Method for synthesizing 4-methyl-1-pentene through propylene dimerization

Abstract

The method comprises the following steps: filling a fixed bed reactor with a propylene dimerization catalyst, carrying out purification treatment on the vaporized raw material propylene, feeding the purified raw material propylene into the fixed bed reactor, carrying out a reaction, and carrying out separation to remove an isomerization product so as to obtain the target product 4-methyl-1-pentene. The propylene dimerization catalyst comprises a carrier and active metal loaded on the carrier, wherein the carrier is a mixture which is modified by taking a fatty alkyl dimethyl tertiary amine solvent as an auxiliary agent and comprises alkali metal carbonate and metal oxide, and the active metal comprises sodium and / or potassium. According to the present invention, the problems of low activity and low reaction conversion rate of the existing propylene dimerization catalyst are effectively solved, the catalyst has characteristics of high propylene conversion rate and high 4MP1 selectivity, the conversion rate of the reaction of propylene dimerization into 4MP1 is improved, and the support is provided for the industrialization of the propylene dimerization process.

Description

Technical Field

[0001] This invention relates to a catalyst for the dimerization of propylene to 4-methyl-1-pentene (4MP1) and a method for synthesizing 4-methyl-1-pentene (4MP1), belonging to the field of propylene dimerization. Background Technology

[0002] 4-Methyl-1-pentene (4MP1) is a product of propylene dimerization and is an important chemical raw material and intermediate. Its main uses include the following:

[0003] 1. An important raw material for the synthesis of poly-4-methyl-1-pentene (PMP)

[0004] Poly(4-methyl-1-pentene) (PMP) is a novel thermoplastic resin, primarily produced by the dimerization of propylene to obtain the monomer 4-methyl-1-pentene (4PM1), followed by polymerization using a Ziegler-Natta catalyst or a metallocene catalyst. PMP can be molded using injection molding, blow molding, and extrusion methods, and possesses advantages such as high light transmittance, good heat resistance, non-toxicity, chemical resistance, creep resistance, and excellent electrical insulation. Due to its superior comprehensive properties, PMP can be used to prepare artificial kidney dialysis membranes, oxygenation membranes, and hollow fiber membranes (PMP membranes), and is widely used in the medical device field. Furthermore, PMP can also be made into microporous membrane materials, adsorbent materials, and encapsulation mold materials, showing great application potential in high-frequency electronic components and 5G communication base stations.

[0005] ECMO, or Extracorporeal Membrane Oxygenation Therapy, commonly known as "artificial lung," is currently the most crucial support method for severe cardiopulmonary failure and is hailed as the "last straw" for critically ill pneumonia patients. The oxygenation membrane is the core component of the ECMO system, responsible for blood oxygenation, and the main material used to produce the oxygenation membrane is PMP hollow fiber membrane.

[0006] PMP crystals have unique sizes and morphologies, making their preparation process difficult to control. Therefore, globally, there are very few PMP manufacturers with limited production capacity, with Mitsui Chemicals of Japan being the main supplier. Currently, Chinese companies mainly focus on PMP modification and PMP products; PMP materials have not yet achieved industrial-scale production, and demand still relies on imports. With the increasing demand from ECMO clinical applications and the accelerated construction of 5G base stations, the PMP market has broad development prospects, leading to an urgent need for domestic substitution of 4-methyl-1-pentene (4PM1).

[0007] 2. Synthesis of linear low-density polyethylene resin (LLDPE)

[0008] Linear low-density polyethylene (LLDPE) resin uses comonomers such as 1-butene, 1-hexene, 1-octene, and 4MP1. As the number of carbon atoms and the length of the branched chains increase in the comonomers, the tensile strength, impact strength, tear strength, and puncture resistance of LLDPE films and other products are improved. Among the comonomers, 4MP1 copolymers exhibit superior performance, and the traditional method of trimerizing ethylene to produce hexene is more expensive than using 4MP1. Therefore, since the 1970s, foreign polyethylene (PE) manufacturers have heavily researched the production process of 4MP1 and used it for copolymerization in LLDPE production, achieving significant results. For example, Mitsui Petrochemicals' Ultzex ​​brand LLDPE, which went into production in 1982, is a copolymer of 4MP1 and ethylene, exhibiting significantly improved impact toughness and relative elongation at break.

[0009] Most of the LLDPE produced in my country uses butene and hexene as copolymers, and there is no LLDPE plant using 4MP1 as a copolymer. However, judging from the international development trend of LLDPE resin, 4MP1 as a comonomer will become the mainstream in the high-end LLDPE market.

[0010] The main method for producing 4-methyl-1-pentene (4MP1) is the selective dimerization of propylene. The catalyst used is primarily alkali metal-based, prepared by dispersing the alkali metal on an alkali metal carbonate and / or bicarbonate support. This catalyst, as a traditional propylene dimerization catalyst, can achieve high selectivity. However, the low single-pass conversion rate of the feedstock is the main challenge in the alkali metal-catalyzed propylene dimerization to 4MP1 reaction. Current research, both domestically and internationally, focuses on adding transition metals, metal oxides, or other additives to the alkali metal catalyst, or on modifying the support itself and adding auxiliary agents to improve the conversion rate. Simultaneously, during experiments, a series of operations are typically employed, such as increasing the reaction temperature, pressure, and decreasing the space velocity, to attempt to overcome this limitation. However, changes in operating conditions undoubtedly exacerbate the polymerization reaction, leading to an increase in isomeric byproducts, especially 4-methyl-2-pentene (4MP2), which has a similar boiling point, making subsequent separation more difficult. Summary of the Invention

[0011] The technical problem to be solved by the present invention is: how to provide a catalyst for the dimerization of propylene to 4-methyl-1-pentene (4MP1) by optimizing the pore structure of the support, and a method for synthesizing 4MP1 to solve the problem of low reaction conversion rate of existing propylene dimerization catalysts.

[0012] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: a catalyst for propylene dimerization, comprising a support and an active metal supported on the support; wherein the support is a mixture of alkali metal carbonates and metal oxides modified with a fatty alkyl dimethyl tertiary amine solvent as an auxiliary agent, and the active metal comprises at least one of sodium and potassium.

[0013] Preferably, the alkali metal carbonate in the carrier is potassium carbonate; the metal oxide in the carrier is magnesium oxide, calcium oxide, or a mixture of the two; and the aliphatic alkyl dimethyl tertiary amine solvent aid is tetraalkyl dimethyl tertiary amine, octaalkyl dimethyl tertiary amine, decaalkyl dimethyl tertiary amine, dodecyl dimethyl tertiary amine, tetradecyl dimethyl tertiary amine, or hexadecyl dimethyl tertiary amine, preferably tetraalkyl dimethyl tertiary amine.

[0014] Preferably, in the carrier, the mass content of the metal oxide is 1-15%, preferably 3-10%, based on the mass of the alkali metal carbonate; the mass content of the aliphatic alkyl dimethyl tertiary amine solvent is 5-400%, based on the mass of the mixture of alkali metal carbonate and metal oxide; and the mass content of the active metal is 0.5-25%, based on the mass of the carrier.

[0015] The present invention also provides a method for synthesizing the above-mentioned propylene dimerization catalyst: alkali metal carbonate and metal oxide are mixed and sieved to obtain a particulate support mixture. Then, the mixture is mixed with a fatty alkyl dimethyl tertiary amine solvent. The resulting paste is first vacuum dried in air at 85-95°C, then calcined, and then cooled to 80-85°C in a nitrogen atmosphere. The alkali metal is then molten and loaded, and then heated and kept at a constant temperature to obtain a uniformly distributed catalyst. The catalyst is then cooled to room temperature for later use.

[0016] Preferably, the sieve diameter is 15–60 μm, more preferably 30–50 μm, and even more preferably 35–45 μm.

[0017] Preferably, the mass ratio of the mixture to the fatty alkyl dimethyl tertiary amine solvent is 0.25 to 20, more preferably 1 to 12.

[0018] Preferably, the calcination is carried out at 400-950℃ for 1-5 hours, and more preferably at 650-850℃ for 2-4 hours; the mass content of the alkali metal molten and loaded on the carrier after calcination is 0.5-25%, preferably 1-10%; the reheating and constant temperature after calcination is carried out at 150-350℃ for 0.5-4 hours, and more preferably at 250-300℃ for 2-3 hours.

[0019] This invention also provides a method for the dimerization of propylene to 4-methyl-1-pentene (4MP1): the above-mentioned propylene dimerization catalyst is packed into a fixed-bed reactor. The vaporized propylene feedstock is first purified before entering the fixed-bed reactor to react. Isomers are separated and removed to obtain the target product 4-methyl-1-pentene. The entire reaction process mainly involves dimerization and isomerization. The target product is 4MP1, and isomers such as 4-methyl-2-pentene (4MP2), C5 components, 1-hexene, and 2-hexene are also produced as the reaction proceeds. The reactor used is a conventional fixed-bed reactor, and the heat released by the reaction is removed by cooling water from the fixed-bed reactor jacket.

[0020] Preferably, the vaporization of the raw material propylene is achieved by heating or reducing pressure; the purification treatment is performed by adsorption; the reaction operating temperature is 100–250°C, preferably 150–200°C; the reaction operating pressure is 5–20 MPa, preferably 10–15 MPa; and the reaction space velocity is 0.5–4 h⁻¹. -1 Preferably 1-3 hours -1 .

[0021] Preferably, the separation is specifically distillation, and the distillation column used is a plate column or a packed column, and the method used is atmospheric distillation or vacuum distillation.

[0022] The reaction of propylene dimerization to 4MP1 using the catalyst and synthesis method synthesized in this invention has the characteristics of high propylene conversion and high 4MP1 selectivity. It can effectively solve the problem of low conversion rate in the existing reaction of propylene dimerization to 4-methyl-1-pentene (4MP1) and achieve better reaction results. Detailed Implementation

[0023] To make the present invention more apparent and understandable, preferred embodiments are described in detail below.

[0024] Unless otherwise specified, the proportions and percentages mentioned in the following examples and comparative examples refer to mass (percentage), and the raw materials used are all commercially available.

[0025] In the examples, the carrier mixture used is potassium carbonate, and the metal oxide used is magnesium oxide or calcium oxide or a mixture of the two.

[0026] The carrier mixture modifier used in the examples is a fatty alkyl dimethyl tertiary amine solvent, preferably tetraalkyl dimethyl tertiary amine.

[0027] The active metal used in the examples is sodium or potassium or a mixture of both.

[0028] Example 1

[0029] Anhydrous potassium carbonate, magnesium oxide, and calcium oxide were mixed in a ratio of 20:1:1, sieved, and classified to obtain 30-50 μm particles, which were used as a carrier. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 1:2 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in air, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in a nitrogen atmosphere, sieved, and a carrier with a particle size of 35-45 μm was taken.

[0030] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain a uniformly distributed catalyst A. The catalyst A was then cooled to room temperature and set aside for use.

[0031] The catalyst A obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0032] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0033] Example 2

[0034] Anhydrous potassium carbonate, magnesium oxide, and calcium oxide were mixed in a ratio of 20:1:1, sieved, and classified to obtain 30-50 μm particles, which were used as a carrier. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 1:1 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in an air atmosphere, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in a nitrogen atmosphere, sieved, and a carrier with a particle size of 35-45 μm was taken.

[0035] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain a uniformly distributed catalyst B. The catalyst was then cooled to room temperature and set aside for use.

[0036] The catalyst B obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0037] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0038] Example 3

[0039] Anhydrous potassium carbonate, magnesium oxide, and calcium oxide were mixed in a ratio of 20:1:1, sieved, and classified to obtain 30-50 μm particles, which were used as carriers. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 2:1 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in an air atmosphere, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in a nitrogen atmosphere, sieved, and a carrier with a particle size of 35-45 μm was taken.

[0040] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain a uniformly distributed catalyst C. The catalyst was then cooled to room temperature and set aside for use.

[0041] The catalyst C obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0042] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0043] Example 4

[0044] Anhydrous potassium carbonate, magnesium oxide, and calcium oxide were mixed in a ratio of 20:1:1, sieved, and classified to obtain 30-50 μm particles, which were used as a carrier. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 1:2 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in air, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in a nitrogen atmosphere, sieved, and a carrier with a particle size of 35-45 μm was taken.

[0045] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (all potassium metal) was molten and loaded, and heated to 300℃ and kept at that temperature for 3 hours to obtain a uniformly distributed catalyst D. The catalyst was then cooled to room temperature and set aside for use.

[0046] The catalyst D obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0047] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0048] Example 5

[0049] Anhydrous potassium carbonate and magnesium oxide were mixed in a ratio of 10:1, sieved, and classified to obtain particles of 30-50 μm, which were used as carriers. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 1:2 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in air, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in a nitrogen atmosphere, sieved, and a carrier of 35-45 μm was taken.

[0050] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain a uniformly distributed catalyst E. The catalyst was then cooled to room temperature and set aside for use.

[0051] The catalyst E obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0052] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0053] Example 6

[0054] Anhydrous potassium carbonate and magnesium oxide were mixed in a ratio of 10:1, sieved, and classified to obtain 30-50 μm particles, which were used as carriers. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 1:1 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in an air atmosphere, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in a nitrogen atmosphere, sieved, and a carrier with a particle size of 35-45 μm was taken.

[0055] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain a uniformly distributed catalyst F. The catalyst was then cooled to room temperature and set aside for use.

[0056] The catalyst F obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0057] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0058] Example 7

[0059] Anhydrous potassium carbonate and magnesium oxide were mixed in a ratio of 10:1, sieved, and classified to obtain 30-50 μm particles, which were used as carriers. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 2:1 to obtain a paste. The paste was first vacuum dried at 85 °C for 2 h in an air atmosphere, and then calcined at 650 °C for 4 h. The carrier was cooled to 80-85 °C in a nitrogen atmosphere, sieved, and a carrier with a size of 35-45 μm was taken.

[0060] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain a uniformly distributed catalyst G. The catalyst was then cooled to room temperature and set aside for use.

[0061] The catalyst G obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0062] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0063] Example 8

[0064] Anhydrous potassium carbonate and magnesium oxide were mixed in a ratio of 10:1, sieved, and classified to obtain particles of 30-50 μm, which were used as carriers. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent in a ratio of 1:2 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in air, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in a nitrogen atmosphere, sieved, and a carrier of 35-45 μm was taken.

[0065] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (all potassium metal) was molten and loaded, and heated to 300℃ and kept at that temperature for 3 hours to obtain a uniformly distributed catalyst H. The catalyst was then cooled to room temperature and set aside for use.

[0066] The catalyst H obtained above was packed into a fixed-bed reactor, and the reaction was carried out according to the method and process of propylene dimerization to 4-methyl-1-pentene (4MP1) of the present invention. After a series of processes such as vaporization, purification, filtration, polymerization and separation, the raw material propylene was obtained to obtain the reaction product.

[0067] The propylene conversion rate was determined by calculating the propylene content in the raw materials and products; the selectivity of 4-methyl-1-pentene (4MP1) was obtained by calculating the ratio of the amount of 4-methyl-1-pentene (4MP1) in the product to the amount of converted propylene. Relevant data are shown in Table 1.

[0068] Comparative Example 1

[0069] Anhydrous potassium carbonate, magnesium oxide, and calcium oxide were mixed in a ratio of 20:1:1, sieved, and classified to obtain a 35-45 μm polymer, which was used as a carrier without being mixed with tetraalkyldimethylamine solvent.

[0070] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain catalyst I with uniform distribution. The catalyst was then cooled to room temperature and set aside for use.

[0071] The remaining steps and methods are the same as in Example 1.

[0072] Comparative Example 2

[0073] Anhydrous potassium carbonate was sieved and classified to obtain 35-45 μm particles, which were used as a carrier and were not mixed with metal oxides or tetraalkyldimethylamine solvent.

[0074] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the support, 5% alkali metal (all potassium metal) was molten and loaded onto it. The mixture was heated to 300°C and kept at that temperature for 3 hours to obtain a uniformly distributed catalyst J. The catalyst was then cooled to room temperature and set aside for use.

[0075] The remaining steps and methods are the same as in Example 1.

[0076] Comparative Example 3

[0077] Anhydrous potassium carbonate was sieved and classified to obtain particles of 30-50 μm, which were used as a carrier. The above carrier mixture was mixed with tetraalkyldimethyl tertiary amine solvent at a ratio of 1:2 to obtain a paste. The paste was first vacuum dried at 85°C for 2 hours in air atmosphere, and then calcined at 650°C for 4 hours. The carrier was cooled to 80-85°C in nitrogen atmosphere, sieved, and a carrier of 35-45 μm was taken.

[0078] A certain amount of catalyst support was placed in a three-necked flask under a nitrogen atmosphere. Based on the mass of the mixed support, 5% alkali metal (sodium to potassium in a mass ratio of 1:1) was molten and loaded, and heated to 300℃ for 3 hours to obtain a uniformly distributed catalyst K. The catalyst was then cooled to room temperature and set aside for use.

[0079] The remaining steps and methods are the same as in Example 1.

[0080] Using the aforementioned propylene dimerization process, a certain temperature was selected within the aforementioned preferred operating temperature range of 150–200°C, a certain pressure was selected within the aforementioned preferred operating pressure range of 10–15 MPa, and a certain space velocity was selected within the aforementioned preferred space velocity range of 1–3 h⁻¹. The catalysts obtained in Examples 1–8 and Comparative Examples 1–3 were applied and verified. The application results are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] As can be seen from the results in Table 1, the propylene dimerization catalyst provided by the present invention has the advantages of high activity and good selectivity. Under the preferred polymerization conditions of the present invention, the selectivity of 4MP1 in Example 4 is the highest, reaching 89.2%. At the same time, the propylene conversion rate is also improved to a certain extent compared with Comparative Examples 1 to 3. The higher selectivity reduces the difficulty of the subsequent separation process and improves the purity of the product.

[0085] This invention provides a catalyst for propylene dimerization, a method for synthesizing this catalyst, and a method for synthesizing dipropylene 4MP1 using the propylene dimerization catalyst. Examples and comparative examples were used to verify the application of the invention. The results show that this invention can effectively solve the problem of low conversion rate in existing propylene dimerization reactions, thereby improving the conversion rate of the propylene dimerization reaction to 4MP1, and providing support for the industrialization of propylene dimerization processes.

Claims

1. A catalyst for propylene dimerization, characterized in that, The invention includes a carrier and an active metal loaded on the carrier; wherein the carrier is a mixture of alkali metal carbonates and metal oxides modified with an aliphatic alkyl dimethyl tertiary amine solvent as an adjuvant, and the active metal includes at least one of sodium and potassium.

2. The catalyst for propylene dimerization as described in claim 1, characterized in that, The alkali metal carbonate in the carrier is potassium carbonate; the metal oxide in the carrier is magnesium oxide, calcium oxide, or a mixture of the two; the fatty alkyl dimethyl tertiary amine solvent aid is tetraalkyl dimethyl tertiary amine, octaalkyl dimethyl tertiary amine, decaalkyl dimethyl tertiary amine, dodecyl dimethyl tertiary amine, tetradecyl dimethyl tertiary amine, or hexadecyl dimethyl tertiary amine.

3. The catalyst for propylene dimerization as described in claim 1, characterized in that, In the carrier, the mass content of the metal oxide is 1-15% based on the mass of the alkali metal carbonate; the mass content of the aliphatic alkyl dimethyl tertiary amine solvent is 5-400% based on the mass of the mixture of alkali metal carbonate and metal oxide; and the mass content of the active metal is 0.25-20% based on the mass of the carrier.

4. The method for synthesizing the propylene dimerization catalyst according to any one of claims 1-3, characterized in that, Alkali metal carbonates and metal oxides are mixed and sieved to obtain a particulate support mixture. This mixture is then mixed with a fatty alkyl dimethyl tertiary amine solvent. The resulting paste is first vacuum dried in air at 85-95°C, then calcined, and then cooled to 80-85°C in a nitrogen atmosphere. The alkali metal is then molten and loaded, and then heated and kept at a constant temperature to obtain a uniformly distributed catalyst. The catalyst is then cooled to room temperature and ready for use.

5. The synthesis method as described in claim 4, characterized in that, The sieve size is 15–60 μm.

6. The synthesis method according to claim 4, characterized in that, The mass ratio of the mixture to the fatty alkyl dimethyl tertiary amine solvent is 0.2 to 5.

7. The synthesis method according to claim 4, characterized in that, The calcination is specifically carried out at 400-950℃ for 1-5 hours; the mass content of alkali metal molten and loaded on the carrier after calcination is 0.5-25%; the reheating and constant temperature after calcination is specifically carried out at 150-350℃ for 0.5-4 hours.

8. A method for the dimerization of propylene to 4-methyl-1-pentene, characterized in that, The propylene dimerization catalyst according to any one of claims 1-3 is packed into a fixed-bed reactor. The vaporized propylene is first purified and then enters the fixed-bed reactor to react. The isomers are separated and removed to obtain the target product 4-methyl-1-pentene.

9. The method as described in claim 8, characterized in that, The propylene raw material is vaporized by heating or reducing pressure; purification is achieved through adsorption; the reaction operating temperature is 100–250°C; the reaction operating pressure is 5–20 MPa; and the reaction space velocity is 0.5–4 h⁻¹. -1 .

10. The method as described in claim 8, characterized in that, The separation is specifically distillation, using a plate column or a packed column, and employing atmospheric distillation or vacuum distillation.

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