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: pretreating a raw material containing propylene, a diluent and a coking inhibitor, and carrying out dimerization reaction on the obtained pretreated raw material and a catalyst in a non-oxidizing atmosphere to obtain 4-methyl-1-pentene, and carrying out rectification separation on the obtained reaction material to obtain the 4-methyl-1-pentene. According to the method provided by the invention, the selectivity of 4M1P is effectively improved, and the catalytic activity and the one-way service life 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 amount of heat released. The reaction temperature is difficult to control, and the conversion rate and selectivity are sensitive to the reaction temperature. Therefore, it is necessary to remove the reaction heat in time to maintain a stable reaction temperature, reduce the occurrence of side reactions, and improve the selectivity of the target product. When the conversion rate is low, the heat released is also low.

[0006] CN202010495971.3 discloses a synthesis process of 4-methyl-1-pentene, in which propylene is dehydrated and deoxygenated and added to a reaction unit for dimerization and isomerization, and then the unreacted raw materials are returned to the reaction unit for circulation after gas-liquid separation. However, in this process method, when the catalyst activity is good, the reaction conversion rate and reaction temperature are difficult to control, and there is a risk that the unreacted raw materials will continue to react, thereby increasing the heat release, and the excess heat cannot be removed in time, causing the reaction temperature to deviate from the normal temperature, affecting the selectivity of the target product.

[0007] CN200910209365.4 discloses a catalyst and a dimerization method for propylene dimerization, using a transition metal coordination compound as a catalyst, and a liquid phase reaction method or a gas phase reaction method such as a dissolution reaction or a suspension reaction can be used. In the liquid phase dimerization method, inert hydrocarbons such as certain aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons or halogenated hydrocarbons are used as solvents. CN201980046469.X discloses a catalyst and a method for propylene dimerization, which reacts a feed stream containing aliphatic α-olefins with a loaded alkali metal or alkali metal complex catalyst to produce branched aliphatic olefins; the aliphatic α-olefin feed stream mainly contains propylene, and the rest is ethylene, saturated hydrocarbons, inert gases or a combination thereof. Although the above-mentioned technology adopts the technical means of adding solvents, it still cannot solve the problems of catalyst coking and deactivation and short service life.

[0008] 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 comes into contact with water and air during disassembly. Summary of the invention

[0009] The purpose of the present invention is to overcome the problems that the existing method for preparing 4-methyl-1-pentene by dimerization of propylene is prone to multimerization and the reaction temperature is difficult to control, resulting in reduced selectivity of 4-methyl-1-pentene and decreased activity of the catalyst, as well as the risk of fire due to blockage of catalyst powder along with materials to the downstream, and to provide a method for preparing 4-methyl-1-pentene by dimerization of propylene and a device for preparing 4-methyl-1-pentene by dimerization of propylene. The method effectively improves the selectivity of 4M1P and improves the catalytic activity and single-pass service life of the catalyst.

[0010] In order to achieve the above-mentioned object, the first aspect of the present invention provides a method for preparing 4-methyl-1-pentene by dimerization of propylene, the method comprising: pretreating a raw material containing propylene, a diluent and a coking inhibitor, dimerizing the obtained pretreated raw material and a catalyst in a non-oxidizing atmosphere, and separating the obtained reaction materials by distillation to obtain 4-methyl-1-pentene.

[0011] Preferably, 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.

[0012] Preferably, in the raw material, the mass ratio of the diluent to propylene is 1-200:1, preferably 1-80:1, and more preferably 10-50:1.

[0013] Preferably, the distillation separation process includes a first distillation separation, a second distillation separation and a third distillation separation; wherein, the reaction material is subjected to the first distillation separation to obtain a light component and a first mixed material; the first mixed material is subjected to the second distillation separation to obtain light impurities and a second mixed material; the second mixed material is subjected to the third distillation separation to obtain 4-methyl-1-pentene and heavy impurities.

[0014] 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;

[0015] The pretreatment unit is used to pretreat the raw material containing propylene, diluent and 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 obtain a reaction material; the distillation and separation unit is used to distill and separate the reaction material to obtain 4-methyl-1-pentene.

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

[0017] (1) The method provided by the present invention reduces the concentration of propylene in the raw material by adding a diluent to the raw material, avoids the uncontrollable propylene conversion rate and heat release when pure propylene is used as the raw material, prevents the bed from overheating, and maintains the reaction temperature within the range required for the dimerization reaction, thereby ensuring the high selectivity of 4M1P; at the same time, a coking inhibitor is added to the raw material to inhibit the occurrence of the polymerization reaction and prevent the catalyst from coking, thereby improving the selectivity of 4M1P and extending the activity and service life of the catalyst;

[0018] (2) The method provided by the present invention also regulates the mass ratio of the diluent to propylene in the raw material so that the reaction temperature rise of the dimerization reaction is ≤60°C, thereby more effectively improving the selectivity of 4M1P and the activity of the catalyst;

[0019] (3) The method provided by the present invention also performs a first filtration, a second filtration, and a water washing on the dimerization reaction materials in sequence 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 washed. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Description of Reference Numerals

[0022] 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; IV-3, third distillation separation tower; 01, first filtration component; 02, second filtration component; 03, water injection port;

[0023] 1. Propylene; 2. Coking inhibitor; 3. Diluent; 4. Raw materials; 5. Raw materials after pretreatment; 6. Reaction materials; 7. Filtered materials; 8. Light components; 9. First mixed material; 10. Light impurities; 11. Second mixed material; 12. 4-methyl-1-pentene; 13. Heavy impurities. DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

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

[0026] A first aspect of the present invention provides a method for preparing 4-methyl-1-pentene by dimerization of propylene, the method comprising: pretreating a raw material containing propylene, a diluent and a coking inhibitor, dimerizing the obtained pretreated raw material and a catalyst in a non-oxidizing atmosphere, and separating the obtained reaction material by distillation to obtain 4-methyl-1-pentene.

[0027] The inventors of the present invention have found that in the method of preparing 4-methyl-1-pentene (4M1P) by propylene dimerization, adding a diluent and a coking inhibitor to the raw material reduces the concentration of raw propylene, avoids the uncontrollable propylene conversion rate and heat release when pure propylene is used as the raw material, and prevents the bed from overheating; on the other hand, it inhibits the occurrence of polymerization reaction, prevents catalyst coking, and thus improves the selectivity of 4M1P and the catalytic activity of the catalyst, and prolongs the life of the catalyst. In particular, by regulating the mass ratio of the diluent to propylene in the raw material, the reaction temperature rise of the dimerization reaction is ≤60°C, preferably ≤30°C, which more effectively improves the selectivity of 4M1P and the activity of the catalyst.

[0028] 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 4M1P is more effectively improved by inhibiting the occurrence of polymerization reaction and preventing catalyst coking.

[0029] In some embodiments of the present invention, preferably, in the raw material, the mass ratio of the diluent to propylene is 1-200:1, for example, 1:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, 60:1, 80:1, 100:1, 150:1, 200:1, and any value in the range of any two values, preferably 1-80:1, more preferably 10-50:1. Meeting the above mass ratio range can better regulate the temperature rise of the balanced dimerization reaction, thereby improving the selectivity of 4M1P.

[0030] In some embodiments of the present invention, preferably, the diluent is selected from alkanes and / or cycloalkanes, preferably selected from C 2 -C 5 Alkanes and / or C 3 -C 6 The cycloalkane is more preferably at least one selected from ethane, propane, n-butane, isobutane and n-pentane, further preferably propane and / or cyclopropane, and most preferably propane.

[0031] In some embodiments of the present invention, preferably, the coking inhibitor is selected from hydrogen.

[0032] In some embodiments of the present invention, preferably, the purity of the propylene is ≥ 80 wt%, preferably ≥ 95 wt%.

[0033] 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.

[0034] In some embodiments of the present invention, preferably, the dimerization reaction conditions include: a temperature of 50-300° C., preferably 100-200° C.; and a pressure of 4-20 MPa, preferably 6-12 MPa. In the present invention, the pressures are all absolute pressures.

[0035] In some embodiments of the present invention, preferably, the reaction temperature rise of the dimerization reaction is ≤60° C., preferably ≤30° C. In the present invention, the reaction temperature rise refers to the difference between the reaction outlet temperature and the reaction inlet temperature.

[0036] In some embodiments of the present invention, preferably, the dimerization reaction includes N reaction stages, N≥1 and N is a natural number, N is preferably selected from 1, 2, 3, 4, 5, 6, and N is more preferably selected from 2, 3, 4; wherein the process of the dimerization reaction includes: subjecting the pretreated raw material and the first catalyst to a first reaction stage in a non-oxidizing atmosphere to obtain a first reaction material; subjecting the first reaction material and the second catalyst to a second reaction stage in a non-oxidizing atmosphere to obtain a second reaction material; ...; subjecting the (N-1) reaction material and the Nth catalyst to an Nth reaction stage in a non-oxidizing atmosphere to obtain the Nth reaction material as the reaction material.

[0037] 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. In the present invention, the carrier of the catalyst is selected from at least one of an alkali metal carbonate, a molecular sieve and activated carbon, preferably an alkali metal carbonate, and the alkali metal carbonate is selected from sodium carbonate and / or potassium carbonate.

[0038] 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%.

[0039] In some embodiments of the present invention, preferably, the distillation separation process includes a first distillation separation, a second distillation separation and a third distillation separation; wherein, the reaction material is subjected to the first distillation separation to obtain a light component and a first mixed material; the first mixed material is subjected to the second distillation separation to obtain light impurities and a second mixed material; the second mixed material is subjected to the third distillation separation to obtain 4-methyl-1-pentene and heavy impurities.

[0040] In the present invention, the light component is rich in diluent and unreacted propylene; the light impurities are diluent, unreacted propylene and a small amount of 4-methyl-1-pentene; the heavy impurities are rich in by-products (polymerization products, such as C 9+ ).

[0041] In some embodiments of the present invention, preferably, the pressure of the first distillation separation is 1-3MPa, preferably 1.5-2MPa; the pressure of the second distillation separation is 0.2-1MPa, preferably 0.5-1MPa; the pressure of the third distillation separation is 0.2-0.8MPa, preferably 0.2-0.5MPa.

[0042] In some embodiments of the present invention, preferably, the light component is returned and mixed into the raw material. The main purpose of such arrangement is to reduce the amount of fresh material used and reduce production costs. In the present invention, the diluent in the raw material can come from fresh diluent or from the light component obtained from the first distillation; it can also contain both fresh diluent and the light component obtained from the first distillation separation.

[0043] 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 to obtain the reaction material.

[0044] In some embodiments of the present invention, preferably, before the distillation separation, the reaction material is subjected to a second filtration to further remove the catalyst fine powder remaining in the reaction material to obtain a filtered material.

[0045] In some embodiments of the present invention, preferably, after the second filtration, the reaction material is contacted with water and reacted. This arrangement is intended to deactivate the catalyst fine powder remaining in the reaction material and avoid the risk of fire when the device is disassembled and exposed to water and air.

[0046] In some embodiments of the present invention, preferably, the mass ratio of the 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 consisting of any two values, preferably 100:0.01-1.

[0047] 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;

[0048] The pretreatment unit I is used to pretreat a raw material 4 containing propylene 1, a diluent 3 and a coking inhibitor 2 to obtain a pretreated raw material 5; the reaction unit II is used to dimerize the pretreated raw material 5 and a catalyst in a non-oxidizing atmosphere to obtain a reaction material 6; and the distillation and separation unit IV is used to distill and separate the reaction material 6 to obtain 4-methyl-1-pentene 12.

[0049] 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.

[0050] 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.

[0051] In some embodiments of the present invention, preferably, Figure 1 As shown, the reactor is provided with a first filter component 01, and the first filter component 01 is arranged below the catalyst bed layer, and is used to perform a first filtration on the material of the dimerization reaction to obtain the reaction material 6. In the present invention, the first filter component 01 is arranged below the last catalyst bed layer from top to bottom in the reactor.

[0052] 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.

[0053] In some embodiments of the present invention, preferably, Figure 1As shown, the device further comprises: a filtering unit III connected to the reaction unit II and the distillation separation unit IV, for performing a second filtration on the reaction material 6 to obtain a filtered material 7. Further preferably, the filtering unit III is provided with a second filtering component 02.

[0054] 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, a sintered metal powder, a ceramic membrane, and a polyester filter element.

[0055] 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 mix the filtered material 7 with water and react.

[0056] In some embodiments of the present invention, preferably, Figure 1 As shown, the distillation separation unit IV includes: a first distillation separation tower IV-1, a second distillation separation tower IV-2 and a third distillation separation tower IV-3 which are connected in series in sequence, wherein the reaction material 6 enters the first distillation separation tower IV-1, and a light component 8 is obtained at the top of the tower, and a first mixed material 9 obtained at the bottom of the tower enters the second distillation separation tower IV-2, and a light impurity 10 is obtained at the top of the tower, and a second mixed material 11 obtained at the bottom of the tower enters the third distillation separation tower IV-3, and 4-methyl-1-pentene 12 is obtained at the top of the tower, and a heavy impurity 13 is obtained at the bottom of the tower.

[0057] In some embodiments of the present invention, preferably, Figure 1 As shown, the top of the first distillation separation tower IV-1 is connected to the pretreatment unit I, which is used to return the light component 8 and mix it into the pretreated raw material 4.

[0058] According to a particularly preferred embodiment of the present invention, a method for preparing 4-methyl-1-pentene by dimerization of propylene comprises: pre-treating a raw material containing propylene, a diluent and a coking inhibitor, dimerizing the obtained pre-treated raw material and a catalyst in a non-oxidizing atmosphere, performing a first distillation separation on the obtained reaction material to obtain a light component and a first mixed material; performing a second distillation separation on the first mixed material to obtain light impurities and a second mixed material; performing a third distillation separation on the second mixed material to obtain 4-methyl-1-pentene and heavy impurities; and returning the light component and mixing it into the raw material;

[0059] Wherein, the molar concentration of the coking inhibitor in the raw material calculated as propylene is 30-300 ppm; in the raw material, the mass ratio of the diluent to propylene is 10-50:1;

[0060] Wherein, the coking inhibitor is selected from hydrogen; the diluent is selected from propane and / or cyclopropane; the water content in the raw material after pretreatment is ≤3ppm; the oxygen content is ≤3ppm;

[0061] Wherein, the catalyst is selected from a supported Na / K catalyst, and the Na / K loading amount is 1-10wt%.

[0062] The present invention will be described in detail below through examples.

[0063] Some process parameters and test results of Examples 1-8 and Comparative Examples 1-2 are listed in Table 1.

[0064] Example 1

[0065] 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 filtration unit III, a first distillation separation tower IV-1, a second distillation separation tower IV-2 and a third distillation separation tower IV-3 connected in sequence; the reaction unit I is selected from a fixed bed reactor containing a single catalyst bed, and the fixed bed reactor and the filtration unit III are respectively provided with a first filtration component 01 and a second filtration component 02; a water injection port 03 is provided on the pipeline connecting the filtration unit III and the first distillation separation tower IV-1;

[0066] 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 top of the first distillation separation tower IV-1 is connected to the pretreatment unit I;

[0067] The method for preparing 4-methyl-1-pentene by propylene dimerization is carried out in the above-mentioned device, and the method comprises:

[0068] (1) pretreating a raw material containing propylene, propane and hydrogen to obtain a pretreated raw material;

[0069] The purity of the propylene is 95 wt %, the molar concentration of the coking inhibitor in the raw material is 50 ppm based on propylene; the mass ratio of propane to propylene in the raw material is 20:1; the water content in the raw material after the pretreatment is 2.5 ppm, and the oxygen content is 2.6 ppm;

[0070] (2) contacting the pretreated raw material with the catalyst and performing a dimerization reaction (temperature of 150° C., pressure of 10 MPa), and filtering the obtained dimerization reaction material to obtain a reaction material;

[0071] The above catalyst is a supported Na / K catalyst, the Na / K loading is 6wt%, and the carrier is potassium carbonate;

[0072] (3) After the reaction material is filtered through a second filtration to obtain a filtered material, it is mixed with water at a mass ratio of 100:0.02 and reacted, and then subjected to a first distillation separation (the pressure at the top of the tower is 1.8 MPa). The first mixed material obtained in the bottom of the tower is subjected to a second distillation separation (the pressure at the top of the tower is 0.8 MPa). The second mixed material obtained in the bottom of the tower is subjected to a second distillation separation (the pressure at the top of the tower is 0.3 MPa), and 4-methyl-1-pentene is obtained at the top of the tower; the light component obtained at the top of the first distillation separation tower is returned and mixed with the above raw materials.

[0073] Example 2

[0074] According to the device provided in Example 1;

[0075] According to the method provided in Example 1, the difference is that in step (1),

[0076] 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.

[0077] Example 3

[0078] According to the device provided in Example 1;

[0079] According to the method provided in Example 1, the difference is that in step (1),

[0080] 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.

[0081] Example 4

[0082] According to the device provided in Example 1;

[0083] According to the method provided in Example 1, the difference is that in step (1),

[0084] 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.

[0085] Example 5

[0086] According to the device provided in Example 1;

[0087] According to the method provided in Example 1, the difference is that in step (1),

[0088] The mass ratio of propane to propylene in the above raw materials is 15:1; other conditions are the same, and 4-methyl-1-pentene is obtained.

[0089] Example 6

[0090] According to the device provided in Example 1;

[0091] According to the method provided in Example 1, the difference is that in step (1),

[0092] The mass ratio of propane to propylene in the above raw materials is 40:1, and other conditions are the same to obtain 4-methyl-1-pentene.

[0093] Example 7

[0094] According to the device provided in Example 1;

[0095] According to the method provided in Example 1, the difference is that in step (1),

[0096] The mass ratio of propane to propylene in the above raw materials was 0.5:1, and the other conditions were the same. As a result, the reaction temperature rose by more than 100°C, and the reaction could not proceed normally.

[0097] Example 8

[0098] According to the device provided in Example 1;

[0099] According to the method provided in Example 1, the difference is that in step (1),

[0100] Replacing the type of diluent with cyclopropane and keeping the other conditions the same, 4-methyl-1-pentene was obtained.

[0101] Comparative Example 1

[0102] According to the device provided in Example 1;

[0103] According to the method provided in Example 1, the difference is that in step (1),

[0104] No hydrogen is added to the above raw materials, and other conditions are the same to obtain 4-methyl-1-pentene.

[0105] Comparative Example 2

[0106] According to the device provided in Example 1;

[0107] According to the method provided in Example 1, in step (1),

[0108] No propane was added to the above raw materials, and other conditions were the same. As a result, the reaction temperature rose by more than 100°C, and the reaction could not proceed normally.

[0109] Table 1

[0110]

[0111] Note: 1-Concentration of coking inhibitor in the raw material calculated as propylene, ppm; 2-Mass ratio of diluent to propylene in the raw material; 3-Reaction temperature rise of dimerization reaction, the difference between reaction outlet temperature and reaction inlet temperature, °C.

[0112] It can be seen from the data in Table 1 that by using the method provided by the present invention, adding a coking inhibitor and a diluent to the raw material can effectively improve the selectivity of 4-methyl-1-pentene.

[0113] 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 yield.

[0114] Compared with Example 1 and Examples 5-7, it can be seen that by adjusting the mass ratio of the diluent to propylene in the raw material, the reaction temperature rise and the selectivity of 4-methyl-1-pentene can be adjusted, but too large a mass ratio will also increase the energy consumption of the device.

[0115] 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: pre-treating a raw material containing propylene, a diluent and a coking inhibitor, dimerizing the obtained pre-treated raw material and a catalyst in a non-oxidizing atmosphere, and rectifying and separating the obtained reaction material to obtain 4-methyl-1-pentene.

2. The method according to claim 1, wherein: 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, in the raw material, the mass ratio of the diluent to propylene 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 diluent is selected from alkanes and / or cycloalkanes, preferably selected from C2-C5 alkanes and / or C3-C6 cycloalkanes, more preferably selected from propane and / or cyclopropane; And / or, the coking inhibitor is selected from hydrogen.

4. The method according to any one of claims 1 to 3, wherein: The pretreatment process includes: dehydrating and deoxidizing the raw materials; 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: The conditions of the dimerization reaction include: a temperature of 50-300°C, preferably 100-200°C; a pressure of 4-20MPa, preferably 6-12MPa; and / or, the reaction temperature rise of the dimerization reaction is ≤60°C, preferably ≤30°C; And / or, the dimerization reaction comprises N reaction stages, N ≥ 1 and N is a natural number, N is preferably selected from 2-6, more preferably selected from 2-4; The dimerization reaction process includes: subjecting the pretreated raw material and the first catalyst to a first reaction stage in a non-oxidizing atmosphere to obtain a first reaction material; subjecting the first reaction material and the second catalyst to a second reaction stage in a non-oxidizing atmosphere to obtain a second reaction material; ...; subjecting the (N-1) reaction material and the Nth catalyst to an Nth reaction stage in a non-oxidizing atmosphere to obtain the Nth reaction material as the reaction material.

6. The method according to any one of claims 1 to 5, wherein: 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.

7. The method according to any one of claims 1 to 6, wherein: The distillation separation process includes a first distillation separation, a second distillation separation and a third distillation separation; The reaction material is subjected to the first distillation separation to obtain a light component and a first mixed material; the first mixed material is subjected to the second distillation separation to obtain light impurities and a second mixed material; the second mixed material is subjected to the third distillation separation to obtain 4-methyl-1-pentene and heavy impurities; Preferably, the pressure of the first distillation separation is 1-3MPa, preferably 1.5-2MPa; the pressure of the second distillation separation is 0.2-1MPa, preferably 0.5-1MPa; the pressure of the third distillation separation is 0.2-0.8MPa, preferably 0.2-0.5MPa; Preferably, the light fraction is returned and mixed into the feedstock.

8. The method according to any one of claims 1 to 7, wherein: Performing a first filtration on the dimerization reaction material to obtain the reaction material; and / or, before the distillation separation, the reaction material is subjected to a second filtration to obtain a filtered material; Preferably, after the second filtration, the reaction material is contacted with water and reacted; Preferably, the mass ratio of the reaction material to water is 100:0.01-10, preferably 100:0.01-1.

9. 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, diluent and 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 obtain a reaction material; the distillation and separation unit is used to distill and separate the reaction material to obtain 4-methyl-1-pentene.

10. The device according to claim 9, wherein: The reaction unit comprises at least one reactor connected in series, preferably 2-6 reactors connected in series, and more preferably 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 device further comprises: a filtering unit connected to the reaction unit and the rectification and separation unit; 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.

11. The device according to claim 9 or 10, wherein: The distillation separation unit comprises: a first distillation separation tower, a second distillation separation tower and a third distillation separation tower connected in series in sequence, wherein the reaction material enters the first distillation separation tower, a light component is obtained at the tower top, a first mixed material obtained at the tower bottom enters the second distillation separation tower, a second mixed material obtained at the tower bottom enters the third distillation separation tower, and 4-methyl-1-pentene is obtained at the tower top; Preferably, the top of the first distillation separation tower is connected to the pretreatment unit.

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