A bisphosphonophenylamine tridentate ligand compound and its application

Abstract

This invention discloses a bisphosphonophenylamine tridentate ligand compound, which is prepared from diphenylamine compounds, elemental bromine, n-butyllithium, organophosphorus compounds, etc. This ligand compound can be combined with transition metal compounds and aluminum-containing additives to form a catalyst composition for the catalytic reaction of ethylene tetramerization to 1-octene, exhibiting advantages such as high catalytic activity, high 1-octene selectivity, and low deactivation at high temperatures.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a bisphosphine phenylamine tridentate ligand compound and its applications. Background Technology

[0002] Currently, China has made breakthroughs in the technologies for preparing 1-butene through ethylene dimerization and 1-hexene through ethylene trimerization, and has successfully achieved industrial-scale production. In the field of selective ethylene tetramerization, Satellite Petrochemical announced in 2023 that its independently developed technology for preparing 1-octene through ethylene tetramerization had passed pilot-scale evaluation, but industrial-scale production has not yet been completed. Globally, only Sasol has achieved industrial-scale production of 1-octene through ethylene tetramerization. Furthermore, in the field of selective oligomerization of ethylene to prepare higher-carbon α-olefins (such as ethylene pentamerization to prepare 1-decene), industrialization has not yet been achieved globally, and related technologies require further research.

[0003] In the market, the widespread application of linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and polyolefin elastomers (POE) has led to a significant increase in the consumption of linear α-olefin (LAO) monomers such as 1-hexene and 1-octene, which are required for the synthesis of these materials, with 1-octene being the most representative. Compared to LLDPE synthesized using 1-butene and 1-hexene as comonomers, LLDPE synthesized using 1-octene as a comonomer exhibits superior tensile and tear resistance and better optical properties due to the increased carbon chain length of the comonomer. On the other hand, POE synthesized by copolymerizing 1-octene with ethylene can significantly improve the material's mechanical properties, optical properties, and elasticity. However, current methods for producing 1-octene mainly rely on non-selective oligomerization, while the products of non-selective oligomerization of ethylene exhibit a Schulz-Flory distribution, generating a large amount of C4-C in addition to the target product, 1-octene. 20 The presence of olefins in ethylene results in very low selectivity for 1-octene, not exceeding 30%. Shell's patent US3676523A uses a nickel metal catalyst for ethylene oligomerization, achieving a 1-octene selectivity of 11%. Therefore, this type of process requires a large amount of energy for separating the oligomers and is difficult to obtain high-purity 1-octene.

[0004] Meanwhile, all currently disclosed technologies for the tetramerization of ethylene to produce 1-octene produce a certain amount of polyethylene as a byproduct. Taking the classic Cr / ((Ph)2PN(iPr)P(Ph)2) / MAO catalyst system as an example, this catalytic system produces 0.1%-2% polyethylene under different process conditions. If not controlled, as the equipment operates for longer periods, the polyethylene will adhere to the inner wall of the equipment, even causing pipe blockage, seriously affecting the long-term stable operation of the equipment. Furthermore, the above-mentioned catalytic system has poor heat resistance; when the reaction temperature exceeds 80℃, the catalyst activity drops sharply, making it difficult to solve the problems of polyethylene adhesion and pipe blockage by increasing the reaction temperature.

[0005] In summary, ethylene tetramerization has advantages over non-selective oligomerization of ethylene in the preparation of 1-octene. However, the polymer produced by the ethylene tetramerization reaction will increase the production cost due to its impact on the equipment. Therefore, developing catalysts with high temperature resistance and extremely low polyethylene content is the key to the ethylene tetramerization to 1-octene production. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a bisphosphonophenylamine tridentate ligand compound and its application. A catalyst composition composed of this compound is used to prepare 1-octene via ethylene tetramerization, exhibiting advantages such as high catalytic activity, high 1-octene selectivity, and low susceptibility to deactivation at high temperatures.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A bisphosphonophenylamine tridentate ligand compound has the following general structural formula:

[0009] In this context, R and R' are independently selected from any one of hydrogen, halogen, alkyl, alkenyl, and aryl.

[0010] The reaction flow for preparing the bisphosphine phenylamine tridentate ligand compound is as follows:

[0011] .

[0012] Its preparation method includes the following steps:

[0013] 1) At -35 °C, diphenylamine compounds were dissolved in glacial acetic acid (AcOH), bromine was added and stirred for 2 hours, then Na2S2O4 solution was added to the solution and stirred for 15 min. The solid was collected, washed three times with water, and then purified by crystallization with a methanol / chloroform mixture at -20 °C. The solid was then dried under vacuum at 50 °C to obtain bromophenylamine compounds.

[0014] 2) At -35 °C, the obtained bromophenylamine compound was dissolved in diethyl ether, n-butyllithium (n-BuLi) was added and the mixture was brought to room temperature and stirred for 3 h. The mixture was then cooled to -35 °C, and an organophosphine compound was added dropwise. The mixture was then brought to room temperature with stirring and maintained for 24 h. After drying, the solid was dissolved in toluene and stirred for 30 min. The solid was then filtered, washed, and dried to obtain the bisphosphine phenylamine tridentate ligand compound.

[0015] Furthermore, the molar ratio of diphenylamine compounds and elemental bromine used in step 1) is 1:1.2.

[0016] Furthermore, the concentration of the Na2S2O4 solution mentioned in step 1) is 0.5 mol / L, and the amount added is calculated based on the molar ratio of Na2S2O4 to diphenylamine compounds being 5:1.

[0017] Furthermore, in step 1), the volume ratio of methanol to chloroform in the mixture is 1:3.

[0018] Furthermore, in step 2), the molar ratio of bromophenylamine compounds, n-butyllithium, and organophosphorus compounds is 1:1.2:1.2.

[0019] The bisphosphine phenylamine tridentate ligand compound can be combined with transition metal compounds and aluminum-containing additives to form a catalyst composition for catalytic tetramerization of ethylene to prepare 1-octene.

[0020] Furthermore, the transition metal compound contains one or more of the transition metals chromium, molybdenum, iron, titanium, zirconium, and nickel, preferably at least one of chromium acetylacetonate, chromium isooctanoate, chromium tri(tetrahydrofuran)trichloride, or chromium tetrahydrofuran chloride.

[0021] Furthermore, the aluminum-containing additive is selected from one or more of triethylaluminum, trimethylaluminum, triisobutylaluminum, methylaluminoxane, modified methylaluminoxane, and ethylaluminoxane.

[0022] Furthermore, the molar ratio of the bisphosphine phenylamine tridentate ligand compound to the transition metal element in the transition metal compound is 0.01:1 to 100:1, preferably 0.1:1 to 10:1.

[0023] Furthermore, the molar ratio of the aluminum-containing additive to the transition metal element in the transition metal compound is 100:1 to 1000:1.

[0024] Furthermore, the specific application method involves adding the catalyst composition to an inert solvent and reacting it for 0.1 to 2 hours at 30 to 150°C and an ethylene pressure of 0.5 to 20 MPa.

[0025] Furthermore, the inert solvent includes alkanes or aromatics, preferably one of benzene, toluene, cyclohexane, methylcyclohexane, n-heptane, and n-hexane.

[0026] The significant advantages of this invention are:

[0027] (1) Unlike existing P-phenyl-N-pyridine (PNN) ligands, the bisphosphonophenylamine tridentate ligand provided in this invention has a P-phenyl-N-phenyl-P (PNP) structure, which is rigid, has strong coordination ability, and can form relatively stable complexes with transition metals. Furthermore, the electrons on its nitrogen atom are fed back to the phosphorus atom center through the two phenyl groups, making the ligand less prone to electron transfer reactions under high temperature conditions, thus enhancing the high-temperature resistance of the catalyst. By modifying the phosphorus and nitrogen atoms in bisphosphonophenylamine with various substituents, the electron density and steric hindrance around the central metal of the catalyst can be adjusted, thereby regulating the activity and selectivity of the catalyst. The ligand structure obtained in this invention is novel, easy to prepare, readily soluble in various organic solvents, and readily coordinates with metals.

[0028] (2) In the catalyst composition used in the ethylene polymerization reaction, the spatial configuration and electron-donating properties of the ligands are key factors affecting its catalytic performance. This invention is the first to use bisphosphine phenylamine tridentate compounds as ligands in the ethylene oligomerization catalyst system, and uses the catalyst composition composed of them to prepare 1-octene by ethylene tetramerization. The catalyst composition exhibits advantages such as high catalytic activity, high selectivity for 1-octene, low polymer selectivity, and low deactivation at high temperatures. Attached Figure Description

[0029] Figure 1 The 1H NMR spectrum of bis[2-(diisopropylphosphino)-4-tert-butylphenyl]amine prepared for the example.

[0030] Figure 2 The carbon NMR spectrum of bis[2-(diisopropylphosphino)-4-tert-butylphenyl]amine prepared for the example. Detailed Implementation

[0031] A bisphosphonophenylamine tridentate ligand compound, the preparation method of which includes the following steps:

[0032] 1) At -35 °C, diphenylamine compounds were dissolved in glacial acetic acid, and then bromine was added and stirred for 2 hours. Then, 0.5 mol / L Na2S2O4 solution was added to the solution at a molar ratio of Na2S2O4 to diphenylamine compounds of 5:1. The mixture was stirred for 15 min, the solid was collected, washed three times with water, and then purified by crystallization with a methanol / chloroform (1:3, v / v) mixture at -20 °C. The solid was then dried under vacuum at 50 °C to obtain bromophenylamine compounds.

[0033] 2) At -35 °C, the obtained bromophenylamine compounds were dissolved in diethyl ether, n-butyllithium (n-BuLi) was added, and the mixture was brought to room temperature and stirred for 3 h. Then, the temperature was lowered to -35 °C, and organophosphine compounds were added dropwise. The mixture was then brought to room temperature with stirring and maintained for 24 h. After drying, the resulting solid was dissolved in toluene and stirred for 30 min. The mixture was then filtered, washed, and dried to obtain the bisphosphine phenylamine tridentate ligand compound, whose general structural formula is as follows:

[0034] In this context, R and R' are independently selected from any one of hydrogen, halogen, alkyl, alkenyl, and aryl.

[0035] In step 1), the molar ratio of diphenylamine compounds to elemental bromine is 1:1.2. In step 2), the molar ratio of bromophenylamine compounds, n-butyllithium, and organophosphorus compounds is 1:1.2:1.2.

[0036] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0037] Example: Synthesis of bis[2-(diisopropylphosphino)-4-tert-butylphenyl]amine

[0038]

[0039] At -35 °C, 2 g of bis(2-bromo-4-tert-butylphenyl)amine (purchased from Aladdin) was dissolved in Et₂O, 5.5 mL of n-BuLi was added, and the mixture was heated to room temperature and stirred for 3 h. The temperature was then lowered to -35 °C, and 1.46 mL of di(isopropyl)phosphine chloride (purchased from Aladdin) was added dropwise. The mixture was heated to room temperature with stirring and maintained for 24 h. The solution was then dried under vacuum, dissolved in toluene, and the air in the solution was removed by degassing (V = 0.248 mL). The mixture was stirred for 30 min, filtered, dried under vacuum, washed with CH₃CN (2 × 20 mL), filtered, and dried to obtain 1.5 g of bis[2-(diisopropylphosphino)-4-tert-butylphenyl]amine, with a yield of 65%. The 1H NMR and 1C NMR spectra of the product are shown below. Figure 1 , 2 As shown.

[0040] Application Example 1:

[0041] Chromium isooctanoate, bis[2-(diisopropylphosphino)-4-tert-butylphenyl]amine prepared in the examples, and methylaluminoxane (MAO) were dissolved in dehydrated and deoxygenated methylcyclohexane to prepare corresponding solutions.

[0042] The ethylene oligomerization reaction was carried out in a high-pressure stainless steel reactor. Before the reaction, the reactor body was placed in an oven at 120 °C overnight. Then, the reactor body was connected to the evaluation system and sealed (with the tail gas valve closed), and evacuated at 105 °C for 1 h. The reactor was then naturally cooled to 50 °C, during which time it was purged three times with nitrogen and ethylene, respectively.

[0043] Ethylene was introduced into the reactor to a slightly positive pressure. Under stirring conditions, the solution of the prepared catalyst composition (the molar ratio of chromium isooctanoate, ligand and MAO in the catalyst composition was 1:1.2:1000) was injected into the reactor in sequence. After stirring for 2 minutes, the reactor pressure was adjusted to 2 MPa. After reacting for 1 hour, the reaction was stopped, the inlet valve was closed, the reactor body was quickly removed, and the reactor was immersed in an ice-water bath to cool it to below 10 °C.

[0044] After releasing the pressure to 0.1 MPa by opening the tail gas valve, 5 mL of 10% HCl ethanol solution was injected under stirring, and the weight was recorded. A small amount of the liquid phase product was analyzed by GC-MS. The remaining sample was filtered, and the resulting polymer was placed in a vacuum oven at 60 °C overnight. The polymer was collected, weighed, and its mass was recorded. The catalyst activity and selectivity were calculated based on the GC-MS results and the polymer mass. The data are shown in Table 1.

[0045] Application Example 2:

[0046] Same as in Application Example 1, except that the reaction temperature of 50°C was replaced with 100°C. The data results are shown in Table 1.

[0047] Application Example 3:

[0048] Same as Application Example 1, except that the solvent methylcyclohexane was replaced with cyclohexane. The data results are shown in Table 1.

[0049] Application Example 4:

[0050] Similar to Application Example 2, except that the pressure was changed from 2MPa to 4MPa. The data results are shown in Table 1.

[0051] Application Example 5:

[0052] Same as Application Example 1, except that the reaction time was changed from 1 hour to 30 minutes. The data results are shown in Table 1.

[0053] Application Example 6:

[0054] Chromium isooctanoate, bis[2-(diisopropylphosphino)-4-tert-butylphenyl]amine prepared in the examples, and methylaluminoxane (MAO) were dissolved in dehydrated and deoxygenated toluene to prepare corresponding solutions.

[0055] The ethylene oligomerization reaction was carried out in a high-pressure stainless steel reactor. Before the reaction, the reactor body was placed in an oven at 120 °C overnight. Then, the reactor body was connected to the evaluation system and sealed (with the tail gas valve closed), and evacuated at 105 °C for 1 h. The reactor was then naturally cooled to 60 °C, during which time it was purged three times with nitrogen and ethylene, respectively.

[0056] Ethylene was introduced into the reactor to a slightly positive pressure. Under stirring, the solution of the prepared catalyst composition (the molar ratio of chromium isooctanoate, ligand and MAO in the catalyst composition was 1:1.2:1000) was injected into the reactor in sequence. After stirring for 2 minutes, the pressure of the reactor was adjusted to 1 MPa. After reacting for 30 minutes, the reaction was stopped, the inlet valve was closed, the reactor body was quickly removed, and the reactor was immersed in an ice-water bath to cool it to below 10 °C.

[0057] After releasing the pressure to 0.1 MPa by opening the tail gas valve, 5 mL of 10% HCl ethanol solution was injected under stirring, and the weight was recorded. A small amount of the liquid phase product was analyzed by GC-MS. The remaining sample was filtered, and the resulting polymer was placed in a vacuum oven at 60 °C overnight. The polymer was collected, weighed, and its mass was recorded. The catalyst activity and selectivity were calculated based on the GC-MS results and the polymer mass. The data are shown in Table 1.

[0058] Application Comparative Example 1:

[0059] Similar to Application Example 1, except that the ligand used was changed to PNP (PNP synthesis reference (A.Bollmann, K. Blann, JT Dixon, et al, J. Am. Chem. Soc. 126 (2004) 14712–14713), data results are shown in Table 1.

[0060] Application Comparative Example 2:

[0061] The same application was used as Comparative Example 1, except that the reaction temperature was changed from 50℃ to 100℃. The data results are shown in Table 1.

[0062] Application Comparative Example 3:

[0063] Similar to Application Example 6, except that the ligand used was changed to PNN (the synthesis of PNN is described in patent 106853378A), and the data results are shown in Table 1.

[0064] Table 1 Summary of reaction conditions and reaction performance of the examples and comparative examples

[0065]

[0066] As shown in Table 1, the catalyst compositions using bis[2-(diisopropylphosphino)-4-tert-butylphenyl]amine as ligands prepared in the examples exhibit excellent catalytic performance in ethylene tetramerization under different conditions. Compared to PNP ligands, at low temperatures, the catalysts using the ligands in the examples showed comparable activity to those using PNP ligands (Comparative Example 1), but the catalysts using the ligands in the examples exhibited lower polymer selectivity. At high temperatures, the catalysts using the ligands in the examples maintained high activity, while the catalysts using PNP ligands showed an activity reduction of more than 50% at high temperatures (Comparative Example 2). Furthermore, compared to PNN ligands, the catalysts using the ligands in the examples showed significantly higher catalytic performance than those using PNN ligands (Comparative Example 3).

[0067] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. The application of a bisphosphine phenylamine tridentate ligand compound in the tetramerization of ethylene to prepare 1-octene, characterized in that, A catalyst composition consisting of a transition metal compound, the aforementioned bisphosphine phenylamine tridentate ligand compound, and an aluminum-containing additive is used to catalyze the tetramerization of ethylene to 1-octene. The transition metal compound is at least one of chromium acetylacetone, chromium isooctanoate, chromium tri(tetrahydrofuran)trichloride, or chromium tetrahydrofuran chloride. The chemical structural formula of the bisphosphine phenylamine tridentate ligand compound is as follows: ; The aluminum-containing additive is selected from one or more of triethylaluminum, trimethylaluminum, triisobutylaluminum, methylaluminoxane, modified methylaluminoxane, and ethylaluminoxane.

2. The application according to claim 1, characterized in that, The molar ratio of the aluminum-containing additive to the transition metal element in the transition metal compound is 100:1 to 1000:

1.

3. The application according to claim 1, characterized in that, The molar ratio of the bisphosphine phenylamine tridentate ligand compound to the transition metal element in the transition metal compound is 0.01:1 to 100:

1.

4. The application according to claim 1, characterized in that, The specific application method involves injecting the catalyst composition into an inert solvent and reacting it for 0.1 to 2 hours at 30 to 150°C and a gas pressure of 0.5 to 20 MPa.

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