Carbon tetraolefin selective oligomerization process and system for carbon tetraolefin selective oligomerization reaction

Abstract

The present application relates to the field of olefin polymerization, and discloses a method for selectively polymerizing carbon four olefins and a system for selectively polymerizing carbon four olefins. The method for selectively polymerizing carbon four olefins comprises: (1) polymerizing carbon four raw materials in the presence of a reaction regulator; and (2) separating the material obtained in the step (1) in the presence of a separation regulator to obtain residual raw materials, the reaction regulator, the separation regulator and polymerization products. The method for selectively polymerizing carbon four olefins has the advantages of high product separation precision and low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of olefin fusion, and more specifically to a method for selective fusion of C4 olefins and a system for selective fusion reactions of C4 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] The MTBE unit is a crucial component in the processing of mixed C4 fractions. Mixed C4 fractions produced by catalytic cracking or catalytic decomposition units, after processing by the MTBE unit, not only better meet the alkyl-to-olefin ratio requirements of alkylation units, but also convert isobutene, which is not a suitable alkylation feedstock, into MTBE, a high-octane gasoline blending component with higher added value. The mixed C4 fractions byproducts of ethylene cracking units have a high 1-butene content, making them a good feedstock for producing high-purity 1-butene. However, isobutene and 1-butene have very similar boiling points, making separation difficult using conventional methods. The MTBE unit achieves the separation of isobutene and 1-butene through a chemical reaction.

[0005] With the gradual promotion and use of ethanol gasoline, and due to the potential for MTBE to pollute groundwater, MTBE production capacity will decline, and some MTBE production units will face shutdowns or conversions. Selective C4 olefin scavenging technology is a good alternative technology for MTBE production, capable of meeting the needs of subsequent processing of C4 fractions. The main characteristic of selective C4 olefin scavenging technology is that isobutylene in the mixed C4 fractions selectively scavenges under the action of a scavenging catalyst to form a scavenging product with isooctene as the main component. The resulting scavenging product is a high-octane gasoline component and an important chemical raw material. The remaining mixed C4 fraction after the reaction can still be processed using the original process flow.

[0006] 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. 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 recover and reuse the inhibitor through a side extraction line 10-12 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 rate in the catalytic distillation column and high energy consumption of the device; in addition, the bottom temperature of the catalytic distillation column is high, requiring a high-temperature heat source to provide the heat required for separation. CN109354567A discloses an isobutylene polymerization system and process method converted from a methyl tert-butyl ether unit. The isobutylene fusion system consists of a feeding unit, a fusion unit, a catalytic distillation unit, and an inhibitor recovery unit. The inhibitor recovery unit is composed of an inhibitor extraction tower and an inhibitor distillation recovery tower connected together. The mixture and inhibitor are pre-reacted in the fusion reactor, then undergo deep fusion reaction in the catalytic distillation tower, and finally the inhibitor is recovered and the fusion product is extracted by the inhibitor extraction tower and the inhibitor distillation recovery tower. This method has a high reflux ratio in the catalytic distillation tower and high energy consumption. In addition, the temperature of the bottom of the catalytic distillation tower is high, requiring a high-temperature heat source to provide the heat required for separation.

[0007] In conclusion, it is essential to develop a selective stoichiometry method for C4 olefins that is simple in process, feasible and reliable, has high product separation accuracy, and low separation 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 existing technologies, and to provide a method for selective superposition of C4 olefins and a system for the selective superposition reaction of C4 olefins. The selective superposition method for C4 olefins described in this invention has the advantages of high product separation accuracy and low separation energy consumption.

[0009] To achieve the above objectives, the present invention provides a method for selective superposition of carbotetraolefins, 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 from the superposition reaction in step (1) is separated to obtain the remaining raw material, reaction regulator, separation regulator and superposition product.

[0012] Preferably, the amount of the separation regulator is 0.1-20% of the mass flow rate of the composite product, and more preferably 2-10%.

[0013] A second aspect of the present invention provides a system for selective chelation reaction of C4 olefins, the system comprising: a chelation reaction unit and a product separation unit connected in sequence;

[0014] The superposition reaction unit includes a superposition reactor for superposition reaction of C4 olefins;

[0015] The product separation unit includes a residual raw material separation tower and a regulator recovery 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, and the superposition product is obtained at the bottom of the tower.

[0016] 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 containing separation regulator and reaction regulator is obtained, while the bottom material is obtained as a composite product.

[0017] The outlet of the regulator recovery tower is connected to the feed inlet of the superimposed reactor; or, the outlet of the regulator recovery tower is connected to the feed inlet of the residual raw material separation tower and the feed inlet of the superimposed reactor.

[0018] The beneficial effects of the present invention through the above technical solution include:

[0019] The selective superposition method for C4 olefins provided by this invention separates products in the presence of a separation regulator. Under the condition of achieving the same separation accuracy of the remaining raw materials (controlling the remaining raw materials to be essentially free of reaction regulators), the separation energy consumption can be reduced by 20-50% compared to not introducing a separation regulator. The energy consumption of the first separation tower accounts for about 70% of the total energy consumption, resulting in a significant overall energy-saving effect.

[0020] The selective superposition method for C4 olefins provided by this invention significantly reduces the bottom temperature of the first separation tower after introducing a separation regulator. This allows for the use of readily available low-temperature heat sources as the heat source for the reboiler of the residual feed separation tower, avoiding the use of high-temperature heat sources. Simultaneously, the bottom temperature of the residual feed separation tower is close to that of the C4 removal tower in a conventional MTBE unit, but lower than the design temperature (≤165℃) of the C4 removal tower in a conventional MTBE unit. The C4 removal tower and methanol recovery tower in a conventional MTBE unit can be reused as the residual feed separation tower and regulator separation tower, respectively, greatly reducing equipment costs. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the process flow of the selective superposition method of C4 olefins in Embodiment 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of the process flow of the selective superposition method of C4 olefins in Embodiment 2 of the present invention.

[0023] Explanation of reference numerals in the attached figures

[0024] A. Raw material pretreatment unit; B. Superposition reaction unit; C. Product separation unit;

[0025] 1. C4 raw material; 2. Demineralized water; 3. Wash water;

[0026] 4. C4 feedstock after water washing; 5. Materials obtained from the superposition reaction; 6. Separation regulator;

[0027] 7. Secondary residual raw material; 8. Reaction regulator; 9. Superposition product;

[0028] 10. Water washing tower; 11. Composite reactor; 12. Residual raw material separation tower; 13. Regulator recovery tower. Detailed Implementation

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The first aspect of this invention provides a method for selective superposition of carbotetraenes, the method comprising:

[0033] (1) In the presence of a reaction regulator, the C4 raw materials are subjected to a superposition reaction;

[0034] (2) In the presence of a separation regulator, the material obtained from the superposition reaction in step (1) is separated to obtain the remaining raw material, reaction regulator, separation regulator and superposition product.

[0035] 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.

[0036] 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.

[0037] Particularly preferably, the separation regulator contains cis-2-butene and / or trans-2-butene.

[0038] 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.

[0039] According to the present invention, preferably, the distillation range of the light naphtha is 5-80°C.

[0040] 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 value within any range of any two of these values, preferably 2-10%. Using this preferred embodiment, under the same separation accuracy conditions, it is more advantageous to reduce separation energy consumption.

[0041] The separation regulator described in this invention is consumed at minimal rate throughout the process; therefore, this invention does not impose any particular limitation on the timing of its addition. Preferably, the separation regulator is added in step (1) and / or in step (2).

[0042] According to the present invention, preferably, the separation in step (2) includes a first separation and a second separation, wherein the first separation is carried out in a residual raw material separation tower, and the bottom of the residual raw material separation tower yields a bottom material containing a separation regulator, a reaction regulator and a superposition product; and the top of the residual raw material separation tower yields a second residual raw material.

[0043] The bottom material of the remaining raw material separation tower is introduced into the regulator recovery tower for a second separation. The bottom of the tower yields a composite product, and the top of the tower yields a top material containing separation regulator and reaction regulator.

[0044] When the separation regulator is selected from the residual feedstock, the bottom of the residual feedstock separation column yields a bottom product containing the first residual feedstock, the reaction regulator, and the superposition product; the top of the residual feedstock separation column yields the second residual feedstock. In this case, the first residual feedstock is the separation regulator.

[0045] The present invention does not particularly limit the residual raw material separation tower and the regulator recovery tower, and can be any fractionation tower conventionally used in the art.

[0046] The residual raw material separation tower and the regulator recovery tower described in this invention are each equipped with their own matching reboilers to provide heat for the residual raw material separation tower and the regulator recovery tower. This is a conventional setup in the field and is not shown in the accompanying drawings of this invention.

[0047] According to the present invention, preferably, the top material of the regulator recovery tower provides at least a partial separation regulator and / or reaction regulator.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] According to the present invention, preferably, the superposition product is a C7-C12 olefin, more preferably isooctene.

[0052] According to the present invention, preferably, the conditions for the first separation and the second separation each independently include: a column top temperature of 20-200°C, a column bottom temperature of 20-200°C, a column top pressure of 0-1 MPaG, and a reflux ratio of 0.1-25. In the superposition method provided by the present invention, product separation is performed under operating conditions with a lower reflux ratio, which is beneficial for reducing energy consumption and saving equipment investment.

[0053] 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 120-165°C, for example, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, and any two of these values. The pressure at the top of the tower 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 two of these values; the reflux ratio is 0.2-0.6, for example, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, and any two of these values. This preferred embodiment allows for the separation of residual feedstock under operating conditions with a lower reflux ratio, which helps reduce energy consumption and save costs. The lower temperature of the residual feedstock separation tower bottom allows for the use of a low-temperature heat source as the heat source for the reboiler, avoiding the use of a high-temperature heat source. Furthermore, the lower temperature of the residual feedstock separation tower bottom is lower than the bottom temperature of the decarbonization tower in the conventional MTBE unit's product separation unit. The decarbonization tower and methanol recovery tower in the conventional MTBE unit can be reused as the residual feedstock separation tower and regulator separation tower, respectively, significantly reducing equipment costs.

[0054] 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 0-0.3 MPaG, and a reflux ratio of 2-20.

[0055] The selective chelation method for C4 olefins provided by this invention can achieve high separation accuracy of residual raw materials. Preferably, the proportion of reaction regulator in the second residual raw material is less than 500 ppm, more preferably less than 50 ppm, and even more preferably less than 20 ppm.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] According to the present invention, preferably, the superposition reaction is carried out in a superposition reactor.

[0064] Preferably, the superimposed reactor is selected from a fixed-bed reactor, a bubble-point reactor, or a tubular reactor.

[0065] In this invention, the main reaction occurring in the superposition reactor is the superposition reaction of isobutylene in the C4 feedstock. Preferably, when the isobutylene concentration in the C4 feedstock is less than or equal to 15 wt%, a fixed-bed or bubble-point reactor is used; when the isobutylene concentration in the C4 feedstock is greater than 15 wt%, a tubular reactor is used.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The selective superposition method for C4 olefins provided by this invention can utilize entirely new equipment as the separation unit (residual feed separation tower and regulator separation tower), or it can reuse the existing separation unit of a methyl tert-butyl ether unit. The latter effectively utilizes existing equipment, avoids resource waste, and saves costs.

[0070] According to the present invention, preferably, the residual raw material separation tower comes from the decarbonization tower 4 in the methyl tert-butyl ether unit.

[0071] According to the present invention, preferably, the regulator separation tower is derived from the methanol recovery tower in the methyl tert-butyl ether unit.

[0072] A second aspect of the present invention provides a system for selective chelation reaction of C4 olefins, the system comprising: a chelation reaction unit B and a product separation unit C;

[0073] The superposition reaction unit B includes a superposition reactor 11, which is used to carry out a superposition reaction of C4 olefins.

[0074] The product separation unit C includes a residual raw material separation tower 12 and a regulator recovery tower 13. 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 and superposition products is obtained at the bottom of the tower.

[0075] 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 is obtained as a composite product.

[0076] The outlet of the regulator recovery tower 13 is connected to the feed inlet of the superimposed reactor 11; or, the outlet of the regulator recovery tower 13 is connected to the feed inlet of the residual raw material separation tower 12 and the feed inlet of the superimposed reactor 11.

[0077] Preferably, the top outlet of the regulator recovery tower 13 is connected to the feed inlet of the superimposed reactor 11. This preferred embodiment is used to recover and reuse the reaction regulator and the separation regulator together.

[0078] 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. This preferred embodiment is used to separately recover and reuse the reaction regulator and the separation regulator.

[0079] 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.

[0080] In the system provided by this invention, entirely new equipment can be used as the separation unit C (residual feed separation tower 12 and regulator separation tower 13), or the separation equipment of the methyl tert-butyl ether unit can be reused as the separation unit C of this invention. The latter can effectively utilize existing equipment, avoid resource waste, and save costs.

[0081] According to the present invention, preferably, the residual raw material separation tower 12 comes from the decarbonization tower 4 in the methyl tert-butyl ether unit.

[0082] According to the present invention, preferably, the regulator recovery tower 13 is derived from the methanol recovery tower in the methyl tert-butyl ether unit.

[0083] 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.

[0084] According to the present invention, preferably, the raw material pretreatment unit A includes a water washing tower 10 and / or a purification tower.

[0085] 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 the 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, and 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 residue 5 at the outlet of the superposition reactor is introduced into the residual feedstock in the product separation unit C. The top stream of the residual raw material separation tower 12 is the second residual raw material 7, and the bottom stream (the first residual raw material, namely the separation regulator 6, the reaction regulator 8, and the superposition product 9) is introduced into the regulator recovery tower 13 in the product separation unit C. The top stream of the regulator recovery tower 13 is a mixture stream containing the reaction regulator 8 and the separation regulator 6. This mixture stream 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 of the regulator recovery tower 13 is the superposition product 9.

[0086] 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; the bottom stream of the regulator recovery tower 13 is the superposition product 9. For example, refer to... Figure 2 .

[0087] According to a specific embodiment of the present invention, such as Figure 2 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, 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, a selective superposition reaction of isobutylene mainly occurs. The superposition reaction residue 5 from the superposition reactor outlet is introduced into the residual feedstock separation tower 12 in product separation unit C. Simultaneously, a separation regulator 6 is introduced from the outside into the residual feedstock separation tower 12. The top stream of column 12 is the second residual raw material 7, and the bottom stream (separation regulator 6, reaction regulator 8, and superposition product 9) is introduced into the regulator recovery column 13 in the product separation unit C. The top stream of regulator recovery column 13 is the 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 column 12. The reaction regulator 8 is collected from the side stream outlet of regulator recovery column 13. 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 of regulator recovery column 13 is the superposition product 9.

[0088] 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; the bottom stream of the regulator recovery tower 13 is the superposition product 9. For example, refer to... Figure 1 .

[0089] In this invention, the terms "first" and "second" 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.

[0090] The present invention will be described in detail below through embodiments.

[0091] The composite catalyst is a commercially available product from Kerry Environmental Protection Technology Co., Ltd., with the brand name KC110.

[0092] Example 1

[0093] use Figure 1 The method for selective stoichiometry of C4 olefins is shown. The feedstock is C4 feedstock from a refinery, and its mass composition is shown in Table 1. The stoichiometric catalyst used is a sulfonic acid-type ion exchange resin catalyst. The reaction regulator is tert-butanol, used at 2% of the C4 feedstock mass flow rate. The stoichiometric reactor is a fixed-bed reactor. The obtained stoichiometric product is a C7-C12 olefin fraction with isooctene as the main component. The separation regulator is the first residual feedstock, whose mass composition is shown in Table 3, used at 5% of the stoichiometric product mass flow rate. The composition of the second residual feedstock is shown in Table 1, and the main operating conditions of the product separation unit fractionation column are shown in Table 2.

[0094] Example 2

[0095] 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 resulting synthesized product is a C7-C12 olefin fraction with isooctene as the main component. The separation regulator is externally added reformate topping oil, with its mass composition shown in Table 3, used at 7% of the mass flow rate of the synthesized product. The composition of the second residual feedstock is shown in Table 1, and the main operating conditions of the product separation unit fractionation tower are shown in Table 2.

[0096] Comparative Example 1

[0097] The method is carried out according to Example 1, 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 and superposition product 9) 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 is the superposition product 9.

[0098] 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.

[0099] Table 1

[0100]

[0101] Table 2

[0102]

[0103] Table 3

[0104]

[0105] As can be seen from Tables 1 and 2, the superposition method provided by this invention, under similar separation accuracy of the residual raw material separation tower, significantly reduces the energy consumption of the product separation unit compared with not introducing a separation regulator, resulting in significant energy-saving effect.

[0106] Compared with Comparative Example 1, under the condition that the separation accuracy of the residual raw material separation tower is the same, the total energy consumption of the product separation unit of Example 1 is reduced by about 32%, and the energy saving effect is obvious.

[0107] In Examples 1-2, the reboiler temperatures of the residual feed separation columns are relatively low, allowing readily available low-temperature heat sources to be used as the heat source for the reboiler. However, in Comparative Example 1, the reboiler temperature of the residual feed separation column is 172°C, making it difficult for the low-temperature heat source to meet the temperature requirements of the reboiler. A higher-temperature heat source is needed for the reboiler.

[0108] The bottom temperature of the residual feed separation tower in Examples 1-2 is relatively low, close to the bottom temperature of the fourth decarbonization tower in a conventional MTBE unit, but lower than the design temperature (≤165℃) of the fourth decarbonization tower in a conventional MTBE unit. Therefore, the fourth decarbonization tower and methanol recovery tower of the MTBE unit can be reused as the residual feed separation tower and regulator recovery tower of this invention, respectively, avoiding resource waste and saving costs. In contrast, the bottom temperature of the residual feed separation tower in Comparative Example 1 is higher than the bottom temperature of the fourth decarbonization tower in a conventional MTBE unit, and also higher than the design temperature of the fourth decarbonization tower in a conventional MTBE unit. Therefore, the fourth decarbonization tower and methanol recovery tower of the MTBE unit cannot be reused.

[0109] 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 selective superposition of 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 from the superposition reaction in step (1) is separated to obtain the remaining raw material, the reaction regulator, the separation regulator and the superposition product; the separation regulator contains at least one of cis-2-butene, trans-2-butene and isopentane; Among them, based on the total mass of the separation regulator, the total mass content of cis-2-butene, trans-2-butene, and isopentane is above 70%; The separation regulator is selected from light naphtha and / or at least a portion of the remaining raw materials; The amount of the separation regulator is 2-10% of the mass flow rate of the composite product.

2. The overlapping method according to claim 1, wherein, The distillation range of the light naphtha is 5-80℃.

3. The overlapping method according to claim 1, wherein, The separation regulator is added in step (1) and / or in step (2).

4. The overlapping method according to any one of claims 1-3, wherein, The separation in step (2) includes a first separation and a second separation. The first separation is carried out in a residual raw material separation tower. The bottom of the residual raw material separation tower yields a bottom material containing a separation regulator, a reaction regulator, and a superposition product. The top of the residual raw material separation tower yields a second residual raw material. The bottom material of the remaining raw material separation tower is introduced into the regulator recovery tower for a second separation. The bottom of the tower yields a composite product, and the top of the tower yields a top material containing separation regulator and reaction regulator.

5. The overlapping method according to claim 4, wherein, The top material of the regulator recovery tower provides at least a portion of the separation regulator and / or at least a portion of the reaction regulator.

6. The overlapping method according to claim 4, wherein, The reaction regulator and separation regulator are returned to step (1) and mixed with the C4 feedstock; Alternatively, the reaction regulator returns to step (1) and is mixed with the C4 feedstock, and the separation regulator returns to step (2) and is mixed with the material obtained from the superposition reaction.

7. The overlapping method according to claim 1, wherein, The superposition product is a C7-C12 olefin.

8. The overlapping method according to claim 7, wherein, The superposition product is isooctene.

9. The overlapping method according to claim 4, wherein, The conditions for the first and second separations are independent of each other: the top temperature of the column is 20-200℃, the bottom temperature of the column is 20-200℃, the top pressure of the column is 0-1MPaG, and the reflux ratio is 0.1-25.

10. The overlapping method according to claim 9, wherein, The conditions for the first separation are: top temperature of 40-70℃, bottom temperature of 120-165℃, top pressure of 0.3-0.7MPaG, and reflux ratio of 0.2-0.

6. The conditions for the second separation are: top temperature of 50-120℃, bottom temperature of 120-160℃, top pressure of 0-0.3MPaG, and reflux ratio of 2-20.

11. The overlapping method according to claim 4, wherein, The proportion of reaction regulator in the second remaining raw material is less than 500 ppm.

12. The overlapping method according to claim 11, wherein, The proportion of reaction regulator in the second remaining raw material is less than 50 ppm.

13. The overlapping method according to claim 4, wherein, The remaining raw material separation tower comes from the decarbonization tower four in the methyl tert-butyl ether unit; The regulator recovery tower is derived from the methanol recovery tower in the methyl tert-butyl ether unit.

14. The overlapping method according to any one of claims 1-3, 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; The reaction regulator is selected from at least one of tert-butanol, water, methyl tert-butyl ether, and methanol.

15. The overlapping method according to claim 14, wherein, The reaction regulator is tert-butanol.

16. The overlapping method according to any one of claims 1-3, wherein, The C4 feedstock is a catalytically cracked C4 fraction and / or an ethylene cracked C4 fraction.

17. The overlapping method according to any one of claims 1-3, wherein, The amount of the reaction regulator used is 0.1-5% of the mass flow rate of the C4 feedstock.

18. The overlapping method according to claim 14, wherein, The catalyst is a sulfonic acid type ion exchange resin catalyst.

19. The overlapping method according to any one of claims 1-3, wherein, The superposition reaction is carried out in a superposition reactor, which is selected from a fixed-bed reactor, a bubble-point reactor, or a tubular reactor.

20. The overlapping method according to any one of claims 1-3, wherein, Before the C4 raw material undergoes the superposition reaction, it is pretreated. The pretreatment includes water washing and / or purification agent treatment; The pretreatment also includes selective hydrogenation.

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