Method and device for preparing 4-methyl-1-pentene through propylene dimerization

Abstract

The invention relates to the technical field of propylene dimerization, in particular to a method and device for preparing 4-methyl-1-pentene through propylene dimerization, and the method comprises the following steps: (1) dehydrating and deoxidizing a raw material containing propylene, a coking inhibitor and a diluent to obtain a treated raw material; (2) contacting the treated raw material with a catalyst, carrying out dimerization reaction to obtain a reaction material, carrying out heat treatment on part of the reaction material, returning, and carrying out the dimerization reaction; (3) carrying out rectification separation on the rest reaction material to obtain a light component, 4-methyl-1-pentene and a heavy component; wherein the total temperature rise delta T of the dimerization reaction is regulated and controlled through the mass ratio of the diluent to the propylene in the raw materials and the recycle ratio of the reaction materials, and the recycle ratio of the reaction materials is the mass ratio of the part of the reaction materials to the propylene in the raw materials. According to the method, the selectivity of the 4-methyl-1-pentene is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of propylene dimerization, and in particular to a method for preparing 4-methyl-1-pentene by propylene dimerization and a device for preparing 4-methyl-1-pentene by propylene dimerization. Background Art

[0002] 4-Methyl-1-pentene is an important polymerization monomer that can be used as a copolymer of ethylene and propylene. It can improve the transparency and environmental stress resistance of polyolefins. It can also be homopolymerized into thermoplastics to prepare poly-4-methyl-1-pentene (PMP) with excellent performance.

[0003] The preparation of 4-methyl-1-pentene mainly includes three main synthetic routes: halogenated hydrocarbon coupling, pentanol dehydration and propylene dimerization. Among them, the process route of preparing 4-methyl-1-pentene by propylene dimerization using alkali metal as catalyst has good economic efficiency and has been industrialized abroad. In China, many scientific research institutes and universities have also carried out experimental research on the preparation of 4-methyl-1-pentene by propylene dimerization, but it has not yet been industrialized.

[0004] On the one hand, under the reaction conditions of propylene dimerization to prepare 4-methyl-1-pentene, in addition to the dimerization reaction, a polymerization reaction is also likely to occur to generate a polymer product. The generation of the polymer product not only reduces the selectivity of 4-methyl-1-pentene, but also reduces the activity of the catalyst and shortens its life. Therefore, how to accurately control the degree of polymerization or dimerization selectivity is the key to this technology. Usually, when the catalyst activity is reduced to a certain extent, the catalyst is partially regenerated by online regeneration, but this method cannot extend the catalyst's one-way life.

[0005] On the other hand, the preparation of 4-methyl-1-pentene by propylene dimerization is an exothermic reaction with a large heat release, and the reaction temperature is difficult to control, and the conversion rate and selectivity are sensitive to the reaction temperature. Therefore, it is necessary to remove the reaction heat in time to maintain a stable reaction temperature, reduce the occurrence of side reactions, and improve the selectivity of the target product. When the conversion rate is low, the heat release is also low. CN202010495971.3 discloses a synthesis process of 4-methyl-1-pentene, in which propylene is added to a reaction unit through dehydration and deoxygenation to carry out dimerization and isomerization reactions, and then the unreacted raw materials are returned to the reaction unit for circulation after gas-liquid separation. However, this process method, when the catalyst activity is good, the reaction conversion rate and reaction temperature are difficult to control, and the unreacted raw materials have the risk of continuing to react, thereby increasing the heat release, and the excess heat cannot be removed in time, so that the reaction temperature deviates from the normal temperature, affecting the selectivity of the target product. Moreover, a large amount of unreacted raw materials have a high energy consumption through distillation separation circulation.

[0006] In addition, the alkali metal catalyst used has extremely high requirements for water and oxygen content. Once the catalyst powder is blocked along with the material to the downstream, there is a risk of fire when the device encounters air during disassembly. Summary of the invention

[0007] The purpose of the present invention is to overcome the above technical problems and provide a method and device for preparing 4-methyl-1-pentene by propylene dimerization. The method adjusts the mass ratio of the diluent and propylene in the raw material and the circulation ratio of the reaction materials, thereby adjusting the total temperature rise of the dimerization reaction, thereby facilitating the selectivity of 4-methyl-1-pentene; at the same time, the method reduces the energy consumption of distillation separation and increases the operational flexibility.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for preparing 4-methyl-1-pentene by dimerization of propylene, the method comprising:

[0009] (1) subjecting a raw material containing propylene, a coking inhibitor and a diluent to dehydration and deoxygenation treatment to obtain a treated raw material; (2) contacting the treated raw material with a catalyst and performing a dimerization reaction to obtain a reaction material, and returning a portion of the reaction material after heat removal treatment to perform the dimerization reaction; (3) subjecting the remaining portion of the reaction material to distillation separation to obtain a light component, 4-methyl-1-pentene and a heavy component;

[0010] The total temperature rise ΔT of the dimerization reaction is regulated by the mass ratio of the diluent to propylene in the raw material and the circulation ratio of the reaction material, and the circulation ratio of the reaction material is the mass ratio of the part of the reaction material to the propylene in the raw material.

[0011] Preferably, the total temperature rise ΔT of the dimerization reaction is ≤60°C, preferably ≤30°C.

[0012] Preferably, the mass ratio of the diluent to propylene in the raw material is 0.1-200:1, preferably 1-80:1.

[0013] And / or, the circulation ratio of the reaction materials is 0.1-200:1, preferably 1-80:1.

[0014] The second aspect of the present invention provides a device for preparing 4-methyl-1-pentene by dimerization of propylene, the device comprising: a pretreatment unit, a reaction unit and a distillation separation unit connected in sequence;

[0015] The pretreatment unit is used to dehydrate and deoxygenate the raw material containing propylene, coking inhibitor and diluent to obtain treated raw material; the reaction unit is selected from at least one reactor connected in series with an external circulation heat extraction component, and is used to contact the treated raw material with a catalyst and perform a dimerization reaction to obtain a reaction material, and return part of the reaction material to the reactor after heat extraction treatment; the distillation and separation unit is used to distill and separate the remaining part of the reaction material to obtain 4-methyl-1-pentene.

[0016] Through the above technical scheme, the method provided by the present invention, by adding a coking inhibitor and a diluent to the raw material, and limiting the total temperature rise ΔT of the dimerization reaction by regulating the mass ratio of the diluent to propylene in the raw material and the circulation ratio of the reaction materials, especially limiting the total temperature rise ΔT of the dimerization reaction to satisfy formulas (I-1) and (I-2), avoids defects such as polymerization, catalyst coking, and difficulty in controlling the reaction temperature, thereby effectively improving the selectivity of 4-methyl-1-pentene; at the same time, the method recycles part of the reaction materials, reduces the energy consumption of distillation separation, increases the flexibility of operation, and facilitates industrial production.

[0017] The method provided by the present invention is also limited to filtering the catalyst fine powder remaining in the reaction material before distillation separation (for example, first filtration, second filtration), thereby avoiding the risk of active catalyst catching fire when contacting water and air when subsequent pipelines and pipes are blocked by catalysts and are disassembled and flushed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention provides a schematic diagram of the structure of a first device for preparing 4-methyl-1-pentene by propylene dimerization.

[0019] Figure 2 The present invention provides a second device structure schematic diagram for preparing 4-methyl-1-pentene by propylene dimerization.

[0020] Figure 3 The present invention provides a third device structure schematic diagram for preparing 4-methyl-1-pentene by propylene dimerization.

[0021] Description of Reference Numerals

[0022] I, pretreatment unit; II, reaction unit; II-1, first reactor; II-2, first reactor; III, distillation separation unit; III-1, first distillation separation tower; III-2, second distillation separation tower; III-3, third distillation separation tower; IV, cooler; V, pump; VI, heater; VI-1, heater 1; VI-2, heater 2; 01, first filter component; 01-i, first filter component 1; 01-ii, first filter component 2; 02, second filter component; 03, circulation pipeline; 03-1, circulation pipeline 1; 03-2, circulation pipeline 2;

[0023] 1. Propylene; 2. Coking inhibitor; 3. Diluent; 4. Raw materials; 5. Treated raw materials; 6. Reaction materials; 6-i. Part of the reaction materials; 6-ii. The remaining reaction materials; 7. Take the heat-treated materials; 7-i. Take the heat-treated material 1; 7-ii. Take the heat-treated material 2; 8. Light components; 9. The first mixed material; 10. Light impurities; 11. The second mixed material; 12. 4-methyl-1-pentene; 13. Heavy components; 14. The outlet material of the first reactor. DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] In the present invention, unless otherwise specified, "first" and "second" do not indicate a sequence or limit the materials or steps, but are only used to indicate that they are not the same material or step. For example, "first" and "second" in "first filtration" and "second filtration" are only used to indicate that they are not the same filtration.

[0026] In the present invention, unless otherwise specified, the "top" of a container refers to the position of 0-10% from top to bottom of the container; the "upper part" of a container refers to the position of 10-40% from top to bottom of the container; the "middle part" of a container refers to the position of 40-60% from top to bottom of the container; the "lower part" of a container refers to the position of 60-90% from top to bottom of the container; and the "bottom" of a container refers to the position of 90-100% from top to bottom of the container.

[0027] The first aspect of the present invention provides a method for preparing 4-methyl-1-pentene by dimerization of propylene, the method comprising:

[0028] (1) subjecting a raw material containing propylene, a coking inhibitor and a diluent to a dehydration and deoxygenation treatment to obtain a treated raw material;

[0029] (2) contacting the treated raw material with a catalyst and performing a dimerization reaction to obtain a reaction material, and returning a portion of the reaction material after heat removal to perform the dimerization reaction;

[0030] (3) subjecting the remaining reaction materials to distillation separation to obtain light components, 4-methyl-1-pentene and heavy components;

[0031] The total temperature rise ΔT of the dimerization reaction is regulated by the mass ratio of the diluent to propylene in the raw material and the circulation ratio of the reaction material, and the circulation ratio of the reaction material is the mass ratio of the part of the reaction material to the propylene in the raw material.

[0032] The inventors of the present invention have found through research that: adding a coking inhibitor to the raw material can inhibit the occurrence of polymerization reaction and prevent the catalyst from coking, thereby improving the selectivity of 4-methyl-1-pentene and extending the life of the catalyst; adding a diluent to the raw material can reduce the concentration of propylene in the raw material, avoid the uncontrollable propylene conversion rate and heat release when pure propylene is used as the raw material, and prevent the bed from overheating; at the same time, a reaction material circulation heat extraction is set, specifically by adjusting the mass ratio of the diluent to propylene in the raw material and the circulation ratio of the reaction material, and then adjusting the temperature rise of the dimerization reaction, thereby well controlling the selectivity of 4-methyl-1-pentene.

[0033] At the same time, the method removes the residual catalyst in the reaction materials before distillation separation, thereby avoiding the risk of active catalyst catching fire when encountering water and air when subsequent pipelines and pipes are blocked by the catalyst and are disassembled and flushed.

[0034] In the present invention, unless otherwise specified, the reaction material is divided into a partial reaction material and a remaining partial reaction material.

[0035] In some embodiments of the present invention, preferably, the dimerization reaction is carried out in at least one reactor connected in series, and the reactor is equipped with an external circulation heat extraction component; further preferably, the number of the reactors is 1-6, preferably 1-4, and more preferably 2-4.

[0036] In some embodiments of the present invention, preferably, at least one catalyst bed is stacked in the reactor, preferably 1-6 catalyst beds are stacked, and more preferably 1-3 catalyst beds are stacked.

[0037] In a first specific embodiment of the present invention, Figure 1 As shown, the dimerization reaction is carried out in a fixed bed reactor with an external circulation heat extraction component, and a catalyst bed is arranged in the fixed bed reactor.

[0038] In a second specific embodiment of the present invention, Figure 2 As shown, the dimerization reaction is carried out in a fixed bed reactor with an external circulation heat extraction component, and two catalyst beds are stacked in the fixed bed reactor.

[0039] In a third specific embodiment of the present invention, Figure 3 As shown, the dimerization reaction is carried out in two fixed bed reactors connected in series with heat extraction components, and a catalyst bed layer is stacked in each fixed bed reactor.

[0040] In some embodiments of the present invention, preferably, the total temperature rise ΔT of the dimerization reaction satisfies:

[0041]

[0042]

[0043] Wherein, ΔT is the total temperature rise of the dimerization reaction, °C; ΔT i is the temperature rise of the ith catalyst bed, °C; n is the total number of catalyst beds, and is selected from a natural number, wherein the counting rule of the catalyst beds is selected from the material flow direction, starting from the upstream catalyst bed stacked in the first reactor in series, and counting sequentially to the downstream catalyst bed stacked in the last reactor; K i is the average reaction heat of the ith catalyst bed, kJ / kg; X i is the propylene conversion rate of the i-th catalyst bed; R0 is the mass ratio of the diluent to propylene in the raw material; R 1i is the mass ratio of the material returned to the i-th catalyst bed to the propylene in the feedstock; C Pi is the specific heat of the material in the ith catalyst bed, kJ / (kg·℃);.

[0044] In the present invention, unless otherwise specified, the total number n of catalyst beds is the sum of the number of catalyst beds in at least one reactor connected in series according to the direction of material flow.

[0045] In the present invention, unless otherwise specified, the number of reactors connected in series may be one or more; the number of catalyst beds stacked in each reactor may be one or more.

[0046] In the present invention, the first catalyst bed refers to the most upstream catalyst bed stacked in the first reactor connected in series according to the material flow direction; similarly, the i-th catalyst bed refers to the i-th catalyst bed counted from the most upstream catalyst bed stacked in the first reactor connected in series according to the material flow direction.

[0047] In a specific embodiment of the present invention, Figure 2 As shown, according to the material flow direction, the two catalyst beds stacked in the reactor are counted as the first catalyst bed and the second catalyst bed respectively.

[0048] In a specific embodiment of the present invention, Figure 3 As shown, according to the material flow direction, the catalyst beds in the two series-connected reactors are counted as the first catalyst bed and the second catalyst bed respectively.

[0049] In some embodiments of the present invention, preferably, the total temperature rise ΔT of the dimerization reaction is ≤60°C, for example, 5°C, 6°C, 8°C, 10°C, 12°C, 15°C, 20°C, 25°C, 30°C, 40°C, 50°C, 60°C, and any value in the range of any two values, preferably ≤30°C. In the present invention, the total temperature rise of the dimerization reaction is the sum of the temperature rises of each catalyst bed.

[0050] In some embodiments of the present invention, preferably, the temperature rise of a single catalyst bed is ≤30° C., preferably ≤20° C. In the present invention, the temperature rise of a single catalyst bed is selected from the difference between the discharge temperature and the feed temperature of the single catalyst bed, ℃.

[0051] In a specific embodiment of the present invention, when the total number of catalyst beds is n=1, the total temperature rise ΔT of the dimerization reaction satisfies:

[0052]

[0053] In the present invention, when the total number of catalyst beds is n=1, Figure 1 As shown, the dimerization reaction is carried out in a single fixed bed reactor with an external circulation heat extraction part, and a catalyst bed layer is stacked in the fixed bed reactor.

[0054] In another specific embodiment of the present invention, when the total number of catalyst beds is n=2, the total temperature rise ΔT of the dimerization reaction satisfies:

[0055]

[0056] In the present invention, when the total number of catalyst beds is n=2, Figure 2 As shown, the dimerization reaction is carried out in a single fixed bed reactor with an external circulation heat extraction part, and two catalyst beds are stacked in the fixed bed reactor; or, as Figure 3 As shown, the dimerization reaction is carried out in two fixed bed reactors connected in series with an external circulation heat extraction component, and a catalyst bed layer is stacked in each fixed bed reactor.

[0057] In some embodiments of the present invention, preferably, the mass ratio of the diluent to propylene in the raw material is 0.1-200: 1, for example, 0.1: 1, 1: 1, 10: 1, 20: 1, 40: 1, 50: 1, 60: 1, 80: 1, 100: 1, 150: 1, 200: 1, and any value in the range consisting of any two values, preferably 1-80: 1. When the above mass ratio range is met, the selectivity of 4-methyl-1-pentene is improved by balancing the total temperature rise of the dimerization reaction.

[0058] In some embodiments of the present invention, preferably, the diluent is selected from alkanes and / or cycloalkanes, preferably selected from C2-C5 alkanes and / or C3-C6 cycloalkanes, more preferably selected from at least one of ethane, propane, n-butane, isobutane and n-pentane, and most preferably propane.

[0059] In some embodiments of the present invention, preferably, the purity of the propylene is ≥ 80 wt%, preferably ≥ 95 wt%.

[0060] In some embodiments of the present invention, preferably, the circulation ratio of the reaction material is 0.1-200: 1, for example, 0.1: 1, 1: 1, 10: 1, 15: 1, 20: 1, 30: 1, 50: 1, 60: 1, 80: 1, 100: 1, 150: 1, 200: 1, and any value in the range of any two values, preferably 1-80: 1. In the present invention, the circulation ratio meeting the above range is conducive to improving the selectivity of 4-methyl-1-pentene.

[0061] In some embodiments of the present invention, preferably, in the raw material calculated as propylene, the molar concentration of the coking inhibitor is 2-1000ppm, for example, 2ppm, 10ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 1000ppm, and any value in the range consisting of any two values, preferably 10-500ppm. The molar concentration ratio satisfying the above range can more effectively improve the selectivity of 4-methyl-1-pentene by inhibiting the occurrence of polymerization reaction and preventing catalyst coking.

[0062] In some embodiments of the present invention, preferably, the coking inhibitor is selected from hydrogen.

[0063] In some embodiments of the present invention, preferably, the water content in the treated raw material is ≤10ppm; the oxygen content is ≤10ppm; further preferably, the water content in the treated raw material is ≤3ppm; the oxygen content is ≤3ppm.

[0064] In the present invention, unless otherwise specified, before the dimerization reaction is carried out, a non-oxidizing gas (eg, nitrogen, etc.) is introduced to replace the air, and then the treated raw material is introduced to replace the non-oxidizing gas.

[0065] In some embodiments of the present invention, preferably, in step (2), the dimerization reaction conditions include: a temperature of 50-300° C., preferably 100-200° C.; and a pressure of 4-20 MPa, preferably 6-12 MPa. In the present invention, the pressures are all absolute pressures.

[0066] In the present invention, the type of the catalyst has a wide selection range. Preferably, the catalyst is selected from supported alkali metal catalysts, preferably supported Na / K catalysts.

[0067] In some embodiments of the present invention, preferably, based on the total weight of the supported alkali metal catalyst, the alkali metal loading is 0.1-20wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, 20wt%, and any value in the range consisting of any two values, preferably 1-10wt%.

[0068] In some embodiments of the present invention, preferably, in step (2), the temperature of the heat-treated material is 0-120° C. lower than the temperature of the treated raw material, for example, 0° C., 10° C., 20° C., 40° C., 60° C., 80° C., 100° C., 120° C., and any value in the range of any two values, preferably 0-100° C. Meeting the above range is more conducive to regulating the total temperature rise of the dimerization reaction, thereby improving the selectivity of 4-methyl-1-pentene.

[0069] In some embodiments of the present invention, preferably, the heat removal process comprises: cooling, pressurizing and heating the part of the reaction material in sequence to obtain a heat-treated material.

[0070] In some embodiments of the present invention, when the total number of catalyst beds n=1, part of the reaction materials are sequentially cooled, pressurized and heated, and returned to the catalyst bed; or, when the total number of catalyst beds n≠1, part of the reaction materials are sequentially cooled and pressurized, and the pressurized logistics obtained are divided into n streams, which are respectively heated and returned to the i-th catalyst bed.

[0071] In a specific embodiment of the present invention, when the total number of catalyst beds n=1, Figure 1 As shown, the part of the reaction material is cooled, pressurized and heated in sequence and then returned to the first catalyst bed.

[0072] In a specific embodiment of the present invention, when the total number of catalyst beds n=2, as Figure 2-3 As shown, the part of the reaction material is cooled and pressurized in sequence, and the pressurized logistics obtained are divided into two streams, which are heated separately and then returned to the first catalyst bed and the second catalyst bed respectively.

[0073] In some embodiments of the present invention, preferably, the temperature of the material after cooling is 40-150°C, preferably 40-100°C; preferably, the pressure of the material after pressurization is 4-20MPa, preferably 6-12MPa; preferably, the temperature of the material after heating is 50-200°C, preferably 55-160°C.

[0074] In some embodiments of the present invention, preferably, in step (3), the distillation separation process includes: a first distillation separation, a second distillation separation and a third distillation separation; wherein the first distillation separation process includes: subjecting the remaining part of the reaction material to the first distillation separation to obtain a light component and a first mixed material; the second distillation separation process includes: subjecting the first mixed material to the second distillation separation to obtain light impurities and a second mixed material; the third distillation separation process includes: subjecting the second mixed material to the third distillation separation to obtain 4-methyl-1-pentene and a heavy component.

[0075] In the present invention, unless otherwise specified, the light component is selected from a stream rich in diluent and unreacted propylene; the light impurities are a small amount of diluent, unreacted propylene and a small amount of 4-methyl-1-pentene; the heavy component is selected from a stream rich in dimer isomers (e.g., 1-hexene) and polymer reaction products (e.g., C 9+ ) logistics.

[0076] In some embodiments of the present invention, preferably, the conditions for the first distillation separation include: the top pressure is 1-3MPa, preferably 1.5-2MPa; the conditions for the second distillation separation include: the top pressure is 0.2-1MPa, preferably 0.5-1MPa; the conditions for the third distillation separation include: the top pressure is 0.2-0.8MPa, preferably 0.2-0.5MPa.

[0077] In some embodiments of the present invention, preferably, the light component is returned and mixed into the raw material. The main purpose of such arrangement is to reduce the amount of fresh material used and reduce production costs. In the present invention, the diluent in the raw material can come from fresh diluent or from the light component obtained from the first distillation; it can also contain both fresh diluent and the light component obtained from the first distillation separation.

[0078] In the present invention, in order to avoid the blockage of catalyst fine powder in the downstream process and the risk of fire when the device is disassembled and encounters water and air, preferably, the method further comprises: subjecting the dimerization reaction material to a first filtration to obtain the reaction material, and dividing the obtained reaction material into the partial reaction material and the remaining partial reaction material.

[0079] In some embodiments of the present invention, preferably, the method further comprises: subjecting the remaining portion of the reaction material to the distillation separation after a second filtration.

[0080] The second aspect of the present invention provides a schematic diagram of the structure of a device for preparing 4-methyl-1-pentene by propylene dimerization, as shown in Figure 1-3 As shown, the device comprises: a pretreatment unit I, a reaction unit II and a distillation separation unit III connected in sequence;

[0081] The pretreatment unit I is used to dehydrate and deoxygenate a raw material 4 containing propylene 1, a coking inhibitor 2 and a diluent 3 to obtain a treated raw material 5; the reaction unit II is selected from at least one reactor connected in series with an external circulation heat extraction component, and is used to contact the treated raw material 5 with a catalyst and perform a dimerization reaction to obtain a reaction material 6, and return part of the reaction material 6-i to the reaction unit II after heat extraction treatment; the distillation and separation unit III is used to distill and separate the remaining part of the reaction material 6-ii to obtain 4-methyl-1-pentene 12.

[0082] In the present invention, preferably, Figure 1 As shown, a heat extraction component is provided on the circulation pipeline 03 connected to the reactor; further preferably, according to the material flow direction, the heat extraction component includes a cooler IV, a pump V and a heater VI connected in sequence, which are respectively used to cool, pressurize and heat the part of the reaction material 6-i in sequence to obtain the material 7 after heat treatment.

[0083] In the present invention, the reactor includes but is not limited to a fixed bed reactor.

[0084] In the present invention, preferably, the reactor contains at least one catalyst bed layer arranged in layers, preferably contains 1 to 6 catalyst beds, and more preferably contains 1 to 3 catalyst beds.

[0085] In a specific embodiment of the present invention, Figure 1 As shown, the reaction unit II is selected from a fixed bed reactor with an external circulation heat extraction component, and a catalyst bed is arranged in the fixed bed reactor; according to the material flow direction, a cooler IV, a pump V and a heater VI are arranged in sequence on the circulation pipeline 03 connected to the fixed bed reactor, which are used to cool, pressurize and heat part of the reaction material 6-i in sequence, and the obtained heat-treated material 7 is returned to the catalyst bed.

[0086] In another specific embodiment of the present invention, Figure 2 As shown, the reaction unit II is selected from a fixed bed reactor with an external circulation heat extraction component, and two catalyst beds are arranged in the fixed bed reactor; according to the material flow direction, a cooler IV and a pump V are arranged on the pipeline connecting the fixed bed reactor, and a heater VI-1 is arranged on the circulation pipeline 03-1, and a heater VI-2 is arranged on the circulation pipeline 03-2, which are used to cool and pressurize part of the reaction material 6-i in turn, and the pressurized material obtained is divided into two streams for heating respectively, and the obtained heat-treated material 7-i and the heat-treated material 7-ii are returned to the first catalyst bed and the second catalyst bed respectively.

[0087] In another specific embodiment of the present invention, Figure 3 As shown, the reaction unit II is selected from two fixed bed reactors connected in series with external circulation heat extraction components, and a catalyst bed is arranged in each fixed bed reactor; according to the material flow direction, a cooler IV and a pump V are arranged on the pipeline connecting the second fixed bed reactor, and a heater VI-1 is arranged on the circulation pipeline 03-1, and a heater VI-2 is arranged on the circulation pipeline 03-2, which are used to cool and pressurize part of the reaction material 6-i in turn, and the pressurized material obtained is divided into two streams for heating respectively, and the obtained heat-treated material 7-i and the heat-treated material 7-ii are returned to the first catalyst bed in the first reactor II-1 and the second catalyst bed in the second reactor II-2 respectively.

[0088] In the present invention, preferably, Figure 1 As shown, the device also includes: a first filtering component 01 and / or a second filtering component 02; the first filtering component 01 is arranged at the bottom of the reaction unit II, and is used to obtain the reaction material 6 after the material of the dimerization reaction is filtered for the first time; the second filtering component 02 is connected to the reaction unit II and the distillation and separation unit III, and is used to perform the distillation and separation on the remaining part of the reaction material 6-ii after the second filtration.

[0089] In the present invention, the first filter component 01 and the second filter component 02 are each independently selected from a mesh and / or membrane with a filtering accuracy of ≤15 μm, including but not limited to a metal mesh, a sintered metal powder, a ceramic membrane, and a polyester filter element.

[0090] In the present invention, preferably, Figure 1-2As shown, the distillation separation unit III includes: a first distillation separation tower III-1, a second distillation separation tower III-2 and a third distillation separation tower III-3 which are connected in sequence; the first distillation separation tower III-1 is used to perform a first distillation separation on the remaining part of the reactant 6-ii, and a light component 8 is obtained at the top of the tower, and a first mixed material 9 is obtained at the bottom of the tower; the second distillation separation tower III-2 is used to perform a second distillation separation on the first mixed material 9, and a light impurity 10 is obtained at the top of the tower, and a second mixed material 11 is obtained at the bottom of the tower; the third distillation separation tower III-3 is used to perform a third distillation separation on the second mixed material 11, and 4-methyl-1-pentene 12 is obtained at the top of the tower, and a heavy component 13 is obtained at the bottom of the tower.

[0091] In the present invention, preferably, Figure 1 As shown, the top of the first distillation separation tower III-1 is connected to the pretreatment unit I for returning the light component 8 and performing the dehydration and deoxygenation treatment.

[0092] According to a particularly preferred embodiment of the present invention, a method for preparing 4-methyl-1-pentene by dimerization of propylene comprises:

[0093] (1) subjecting a raw material containing propylene, a coking inhibitor and a diluent to dehydration and deoxygenation treatment to obtain a treated raw material; (2) contacting the treated raw material with a catalyst and performing a dimerization reaction to obtain a reaction material, and returning a portion of the reaction material after heat removal treatment to perform the dimerization reaction; (3) subjecting the remaining portion of the reaction material to distillation separation to obtain a light component, 4-methyl-1-pentene and a heavy component;

[0094] The total temperature rise ΔT of the dimerization reaction is regulated by the mass ratio of the diluent to propylene in the raw material and the circulation ratio of the reaction material, and the circulation ratio of the reaction material is the mass ratio of the part of the reaction material to the propylene in the raw material;

[0095] The mass ratio of the diluent to propylene in the raw material is 1-80:1; the circulation ratio of the reaction material is 1-80:1; the molar concentration of the coking inhibitor in the raw material calculated as propylene is 10-500 ppm; and the coking inhibitor is selected from hydrogen.

[0096] The present invention will be described in detail below through examples.

[0097] The catalysts of the examples and comparative examples are supported Na / K catalysts, and the Na / K loading is 6 wt %;

[0098] Some process parameters and test results of Examples 1-10 and Comparative Examples 1-3 are listed in Table 1.

[0099] Example 1

[0100] The device for preparing 4-methyl-1-pentene by propylene dimerization is as follows: Figure 1 As shown by Figure 1 It can be seen that the device includes: a pretreatment unit I, a reaction unit II and a distillation separation unit III connected in sequence; the reaction unit II is selected from a fixed bed reactor with an external circulation heat extraction component, and a single catalyst bed is arranged in the fixed bed reactor; according to the material flow direction, a cooler IV, a pump V and a heater VI are arranged in sequence on the circulation pipeline 03 connected to the fixed bed reactor; a first filtering component 01 is arranged at the bottom of the fixed bed reactor, and a second filtering component 02 is arranged on the connecting pipeline between the fixed bed reactor and the distillation separation unit;

[0101] The first filter component 01 and the second filter component 02 are both selected from metal filter meshes with a filtering accuracy of 10 μm.

[0102] The method for preparing 4-methyl-1-pentene by propylene dimerization is carried out in the above-mentioned device, and the method comprises:

[0103] (1) subjecting a raw material containing propylene, propane and hydrogen to a dehydration and deoxygenation treatment to obtain a treated raw material; the purity of the propylene is 95 wt %, the mass ratio of propane to propylene in the raw material is 10:1; the molar concentration of the hydrogen in the raw material calculated on the basis of propylene is 60 ppm; the water content and oxygen content of the treated raw material are 2.3 ppm and 2.7 ppm respectively;

[0104] (2) replacing the air in the reaction unit with nitrogen, and then replacing the nitrogen with the treated raw material, contacting the treated raw material with the catalyst and performing a dimerization reaction (temperature of 150° C., pressure of 10 MPa), and filtering the obtained dimerization reaction material to obtain a reaction material, and cooling part of the reaction material to 40° C., pressurizing to 10 MPa, and heating to 150° C. in sequence, and returning the obtained heat-treated material to the catalyst bed inlet;

[0105] The mass ratio of the above-mentioned partial reaction materials to the propylene in the raw material is 10:1;

[0106] (3) The remaining reaction material is subjected to a second filtration, and the filtered material is subjected to a first distillation separation (the tower top pressure is 1.8 MPa). The light component obtained at the tower top is returned and mixed with the above raw materials. The first mixed material obtained at the tower bottom is subjected to a second distillation separation (the tower top pressure is 0.8 MPa). The second mixed material obtained at the tower bottom is subjected to a second distillation separation (the tower top pressure is 0.3 MPa), and 4-methyl-1-pentene is obtained at the tower top.

[0107] Example 2

[0108] According to the device of embodiment 1;

[0109] According to the method of Example 1, the difference is that in step (1),

[0110] The molar concentration of hydrogen in the above raw material calculated on the basis of propylene was replaced with 200 ppm, and the other conditions were the same to obtain 4-methyl-1-pentene.

[0111] Example 3

[0112] According to the device of embodiment 1;

[0113] According to the method of Example 1, the difference is that in step (1),

[0114] The molar concentration of hydrogen in the above raw material calculated on the basis of propylene was replaced with 600 ppm, and the other conditions were the same to obtain 4-methyl-1-pentene.

[0115] Example 4

[0116] According to the device of embodiment 1;

[0117] According to the method of Example 1, the difference is that

[0118] In step (1), the mass ratio of propane to propylene in the above raw materials is replaced with 20:1;

[0119] In step (2), the circulation ratio of the reaction materials is replaced with 1:1, and the other conditions are the same to obtain 4-methyl-1-pentene.

[0120] Example 5

[0121] According to the device of embodiment 1;

[0122] According to the method of Example 1, the difference is that

[0123] In step (1), the mass ratio of propane to propylene in the above raw materials is replaced to 1:1;

[0124] In step (2), the circulation ratio of the reaction materials is replaced with 20:1, and the other conditions are the same to obtain 4-methyl-1-pentene.

[0125] Example 6

[0126] According to the device of embodiment 1;

[0127] According to the method of Example 1, the difference is that

[0128] In step (1), the mass ratio of propane to propylene in the above raw materials is replaced with 100:1;

[0129] In step (2), the circulation ratio of the reaction materials is replaced with 1:1, and the other conditions are the same to obtain 4-methyl-1-pentene.

[0130] Example 7

[0131] According to the device of embodiment 1;

[0132] According to the method of Example 1, the difference is that

[0133] In step (1), the mass ratio of propane to propylene in the above raw materials is replaced with 1:1;

[0134] In step (2), the circulation ratio of the reaction materials is replaced with 100:1, and the other conditions are the same to obtain 4-methyl-1-pentene.

[0135] Example 8

[0136] The device according to Example 1 is different in that:

[0137] like Figure 2 As shown, two catalyst beds are arranged in the fixed bed reactor, and the catalyst loading amount of the two catalyst beds is the same;

[0138] According to the material flow direction, a cooler IV and a pump V are sequentially arranged on the circulation pipe 03 connected to the fixed bed reactor. After the pump, the circulation pipe is divided into a circulation pipe 1 03-1 and a circulation pipe 2 03-2. A heater 1 VI-1 and a heater 2 VI-2 are respectively arranged on the circulation pipe 1 03-1 and the circulation pipe 2 03-2.

[0139] The method is carried out in the above-mentioned apparatus, except that

[0140] In step (2), the obtained dimerization reaction material is first filtered to obtain a reaction material, and part of the reaction material is sequentially cooled to 40° C. and pressurized to 10 MPa, and then divided into two streams, one of which is heated to 150° C. and returned to the inlet of the first catalyst bed, and the other is heated to 55° C. and returned to the inlet of the second catalyst bed;

[0141] The mass ratio of the material returned to the first catalyst bed to the propylene in the feedstock was 8:1; the mass ratio of the material returned to the second catalyst bed to the propylene in the feedstock was 2:1.

[0142] Example 9

[0143] The device according to Example 8;

[0144] The method of Example 8 is followed, except that

[0145] In step (2), one stream is heated to 150°C and then returned to the inlet of the first catalyst bed, and the other stream is heated to 112°C and then returned to the inlet of the second catalyst bed;

[0146] The mass ratio of the material returned to the first catalyst bed to the propylene in the feedstock is 5:1; the mass ratio of the material returned to the second catalyst bed to the propylene in the feedstock is 5:1.

[0147] Example 10

[0148] The device according to Example 8;

[0149] The method of Example 8 is followed, except that

[0150] In step (2), one stream is heated to 150°C and then returned to the inlet of the first catalyst bed, and the other stream is heated to 126°C and then returned to the inlet of the second catalyst bed;

[0151] The mass ratio of the material returned to the first catalyst bed to the propylene in the feedstock was 2:1; the mass ratio of the material returned to the second catalyst bed to the propylene in the feedstock was 8:1.

[0152] Comparative Example 1

[0153] According to the device of embodiment 1;

[0154] The method of Example 1 is followed, except that in step (1), no hydrogen is added, and the other conditions are the same to obtain 4-methyl-1-pentene.

[0155] Comparative Example 2

[0156] According to the device of embodiment 1;

[0157] The method of Example 1 is followed, except that in step (1), propane is not added, and the other conditions are the same to obtain 4-methyl-1-pentene.

[0158] Comparative Example 3

[0159] The apparatus according to Example 1, except that the reaction unit II is selected from a fixed bed reactor provided with a single catalyst bed;

[0160] The method of Example 1 is different from that in step (2), the reaction material is not subjected to a heat removal cycle, that is, the reaction material is directly subjected to step (3) to obtain 4-methyl-1-pentene.

[0161] Table 1

[0162]

[0163] Note: 1- molar concentration of coking inhibitor in the feedstock in terms of propylene, ppm;

[0164] 2-The mass ratio of diluent to propylene in the raw material;

[0165] 3- mass ratio of some reaction materials to propylene in the raw materials;

[0166] 4-The total temperature rise ΔT of the dimerization reaction satisfies: Taking Example 1 as an example, K1=1233kJ / kg, X1=77%, R0=10, R 11 =10, C P1 =2.4kJ / (kg·℃).

[0167] Similarly, taking Example 8 as an example, ΔT=ΔT1+ΔT2;

[0168]

[0169] Among them, K1 = 1211 kJ / kg, X1 = 38.5%, R0 = 10, R 11 =8, C P1 =2.4kJ / (kg·℃); K2=1204kJ / kg, X2=38.5%, R0=10, R 11 =8, R 12 =2, C P2 =2.4kJ / (kg·℃).

[0170] Table 1

[0171]

[0172]

[0173] Note: 5- The sum of the energy consumption for pressurization and distillation to separate the light components relative to 1 kg of 4-methyl-1-pentene.

[0174] It can be seen from the data in Table 1 that, compared with Comparative Examples 1-3, Examples 1-10 adopt the method provided by the present invention, add a coking inhibitor and a diluent to the raw material, and effectively improve the selectivity of 4-methyl-1-pentene by regulating the total temperature rise ΔT of the dimerization reaction.

[0175] By comparing Examples 1-3, it can be seen that adding a coking inhibitor to the raw material can improve the selectivity of 4-methyl-1-pentene, but too large an addition amount significantly reduces the conversion rate.

[0176] By comparing Examples 4-7, it can be seen that a larger mass ratio and a smaller circulation ratio can improve the selectivity of 4-methyl-1-pentene, but the separation energy consumption is higher. A larger circulation ratio and a smaller mass ratio can reduce the separation energy consumption, but the selectivity of 4-methyl-1-pentene is reduced.

[0177] By comparing Example 1 with Examples 8-10, it can be seen that by dividing part of the reaction materials into shares for heat treatment and combining the circulation ratio of the reaction materials returned to each catalyst bed, the selectivity of 4-methyl-1-pentene can be effectively regulated while ensuring the same energy consumption.

[0178] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing 4-methyl-1-pentene by propylene dimerization, characterized in that: The method includes: (1) subjecting a raw material containing propylene, a coking inhibitor and a diluent to dehydration and deoxygenation treatment to obtain a treated raw material; (2) contacting the treated raw material with a catalyst and performing a dimerization reaction to obtain a reaction material, and returning a portion of the reaction material after heat removal treatment to perform the dimerization reaction; (3) subjecting the remaining portion of the reaction material to distillation separation to obtain a light component, 4-methyl-1-pentene and a heavy component; The total temperature rise ΔT of the dimerization reaction is regulated by the mass ratio of the diluent to propylene in the raw material and the circulation ratio of the reaction material, and the circulation ratio of the reaction material is the mass ratio of the part of the reaction material to the propylene in the raw material.

2. The method according to claim 1, wherein: The dimerization reaction is carried out in at least one reactor connected in series, and the reactor is provided with an external circulation heat extraction component; Preferably, the number of the reactors is 1-6, preferably 1-4; Preferably, at least one catalyst bed is stacked in the reactor, preferably 1 to 6 catalyst beds are stacked, and more preferably 1 to 3 catalyst beds are stacked.

3. The method according to claim 1 or 2, wherein: The total temperature rise ΔT of the dimerization reaction satisfies: Wherein, ΔT is the total temperature rise of the dimerization reaction, °C; ΔT i is the temperature rise of the ith catalyst bed, °C; n is the total number of catalyst beds, and is selected from a natural number, wherein the counting rule of the catalyst beds is selected from the material flow direction, starting from the upstream catalyst bed stacked in the first reactor in series, and counting sequentially to the downstream catalyst bed stacked in the last reactor; K i is the average reaction heat of the ith catalyst bed, kJ / kg; X i is the propylene conversion rate of the i-th catalyst bed; R0 is the mass ratio of the diluent to propylene in the raw material; R 1i is the mass ratio of the material returned to the i-th catalyst bed to the propylene in the feedstock; C Pi is the specific heat of the material in the ith catalyst bed, kJ / (kg·℃); Preferably, the total temperature rise ΔT of the dimerization reaction is ≤60°C, preferably ≤30°C; Preferably, the temperature rise of a single catalyst bed is ≤30°C, preferably ≤20°C.

4. The method according to any one of claims 1 to 3, wherein: In step (1), the mass ratio of the diluent to propylene in the raw material is 0.1-200:1, preferably 1-80:1; and / or, the diluent is selected from alkanes and / or cycloalkanes, preferably selected from C2-C5 alkanes and / or C3-C6 cycloalkanes, more preferably selected from at least one of ethane, propane, n-butane, isobutane and n-pentane; And / or, the circulation ratio of the reaction materials is 0.1-200:1, preferably 1-80:

1.

5. The method according to any one of claims 1 to 4, wherein: In step (1), the molar concentration of the coking inhibitor in the raw material calculated as propylene is 2-1000 ppm, preferably 10-500 ppm; and / or, the coking inhibitor is selected from hydrogen; And / or, the water content in the treated raw material is ≤10ppm, preferably ≤3ppm; the oxygen content is ≤10ppm, preferably ≤3ppm.

6. The method according to any one of claims 1 to 5, wherein: In step (2), the conditions for the dimerization reaction include: a temperature of 50-300° C., preferably 100-200° C.; a pressure of 4-20 MPa, preferably 6-12 MPa; and / or, the catalyst is selected from supported alkali metal catalysts, preferably supported Na / K catalysts; Preferably, the alkali metal loading is 0.1-20 wt %, preferably 1-10 wt %, based on the total weight of the supported alkali metal catalyst; And / or, the temperature of the material after the heat treatment is 0-120°C lower than the temperature of the raw material after the treatment, preferably 0-100°C.

7. The method according to claim 3, wherein: In step (2), the heat removal process includes: cooling, pressurizing and heating the part of the reaction material in sequence to obtain a heat-treated material; and / or, when the total number of the catalyst beds n=1, part of the reaction materials are sequentially cooled, pressurized and heated, and returned to the catalyst bed; or, when the total number of the catalyst beds n≠1, part of the reaction materials are sequentially cooled and pressurized, and the pressurized streams are divided into n streams, which are respectively heated and returned to the i-th catalyst bed; Preferably, the temperature of the cooled material is 40-150°C, preferably 40-100°C; Preferably, the pressure of the pressurized material is 4-20 MPa, preferably 6-12 MPa; Preferably, the temperature of the heated material is 50-200°C, preferably 55-160°C.

8. The method according to any one of claims 1 to 7, wherein: In step (3), the distillation separation process includes: a first distillation separation, a second distillation separation and a third distillation separation; The first distillation separation process includes: subjecting the remaining part of the reaction material to the first distillation separation to obtain light components and a first mixed material; the second distillation separation process includes: subjecting the first mixed material to the second distillation separation to obtain light impurities and a second mixed material; the third distillation separation process includes: subjecting the second mixed material to the third distillation separation to obtain 4-methyl-1-pentene and heavy components; Preferably, the conditions for the first distillation separation include: the tower top pressure is 1-3MPa, preferably 1.5-2MPa; the conditions for the second distillation separation include: the tower top pressure is 0.2-1MPa, preferably 0.5-1MPa; the conditions for the third distillation separation include: the tower top pressure is 0.2-0.8MPa, preferably 0.2-0.5MPa; Preferably, the light fraction is returned and mixed into the feedstock.

9. The method according to any one of claims 1 to 8, wherein: The method further comprises: subjecting the dimerization reaction material to a first filtration, and the obtained reaction material is divided into the partial reaction material and the remaining partial reaction material; And / or, the method further comprises: subjecting the remaining portion of the reaction material to the distillation separation after a second filtration.

10. A device for preparing 4-methyl-1-pentene by propylene dimerization, characterized in that: The device comprises: a pretreatment unit, a reaction unit and a distillation separation unit connected in sequence; The pretreatment unit is used to dehydrate and deoxygenate the raw material containing propylene, coking inhibitor and diluent to obtain treated raw material; the reaction unit is selected from at least one reactor connected in series with an external circulation heat extraction component, and is used to contact the treated raw material with a catalyst and perform a dimerization reaction to obtain a reaction material, and return part of the reaction material to the reactor after heat extraction treatment; the distillation and separation unit is used to distill and separate the remaining part of the reaction material to obtain 4-methyl-1-pentene.

11. The device according to claim 10, wherein: A heat extraction component is provided on the circulation pipeline connected to the reactor; And / or, according to the material flow direction, the heat extraction component includes a cooler, a pump and a heater connected in sequence, which are respectively used to cool, pressurize and heat the part of the reaction material in sequence; And / or, the reactor contains at least one catalyst bed arranged in layers, preferably contains 1 to 6 catalyst beds, more preferably contains 1 to 3 catalyst beds; And / or, the device also includes: a first filtering component and / or a second filtering component; the first filtering component is arranged at the bottom of the reaction unit, and is used to obtain the reaction material after the dimerization reaction material is subjected to a first filtration; the second filtering component is connected to the reaction unit and the distillation and separation unit, and is used to perform the distillation and separation on the remaining part of the reaction material after a second filtration.

12. The device according to claim 10 or 11, wherein: The distillation separation unit comprises: a first distillation separation tower, a second distillation separation tower and a third distillation separation tower connected in sequence; The first distillation separation tower is used to perform a first distillation separation on the remaining reaction material, and a light component is obtained at the top of the tower, and a first mixed material is obtained at the bottom of the tower; the second distillation separation tower is used to perform a second distillation separation on the first mixed material, and a light impurity is obtained at the top of the tower, and a second mixed material is obtained at the bottom of the tower; the third distillation separation tower is used to perform a third distillation separation on the second mixed material, and 4-methyl-1-pentene is obtained at the top of the tower, and a heavy component is obtained at the bottom of the tower; Preferably, the top of the first distillation separation tower is connected to the pretreatment unit.

Images