WO2024244137A1 - Ethylene selective tetramer catalyst composition and preparation method therefor - Google Patents

Abstract

Disclosed in the present invention are an ethylene selective tetramer catalyst composition and a preparation method therefor. Two novel ligands are synthesized for the first time under the condition that two main components of a transition metal compound and an alkyl aluminum cocatalyst are kept unchanged. That is, in the present invention, a chromium metal salt, a novel ligand compound, and alkyl aluminum together form an ethylene tetramer catalyst composition. The two ligands have proper electron donating ability, can be effectively constructed into a double-center active center with metal chromium, and have high activity, and the spatial configuration of the ligands can effectively inhibit generation of by-product polyethylene, facilitating long-period operation of a reaction.

Description

A kind of ethylene selective tetramerization catalyst composition and preparation method thereof Technical Field

The invention belongs to the field of ethylene oligomerization preparation, and specifically relates to an ethylene selective tetramerization catalyst composition and a preparation method thereof.

Background Art

Linear alpha-olefins (LAO) 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 high-end fully synthetic lubricants, surfactants, plasticizers and other fine chemicals. Advanced and mature LAO production technology is mainly in the hands of world-renowned companies such as ChevronPhillips, Shell, Sasol, Idemitsu, SABIC/Linde, INEOS, etc. China started relatively late in this field and is still in the development stage overall. Foreign advanced technology is blocked to China, and China cannot introduce mature LAO production processes. Therefore, it is of great significance to independently develop domestic technology.

At present, Sinopec's 2-butene isomerization has achieved the industrialization of 1-butene, and Axens has also achieved the industrialization of 1-butene by using ethylene dimerization. Four companies in the world have achieved the industrialization of ethylene trimerization to produce 1-hexene, namely ChevronPhillips, Sinopec, PetroChina and Mitsui Chemicals. At present, only Sasol has achieved the industrialization of ethylene tetramerization. At present, no one in the world has achieved the industrialization of ethylene pentamerization to produce 1-decene.

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. In 2022, China's α-olefin production capacity of C5 and above will be 95,000 tons/year, and the output will be 45,000 tons, mainly contributed by the 1-hexene project. In addition to importing pure α-olefins, China imports a large amount of α-olefin derivatives such as LLDPE/HDPE, PAO, POE, etc. every year, so the equivalent α-olefin consumption and external dependence are much greater than the above values.

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. By copolymerizing 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.

Although 1-octene has a very high value, the current method for producing 1-octene is still non-selective polymerization, unlike 1-hexene, which has achieved high selective polymerization production (1-hexene product selectivity greater than 90%). The distribution of non-selective polymerization products conforms to the Schulz-Flory distribution, and not only 1-octene can be obtained, but also a large amount of _C4 - _C20 olefin products can be produced at the same time. The selectivity of 1-octene is very low, not exceeding 30%. Shell's US3676523A uses a nickel metal catalyst to carry out ethylene polymerization, and the selectivity of 1-octene is 11%. US Patent US6184428B2 uses a nickel compound to catalyze the ethylene polymerization product, and the selectivity of 1-octene is 19%. Japanese Patent JP2002121157A uses a zirconium metal catalyst to catalyze the ethylene polymerization product, and the selectivity of 1-octene is 15%. Chinese Patent CN101816951B discloses a Zr complex catalyst, in which the selectivity of C8 can reach up to 24.37%; Chinese Patent CN101569865B discloses a Zr complex catalyst, in which the selectivity of C8 can reach up to 27.28%.

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, CN110801864A of Merrill, US10539517, US10538088, US11629533, and US11993396 of Sasol all disclose the use of chromium compounds/ligands/auxiliary agent catalyst systems for selective polymerization of ethylene, and the selectivity of 1-octene in the product can be greater than 70%.

The applicant has also conducted relevant research on ethylene trimerization and tetramerization, and has achieved the goals of improving the selectivity of the target product 1-hexene or 1-octene, reducing the polymer selectivity, and improving the catalyst activity by synthesizing new ligands and improving catalyst formulations. The patents applied for are as follows: CN112264106A, CN112517080A, CN113880879A, CN113880881A, CN114011469A, CN113996343A, CN114225968A, CN114789067A.

Currently, there are five mature non-selective α-olefin production processes in the world, including Shell, Chevron, Gulf, Ethyl and Linde, with a production capacity of 2.1 million tons/year, and the main products range from C4 to C20. However, this type of production process has a wide distribution range of products, poor selectivity for specific products, and requires a lot of energy to separate high-purity α-olefins, which is difficult to meet the market demand for high-purity LAO.

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.

Technical issues

The ethylene tetramerization catalyst composition is composed of an organic metal salt, a ligand and an alkyl aluminum cocatalyst. The spatial configuration and electron-donating properties of the ligand are key factors affecting the catalytic performance. While the two main components of the transition metal compound and the alkyl aluminum co-catalyst remain unchanged, two new ligands are synthesized for the first time. That is, the ethylene tetramerization catalyst composition of the present invention is composed of chromium metal salt, new ligand compound and alkyl aluminum. These two ligands have appropriate electron donating ability and can effectively form a dual-center active center with metal chromium, which has high activity. At the same time, their spatial configuration can effectively inhibit the formation of by-product polyethylene, which is conducive to the long-term operation of the reaction.

Technical Solutions

In order to solve the above technical problems, the present invention discloses a method for preparing an ethylene tetramerization catalyst and its application. The present invention relates to a catalyst composed of a transition metal compound a, a ligand compound b and an alkyl aluminum cocatalyst c for ethylene tetramerization and its application. The ethylene oligomerization catalyst system with two novel phosphorus-containing compounds as ligands claimed in the present invention has the advantages of high catalyst activity, high 1-octene selectivity, less polyethylene byproduct in the product, and can reduce costs in industrialization when catalyzing ethylene oligomerization reaction.

The structures of the two new ligands are shown below:

The present invention claims an ethylene polymerization 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 for catalyzing ethylene polymerization reaction: transition metal compound a: the transition metal compound is selected from at least one of 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;

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;

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

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

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;

Further, the application of ethylene tetramerization catalyst: the ethylene tetramerization reaction is mainly carried out in an inert solvent, the catalyst composition is prepared in proportion, and is 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 make it 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.

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

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

(1) Catalyst preparation: Weigh a certain amount of chromium salt, ligand and alkyl aluminum reagent respectively and dissolve them in a solvent that has been treated with water to prepare three solutions for use;

(2) Before the reaction, place the reactor body and lining in an oven at 120°C and dry overnight, connect to the evaluation system, seal, and heat to 100°C for 1 hour under vacuum conditions (tail gas valve closed) to remove residual water, oxygen, and oxygen-containing impurities. Then set the temperature to the reaction temperature, let it cool naturally, fill with nitrogen, and then evacuate the reactor three times to ensure that the air has been replaced. Then use a vacuum pump to remove the nitrogen and fill it with ethylene. Repeat three times to ensure that the reactor is filled with ethylene.

(3) Open the tail gas valve, and inject the solvent and the additional alkyl aluminum co-catalyst in sequence using a syringe under stirring conditions. After the temperature stabilizes to the reaction temperature, inject the dehydrated solvent, alkyl aluminum reagent, ligand solution, and chromium salt solution in sequence using a syringe, close the tail gas valve, adjust the pressure reducing valve, and start timing after the pressure rises to a 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.

(4) After opening the tail gas valve to release the pressure, inject 5 ml of 10% HCl/ethanol solution under stirring conditions to quench the alkyl aluminum co-catalyst, and then weigh and record the weight. Take a small amount of liquid phase product and use GC-MS to analyze the product. Filter the remaining sample, weigh the filter paper in advance and record the mass, then scrape the polymer on the stirring paddle with a spoon and use The solvent was washed into a beaker, and the obtained polymer was placed in a vacuum oven at 60°C for overnight drying, and weighed separately to calculate the mass of the polymer. The component types can be calibrated according to MS, and the selectivity of each product and the catalyst activity can be calculated based on the GC results combined with the mass of the liquid phase product and the mass of the polymer.

Beneficial Effects

The advantages of the present invention are:

(1) For the first time, an o-phenylenedisulfide diphenylphosphine compound, an m-phenylenedisulfide diphenylphosphine compound, a 1,2-bis(diphenylphosphinooxy)benzene compound or a 1,3-bis(diphenylphosphinooxy)benzene compound is used as a ligand in an ethylene oligomerization catalyst system;

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

(3) The product contains very little polyethylene and the catalyst activity is extremely high.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a hydrogen nuclear magnetic resonance spectrum of diphenylphosphine disulfide;

Fig. 2 is the nuclear magnetic resonance phosphine spectrum of o-phenyl disulfide diphenyl phosphine;

FIG3 is a hydrogen nuclear magnetic resonance spectrum of 1,2-bis(diphenylphosphinooxy)benzene;

FIG4 is a nuclear magnetic resonance phosphine spectrum of 1,2-bis(diphenylphosphinooxy)benzene;

FIG5 is a hydrogen nuclear magnetic resonance spectrum of diphenyl phosphine disulfide;

FIG6 is a nuclear magnetic resonance phosphine spectrum of diphenyl phosphine disulfide;

FIG7 is a hydrogen nuclear magnetic resonance spectrum of 1,3-bis(diphenylphosphinooxy)benzene;

FIG8 is a NMR phosphine spectrum of 1,3-bis(diphenylphosphinooxy)benzene.

Embodiments of the present invention

In order 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.

Example 1 Synthesis of o-phenyl disulfide diphenylphosphine ligand

The preparation of o-phenyl disulfide diphenyl phosphine 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:

The specific synthesis steps are as follows: Suspend NaH (179 mg, 7.46 mmol) in THF (5 mL) Slowly add 1,2-dimercaptobenzene (510 mg, 3.58 mmol) in THF (50 mL). Wash the NaH residue with an additional 5 mL of THF. The reaction mixture is stirred at room temperature for 1 h and Ph ₂ PCl (1.18 g, 7.73 mmol) is added. The resulting mixture is stirred for another hour before all volatiles are removed in vacuo. Extraction with n-hexane (3×20 mL) and removal of the solvent in vacuo affords the desired ligand (93%, 3.33 mmol). The ligand was characterized by H NMR and phosphine spectra (Figures 1 and 2), and its characteristic H NMR and phosphine spectra peaks can prove the successful preparation of the compound.

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

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:

The specific synthesis steps are as follows: pure chlorodiphenylphosphine (2.1g, 9.5mmol) was added dropwise to a tetrahydrofuran (30mL) solution of 1,2-benzenediol (0.5g, 4.5mmol) and triethylamine (1g, 9.9mmol) and reacted at room temperature under nitrogen atmosphere for 10 minutes. The pale suspension was stirred overnight. The precipitate was removed by filtration and the solvent was evaporated under vacuum to obtain a yellow amorphous residue. The product was extracted with hot degassed hexane (3×20mL) under nitrogen to obtain a partially brown oily substance. The volatiles were evaporated to obtain a nearly colorless, moisture- and air-sensitive viscous oil (1.5g, 71%). Nuclear magnetic resonance characterization hydrogen spectrum and phosphine spectrum: 31P{1H}NMR (CDCl3; δ): 113.1 (s). 1HNMR (CDCl3; δ): 7.59 (dd, 3JH, H＝7.5Hz(av), 8H, metaPh), 7.39-7.30 (m, 12H, orthoandparaPh), 7.14 (m, 2H, 3-HC6H4), 6.91 (m, 2H, 4-HC6H4).

Example 3 Synthesis of m-phenylenedisulfide diphenylphosphine ligand

The preparation of isophenyl disulfide 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:

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 THF. The reaction mixture was stirred at room temperature for 1 h, and Ph ₂ PCl (1.18 g, 7.73 mmol). 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 afforded the desired ligand (93%, 3.33 mmol). The ligand was characterized by H NMR and phosphine spectra (Figures 5 and 6), and its characteristic H NMR and phosphine spectra peaks confirmed the successful preparation of the compound.

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

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:

The specific synthesis steps are as follows: Dissolve resorcinol (3.5 g, 32 mmol) in 100 ml toluene, and then add triethylamine (9.3 ml, 67 mmol). Then, add chlorodiphenylphosphine (14.78 g, 67 mmol) prepared in toluene (50 ml) 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 (400 MHz, C6D6): 87.6-7.4 (m, 20H, PPh ₂ ), 7.19 (m, 1H, 2-H), 6.98 (m, 1H, 5-H), 6.84 (m, 2H, 4-6-H) ³¹ P (1H) NMR (400 MHz, C6D6): 113.

Embodiment 5:

The ethylene polymerization reaction is carried out in a high-pressure stainless steel reactor. Before the reaction, the reactor body is placed in an oven at 120°C and dried overnight, connected to the evaluation system, sealed, and heated to 100°C for 1h under vacuum conditions (the tail gas valve is closed) to remove residual water, oxygen and oxygen-containing impurities. Then the temperature is set to 80°C, allowed to cool naturally, and nitrogen is filled at the same time, followed by vacuuming, repeated three times to ensure that the air has been replaced. Then the nitrogen is pumped away with a vacuum pump and filled with ethylene, repeated three times to ensure that the kettle is full of ethylene. Then the solvent methylcyclohexane and the catalyst composition (chromium isooctanoate: diphenyl phosphine disulfide: methylaluminoxane MAO in the catalyst composition = 1:1.2:1000, molar ratio) are added thereto in turn. The reaction pressure is controlled to 2MPa, and the reaction is stopped after 1h of reaction. The air inlet valve is closed, the reactor body is removed, and the reactor is immersed in an ice water bath to cool the reactor to below 10°C. After opening the tail gas valve to release the pressure, inject 5mL of 10% HCl/ethanol solution under stirring to quench the alkyl aluminum, then weigh and record the weight. Take a small amount of liquid phase product and use GC-MS to analyze the product. Filter the remaining sample, weigh the filter paper in advance and record the mass, then scrape the polymer on the stirring paddle with a spoon, wash it with solvent 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, and according to the GC results, the polymer can be calibrated. The selectivity of each product and the activity of the catalyst can be calculated by combining the mass of the liquid phase product and the mass of the polymer. The data results are shown in Table 1.

Embodiment 6:

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

Embodiment 7:

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

Embodiment 8:

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

Embodiment 9:

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

Embodiment 10:

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

Comparative Example 1:

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

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

As shown in Table 1, the use of phosphine-containing compounds with S or O as ligands for ethylene tetramerization has higher catalytic activity than traditional carbon and nitrogen-containing PNPs. While maintaining high 1-octene selectivity, it can reduce the selectivity of byproduct polyethylene and reduce wall hanging, which is conducive to 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 soft and hard acids and bases, S and O have stronger coordination ability with transition metals, which can improve the rigidity of the ligand and the metal center, thereby achieving the effect of improving catalytic activity.

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 (7)

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 co-catalyst; 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; Ligand is 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 ligand 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; The alkyl aluminum co-catalyst is one of methylaluminoxane, modified methylaluminoxane, drained methylaluminoxane, triethylaluminum, and trimethylaluminum. The ethylene selective tetramerization catalyst composition according to claim 1 is 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. The ethylene selective tetramerization catalyst composition according to claim 1 is characterized in that the molar ratio of the alkyl aluminum co-catalyst to the transition metal compound is 100:1 to 1000:1. The ethylene selective tetramerization catalyst composition according to claim 1 is characterized in that the molar ratio of the ligand to the transition metal compound is 0.01:1 to 100:1. The ethylene selective tetramerization catalyst composition according to claim 4 is characterized in that the molar ratio of the ligand to the transition metal compound is 0.1:1 to 10:1. The use of the catalyst composition according to claim 1 in the selective tetramerization of ethylene is characterized in that: the ethylene tetramerization reaction is carried out in an inert solvent, the catalyst composition is 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 make it fully contact with the catalyst composition to carry out ethylene tetramerization, and the reaction conditions are: temperature 30-150°C, pressure 0.5-20MPa, time 0.1-2h. The use according to claim 6 is characterized in that the solvent includes benzene, toluene, cyclohexane, methylcyclohexane, n-heptane and n-hexane.