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

Abstract

The present invention relates to the technical field of preparing 4-methyl-1-pentene, and specifically relates to a method and apparatus for preparing 4-methyl-1-pentene. The method comprises: causing a raw material containing propylene, a coke formation inhibitor and an optional diluent to undergo a dimerization reaction in the presence of a catalyst; performing gas-liquid separation on a resulting reaction mixture, to obtain a gas and / or supercritical phase flow and a liquid phase flow; splitting the gas and / or supercritical phase flow into two portions, a portion of the gas and / or supercritical phase flow undergoing heat recovery treatment and being returned as a recycled stream to the dimerization reaction; and performing distillation of the remaining portion of the gas and / or supercritical phase flow and the liquid phase flow, to obtain 4-methyl-1-pentene. The method and the corresponding apparatus enable efficient temperature control, high 4M1P selectivity, and long-cycle operation with relatively low energy consumption.

Description

Method and apparatus for preparing 4-methyl-1-pentene Technical Field

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

[0002] Propylene is a key raw material in modern chemical industry, and its dimerization process produces 4-methyl-1-pentene (4M1P), which has significant industrial applications. As a high-performance C6 olefin, 4-methyl-1-pentene is primarily used as a comonomer in the production of linear low-density polyethylene (LLDPE). This resin exhibits excellent tensile and tear strength, as well as good dielectric properties. Compared to 1-hexene, the more branched structure of 4-methyl-1-pentene, as a comonomer, can further optimize the performance of LLDPE, such as improving the material's toughness, transparency, and environmental stress resistance. Due to its cost advantages in production, 4-methyl-1-pentene has received increasing attention in recent years. Furthermore, 4-methyl-1-pentene can also undergo self-polymerization to produce poly(4-methyl-1-pentene) (PMP) resin. This resin is a high-performance thermoplastic material with excellent high temperature resistance, chemical corrosion resistance, low dielectric properties, good air permeability, transparency, low density, good biocompatibility and low surface tension. It is widely used in membrane separation, food packaging, medical devices and electronic components.

[0003] Propylene dimerization is a strongly exothermic process with a significant heat effect, requiring stringent temperature control. Furthermore, the propylene conversion rate and the selectivity of the target product are sensitive to the reaction temperature. If the heat of reaction cannot be removed promptly and effectively, it will be difficult to maintain a stable reaction temperature, thereby exacerbating side reactions and reducing the selectivity of the target product.

[0004] In the process of preparing 4-methyl-1-pentene by propylene dimerization, in addition to the target dimerization reaction to generate 4-methyl-1-pentene, several side reactions occur, including the formation of dimer isomers such as 1-hexene and 4-methyl-2-pentene (4M2P), and further polymerization reactions to generate polymers with higher carbon numbers. These side reactions not only reduce the selectivity and yield of the target product 4M1P, but also accelerate catalyst deactivation and shorten its operating cycle.

[0005] To suppress the increased side reactions and catalyst deactivation caused by the strong exothermic effect of propylene dimerization, a common industrial approach is to maintain the single-pass conversion rate of propylene at a low level. This method, by limiting the reaction progress and reducing the adiabatic temperature rise, stabilizes the reaction temperature within a certain range, which is beneficial for improving the selectivity of 4M1P. However, a significant drawback of this method is that low-conversion operation severely limits the product yield per pass through the reactor, resulting in a large amount of unreacted propylene requiring recycling, which not only increases the separation load but also leads to low reactor production efficiency. Another common approach relies on external forced heat removal (e.g., high-load heat exchange systems) to achieve temperature control. Although this can maintain stable reaction conditions to some extent, it significantly increases the energy consumption and operating costs of the unit, posing significant challenges in terms of economics and process sustainability.

[0006] Therefore, there is an urgent need to develop a process that achieves high-efficiency temperature control and high selectivity with low energy consumption, thereby improving the industrial cost-effectiveness of propylene-directed conversion to 4-methyl-1-pentene. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems in existing processes for preparing 4-methyl-1-pentene by propylene dimerization, such as the difficulty in simultaneously achieving "high selectivity" and "high yield," "controllable temperature rise" and "low energy consumption," and limited operating cycles. This invention provides a method and apparatus for preparing 4-methyl-1-pentene. This method and apparatus can solve at least one problem existing in the prior art, such as achieving efficient temperature control and high 4M1P selectivity with low energy consumption under high conversion conditions, and enabling long-term operation.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing 4-methyl-1-pentene, the method comprising:

[0009] (a) A feedstock comprising propylene, a coking inhibitor, and optionally a diluent is subjected to a dimerization reaction in the presence of a catalyst to obtain a reaction mixture.

[0010] (b) The reaction mixture is subjected to gas-liquid separation to obtain a gas phase and / or a supercritical phase stream and a liquid phase stream;

[0011] (c) The gaseous and / or supercritical phase stream is divided into two parts, wherein a portion of the gaseous and / or supercritical phase stream is subjected to heat treatment and returned to step (a) as a circulating stream, wherein the mass ratio of propylene in the raw material to the circulating stream is ≤1:5;

[0012] (d) Fractionate the remaining gaseous and / or supercritical phase stream with the liquid stream to obtain 4-methyl-1-pentene.

[0013] 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 fractionation unit connected in sequence;

[0014] The reaction unit is used to carry out a dimerization reaction of a raw material containing propylene, a coking inhibitor and an optional diluent in the presence of a catalyst to obtain a reaction mixture;

[0015] The gas-liquid separation unit has a gas phase and / or supercritical phase stream outlet and a liquid phase stream outlet, which is used to separate the reaction mixture into gas phase and / or supercritical phase stream and liquid phase stream.

[0016] The gas phase and / or supercritical phase stream outlets of the gas-liquid separation unit are fluidly connected to the reaction unit and the fractionation unit, respectively. A heat extraction unit is provided on the pipeline that connects the gas phase and / or supercritical phase stream outlets to the reaction unit, which is used to perform heat extraction on a portion of the gas phase and / or supercritical phase stream and then return it to the reaction unit as a circulating stream.

[0017] The fractionation unit is used to fractionate the remaining gaseous and / or supercritical phase stream with the liquid stream to obtain 4-methyl-1-pentene.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention returns a portion of the gas phase and / or supercritical phase stream obtained after gas-liquid separation of the reaction mixture to the dimerization reaction as a circulating stream after heat removal, and controls the mass ratio of propylene in the raw material to the circulating stream. This can avoid uncontrollable propylene conversion rate and heat release, prevent bed temperature runaway, and help maintain the reaction temperature within the range required for the dimerization reaction. Even under low diluent or even no diluent conditions, the bed temperature rise can be controlled with low energy consumption, thus improving the selectivity of the target product.

[0020] (2) By adding coking inhibitors to the raw materials and adjusting their molar concentration, the present invention can inhibit the occurrence of polymerization reactions, prevent catalyst coking, thereby improving the selectivity of the target product and the activity and stability of the catalyst, and extending the operating cycle.

[0021] (3) By adding a diluent to the raw materials and adjusting the mass ratio of the diluent to propylene, the present invention can further synergistically control the temperature rise of the bed and improve the selectivity of the target product; in addition, the addition of the diluent is also beneficial to the elution of polymers attached to the active centers on the catalyst surface.

[0022] (4) By optimizing the mass ratio of diluent to propylene, the mass ratio of propylene to circulating stream, and the molar concentration of coking inhibitor in the raw materials, this invention can effectively control the propylene conversion rate, 4M1P selectivity, process energy consumption, and operating cycle. Thus, under conditions of high conversion rate, it can still achieve efficient temperature control, high 4M1P selectivity, and long cycle operation with low energy consumption. Attached Figure Description

[0023] Figure 1 is a process flow diagram for the preparation of 4-methyl-1-pentene according to a specific embodiment of the present invention;

[0024] Figure 2 is a process flow diagram for the preparation of 4-methyl-1-pentene according to another specific embodiment of the present invention;

[0025] Figure 3 is a flow chart of the 4-methyl-1-pentene preparation process used in Comparative Example 3;

[0026] Figure 4 is a flow chart of the preparation process of 4-methyl-1-pentene used in Comparative Example 4;

[0027] Figure 5 is a flow chart of the 4-methyl-1-pentene preparation process used in Comparative Example 6.

[0028] Explanation of reference numerals in the attached figures: I. Pretreatment unit; II. Reaction unit; III. Fractionation unit; III-1. First distillation column; III-2. Second distillation column; 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. 1. Propylene; 2. Coking inhibitor; 3. Diluent; 4. Raw material; 5. Pretreated raw material; 6. Reaction raw material; 7. Reaction mixture; 7-i. Partial reaction mixture; 7-ii. Remaining reaction mixture; 8. Gas phase and / or supercritical phase stream; 8-i. Partial gas phase and / or supercritical phase stream; 8-ii. Remaining gas phase and / or supercritical phase stream; 9. Liquid phase stream; 10. Circulating stream; 11. Fractionation feed; 12. Light component; 13. Mixed component; 14. 4-Methyl-1-pentene; 15. Heavy component. Detailed Implementation

[0029] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0030] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of conflict, including definitions, this specification shall prevail.

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values, such as up to 10% plus or minus the disclosed numerical 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.

[0032] In this invention, unless otherwise specified, "first" and "second" do not indicate a sequence or limit the flow or steps, but are used only to indicate that they are not the same flow or step. For example, "first" and "second" in "first filter" and "second filter" are only used to indicate that they are not the same filter.

[0033] The first aspect of this invention provides a method for preparing 4-methyl-1-pentene, the method comprising:

[0034] (a) A feedstock comprising propylene, a coking inhibitor, and optionally a diluent is subjected to a dimerization reaction in the presence of a catalyst to obtain a reaction mixture.

[0035] (b) The reaction mixture is subjected to gas-liquid separation to obtain a gas phase and / or a supercritical phase stream and a liquid phase stream;

[0036] (c) The gaseous and / or supercritical phase stream is divided into two parts, wherein a portion of the gaseous and / or supercritical phase stream is subjected to heat treatment and returned to step (a) as a circulating stream, wherein the mass ratio of propylene in the raw material to the circulating stream is ≤1:5;

[0037] (d) Fractionate the remaining gaseous and / or supercritical phase stream with the liquid stream to obtain 4-methyl-1-pentene.

[0038] In this invention, unless otherwise specified, the term "gas phase and / or supercritical phase stream" refers to a stream that can be a gas phase stream, a supercritical phase stream, or a mixture of gas phase and supercritical phase streams, depending primarily on the operating conditions of the gas-liquid separation; the gas phase and / or supercritical phase stream consists of a portion of the gas phase and / or supercritical phase stream and the remaining portion of the gas phase and / or supercritical phase stream.

[0039] In some embodiments of the present invention, the mass ratio of propylene in the raw material to the circulating stream is ≤1:5, for example, 1:5, 1:10, 1:12, 1:15, 1:18, 1:20, 1:30, 1:40, 1:50, 1:80, 1:100, and any value within the range of any two values, preferably 1:10-80, more preferably 1:10-20.

[0040] In this invention, by returning a portion of the gaseous and / or supercritical phase streams to step (a) as a recycle stream after heat removal, the bed temperature rise in the dimerization reaction can be effectively controlled. By further adjusting the mass ratio of propylene in the feedstock to the recycle stream within a preferred range, not only can the bed temperature rise be controlled and high 4M1P selectivity be obtained, but energy consumption can also be significantly reduced. When the mass ratio is greater than 1:5, the temperature rise is high and the selectivity of the target product is low; when the mass ratio is less than 1:100, although the temperature rise is low and the selectivity of the target product is high, the recycle energy consumption increases significantly.

[0041] In some embodiments of the present invention, the diluent is selected from C2-C6 alkanes and mixtures thereof, preferably from C2-C5 alkanes, C3-C6 cycloalkanes and mixtures thereof, more preferably from ethane, propane, n-butane, isobutane, n-pentane and mixtures thereof, even more preferably from propane, n-butane and mixtures thereof, and even more preferably from propane.

[0042] In some embodiments of the present invention, the mass ratio of the diluent to propylene in the raw material 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.

[0043] In this invention, by adding a diluent to the raw materials and adjusting the mass ratio of the diluent to propylene, the bed temperature rise can be further synergistically controlled, ensuring that the bed temperature rise of the dimerization reaction is ≤30℃, preferably ≤20℃. This effectively improves the selectivity of 4M1P without significantly affecting the propylene conversion rate. Furthermore, the addition of the diluent also facilitates the elution of polymers adhering to the active sites on the catalyst surface, reducing the selectivity of byproducts.

[0044] In some embodiments of the present invention, the coking inhibitor contains hydrogen, preferably hydrogen. In some embodiments of the present invention, the concentration of hydrogen in the coking inhibitor is 80-100% by volume. In some embodiments of the present invention, the coking inhibitor contains other gases besides hydrogen, such as methane, ethane, nitrogen, etc.

[0045] In some embodiments of the present invention, based on propylene in the raw material, the molar concentration of the coking inhibitor 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 the range of any two values, preferably 10-300 ppm.

[0046] In this invention, by adding a coking inhibitor to the raw material and controlling its molar concentration within the above-mentioned range, the occurrence of polymerization reaction can be suppressed, catalyst coking can be prevented, the selectivity of 4M1P and the activity and stability of the catalyst can be effectively improved, and the operating cycle can be extended.

[0047] In some embodiments of the present invention, the purity of the propylene is ≥80 wt%, preferably ≥95 wt%.

[0048] 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, n-butane and mixtures thereof, and the coking inhibitor is hydrogen.

[0049] In some embodiments of the present invention, the conditions for the dimerization reaction include: a temperature of 50-300°C, preferably 100-200°C; and a pressure of 4-20 MPa, preferably 6-12 MPa.

[0050] In this invention, unless otherwise specified, all pressure parameters refer to absolute pressure.

[0051] In some embodiments of the present invention, 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, the term "bed temperature rise" refers to the difference between the outlet temperature and the inlet temperature of a single catalyst bed, or the sum of the differences between the outlet temperature and the inlet temperature of each catalyst bed in a multi-catalyst bed.

[0052] In some embodiments of the present invention, 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 raw material for use in the dimerization reaction.

[0053] In some embodiments of the present invention, the temperature of the reaction raw materials is 50-300°C, preferably 100-200°C; and the pressure is 4-20 MPa, preferably 6-12 MPa.

[0054] In this invention, the type of catalyst is not particularly limited. Preferably, the catalyst is a supported alkali metal catalyst, and more preferably a supported Na / K catalyst. In this invention, the support for the catalyst is selected from at least one of alkali metal carbonates, molecular sieves, and activated carbon, preferably an alkali metal carbonate. Preferably, the alkali metal carbonate is selected from sodium carbonate and / or potassium carbonate.

[0055] In some embodiments of the present invention, the alkali metal loading is 0.1-20 wt% based on the total weight of the supported alkali metal catalyst, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, and any value within any range of any two values, preferably 1-10 wt%.

[0056] In some embodiments of the present invention, the catalyst surface is coated with paraffin wax, which is removed from the catalyst surface by purging with the diluent during reactor heating before the dimerization reaction. Preferably, the mass ratio of paraffin wax to the supported alkali metal catalyst is 0.01-2:1, for example 0.01:1, 0.02:1, 0.05:1, 0.1:1, 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, and any value within any range of any two values, preferably 0.05-1:1. By coating the catalyst surface with paraffin wax, the bed temperature rise during catalyst loading can be controlled to less than 10°C, for example less than 10°C, less than 5°C, less than 3°C, preferably less than 3°C.

[0057] In this invention, when a supported alkali metal catalyst is used in step (a), the dimerization reaction is carried out under a non-oxidizing atmosphere. Unless otherwise specified, the term "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, and mixtures thereof.

[0058] In some embodiments of the present invention, the water content in the raw material is ≤10ppm and the oxygen content is ≤10ppm; preferably, the water content is ≤3ppm and the oxygen content is ≤3ppm.

[0059] 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; preferably, the water content of the pretreated raw material is ≤3ppm and the oxygen content is ≤3ppm.

[0060] In some embodiments of the present invention, when the water content and oxygen content in the raw material are greater than 3 ppm and greater than 3 ppm, the raw material is subjected to dehydration and / or deoxygenation treatment to obtain pretreated raw material for use in the dimerization reaction.

[0061] In this invention, the gas-liquid separation in step (b) aims to separate the reaction mixture into a gas phase and / or a supercritical phase stream and a liquid phase stream. Preferably, the conditions for gas-liquid separation include: a temperature of 50-300°C, more preferably 100-200°C; and a pressure of 4-20 MPa, more preferably 6-12 MPa.

[0062] In some embodiments of the present invention, the conditions for gas-liquid separation are close to the conditions for the dimerization reaction. Preferably, the pressure difference between the gas-liquid separation and the dimerization reaction does not exceed 0.5 MPa, for example, 0 MPa, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, and any value within a range of any two values.

[0063] In this invention, the temperature of the circulating stream is controlled by removing heat from a portion of the gas phase and / or supercritical phase stream, thus preventing the high-temperature gas phase and / or supercritical phase stream from directly returning to step (a) and causing the bed temperature of the reaction unit to runaway. In this way, the reaction temperature is maintained within the range required for the dimerization reaction, thereby achieving high selectivity of the target product.

[0064] In some embodiments of the present invention, the heat treatment in step (c) includes: cooling the portion of the gas phase and / or supercritical phase stream sequentially according to the stream flow direction to obtain a cooled stream, a second pressurization to obtain a pressurized stream, and a second heating to obtain the circulating stream.

[0065] In some embodiments of the present invention, the temperature of the cooled material is 40-150°C, preferably 40-100°C.

[0066] In some embodiments of the present invention, the pressure of the pressurized material is 4-20 MPa, preferably 6-12 MPa.

[0067] In some embodiments of the present invention, 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.

[0068] In some embodiments of the present invention, the temperature of the circulating stream is less than or equal to the temperature of the dimerization reaction. Preferably, the temperature of the circulating stream is 0-80°C lower than the temperature of the dimerization reaction, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 30°C, 50°C, 80°C, and any value within a range of any two of these values, preferably 0-40°C.

[0069] In some embodiments of the invention, the reaction mixture obtained in step (a) comprises: 4-methyl-1-pentene, catalyst powder, light components (e.g., unreacted propylene, coking inhibitor, diluent, C4-C5 fraction), and heavy components (isomers, such as 4-methyl-2-pentene, 1-hexene, and polymers, such as C9). + (Components), etc.

[0070] In some embodiments of the invention, the reaction mixture filtered through a catalyst fine powder contains 30-95 wt% diluent, 1-15 wt% propylene, 4-55 wt% 4-methyl-1-pentene and byproducts, and 0.1-800 ppm (molar concentration relative to the total stream) of coking inhibitor; preferably, it contains 40-85 wt% diluent, 2-10 wt% propylene, 13-50 wt% 4-methyl-1-pentene and byproducts, and 5-500 ppm (molar concentration relative to the total stream) of coking inhibitor. The corresponding circulating stream contains 62-98 wt% diluent, 1-30 wt% propylene, 0.1-3 wt% 4-methyl-1-pentene, and 0.1-1000 ppm (molar concentration relative to the total stream) of coking inhibitor; preferably, it contains 73-98 wt% diluent, 2-25 wt% propylene, 0.1-2 wt% 4-methyl-1-pentene, and 10-600 ppm (molar concentration relative to the total stream) of coking inhibitor.

[0071] In some embodiments of the present invention, the fractionation in step (d) includes, but is not limited to, distillation separation, rectification separation, etc. In some embodiments of the present invention, in addition to fractionation, step (d) may also include separation methods such as extraction separation, adsorption separation, membrane separation, etc., thereby obtaining purified 4-methyl-1-pentene.

[0072] In some embodiments of the present invention, the fractionation includes a first distillation separation and a second distillation separation; wherein the remaining gaseous and / or supercritical phase stream and liquid stream are subjected to the first distillation separation to obtain a light component and a mixed component; the mixed component is subjected to the second distillation separation to obtain 4-methyl-1-pentene and a heavy component.

[0073] In this invention, unless otherwise specified, the feed stream in the fractionation of step (d) includes the remaining gaseous and / or supercritical phase stream and liquid stream.

[0074] In this invention, the light component comprises a diluent, unreacted propylene, a coking inhibitor, and a C4-C5 fraction; the heavy component comprises byproducts (isomers, such as 4-methyl-2-pentene and 1-hexene), and polymers, such as C9... + (Components).

[0075] In some embodiments of the present invention, the pressure of the first distillation separation is 1-3 MPa, for example, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, and any value in any range of any two values, preferably 1.5-2 MPa.

[0076] In some embodiments of the present invention, 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, 0.6 MPa, 0.7 MPa, 0.8 MPa, and any value within the range of any two values, preferably 0.2-0.5 MPa.

[0077] In some embodiments of the present invention, in order to avoid the catalyst fine powder causing blockage in the downstream process and the risk of the catalyst igniting when it comes into contact with water and air during equipment disassembly, the method preferably further includes filtering the reaction mixture obtained in step (a).

[0078] In some embodiments of the invention, the filtration includes a first filtration and / or a second filtration performed after step (a) and before step (b) to obtain a filtered reaction mixture for the gas-liquid separation. Preferably, the precision of the second filtration is less than or equal to the precision of the first filtration.

[0079] In this invention, by setting a first filter and / or a second filter before gas-liquid separation, most of the fine catalyst powder entrained in the reaction mixture can be removed. For example, the amount of fine powder collected at the bottom of the reactor after the reaction is >80%, preferably >90%, and more preferably >95% relative to the catalyst loss. The filtration also avoids clogging of downstream pipelines and equipment by catalyst powder, and the risk of ignition of the active catalyst when exposed to water and air during equipment disassembly and flushing.

[0080] A second aspect of the present invention provides an apparatus for preparing 4-methyl-1-pentene. As shown in FIG1, the apparatus includes a reaction unit II, a gas-liquid separation unit VI, and a fractionation unit III connected in sequence.

[0081] The reaction unit II is used to carry out a dimerization reaction of raw material 4 containing propylene 1, coking inhibitor 2 and optional diluent 3 in the presence of a catalyst to obtain reaction mixture 7;

[0082] The gas-liquid separation unit VI has a gas phase and / or supercritical phase stream outlet and a liquid phase stream outlet, which is used to separate the reaction mixture 7 into gas phase and / or supercritical phase stream 8 and liquid phase stream 9.

[0083] The gas phase and / or supercritical phase stream outlets of the gas-liquid separation unit VI are fluidly connected to the reaction unit II and the fractionation unit III, respectively, for dividing the gas phase and / or supercritical phase stream 8 into two parts 8-i and 8-ii. A heat extraction unit is provided on the pipeline that connects the gas phase and / or supercritical phase stream outlet to the reaction unit II, for heat extraction treatment of part of the gas phase and / or supercritical phase stream 8-i, and then returning it to the reaction unit II as a circulating stream 10.

[0084] The fractionation unit III is used to fractionate the remaining gaseous and / or supercritical phase stream 8-ii with the liquid stream 9 to obtain 4-methyl-1-pentene 14.

[0085] In some embodiments of the present invention, as shown in FIG2, the apparatus further includes a pretreatment unit I disposed upstream of the reaction unit II, for dehydrating and / or deoxygenating the raw material 4 to obtain pretreated raw material 5 for use in the dimerization reaction.

[0086] In some embodiments of the present invention, as shown in Figures 1-2, the apparatus further includes: a first pump IV and a first heater V connected in series in the upstream pipeline of the reaction unit II, or in the pipeline connecting the pretreatment unit I and the reaction unit II, according to the flow direction of the material, for sequentially pressurizing the raw material 4 or the pretreated raw material 5 and heating it in the first pressurization and first heating to obtain the reaction raw material 6.

[0087] In some embodiments of the present invention, as shown in Figures 1-2, the heat extraction unit includes, in accordance with the flow direction of the material, a cooler VII, a second pump VIII, and a second heater IX connected in series, for sequentially cooling, pressurizing, and heating the partial gas phase and / or supercritical phase material 8-i to obtain the circulating material 10.

[0088] In some embodiments of the present invention, the reaction unit includes at least one reactor, preferably 2-6 reactors in series, more preferably 2-4 reactors in series. In the present invention, the reactor includes, but is not limited to, a fixed-bed reactor.

[0089] In some embodiments of the present invention, each of the reactors is provided with a reaction section and a sedimentation and separation section below the reaction section.

[0090] In some embodiments of the present invention, the reaction section is provided with 1-6 catalyst beds, preferably 1-3 catalyst beds.

[0091] In some embodiments of the invention, the circulating stream 10 is returned to the inlet of the reactor, for example above the reaction section or in the pipeline of the reactant 6.

[0092] In some embodiments of the present invention, the reaction unit includes multiple reactors, such as 2-6 reactors in series, or a single reactor is provided with multiple catalyst beds, such as 2-6 catalyst beds. The gas phase and / or supercritical phase stream is sequentially cooled and then pressurized. The pressurized stream is divided into multiple streams, which are then heated and returned to one or more reactors, or one or more catalyst beds in the reactor.

[0093] In some embodiments of the present invention, a first filter element 01 is provided in the sedimentation separation section. The first filter element 01 is used to perform a first filtration on the reaction mixture to obtain a first-filtered reaction mixture 7.

[0094] In some embodiments of the present invention, the first filter element 01 is selected from meshes and / or membranes with a filtration accuracy of ≤15μm, including but not limited to metal meshes, sintered metal powders, ceramic membranes, and polyester filter cartridges.

[0095] In some embodiments of the present invention, as shown in Figures 1-2, the gas-liquid separation unit VI includes at least one liquid separator. Preferably, the liquid separator, for example, is provided with a second filter element 02 in its feed section.

[0096] In some embodiments of the present invention, the second filter element 02 is selected from meshes and / or membranes with a filtration accuracy of ≤15μm, including but not limited to metal meshes, sintered metal powders, ceramic membranes, and polyester filter cartridges.

[0097] In some embodiments of the present invention, the precision of the second filter element 02 is less than or equal to the precision of the first filter element 01.

[0098] In some embodiments of the present invention, as shown in FIG1-2, the fractionation unit III includes a first distillation column III-1 and a second distillation column III-2 connected in series.

[0099] The first distillation column III-1 is used to perform a first distillation separation on the remaining gaseous and / or supercritical phase stream 8-ii and liquid stream 9 as fractionation feed 11 to obtain light component 12 and mixed component 13; the second distillation column III-2 is used to perform a second distillation separation on the mixed component 13 to obtain 4-methyl-1-pentene 14 and heavy component 15.

[0100] In a particularly preferred embodiment of the present invention, a method for preparing 4-methyl-1-pentene is provided, the method comprising:

[0101] (a) A raw material containing propylene, a coking inhibitor and a diluent is subjected to a dimerization reaction in the presence of a catalyst to obtain a reaction mixture;

[0102] (b) The reaction mixture is subjected to gas-liquid separation to obtain a gas phase and / or a supercritical phase stream and a liquid phase stream;

[0103] (c) The gas phase and / or supercritical phase stream is divided into two parts, wherein a portion of the gas phase and / or supercritical phase stream is subjected to heat treatment and then returned to step (a) as a circulating stream.

[0104] (d) Fractionate the remaining gaseous and / or supercritical phase stream with the liquid stream to obtain 4-methyl-1-pentene;

[0105] The diluent is propane; the coking inhibitor is hydrogen.

[0106] The mass ratio of propylene to circulating fluid in the raw material is 1:10-20; the mass ratio of diluent to propylene in the raw material is 0.5-5:1; and the molar concentration of the coking inhibitor is 10-300 ppm based on the propylene in the raw material.

[0107] The present invention also discloses the following embodiments.

[0108] Scheme 1, a method for preparing 4-methyl-1-pentene, characterized in that the method comprises: 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;

[0109] 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.

[0110] Option 2: According to the method described in Option 1, wherein the mass ratio of the raw material to the recycled material, calculated as propylene, is 1:0.1-200, preferably 1:5-80, and more preferably 1:10-20.

[0111] Option 3: The method according to Option 1 or 2, wherein the diluent is selected from alkanes and / or cycloalkanes, preferably from C2-C5 alkanes and / or C3-C6 cycloalkanes, and more preferably from propane and / or n-butane;

[0112] Preferably, the coking inhibitor is selected from hydrogen-containing gases, and more preferably from hydrogen gas;

[0113] Preferably, in the raw materials, the mass ratio of the diluent to propylene is 0-20:1, more preferably 0.5-5:1;

[0114] Preferably, the molar concentration of the coking inhibitor, calculated as hydrogen, in the raw material is 2-1000 ppm, more preferably 10-500 ppm.

[0115] Option 4: The method described in any one of Options 1-3, wherein the water content in the raw material is ≤10ppm, preferably ≤3ppm; and the oxygen content is ≤10ppm, preferably ≤3ppm.

[0116] Preferably, when the water content and oxygen content in the raw material are greater than 3 ppm and greater than 3 ppm, the raw material is subjected to dehydration and / or deoxygenation treatment to obtain pretreated raw material for the dimerization reaction.

[0117] Option 5: The method described in any one of Options 1-4, wherein the conditions for the dimerization reaction are: temperature of 50-300℃, preferably 100-200℃; pressure of 4-20MPa, preferably 6-12MPa;

[0118] Preferably, the bed temperature rise during the dimerization reaction is ≤30℃, more preferably ≤20℃;

[0119] 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.

[0120] Option 6: The method according to any one of Options 1-5, wherein the active metal catalyst is a supported alkali metal catalyst, preferably selected from a supported Na / K catalyst;

[0121] Preferably, based on the total weight of the supported alkali metal catalyst, the alkali metal loading is 0.1-20 wt%, more preferably 1-10 wt%.

[0122] Preferably, the catalyst surface is coated with paraffin wax. Before the dimerization reaction, the reactor is heated and the paraffin wax coating on the catalyst surface is removed under the presence of a diluent medium. The weight of the paraffin wax is 0.01 to 2 times the total weight of the supported alkali metal catalyst, preferably 0.05 to 1 times.

[0123] Option 7: The method described in any one of Options 1-6, wherein the conditions for gas-liquid separation are: temperature of 50-300℃, preferably 100-200℃; pressure of 4-20MPa, preferably 6-12MPa;

[0124] Preferably, the temperature of the recycled material is less than or equal to the temperature of the dimerization reaction;

[0125] More preferably, the temperature of the circulating material is 50-300℃, more preferably 50-200℃;

[0126] 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, pressurized a second time, and heated a second time to obtain the circulating material;

[0127] More preferably, the temperature of the cooled material is 40-150°C, more preferably 40-100°C;

[0128] More preferably, the pressure of the pressurized material is 4-20 MPa, more preferably 6-12 MPa.

[0129] Option 8: The method described in any one of Options 1-7, wherein the distillation separation process comprises a first distillation separation and a second distillation separation;

[0130] 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.

[0131] Preferably, the pressure of the first distillation separation is 1-3 MPa, more preferably 1.5-2 MPa; the pressure of the second distillation separation is 0.2-0.8 MPa, more preferably 0.2-0.5 MPa.

[0132] Preferably, the method further includes: subjecting the dimerization reaction material to a first filtration to obtain the reaction product;

[0133] Preferably, the method further includes: performing gas-liquid separation after passing the reaction product through a second filtration.

[0134] Option 9: An apparatus for preparing 4-methyl-1-pentene, characterized in that the apparatus comprises a reaction unit, a gas-liquid separation unit, and a distillation separation unit connected in sequence;

[0135] 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.

[0136] 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.

[0137] 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.

[0138] Scheme 10: The apparatus according to Scheme 9, wherein the apparatus further includes: a pretreatment unit disposed before the reaction unit, used to dehydrate and / or deoxygenate the raw material to obtain pretreated raw material for the dimerization reaction;

[0139] Preferably, the device further includes: a first pump and a first heater are sequentially arranged on the upstream pipe of the reaction unit or on the pipe connecting the pretreatment unit and the reaction unit according to the material flow direction, for sequentially pressurizing and heating the raw material or the pretreated raw material to obtain the reaction raw material;

[0140] Preferably, according to the material flow direction, the heat extraction unit includes: a cooler, a second pump, and a second heater connected in series, used to sequentially cool, pressurize, and heat the portion of the gaseous / supercritical phase material to obtain the circulating material;

[0141] Preferably, the reaction unit includes at least one reactor in series, more preferably 2-6 reactors in series, and more preferably 2-4 reactors in series.

[0142] Preferably, each reactor is provided with 1-6 catalyst beds, and more preferably 1-3 catalyst beds;

[0143] Preferably, the reactor is provided with a first filter element, and the first filter element is disposed below the catalyst bed;

[0144] Preferably, the gas-liquid separation unit is selected from a separator tank equipped with a second filter element.

[0145] Option 11: The apparatus according to Option 9 or 10, wherein the distillation separation unit is selected from a first distillation separation column and a second distillation separation column connected in series.

[0146] The first distillation column is used to perform a first distillation separation on the remaining gaseous / supercritical phase material and liquid phase material to obtain light components and a mixture; the second distillation column is used to perform a second distillation separation on the mixture to obtain 4-methyl-1-pentene and heavy components.

[0147] To facilitate understanding of the present invention, the following embodiments are provided. However, these embodiments are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0148] Example

[0149] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0150] The present invention will be described in detail below through examples. Unless otherwise specified, all methods used are conventional methods. All reagents used are commercially available and of analytical grade unless otherwise specified. Room temperature refers to approximately 25°C.

[0151] Analysis method:

[0152] Component content analysis was performed by gas chromatography. A PONA column and a flame ionization detector were used, with a detector temperature of 300℃, an injection port temperature of 250℃, and a split ratio of 1:200. The peak area of ​​each component was measured, and the content of each component was calculated using the corrected area normalization method. The content of a component is the ratio of its peak area to the sum of the peak areas of all components.

[0153] The conversion rate is the percentage of propylene content in the inlet stream of the reaction unit compared to the propylene content in the outlet stream of the reaction unit after 12 hours of initial stabilization.

[0154] Selectivity is the percentage of a certain product in the stream at the outlet of the reaction unit relative to the total product in the stream at the outlet of the reaction unit.

[0155] Lifetime is the total operating time of the device when the conversion rate decreases to half of the initial stable conversion rate.

[0156] The temperature rise of the catalyst bed is the ratio of the total heat release to the product of the reactant flow rate and specific heat through the catalyst bed.

[0157] Catalyst loss is the difference between the weight of the catalyst (excluding paraffin) loaded into the reactor and the weight of the catalyst after the reaction.

[0158] Example 1

[0159] The apparatus shown in Figure 2 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 column III-1, and a second distillation column III-2 connected in sequence. The gas phase and / or supercritical phase stream outlet of the gas-liquid separation unit VI is in fluid communication with the reaction unit II and the fractionation unit III, respectively. A cooler VII, a second pump VIII, and a second heater IX are sequentially installed on the pipeline connecting the gas phase and / or supercritical phase stream outlet of the gas-liquid separation unit VI and the reaction unit II, according to the flow direction of the stream.

[0160] Among them, reaction unit II is a fixed-bed reactor with a single catalyst bed in the reaction section. A sedimentation separation section is set below the reaction section of the fixed-bed reactor, which is equipped with a first filter element 01. The shell diameter of the sedimentation separation section is 1.2 times the shell diameter of the reaction section. The feed section of gas-liquid separation unit VI is equipped with a second filter element 02. Both the first filter element 01 and the second filter element 02 are metal filter screens with a filtration accuracy of 10μm.

[0161] A method for preparing 4-methyl-1-pentene in the above-described apparatus, the method comprising:

[0162] (1) The raw material 4 containing propylene 1, hydrogen 2 and propane 3 is dehydrated and deoxygenated to obtain pretreated raw material 5; the molar concentration of hydrogen is 60 ppm based on propylene in the above raw material; 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.

[0163] (2) The pretreated raw material 5 was sequentially pressurized to 10 MPa and heated to 150 °C. The resulting reaction raw material 6 was subjected to a catalyst (catalyst preparation: anhydrous potassium carbonate was sieved, graded, and mixed, then graphite and guar gum powder were added and mixed to form a catalyst, which was then calcined at 500 °C and cooled to 150 °C at a cooling rate of 30-50 °C / h to obtain a catalyst support. Under nitrogen protection, metallic Na and K were added to the support, each with a loading of 3 wt%, and the catalyst was stirred at 350 °C for 4 h to prepare a supported Na / K catalyst. The catalyst surface was coated with paraffin wax, and the weight ratio of paraffin wax to catalyst was 0.2:1. Before the dimerization reaction, the paraffin wax coating on the catalyst surface was removed by purging with a diluent when the reactor was heated.) The resulting reaction mixture 7 was subjected to gas-liquid separation after the first and second filtrations (temperature 150 °C; pressure 10 MPa) to obtain a supercritical phase stream 8 and a liquid stream 9.

[0164] (3) The supercritical phase stream 8 is divided into two parts 8-i and 8-ii. The supercritical phase stream 8-i is cooled to 80°C, pressurized to 10MPa, and heated to 150°C in sequence. It is then returned to the reaction unit II as the circulating stream 10 and carried out the dimerization reaction.

[0165] The mass ratio of propylene 1 to recycled stream 10 in the above raw materials is 1:15;

[0166] The remaining supercritical phase stream 8-ii and liquid phase stream 9 are combined as fractionation feed 11 for the first distillation separation (top pressure 1.8 MPa). The mixed component 13 obtained at the bottom of the column is subjected to the second distillation separation (top pressure 0.3 MPa), and 4-methyl-1-pentene 14 is obtained at the top of the column.

[0167] The temperature rise in the bed during catalyst loading is less than 3°C.

[0168] After the reaction is complete, the amount of fine powder collected at the bottom of the reactor is 97% of the catalyst loss.

[0169] The reaction conditions and results of this embodiment are shown in Table 1 and Table 2, respectively.

[0170] Example 2

[0171] The apparatus of Example 1 is used;

[0172] The method is the same as in Example 1, except that in step (3), the mass ratio of propylene in the raw material to the circulating stream is replaced with 1:10; the other conditions are the same.

[0173] The reaction conditions and results of this embodiment are shown in Table 1 and Table 2, respectively.

[0174] Example 3

[0175] The apparatus of Example 1 is used;

[0176] The method is the same as in Example 1, except that in step (3), the mass ratio of propylene in the raw material to the circulating stream is replaced with 1:50; the other conditions are the same.

[0177] The reaction conditions and results of this embodiment are shown in Table 1 and Table 2, respectively.

[0178] Example 4

[0179] The apparatus of Example 1 is used;

[0180] The method is the same as in Example 1, except that in step (3), the mass ratio of propylene in the raw material to the circulating stream is replaced with 1:100; the other conditions are the same.

[0181] The reaction conditions and results of this embodiment are shown in Table 1 and Table 2, respectively.

[0182] Example 5

[0183] The apparatus of Example 1 is used;

[0184] The method is the same as in Example 1, except that in step (1), the molar concentration of hydrogen, based on propylene in the raw material, is replaced with 20 ppm; the other conditions are the same.

[0185] The reaction conditions and results of this embodiment are shown in Table 1 and Table 2, respectively.

[0186] Example 6

[0187] The apparatus of Example 1 is used;

[0188] The method of Example 1 is followed, except that in step (1), the molar concentration of hydrogen, based on propylene in the raw material, is replaced with 400 ppm; the other conditions are the same.

[0189] The reaction conditions and results of this embodiment are shown in Table 1 and Table 2, respectively.

[0190] Example 7

[0191] The apparatus of Example 1 is used;

[0192] The method is the same as in Example 1, except that propane is not added in step (1); the other conditions are the same.

[0193] The reaction conditions and results of this embodiment are shown in Table 1 and Table 2, respectively.

[0194] Comparative Example 1

[0195] The apparatus of Example 1 is used;

[0196] The method is the same as in Example 1, except that in step (3), the mass ratio of propylene in the raw material to the circulating stream is replaced with 1:1; the other conditions are the same.

[0197] The reaction conditions and results for the comparative example are shown in Table 1 and Table 2, respectively.

[0198] In this comparative example, the reaction could not proceed normally because the bed temperature rise exceeded 100°C.

[0199] Comparative Example 2

[0200] The apparatus of Example 1 is used;

[0201] The method is the same as in Example 1, except that hydrogen is not added in step (1), while the other conditions are the same.

[0202] The reaction conditions and results for the comparative example are shown in Table 1 and Table 2, respectively.

[0203] Comparative Example 3

[0204] The apparatus shown in Figure 3 differs from that in Example 1 in that the gas phase and / or supercritical phase stream outlet of gas-liquid separation unit VI is not connected to reaction unit II.

[0205] The method of Example 1 is different except that in step (1), the mass ratio of propane to propylene in the raw material is replaced with 15:1; in step (3), the supercritical phase stream is not split, but all the supercritical phase stream 8 and liquid stream 9 are combined as fractionation feed 11, and the other conditions are the same.

[0206] The reaction conditions and results for the comparative example are shown in Table 1 and Table 2, respectively.

[0207] Comparative Example 4

[0208] The apparatus shown in Figure 4 differs from that in Example 1 in that the gas phase and / or supercritical phase stream outlet of gas-liquid separation unit VI is not fluidly connected to reaction unit II. The outlet of reaction unit II is fluidly connected to the upper part of the reaction section of reaction unit II and gas-liquid separation unit VI, respectively. According to the flow direction of the stream, a cooler VII, a second pump VIII, and a second heater IX are sequentially installed on the pipeline connecting the outlet of reaction unit II and the upper part of the reaction section.

[0209] The method is the same as in Example 1, except that...

[0210] In step (1), the raw materials do not contain propane;

[0211] In step (2), the reaction mixture 7 after the first filtration is divided into two parts 7-i and 7-ii. Part of the reaction mixture 7-i is successively cooled to 80°C, pressurized to 10MPa, and heated to 150°C to obtain a circulating stream that is returned to reaction unit II.

[0212] The mass ratio of propylene in the raw materials to the recycled stream is 1:15.

[0213] The remaining reaction mixture 7-ii was subjected to gas-liquid separation to obtain a supercritical phase stream and a liquid stream;

[0214] In step (3), all supercritical phase streams and liquid streams are combined as fractionation feed 11, with the other conditions remaining the same.

[0215] The reaction conditions and results for the comparative example are shown in Table 1 and Table 2, respectively.

[0216] Comparative Example 5

[0217] The apparatus used in Comparative Example 4 was employed, except that propane 3 was added to raw material 4 as a diluent.

[0218] The method is the same as in Comparative Example 4, except that in step (1), the raw materials contain propane, and the mass ratio of propane to propylene is 1:1, while the other conditions are the same.

[0219] The reaction conditions and results for the comparative example are shown in Table 1 and Table 2, respectively.

[0220] Comparative Example 6

[0221] The device shown in Figure 5 differs from the device in Embodiment 1 in that, according to the flow direction of the material, the second pump VIII and the second heater IX are not installed downstream of the cooler VII on the circulating material pipeline, and the downstream outlet pipeline of the cooler VII is connected to the upstream of the first pump IV.

[0222] The method of Example 1 is different in that, in step (3), the supercritical phase stream is divided into two parts. One part of the supercritical phase stream is cooled to 80°C and then returned to the pipeline upstream of reaction unit II as a circulating stream 10 to be combined with the pretreated raw material 5. After being pressurized to 10MPa and heated to 150°C, it undergoes a dimerization reaction.

[0223] The conversion rate and selectivity of the reaction in Comparative Example 6 were comparable to those in Example 1, but the energy consumption was 2115 kJ / kg, which was significantly higher than that of Example 1.

[0224] Table 1 Note: 1- Molar concentration of hydrogen in ppm, based on propylene in the feedstock; 2- Mass ratio of propane to propylene in the feedstock; 3- Mass ratio of propylene in the feedstock to the recycled stream.

[0225] Table 2 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.

[0226] As shown in Tables 1 and 2, compared to Comparative Example 1, the embodiments of the present invention, by adjusting the mass ratio of propylene in the raw materials to the circulating stream, can control the bed temperature rise with low energy consumption, prevent bed overheating, and help maintain the reaction temperature within the range required for the dimerization reaction, allowing the reaction to proceed normally. Controlling the bed temperature rise improves the selectivity of 4M1P.

[0227] Compared to Comparative Example 2, the embodiment of the present invention adds hydrogen to the raw material as a coking inhibitor, which effectively improves the selectivity of 4M1P and extends the operating cycle.

[0228] By comparing Example 1 and Comparative Example 3, it can be seen that the process of recycling part of the supercritical stream back to the reactor without setting up a gas-liquid separator, and instead increasing the proportion of propane in the feedstock, achieves a 4M1P selectivity comparable to that of Example 1; however, the energy consumption of Comparative Example 3 is significantly increased.

[0229] Comparing Examples 1 and 7, it can be seen that under the condition of setting up a material heat recovery cycle, adding a certain amount of diluent can further wash away the polymers attached to the active centers on the catalyst surface, reduce the temperature rise with lower energy consumption, and improve the selectivity of 4M1P.

[0230] By comparing Example 1 and Comparative Example 5 or Example 7 and Comparative Example 4, it can be seen that, compared with the process of Comparative Example 4-5 in which a portion of the reactant stream is diverted out at the outlet of the reaction unit and recycled back to the reactor, the embodiments of the present invention have higher selectivity and longer operating cycle under the premise of comparable energy consumption.

[0231] By comparing Example 1 and Comparative Example 6, it can be seen that by recycling a portion of the supercritical phase stream back to the reaction unit after heat extraction, instead of recycling it back to the upstream pipeline of the reaction unit after cooling, and combining it with the pretreated raw materials for the first pressurization and first heating, energy consumption can be significantly reduced.

[0232] The data from the above embodiments and comparative examples show that the present invention can effectively control propylene conversion rate, 4M1P selectivity, process energy consumption and operating cycle by optimizing the mass ratio of diluent to propylene in the raw materials, the mass ratio of propylene to the circulating stream, the molar concentration of coking inhibitor in the raw materials and a specific process flow. Thus, even under conditions of high conversion rate, it can still achieve efficient temperature control, high 4M1P selectivity and long cycle operation with low energy consumption.

[0233] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing 4-methyl-1-pentene, characterized in that, The method includes: (a) A feedstock comprising propylene, a coking inhibitor, and optionally a diluent is subjected to a dimerization reaction in the presence of a catalyst to obtain a reaction mixture. (b) The reaction mixture is subjected to gas-liquid separation to obtain a gas phase and / or a supercritical phase stream and a liquid phase stream; (c) The gaseous and / or supercritical phase stream is divided into two parts, wherein a portion of the gaseous and / or supercritical phase stream is subjected to heat treatment and returned to step (a) as a circulating stream, wherein the mass ratio of propylene in the raw material to the circulating stream is ≤1:5, preferably 1:10-80, more preferably 1:10-20. (d) Fractionate the remaining gaseous and / or supercritical phase stream with the liquid stream to obtain 4-methyl-1-pentene.

2. The method according to claim 1, wherein, The diluent is selected from C2-C6 alkanes and mixtures thereof, preferably from C2-C5 alkanes, C3-C6 cycloalkanes and mixtures thereof, and more preferably from propane, n-butane and mixtures thereof; Preferably, the coking inhibitor contains hydrogen gas; Preferably, the mass ratio of the diluent to propylene in the raw material is 0-20:1, more preferably 0.5-5:1; Preferably, based on the propylene content in the raw material, the molar concentration of the coking inhibitor is 2-1000 ppm, more preferably 10-300 ppm.

3. The method according to claim 1 or 2, wherein, The conditions for the dimerization reaction include: a temperature of 50-300℃, preferably 100-200℃; and a pressure of 4-20MPa, preferably 6-12MPa. Preferably, the bed temperature rise during the dimerization reaction is ≤30℃, more preferably ≤20℃; 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 raw material for use in the dimerization reaction.

4. The method according to any one of claims 1-3, wherein, The catalyst is a supported alkali metal catalyst, preferably a supported Na / K catalyst; Preferably, based on the total weight of the supported alkali metal catalyst, the alkali metal loading is 0.1-20 wt%, more preferably 1-10 wt%. Preferably, the catalyst surface is coated with paraffin wax, and the paraffin wax coating on the catalyst surface is removed by purging with the diluent when the reactor is heated before the dimerization reaction; the mass ratio of the paraffin wax to the supported alkali metal catalyst is 0.01-2:1, preferably 0.05-1:

1.

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

6. The method according to any one of claims 1-5, wherein, The conditions for gas-liquid separation include: a temperature of 50-300℃, preferably 100-200℃; and a pressure of 4-20MPa, preferably 6-12MPa. Preferably, the heat treatment includes: cooling a portion of the gas phase and / or supercritical phase stream sequentially according to the stream flow direction to obtain a cooled stream, a second pressurization, a pressurized stream, and a second heating to obtain the circulating stream; More preferably, the temperature of the cooled material is 40-150°C, more preferably 40-100°C; More preferably, the pressure of the pressurized material is 4-20 MPa, more preferably 6-12 MPa; Preferably, the temperature of the circulating fluid is 50-300℃, and more preferably 50-200℃; Preferably, the temperature of the circulating material is less than or equal to the temperature of the dimerization reaction; more preferably, the temperature of the circulating material is 0-80°C lower than the temperature of the dimerization reaction, more preferably 0-40°C.

7. The method according to any one of claims 1-6, wherein, The fractionation includes a first distillation separation and a second distillation separation; The remaining gaseous and / or supercritical phase and liquid phase streams are subjected to the first distillation separation to obtain light components and mixed components; the mixed components are subjected to the second distillation separation to obtain 4-methyl-1-pentene and heavy components. Preferably, the pressure of the first distillation separation is 1-3 MPa, more preferably 1.5-2 MPa; the pressure of the second distillation separation is 0.2-0.8 MPa, more preferably 0.2-0.5 MPa. Preferably, the method further includes filtering the reaction mixture obtained in step (a); More preferably, the filtration includes: a first filtration and / or a second filtration performed after step (a) and before step (b) to obtain a filtered reaction mixture for the gas-liquid separation, preferably, the precision of the second filtration is less than or equal to the precision of the first filtration.

8. An apparatus for preparing 4-methyl-1-pentene, characterized in that, The device includes a reaction unit, a gas-liquid separation unit, and a fractionation unit connected in sequence. The reaction unit is used to carry out a dimerization reaction of a raw material containing propylene, a coking inhibitor and an optional diluent in the presence of a catalyst to obtain a reaction mixture; The gas-liquid separation unit has a gas phase and / or supercritical phase stream outlet and a liquid phase stream outlet, which is used to separate the reaction mixture into gas phase and / or supercritical phase stream and liquid phase stream. The gas phase and / or supercritical phase stream outlets of the gas-liquid separation unit are fluidly connected to the reaction unit and the fractionation unit, respectively. A heat extraction unit is provided on the pipeline that connects the gas phase and / or supercritical phase stream outlets to the reaction unit, which is used to perform heat extraction on a portion of the gas phase and / or supercritical phase stream and then return it to the reaction unit as a circulating stream. The fractionation unit is used to fractionate the remaining gaseous and / or supercritical phase stream with the liquid stream to obtain 4-methyl-1-pentene.

9. The apparatus according to claim 8, wherein, The apparatus further includes a pretreatment unit disposed upstream of the reaction unit, used to dehydrate and / or deoxygenate the raw material to obtain pretreated raw material for use in the dimerization reaction.

10. The apparatus according to claim 8 or 9, wherein, The apparatus further includes a first pump and a first heater connected in series in the upstream pipeline of the reaction unit or in the pipeline connecting the pretreatment unit and the reaction unit, according to the flow direction of the material, for sequentially pressurizing and heating the raw material or the pretreated raw material to obtain the reaction raw material.

11. The apparatus according to any one of claims 8-10, wherein, According to the flow direction of the logistics, the heat extraction unit includes: a cooler, a second pump, and a second heater connected in series, used to sequentially cool, pressurize, and heat the partial gas phase and / or supercritical phase logistics to obtain the circulating logistics.

12. The apparatus according to any one of claims 8-11, wherein, The reaction unit includes at least one reactor, preferably 2-6 reactors in series, and more preferably 2-4 reactors in series. Each reactor is provided with a reaction section and a sedimentation and separation section below the reaction section; The reaction section is provided with 1-6 catalyst beds, preferably 1-3 catalyst beds; Preferably, the sedimentation separation section is provided with a first filter element; preferably, the filtration accuracy of the first filter element is ≤15μm; Preferably, the shell diameter ratio of the sedimentation separation section to the reaction section is 1-1.5:

1.

13. The apparatus according to any one of claims 8-12, wherein, The gas-liquid separation unit includes at least one liquid separator. Preferably, the separator is provided with a second filter element; preferably, the filtration accuracy of the second filter element is ≤15μm; preferably, the accuracy of the second filter element is less than or equal to the accuracy of the first filter element.

14. The apparatus according to any one of claims 8-13, wherein, The fractionation unit includes a first distillation column and a second distillation column connected in series. The first distillation column is used to perform a first distillation separation on the remaining gaseous and / or supercritical phase stream and liquid stream to obtain light components and mixed components; the second distillation column is used to perform a second distillation separation on the mixed components to obtain 4-methyl-1-pentene and heavy components.

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