Process for the preparation of 4-methyl-1-pentene by dimerization of propylene using a catalyst and a method for the preparation and use of the catalyst

Abstract

The present application relates to the field of propylene dimerization catalyst, disclose a kind of propylene dimerization catalyst and its preparation method and application, propylene dimerization preparation 4-methyl-1-pentene method, the catalyst includes carrier and active metal supported on the carrier;Wherein, the carrier includes alkali metal carbonate and fluorinated graphite, the active metal includes sodium and / or potassium;Wherein, in the carrier, fluorinated graphite content is 0.5-5wt% based on the mass of the alkali metal carbonate.It can further improve the activity of catalyst, improve the single-pass conversion of propylene and the selectivity of 4M1P by introducing fluorinated graphite in the carrier, through the interaction between fluorinated graphite and alkali metal carbonate.

Description

Technical Field

[0001] This invention relates to the field of propylene dimerization catalysts, specifically to a propylene dimerization catalyst, its preparation method and application, and a method for preparing 4-methyl-1-pentene by propylene dimerization. Background Technology

[0002] Propylene is a crucial cornerstone of modern chemical industry. Dimerization yields various higher olefin products, including 1-pentene, 4-methyl-1-pentene, 2-methyl-1-pentene, and 4-methyl-2-pentene. These dimerization products not only function as precursors for detergents, synthetic oils, and plasticizers in human society, but they can also be used as monomers to polymerize other high-performance polymers. In particular, poly(4-methyl-1-pentene) (PMP), formed by the self-polymerization of 4-methyl-1-pentene (4M1P), is a thermoplastic with significant advantages in properties such as transparency, heat resistance, impact resistance, and corrosion resistance. It is currently widely used in the automotive, aerospace, optics, and medical device industries. Furthermore, linear low-density polyethylene (LLDPE) resin, produced by copolymerizing 4M1P and ethylene, is renowned in industry for its excellent impact resistance, tensile tear strength, and dielectric properties.

[0003] The main technical routes for propylene dimerization include alkali metal catalysis and metallocene complex catalysis. Currently, most metallocene complex catalysis methods use Zr or Hf as the metal center, which cannot simultaneously achieve propylene conversion and 4M1P selectivity (30%-60%). The only exception is the uranium-ceramic complex developed by Dow Chemical, but it also faces limitations such as high catalyst cost and short lifespan, preventing its practical industrialization. Alkali metal catalysis, based on the carbanion principle, can selectively generate thermodynamically inferior 4M1P, thereby improving 4M1P selectivity. This is the most researched method by domestic and international institutions and is the industrialized technology actually adopted by foreign companies such as Mitsui Chemicals (Japan) and Philips (USA).

[0004] The low single-pass conversion rate of the feedstock is the main challenge in the alkali metal-catalyzed propylene dimerization to 4M1P reaction. Therefore, current experiments typically employ methods such as increasing reaction temperature and pressure, and decreasing space velocity to attempt to overcome this limitation. However, while these methods improve the feedstock conversion rate, they also prolong the contact time between the reactants and the catalyst, intensifying the polymerization reaction and increasing the proportion of isomerization byproducts in the product. This presents new challenges for the subsequent industrial separation and purification of the product. Simulation studies of the product component distillation process show that 4M1P is the light key component in the distillation, while 4-methyl-2-pentene (4M2P), with a similar boiling point, is the heavy key component. The ratio of these two components in the distillation feedstock significantly affects the scale and energy consumption of the distillation column. Therefore, their proportion in the product becomes one of the main evaluation indicators for the propylene dimerization reaction. Correspondingly, the selectivity of 4M1P is also an important factor influencing the industrial application potential of propylene dimerization catalysts. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of insufficient activity and poor selectivity of propylene dimerization catalysts in the prior art, and to provide a propylene dimerization catalyst, its preparation method and application, and a method for preparing 4-methyl-1-pentene by propylene dimerization. This catalyst has high activity and good selectivity for 4-methyl-1-pentene.

[0006] To achieve the above objectives, a first aspect of the present invention provides a propylene dimerization catalyst, the catalyst comprising a support and an active metal supported on the support; wherein the support comprises an alkali metal carbonate and fluorinated graphite, and the active metal comprises sodium and / or potassium;

[0007] In the carrier, the content of fluorinated graphite is 0.5-5 wt%, based on the mass of the alkali metal carbonate.

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned propylene dimerization catalyst, comprising:

[0009] (1) Alkali metal carbonates and fluorinated graphite are mixed and molded to obtain a carrier;

[0010] (2) Load the active metal onto the carrier.

[0011] A third aspect of the present invention provides the application of the above-mentioned propylene dimerization catalyst in propylene polymerization reaction.

[0012] The fourth aspect of the present invention provides a method for preparing 4-methyl-1-pentene by propylene dimerization, the method comprising: contacting propylene with a catalyst under an inert atmosphere to carry out selective polymerization of propylene;

[0013] The catalyst is the propylene dimerization catalyst described in the first aspect.

[0014] In existing technologies, alkali metal carbonates are essentially non-sticky compounds and difficult to mold. Graphite is typically added to act as a binder, facilitating carrier molding, but the catalyst activity and selectivity remain unsatisfactory. The inventors of this invention discovered that by introducing fluorinated graphite, which exhibits superior lubrication properties and higher high-temperature stability compared to ordinary graphite, into the carrier, the interaction between fluorinated graphite and alkali metal carbonates further enhances catalyst activity, improving the single-pass conversion rate of propylene and the selectivity of 4M1P. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of the present invention provides a propylene dimerization catalyst, the catalyst comprising a support and an active metal supported on the support; wherein the support comprises an alkali metal carbonate and fluorinated graphite, and the active metal comprises sodium and / or potassium;

[0017] In the carrier, the content of fluorinated graphite is 0.5-5 wt%, based on the mass of the alkali metal carbonate.

[0018] Since alkali metal carbonates are essentially non-sticky compounds and difficult to mold, existing technologies generally add graphite to act as a binder, facilitating the molding of the support. However, due to the inherent lubrication properties of graphite, the pore structure of the support is difficult to further optimize by increasing the amount of graphite added. The inventors of this invention discovered that by introducing fluorinated graphite into the support, the specific surface area and pore volume of the support increase after baking, resulting in a more uniform distribution of the active metal in the supported catalyst. This allows for more complete contact between propylene and the catalyst during the reaction, thereby improving the catalyst's conversion efficiency and product selectivity.

[0019] According to the present invention, preferably, the content of fluorinated graphite in the support, based on the mass of the alkali metal carbonate, is 0.75-3 wt%, for example, it can be a specific content value or a range between the two, such as 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3 wt%. With the above-mentioned preferred composition, the interaction between fluorinated graphite and alkali metal carbonate can be further enhanced, which is beneficial to further and effectively improve the specific surface area and pore volume of the support, thereby improving the catalytic performance of the catalyst.

[0020] In this invention, "fluorinated graphite" refers to a novel graphite material in which fluorine enters between the planar layers of the six-carbon rings of graphite and bonds firmly with carbon atoms through covalent bonds, resulting in a layered structure. Due to its excellent lubricity, fluorinated graphite is generally used in existing technologies as a lubricant, battery active material, etc. However, the inventors of this invention have creatively combined fluorinated graphite with alkali metal carbonates for use as a propylene dimerization catalyst support. They discovered that the interaction between fluorinated graphite and alkali metal carbonates further optimizes the specific surface area and pore volume of the baked support, thereby improving the catalyst's conversion efficiency and product selectivity.

[0021] This invention does not have special requirements regarding the source of the fluorinated graphite; it can be commercially available or prepared using methods known in the prior art. This invention also does not have special limitations on the fluorine content in the fluorinated graphite, as long as the aforementioned structure of the fluorinated graphite can be obtained. Preferably, in the fluorinated graphite, the molar ratio of fluorine to carbon is 1-1.25:1, more preferably 1.1-1.2:1.

[0022] In existing technologies, the specific surface area and pore volume of supports based on alkali metal carbonates are not ideal, and uniform metal distribution cannot be achieved after loading alkali metals, thus limiting catalytic performance. In this invention, the specific surface area and pore volume of the baked support are further optimized through the interaction between fluorinated graphite and alkali metal carbonates. Preferably, the specific surface area of ​​the support is 0.1-20 cm³. 2 / g, preferably 0.5-5cm 2 / g, more preferably 1.5-3cm 2 / g.

[0023] The inventors of this invention discovered that the pore volume of the support can be further controlled by adjusting the content of fluorinated graphite and alkali metal carbonates. Preferably, the pore volume of the support is 0.001-0.05 mL / g, and more preferably 0.003-0.02 mL / g. Under these preferred conditions, it is beneficial to further improve the catalytic activity and selectivity of the catalyst.

[0024] According to the present invention, preferably, the average pore size of the support is 2-60 nm, more preferably 6-18 nm. Within the above-mentioned preferred average pore size range, it is beneficial to improve the propylene conversion rate. More preferably, the average pore size of the support is 8-15 nm.

[0025] In this invention, the specific surface area, pore volume, and average pore size of the carrier are obtained by BET method.

[0026] In this invention, a wide range of particle size is selected for the support, which can be chosen by those skilled in the art according to the needs of the reaction system. Preferably, the particle size of the support is 10-100 mesh, and more preferably 40-60 mesh. Controlling the support particle size within the above-mentioned preferred range helps to improve the matching degree between the catalyst particles and the inner diameter of the reactor, thereby bringing the conversion rate of propylene dimerization and the product isomerization rate into a more balanced value, while achieving a high propylene conversion rate and 4M1P selectivity.

[0027] In existing technologies, the low specific surface area and small pore volume of catalysts hinder the dispersion of active metals on the support. To improve catalyst activity, a higher loading of active metal is often required, leading to low utilization of the active metal and high catalytic costs. Furthermore, excessively high loading can exacerbate catalyst agglomeration, significantly reducing fluidity and drastically increasing the difficulty of subsequent transfer steps. In this invention, by optimizing the pore structure of the support, the loading of active metal can be reduced, the utilization rate of active metal can be improved, and the catalyst fluidity can be maintained at a good level. Preferably, the content of the active metal is 0.5-20 wt% based on the mass of the alkali metal carbonate in the support; more preferably, the content of the active metal is 1-10 wt% based on the mass of the alkali metal carbonate in the support, and more preferably, 1-5 wt%. Within the above-mentioned preferred component content range, a balance can be struck between low metal loading and high conversion and product selectivity.

[0028] In this invention, the active metal exists in a metallic state.

[0029] According to the present invention, the selection range of the alkali metal carbonate is relatively wide, and those skilled in the art can select it according to actual needs. To further improve the catalytic activity of the catalyst, preferably, the alkali metal carbonate is potassium carbonate.

[0030] In this invention, the active metal can be sodium, potassium, or a combination of sodium and potassium, which can be selected by those skilled in the art according to actual needs. Preferably, the active metal includes sodium and potassium. Preferably, the mass ratio of sodium to potassium is 1-5:5-1. With the above-mentioned preferred composition of support and active metal, the catalytic activity of the catalyst and the selectivity for 4-methyl-1-pentene can be further improved.

[0031] A second aspect of the present invention provides a method for preparing the above-mentioned propylene dimerization catalyst, comprising:

[0032] (1) Alkali metal carbonate, fluorinated graphite and guar gum powder are mixed and molded to obtain a carrier;

[0033] (2) Load the active metal onto the carrier.

[0034] In this invention, there are no special requirements for the specific operation and conditions of the mixing and molding process described in step (1), and conventional molding methods in the art can be used. For example, the molding method can be tablet molding.

[0035] Preferably, in step (1), the molding process includes: mixing the alkali metal carbonate, fluorinated graphite, and guar gum powder, followed by tableting, pulverizing, sieving, and molding calcination. The tableting, pulverizing, and sieving can be performed using conventional methods in the art, as long as the carrier has a certain strength and morphology; this invention does not have any particular limitations in this regard. Preferably, through pulverizing and sieving, the particle size of the carrier is 10-100 mesh, more preferably 40-60 mesh. Controlling the carrier particle size within the above-preferred range helps to balance the conversion rate of propylene dimerization and the product isomerization rate, while simultaneously achieving a high propylene conversion rate and 4M1P selectivity.

[0036] In this invention, there are no particular limitations on the molding and baking conditions, and conventional operating conditions in the art can be used. Preferably, the molding and baking conditions include: a baking temperature of 100-800℃, preferably 300-600℃; and a baking time of 1-10h, preferably 2-8h.

[0037] According to the present invention, by introducing guar gum powder into the mixing process, the pore structure of the support can be further optimized. Preferably, the amount of guar gum powder is 0.1-20 wt% of the weight of the alkali metal carbonate, more preferably 1-10 wt%. In the above preferred cases, the catalytic activity of the catalyst can be further improved.

[0038] According to the present invention, the amount of fluorinated graphite is 0.5-5 wt% of the mass of the alkali metal carbonate, preferably 0.75-3 wt%.

[0039] In this invention, the selection range of the alkali metal carbonate has been described above and will not be repeated here. This invention does not have special requirements regarding the source of the alkali metal carbonate. Preferably, the preparation method further includes: pretreating the alkali metal carbonate before mixing and molding to ensure its particle size distribution conforms to the Rosin-Rammler (RR) distribution. The pretreatment method is well known to those skilled in the art; for example, it can be sieved, graded, and mixed according to the Rosin-Rammler (RR) distribution disclosed in EP0083083. Under the above preferred conditions, it is more beneficial to leverage the interaction between the alkali metal carbonate and fluorinated graphite, improving the overall performance of the support and thus enhancing the catalytic performance of the catalyst.

[0040] In this invention, the loading in step (2) can be any conventional loading method in the art, as long as the active metal is dispersed on the carrier. Preferably, step (2) includes: mixing the carrier and the active metal under an inert atmosphere.

[0041] The present invention does not impose any particular limitation on the specific conditions for mixing, and those skilled in the art can select them according to actual needs. Preferably, the mixing conditions include: a temperature of 100-600℃, more preferably 200-400℃; and a time of 0.5-8h, more preferably 1-6h.

[0042] The present invention does not have particular requirements for the specific mixing method, as long as the active metal can be uniformly dispersed on the carrier. Any mixing method well known to those skilled in the art can be used, such as rotational mixing or stirring mixing. Preferably, the mixing is carried out under stirring conditions.

[0043] In this invention, preferably, the inert atmosphere is provided by at least one of nitrogen, argon, neon and helium.

[0044] In this invention, to ensure the uniformity of the support, the preparation method preferably further includes: drying the support before loading it with an active metal. The drying can be performed using conventional operations and conditions in the art. Preferably, the drying includes drying at 100-400°C for 0.5-4 hours in the presence of an inert atmosphere.

[0045] A third aspect of the present invention provides the application of the above-mentioned propylene dimerization catalyst in propylene polymerization reaction.

[0046] The fourth aspect of the present invention provides a method for preparing 4-methyl-1-pentene by propylene dimerization, the method comprising: contacting propylene with a catalyst under an inert atmosphere to carry out selective polymerization of propylene;

[0047] The catalyst is the propylene dimerization catalyst described in the first aspect.

[0048] In this invention, the selection range for the contact conditions is relatively wide and can be chosen according to actual production needs. Preferably, the contact conditions include: a reaction pressure of 4-16 MPa, more preferably 6-12 MPa; a reaction temperature of 120-180℃, more preferably 140-160℃; and a liquid hourly space velocity of 0.2-6 h⁻¹. -1 Preferably 0.6-4h -1 .

[0049] According to the present invention, the inert atmosphere is an inert protective gas that does not participate in the reaction, and may be provided by at least one of nitrogen, argon, neon and helium.

[0050] The method for preparing 4-methyl-1-pentene by propylene dimerization provided by this invention is applicable to a wide range of liquid hourly space velocities (LISH velocities). Within this wide range, it can maintain relatively stable 4-methyl-1-pentene selectivity, which is beneficial for ensuring product stability in industrial production. This keeps the subsequent product distillation conditions within a small fluctuation range, reduces energy consumption, and lowers the capital investment in the distillation column.

[0051] Preferably, the method further includes: subjecting the propylene to deoxygenation and dehydration treatment prior to the contact. The deoxygenation and dehydration treatment can be performed using conventional methods in the art, which are well known to those skilled in the art and will not be described in detail here.

[0052] Preferably, the contact is performed in a high-voltage microreactor.

[0053] The present invention will be described in detail below through embodiments.

[0054] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available.

[0055] In the examples, the molar ratio of fluorine to carbon in the fluorinated graphite is 1.18:1.

[0056] Example 1

[0057] (1) Anhydrous potassium carbonate was sieved, graded, and mixed according to the Rosin-Rammler distribution (RR distribution) disclosed in EP0083083. Based on the mass of the prepared anhydrous potassium carbonate (RR distribution potassium carbonate), 1 wt% fluorinated graphite and 2.5 wt% guar gum powder were added and mixed evenly. The mixture was then pressed into tablets using an electric tablet press at a pressure of 20 MPa and a holding time of 5 min. The pressed tablets were pulverized and sieved. The 40-60 mesh (300-450 nm) carrier particles were placed in a vacuum crucible furnace and baked at 500℃ and atmospheric pressure for 6 h to obtain the catalyst support. The physicochemical properties of the support are shown in Table 1.

[0058] (2) Support loading: A certain amount of baked catalyst support was placed in a three-necked flask under a nitrogen atmosphere and dried at 350°C by mechanical stirring and electric heating. After the flask wall was free of water mist, it was maintained for 2 hours. After cooling, based on the mass of anhydrous potassium carbonate, 2.2 wt% of metallic sodium and 2.8 wt% of metallic potassium were added. Then, the mixture was stirred at 350°C for 4 hours to prepare a gray-black powder propylene dimerization catalyst A1.

[0059] Example 2

[0060] (1) Anhydrous potassium carbonate was sieved, graded, and mixed according to the Rosin-Rammler distribution (RR distribution) disclosed in EP0083083. Based on the mass of the prepared anhydrous potassium carbonate (RR distribution potassium carbonate), 0.75 wt% fluorinated graphite and 2.5 wt% guar gum powder were added and mixed evenly. The mixture was then pressed into tablets using an electric tablet press at a pressure of 20 MPa and a holding time of 5 min. The pressed tablets were pulverized and sieved. The 40-60 mesh (300-450 nm) carrier particles were placed in a vacuum crucible furnace and baked at 500℃ and atmospheric pressure for 6 h to obtain the catalyst support. The physicochemical properties of the support are shown in Table 1.

[0061] (2) Support loading: A certain amount of baked catalyst support was placed in a three-necked flask under a nitrogen atmosphere and dried at 300°C by mechanical stirring and electric heating. After the flask wall was free of water mist, it was maintained for 2 hours. After cooling, 3 wt% of metallic sodium and 2 wt% of metallic potassium were added based on the mass of anhydrous potassium carbonate. Then, the mixture was stirred at 300°C for 6 hours to prepare a gray-black powder propylene dimerization catalyst A2.

[0062] Example 3

[0063] (1) Anhydrous potassium carbonate was sieved, graded, and mixed according to the Rosin-Rammler distribution (RR distribution) disclosed in EP0083083. Based on the mass of the prepared anhydrous potassium carbonate (RR distribution potassium carbonate), 2 wt% fluorinated graphite and 2.5 wt% guar gum powder were added and mixed evenly. The mixture was then pressed into tablets using an electric tablet press at a pressure of 20 MPa and a holding time of 5 min. The pressed tablets were pulverized and sieved. The 40-60 mesh (300-450 nm) carrier particles were placed in a vacuum crucible furnace and baked at 500℃ and atmospheric pressure for 6 h to obtain the catalyst support. The physicochemical properties of the support are shown in Table 1.

[0064] (2) Support loading: A certain amount of baked catalyst support was placed in a three-necked flask under a nitrogen atmosphere and dried at 350°C by mechanical stirring and electric heating. After the flask wall was free of water mist, it was maintained for 2 hours. After cooling, based on the mass of anhydrous potassium carbonate, 2.8 wt% of metallic sodium and 2.2 wt% of metallic potassium were added. Then, the mixture was stirred at 350°C for 4 hours to prepare a gray-black powder propylene dimerization catalyst A3.

[0065] Example 4

[0066] The method is the same as in Example 1, except that in step (2), potassium metal is replaced with an equal mass of sodium metal, and the resulting catalyst is denoted as A4.

[0067] Example 5

[0068] The method was followed as in Example 1, except that the amount of fluorinated graphite added was 3 wt%, and the physicochemical properties of the support are shown in Table 1. The resulting catalyst is designated A5.

[0069] Example 6

[0070] Following the method in Example 1, except that the pressed sheet-like support was pulverized and sieved, and the support particles of 16-20 mesh (900-1250 nm) were placed in a vacuum crucible furnace and baked at 500°C and atmospheric pressure for 6 hours with air to obtain the catalyst support. The physicochemical properties of the support are shown in Table 1. The obtained catalyst is denoted as A6.

[0071] Comparative Example 1

[0072] The method described in Example 1 was followed, except that an equal mass of graphite was used instead of fluorinated graphite. The physicochemical properties of the support are shown in Table 1. The resulting catalyst is denoted as DA1.

[0073] Comparative Example 2

[0074] The method was followed as in Example 1, except that the amount of fluorinated graphite added was 0.25 wt%, and the physicochemical properties of the support are shown in Table 1. The resulting catalyst is denoted as DA2.

[0075] Table 1 Physicochemical properties of the carrier

[0076]

[0077] Test case

[0078] The catalyst was transferred to the reactor under a nitrogen atmosphere and connected to a high-pressure microreactor. The raw material propylene was fed into the reactor via a high-pressure constant flow pump and sequentially through a deoxygenation and dehydration pretreatment system to carry out the reaction of propylene dimerization to prepare 4-methyl-1-pentene (4M1P). The reaction conditions are shown in Table 2. A portion of the reaction product was split and sent to a gas chromatograph for online analysis through a six-way valve, while the remaining product was collected in a cold trap collection bottle.

[0079] Gas chromatography analysis of the products was performed using a PONA column (50m×200μm×0.5μm), with a detector temperature of 300℃, an injection port temperature of 250℃, a split ratio of 1:200, and a programmed temperature rise of 35℃ for 15 min, followed by a rise at 2℃ / min to 65℃, and then a rise at 20℃ / min to 250℃. The product analysis results are listed in Table 2.

[0080] Table 2

[0081]

[0082]

[0083] The results in Tables 1 and 2 show that the propylene dimerization catalyst provided by this invention has the advantages of high activity and good selectivity, especially at a liquid hourly space velocity of 2.4 h⁻¹. -1 Under polymerization conditions, a 4M1P selectivity of up to 91% can be achieved, which greatly reduces the scale and energy consumption of reactant distillation and purification equipment and provides the possibility for industrial separation of reactants in the later stage. At the same time, the test results under multiple liquid hourly space velocity polymerization conditions provide alternative solutions for the application of catalysts in the later stage. These results together promote the industrial application of propylene dimerization catalysts.

[0084] 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 propylene dimerization catalyst, characterized in that, The catalyst comprises a support and an active metal supported on the support; wherein the support comprises an alkali metal carbonate and fluorinated graphite, and the active metal comprises sodium and / or potassium; In the carrier, based on the mass of the alkali metal carbonate, the content of fluorinated graphite is 0.5-5 wt%, and the molar ratio of fluorine to carbon in the fluorinated graphite is 1.1-1.25:

1. The pore volume of the carrier is 0.003-0.02 mL / g.

2. The catalyst according to claim 1, wherein, In the carrier, the content of fluorinated graphite is 0.75-3 wt%, based on the mass of the alkali metal carbonate; And / or, in the fluorinated graphite, the molar ratio of fluorine to carbon is 1.1-1.2:

1.

3. The catalyst according to claim 1 or 2, wherein, The specific surface area of ​​the carrier is 0.1-20 cm². 2 / g; And / or, the average pore size of the carrier is 2-60 nm; And / or, the particle size of the carrier is 10-100 mesh.

4. The catalyst according to claim 3, wherein, The specific surface area of ​​the carrier is 0.5-5 cm². 2 / g; And / or, the average pore size of the carrier is 6-18 nm; And / or, the particle size of the carrier is 40-60 mesh.

5. The catalyst according to claim 1 or 2, wherein, Based on the mass of the alkali metal carbonate in the carrier, the content of the active metal is 0.5-20 wt%.

6. The catalyst according to claim 5, wherein, Based on the mass of the alkali metal carbonate in the carrier, the content of the active metal is 1-10 wt%.

7. The catalyst according to claim 1 or 2, wherein, The alkali metal carbonate is potassium carbonate.

8. The catalyst according to claim 1 or 2, wherein, The active metals include sodium and potassium.

9. The catalyst according to claim 8, wherein, In the active metal, the mass ratio of sodium to potassium, calculated by element, is 1-5:5-1.

10. A method for preparing the propylene dimerization catalyst according to any one of claims 1-9, comprising: (1) Alkali metal carbonate, fluorinated graphite and guar gum powder are mixed and molded to obtain a carrier; (2) Load the active metal onto the carrier.

11. The preparation method according to claim 10, wherein, In step (1), the molding process includes: mixing the alkali metal carbonate, fluorinated graphite and guar gum powder, and then pressing, crushing, sieving and molding the mixture into tablets.

12. The preparation method according to claim 11, wherein, The conditions for molding and calcining include: calcination temperature of 100-800℃ and calcination time of 1-10h.

13. The preparation method according to claim 12, wherein, The conditions for molding and calcination include: calcination temperature of 300-600℃ and calcination time of 2-8h.

14. The preparation method according to claim 10 or 11, wherein, The amount of guar gum powder used is 0.1-20 wt% of the weight of the alkali metal carbonate.

15. The preparation method according to claim 14, wherein, The amount of guar gum powder used is 1-10 wt% of the weight of the alkali metal carbonate.

16. The preparation method according to claim 10, wherein, Step (2) includes mixing the carrier and the active metal under an inert atmosphere.

17. The preparation method according to claim 16, wherein, The mixing conditions include a temperature of 100-600℃ and a time of 0.5-8h.

18. The preparation method according to claim 17, wherein, The mixing conditions include: a temperature of 200-400℃ and a time of 1-6 hours.

19. The preparation method according to claim 16, wherein, The mixing is carried out under stirring conditions.

20. The preparation method according to claim 16, wherein, The inert atmosphere is provided by at least one of nitrogen, argon, neon and helium.

21. The use of the propylene dimerization catalyst according to any one of claims 1-9 in the propylene polymerization reaction.

22. A method for preparing 4-methyl-1-pentene by propylene dimerization, the method comprising: In an inert atmosphere, propylene is brought into contact with a catalyst to carry out selective polymerization of propylene; The catalyst is characterized in that it is a propylene dimerization catalyst according to any one of claims 1-9.

23. The method according to claim 22, wherein, The contact conditions include: reaction pressure 4-16 MPa, reaction temperature 120-180 °C, and liquid hourly space velocity (LISH) of 0.2-6 h⁻¹. -1 .

24. The method according to claim 23, wherein, The contact conditions include: a reaction pressure of 6-12 MPa, a reaction temperature of 140-160 °C, and a liquid hourly space velocity of 0.6-2.4 h⁻¹. -1 .

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