Method and device for preparing 4-methyl-1-pentene

Abstract

The invention relates to the technical field of preparation of 4-methyl-1-pentene, in particular to a method and a device for preparing 4-methyl-1-pentene. The method comprises the following steps: carrying out dimerization reaction on a raw material containing propylene, a coking inhibitor and a diluent and an active metal catalyst in a non-oxidizing atmosphere, and carrying out gas-liquid separation on the obtained reaction product to obtain a gas-phase / supercritical-phase material and a liquid-phase material; wherein the gas-phase / supercritical-phase material is divided into two streams, and part of the gas-phase / supercritical-phase material is subjected to heat treatment and is returned to the dimerization reaction as a circulating material; and carrying out rectification separation on the residual gas phase / supercritical phase material and the liquid phase material to obtain the 4-methyl-1-pentene. The method not only effectively improves the selectivity of the target product, but also has low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of 4-methyl-1-pentene technology, specifically to a method for preparing 4-methyl-1-pentene and an apparatus for preparing 4-methyl-1-pentene. Background Technology

[0002] Under the reaction conditions for the preparation of 4-methyl-1-pentene by propylene dimerization, in addition to the dimerization reaction to form 4-methyl-1-pentene, other dimer isomers (such as 1-hexene, 4-methyl-2-pentene, etc.) are also generated, and polymerization reactions are also prone to occur to form polymeric products. The occurrence of side reactions leads to low selectivity and yield of the target product 4-methyl-1-pentene, as well as a short catalyst operating cycle.

[0003] The preparation of 4-methyl-1-pentene by propylene dimerization is an exothermic reaction with a large amount of heat released, making it difficult to control the reaction temperature. Furthermore, the conversion rate and selectivity are sensitive to the reaction temperature. Therefore, it is necessary to remove the heat of reaction promptly to maintain a stable reaction temperature, reduce the occurrence of side reactions, and improve the selectivity of the target product.

[0004] CN202010495971.3 discloses a synthesis process for 4-methyl-1-pentene. Propylene is dehydrated and deoxygenated before being added to a reaction unit for dimerization and isomerization. Unreacted raw materials are then separated using a packed tower and returned to the reaction unit for recycling. However, this process, even with a highly active catalyst, suffers from difficulty in controlling the reaction conversion rate and temperature. Unreacted raw materials pose a risk of continued reaction, leading to increased heat release. Excess heat cannot be removed promptly, causing the reaction temperature to deviate from the normal range and affecting the selectivity of the target product. Furthermore, the energy consumption for recycling large quantities of unreacted raw materials through distillation is very high.

[0005] Therefore, there is an urgent need to develop a reliable and energy-efficient process to provide a favorable reaction environment for the directional transformation of reactants. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low target product selectivity and high energy consumption in the existing process for preparing 4-methyl-1-pentene by propylene dimerization, as well as the blockage of catalyst powder as it travels downstream and the fire risk during disassembly of the equipment. This invention provides a method and an apparatus for preparing 4-methyl-1-pentene, which not only effectively improves the target product selectivity but also has low energy consumption.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing 4-methyl-1-pentene, the method comprising: carrying out a dimerization reaction of a raw material containing propylene, a coking inhibitor and a diluent with an active metal catalyst in a non-oxidizing atmosphere, and obtaining a reaction product by gas-liquid separation to obtain a gas phase / supercritical phase material and a liquid phase material;

[0008] In this process, the gaseous / supercritical phase material is divided into two streams. Part of the gaseous / supercritical phase material is subjected to heat treatment and then returned to the dimerization reaction as recycled material. The remaining gaseous / supercritical phase material is separated from the liquid phase material by distillation to obtain 4-methyl-1-pentene.

[0009] Preferably, the diluent is selected from alkanes and / or cycloalkanes, more preferably from C2-C5 alkanes and / or C3-C6 cycloalkanes, and more preferably from propane and / or n-butane.

[0010] Preferably, the coking inhibitor is selected from hydrogen.

[0011] Preferably, the mass ratio of the raw material to the recycled material, calculated as propylene, is 1:0.1-200, more preferably 1:5-80, and even more preferably 1:10-20.

[0012] A second aspect of the present invention provides an apparatus for preparing 4-methyl-1-pentene, the apparatus comprising a reaction unit, a gas-liquid separation unit, and a distillation separation unit connected in sequence;

[0013] The reaction unit is used to carry out a dimerization reaction between the raw materials containing propylene, coking inhibitor and diluent and an active metal catalyst in a non-oxidizing atmosphere to obtain the reaction product; the gas-liquid separation unit is used to separate the reaction product into gas-phase / supercritical material and liquid-phase material.

[0014] A heat extraction unit is installed on the pipe connecting the top of the gas-liquid separation unit and the reaction unit according to the material flow direction. This unit is used to heat-treat a portion of the gaseous / supercritical material and reuse it as recycled material in the reaction unit.

[0015] The distillation separation unit is used to distill and separate the remaining gaseous / supercritical phase material from the liquid phase material to obtain 4-methyl-1-pentene.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The method provided by the present invention uses dimerization reaction, gas-liquid separation and distillation separation techniques to separate raw materials containing propylene, coking inhibitor and diluent, and combines some gas phase / supercritical phase materials with heat treatment as recycled materials, thereby effectively improving the selectivity of 4-methyl-1-pentene and reducing energy consumption.

[0018] (2) The method provided by the present invention can effectively control the selectivity of 4-methyl-1-pentene by adjusting the mass ratio of raw materials to recycled materials, while ensuring low diluent and low energy consumption in the raw materials;

[0019] (3) The method provided by the present invention controls the degree of inhibition of polymerization reaction by adjusting the molar concentration of coking inhibitor in the raw material, thereby preventing catalyst coking and improving the selectivity of target product and catalyst activity; by controlling the diluent content in the raw material, the uncontrollable propylene conversion rate and heat release when using pure propylene as raw material are avoided, bed temperature runaway is prevented, and the reaction temperature is maintained within the range required for dimerization reaction, thereby ensuring high selectivity of target product.

[0020] (4) The method provided by the present invention is further limited to first filtration and second filtration of the residual catalyst powder in the reaction product before distillation separation, so as to avoid the risk of the active catalyst igniting when it comes into contact with water and air during the disassembly and flushing of subsequent pipelines and equipment blocked by the catalyst. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the apparatus for preparing 4-methyl-1-pentene provided by the present invention;

[0022] Figure 2 This is a schematic diagram of another apparatus for preparing 4-methyl-1-pentene provided by the present invention;

[0023] Figure 3 This is a schematic diagram of an apparatus for preparing 4-methyl-1-pentene provided in Comparative Example 2;

[0024] Figure 4 This is a schematic diagram of an apparatus for preparing 4-methyl-1-pentene provided in Comparative Example 3.

[0025] Explanation of reference numerals in the attached figures

[0026] I. Pretreatment unit; II. Reaction unit; III. Distillation and separation unit; III-1. First distillation and separation tower; III-2. Second distillation and separation tower; IV. First pump; V. First heater; VI. Gas-liquid separation unit; VII. Cooler; VIII. Second pump; IX. Second heater; O1. First filter element; O2. Second filter element.

[0027] 1. Propylene; 2. Coking inhibitor; 3. Diluent; 4. Raw material; 5. Pretreated raw material; 6. Reaction raw material; 7. Reaction product; 7-i. Partial reaction product; 7-ii. Remaining reaction product; 8. Gas phase / supercritical phase material; 8-i. Partial gas phase / supercritical phase material; 8-ii. Remaining gas phase / supercritical phase material; 9. Liquid phase material; 10. Recycled material; 11. Distillation separation raw material; 12. Light component; 13. Mixed material; 14. 4-Methyl-1-pentene; 15. Heavy component. Detailed Implementation

[0028] 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.

[0029] In this invention, unless otherwise specified, "first" and "second" do not indicate a sequence or limit the specific materials or steps; they are merely used to indicate that these are not the same material or step. For example, "first" and "second" in "first filtration" and "second filtration" are only used to indicate that these are not the same filtration process.

[0030] The first aspect of the present invention provides a method for preparing 4-methyl-1-pentene, the method comprising: carrying out a dimerization reaction of a raw material containing propylene, a coking inhibitor and a diluent with an active metal catalyst in a non-oxidizing atmosphere, and obtaining a reaction product by gas-liquid separation to obtain a gas phase / supercritical phase material and a liquid phase material;

[0031] In this process, the gaseous / supercritical phase material is divided into two streams. Part of the gaseous / supercritical phase material is subjected to heat treatment and then returned to the dimerization reaction as recycled material. The remaining gaseous / supercritical phase material is separated from the liquid phase material by distillation to obtain 4-methyl-1-pentene.

[0032] In this invention, unless otherwise specified, the gas phase / supercritical phase material can be either a gas phase material or a supercritical phase material, depending mainly on the operating conditions of gas-liquid separation; the gas phase / supercritical phase material consists of a portion of the gas phase / supercritical phase material and the remaining portion of the gas phase / supercritical phase material.

[0033] In this invention, unless otherwise specified, the non-oxidizing atmosphere refers to an oxygen content of less than 10 ppm, including but not limited to hydrogen atmosphere, methane atmosphere, ethane atmosphere, nitrogen atmosphere, etc.

[0034] In some embodiments of the present invention, preferably, the mass ratio of the raw material to the recycled material, calculated as propylene, is 1:0.1-200, for example, 1:0.1, 1:0.5, 1:1, 1:5, 1:10, 1:12, 1:15, 1:18, 1:20, 1:30, 1:40, 1:50, 1:80, 1:100, 1:150, 1:200, and any value within the range of any two values, preferably 1:5-80, more preferably 1:10-20.

[0035] In this invention, a mass ratio that meets the above range can not only control a lower bed temperature rise and obtain a highly selective target product, but also effectively reduce energy consumption. When the mass ratio is greater than 1:0.1, the temperature rise is higher and the selectivity of the target product 4-methyl-1-pentene is lower. When the mass ratio is less than 1:200, the temperature rise is lower, the selectivity of the target product 4-methyl-1-pentene is higher, and the cycle energy consumption is higher.

[0036] In some embodiments of the present invention, preferably, the diluent is selected from alkanes and / or cycloalkanes, more preferably from C2-C5 alkanes and / or C3-C6 cycloalkanes, more preferably from at least one of ethane, propane, n-butane, isobutane and n-pentane, further preferably from propane and / or n-butane, and most preferably from propane.

[0037] In some embodiments of the present invention, preferably, the mass ratio of the diluent to propylene in the raw materials is 0-20:1, for example, 0:1, 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 8:1, 10:1, 15:1, 20:1, and any value within the range of any two values, preferably 0.5-5:1.

[0038] In this invention, by adjusting the mass ratio of the raw material to the recycled material (based on propylene) and the mass ratio of the diluent to propylene in the raw material, the bed temperature rise of the dimerization reaction is ≤30°C, preferably ≤20°C, which effectively improves the selectivity of 4M1P.

[0039] In some embodiments of the present invention, preferably, the coking inhibitor is selected from hydrogen-containing gases, and more preferably from hydrogen. In the present invention, the hydrogen concentration in the hydrogen-containing gas is 80-100% by volume. In the present invention, the hydrogen-containing gas contains other gases besides hydrogen, such as methane, ethane, nitrogen, etc.

[0040] In some embodiments of the present invention, preferably, the molar concentration of the coking inhibitor, calculated as hydrogen and based on propylene, in the feedstock is 2-1000 ppm, for example, 2 ppm, 10 ppm, 20 ppm, 30 ppm, 50 ppm, 60 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 1000 ppm, and any value within any range of two such values, preferably 10-500 ppm. In the present invention, satisfying the above molar concentration range more effectively improves the selectivity of 4M1P by suppressing the occurrence of polymerization reactions and preventing catalyst coking.

[0041] In some embodiments of the present invention, preferably, the purity of the propylene is ≥80wt%, more preferably ≥95wt%.

[0042] In some preferred embodiments of the present invention, the raw material consists of propylene, a diluent and a coking inhibitor, wherein the diluent is selected from propane and / or n-butane, and the coking inhibitor is hydrogen.

[0043] In some embodiments of the present invention, preferably, the water content in the raw material is ≤10ppm and the oxygen content is ≤10ppm; more preferably, the water content is ≤3ppm and the oxygen content is ≤3ppm.

[0044] In this invention, when the water content and oxygen content in the raw material exceed the specified values, it is preferable to pretreat the raw material to obtain pretreated raw material. The pretreatment process is as follows: the raw material is dehydrated and / or deoxygenated to obtain pretreated raw material; the water content of the pretreated raw material is ≤10ppm and the oxygen content is ≤10ppm; more preferably, the water content of the pretreated raw material is ≤3ppm and the oxygen content is ≤3ppm.

[0045] In some embodiments of the present invention, preferably, when the water content and oxygen content in the raw material are >3ppm and >3ppm, the raw material is subjected to dehydration and / or deoxygenation treatment to obtain pretreated raw material for the dimerization reaction.

[0046] In some embodiments of the present invention, preferably, the dimerization reaction conditions are: a temperature of 50-300°C, preferably 100-200°C; and a pressure of 4-20 MPa, preferably 6-12 MPa.

[0047] In this invention, unless otherwise specified, all pressure parameters refer to absolute pressure.

[0048] In this invention, unless otherwise specified, the reaction products include: 4-methyl-1-pentene, catalyst powder, light components (e.g., unreacted propylene, coking inhibitor, diluent, C4-C5 fraction), heavy components (isomers, such as 4-methyl-2-pentene, and polymer products, such as C9...). + )wait.

[0049] In some embodiments of the present invention, preferably, the bed temperature rise of the dimerization reaction is ≤30°C, for example, 30°C, 20°C, 10°C, 5°C, 0°C, and any value within a range of any two values, preferably ≤20°C. In the present invention, bed temperature rise refers to the difference between the outlet temperature and the inlet temperature of a single catalyst bed, or the difference between the outlet temperature of any catalyst bed in a multi-catalyst bed and the inlet temperature of any upstream catalyst bed.

[0050] In this invention, preferably, the method further includes: subjecting the raw material or pretreated raw material to a first pressurization and a first heating in sequence to obtain a reaction material for the dimerization reaction.

[0051] In this invention, preferably, the temperature of the reaction raw materials is 50-300℃, more preferably 100-200℃; and the pressure is 4-20MPa, more preferably 6-12MPa.

[0052] In this invention, a wide range of types of active metal catalysts can be selected. Preferably, the active metal catalyst is a supported alkali metal catalyst, and more preferably, it is selected from supported Na / K catalysts. In this invention, the support for the active metal catalyst is selected from at least one of alkali metal carbonates, molecular sieves, and activated carbon, and more preferably, it is selected from alkali metal carbonates, wherein the alkali metal carbonate is selected from sodium carbonate and / or potassium carbonate.

[0053] In some embodiments of the present invention, preferably, based on the total weight of the supported alkali metal catalyst, the alkali metal loading is 0.1-20 wt%, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 20 wt%, and any value within the range of any two values, preferably 1-10 wt%.

[0054] In this invention, the gas-liquid separation aims to separate the reaction products into a gaseous / supercritical material and a liquid material. Preferably, the conditions for gas-liquid separation are: a temperature of 50-300℃, more preferably 100-200℃; and a pressure of 4-20 MPa, more preferably 6-12 MPa.

[0055] In this invention, by regulating the temperature of the recycled material, the direct reuse of high-temperature gas-phase / supercritical-phase material is avoided, which could cause temperature changes in the dimerization reaction and prevent bed overheating. This maintains the temperature within the range required for the dimerization reaction, ensuring high selectivity of the target product.

[0056] In some embodiments of the present invention, preferably, the temperature of the recycled material is ≤ the temperature of the dimerization reaction.

[0057] In some embodiments of the present invention, more preferably, the temperature of the circulating material is 50-300°C, for example, 50°C, 60°C, 80°C, 100°C, 150°C, 200°C, 250°C, 300°C, and any value within the range of any two values, preferably 50-200°C.

[0058] In some embodiments of the present invention, preferably, the heat treatment process is as follows: according to the material flow direction, the portion of the gas phase / supercritical phase material is sequentially cooled, second pressurized, and second heated to obtain the circulating material.

[0059] In some embodiments of the present invention, it is further preferred that the temperature of the cooled material is 40-150°C, more preferably 40-100°C.

[0060] In some embodiments of the present invention, more preferably, the pressure of the pressurized material is 4-20 MPa, and more preferably 6-12 MPa.

[0061] In some embodiments of the present invention, preferably, the distillation separation process is a first distillation separation and a second distillation separation; wherein, the remaining gaseous / supercritical phase material and liquid phase material are subjected to the first distillation separation to obtain light components and a mixture; the mixture is subjected to the second distillation separation to obtain 4-methyl-1-pentene and heavy components.

[0062] In this invention, unless otherwise specified, the distillation separation feedstock consists of the remaining gaseous / supercritical phase material and liquid phase material.

[0063] In this invention, the light component is rich in diluent, unreacted propylene, coking inhibitor, C4-C5 fraction, and a small amount of 4-methyl-1-pentene; the recombinant component is rich in byproducts (isomers, such as 4-methyl-2-pentene) and polymerization products, such as C9... + ).

[0064] In some embodiments of the present invention, preferably, the pressure of the first distillation separation is 1-3 MPa, for example, 1 MPa, 1.5 MPa, 2 MPa, 3 MPa, and any value within the range of any two values, preferably 1.5-2 MPa; the pressure of the second distillation separation is 0.2-0.8 MPa, for example, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.8 MPa, and any value within the range of any two values, preferably 0.2-0.5 MPa.

[0065] In this invention, to avoid clogging of the catalyst powder in the downstream process and the risk of fire from water and air during disassembly of the equipment, the method preferably further includes: subjecting the dimerization reaction material to a first filtration to obtain the reaction product.

[0066] In some embodiments of the present invention, more preferably, the method further includes: subjecting the reaction product to a second filtration followed by gas-liquid separation. This arrangement further removes residual catalyst powder from the reaction product, yielding the filtered material.

[0067] A second aspect of the present invention provides a schematic diagram of an apparatus for preparing 4-methyl-1-pentene, as shown below. Figure 1 As shown, the device includes a reaction unit II, a gas-liquid separation unit VI, and a distillation separation unit III connected in sequence;

[0068] The reaction unit II is used to carry out a dimerization reaction between the raw material 4 containing propylene 1, coking inhibitor 2 and diluent 3 and an active metal catalyst in a non-oxidizing atmosphere to obtain reaction product 7; the gas-liquid separation unit VI is used to separate the reaction product 7 into gas phase / supercritical material 8 and liquid phase material 9.

[0069] In this process, a heat extraction unit is installed on the pipe connecting the top of the gas-liquid separation unit VI and the reaction unit II, according to the material flow direction. This unit is used to heat-treat a portion of the gaseous / supercritical material 8-i and reuse it as circulating material 10 in the reaction unit II.

[0070] The distillation separation unit III is used to distill and separate the remaining gaseous / supercritical phase material 8-ii from the liquid phase material 9 to obtain 4-methyl-1-pentene 14.

[0071] In this invention, such as Figure 2 As shown, the apparatus further includes a pretreatment unit I disposed before the reaction unit II, used to dehydrate and / or deoxygenate the raw material 4 to obtain pretreated raw material 5 for the dimerization reaction.

[0072] According to the present invention, preferably, such as Figure 1-2 As shown, the device further includes: a first pump IV and a first heater V are sequentially installed on the upstream pipe of the reaction unit II or on the pipe connecting the pretreatment unit I and the reaction unit II, according to the material flow direction, for sequentially pressurizing the raw material 4 or the pretreated raw material 5 and heating it to obtain the reaction raw material 6.

[0073] According to the present invention, preferably, such as Figure 1-2 As shown, according to the material flow direction, the heat extraction unit includes: a cooler VII, a second pump VIII, and a second heater IX connected in series, used to cool, pressurize, and heat the partial gas phase / supercritical phase material 8-i in sequence to obtain the circulating material 10.

[0074] In some embodiments of the present invention, preferably, the reaction unit comprises at least one reactor in series, more preferably 2-6 reactors in series, and even more preferably 2-4 reactors in series. In the present invention, the reactors shown include, but are not limited to, fixed-bed reactors.

[0075] In some embodiments of the present invention, preferably, each reactor is provided with 1-6 catalyst beds, and more preferably 1-3 catalyst beds.

[0076] In some embodiments of the present invention, preferably, such as Figure 1-2 As shown, the reactor is equipped with a first filter element 01, which is located below the catalyst bed to perform a first filtration of the dimerization product to obtain the reaction product 7.

[0077] In this invention, the first filter element 01 is disposed below the last catalyst bed layer from top to bottom in the reactor. In this invention, the first filter element 01 is selected from meshes and / or membranes with a filtration accuracy ≤15μm, including but not limited to metal meshes, sintered metal powders, ceramic membranes, and polyester filter cartridges.

[0078] In some embodiments of the present invention, preferably, such as Figure 1-2 As shown, the gas-liquid separation unit VI is selected from a separatory tank equipped with a second filter element 02. In this invention, the second filter element 02 is selected from a mesh and / or membrane with a filtration accuracy ≤15μm, including but not limited to metal mesh, sintered metal powder, ceramic membrane, and polyester filter element.

[0079] In this invention, such as Figure 1 As shown, preferably, the distillation separation unit is selected from the first distillation separation column III-1 and the second distillation separation column III-2 connected in series;

[0080] The first distillation column III-1 is used to perform a first distillation separation on the remaining gaseous / supercritical phase material 8-ii and liquid phase material 9 as distillation separation feedstock 11 to obtain light component 12 and mixture 13; the second distillation column III-2 is used to perform a second distillation separation on the mixture 13 to obtain 4-methyl-1-pentene 14 and heavy component 15.

[0081] According to a particularly preferred embodiment of the present invention, a method for preparing 4-methyl-1-pentene is provided, the method comprising: carrying out a dimerization reaction of a raw material containing propylene, a coking inhibitor and a diluent with an active metal catalyst in a non-oxidizing atmosphere, and obtaining a gas-phase / supercritical phase material and a liquid phase material after gas-liquid separation of the reaction product;

[0082] In this process, the gaseous / supercritical phase material is divided into two streams. Part of the gaseous / supercritical phase material is pyrolyzed and then returned to the dimerization reaction as recycled material. The remaining gaseous / supercritical phase material is separated from the liquid phase material by distillation to obtain 4-methyl-1-pentene.

[0083] The diluent is selected from propane; the coking inhibitor is selected from hydrogen.

[0084] The mass ratio of the raw material to the recycled material, calculated as propylene, is 1:10-20; the mass ratio of the diluent to propylene in the raw material is 0-20:1; and the molar concentration of the coking inhibitor, calculated as hydrogen, in the raw material, is 10-500 ppm.

[0085] The present invention will be described in detail below through embodiments.

[0086] Example 1

[0087] The apparatus for preparing 4-methyl-1-pentene is as follows: Figure 2 As shown, the device includes a pretreatment unit I, a first pump IV, a first heater V, a reaction unit II, a gas-liquid separation unit VI, a first distillation separation tower III-1, and a second distillation separation tower III-2 connected in sequence; wherein, according to the material flow direction, a cooler VII, a second pump VIII, and a second heater IX are sequentially arranged on the pipe connecting the top of the gas-liquid separation unit VI and the reaction unit II.

[0088] Among them, reaction unit II is selected from a fixed bed reactor containing a single catalyst bed, and the fixed bed reactor and gas-liquid separation unit VI are respectively equipped with a first filter element 01 and a second filter element 02; the first filter element 01 and the second filter element 02 are both selected from metal filter screens with a filtration accuracy of 10μm.

[0089] The method for preparing 4-methyl-1-pentene is carried out in the above-described apparatus, and the method includes:

[0090] (1) The raw material containing propylene, hydrogen and propane is dehydrated and deoxygenated to obtain the pretreated raw material; the molar concentration of hydrogen in the above raw material, based on propylene, is 60 ppm; the mass ratio of propane to propylene is 1:1; the water content in the above pretreated raw material is 0.7 ppm and the oxygen content is 0.8 ppm.

[0091] (2) The pretreated raw materials are sequentially pressurized to 10 MPa and heated to 150°C. The resulting reaction raw materials undergo dimerization reaction under the action of a catalyst (supported Na / K catalyst, Na / K loading is 6 wt%) (temperature is 150°C; pressure is 10 MPa). The resulting dimerization reaction material is filtered first to obtain the reaction product.

[0092] The reaction products were filtered a second time and then subjected to gas-liquid separation (temperature 150℃; pressure 10MPa) to obtain supercritical phase material and liquid phase material.

[0093] (3) The supercritical phase material is divided into two streams. Part of the supercritical phase material is cooled to 80°C, pressurized to 10MPa, and heated to 150°C in sequence. It is then returned as a recycled material to carry out the dimerization reaction.

[0094] The mass ratio of the above-mentioned raw materials to the recycled materials, calculated as propylene, is 1:15.

[0095] The remaining supercritical phase material and liquid phase material were mixed and used as raw material for the first distillation separation (top pressure of 1.8 MPa). The mixture obtained from the bottom of the column was then subjected to the second distillation separation (top pressure of 0.3 MPa), and 4-methyl-1-pentene S1 was obtained from the top of the column.

[0096] Example 2

[0097] The apparatus according to Example 1;

[0098] The method is the same as in Example 1, except that...

[0099] In step (1), the molar concentration of hydrogen in the above raw materials, based on propylene, is replaced with 20 ppm; the other conditions are the same, and 4-methyl-1-pentene S2 is obtained.

[0100] Example 3

[0101] The apparatus according to Example 1;

[0102] The method is the same as in Example 1, except that...

[0103] In step (1), the molar concentration of hydrogen in the above raw materials, based on propylene, is replaced with 400 ppm; the other conditions are the same, and 4-methyl-1-pentene S3 is obtained.

[0104] Example 4

[0105] The apparatus according to Example 1;

[0106] The method is the same as in Example 1, except that...

[0107] In step (3), the mass ratio of the above raw material to the recycled material, calculated as propylene, is replaced with 1:10; the other conditions are the same, and 4-methyl-1-pentene S4 is obtained.

[0108] Example 5

[0109] The apparatus according to Example 1;

[0110] The method is the same as in Example 1, except that...

[0111] In step (3), the mass ratio of the above raw material to the recycled material, calculated as propylene, is replaced with 1:50; the other conditions are the same, and 4-methyl-1-pentene S5 is obtained.

[0112] Example 6

[0113] The apparatus according to Example 1;

[0114] The method is the same as in Example 1, except that...

[0115] In step (3), the mass ratio of the above raw materials to the recycled materials, calculated as propylene, is replaced with 1:1; the other conditions are the same. Due to the excessive temperature rise in the reaction, the reaction cannot proceed normally.

[0116] Example 7

[0117] The apparatus according to Example 1;

[0118] The method is the same as in Example 1, except that...

[0119] In step (3), the mass ratio of the above raw materials to the recycled materials, calculated as propylene, is replaced with 1:100;

[0120] Under the same conditions, 4-methyl-1-pentene S7 was obtained.

[0121] Example 8

[0122] The apparatus according to Example 1;

[0123] The method is the same as in Example 1, except that...

[0124] In step (1), propane is not added;

[0125] Under the same conditions, 4-methyl-1-pentene S8 was obtained.

[0126] Example 9

[0127] The apparatus according to Example 1;

[0128] The method is the same as in Example 1, except that...

[0129] In step (1), the mass ratio of propane to propylene in the above raw materials is replaced with 15:1;

[0130] Under the same conditions, 4-methyl-1-pentene S9 was obtained.

[0131] Comparative Example 1

[0132] The apparatus according to Example 1;

[0133] The method is the same as in Example 1, except that...

[0134] In step (1), no hydrogen gas was added, and the other conditions were the same, to obtain 4-methyl-1-pentene DS1.

[0135] Comparative Example 2

[0136] The apparatus according to Embodiment 1 differs in that the top of the gas-liquid separation unit VI is not connected to the reaction unit II, and it does not include the cooler VII, the second pump VIII, and the second heater IX; that is,

[0137] like Figure 3 As shown, the device includes a pretreatment unit I, a first pump IV, a first heater V, a reaction unit II, a gas-liquid separation unit VI, a first distillation separation tower III-1, and a second distillation separation tower III-2 connected in sequence; wherein, the reaction unit II is selected from a fixed-bed reactor containing a single catalyst bed, and the fixed-bed reactor and the gas-liquid separation unit VI are respectively provided with a first filter element 01 and a second filter element 02; both the first filter element 01 and the second filter element 02 are selected from metal filter screens with a filtration accuracy of 10μm.

[0138] The method is the same as in Example 1, except that...

[0139] In step (1), the mass ratio of propane to propylene in the above raw materials is replaced with 15:1;

[0140] In step (3), the above-mentioned supercritical material and liquid material are mixed as raw materials for distillation separation, and the other conditions are the same to obtain 4-methyl-1-pentene DS2.

[0141] Comparative Example 3

[0142] The apparatus according to Example 1 differs in that, in accordance with the material flow direction, a cooler VII, a second pump VIII, and a second heater IX are installed on the pipes connecting the bottom and top of reaction unit II; that is,

[0143] like Figure 4 As shown, the device includes a pretreatment unit I, a first pump IV, a first heater V, a reaction unit II, a gas-liquid separation unit VI, a first distillation separation tower III-1, and a second distillation separation tower III-2 connected in sequence; wherein, according to the material flow direction, a cooler VII, a second pump VIII, and a second heater IX are sequentially installed on the pipes connecting the bottom and top of the reaction unit II.

[0144] Among them, reaction unit II is selected from a fixed bed reactor containing a single catalyst bed, and the fixed bed reactor and gas-liquid separation unit VI are respectively equipped with a first filter element 01 and a second filter element 02; the first filter element 01 and the second filter element 02 are both selected from metal filter screens with a filtration accuracy of 10μm.

[0145] The method is the same as in Example 1, except that...

[0146] In step (1), the raw materials do not contain propane;

[0147] In step (2), the above reaction products are divided into two streams. Part of the reaction products are successively cooled to 80°C, pressurized to 10MPa, and heated to 150°C to obtain recycled material that is returned to the above dimerization reaction.

[0148] The mass ratio of the above-mentioned raw materials and some reaction products, calculated based on propylene, is 1:15.

[0149] The remaining reaction products were subjected to gas-liquid separation to obtain supercritical phase material and liquid phase material;

[0150] In step (3), the above-mentioned supercritical phase material and liquid phase material are used as raw materials for distillation separation, and the other conditions are the same, to obtain 4-methyl-1-pentene DS3.

[0151] Comparative Example 4

[0152] The apparatus is the same as that of Comparative Example 3, except that a diluent 3 is added to raw material 4.

[0153] Following the method of Comparative Example 3, the difference is that...

[0154] In step (1), the raw material contains propane, and the mass ratio of propane to propylene is 1:1.

[0155] Under the same conditions, 4-methyl-1-pentene DS4 was obtained.

[0156] Table 1

[0157]

[0158] Note: 1 - Molar concentration of hydrogen in the feedstock, expressed in ppm, based on propylene;

[0159] 2- The mass ratio of propane to propylene in the raw materials;

[0160] 3- The mass ratio of raw materials to recycled materials, calculated as propylene.

[0161] Continued from Table 1

[0162]

[0163] Note: 4-The sum of the energy consumption of the cycle and the energy consumption of the distillation separation of light components relative to 1 kg of 4-methyl-1-pentene.

[0164] As shown in Table 1, compared with Comparative Example 1, Examples 1-10, using the method provided by this invention, added hydrogen as a coking inhibitor to the raw materials, which effectively improved the selectivity of 4-methyl-1-pentene. Further comparison of Examples 1-3 shows that although an excessive amount of coking inhibitor increases the selectivity of the target product, it significantly reduces the raw material conversion rate.

[0165] By comparing Comparative Example 2 with Examples 1 and 9, it can be seen that the process without setting up a separation tank to recycle gas phase or supercritical material back to the reactor, by increasing the proportion of propane in the feedstock, achieves a selectivity of 4-methyl-1-pentene that is comparable to that of Example 1, but lower than the 94% achieved in Example 9 using the same propane proportion; however, Comparative Example 2 significantly increases energy consumption by increasing the proportion of propane in the feedstock.

[0166] By comparing Comparative Examples 3-4 with Examples 1 and 8, it can be seen that, compared with the process of Comparative Examples 3-4 which separates part of the reactants at the reactor outlet and recycles them back to the reactor, the embodiments proposed in this invention have higher selectivity for 4-methyl-1-pentene under the premise of comparable separation energy consumption.

[0167] By comparing Examples 1 and 4-7, it can be seen that by adjusting the mass ratio of raw material to recycled material based on propylene, the bed temperature rise of the dimerization reaction can be affected, thereby controlling the selectivity of the target product, especially the mass ratio that meets the preferred protection range, and achieving high 4-methyl-1-pentene selectivity with low energy consumption.

[0168] 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 process for the preparation of 4-methyl-l-pentene, characterized in that, The method comprises: carrying out dimerization reaction of a raw material containing propylene, a coking inhibitor and a diluent with a live metal catalyst in a non-oxidizing atmosphere, and after gas-liquid separation of the obtained reaction product, obtaining gas / supercritical phase material and liquid phase material; Wherein, the gas / supercritical phase material is divided into two streams, part of the gas / supercritical phase material is subjected to heat removal treatment and then returned to the dimerization reaction as a circulating material; the remaining gas / supercritical phase material is subjected to rectification separation with the liquid phase material to obtain 4-methyl-1-pentene.

2. The method of claim 1, wherein, The mass ratio of the raw material to the circulating material, based on propylene, is 1:0.1-200, preferably 1:5-80, and more preferably 1:10-20.

3. The method of claim 1 or 2, wherein, The diluent is selected from alkanes and / or cycloalkanes, preferably C2-C5 alkanes and / or C3-C6 cycloalkanes, and more preferably propane and / or n-butane; Preferably, the coking inhibitor is selected from hydrogen-containing gas, preferably hydrogen. Preferably, in the raw material, the mass ratio of the diluent to propylene is 0-20:1, preferably 0.5-5:

1. Preferably, in the raw material, the molar concentration of the coking inhibitor, based on hydrogen, is 2-1000 ppm, preferably 10-500 ppm.

4. The method of any of claims 1-3, wherein, The water content in the raw material is ≤10 ppm, preferably ≤3 ppm; and the oxygen content is ≤10 ppm, preferably ≤3 ppm; Preferably, when the water content in the raw material is >3 ppm and the oxygen content is >3 ppm, the raw material is subjected to dehydration treatment and / or deoxygenation treatment to obtain a pretreated raw material for the dimerization reaction.

5. The method of any of claims 1-4, wherein, The dimerization reaction is carried out at a temperature of 50-300°C, preferably 100-200°C, and a pressure of 4-20 MPa, preferably 6-12 MPa. Preferably, the bed temperature rise of the dimerization reaction is ≤30°C, preferably ≤20°C. Preferably, the method further comprises: sequentially subjecting the raw material or the pretreated raw material to first pressurization and first heating to obtain a reaction raw material for the dimerization reaction.

6. The method of any of claims 1-5, wherein, The live metal catalyst is a supported alkali metal catalyst, preferably selected from 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.

7. The method of any of claims 1-6, wherein, The gas-liquid separation is carried out at a temperature of 50-300°C, preferably 100-200°C, and a pressure of 4-20 MPa, preferably 6-12 MPa. Preferably, the temperature of the circulating material is ≤ the temperature of the dimerization reaction. Further preferably, the temperature of the circulating material is 50-300°C, preferably 50-200°C. Preferably, the heat removal treatment is carried out by sequentially subjecting the part of the gas / supercritical phase material to cooling, second pressurization and second heating in the direction of material flow to obtain the circulating material. Further preferably, the temperature of the cooled material is 40-150°C, preferably 40-100°C. Further preferably, the pressure of the pressurized material is 4-20 MPa, preferably 6-12 MPa.

8. The method of any one of claims 1-7, wherein, The process of the rectification separation is a first rectification separation and a second rectification separation; The first rectification separation is performed on the remaining part of the gas phase / supercritical phase material and the liquid phase material to obtain light components and mixed material, and the second rectification separation is performed on the mixed material to obtain 4-methyl-1-pentene and heavy components; Preferably, the pressure of the first rectification separation is 1-3 MPa, preferably 1.5-2 MPa, and the pressure of the second rectification separation is 0.2-0.8 MPa, preferably 0.2-0.5 MPa; Preferably, the method further comprises: performing a first filtration on the material of the dimerization reaction to obtain the reaction product; Preferably, the method further comprises: performing a second filtration on the reaction product, and then performing the gas-liquid separation.

9. An apparatus for producing 4-methyl-l-pentene, characterized by The device comprises a reaction unit, a gas-liquid separation unit and a rectification separation unit connected in sequence; The reaction unit is used for performing a dimerization reaction on a raw material containing propylene, a coking inhibitor and a diluent with a living metal catalyst in a non-oxidizing atmosphere to obtain a reaction product, and the gas-liquid separation unit is used for performing a gas-liquid separation on the reaction product to obtain a gas phase / supercritical material and a liquid phase material; The top of the gas-liquid separation unit and the pipeline of the reaction unit are connected in sequence, and a heat removal unit is arranged on the pipeline to remove part of the gas phase / supercritical material as a circulating material for the reaction unit; The rectification separation unit is used for performing a rectification separation on the remaining part of the gas phase / supercritical phase material and the liquid phase material to obtain 4-methyl-1-pentene.

10. The apparatus of claim 9, wherein, The device further comprises a pretreatment unit arranged before the reaction unit, which is used for performing a dehydration treatment and / or a deoxygenation treatment on the raw material to obtain pretreated raw material for the dimerization reaction; Preferably, the device further comprises a first pump and a first heater arranged in sequence on the pipeline upstream of the reaction unit or on the pipeline connecting the pretreatment unit and the reaction unit in the material flow direction, which are used for sequentially pressurizing and heating the raw material or the pretreated raw material to obtain reaction raw material; Preferably, the heat removal unit comprises a cooler, a second pump and a second heater connected in sequence, which are used for sequentially cooling, pressurizing and heating the part of the gas phase / supercritical phase material to obtain the circulating material; Preferably, the reaction unit comprises at least one reactor connected in sequence, preferably 2-6 reactors connected in sequence, and more preferably 2-4 reactors connected in sequence; Preferably, each reactor is provided with 1-6 catalyst beds, preferably 1-3 catalyst beds; Preferably, the reactor is provided with a first filtration component, and the first filtration component is arranged below the catalyst bed; Preferably, the gas-liquid separation unit is a liquid separation tank provided with a second filtration component.

11. The apparatus of claim 9 or 10, wherein, The rectification separation unit comprises a first rectification separation tower and a second rectification separation tower connected in sequence, The first rectification separation tower is used for first rectification separation of the remaining part of the gas phase / supercritical phase material and the liquid phase material, to obtain light components and mixed material; the second rectification separation tower is used for second rectification separation of the mixed material, to obtain 4-methyl-1-pentene and heavy components.

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