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

Abstract

The invention relates to the technical field of propylene dimerization, in particular to a method and device for preparing 4-methyl-1-pentene through propylene dimerization, and the method comprises the following steps: (1) pretreating a raw material containing propylene and a coking inhibitor to obtain a pretreated raw material; (2) in a non-oxidizing atmosphere, contacting the pretreated raw materials with a catalyst and carrying out dimerization reaction to obtain reaction materials which are divided into a part of reaction materials and a residual part of reaction materials; (3) carrying out rectification separation on the rest reaction material to obtain 4-methyl-1-pentene; wherein the partial reaction materials are recycled for the dimerization reaction after being subjected to heat removal. According to the method provided by the invention, the multimerization reaction is avoided by regulating and controlling the temperature of the dimerization reaction, so that the selectivity of the 4-methyl-1-pentene and the activity of the catalyst are improved.

Description

Technical Field

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

[0002] 4-Methyl-1-pentene (4M1P) is an important polymerization monomer that can be used as a copolymer of ethylene and propylene. It can improve the transparency and environmental stress resistance of polyolefins. It can also be homopolymerized into thermoplastics to prepare poly-4-methyl-1-pentene (PMP) with excellent performance.

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

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

[0005] On the other hand, the preparation of 4-methyl-1-pentene by propylene dimerization is an exothermic reaction with a large heat release, and the reaction temperature is difficult to control, and the conversion rate and selectivity are sensitive to the reaction temperature. Therefore, it is necessary to remove the reaction heat in time to maintain a stable reaction temperature, reduce the occurrence of side reactions, and improve the selectivity of the target product. CN202010495971.3 discloses a method for synthesizing 4-methyl-1-pentene, in which propylene is added to a reaction unit after dehydration and deoxygenation to carry out dimerization and isomerization, and then the unreacted raw materials are returned to the reaction unit for circulation after gas-liquid separation, but a large amount of unreacted raw materials are separated and recycled by distillation, and the energy consumption is very high.

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

[0007] The purpose of the present invention is to overcome the above technical problems and provide a method for preparing 4-methyl-1-pentene by propylene dimerization and a device for preparing 4-methyl-1-pentene by propylene dimerization. The method provided by the present invention avoids the occurrence of polymerization reaction by regulating the dimerization reaction temperature, thereby improving the selectivity of 4-methyl-1-pentene and the activity of the catalyst.

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

[0009] (1) pretreating a raw material containing propylene and a coking inhibitor to obtain a pretreated raw material;

[0010] (2) contacting the pretreated raw material with a catalyst in a non-oxidizing atmosphere and performing a dimerization reaction, and the obtained reaction material is divided into a partial reaction material and a remaining partial reaction material;

[0011] (3) subjecting the remaining reaction material to distillation separation to obtain 4-methyl-1-pentene;

[0012] Wherein, part of the reaction material is recycled to the dimerization reaction after heat removal.

[0013] Preferably, the mass ratio of the part of the reaction material to the remaining part of the reaction material is 1-200:1, preferably 1-80:1, and more preferably 10-50:1.

[0014] Preferably, the heat extraction process comprises: sequentially cooling, pressurizing and heating the part of the reaction material to obtain a circulating reaction material.

[0015] Preferably, in step (1), the molar concentration of the coking inhibitor in the raw material calculated as propylene is 2-1000 ppm, preferably 10-500 ppm, more preferably 30-300 ppm.

[0016] The second aspect of the present invention provides a device for preparing 4-methyl-1-pentene by propylene dimerization, the device comprising a pretreatment unit, a reaction unit and a distillation separation unit connected in sequence;

[0017] The pretreatment unit is used to pretreat the raw material containing propylene and the coking inhibitor to obtain the pretreated raw material; the reaction unit is used to dimerize the pretreated raw material and the catalyst in a non-oxidizing atmosphere to separate the obtained reaction material into a part of the reaction material and the remaining part of the reaction material; the distillation and separation unit is used to distill and separate the remaining part of the reaction material to obtain 4-methyl-1-pentene;

[0018] Wherein, according to the material flow direction, a heat extraction unit is provided on the circulation pipeline at the outlet and the inlet of the reaction unit, for recycling part of the reaction material to the reaction unit after heat extraction.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The method provided by the present invention improves the selectivity of 4-methyl-1-pentene and the activity of the catalyst by adding a coking inhibitor to the raw material and inhibiting the occurrence of the polymerization reaction; at the same time, a portion of the reaction material is limited to be reused in the dimerization reaction after heat extraction, and in particular, the total temperature rise of the dimerization reaction is ≤60°C by regulating the circulation ratio of the reaction material, thereby improving the selectivity of 4-methyl-1-pentene;

[0021] (2) The present invention limits the recycling of part of the reaction materials, eliminating the need for distillation, separation and recycling of a large amount of materials, thereby significantly reducing energy consumption;

[0022] (3) The method provided by the present invention also performs a first filtration on the dimerization reaction materials and a second filtration on the remaining reaction materials before distillation separation to remove a small amount of catalyst mixed in the reaction materials, thereby avoiding the risk of the catalyst catching fire when it comes into contact with water and air once the subsequent pipelines and pipes are blocked by the catalyst and are disassembled and flushed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of a device for preparing 4-methyl-1-pentene by propylene dimerization provided by the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of a device for preparing 4-methyl-1-pentene by propylene dimerization provided in Comparative Example 1.

[0025] Description of Reference Numerals

[0026] I. Pretreatment unit; II. Reaction unit; III. Filtration unit; IV. Distillation separation unit; IV-1. First distillation separation tower; IV-2. Second distillation separation tower; V. Cooler; VI. Pump; VII. Heater; 01. First filtering component; 02. Second filtering component; 03. Water injection port; 04. Heat extraction coil; 1. Propylene; 2. Coking inhibitor; 3. Raw materials; 4. Raw materials after pretreatment; 5. Reaction materials; 5-i. Part of the reaction materials; 5-ii. The remaining part of the reaction materials; 6. The filtered materials; 7. Light components; 8-Mixed materials; 9. 4-methyl-1-pentene; 10. Heavy impurities; 11. Circulating reaction materials. DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] Unless otherwise specified, "first" and "second" do not indicate a sequence or limit to the materials or steps, but are only used to distinguish or indicate that they are not the same materials or steps. For example, in "first filtration" and "second filtration", "first" and "second" are only used to indicate that they are not the same filtration.

[0029] A first aspect of the present invention provides a method for preparing 4-methyl-1-pentene by dimerization of propylene, the method comprising:

[0030] (1) pretreating a raw material containing propylene and a coking inhibitor to obtain a pretreated raw material;

[0031] (2) contacting the pretreated raw material with a catalyst in a non-oxidizing atmosphere and performing a dimerization reaction, and the obtained reaction material is divided into a partial reaction material and a remaining partial reaction material;

[0032] (3) subjecting the remaining reaction material to distillation separation to obtain 4-methyl-1-pentene;

[0033] Wherein, part of the reaction material is recycled to the dimerization reaction after heat removal.

[0034] The inventor of the present invention has found that compared with the existing method of propylene dimerization 4-methyl-1-pentene, there are defects such as easy polymerization reaction to generate polymer products during the reaction process, difficult to control the reaction temperature, and the risk of ignition when the catalyst powder is blocked with the material to the downstream. The present invention adds a coking inhibitor to the raw material, inhibits the occurrence of polymerization reaction, prevents the catalyst from coking, thereby improving the selectivity of 4-methyl-1-pentene and extending the life of the catalyst; at the same time, by limiting the recycling of part of the reaction materials after heat extraction, on the one hand, the temperature rise of the dimerization reaction is regulated, thereby improving the selectivity of 4-methyl-1-pentene; on the other hand, by reducing the amount of material separated by distillation, the reaction energy consumption is reduced. In particular, the present invention limits the circulation ratio of the reaction materials so that the total temperature rise of the dimerization reaction is ≤60°C, which more effectively improves the selectivity of 4-methyl-1-pentene.

[0035] In the present invention, unless otherwise specified, the reaction materials include: 4-methyl-1-pentene, catalyst fine powder, light components (e.g., unreacted propylene, coking inhibitor), heavy impurities (polymerization products, e.g., C 9+ )wait.

[0036] In some embodiments of the present invention, preferably, the mass ratio of the part of the reaction material to the remaining part of the reaction material is 1-200: 1, for example, 1: 1, 10: 1, 15: 1, 20: 1, 30: 1, 50: 1, 60: 1, 80: 1, 100: 1, 150: 1, 200: 1, and any value in the range of any two numerical values, preferably 1-80: 1, more preferably 10-50: 1. In the present invention, the mass ratio of the part of the reaction material to the remaining part of the reaction material is also the circulation ratio of the reaction material. In the present invention, satisfying the circulation ratio in the above range is conducive to improving the selectivity of 4-methyl-1-pentene.

[0037] In some embodiments of the present invention, preferably, the heat extraction process comprises: cooling, pressurizing and heating the part of the reaction material in sequence to obtain a circulating reaction material. In the present invention, the cooling is intended to condense and cool the part of the reaction material, the pressurizing is intended to provide power for the reaction material to return to the reactor inlet, and the heating is intended to bring the pressurized material to the return temperature of the circulating reaction material.

[0038] In some embodiments of the present invention, preferably, the temperature of the circulating reaction material is 0-100° C. lower than the inlet temperature of the dimerization reaction, for example, 0° C., 10° C., 20° C., 30° C., 40° C., 50° C., 60° C., 80° C., 100° C., and any value in the range of any two values, preferably 0-60° C. When the above range is met, the temperature of the circulating reaction material is regulated to reduce the temperature of the raw material, thereby improving the selectivity of 4-methyl-1-pentene.

[0039] In some embodiments of the present invention, preferably, the temperature of the cooled material is 40-300°C, for example, 40°C, 50°C, 60°C, 80°C, 100°C, 120°C, 150°C, 200°C, 300°C, and any value in the range consisting of any two values, preferably 40-150°C.

[0040] In some embodiments of the present invention, preferably, the pressure of the pressurized material is 4-20MPa, for example, 4MPa, 6MPa, 8MPa, 10MPa, 12MPa, 15MPa, 20MPa, and any value in the range of any two values, preferably 6-12MPa. In the present invention, the pressure is absolute pressure.

[0041] In some embodiments of the present invention, preferably, the molar concentration of the coking inhibitor in the raw material calculated as propylene is 2-1000ppm, for example, 2ppm, 10ppm, 30ppm, 50ppm, 100ppm, 200ppm, 300ppm, 500ppm, 1000ppm, and any value in the range consisting of any two values, preferably 10-500ppm, more preferably 30-300ppm. When the above molar concentration ratio range is met, the selectivity of 4-methyl-1-pentene is more effectively improved by inhibiting the occurrence of polymerization reaction and preventing catalyst coking.

[0042] In some embodiments of the present invention, preferably, the coking inhibitor is selected from hydrogen.

[0043] In some embodiments of the present invention, preferably, the purity of the propylene is ≥ 80 wt%, preferably ≥ 95 wt%.

[0044] In some embodiments of the present invention, preferably, the pretreatment process includes: dehydrating and deoxygenating the raw material; further preferably, the water content in the raw material after the pretreatment is ≤10ppm, and the oxygen content is ≤10ppm; more preferably, the water content in the raw material after the pretreatment is ≤3ppm, and the oxygen content is ≤3ppm.

[0045] In the present invention, the type of the catalyst has a wide selection range. Preferably, the catalyst is selected from a supported alkali metal catalyst, preferably a supported Na / K catalyst; the carrier of the supported alkali metal catalyst is selected from at least one of alkali metal carbonate, molecular sieve and activated carbon, preferably selected from alkali metal carbonate, and the alkali metal carbonate is selected from sodium carbonate and / or potassium carbonate.

[0046] In some embodiments of the present invention, preferably, based on the total weight of the supported alkali metal catalyst, the alkali metal loading is 0.1-20wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 5wt%, 10wt%, 20wt%, and any value in the range consisting of any two values, preferably 1-10wt%.

[0047] In some embodiments of the present invention, preferably, 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.

[0048] In some embodiments of the present invention, it is further preferred that the radial temperature difference of the dimerization reaction is ≤10°C / m, preferably ≤5°C / m, and more preferably ≤2°C / m. In the present invention, the radial temperature difference is the ratio of the absolute value of the temperature difference between the center and the edge of the reactor cross section to the radius.

[0049] In some embodiments of the present invention, preferably, the total reaction temperature rise of the dimerization reaction is ≤60° C., preferably ≤30° C. In the present invention, the total reaction temperature rise refers to the sum of the temperature rises of each catalyst bed, ℃.

[0050] In some embodiments of the present invention, it is further preferred that the temperature rise of a single catalyst bed in the dimerization reaction is ≤30° C., preferably ≤15° C. In the present invention, the temperature rise of a single catalyst bed refers to the difference between the discharge temperature and the feed temperature of each catalyst bed, ℃.

[0051] In the present invention, the distillation separation is intended to distill and separate the remaining part of the reaction materials to obtain not only 4-methyl-1-pentene, but also light components rich in coking inhibitors and unreacted propylene and heavy impurities rich in by-products.

[0052] In some embodiments of the present invention, preferably, in step (3), the distillation separation process includes: a first distillation separation and a second distillation separation; wherein the remaining part of the reaction material is subjected to the first distillation separation to obtain a light component and a mixed material; and the mixed material is subjected to the second distillation separation to obtain 4-methyl-1-pentene and heavy impurities.

[0053] In some embodiments of the present invention, it is further preferred that the top pressure of the first distillation separation is 1-3 MPa, preferably 1.5-2 MPa; the top pressure of the second distillation separation is 0.2-0.8 MPa, preferably 0.2-0.5 MPa.

[0054] In the present invention, in order to avoid the blockage of catalyst fine powder in the downstream process and the fire risk when the device is disassembled and encounters water and air, preferably, the dimerization reaction material is first filtered to remove the catalyst fine powder mixed in the dimerization reaction material, and the obtained reaction material is divided into two parts, that is, part of the reaction material and the remaining part of the reaction material.

[0055] In some embodiments of the present invention, preferably, before the distillation separation, the remaining portion of the reaction material is subjected to a second filtration to further remove the catalyst fine powder remaining in the remaining portion of the reaction material to obtain a filtered material.

[0056] In some embodiments of the present invention, preferably, after the second filtration, the remaining reaction material is washed with water. This arrangement is intended to deactivate the catalyst fine powder remaining in the remaining reaction material and avoid the risk of fire when the device is disassembled due to water and air.

[0057] In some embodiments of the present invention, preferably, during the water washing process, the mass ratio of the remaining reaction material to water is 100:0.01-10, for example, 100:0.01, 100:0.05, 100:0.1, 100:0.2, 100:0.5, 100:1, 100:5, 100:10, and any value in the range composed of any two values, preferably 100:0.01-1.

[0058] The second aspect of the present invention provides a schematic diagram of the structure of a device for preparing 4-methyl-1-pentene by propylene dimerization. Figure 1 As shown by Figure 1 It can be seen that the device comprises a pretreatment unit I, a reaction unit II and a distillation separation unit IV which are connected in sequence;

[0059] The pretreatment unit I is used to pretreat the raw material 3 containing propylene 1 and the coking inhibitor 2 to obtain the pretreated raw material 4; the reaction unit II is used to dimerize the pretreated raw material 4 and the catalyst in a non-oxidizing atmosphere to obtain a reaction material 5-i and a remaining reaction material 5-ii; the distillation and separation unit IV is used to distill and separate the remaining reaction material 5-ii to obtain 4-methyl-1-pentene 9;

[0060] Wherein, according to the material flow direction, a heat extraction unit is provided on the circulation pipeline at the outlet and the inlet of the reaction unit II, for recycling part of the reaction material 5 - i to the reaction unit II after heat extraction.

[0061] In the present invention, Figure 1 As shown, the heat extraction unit includes: a cooler V, a pump VI and a heater VII which are connected in sequence and are respectively used to cool, pressurize and heat the part of the reaction material 5 - i in sequence to obtain a circulating reaction material 11 .

[0062] In some embodiments of the present invention, preferably, the reaction unit comprises at least one reactor connected in series, preferably 2-6 reactors connected in series, more preferably 2-4 reactors connected in series. In the present invention, the reactor includes but is not limited to a fixed bed reactor.

[0063] In some embodiments of the present invention, preferably, each of the reactors is provided with 1 to 6 catalyst beds, preferably 1 to 3 catalyst beds.

[0064] In a first specific embodiment of the present invention, Figure 1As shown, the reaction unit II is selected from a fixed bed reactor containing one catalyst bed layer, and a cooler V, a pump VI and a heater VII are sequentially arranged on the circulation pipelines at the outlet and the inlet of the fixed bed reactor.

[0065] In a second specific embodiment of the present invention, when the reaction unit contains at least one reactor with a single catalyst bed connected in series, a cooler, a pump and a heater are sequentially arranged on the circulation pipeline connecting the outlet and the inlet of the reaction unit according to the material flow direction, so as to cool, pressurize and heat part of the reaction materials in sequence, and then return them to each reactor through the circulation branch pipe; or; a cooler and a pump are sequentially arranged on the circulation pipeline connecting the outlet and the inlet of the reaction unit, and a heater is arranged on the circulation branch pipe, so as to cool and pressurize part of the reaction materials in sequence, and then return them to each reactor through the circulation branch pipe after being heated respectively.

[0066] In a second specific embodiment of the present invention, when the reaction unit is selected from a reactor containing 2-6 catalyst beds, a cooler, a pump and a heater are sequentially arranged on the circulation pipeline connecting the outlet and the inlet of the reactor according to the material flow direction, so as to cool, pressurize and heat part of the reaction materials in sequence, and then return them to each catalyst bed through the circulation branch; or; a cooler and a pump are sequentially arranged on the circulation pipeline connecting the outlet and the inlet of the reactor, and a heater is arranged on the circulation branch, so as to cool and pressurize part of the reaction materials in sequence, and then return them to each catalyst bed through the circulation branch after being heated respectively.

[0067] In some embodiments of the present invention, preferably, Figure 1 As shown, the reactor is provided with a first filter component 02, and the first filter component 02 is arranged below the catalyst bed layer, and is used to perform a first filtration on the dimerization reaction material, and the obtained reaction material is divided into a partial reaction material 5-i and a remaining partial reaction material 5-ii. In the present invention, the first filter component is arranged below the last catalyst bed layer from top to bottom in the reactor.

[0068] In the present invention, the first filter component 01 is selected from a mesh and / or membrane with a filtering accuracy of ≤15 μm, including but not limited to a metal mesh, a sintered metal powder, a ceramic membrane, and a polyester filter element.

[0069] In some embodiments of the present invention, preferably, Figure 1As shown, the distillation separation unit IV includes: a first distillation separation tower IV-1 and a second distillation separation tower IV-2 connected in series, the first distillation separation tower IV-1 is used to perform a first distillation separation on the remaining part of the reaction material 5-ii, and a light component 7 is obtained at the top of the tower, and a mixed material 8 is obtained in the bottom of the tower; the second distillation separation tower IV-2 is used to perform a second distillation separation on the mixed material 8, and 4-methyl-1-pentene 9 is obtained at the top of the tower, and a heavy impurity 10 is obtained in the bottom of the tower.

[0070] In some embodiments of the present invention, preferably, Figure 1 As shown, the device further includes: a filtering unit III connected to the reaction unit II and the distillation separation unit IV, for performing a second filtration on the remaining portion of the reaction material 5-ii to obtain a filtered material 6.

[0071] In some embodiments of the present invention, preferably, Figure 1 As shown, the filter unit III is provided with a second filter component 02. In the present invention, the second filter component 02 is selected from a mesh and / or membrane with a filtering accuracy of ≤15 μm, including but not limited to a metal mesh, metal powder sintering, ceramic membrane, polyester filter element, etc.

[0072] In some embodiments of the present invention, preferably, Figure 1 As shown, a water injection port 03 is provided on the pipeline connecting the filtering unit III and the distillation separation unit IV, which is used to contact the filtered material 6 with water and wash it with water.

[0073] According to a particularly preferred embodiment of the present invention, a method for preparing 4-methyl-1-pentene by dimerization of propylene comprises:

[0074] (1) pretreating a raw material containing propylene and a coking inhibitor to obtain a pretreated raw material;

[0075] (2) contacting the pretreated raw material with a catalyst in a non-oxidizing atmosphere and performing a dimerization reaction, and the obtained reaction material is divided into a partial reaction material and a remaining partial reaction material;

[0076] (3) subjecting the remaining reaction material to a first distillation separation to obtain a light component and a mixed material; subjecting the mixed material to a second distillation separation to obtain 4-methyl-1-pentene;

[0077] wherein the part of the reaction material is sequentially cooled, pressurized and heated to obtain a circulating reaction material which is recycled for the dimerization reaction; the temperature of the circulating reaction material is 0-60° C. lower than the inlet temperature of the dimerization reaction;

[0078] Wherein, the mass ratio of the part of the reaction material to the remaining part of the reaction material is 10-50:1;

[0079] Wherein, the molar concentration of the coking inhibitor in the raw material calculated as propylene is 30-300 ppm.

[0080] The present invention will be described in detail below through examples.

[0081] Some process parameters and test results of Examples 1-8 and Comparative Examples 1-3 are listed in Table 1.

[0082] Example 1

[0083] The device for preparing 4-methyl-1-pentene by propylene dimerization is as follows: Figure 1 As shown by Figure 1 It can be seen that the device includes: a pretreatment unit I, a reaction unit II, a filtering unit III and a distillation separation unit IV connected in sequence; the reaction unit II and the filtering unit III are respectively provided with a first filtering component 01 and a second filtering component 02; a water injection port 03 is provided on the pipeline connecting the filtering unit III and the distillation separation unit IV;

[0084] Wherein, the reaction unit II is selected from a fixed bed reactor with a single catalyst bed, and the circulation pipelines at the outlet and inlet of the fixed bed reactor are provided with a cooler V, a pump VI and a heater VII;

[0085] Wherein, the first filter component 01 and the second filter component 02 are both selected from metal filter meshes with a filtering accuracy of 10 μm; the distillation separation unit IV comprises: a first distillation separation tower IV-1 and a second distillation separation tower IV-2 connected in series.

[0086] The method for preparing 4-methyl-1-pentene by propylene dimerization is carried out in the above-mentioned device, and the method comprises:

[0087] (1) pretreating a raw material containing propylene and hydrogen to obtain a pretreated raw material;

[0088] The purity of the propylene is 95 wt %, the concentration of hydrogen in the raw material is 70 ppm; the water content in the raw material after the pretreatment is 2.5 ppm, and the oxygen content is 2.3 ppm;

[0089] (2) in a nitrogen atmosphere, the pretreated raw material and the catalyst are contacted and a dimerization reaction is carried out (temperature is 150° C., pressure is 10 MPa), and the obtained dimerization reaction material is filtered for the first time, and the obtained reaction material is divided into a partial reaction material and a remaining reaction material with a mass ratio of 20:1; the catalyst is a supported Na / K catalyst, the Na / K loading amount is 6wt%, and the carrier is potassium carbonate;

[0090] (3) The remaining reaction material is subjected to a second filtration, the filtered material is mixed with water at a mass ratio of 100:0.01 and washed with water, and then subjected to a first distillation separation (the tower top pressure is 1.8 MPa), and the mixed material obtained at the bottom of the tower is subjected to a second distillation separation (the tower top pressure is 0.3 MPa) to obtain 4-methyl-1-pentene;

[0091] (4) After cooling the above part of the reaction material, the cooled material with a temperature of 80° C. is pressurized to 10 MPa, and then heated to 150° C., and the obtained circulating reaction material is reused in the above dimerization reaction.

[0092] Example 2

[0093] According to the device provided in Example 1;

[0094] According to the method provided in Example 1, the difference is that in step (1),

[0095] The concentration of hydrogen in the above raw materials was adjusted to 200 ppm, and the other conditions were the same to obtain 4-methyl-1-pentene.

[0096] Example 3

[0097] According to the device provided in Example 1;

[0098] According to the method provided in Example 1, the difference is that in step (1),

[0099] The concentration of hydrogen in the above raw materials was adjusted to 600 ppm, and the other conditions were the same to obtain 4-methyl-1-pentene.

[0100] Example 4

[0101] According to the device provided in Example 1;

[0102] According to the method provided in Example 1, the difference is that in step (1),

[0103] The concentration of hydrogen in the above raw materials was adjusted to 1100 ppm, and the other conditions were the same to obtain 4-methyl-1-pentene.

[0104] Example 5

[0105] According to the device provided in Example 1;

[0106] According to the method provided in Example 1, the difference is that in step (2),

[0107] The mass ratio of part of the reaction material to the remaining part of the reaction material was replaced to 30:1, and the other conditions were the same to obtain 4-methyl-1-pentene.

[0108] Example 6

[0109] According to the device provided in Example 1;

[0110] According to the method provided in Example 1, the difference is that in step (2),

[0111] The mass ratio of part of the reaction material to the remaining part of the reaction material is replaced with 100:1, and the other conditions are the same to obtain 4-methyl-1-pentene.

[0112] Example 7

[0113] According to the device provided in Example 1;

[0114] According to the method provided in Example 1, the difference is that in step (4),

[0115] The heating conditions were adjusted so that the temperature of the circulating reaction material was 110° C., and the other conditions were the same to obtain 4-methyl-1-pentene.

[0116] Example 8

[0117] According to the device provided in Example 1, the difference is that the reaction unit is selected from a fixed bed reactor having three catalyst beds, and the circulation pipelines at the outlet and inlet of the fixed bed reactor are provided with a cooler V, a pump VI and a heater VII, and the outlet of the heater VIII is connected to each catalyst bed through a circulation branch pipe;

[0118] The method is carried out in the above-mentioned device, except that in step (4),

[0119] The circulating reaction material was divided into three materials of equal mass ratio and then reused for the above dimerization reaction under the same other conditions to obtain 4-methyl-1-pentene.

[0120] Comparative Example 1

[0121] According to the device provided in Example 1;

[0122] According to the method provided in Example 1, the difference is that in step (1),

[0123] No hydrogen is added to the above raw materials, and other conditions are the same to obtain 4-methyl-1-pentene.

[0124] Comparative Example 2

[0125] According to the device provided in Example 1;

[0126] According to the method provided in Example 1, the difference is that in step (2), all reaction materials are subjected to step (3), step (4) is eliminated, and the other conditions are the same. As a result, the reaction temperature rises by more than 100° C., and the reaction cannot proceed normally.

[0127] Comparative Example 3

[0128] According to the device provided in Example 1, the difference is that Figure 2 As shown,

[0129] The reaction unit II is not provided with a circulation pipeline, and is not provided with a cooler V, a pump VI and a heater VII; the reaction unit II is selected from a fixed bed reactor with a heat extraction coil 04;

[0130] The method for preparing 4-methyl-1-pentene by propylene dimerization is carried out in the above-mentioned device, and the method comprises:

[0131] (1) pretreating a raw material containing propylene and hydrogen to obtain a pretreated raw material;

[0132] The purity of the propylene is 95 wt %, the concentration of hydrogen in the raw material is 70 ppm; the water content in the raw material after the pretreatment is 2.4 ppm, and the oxygen content is 2.6 ppm;

[0133] (2) in a nitrogen atmosphere, the pretreated raw material was contacted with the catalyst and a dimerization reaction was carried out (temperature was 150° C., pressure was 10 MPa), the obtained dimerization reaction material was heat exchanged with the cooling medium in the heat extraction coil, and then a first filtration was carried out to obtain a reaction material with a temperature of 165° C.;

[0134] (3) The reaction material and water were mixed at a mass ratio of 100:0.01 and washed with water, and then subjected to a first distillation separation (the top pressure was 1.8 MPa). The mixture obtained at the bottom of the tower was subjected to a second distillation separation (the top pressure was 0.3 MPa) to obtain 4-methyl-1-pentene.

[0135] Table 1

[0136]

[0137] Note: 1-Concentration of coking inhibitor in the raw material calculated as propylene, ppm; 2-Circulation ratio of reaction materials, i.e., mass ratio of part of reaction materials to remaining part of reaction materials; 3-Temperature difference between circulating reaction materials and dimerization reaction, i.e., the temperature of circulating reaction materials is lower than the inlet temperature of dimerization reaction, °C; 4-Total temperature rise of dimerization reaction, °C.

[0138] Table 1

[0139]

[0140] It can be seen from the data in Table 1 that, compared with Comparative Examples 1-3, Examples 1-8 adopt the method provided by the present invention, add a coking inhibitor to the raw materials, and reuse part of the reaction materials after heat removal, which effectively improves the selectivity of 4-methyl-1-pentene.

[0141] Compared with Examples 1-4, it can be seen that adding a coking inhibitor to the raw material can improve the selectivity of 4-methyl-1-pentene, but too large an addition amount significantly reduces the conversion rate of propylene.

[0142] Compared with Comparative Example 3, Example 1 adopts the technical means of recycling part of the reaction materials after heat extraction, so that the radial temperature rise of the reactor is smaller, and the selectivity of 4-methyl-1-pentene is more effectively improved.

[0143] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing 4-methyl-1-pentene by propylene dimerization, characterized in that: The method comprises: (1) pretreating a raw material containing propylene and a coking inhibitor to obtain a pretreated raw material; (2) contacting the pretreated raw material with a catalyst in a non-oxidizing atmosphere and performing a dimerization reaction, and the obtained reaction material is divided into a partial reaction material and a remaining partial reaction material; (3) The remaining reaction material is subjected to distillation separation to obtain 4-methyl-1-pentene. Wherein, part of the reaction material is recycled to the dimerization reaction after heat removal.

2. The method according to claim 1, wherein: The mass ratio of the part of the reaction material to the remaining part of the reaction material is 1-200:1, preferably 1-80:1, and more preferably 10-50:

1.

3. The method according to claim 1 or 2, wherein: The heat extraction process includes: sequentially cooling, pressurizing and heating the part of the reaction material to obtain a circulating reaction material; Preferably, the temperature of the circulating reaction material is 0-100°C lower than the inlet temperature of the dimerization reaction, preferably 0-60°C; Preferably, the temperature of the cooled material is 40-300°C, preferably 40-150°C; Preferably, the pressure of the pressurized material is 4-20 MPa, preferably 6-12 MPa.

4. The method according to any one of claims 1 to 3, wherein: In step (1), the molar concentration of the coking inhibitor in the raw material calculated as propylene is 2-1000 ppm, preferably 10-500 ppm, more preferably 30-300 ppm; and / or, the coking inhibitor is selected from hydrogen; And / or, the pretreatment process includes: dehydrating and deoxygenating the raw material; And / or, the water content in the raw material after the pretreatment is ≤10ppm, preferably ≤3ppm; the oxygen content is ≤10ppm, preferably ≤3ppm.

5. The method according to any one of claims 1 to 4, wherein: In step (2), the catalyst is selected from supported alkali metal catalysts, preferably supported Na / K catalysts; Preferably, the alkali metal loading is 0.1-20 wt %, preferably 1-10 wt %, based on the total weight of the supported alkali metal catalyst; Preferably, the carrier of the supported alkali metal catalyst is selected from at least one of alkali metal carbonate, molecular sieve and activated carbon.

6. The method according to any one of claims 1 to 5, wherein: In step (2), the conditions for the dimerization reaction include: a temperature of 50-300° C., preferably 100-200° C.; a pressure of 4-20 MPa, preferably 6-12 MPa; and / or, the radial temperature difference of the dimerization reaction is ≤10°C / m, preferably ≤5°C / m; and / or, the total temperature rise of the dimerization reaction is ≤60°C, preferably ≤30°C; And / or, the temperature rise of a single catalyst bed in the dimerization reaction is ≤30°C, preferably ≤15°C.

7. The method according to any one of claims 1 to 6, wherein: In step (3), the distillation separation process includes: a first distillation separation and a second distillation separation; The remaining reaction material is subjected to the first distillation separation to obtain light components and a mixed material; the mixed material is subjected to the second distillation separation to obtain 4-methyl-1-pentene and heavy impurities; Preferably, the tower top pressure of the first distillation separation is 1-3 MPa, preferably 1.5-2 MPa; the tower top pressure of the second distillation separation is 0.2-0.8 MPa, preferably 0.2-0.5 MPa; and / or, subjecting the dimerization reaction material to a first filtration to obtain the reaction material; and / or, before the distillation separation, subjecting the remaining portion of the reaction material to a second filtration to obtain a filtered material; Preferably, after the second filtration, the remaining portion of the reaction material is washed with water; Preferably, during the water washing process, the mass ratio of the remaining reaction material to water is 100:0.01-10, preferably 100:0.01-1.

8. A device for preparing 4-methyl-1-pentene by propylene dimerization, characterized in that: The device comprises a pretreatment unit, a reaction unit and a distillation separation unit connected in sequence; The pretreatment unit is used to pretreat the raw material containing propylene and the coking inhibitor to obtain the pretreated raw material; the reaction unit is used to dimerize the pretreated raw material and the catalyst in a non-oxidizing atmosphere to separate the obtained reaction material into a part of the reaction material and the remaining part of the reaction material; the distillation and separation unit is used to distill and separate the remaining part of the reaction material to obtain 4-methyl-1-pentene; Wherein, according to the material flow direction, a heat extraction unit is provided on the circulation pipeline at the outlet and the inlet of the reaction unit, for recycling part of the reaction material to the reaction unit after heat extraction.

9. The device according to claim 8, wherein: The heat extraction unit comprises: a cooler, a pump and a heater connected in sequence, respectively used to cool, pressurize and heat the part of the reaction material in sequence to obtain a circulating reaction material; And / or, the reaction unit comprises at least one reactor connected in series, preferably comprises 2-6 reactors connected in series, and more preferably comprises 2-4 reactors connected in series; Preferably, each of the reactors is provided with 1 to 6 catalyst beds, preferably 1 to 3 catalyst beds; Preferably, the reactor is provided with a first filter component, and the first filter component is arranged below the catalyst bed; And / or, the distillation separation unit comprises: a first distillation separation tower and a second distillation separation tower connected in series, wherein the first distillation separation tower is used to perform a first distillation separation on the remaining part of the reaction material to obtain a light component and a mixed material; and the second distillation separation tower is used to perform a second distillation separation on the mixed material to obtain 4-methyl-1-pentene and heavy impurities.

10. The device according to claim 8 or 9, wherein: The device further comprises: a filtering unit connected to the reaction unit and the rectification and separation unit, and configured to perform a second filtration on the remaining portion of the reaction material to obtain a filtered material; Preferably, the filter unit is provided with a second filter component; Preferably, a water injection port is provided on the pipeline connecting the filtering unit and the distillation separation unit for washing the filtered material with water.

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