RU2549833C1 - Catalytic complex of selective ethylene in 1-hexene trimerisation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: catalytic complex of selective ethylene in 1-hexene trimerisation includes: a chromium (III) compound with a diphosphine ligand of the general formula [CrCl₃((Ph₂P(1,2-C₆H₄)P(Ph)(1,2-C₆H₄)CH=CH₂)_-(L)], where L - tetrahydrofuran or water, chloride of tris(tetrahydrofuran)chromium is applied as a chromium (III) source, a solution of methylalumoxane is applied as an activator, with the complex components being in the following molar ratio: chromium compounds: activator= 0.02-0.12%:99.88-99.98%.

EFFECT: high productivity of selective ethylene trimerisation.

2 tbl, 11 ex

Description

The invention relates to organic chemistry, in particular to a technology for the trimerization of olefins, and in particular to a process for the selective production of 1-hexene by the trimerization of ethylene.

1-hexene is an important commercial starting material, widely used as a comonomer in the polymerization of ethylene to obtain linear low density polyethylene. In this case, special requirements are imposed on the purity of the α-olefin. Recent studies have been based on the search for catalytic systems, usually consisting of a mixture of chromium, ligand and activator compounds, which allow selective production of 1-hexene from ethylene, as opposed to previous oligomerization technologies, in which a number of α-olefins are formed according to the Schulz-Flory distribution.

Among the known technologies for the selective production of 1-hexene by trimerization of ethylene, the most high-performance catalytic complexes are systems based on mixtures of chromium compounds with PNP ligands. US 7141633 B2, 11.28.2006. But the claimed productivity of 1033.2 kg (1-hexene) / g _Cr · h is observed only in the first minutes of the process, in the future, the reaction rate is significantly reduced and productivity decreases.

In the closest analogue to the claimed catalytic complex - RU 2456077 C1, 07/20/2012, a similar catalytic system based on chromium compounds and stereospecific ligands having (S, S) - or (R, R) -isomer structure of P-C-C- is described P, allowing to increase the productivity and selectivity of trimerization.

The described technologies have the following disadvantages: the process is difficult to control, because the catalyst activity is greatest in the first minutes of the process, then drops sharply, and its real value is much less than the claimed; unbound ligands are present in the reaction mixture, which are products of the dissociation of the starting chromium compounds, which can interact with the activator and impair the performance of the process.

The technical task of the invention is the development of a productive catalytic complex for highly selective trimerization of ethylene in 1-hexene.

The technical result from the implementation of the invention is to achieve high performance trimerization of ethylene - 1914 kg (1-hexene) / g _Cr · h for the entire duration of the process (30 min), which is the highest indicator among the known catalytic systems.

The technical result is achieved by the fact that the catalytic complex for the selective trimerization of ethylene into 1-hexene includes: a chromium (III) compound with a diphosphine ligand of the general formula [CrCl ₃ ((Ph ₂ P (1,2-С ₆ Н ₄ ) Р (Ph) ( 1,2-C ₆ H ₄ ) CH = CH ₂ ) _- (L)], where L is tetrahydrofuran or water, the source of chromium (III) is Tris (tetrahydrofuran) chromium chloride, and the activator is a solution of methylaluminoxane, with the components of the complex are in the following molar ratio: chromium compounds: activator = 0.02-0.12%: 99.88-99.98%.

The task and technical result are achieved with the following methods for the preparation of compounds and a catalytic complex for the selective trimerization of ethylene into 1-hexene, and the conditions for the trimerization process.

Example 1. The synthesis of 2-bromostyrene (1) is carried out in accordance with the procedure described in S. Hibino, E. Sugino, Y. Adachi, K. Nomi, K. Sato. The alternative synthesis of isoquinoline nucleus using the thermal electrocyclic reaction of l-azahexa-1,3,5-triene system. Heterocycles, 1989, v. 28, p. 275-279.

All reactions are carried out in an inert atmosphere. The solvents are preliminarily purified by distillation in an argon atmosphere: tetrahydrofuran was distilled over ketopodium sodium, methylene chloride and ethyl acetate over CaH ₂ , hexane and toluene over sodium. 2-Bromobenzaldehyde (Acros, 97%) is used without further purification.

5.35 g (14.98 mmol) methyltriphenylphosphonium bromide are placed in a Schlenk flask, 50 ml of absolute tetrahydrofuran are added. The resulting suspension was cooled to 0 ° C and 9.36 ml of a 1.6 M solution of n-BuLi in hexane was slowly added to it. The yellow-orange mixture was stirred at 0 ° C for 40 minutes, then a solution of 2.52 g (13.6 mmol) of 2-bromobenzaldehyde was slowly added to the mixture at this temperature. A white-yellow precipitate forms. The mixture was stirred at room temperature for 16 hours, 50 ml of an aqueous NaCl solution was added, extracted twice with ethyl acetate, the organic phase was dried over magnesium sulfate, and the solvent was evaporated. A solid, yellow residue was applied to a silica gel column (Acros, 60-200 μm), the first colorless fraction was eluted with hexane / ethyl acetate = 4/1, and the solvent was evaporated. 1.62 g (yield 65 wt%) of 2-bromostyrene are obtained in the form of a yellowish liquid.

¹ H NMR spectrum (400 MHz, CDCl ₃ ): δ (ppm) 7.59-7.06 (m, 5H), 5.74 (dd, 1H, J _HH = 17 Hz, J _HH = 1 Hz, CH = CH _A H _B ), 5.41 (dd, 1H, J _HH = 11 Hz, J _HH = 1 Hz, CH = CH _A H _B ).

Example 2. The synthesis of (2-diphenylphosphine) phenylphosphine chloride (2) is carried out in accordance with the modified method described in M.T. Reetz, A. Gosberg. New non-C ₂ -symmetric phosphine-phosphonites as ligands in asymmetric metal catalysis. Tetrahedron: Asymmetry, 1999, v. 10, p. 2129-2137.

Reactions are carried out in an inert atmosphere. Solvents are purified by distillation in an argon atmosphere: tetrahydrofuran is distilled over ketyl sodium benzophenone, toluene is distilled over sodium.

To a solution of 1 g (2.93 mmol) of 1-bromo-2-diphenylphosphinobenzene in 15 ml of absolute tetrahydrofuran at a temperature of minus 78 ° C, 1.83 ml of a 1.6 M solution of n-BuLi in hexane is slowly added. The reaction mixture was stirred for 2 hours at a temperature of minus 78 ° C, then a solution of 0.67 g (3.10 mmol) (PhP (Cl) NEt _{2 was} added slowly at this temperature. The mixture was allowed to warm to room temperature with stirring. The solvent was evaporated. 25 ml of dry toluene are added to the residue, 2.13 ml of a 4 M solution of HCl in diethyl ether are added to the resulting suspension, instant white precipitation of diethylammonium chloride is observed. The mixture is stirred for 18 hours under argon atmosphere. The pale yellow solution is filtered off from the precipitated precipitate as in a stream of argon, the solvent was evaporated, the residue (yellow oil) was dried in vacuum, yield 1.009 g (85 wt%).

³¹ P NMR spectrum { ¹ H} (161.98 MHz, CDCl ₃ ): δ (ppm) 73.4 (d, ³ J _PP = 282 Hz, P (Ph) Cl), -19.6 ( d, PPh ₂ ),

Example 3. Synthesis of [(2-diphenylphosphino) phenyl] [2- (vinyl) phenyl] phenylphosphine (3)

0.08 g (3.29 mmol) of magnesium is placed in a Schlenk flask (50 ml), calcined in a vacuum, and filled with argon. Add 40 ml of absolute tetrahydrofuran, a catalytic amount of iodine. A solution of 0.5 g (2.73 mmol) of 2-bromostyrene (1) in 20 ml of tetrahydrofuran is separately prepared, a few drops of the prepared solution are added to the reaction flask. The mixture is heated to a boil without stirring, the solution is gradually discolored, the remaining solution 1 is slowly added to the boiling mixture. The solution acquires a brownish-yellow color. The solution is refluxed with stirring for 4 hours. The mixture is cooled to room temperature. Additional tetrahydrofuran is added to dilute the resulting thick brown solution. The resulting Grignard reagent solution is filtered off under argon flow. The solution is cooled to a temperature of minus 30 ° C, a solution of 0.77 g (1.9 mmol) (2-diphenylphosphine) phenylphosphine chloride (2) in 10 ml of tetrahydrofuran is added dropwise to it. The temperature rises to minus 15 ° C. The cooling is removed, the reaction mixture is allowed to warm to room temperature, then the mixture is stirred at this temperature for one day. The solvent was evaporated, the reaction mixture was treated with a saturated aqueous solution of ammonium chloride (20 ml), 50 ml of methylene chloride was added, the organic layer was separated (the aqueous layer was extracted with CH ₂ Cl ₂ ), the combined organic phase was dried over sodium sulfate, and the solvent was evaporated. A pale yellow solid was dissolved in CH ₂ Cl ₂ , a small amount of n-hexane was added, and a white fine precipitate formed. The solution is filtered from the precipitate through a glass filter with a tube in a stream of argon, the solvent is evaporated, get 0.808 g (yield 90 wt%) of a pale yellow crystalline substance.

NMR ³¹ P { ¹ H} (161.98 MHz, CDCl ₃ ): δ (ppm) -13.6 (d, ³ J _PP = 160 Hz, P (C ₆ H ₄ CH = CH ₂ ) Ph ), -21.2 (d, ³ J _PP = 160 Hz, PPh ₂ ).

¹ H NMR (400 MHz, CDCl ₃ ): δ (ppm) 6.76-7.62 (m, 24H, C H = CH ₂ , Ar- H ), 5.54 (dt, 1H, J _HH = 17 Hz, CH = CH _A H _B ), 5.08 (dd, 1H, J _HH = 12 Hz, CH = CH _A H _B ).

Example 4. Synthesis of ([(2-diphenylphosphino) phenyl] [2- (vinyl) phenyl] phenyl phosphine-P, P) - (tetrahydrofuran) -trichlorochrom (III) (4)

To a solution of 0.59 g (1.27 mmol) of [(2-diphenylphosphino) phenyl] [2- (vinyl) phenyl] phenylphosphine (3) in 25 ml of absolute toluene, 0.43 g (1.15 mmol) of Cr ( THF) ₃ Cl ₃ . After 5 minutes of stirring, a gradual change in the color of the mixture from violet to bright blue is observed. The mixture was stirred at room temperature for 84 hours. The solvent was evaporated, and the residue was a violet-blue powder. 25 ml of methylene chloride are added, partial dissolution of the product is observed (dark blue solution), the violet precipitate is filtered off through a glass filter with a tube in a stream of argon. To the dark blue filtrate was added n-hexane and the product crystallized upon cooling. After recrystallization, 0.51 g (yield 64 wt%) of compound 4 (dark blue crystals) is obtained.

Example 5. Preparation of ([(2-diphenylphosphino) phenyl] [2- (vinyl) phenyl] phenylphosphine-P, P) - (aqua) trichlorochromium (III) (5)

Compound 5 in an amount of 0.156 g is formed by crystallization of 0.20 g of compound 4 in an atmosphere of air (yield 85 mass%).

The structure of compound 5 (hydrogen atoms are not shown).

The output and data of elemental analysis of compounds 4 and 5 are presented in table 1.

Table 1 Elemental analysis of compounds 4-5 Compound (yield, mass%) Gross formula MM Found, mass% Calculated, mass% C H P C H P 4 (64) C ₃₆ H ₃₄ P ₂ CrCl ₃ O 702.44 61.38 4.98 8.51 61.50 5.12 8.83 5 (85) C ₃₂ H ₂₈ P ₂ CrCl ₃ O 648.44 59.09 4.21 9.66 59.22 4.32 9.56

Conducting the trimerization of ethylene to 1-hexene using a catalytic trimerization complex of 4 or 5 is presented below.

Example 6

The preparation of catalytic solutions is carried out in a Schlenk vessel in an inert atmosphere of argon. A portion of compound 4 (0.55 mg) is loaded under a stream of argon, 25 ml of absolute methylcyclohexane are added. The catalytic solution was stirred for 15 minutes at room temperature. Then, 0.6 ml of a 10% solution of methylaluminoxane in toluene is added to it, after which it is stirred for another 5 minutes and introduced into the autoclave in a stream of argon. After loading the obtained catalyst system into the autoclave, the ethylene feed is switched on and is not interrupted during the entire process. The temperature and pressure in the autoclave are kept constant (temperature 87 ° C, pressure 40 bar). After the reaction time (30 min), the ethylene supply is shut off, heating and stirring are turned off. After cooling and depressurization, methanol is introduced into the autoclave to decompose the catalyst system and an internal standard (n-decane; 0.2-0.8 g) is added and the mixture is stirred for 10 minutes. After opening the autoclave, 10 ml of a 20% HCl solution and 5 ml of toluene are added to the reaction mass.

Example 7

The example is similar to example 6, but the process is carried out at a temperature of 75 ° C.

Example 8

The example is similar to example 6, but 0.19 mg of compound 4 is taken.

Example 9

The example is similar to example 8, but the process is carried out at a temperature of 75 ° C.

Example 10

The example is similar to example 6, but 0.07 mg of compound 4 is taken and the process is carried out at a temperature of 60 ° C.

Example 11

The example is similar to example 10, but 0.09 mg of compound 5 is taken.

The results obtained in examples 7-11 are shown in table 2.

Claims (1)

A catalytic complex for the selective trimerization of ethylene into 1-hexene, comprising a chromium (III) compound with a diphosphine ligand of the general formula [CrCl ₃ ((Ph ₂ P (1,2-С ₆ Н ₄ ) Р (Ph) (1,2-С ₆ H ₄ ) CH = CH ₂ ) _- (L)], where L is tetrahydrofuran or water, the source of chromium (III) is Tris (tetrahydrofuran) chromium chloride, the activator is methylaluminoxane solution, and the components of the complex are in the following molar ratio: compounds chromium: activator = 0.02-0.12%: 99.88-99.98%.