An ethylene selective tetramerization catalyst composition and preparation method thereof

Abstract

The present invention discloses an ethylene selective tetramerization catalyst composition and its preparation method. While maintaining the two main components, a transition metal compound and an alkyl aluminum co-catalyst, unchanged, two novel ligands are synthesized for the first time. Specifically, the ethylene tetramerization catalyst composition comprises a chromium metal salt, a novel ligand compound, and an alkyl aluminum. These two ligands possess suitable electron-donating capabilities and can effectively form a dual-center active center with metallic chromium, resulting in high activity. Furthermore, their spatial configuration effectively suppresses the formation of the byproduct polyethylene, facilitating long-term reaction operation.

Description

Technical Field

[0001] The invention belongs to the field of ethylene oligomerization preparation, and particularly relates to an ethylene selective tetramerization catalyst composition and a preparation method thereof. Background Art

[0002] Linear α-olefins (LAOs) are important organic chemical raw materials and intermediates. They can be used to produce comonomers of high-density polyethylene, linear low-density polyethylene and polyolefin elastomers. They can also be used as raw materials for the production of fine chemicals such as high-end fully synthetic lubricants, surfactants and plasticizers.

[0003] Sinopec has already commercialized 1-butene through 2-butene isomerization, and Axens has also achieved commercialization of 1-butene through ethylene dimerization. Four companies worldwide have commercialized 1-hexene through ethylene trimerization: Chevron Phillips, Sinopec, PetroChina, and Mitsui Chemicals. Only Sasol has commercialized ethylene tetramerization. Ethylene pentamerization to 1-decene is currently commercialized worldwide.

[0004] In recent years, with the increasing application of materials such as linear low-density polyethylene, high-density polyethylene and polyolefin elastomers, the consumption of linear α-olefin (LAO) monomers such as 1-hexene and 1-octene used to synthesize linear low-density polyethylene has also increased significantly.

[0005] As an important linear α-olefin (LAO) organic monomer, 1-octene is an important component for synthesizing high-value or high-performance polymers, such as linear low-density polyethylene and polyolefin elastomers. Through copolymerization with ethylene, it can significantly improve the mechanical properties, optical properties, impact resistance and elasticity of polyethylene. In addition, 1-octene can also be used to synthesize plasticizers, fatty acids, detergents and lubricant additives.

[0006] Although 1-octene has a very high value, the current method for producing 1-octene is still non-selective oligomerization. Unlike 1-hexene, which has achieved high selective oligomerization production (1-hexene product selectivity is greater than 90%), the distribution of ethylene non-selective oligomerization products conforms to the Schulz-Flory distribution, which can not only produce 1-octene, but also produce a large amount of C4-C 20The olefin product, 1-octene, has a very low selectivity, not exceeding 30%. Shell's US Patent No. 3,676,523A, uses a nickel metal catalyst to polymerize ethylene, achieving an 1-octene selectivity of 11%. US Patent No. 6,184,428B2 uses a nickel compound to catalyze ethylene polymerization, achieving a 19% 1-octene selectivity. Japanese Patent No. JP2002121157A uses a zirconium metal catalyst to catalyze ethylene polymerization, achieving a 15% 1-octene selectivity. Chinese Patent No. CN101816951B discloses a Zr complex catalyst with a C8 selectivity of up to 24.37%, and Chinese Patent No. CN101569865B discloses a Zr complex catalyst with a C8 selectivity of up to 27.28%.

[0007] In addition to the above-mentioned non-selective polymerization of ethylene, there are also a large number of laboratory studies on the selective polymerization of ethylene. For example, patents CN102040624B, CN102451759B, CN103100420A, CN105268480B, CN105498840B, CN105562095B, ​​CN105562101B, CN105562102B, CN105562103B, CN105566037B, and CN107282128B applied for by Sinopec, CN103285926A of PetroChina, CN 110801864 A of Merrill, and US10539517, US10538088, US11629533, and US11993396 of Sasol all disclose the use of a chromium compound / ligand / promoter catalyst system for selective ethylene oligomerization, with the selectivity of 1-octene in the product being greater than 70%.

[0008] The applicant has also conducted research on ethylene trimerization and tetramerization. By synthesizing new ligands and improving catalyst formulations, they have achieved goals such as increasing the selectivity of the target products, 1-hexene or 1-octene, reducing polymer selectivity, and improving catalyst activity. The following patents have been applied for: CN112264106A, CN112517080A, CN113880879A, CN113880881A, CN114011469A, CN113996343A, CN114225968A, and CN114789067A.

[0009] Currently, there are five mature, non-selective α-olefin production processes globally: Shell, Chevron, Gulf, Ethyl, and Linde. Their primary product range extends from C4 to C20. However, these processes suffer from a wide product distribution, poor selectivity for specific products, and the high energy consumption required to separate high-purity α-olefins makes it difficult to meet market demand for high-purity LAOs.

[0010] Most of the ligands in the ethylene tetramerization catalysts that have been disclosed or reported so far are of PNP type structure. The synthesis process is relatively complicated and it is very easy to absorb water and cause deactivation. In addition, a small amount of polyethylene by-products accumulate and easily clog the pipes and control valves in the reaction system, which becomes the main reason affecting the long-term operation of the catalytic system.

[0011] The ethylene tetramerization catalyst composition consists of an organometallic salt, a ligand, and an alkylaluminum co-catalyst. The spatial configuration and electron-donating properties of the ligands are key factors influencing catalytic performance. Based on this, the present invention synthesizes two novel ligands for the first time, while retaining the two main components, a transition metal compound and an alkylaluminum co-catalyst. Specifically, the present invention comprises a chromium metal salt, a novel ligand compound, and an alkylaluminum to form an ethylene tetramerization catalyst composition. These two ligands possess suitable electron-donating properties and can effectively form a dual-center active center with metallic chromium, resulting in high activity. Furthermore, their spatial configuration effectively suppresses the formation of the byproduct polyethylene, facilitating long-term reaction operation. Summary of the Invention

[0012] To address the above-mentioned technical problems, the present invention discloses a method for preparing an ethylene tetramerization catalyst and its application. The present invention relates to a catalyst for ethylene tetramerization comprising a transition metal compound (a), a ligand compound (b), and an alkylaluminum cocatalyst (c), and its application. The ethylene oligomerization catalyst system, comprising two novel phosphorus-containing compounds as ligands, exhibits advantages such as high catalytic activity, high 1-octene selectivity, low polyethylene byproduct content in the product, and reduced costs in industrial production.

[0013] The structures of the two new ligands are shown below:

[0014]

[0015] The present invention claims an ethylene oligomerization catalyst composition, which is composed of a transition metal compound a, a ligand b and an alkyl aluminum cocatalyst c, and the catalyst composition is used to catalyze ethylene oligomerization reactions:

[0016] Transition metal compound a: the transition metal compound is at least one selected from chromium compounds, molybdenum compounds, iron compounds, titanium compounds, zirconium compounds and nickel compounds, preferably at least one of chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride or di(tetrahydrofuran)chromium dichloride;

[0017] Ligand b: Wherein X and Y are the same or different and are selected from sulfur or oxygen; R1, R2, R3 and R4 are the same or different and are selected from hydrogen, alkyl, alkoxy, cycloalkyl or halogen; or the structure of ligand b is wherein X and Y are the same or different and are selected from sulfur or oxygen; R is selected from hydrogen, alkyl, alkoxy, cycloalkyl or halogen;

[0018] Auxiliary agent c: one of methylaluminoxane, modified methylaluminoxane, dried methylaluminoxane, triethylaluminum, and trimethylaluminum.

[0019] Furthermore, the molar ratio of the alkyl aluminum co-catalyst to the transition metal compound is 100:1 to 1000:1;

[0020] Furthermore, the molar ratio of the ligand compound to the transition metal compound is 0.01:1 to 100:1; preferably 0.1:1 to 10:1;

[0021] Furthermore, the application of the ethylene tetramerization catalyst: the ethylene tetramerization reaction is mainly carried out in an inert solvent, the catalyst composition is prepared in proportion, and injected into the reaction system in sequence in the form of a homogeneous catalyst or mixed in advance and uniformly injected, and then the ethylene pressure is increased to allow it to fully contact with the catalyst composition to carry out ethylene tetramerization. The reaction conditions are: temperature 30-150°C, pressure 0.5-20MPa, and time 0.1-2h.

[0022] Furthermore, the solvent includes alkanes or aromatic hydrocarbons; preferably, the solvent includes benzene, toluene, cyclohexane, methylcyclohexane, n-heptane, and n-hexane.

[0023] Furthermore, a preparation method and application of a catalyst composition for preparing 1-octene by tetramerization of ethylene includes the following steps:

[0024] (1) Catalyst preparation: Weigh a certain amount of chromium salt, ligand and alkyl aluminum reagent and dissolve them in a dehydrated solvent to prepare three solutions for use;

[0025] (2) Before the reaction, the reactor body and lining were placed in an oven at 120°C and dried overnight. The reactor body and lining were then connected to the evaluation system, sealed, and heated to 100°C under vacuum conditions for 1 hour (with the tail gas valve closed) to remove residual water, oxygen, and oxygen-containing impurities. The temperature was then set to the reaction temperature and allowed to cool naturally while nitrogen was filled and then vacuumed. This process was repeated three times to ensure that the air was completely replaced. The nitrogen was then removed using a vacuum pump and filled with ethylene. This process was repeated three times to ensure that the reactor body was filled with ethylene.

[0026] (3) Open the tail gas valve, and use a syringe to inject the solvent and the additional alkyl aluminum co-catalyst in sequence under stirring conditions. After the temperature stabilizes to the reaction temperature, use a syringe to inject the dehydrated solvent, alkyl aluminum reagent, ligand solution, and chromium salt solution in sequence, close the tail gas valve, adjust the pressure reducing valve, start timing after the pressure rises to the predetermined pressure value, and record the mass flow meter data. After a certain reaction time, turn off the ethylene gas, stop the reaction, close the air inlet valve, remove the reactor body, and immerse it in an ice water bath to cool the reactor to below 10°C.

[0027] (4) After opening the tail gas valve to release the pressure, inject 5 ml of 10% HCl / ethanol solution under stirring to quench the alkyl aluminum co-catalyst, and then weigh and record the weight. Take a small amount of liquid phase product and analyze the product using GC-MS. Filter the remaining sample, weigh the filter paper in advance and record the mass. Then scrape the polymer on the stirring blade with a spoon, wash it with solvent and put it into a beaker. Place the obtained polymer in a vacuum oven at 60°C and dry it overnight. Weigh it separately and calculate the mass of the polymer. According to the MS, the component types can be calibrated. According to the GC results combined with the mass of the liquid phase product and the mass of the polymer, the selectivity of each product and the catalyst activity can be calculated.

[0028] The advantages of the present invention are:

[0029] (1) For the first time, o-phenylenedisulfide diphenylphosphine compounds, m-phenylenedisulfide diphenylphosphine compounds, 1,2-bis(diphenylphosphinooxy)benzene compounds, or 1,3-bis(diphenylphosphinooxy)benzene compounds were used as ligands in an ethylene oligomerization catalyst system;

[0030] (2) High selectivity for 1-octene in the product;

[0031] (3) The polyethylene content in the product is extremely low; the catalyst activity is extremely high. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the H NMR spectrum of o-phenylenedisulfide diphenylphosphine;

[0033] Figure 2 This is the NMR phosphine spectrum of o-phenylenedisulfide diphenylphosphine;

[0034] Figure 3 is the hydrogen nuclear magnetic resonance spectrum of 1,2-bis(diphenylphosphinooxy)benzene;

[0035] Figure 4 is the NMR phosphine spectrum of 1,2-bis(diphenylphosphinooxy)benzene;

[0036] Figure 5 is the H NMR spectrum of m-phenylenedisulfide diphenylphosphine;

[0037] Figure 6This is the NMR phosphine spectrum of m-phenylenedisulfide diphenylphosphine;

[0038] Figure 7 is the hydrogen nuclear magnetic resonance spectrum of 1,3-bis(diphenylphosphinooxy)benzene;

[0039] Figure 8 This is the NMR phosphine spectrum of 1,3-bis(diphenylphosphinooxy)benzene. DETAILED DESCRIPTION

[0040] To make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0041] Example 1 Synthesis of o-phenylenedisulfide diphenylphosphine ligand

[0042] The preparation of o-phenylenedisulfide diphenylphosphine compounds is through a substitution reaction on the benzene ring. When 1,2-dimercaptobenzene and sodium hydride react in a ratio of (1:2), the following reaction occurs:

[0043]

[0044] The specific synthesis steps are as follows: A suspension of NaH (179 mg, 7.46 mmol) in THF (5 mL) was slowly added to a solution of 1,2-dimercaptobenzene (510 mg, 3.58 mmol) in THF (50 mL). The NaH residue was washed with an additional 5 ml of tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h, and Ph2PCl (1.18 g, 7.73 mmol) was added. The resulting mixture was stirred for another hour before all volatile substances were removed in vacuo. Extraction with n-hexane (3×20 mL) and removal of the solvent in vacuo gave the desired ligand (93%, 3.33 mmol). The ligand was characterized by hydrogen spectrum and phosphine spectrum ( Figure 1 and Figure 2 ), and its characteristic H NMR spectrum and phosphine spectrum peaks can prove the successful preparation of the compound.

[0045] Example 2 Synthesis of 1,2-bis(diphenylphosphinooxy)benzene ligand

[0046] The preparation of 1,2-bis(diphenylphosphinooxy)benzene compounds is through a substitution reaction on the benzene ring. When catechol and diphenylphosphine chloride react in a ratio of (1:2), the following reaction occurs:

[0047]

[0048] The synthesis procedure is as follows: Pure chlorodiphenylphosphine (2.1 g, 9.5 mmol) was added dropwise to a solution of 1,2-benzenediol (0.5 g, 4.5 mmol) and triethylamine (1 g, 9.9 mmol) in tetrahydrofuran (30 mL). The reaction was allowed to proceed at room temperature under nitrogen for 10 minutes. The resulting pale suspension was stirred overnight. The precipitate was removed by filtration, and the solvent was evaporated under vacuum to yield a yellow, amorphous residue. The product was extracted with hot, degassed hexane (3 x 20 mL) under nitrogen, yielding a partially brown oil. Volatiles were evaporated to yield a nearly colorless, moisture- and air-sensitive, viscous oil (1.5 g, 71%). H NMR and phosphine spectra: 31P{1H}NMR (CDCl3; δ): 113.1 (s). 1H NMR (CDCl3; δ): 7.59 (dd, 3JH, H=7.5 Hz (av), 8H, meta Ph), 7.39-7.30 (m, 12H, ortho and para Ph), 7.14 (m, 2H, 3-HC6H4), 6.91 (m, 2H, 4-H C6H4).

[0049] Example 3 Synthesis of m-phenylenedisulfide diphenylphosphine ligand

[0050] The preparation of m-phenylenedisulfide diphenylphosphine compounds is through a substitution reaction on the benzene ring. When 1,3-dimercaptobenzene and sodium hydride react in a ratio of (1:2), the following reaction occurs:

[0051]

[0052] A suspension of NaH (179 mg, 7.46 mmol) in THF (5 mL) was slowly added to a solution of 1,3-dimercaptobenzene (510 mg, 3.58 mmol) in THF (50 mL). The NaH residue was washed with an additional 5 mL of tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h and Ph2PCl (1.18 g, 7.73 mmol) was added. The resulting mixture was stirred for an additional hour before all volatiles were removed in vacuo. Extraction with n-hexane (3×20 mL) and removal of the solvent in vacuo gave the desired ligand (93%, 3.33 mmol). The ligand was characterized by H NMR and phosphine NMR ( Figure 5 and Figure 6 ), and its characteristic H NMR spectrum and phosphine spectrum peaks can prove the successful preparation of the compound.

[0053] Example 4 Synthesis of 1,3-bis(diphenylphosphinooxy)benzene ligand

[0054] The preparation of 1,3-bis(diphenylphosphinooxy)benzene compounds is through a substitution reaction on the benzene ring. When resorcinol and diphenylphosphine chloride react in a ratio of (1:2), the following reaction occurs:

[0055]

[0056] The specific synthesis steps are as follows: Dissolve resorcinol (3.5 g, 32 mmol) in 100 ml of toluene, then add triethylamine (9.3 ml, 67 mmol). Then, add chlorodiphenylphosphine (14.78 g, 67 mmol) in 50 ml of toluene dropwise at room temperature. After 3 hours, filter the reaction mixture, collect the filtrate, and remove the solvent in vacuo to obtain a white solid. Yield: 11.6 g (75%). 1 HNMR (400MHz, C6D6): 87.6-7.4 (m, 20H, PPh2), 7.19 (m, lH, 2-H), 6.98 (m, lH, 5-H), 6.84 (m, 2H, 4-6-H) 31 P(1H)NMR(400MHz,C6D6):113.

[0057] Example 5:

[0058] The ethylene oligomerization reaction was carried out in a high-pressure stainless steel reactor. Before the reaction, the reactor was oven-dried at 120°C overnight, connected to the evaluation system, sealed, and heated to 100°C under vacuum for 1 hour (with the tail gas valve closed) to remove residual water, oxygen, and oxygen-containing impurities. The temperature was then set to 80°C and allowed to cool naturally while nitrogen was filled and then vacuumed three times to ensure complete air displacement. The nitrogen was then removed using a vacuum pump and filled with ethylene, repeating this three times to ensure the reactor was completely filled with ethylene. Methylcyclohexane solvent and the catalyst composition (molar ratio of chromium isooctanoate: diphenylphosphine disulfide: methylaluminoxane (MAO) = 1:1.2:1000) were then added. The reaction pressure was maintained at 2 MPa. After 1 hour, the reaction was terminated. The air inlet valve was closed, the reactor was removed, and immersed in an ice-water bath to cool to below 10°C. After opening the tail gas valve to release pressure, inject 5 mL of 10% HCl / ethanol solution under stirring to quench the alkyl aluminum. The weight is then weighed and recorded. A small amount of the liquid product is taken for analysis using GC-MS. The remaining sample is filtered, and the filter paper is weighed and recorded in advance. The polymer on the stirring paddle is then scraped off with a spoon and washed with solvent into a beaker. The resulting polymer is placed in a vacuum oven at 60°C overnight and weighed separately to calculate the mass of the polymer. Based on the MS calibration component types, the GC results, combined with the mass of the liquid product and the polymer, can be used to calculate the selectivity of each product and the catalyst activity. The data results are shown in Table 1.

[0059] Example 6:

[0060] Same as Example 5, except that the reaction temperature was 60°C. The data results are shown in Table 1.

[0061] Example 7:

[0062] Same as Example 5, except that methylcyclohexane was replaced by cyclohexane. The data results are shown in Table 1.

[0063] Example 8:

[0064] Same as Example 5, except that o-phenyl disulfide was replaced by 1,2-bis(diphenylphosphinooxy)benzene. The data results are shown in Table 1.

[0065] Example 9:

[0066] Same as Example 5, except that o-phenylenedisulfide diphenyl phosphine was replaced by m-phenylenedisulfide diphenyl phosphine. The data results are shown in Table 1.

[0067] Example 10:

[0068] Same as Example 5, except that o-phenyl disulfide diphenylphosphine was replaced with 1,3-bis(diphenylphosphinooxy)benzene. The data results are shown in Table 1.

[0069] Comparative Example 1:

[0070] Same as Example 5, except that the ligand was changed to PNP (the synthesis reference of PNP is (A. Bollmann, K. Blann, JT Dickon, et al, J. Am. Chem. Soc. 126 (2004) 14712-14713)). The data results are shown in Table 1.

[0071] Table 1 Summary of reaction conditions and reaction performance of the embodiments of the present invention and comparative examples.

[0072]

[0073]

[0074] As shown in Table 1, using phosphine-containing compounds with S or O as ligands for ethylene tetramerization exhibits higher catalytic activity than traditional carbon- and nitrogen-containing PNPs. While maintaining high 1-octene selectivity, it can reduce the selectivity of the byproduct polyethylene and reduce wall buildup, thus facilitating long-term operation. Since S and O are soft bases, C and N are hard bases, and transition metals are soft acids, according to the theory of hard and soft acids, S and O have stronger coordination with transition metals, increasing the rigidity between the ligand and the metal center, thereby enhancing catalytic activity.

[0075] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. An ethylene selective tetramerization catalyst composition, characterized in that: The ethylene selective tetramerization catalyst composition comprises a transition metal compound, a ligand and an alkyl aluminum cocatalyst; wherein the transition metal compound is selected from at least one of chromium compounds, molybdenum compounds, iron compounds, titanium compounds, zirconium compounds and nickel compounds; The ligand is 、 、 、 One of the following; The alkyl aluminum cocatalyst is one of methylaluminoxane, modified methylaluminoxane, triethylaluminum and trimethylaluminum.

2. The ethylene selective tetramerization catalyst composition according to claim 1, characterized in that The transition metal compound is at least one of chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride, and di(tetrahydrofuran)chromium dichloride.

3. The ethylene selective tetramerization catalyst composition according to claim 1, characterized in that: The molar ratio of the alkyl aluminum co-catalyst to the transition metal compound is 100:1 to 1000:

1.

4. The ethylene selective tetramerization catalyst composition according to claim 1, characterized in that: The molar ratio of the ligand to the transition metal compound is 0.01:1 to 100:

1.

5. The ethylene selective tetramerization catalyst composition according to claim 4, characterized in that: The molar ratio of the ligand to the transition metal compound is 0.1:1 to 10:

1.

6. Use of the catalyst composition according to claim 1 in the selective tetramerization of ethylene, characterized in that: The ethylene tetramerization reaction is carried out in an inert solvent. The catalyst composition is injected into the reaction system in the form of a homogeneous catalyst in sequence or mixed in advance and uniformly injected. Then the ethylene pressure is increased to allow it to fully contact with the catalyst composition to carry out ethylene tetramerization. The reaction conditions are: temperature 30~150 o C, pressure 0.5~20MPa, time 0.1~2h.

7. The use according to claim 6, characterized in that: Solvents include benzene, toluene, cyclohexane, methylcyclohexane, n-heptane, and n-hexane.

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