RU2717241C1 - Method for oligomerization of ethylene in organic solvent medium in presence of chromium catalyst and organoaluminium activator - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to industrial production of hexene-1 and octene-1 by oligomerization of ethylene and can be used in petrochemical industry and in organic synthesis. Disclosed is a method of producing hexene-1 and octene-1. Oligomerization of ethylene is carried out at moderately high temperatures (30–60 °C) and pressure (2–5 mPa) in the presence of a catalyst prepared from mixtures of a chromium (III) salt and conformationally rigid chelate diphosphonic ligands, activated with malealuminoxane, wherein the ligands used are compounds of a novel structural type based on 5,6-dihydrodibenzo [c,e][1,2] azaphosphinine of general formula:

,

where R¹ is an alkyl or aryl substitute, and R² is an ortho-substituted phenyl moiety. Reaction products are separated by rectification at atmospheric pressure. Ligand used is preferably diphosphine ligands containing a tert-butyl substitute or an ortho-methoxyphenyl substitute R¹ and ortho-methoxyphenyl substitutes R².

EFFECT: technical result is obtaining mixtures of hexene-1 and octene-1 in ratio from 2:1 to 1:2 with formation of by-products in amount of not more than 10 %, with content of non-distillate by-products C6+C8 less than 1 %, when using a catalyst system in small amounts at moderate reaction time.

6 cl, 1 tbl, 19 ex

Description

The invention relates to the field of industrial production of industrially important petrochemical products, hexene-1 and octene-1 by oligomerization of ethylene.

Hexene-1 and octene-1 are used in large-scale production of polyolefins, in particular linear low-pressure polyethylene, polyolefin anti-turbulent additives, lubricants and other products of organic synthesis.

From the current level of technology known methods for producing hexene-1 and octene-1 using oligomerization of ethylene. Non-selective methods of ethylene oligomerization make it possible to obtain mixtures of alpha-olefins with a total content of 1-hexene and 1-octene up to 50% (Angew. Chem. Int. Ed., 2013, 52, 12492-12496).

Advanced methods for the synthesis of hexene-1 and octene-1 are based on selective methods for the oligomerization of ethylene. A method for producing hexene-1 using a catalytic system based on chromium (III) salts, substituted pyrrole and an organoaluminum activator is used in industry; the maximum productivity is achieved for a catalyst prepared from chromium (III) 2-ethylhexanoate, 2,5-dimethylpyrrole and Et ₂ AlCl and AlEt ₃ as cocatalysts (patent US 5563312 (A), C07C 2/24, publ. 08/10/1996; patent EP 0780353 (A1), C07C 2/30, publ. 06/25/1997; patent US 5856257 (A) , B01J 31/00, publ. 01/05/1999). The disadvantages of this method are the low productivity of the catalyst (up to 30 kg / g (Cr) ⋅h), harsh reaction conditions (115 ° C and 100 atm), and the fact that only hexene-1 s can be obtained using this method selectivity up to 93%.

To date, a number of methods have been developed to obtain hexene-1 under mild reaction conditions in the presence of high-performance catalysts based on transition metal complexes. A method is described for the selective trimerization of ethylene in the presence of titanium (IV) pre-bitch complexes activated with methylaluminoxane (MAO) (US Pat. No. 7,056,995 (B2), C08F 4/76, C08F 4/52, C08F 4/64, C08F 4/642, publ. 06.06. .2006). Using these catalysts, even at 30 ° C, a productivity of up to 40 kg / g (Ti) ⋅h is achieved. The disadvantages of the method are the formation of polyethylene (1% or more), the rapid deactivation of the catalyst and the need to use significant (up to 1000 equivalents) quantities of an expensive MAO activator. Among Ti-based catalysts, a high (up to 300 kg / g (Ti) ⋅h) productivity with up to 92% hexene-1 selectivity was demonstrated by the phenoxy-imine complex with an adamantyl substituent in the ortho position of the phenoxy-imine ligand (Organometallics, 2010, 29, 2394-2396), however, this catalyst is thermally unstable and synthetically little available.

Significantly more effective are methods using high-performance chromium catalysts based on diphosphine ligands. A known method for the selective oligomerization of ethylene in the presence of a chromium catalyst based on a ligand (2-MeOS ₆ H ₄ ) ₂ P-NMe-P (2-MeOS ₆ H ₄ ) ₂ (patent WO 0204119 (A1), B01J 31/18, publ. 01/17/2002). At pressures of 10–20 atm and a temperature of 50–100 ° C, productivity values of up to 130 kg / g (Cr) ⋅ h with a yield of hexene-1 up to 89% were achieved. The main byproduct is isomeric C10 hydrocarbons.

A known method of trimerization of ethylene with the formation of hexene-1, which does not require the use of an expensive activator MAO. It is based on the use of the chromium complex of the diphosphine ligand Ph ₂ PN ⁱ Pr-PPh-NH ⁱ Pr activated by triethyl aluminum (Patent WO 2009006979 (A2), B01J 31/14, B01J 31/18, C07C 2/36, C07F 9/46, published on January 15, 2009). The maximum productivity of this catalyst at 50 ° C and 30 atm was 40 kg / g (Cr) ⋅ h. In addition to low productivity, the use of this catalytic system noted the formation of significant quantities of butene-1 and C10 hydrocarbons. The main disadvantage of the catalyst is the high cost of the ligand, due to the complexity of its synthesis.

Considering that octene-1 is also a highly demanded monomer and raw material, the urgent task is to obtain octene-1 or mixtures of octene-1 / hexene-1 by selective ethylene oligomerization.

To solve this problem, a method has been developed for the selective tetmerization of ethylene with predominant formation of octene-1, using a chromium catalyst based on the Ph ₂ PN ( ⁱ Pr) -Ph ₂ ligand (patent WO 2004056479 (A1), B01J 31/18, published January 17, 2002 ) For this catalyst, production rates of up to 110 kg / g (Cr) ⋅h were achieved with a yield of hexene-1 up to 25% and octene-1 up to 75% (the total yield of hexene-1 and octene-1 does not exceed 90%, the ratio of products depends on reaction conditions). The disadvantage of this catalytic system is the formation of significant quantities of isomeric hydrocarbons C6 and polyethylene, as well as low thermal stability of the catalyst.

Also described is a method for producing a mixture of hexene-1 and octene-1 using a catalyst based on the complex [Ph ₂ P-СНМеСНМ-PPh ₂ ] CrCl ₃ (Organometallics, 2010, 29, 5805-5811), in which for a mixture of octene-1 and hexene-1 in a ratio of 2: 1 for a pressure of 30 atm, a productivity of 500 kg / g (Cr) ⋅ h was achieved. The disadvantage of this catalytic system is the formation of significant quantities - up to 6% - of C6 by-products, and up to 1% of polyethylene.

A known method of obtaining a mixture of hexene-1 and octene-1 using a chromium catalyst based on the ligand Ph ₂ P-CH = CH ^t Bu-PPh ₂ (ACS Catal., 2013, 3, 2311-2317). For this catalyst at 40 atm and a temperature of 40 ° C, a productivity of ~ 600 kg / g (Cr) ⋅h was achieved. The disadvantages of this catalytic system are the formation of significant quantities - up to 8% - of C6 by-products, as well as the need to use significant (more than 500 equivalent) amounts of activator, MAO.

A known method of obtaining a mixture of hexene-1 and octene-1 using a chromium catalyst based on a diphosphine ligand (2-FC ₆ H ₄ ) ₂ PN ⁱ Pr-PPh ₂ (patent US 7906681 (B2), C07F 9/02, B01J 27 / 188, B01J 27/00, B01J 31/00, C07C 2/02, published March 15, 2011). Using this catalyst, a productivity of 200 kg / g (Cr) ⋅h was achieved, mixtures of octene-1 and hexene-1 were formed in a ratio of 2: 1 (mass.). The disadvantages of this technical solution are the need to use 500 equiv. and more activator MAO, as well as high pressures (40 atm) and temperature (70 ° C). The content of by-products C6 + C8 3-4%.

Closest to the claimed technical solution is the solution reflected in patent WO 2008077908 (A1), C07F 9/6571, C07F 11/00, B01J 31/18, publ. 07/03/2009. Ethylene oligomerization is carried out in the presence of a chromium catalyst based on a diphosphine ligand (1,2-C ₆ H ₄ O ₂ ) P-NMe-PPh ₂ . For this catalyst, a productivity of 170 kg / g (Cr) ⋅ h was achieved, a 2: 1 yield of a mixture of hexene-1 and octene-1 was about 88%, and the content of by-products C6 + C8 was less than 2%.

A common drawback of the known high-performance catalysts and methods for ethylene oligomerization using them to form mixtures of hexene-1 and octene-1 is the formation of significant amounts of by-products, cyclic and isomeric unsaturated hydrocarbons C6 and C8, which cannot be separated from the target products by distillation. The most probable reason for the formation of such by-products is the conformational mobility of the diphosphine ligand, which facilitates the formation of catalytic centers of side processes, since all known examples of catalysts are described by the general formula R ₂ PZ-PR ' ₂ , where Z is a bridging group linking phosphorus atoms.

The problem to which the claimed invention is directed is to develop a method for the oligomerization of ethylene with the formation of hexene-1 and octene-1 in the presence of minimal amounts of organoaluminum activator and with the formation of mixtures of hexene-1 and octene-1 in high yield (90% or more), with a capacity of ~ 100 kg / g (Cr) ⋅h, and the content of by-products C6 and C8 in amounts of less than 2%.

This problem is solved in that a catalyst uses a mixture of a chromium (III) salt, preferably Cr (III) acetylacetonate, with diphosphine ligands of a new structural class, which differs from the known ligands by the presence of a structurally rigid polycyclic fragment including phosphorus and nitrogen atoms, and activated organoaluminum compounds, methylaluminoxane and trimethylaluminum.

It is preferable to use the 5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine derivative (1) as a ligand for the synthesis of the catalyst, where R ₁ is an alkyl or aryl substituent, and R ² is an aryl substituent. The structure of this ligand makes it easy to synthesize it based on the available starting 2-phenylaniline compound, the ability to vary substituents at phosphorus atoms, and also provides high performance catalyst based on it.

It is preferable to introduce methoxy groups into the structure of the diphosphine ligand in the ortho positions of phenyl substituents at the phosphorus atoms, since this increases the productivity of the catalyst and reduces the formation of by-products of ethylene polymerization.

The technical result provided by the given set of features is to achieve a high yield of mixtures of hexene-1 and octene-1 (more than 90%) with a capacity of more than 100 kg / g (Cr) ⋅ h, with the formation of easily separated by-products in an amount of not more than 10% with the content of isomeric hydrocarbons C6 + C8 in amounts of less than 2%, when carrying out the process at moderate temperatures (up to 60 ° C) and ethylene pressures (up to 50 atm) at a moderate reaction time (2-4 hours).

Thus, a method for producing mixtures of hexene-1 and octene-1 using a oligomerization catalyst based on diphosphine ligands of a new structural type has been developed.

Obtaining hexene-1 and octene-1 is carried out according to reaction (2):

In order to obtain mixtures of hexene-1 and octene-1 by oligomerization of ethylene and to achieve high catalyst productivity under mild reaction conditions, a new diphosphine ligand formula is proposed in which the phosphorus, nitrogen atoms and one of the aromatic substituents on the phosphorus atom are fragments of a conformationally rigid polycyclic system. Compounds of the general formula (1), where R ₁ is an alkyl or aryl substituent and R ² is an aryl substituent, are proposed as similar diphosphine ligands.

The starting compound for the synthesis of diphosphine ligands of the general formula (1) is 6-chloro-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine, available by reaction of 2-phenylaniline with phosphorus (III) chloride, the ligands are synthesized in two stages by sequential interaction with an organometallic compound and diarylchlorophosphine (3):

The two-stage synthesis allows you to vary the substituents on the phosphorus atoms of the ligand, as illustrated by examples 1-2.

The catalyst is prepared by mixing a solution of a chromium (III) salt, preferably Cr (acac) ₃ acetylacetonate, and a diphosphine ligand in inert organic solvents, followed by treatment with organoaluminum activators trimethylaluminum and methylaluminoxane. The ligand forms a complex compound with a chromium salt, the reaction of which with organoaluminum activators leads to the formation of a catalyst solution. The process proceeds at room temperature for 2-5 minutes.

The resulting catalyst solution is introduced into a reactor containing an organic solvent and a small amount of a molecular oxygen acceptor and trace elements. Trimethylaluminum is used as an acceptor. The temperature in the reactor is raised to a predetermined temperature, and ethylene is introduced under pressure. Ethylene pressure is kept constant. At the same time, the oligomerization process begins immediately, accompanied by a slight thermal effect. The reaction is monitored using an ethylene flow sensor, the composition of the products is determined by GLC and NMR spectroscopy. At a temperature of 60 ° C and a pressure of 20 atm and the use of catalysts based on ligands 1 and 2 (formulas are shown in Scheme 3), productivity is reached up to 100 kg / g (Cr) ⋅h with the formation of mixtures of hexene-1 and octene-1 containing no more than 10% of by-products, when using a catalyst based on ligand 2 by distillation at atmospheric pressure, it is possible to obtain a mixture of C6 + C8 hydrocarbons containing practically pure hexene-1 and octene-1 (total impurity content of less than 0.3%).

The achievement of the technical result is confirmed by examples.

The synthesis of 6-chloro-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinin was performed according to the described procedure (GM Campbell I, JK Way, J. Chem. Soc. 1960, 5034. MJS Dewar, WP Kubba, J Am. Chem. Soc. 1960, 82, 5685). The synthesis of diphosphine ligands 1–3 was carried out in an argon atmosphere starting from 6-chloro-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine using commercially available reagents in accordance with Scheme (3). The synthesis methods are given in examples 1-3.

Example 1. The synthesis of ligand 1.

6- (tert-butyl) -5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine.

6-Tert-butyl-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine. A suspension of 6-chloro-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinin (4.67 g, 20 mmol) in ether (20 ml) was added at -20 ° C to a solution of tert-butyllithium in pentane (28 ml 1.6 M solution, 45 mmol). The mixture was stirred for 2 hours at −20 ° C., 12 hours at room temperature and poured into a mixture of a solution of 5% NH ₄ Cl with ice (100 ml) and CH ₂ Cl ₂ (100 ml). The organic layer was separated, the aqueous layer was extracted with CH ₂ Cl ₂ (2 × 20 ml). The combined organic fractions were dried over Na ₂ SO ₄ and evaporated under reduced pressure. The residue was purified using flash chromatography (silica gel 60-200 μm, 1: 1 mixture of Et ₂ O-CH ₂ Cl ₂ ). Yield 3.73 g, (73%), colorless solid. Calculated: C ₁₆ H ₁₈ NP: C, 75.27; H, 7.11; N, 5.49. Found: C, 75.33; H, 7.07; N, 5.55. ¹ H NMR (CDCl ₃ , 20 ° C) δ: 7.94 (d, 1H); 7.82 (d, 1H); 7.48 (m, 2H); 7.33 (t, 1H); 7.16 (t, 1H); 6.92 (t, 1H); 6.79 (d, 1H); 4.48 (broad d, 1H); 0.83 (d, 9H). ³¹ P NMR (CDCl ₃ , 20 ° C) δ: 28.2.

5- (bis (2-methoxyphenyl) phosphino) -6- (tert-butyl) -5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine (ligand 1). Et ₃ N (0.55 ml, 3.9 mmol) and then (o-MeOS ₆ H ₄ ) ₂ PCl (1.12 ml, 4.0 mmol) were added to the stirred suspension of 6-tert-butyl-5,6-dihydrodibenzo [s, e] [ 1,2] azaphosphinin (0.92 g, 3.6 mmol) in acetonitrile (30 ml). After 12 hours of stirring, the solvents were removed under reduced pressure, the residue was recrystallized from ethanol. Yield 1.08 g (60%), colorless crystals. Calculated: C ₃₀ H ₃₁ NO ₂ P ₂ : C, 72.13; H, 6.26; N, 2.80; Oh, 6.41. Found: C, 72.21; H, 6.31; N, 2.78; Oh, 6.48. ¹ H NMR (CDCl ₃ , 20 ° C) δ: 7.98 (d, 1H); 7.93 (d, 1H); 7.72 (d, 1H); 7.56 (d, 1H); 7.52 (t, 1H); 7.39 (t, 1H); 7.33 (t, 1H); 7.25 (t, 1H); 7.21 (t, 1H); 7.11 (m, 1H); 7.05 (t, 1H); 6.85 (t, 1H); 6.83 (t, 1H); 6.71 (m, 1H); 6.66 (t, 1H); 3.83 (s, 3H); 3.52 (s, 3H); 0.46 (d, 9H). ³¹ P NMR (CDCl ₃ , 20 ° C) δ: 57.8 (br.s.); 36.5 (broad).

Example 2. Synthesis of ligand 2.

6-Phenyl-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine. A suspension of 6-chloro-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinin (8.41 g, 36 mmol) in THF (50 ml) was added at 0 ° C to a Grignard reagent solution obtained from PhBr (16.8 g , 100 mmol) and Mg (2.43 g, 100 mmol) in Et ₂ O (80 ml). The mixture was stirred for 12 hours, boiled for 2 hours, cooled and poured into a mixture of ice water (100 ml) and CH ₂ Cl ₂ (100 ml). Then 5% HCl was added until a clear biphasic mixture formed. The organic layer was separated, the aqueous layer was extracted with CH ₂ Cl ₂ (2 × 20 ml). The combined organic fractions were dried over Na ₂ SO ₄ and evaporated under reduced pressure. The residue was recrystallized from a mixture of Et ₂ O-CH ₂ Cl ₂ (1: 1). Yield 5.25 g, (53%), colorless crystals. Calculated: C ₁₈ H ₁₄ NP: C, 78.53; H, 5.13; N, 5.09. Found: C, 78.66; H, 5.10; N, 5.10. ¹ H NMR (CDCl ₃ , 20 ° C) δ: 7.95 (d, 1H); 7.81 (d, 1H); 7.72 (m, 1H); 7.53 (t, 1H); 7.41 (t, 1H); 7.18-7.12 (m, 5H); 6.93 (t, 1H); 6.84 (d, 1H); 4.81 (broad d, 1H). ³¹ P NMR (CDCl ₃ , 20 ° C) δ: 6.26.

5- (Bis (2-methoxyphenyl) phosphino) -6-phenyl-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine (ligand 2). The procedure is similar to that described in example 1. Yield 1.22 g (64%), colorless crystals. Calculated: C ₃₂ H ₂₇ NO ₂ P ₂ : C, 73.98; H, 5.24; N, 2.70; Oh, 6.16. Found: C, 74.09; H, 5.28; N, 2.66; Oh, 6.20. ¹ H NMR (CDCl ₃ , 20 ° C) δ: 7.95 (d, 1H); 7.77 (br. D, 1H); 7.74 (d, 1H); 7.59-7.53 (m, 2H); 7.41-7.32 (m, 3H); 7.28 (t, 1H); 7.20 (t, 1H); 7.04-6.93 (m, 6H); 6.85 (t, 3H); 6.78 (t, 1H); 6.72 (m, 1H); 3.65 (s, 3H); 3.40 (s, 3H). ³¹ P NMR (CDCl ₃ , 20 ° C) δ: 54.27 (d); 16.35 (d).

Example 3. The synthesis of ligand 3.

6- (2-Methoxyphenyl) -5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine. A suspension of 6-chloro-5,6-dihydrodibenzo [c, e] [1,2] azaphosphinin (10.0 g, 43 mmol) in THF (60 ml) was added at 0 ° C to a Grignard reagent solution obtained from 2-bromoanisole ( 18.7 g, 100 mmol) and Mg (2.43 g, 100 mmol) in Et ₂ O (80 ml). The product was isolated as described in Example 2. Yield 7.35 g, (56%), colorless crystals. Calculated: C ₁₉ H ₁₆ NOP: C, 74.74; H, 5.28; N, 4.59; Oh, 5.24. Found: C, 74.86; H, 5.32; N, 4.61; Oh, 5.20. ¹ H NMR (CDCl ₃ , 20 ° C) δ: 7.92 (d, 1H); 7.78 (d, 1H); 7.74 (m, 1H); 7.55 (t, 1H); 7.40 (t, 1H); 7.12 (m, 2H); 6.90 (t, 1H); 6.81 (d, 1H); 6.73 (m, 1H); 6.62 (t, 1H); 6.58 (m, 1H); 4.72 (broad d, 1H); 3.87 (s, 3H). ³¹ P NMR (CDCl ₃ , 20 ° C) δ: 0.30.

5- (Bis (2-methoxyphenyl) phosphino) -6- (2-methoxyphenyl) -5,6-dihydrodibenzo- [c, e] [1,2] azaphosphinine (ligand 3). The procedure is similar to that described in example 1. Yield 1.44 g (73%), colorless crystals. Calculated: C ₃₃ H ₂₉ NO ₃ P ₂ : C, 72.13; H, 5.32; N, 2.55; Oh, 8.73. Found: C, 72.22; H, 5.36; N, 2.50; Oh, 8.78. ¹ H NMR (CDCl ₃ , 20 ° C) δ: 7.80 (d, 1H); 7.74 (br. D, 1H); 7.69 (d, 1H); 7.55 (m, 1H); 7.41 (m, 2H); 7.31-7.22 (m, 4H); 7.01 (t, 4H); 6.87 (t, 1H); 6.78 (m, 2H); 6.63-6.55 (m, 3H); 3.64 (s, 3H); 3.54 (s, 3H); 3.20 (s, 3H). ³¹ P NMR (CDCl ₃ , 20 ° C) δ: 54.20 (d); 10.85 (d).

Ethylene oligomerization was carried out in a 1 liter steel reactor equipped with temperature and pressure sensors, as well as catalyst and ethylene injection systems with a volumetric flowmeter of the gaseous monomer. Compounds 4 (US 7141633 (B2), C08F 4/69, B01J 31/34, publ. 11/28/2006), 5 (patent US 7511183 (B2), С07С 2/08, С07С were selected as ligands for the preparation of comparison catalysts 2/32, C07C 2/36, B01J 31/18, B01J 31/24, published March 31, 2009), 6 (US patent 7906681 (B2), C07F 9/02, B01J 27/188, B01J 27/00, B01J 31/00, C07C 2/02, published March 15, 2011), 7 (ACS Catal., 2013, 3, 2311-2317), 8 (patent US 7803886 (B2), C08F 4/22, C09F 9/535 , B01J 31/02, published September 28, 2010), since these catalysts, according to data published in the scientific periodicals and in the patent literature, demonstrate the best performance in ethylene oligomerization. The structural formulas of ligands 4-8 are shown in scheme (4):

Example 4. Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 1 and chromium (III) acetylacetonate. To a solution of Cr (acac) ₃ (30 μmol) in 3 ml of toluene was added 40 μmol of ligand 1 in 4 ml of toluene, 5 ml of a 1.54 M solution of MMAO-12 (Al _MAO / Cr = 250), and after 5 minutes, 1 ml of 2 M TMA in toluene. Was stirred at room temperature and after 1 min was introduced into the reactor. Before that, 100 ml of heptane and 1 ml of 2 M TMA in toluene were placed in the reactor, the temperature was raised to 50 ° C, and the ethylene pressure was up to 20 atm. The progress of the reaction was monitored using a volumetric flow sensor. After 2 hours, 152.7 L of ethylene was absorbed. Then, the ethylene pressure was gradually reduced to atmospheric, the reactor was cooled, the resulting mixture was analyzed by GLC. 2 ml of water and 1 ml of methanol were added to the mixture, the organic phase was separated by filtration, 5% HCl was added to the residue, and the residue of polyethylene was filtered, dried and weighed. The organic phase was distilled at atmospheric pressure, taking a fraction with so on. in the range of 55-130 ° C. Received 188 g of a colorless liquid containing 21.7% hexene-1, 41.0% octene-1, 0.8% C6 hydrocarbons (methylcyclopentane, hexene-2), 0.4% C8 hydrocarbons, 26.9% n-heptane and 3.9% toluene. Reduced to the consumption of ethylene, data on the composition of the reaction products are presented in table 1.

Example 5. Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 2 and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that ligand 2 was used instead of ligand 1.

Example 6. Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 3 and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions are repeated as described in Example 4, except that ligand 3 was used instead of ligand 1.

Example 7. Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 3 and chromium (III) acetylacetonate under increased pressure. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that ligand 3 was used instead of ligand 1, and the ethylene pressure during the reaction was maintained at 30 atm.

Example 8 (comparative). Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 4 (US 7141633 (B2), C08F 4/69, B01J 31/34, publ. 28.11.2006) and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that ligand 4 was used instead of ligand 1.

Example 9 (comparative). Oligomerization of ethylene in n-heptane in the presence of a ligand-based catalyst 5 (US Pat. No. 7,511,183 (B2), C07C 2/08, C07C 2/32, C07C 2/36, B01J 31/18, B01J 31/24, publ. 31.03 .2009) and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that ligand 5 was used instead of ligand 1.

Example 10 (comparative). Oligomerization of ethylene in n-heptane medium in the presence of a ligand-based catalyst 6 (US patent 7906681 (B2), C07F 9/02, B01J 27/188, B01J 27/00, B01J 31/00, C07C 2/02, publ. 15.03 .2011) and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that ligand 6 was used instead of ligand 1.

Example 11 (comparative). Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 7 (ACS Catal., 2013, 3, 2311-2317) and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that ligand 7 was used instead of ligand 1.

Example 12 (comparative). Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 8 (ACS Catal., 2013, 3, 2311-2317) and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that ligand 7 was used instead of ligand 1.

Example 13. Oligomerization of ethylene in chlorobenzene in the presence of a catalyst based on ligand 1 and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 4, except that chlorobenzene was used as a solvent instead of n-heptane.

Example 14. Oligomerization of ethylene in chlorobenzene in the presence of a catalyst based on ligand 2 and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 5, except that chlorobenzene was used as a solvent instead of n-heptane.

Example 15. Oligomerization of ethylene in chlorobenzene in the presence of a catalyst based on ligand 3 and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 6, except that chlorobenzene was used as a solvent instead of n-heptane.

Example 16 (comparative). Oligomerization of ethylene in chlorobenzene in the presence of a catalyst based on ligand 4 and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 8, except that chlorobenzene was used as a solvent instead of n-heptane.

Example 17 (comparative). Oligomerization of ethylene in chlorobenzene in the presence of a catalyst based on ligand 5 and chromium (III) acetylacetonate. The amounts of reagents and experimental conditions were repeated as described in Example 9, except that chlorobenzene was used as a solvent instead of n-heptane.

Example 18 (comparative). Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 3 and chromium (III) chloride. The amounts of reagents and experimental conditions were repeated as described in Example 6, except that instead of Cr (acac) ₃ , a complex of CrCl ₃ (THF) ₃ composition was used as the chromium salt.

Example 19 (comparative). Oligomerization of ethylene in n-heptane in the presence of a catalyst based on ligand 3 and chromium (III) 2-ethylhexanoate. The amounts of reagents and experimental conditions were repeated as described in Example 6, except that instead of Cr (acac) ₃ , 2-ethylhexanoate, a complex of Cr (n-BuCHEtCOO) ₃ composition, was used as the chromium salt.

The results show that in the process of obtaining hexene-1 and octene-1 by oligomerization of ethylene in the presence of chromium catalysts based on diphosphine ligands:

- the use of catalysts based on ligands containing a structural fragment of 5,6-dihydrodibenzo [s, e] [1,2] azaphosphinine allows to obtain mixtures of hexene-1 and octene-1 containing a small amount of decene-1;

- the use of catalysts based on ligands containing a structural fragment of 5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine and a methoxy group in the ortho position of phenyl substituents at phosphorus atoms, surpass the catalysts in productivity and yield of alpha-olefins by the basis of diphosphine ligands of the traditional "open" structure;

- the use of ligand-based catalysts containing a structural fragment of 5,6-dihydrodibenzo [c, e] [1,2] azaphosphinine and a methoxy group in the ortho position of phenyl substituents on phosphorus atoms, allows to obtain mixtures of hexene-1 and octene-1 with a total ethylene yield of 90% or more with a mass ratio of products from 2: 1 to 1: 2, and containing impurities not separated by distillation of isomeric hydrocarbons C6 + C8 in amounts of not more than 2%.

Thus, the proposed technical solution allows you to develop an effective method for producing hexene-1 and octene-1, not inferior to the known analogues in terms of productivity and yield. Due to the low content of C6 + C8 isomeric hydrocarbons in the by-products of the reaction catalyzed by complexes based on new diphosphine ligands, hexene-1 and octene-1 can be separated by distillation under normal pressure.

Claims (8)

1. The method of oligomerization of ethylene in an organic solvent in the presence of a chromium catalyst and an organoaluminum activator - methylaluminoxane, with heating and pressure, characterized in that the catalyst is a product of the interaction of a chromium (III) salt with a conformationally hard chelate diphosphine ligand and an organoaluminum activator - matilaluminoxane , and a 5,6-dihydrodibenzo [c, e] [1,2] azaphosphinin derivative of the general formula is used as a ligand:

where R ¹ is an alkyl or aryl substituent, and R ₂ is an ortho-substituted phenyl moiety. 2. The method according to p. 1, characterized in that the chromium (III) salt used is chromium (III) acetylacetonate. 3. The method of claim 1, wherein the diphosphine ligands of claim 1 are used, comprising a tert-butyl substituent or ortho-methoxyphenyl substituent R ¹ and ortho-methoxyphenyl substituents R ² . 4. The method according to p. 1, characterized in that the oligomerization is carried out at a temperature of from 20 to 100 ° C, preferably from 40 to 80 ° C. 5. The method according to p. 1, characterized in that the oligomerization is carried out at a pressure of from 0.1 to 10 MPa, preferably from 2 to 6 MPa. 6. The method according to p. 1, characterized in that the oligomerization is carried out at a catalyst / activator ratio of 0.02-1 mol. %, preferably 0.2-0.5 mol. %