 separation tower for second and third separation to obtain isomeric C8 olefins;

[0013] (4) The isomeric C8 olefin gas phase obtained in step (3) is subjected to a first heat exchange with the remaining raw material side stream extract from the separation tower.

[0014] A second aspect of the present invention provides a system for the selective fusion of C4 olefins to produce isomeric C8 olefins, the system comprising: a fusion reaction unit and a product separation unit connected in sequence;

[0015] The superposition reaction unit includes a superposition reactor for superposition reaction of C4 olefins;

[0016] The product separation unit includes a residual raw material separation tower, a regulator recovery tower, and an isomeric C8 separation tower. The residual raw material separation tower is used to perform a first separation on the material obtained from the superposition reaction. A second residual raw material is obtained at the top of the tower, and a bottom material containing a separation regulator, a reaction regulator, isomeric C8, and superposition products is obtained at the bottom of the tower.

[0017] The regulator recovery tower is used to perform a second separation on the bottom material of the remaining raw material separation tower, and the top material contains separation regulator and reaction regulator, while the bottom material contains isomeric C8 olefin and overlapping product.

[0018] The isomeric C8 separation tower is used to perform a third separation on the bottom material of the regulator recovery tower, with overlapping products obtained at the bottom and isomeric C8 olefin gas phase obtained at the top.

[0019] The remaining raw material separation tower is also equipped with a mid-section reboiler. The mid-section reboiler 15 is used to perform a first heat exchange between the isomeric C8 olefin gas phase and the side stream extract of the remaining raw material separation tower to obtain the isomeric C8 olefin liquid phase.

[0020] The beneficial effects of the present invention through the above technical solution include:

[0021] The method for selectively synthesizing isomeric C8 olefins using C4 olefins provided by this invention involves product separation in the presence of a separation regulator. Under the same residual feed separation precision conditions (controlling the second residual feed to be essentially free of reaction regulators) and isomeric C8 separation precision conditions (isooctene content in the isomeric C8 olefin greater than 95%), compared to not introducing a separation regulator, it can significantly reduce the reflux ratio of the residual feed separation column and significantly reduce the tray temperature of the stripping section of the residual feed separation column, making it significantly lower than the top material temperature of the isomeric C8 separation column. Sufficient heat exchange between the top material of the isomeric C8 separation column and the side-stream feed from the residual feed separation column further significantly reduces the reboiler energy consumption of the residual feed separation column, reducing the separation energy consumption of the residual feed separation column by 20-70%. Since the residual feed separation column accounts for a high proportion of the total energy consumption, the overall energy-saving effect of the method described in this invention is significant. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process flow for selectively synthesizing isomeric C8 olefins using C4 olefins in Embodiment 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the process flow for selectively synthesizing isomeric C8 olefins using C4 olefins in Embodiment 2 of the present invention.

[0024] Explanation of reference numerals in the attached figures

[0025] A. Raw material pretreatment unit; B. Superposition reaction unit; C. Product separation unit;

[0026] 1. C4 raw material; 2. Demineralized water; 3. Wash water;

[0027] 4. C4 feedstock after water washing; 5. Materials obtained from the superposition reaction; 6. Separation regulator;

[0028] 7. Secondary residual raw material; 8. Reaction regulator; 9. Isomerized C8 olefin;

[0029] 10. Water washing tower; 11. Composite reactor; 12. Residual feed separation tower; 13. Conditioner recovery tower; 14. Heterogeneous C8 separation tower; 15. Mid-section reboiler; 16. Tower inlet heat exchanger; 17. Composite product. Detailed Implementation

[0030] 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.

[0031] In the description of this invention, it should be understood that the terms "top," "bottom," etc., indicating orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0032] In this invention, the unit "ppm(w)" refers to one part per million by mass, and the unit "ppm(v)" refers to one part per million by volume.

[0033] The first aspect of this invention provides a method for selectively assembling C4 olefins to produce isomeric C8 olefins, the method comprising:

[0034] (1) In the presence of a reaction regulator, the C4 raw materials are subjected to a superposition reaction;

[0035] (2) In the presence of a separation regulator, the material obtained by the superposition reaction in step (1) is first separated in a residual raw material separation tower, and the residual raw material, reaction regulator, separation regulator, isomeric C8 olefin and superposition product are obtained at the bottom of the tower.

[0036] (3) The bottom material of the remaining raw material separation tower is sequentially introduced into the regulator recovery tower and the isomeric C8 separation tower for second and third separation to obtain isomeric C8 olefin gas phase;

[0037] (4) The isomeric C8 olefin gas phase obtained in step (3) is subjected to a first heat exchange with the remaining raw material side stream extract from the separation tower.

[0038] In existing technologies, the tray temperature in the stripping section of the residual feed separation tower is relatively high, and the tray temperature at the side feed outlet of the residual feed separation tower is close to the temperature of the top product in the heterogeneous C8 separation tower. This makes heat exchange between the side feed from the residual feed separation tower and the top product in the heterogeneous C8 separation tower difficult. However, the method provided by this invention, by adding a separation regulator, significantly reduces the reflux ratio of the residual feed separation tower itself, and simultaneously significantly reduces the tray temperature in the stripping section of the residual feed separation tower, making it significantly lower than the temperature of the top product in the heterogeneous C8 separation tower. This allows for sufficient heat exchange between the top product in the heterogeneous C8 separation tower and the side feed from the residual feed separation tower, further reducing energy consumption.

[0039] According to the present invention, preferably, the superposition reaction in step (1) includes: superposition reaction of C4 raw materials under the action of reaction regulator and catalyst and optionally separation regulator.

[0040] The present invention does not impose any particular limitations on the conditions of the superposition reaction, and can be carried out with reference to conventional methods in the art.

[0041] The present invention allows for a wide range of selections of the C4 feedstock, which can be various C4 feedstocks commonly used in the art. Preferably, the C4 feedstock is a catalytic cracked C4 fraction and / or an ethylene cracked C4 fraction.

[0042] The present invention allows for a wide range of choices for the reaction regulator, which can be various reaction regulators commonly used in the art. Preferably, the reaction regulator is selected from at least one of tert-butanol, water, methyl tert-butyl ether, and methanol, and more preferably tert-butanol. All of the above substances are commercially available.

[0043] The present invention allows for a wide range of dosage options for the reaction regulator. Preferably, the dosage of the reaction regulator is 0.1-5% of the mass flow rate of the C4 feedstock.

[0044] This invention allows for a wide range of catalyst selection, encompassing various catalysts commonly used in the art. Preferably, the catalyst is a sulfonic acid-type ion exchange resin catalyst. The catalyst can be commercially available or prepared using methods known to those skilled in the art.

[0045] The present invention does not have a particular limitation on the amount of the catalyst used, and it can be carried out in accordance with conventional methods in the art.

[0046] According to the present invention, preferably, the superposition reaction is carried out in a superposition reactor.

[0047] The present invention does not particularly limit the type of the superimposed reactor, and any reactor capable of performing the above-mentioned superimposed reaction can be used. Preferably, the superimposed reactor is selected from a fixed-bed reactor, a bubble-point reactor, or a tubular reactor.

[0048] Since the separation regulator described in this invention is consumed at minimal rate throughout the process, there is no particular limitation on the timing of its addition. It can be added in step (1) or step (2). Preferably, the separation regulator is added in step (1) and / or step (2).

[0049] According to the present invention, preferably, the C4 raw material is pretreated before undergoing the superposition reaction. This preferred embodiment can effectively remove metal and basic nitride impurities from the C4 raw material.

[0050] Preferably, the pretreatment is selected from water washing and / or purification treatment with a purifying agent. The above pretreatment method is a conventional method in the art, and the specific operation can be carried out according to conventional methods in the art. It will not be described in detail here.

[0051] When the C4 feedstock contains unsaturated olefins (such as dienes), the pretreatment preferably further includes selective hydrogenation. This preferred embodiment allows the unsaturated olefins to be saturated.

[0052] The superposition method described in this invention is carried out in the presence of a separation regulator, which helps to reduce energy consumption and save costs. Meanwhile, the separation regulator described in this invention is readily available, has good miscibility with the reactants, and does not affect the reaction performance. Preferably, the separation regulator contains at least one of C4 alkane, C4 olefin, C5 alkane, C5 olefin, C6 alkane, and C6 olefin, and more preferably contains at least one of cis-2-butene, trans-2-butene, and isopentane.

[0053] To reduce separation energy consumption, preferably, based on the total mass of the separation regulator, the mass content of cis-2-butene, trans-2-butene, and isopentane is 40% or more, and more preferably 70% or more.

[0054] Particularly preferably, the separation regulator contains cis-2-butene and / or trans-2-butene.

[0055] The present invention allows for a wide range of specific types of separation regulators; any regulator possessing the aforementioned characteristics and components can be used. Preferably, the separation regulator is selected from light naphtha and / or at least a portion of the remaining raw materials.

[0056] The distillation range of the light naphtha described in this invention is generally 5-80℃, and light naphtha obtained by various methods commonly used in the art can be used.

[0057] According to the present invention, preferably, the amount of the separation regulator is 0.1-20% of the mass flow rate of the composite product, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, and any two of these values ​​forming a range, preferably 0.5-10%. Using this preferred embodiment, under the same separation accuracy conditions, it is more advantageous to reduce separation energy consumption.

[0058] According to the present invention, preferably, a second residual raw material is obtained at the top of the residual raw material separation tower, wherein the proportion of reaction regulator in the second residual raw material is less than 500 ppm, preferably less than 50 ppm.

[0059] When the separation regulator is selected from the residual feed, the bottom of the residual feed separation column yields a bottom product containing the first residual feed, the reaction regulator, isomeric C8 olefins, and overlapping products; the top of the residual feed separation column yields the second residual feed. In this case, the first residual feed is the separation regulator.

[0060] According to the present invention, preferably, the bottom material of the remaining raw material separation tower is introduced into the regulator recovery tower for a second separation, and the bottom material of the tower is obtained as isomeric C8 olefins and overlapping products, and the top material of the tower is obtained as containing separation regulator and reaction regulator.

[0061] The bottom material of the regulator recovery tower is introduced into the isomeric C8 separation tower for the third separation. The bottom of the tower yields an overlapping product, and the top of the tower yields an isomeric C8 olefin gas phase.

[0062] According to the present invention, preferably, the mass content of isooctene in the gas phase of the isomeric C8 olefin is greater than 95%.

[0063] According to the present invention, preferably, the overlapping product is C8-C. 12 olefins.

[0064] The present invention does not particularly limit the residual raw material separation tower, the regulator recovery tower and the heterogeneous C8 separation tower, and can be any fractionation tower conventionally used in the art.

[0065] The residual raw material separation tower, regulator recovery tower, and heterogeneous C8 tower described in this invention are all equipped with their own matching reboilers, the heat of which is provided by the outside. This is a conventional setup in the field and is not shown in the accompanying drawings of this invention.

[0066] According to the present invention, preferably, the conditions for the first separation, the second separation, and the third separation each independently include: a column top temperature of 20-200°C, a column bottom temperature of 20-220°C, a column top pressure of 0-1 MPaG, and a reflux ratio of 0.1-30. In the superposition method provided by the present invention, product separation is carried out under operating conditions with a relatively low reflux ratio, and the heat contained in the high-temperature materials in the method is fully utilized, which is beneficial for reducing energy consumption and saving equipment investment.

[0067] According to the present invention, preferably, the conditions for the first separation include: a column top temperature of 40-70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, and any value within the range formed by any two of these values; and a column bottom temperature of 120-210°C, for example, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 2 ... The preferred embodiment allows for the separation of residual raw materials under operating conditions with a lower reflux ratio, which helps reduce energy consumption and save costs. The tower top pressure is 0.3-0.7 MPaG, for example, 0.3 MPaG, 0.4 MPaG, 0.5 MPaG, 0.6 MPaG, 0.7 MPaG, and any value within the range of any two of these values.

[0068] According to the present invention, preferably, the conditions for the second separation include: a column top temperature of 50-120°C, a column bottom temperature of 120-160°C, a column top pressure of 0-0.4 MPaG, and a reflux ratio of 2-25.

[0069] According to the present invention, preferably, the conditions for the third separation include: a column top temperature of 80-160°C, a column bottom temperature of 130-190°C, a column top pressure of 0-0.5 MPaG, and a reflux ratio of 1-10.

[0070] Both the reaction regulator and the separation regulator described in this invention are recyclable and reusable, which helps to save costs. The reaction regulator and the separation regulator can be recycled and reused together or separately.

[0071] When the reaction regulator and separation regulator are recycled and reused together, preferably, the reaction regulator and separation regulator are returned to step (1) and mixed with the C4 feedstock.

[0072] When the reaction regulator and the separation regulator are recycled and reused separately, preferably, the reaction regulator is returned to step (1) and mixed with the C4 raw material, and the separation regulator is returned to step (2) and mixed with the material obtained from the superposition reaction.

[0073] According to the present invention, preferably, step (4) includes: exchanging the gas phase of the isomeric C8 olefin obtained in step (3) with the side stream extract of the remaining raw material separation tower to obtain the liquid phase of the isomeric C8 olefin.

[0074] Preferably, the heat exchange temperature difference of the side-stream extract of the remaining raw material separation tower is 15-60℃.

[0075] The heat exchange temperature difference described in this invention is: [(hot side inlet temperature - cold side outlet temperature) + (hot side outlet temperature - cold side inlet temperature)] / 2

[0076] In this invention, the hot side temperature refers to the temperature of isomeric C8 olefins, and the cold side temperature refers to the temperature of the side stream feed at the same tray of the residual feed separation tower.

[0077] It should be noted that, generally speaking, the larger the heat exchange temperature difference, the smaller the total heat exchange area of ​​the heat exchange equipment.

[0078] According to the present invention, preferably, the method further includes: subjecting the isomeric C8 olefin liquid phase to a second heat exchange with the material obtained by the superposition reaction in step (1) to obtain a low-temperature isomeric C8 olefin liquid phase.

[0079] Understandably, the isomeric C8 olefin liquid phase provides the corresponding heat according to the temperature requirements of the second heat exchange.

[0080] The method described in this invention fully utilizes the latent heat (first heat exchange) and sensible heat (second heat exchange) of the gas phase at the top of the heterogeneous C8 separation tower, which is beneficial to the stable operation of each separation tower in different operating cycles, and minimizes the total heat exchange area of ​​the heat exchange equipment.

[0081] Preferably, the low-temperature isomeric C8 olefin liquid phase is recovered.

[0082] A second aspect of the present invention provides a system for the selective fusion of C4 olefins to produce isomeric C8 olefins, the system comprising: a fusion reaction unit B and a product separation unit C connected in sequence;

[0083] The superposition reaction unit B includes a superposition reactor 11, which is used to carry out a superposition reaction of C4 olefins.

[0084] The product separation unit C includes a residual raw material separation tower 12, a regulator recovery tower 13, and an isomeric C8 separation tower 14. The residual raw material separation tower 12 is used to perform a first separation on the material obtained from the superposition reaction. A second residual raw material is obtained at the top of the tower, and a bottom material containing a separation regulator, a reaction regulator, an isomeric C8 olefin, and superposition products is obtained at the bottom of the tower.

[0085] The regulator recovery tower 13 is used to perform a second separation on the bottom material of the remaining raw material separation tower 12, and the top material containing separation regulator and reaction regulator is obtained, while the bottom material contains isomeric C8 olefin and overlapping product.

[0086] The isomeric C8 separation tower 14 is used to perform a third separation on the bottom material of the regulator recovery tower 13, with the bottom of the tower yielding an overlapping product and the top of the tower yielding an isomeric C8 olefin gas phase.

[0087] The residual feed separation tower 12 is also equipped with a mid-section reboiler 15, which is used to perform a first heat exchange between the isomeric C8 olefin gas phase and the side stream extract of the residual feed separation tower to obtain the isomeric C8 olefin liquid phase.

[0088] The isomeric C8 olefin gas phase is subjected to a first heat exchange with the remaining raw material side stream extract from the separation tower to obtain the isomeric C8 olefin liquid phase. This preferred embodiment is beneficial for making full use of the latent heat of the isomeric C8 olefin gas phase.

[0089] According to the present invention, preferably, the system further includes a tower inlet heat exchanger 16 disposed between the superposition reactor 11 and the residual raw material separation tower 12. The tower inlet heat exchanger 16 is used for a second heat exchange between the isomeric C8 olefin liquid phase and the material obtained from the superposition reaction to obtain a low-temperature isomeric C8 olefin liquid phase. By performing a second heat exchange between the isomeric C8 olefin liquid phase and the material obtained from the superposition reaction to obtain a low-temperature isomeric C8 olefin liquid phase, this preferred embodiment is beneficial for fully utilizing the sensible heat of the isomeric C8 separation tower's overhead gas phase after the first heat exchange, which transforms into the isomeric C8 olefin liquid phase.

[0090] The target product of the low-temperature isomerized C8 olefin liquid phase described in this invention is collected and utilized.

[0091] In this invention, the top material of the regulator recovery tower 13 containing the separation regulator and the reaction regulator can be recovered and reused together or separately.

[0092] When recycled together, preferably, the top outlet of the regulator recovery tower 13 is connected to the feed inlet of the superimposed reactor 11.

[0093] When recycled separately, preferably, the top outlet of the regulator recovery tower 13 is connected to the feed inlet of the residual raw material separation tower 12, and the side outlet of the regulator recovery tower 13 is connected to the feed inlet of the superimposed reactor 11.

[0094] According to the present invention, preferably, the residual raw material separation tower 12 is further provided with a separation regulator inlet for introducing a separation regulator from outside the system.

[0095] According to the present invention, preferably, the system further includes: a raw material pretreatment unit A connected to the feed inlet of the superposition reaction unit B, for pretreating the raw materials.

[0096] According to the present invention, preferably, the raw material pretreatment unit A includes a water washing tower 10 and / or a purification tower.

[0097] According to a specific embodiment of the present invention, such as Figure 1 As shown, C4 feedstock 1 is introduced to the bottom of the water washing tower 10 in feedstock pretreatment unit A, and demineralized water 2 is introduced to the top of the water washing tower 10. Inside the water washing tower 10, C4 feedstock 1 and demineralized water 2 are in countercurrent contact. Wash water 3 is drawn out from the bottom of the water washing tower 10. The washed C4 feedstock 4 is introduced from the top of the water washing tower 10 into the superposition reactor 11 of the superposition reaction unit B. In the superposition reactor 11, the selective superposition reaction of isobutylene mainly occurs. The superposition reaction post-reaction material 5 at the outlet of the superposition reactor is introduced into the residual feedstock separation tower 12 in the product separation unit C. The top stream of the residual feedstock separation tower 12 is the second residual feedstock 7, and the bottom stream (the first residual feedstock, namely separation regulator 6, reaction regulator 8, and isomeric C8olefin 9) is... The superimposed product 17 is introduced into the regulator recovery tower 13 in the product separation unit C. The overhead stream of the regulator recovery tower 13 is a mixture containing reaction regulator 8 and separation regulator 6. This mixture is mixed with the washed C4 feed 4 and returned to the superimposed reactor 11 in the superimposed reaction unit B. The bottom stream of the regulator recovery tower 13 (isomeric C8 olefin 9 and superimposed product 17) is introduced into the isomeric C8 separation tower 14 in the product separation unit C. The overhead stream of the isomeric C8 separation tower 14 is isomeric C8 olefin 9. It is then introduced into the intermediate reboiler 15 and the tower inlet heat exchanger 16 of the residual feed separation tower 12 for heat exchange and recycling. The bottom stream of the isomeric C8 separation tower 14 is the superimposed product 17.

[0098] The flow path of the regulator recovery tower 13 can also include: the top stream of the regulator recovery tower 13 is the separation regulator 6, which is mixed with the material 5 obtained from the superposition reaction and returned to the residual raw material separation tower 12; the side stream outlet of the regulator recovery tower 13 collects the reaction regulator 8, which is mixed with the water-washed C4 raw material 4 and returned to the superposition reactor 11 of the superposition reaction unit B. For example, refer to... Figure 2 .

[0099] According to a specific embodiment of the present invention, such as Figure 2As shown, C4 feedstock 1 is introduced to the bottom of the water washing tower 10 in feedstock pretreatment unit A, and demineralized water 2 is introduced to the top of the water washing tower 10. Inside the water washing tower 10, C4 feedstock 1 and demineralized water 2 are in countercurrent contact. Wash water 3 is drawn out from the bottom of the water washing tower 10. The washed C4 feedstock 4 is introduced into the superposition reactor 11 in superposition reaction unit B. In the superposition reactor 11, the selective superposition reaction of isobutylene mainly occurs. The superposition reaction post-reaction material 5 at the outlet of the superposition reactor is introduced into the residual feedstock separation tower 12 in product separation unit C. At the same time, the separation regulator 6 is introduced from the outside into the residual feedstock separation tower 12. The top stream of the residual feedstock separation tower 12 is the second residual feedstock 7, and the bottom stream (separation regulator 6, reaction regulator 8, isomeric C8olefin 9, superposition product 17) is introduced into product separation unit C. The regulator recovery tower 13 has a top stream of separation regulator 6. The separation regulator 6 is mixed with the material 5 obtained from the superposition reaction and returned to the residual raw material separation tower 12. The side stream outlet of the regulator recovery tower 13 collects reaction regulator 8. The reaction regulator 8 is mixed with the water-washed C4 raw material 4 and returned to the superposition reactor 11 of the superposition reaction unit B. The bottom stream of the regulator recovery tower 13 (isomeric C8 olefin 9 and superposition product 17) is introduced into the isomeric C8 separation tower 14 in the product separation unit C. The top stream of the isomeric C8 separation tower 14 is isomeric C8 olefin 9. It is introduced into the intermediate reboiler 15 and the tower inlet heat exchanger 16 of the residual raw material separation tower 12 for heat exchange and recycling. The bottom stream of the isomeric C8 separation tower 14 is superposition product 17.

[0100] The flow path of the regulator recovery tower 13 can also include: the top stream of the regulator recovery tower 13 is a mixture stream containing reaction regulator 8 and separation regulator 6, which is mixed with the washed C4 feedstock 4 and returned to the superposition reactor 11 of the superposition reaction unit B. For example, see reference Figure 1 .

[0101] In this invention, the terms "first," "second," and "third" do not limit the substances and operations, but are only used to distinguish the substances introduced in different steps and the operations performed in different stages.

[0102] The present invention will be described in detail below through embodiments.

[0103] The composite catalyst is a commercially available product from Kerry Environmental Protection Technology Co., Ltd., with the brand name KC110.

[0104] Example 1

[0105] use Figure 1The method for selectively synthesizing isomeric C8 olefins from C4 olefins is shown. The feedstock is C4 feedstock from a refinery, and its mass composition is shown in Table 1. The synthesizing catalyst used is a sulfonic acid type ion exchange resin catalyst. The reaction regulator is tert-butanol, used at 2% of the mass flow rate of the C4 feedstock. The synthesizing reactor is a fixed-bed reactor. The separation regulator is the first residual feedstock, whose mass composition is shown in Table 3. It is used at 0.9% of the mass flow rate of the synthesized product. The isooctene content in the isomeric C8 olefins obtained after the third separation is 95.5%. The composition of the second residual feedstock is shown in Table 1, and the main operating conditions of the fractionation tower in the product separation unit are shown in Table 2.

[0106] Example 2

[0107] use Figure 2 The method for selectively synthesizing C4 olefins is shown. The feedstock is C4 feedstock from a refinery, and its mass composition is shown in Table 1. The synthesizing catalyst used is a sulfonic acid type ion exchange resin catalyst. The reaction regulator is tert-butanol, used at 2% of the mass flow rate of the mixed C4. The synthesizing reactor is a tubular reactor. The separation regulator is added reformate topping oil, with its mass composition shown in Table 3, used at 0.9% of the mass flow rate of the synthesized product. The isooctene content in the isooctene obtained after the third separation is 95.3%. The composition of the second remaining feedstock is shown in Table 1, and the main operating conditions of the fractionation tower in the product separation unit are shown in Table 2.

[0108] Comparative Example 1

[0109] The method of Example 1 is followed, except that no separation regulator is introduced. That is, the top stream of the residual raw material separation tower 12 is the residual raw material, and the bottom stream (reaction regulator 8, isomeric C8 olefin 9, and overlapping product 17) is introduced into the regulator recovery tower 13 in the product separation unit C. The top stream of the regulator recovery tower 13 is the reaction regulator 8. The reaction regulator 8 is mixed with the water-washed C4 raw material 4 and returned to the superposition reactor 11 in the superposition reaction unit B. The bottom stream (isomeric C8 olefin 9 and overlapping product 17) is introduced into the isomeric C8 separation tower 14 in the product separation unit C. The top stream of the isomeric C8 separation tower 14 is the isomeric C8 olefin 9 (isooctene mass content is 95.4%), and the bottom stream is the overlapping product 17. Because the separation regulator 6 is not introduced, under the same conditions of residual feed separation accuracy (controlling the second residual feed to be basically free of reaction regulator), the required reflux ratio of the residual feed separation tower 12 is high. In addition, the temperature of the trays in the stripping section of the residual feed separation tower 12 is high. The temperature of the trays at the same side-stream sampling position as in Example 1 is close to the temperature of the top material of the heterogeneous C8 separation tower 14. The middle section reboiler 15 of the residual feed separation tower 12 cannot exchange heat with the top material of the heterogeneous C8 separation tower 14.

[0110] The composition of the residual feed at the top of the residual feed separation tower is shown in Table 1, and the main operating conditions of the product separation unit fractionation tower are shown in Table 2.

[0111] Table 1

[0112]

[0113]

[0114] Table 2

[0115]

[0116]

[0117] Note: The loads of the intermediate reboiler and the tower inlet heat exchanger are internal circulating energy; the load of the tower bottom reboiler is externally introduced energy.

[0118] Hot side temperature refers to the temperature of isomeric C8 olefins, while cold side temperature refers to the temperature of the side stream feed extracted from the same tray in the residual feed separation tower.

[0119] Table 3

[0120]

[0121] As can be seen from Tables 2 and 3, the superposition method provided by this invention, under similar separation accuracy of the residual feed separation tower, significantly reduces the required reflux ratio of the residual feed separation tower compared to not introducing a separation regulator, and substantially reduces the tray temperature of the stripping section of the residual feed separation tower. Under similar separation accuracy of isomeric C8 olefins, the top material of the isomeric C8 separation tower is used to sequentially exchange heat with the intermediate reboiler and the inlet heat exchanger of the residual feed separation tower, further significantly reducing the energy consumption of the reboiler in the residual feed separation tower. Since the residual feed separation tower accounts for a high proportion of the total energy consumption, the overall energy-saving effect of the method described in this invention is significant.

[0122] Compared with Comparative Example 1, under the condition that the separation accuracy of the residual raw material separation tower and the heterogeneous C8 separation tower is the same, the temperature of the material taken out from the side stream of the residual raw material separation tower in Example 1 is reduced by 26.1°C, and the energy consumption of the reboiler in the bottom of the residual raw material separation tower is reduced by about 54%, which shows a significant energy-saving effect.

[0123] 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 selectively synthesizing isomeric C8 olefins using C4 olefins, characterized in that, The method includes: (1) In the presence of a reaction regulator, the C4 raw materials are subjected to a superposition reaction; (2) In the presence of a separation regulator, the material obtained by the superposition reaction in step (1) is first separated in a residual raw material separation tower, and the residual raw material, reaction regulator, separation regulator, isomeric C8 olefin and superposition product are obtained at the bottom of the tower. (3) The bottom material of the remaining raw material separation tower is sequentially introduced into the regulator recovery tower and the isomeric C8 separation tower for second and third separation to obtain isomeric C8 olefin gas phase; (4) The isomeric C8 olefin gas phase obtained in step (3) is subjected to a first heat exchange with the remaining raw material side stream extract from the separation tower.

2. The overlapping method according to claim 1, wherein, The superposition reaction in step (1) includes: superposition reaction of C4 raw materials under the action of reaction regulator and catalyst and optionally separation regulator; Preferably, the C4 feedstock is a catalytically cracked C4 fraction and / or an ethylene cracked C4 fraction; Preferably, the reaction regulator is selected from at least one of tert-butanol, water, methyl tert-butyl ether and methanol, more preferably tert-butanol; Preferably, the amount of the reaction regulator is 0.1-5% of the mass flow rate of the C4 feedstock; Preferably, the catalyst is a sulfonic acid type ion exchange resin catalyst.

3. The method according to claim 1 or 2, wherein, The separation regulator contains at least one of C4 alkane, C4 olefin, C5 alkane, C5 olefin, C6 alkane, and C6 olefin, preferably at least one of cis-2-butene, trans-2-butene, and isopentane; Preferably, based on the total mass of the separation regulator, the mass content of cis-2-butene, trans-2-butene, and isopentane is 40% or more, and more preferably 70% or more; Preferably, the separation regulator is selected from light naphtha and / or at least a portion of the remaining raw materials.

4. The overlapping method according to any one of claims 1-3, wherein, The amount of the separation regulator is 0.1-20% of the mass flow rate of the composite product, preferably 0.5-10%.

5. The overlapping method according to any one of claims 1-4, wherein, The second residual raw material is obtained from the top of the residual raw material separation tower. The proportion of reaction regulator in the second residual raw material is less than 500 ppm, preferably less than 50 ppm.

6. The overlapping method according to any one of claims 1-5, wherein, The bottom material of the remaining raw material separation tower is introduced into the regulator recovery tower for a second separation. The bottom material of the tower is obtained as isomeric C8 olefins and overlapping products, and the top material of the tower contains separation regulators and reaction regulators. The bottom material of the regulator recovery tower is introduced into the isomeric C8 separation tower for the third separation. The bottom of the tower yields an overlapping product, and the top of the tower yields an isomeric C8 olefin gas phase. Preferably, in the gas phase of the iso-C8 olefin, the mass content of isooctene is greater than 95%; Preferably, the overlapping product is C8-C. 12 olefins.

7. The overlapping method according to any one of claims 1-6, wherein, The conditions for the first separation, the second separation, and the third separation each independently include: a column top temperature of 20-200℃, a column bottom temperature of 20-220℃, a column top pressure of 0-1MPaG, and a reflux ratio of 0.1-30; Preferably, the conditions for the first separation include: a column top temperature of 40-70°C, a column bottom temperature of 120-210°C, a column top pressure of 0.3-0.7 MPaG, and a reflux ratio of 0.2-0.6; Preferably, the conditions for the second separation include: a column top temperature of 50-120°C, a column bottom temperature of 120-160°C, a column top pressure of 0-0.4 MPaG, and a reflux ratio of 2-25. Preferably, the conditions for the third separation include: a column top temperature of 80-160°C, a column bottom temperature of 130-190°C, a column top pressure of 0-0.5 MPaG, and a reflux ratio of 1-10.

8. The overlapping method according to any one of claims 1-7, wherein, Step (4) includes: exchanging the gas phase of the isomeric C8 olefin obtained in step (3) with the side stream extract of the remaining raw material separation tower for the first heat exchange to obtain the liquid phase of the isomeric C8 olefin. Preferably, the method further includes: subjecting the isomeric C8 olefin liquid phase to a second heat exchange with the material obtained from the superposition reaction in step (1) to obtain a low-temperature isomeric C8 olefin liquid phase.

9. A system for the selective fusion of C4 olefins to produce isomeric C8 olefins, the system comprising: A superimposed reaction unit (B) and a product separation unit (C) are connected in sequence; The superposition reaction unit (B) includes a superposition reactor (11) for superposition reaction of C4 olefins; The product separation unit (C) includes a residual raw material separation tower (12), a regulator recovery tower (13), and an isomeric C8 separation tower (14). The residual raw material separation tower (12) is used to perform a first separation on the material obtained from the superposition reaction. A second residual raw material is obtained at the top of the tower, and a bottom material containing a separation regulator, a reaction regulator, an isomeric C8 olefin, and the superposition product is obtained at the bottom of the tower. The regulator recovery tower (13) is used to perform a second separation on the bottom material of the remaining raw material separation tower (12), and the top material containing separation regulator and reaction regulator is obtained, while the bottom material contains isomeric C8 olefin and overlapping product. The isomeric C8 separation tower (14) is used to perform a third separation on the bottom material of the regulator recovery tower (13), with the bottom of the tower yielding an overlapping product and the top of the tower yielding an isomeric C8 olefin gas phase. The residual raw material separation tower (12) is also equipped with a mid-section reboiler (15), which is used to perform a first heat exchange between the gas phase of the isomeric C8 olefin and the side-stream extract of the residual raw material separation tower to obtain the liquid phase of the isomeric C8 olefin.

10. The system according to claim 9, wherein, The system also includes a tower inlet heat exchanger (16) disposed between the superposition reactor (11) and the residual raw material separation tower (12), wherein the tower inlet heat exchanger (16) is used for a second heat exchange between the isomeric C8 olefin liquid phase and the material obtained by the superposition reaction to obtain a low-temperature isomeric C8 olefin liquid phase.

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