RU2752516C1 - Method for synthesising dialkyl 2,3-diisobutyl succinate - component of titanium-magnesium catalysts for olefin polymerisation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for synthesising dialkyl 2,3-di-isobutyl succinates by the formula 1 from succinic acid diester, including the stages of double condensation of isobutyl aldehyde with succinic acid diester in an aprotic solvent or in an anhydrous protic solvent, preferably DMF; 1 to 1.3 equivalent of a metal hydride by the formula MeH_n or a metal alkoxide (RO)_nMe wherein Me is a metal of the first or second group of the periodic system, n is the valence of the metal, R is the residue of the C1-C4 alcohol group, is used as a base, the reaction is executed while heating in the temperature range of 40 to 100°C for 3 to 5 hours resulting in a mixture of mono- and bis-ethylidene compounds, with intermediate esterification, followed by the stage of hydrogenation of the mixture of dienes.

EFFECT: development of a new method for synthesising dialkyl 2,3-di-isobutyl succinates with good yield and high purity; compounds obtained by this method can be used as stereo regulating components in a composition of supported titanium-magnesium catalysts for producing polypropylene.

5 cl, 6 dwg, 1 tbl, 9 ex

Description

Electron donor compounds are one of the key components of titanium-magnesium catalysts for polypropylene production. The use of these compounds in the composition of the catalyst as internal donors makes it possible to radically increase its stereospecificity and, as a consequence, the stereoregularity of the obtained polymer. At the same time, the composition of the donor affects the molecular weight distribution (MWD) of polypropylene, which determines the method of processing and further use of the polymer. Thus, to obtain products by injection molding, polypropylene with a narrow molecular weight distribution is required, while polypropylene with a wide MWD is used to obtain film and pipe grades. One of the first classes of electron-donor compounds, the introduction of which into the composition of a titanium-magnesium catalyst made it possible to obtain highly stereoregular polypropylene with a wide MWD, were 2,3-disubstituted succinic acid esters - succinates (WO 2000063261). The high efficiency of using succinates as internal donors makes it possible to isolate catalysts containing these compounds into a separate, sixth generation of catalysts for propylene polymerization (Adv Polym Sci, 2013, 257, 81; ACS Catal. 2017, 7, 4509).

Promising internal donors are diesters of 2,3-diisobutyl succinate, in particular diethyl 2,3-diisobutyl succinate (compound 1) (WO 2000063261; WO 2013029767). Compound 1 possesses two stereocenters and can exist as four stereoisomers 1а-1d (Fig. 1. Compounds 1а and 1c, as well as 1b and 1d in pairs are mirror isomers; therefore, when analyzed under achiral conditions, only two forms of compound 1 are observed: anti- (or erythro-), conventionally displayed by formula 1a, and syn- (or threo-), conventionally displayed by formula 1b.

Several methods of obtaining compound 1 are described in the literature. The work (J. Org. Chem., 1998, 63, 7130) describes the preparation of succinate 1 as a result of a multistep process involving the interaction of isocaproic acid ethyl ester with lithium diisopropylamide at -78 ° C, one-electron oxidation of the obtained anion by the action of ferrocene hexafluorophosphate, and the interaction of the resulting radical with TEMPO (Fig. 2). The total yield of anti- and syn- forms of compound 1 did not exceed 23%. CN 103145553 claims a similar method for the preparation of compound 1, based on the reaction of isocaproic acid ethyl ester with lithium diisopropylamide at -78 ° C, followed by dimerization under the action of TiCl ₄ with a yield of 84%.

In [Can.J. Chem., 1980, vol. 58, p. 1101-1105] provides another variant of obtaining compound 1. According to this method, the reaction of dimethyl fumaric acid with an isobutyl radical generated during the anodic oxidation of the sodium salt of isovaleric acid, a mixture of isomers of compound 1 was obtained with a yield of 37% (Fig. 3).

These methods for the synthesis of compound 1 have significant disadvantages, such as the use of highly hazardous expensive reagents (butyllithium, lithium diisopropylamide, ferrocene hexafluorophosphate), require the use of deep cooling and an inert atmosphere or complex equipment required for electrolysis, and, as a rule, lead to compound 1 with a low exit.

The closest to our proposed method of obtaining compound 1, the prototype, is a multistage synthesis of compound 1, including alkylation of malonic ester with haloacetate followed by two sequential alkylations with haloalkyls, hydrolysis, decarboxylation and esterification (Fig. 4) (WO 2013029767). This option uses inexpensive available reagents and does not require the use of complex equipment.

However, reproduction of the technique proposed in WO 2013029767 showed that only the first two stages of the process are reproduced, while the third stage leads to the formation of a mixture of the starting isobutyltriester and its isobutyl ether (Fig. 5) in a close ratio instead of the target compound 1 (see Example 1), which is obviously due to the reduced CH acidity of the reaction center in isobutyltriester. There is also no independent description of the successful use of this sequence for the synthesis of compound 1 in the literature. Consequently, this sequence of reactions either does not allow obtaining the claimed product 1, or has a low reproducibility, which makes it inapplicable for practical use.

It is an object of the present invention to provide a method for producing disubstituted succinate 1 with a purity of more than 95%, without significant admixture of monosubstituted 2-isobutyl succinate 2, which reduces the stereoregulating ability of an olefin polymerization catalyst. The general scheme of our proposed method for producing 2,3-diisobutyl succinate diester is shown in Fig. 6. The process of obtaining the diester of 2,3-diisobutyl succinate consists in the double condensation of isobutyl aldehyde with the corresponding diester of succinic acid to form a mixture of mono- and bis-ethylidene compounds 3 and 4 and their subsequent hydrogenation leading to 2,3-diisobutyl succinate 1 ...

In the first stage, the diester of succinic acid (for example, diethyl succinate) is reacted with isobutyl aldehyde taken in an excess of 0-30% in an aprotic solvent such as toluene, ethylbenzene, xylene, DMF, N, N-dimethylacetanilide, 1- methyl 2-pyrrolidone, tetrahydrofuran, preferably DMF, or in an anhydrous protic solvent such as ethanol, isopropanol, tert-butanol. As a base, 1-1.3 equivalents of a metal hydride of the formula MeH _n or a metal alkoxide (RO) _n Me are used, where Me is a metal of the first or second group of the Periodic Table, n is the valence of the metal, R is the remainder of the C1-C4 alcohol group. The reaction is carried out by heating in the temperature range of 40 - 100 ° C for 3-5 h. The monoester of 2-isobutylidene succinate obtained in the course of the reaction in situ is reacted with 1.1 - 1.2 equivalents of an alkylating agent (alkyl halide, dialkyl sulfate) for 30 min - 2 h. into diester 3a-c. After the extraction treatment, the material can be purified by vacuum distillation.

In the second stage, the sum of alkylidene succinic esters 3a-c is reacted with isobutylaldehyde taken with an excess of 0-30% in an aprotic solvent such as toluene, ethylbenzene, xylene, DMF, N, N-dimethylacetanilide, 1-methyl- 2-pyrrolidone, tetrahydrofuran, or in an anhydrous protic solvent such as ethanol, isopropanol, tert-butanol. As a base, 1-1.3 equivalents of a metal hydride of the formula MeH _n or a metal alkoxide (RO) _n Me are used, where Me is a metal of the first or second group of the Periodic System, n is the valence of the metal, R is the remainder of the C1-C4 alcohol group. The reaction is carried out by heating in the temperature range of 40 - 100 ° C for 3-5 hours.The monoester of 2,3-bis-isobutylidene succinate obtained in the course of the reaction in situ by interaction with 1.1 - 1.2 equivalents of an alkylating agent (alkyl halide, dialkyl sulfate) for 30 minutes - 2 hours are converted into diester 4a-e. After the extraction treatment, the product can be purified by vacuum distillation.

The first and second stages of the process can be combined and carried out "in one vessel" without isolating intermediate products 3a-c. For this, 1-1.3 equivalents of the base used and 1-1.3 equivalents of isobutyl aldehyde are added to the reaction mass obtained in the first stage. The reaction is carried out by heating in the temperature range of 40-100 ° C for 3-5 hours.The monoester of 2,3-bis-isobutylidene succinate obtained in the course of the reaction in situ by interaction with 1.1-1.2 equivalents of an alkylating agent (alkyl halide, dialkyl sulfate) for 30 minutes - 2 hours are converted into diesters 4a-e. After the extraction treatment, the product can be purified by vacuum distillation.

At the third stage, the resulting mixture of isomeric bis-isobutylidene-substituted succinates 4a-e without preliminary separation is hydrogenated with hydrogen at temperatures of 100-200 ° C and a pressure of 60-200 bar on hydrogenation catalysts: 5-10% palladium or platinum on carbon, or skeletal nickel to form anti- and syn- isomers 1a, b. Lower alcohols C1-C3 or linear or branched C5-C8 hydrocarbons are used as a solvent. After purification of the product by vacuum distillation, 2,3-bis-isobutyl succinate 1 is obtained with a purity of more than 95%.

Thus, we propose a new method for the synthesis of 2,3-diisobutyl succinate diester 1, which makes it possible to obtain the target product with a purity of at least 95% using inexpensive commercially available reagents and solvents, and conventional chemical equipment.

The resulting diesters of 2,3-diisobutyl succinate, in particular diethyl 2,3-diisobutyl succinate 1, can be used to prepare titanium-magnesium catalysts for the polymerization of propylene into isotactic polypropylene as a stereoregulating electron-donor component, as evidenced by Examples 7-9.

The invention is illustrated by the following examples.

Example 1. Approach to the synthesis of diethyl 2,3-diisobutyl succinate 1 according to the method of WO 2013029767

Suspension of NaH in oil (60%) (64 mg (1.61 mmol)) was washed 2 times with hexane, 5 ml each, decanted, the remaining solvent was distilled off on a rotary evaporator. 1 ml of dry DMF was added, the flask was purged with argon. At room temperature and stirring, 324 mg (1.07 mmol) of triethyl 1-isobutylethane-1,1,2-tricarboxylate synthesized according to the method (WO 2013029767) was added dropwise, the mixture was stirred for 30 min at room temperature. Isobutyl bromide 220 mg (1.61 mmol) was added dropwise. The reaction mixture was stirred at T = 85 ° C for 8 hours. The reaction mixture was cooled, diluted with 5 ml of water and extracted with 3 * 5 ml of methylene chloride. The combined organic phase was washed with 2 ml of saturated NaCl solution, dried with MgSO ₄ . The desiccant was filtered off, the solvent was distilled off on a rotary evaporator. Instead of the expected triethyl-1,2-bis izobutiletan-1,1,2-tricarboxylate received 177 mg of a mixture of the starting compound and its iso-butyl ether in a ratio of 48: 52, according to ¹ H NMR

Example 2. Synthesis of compounds 3а-c in ethanol.

In an inert atmosphere, 3 ml of ethanol was added to 145 mg of sodium (6.28 mmol) and stirred until dissolved. To the resulting solution was added a solution of 1.044 g (6 mmol) of diethyl succinate and 0.411 g (5.71 mmol) of isobutyraldehyde in 1 ml of ethanol. The reaction mixture was refluxed for 7.5 h. 0.654 g (6 mmol) of ethyl bromide was added, the reaction mixture was refluxed for 2 h. The reaction mixture was cooled, evaporated, diluted with water, and extracted with MTBE. The combined organic phase was dried with MgSO ₄ . The desiccant was filtered off, the solvent was distilled off on a rotary evaporator. Received 0.509 g of a mixture of compounds 3а-c, yield 44%.

Example 3. Synthesis of compounds 3а-c in DMF.

35 ml of DMF was added to 0.18 mol of NaH, cooled to 0 ° С, and a solution of 30 ml (0.18 mol) of diethyl succinate and 18.5 ml (0.198 mol) of isobutyraldehyde in 40 ml of DMF was added. The reaction mixture was stirred at 60 ° С for 3 h. 16 ml (0.207 mol) of ethyl bromide were added, the reaction mixture was stirred at 60 ° С for 2 h. The reaction mixture was cooled, diluted with 450 ml of water, and extracted with MTBE. The combined organic phase was washed with saturated NaCl solution, dried with MgSO ₄ . The desiccant was filtered off, the solvent was distilled off on a rotary evaporator. Received 36.19 g of a mixture of compounds 3а-c in the ratio 54: 28: 17 according to CMS data, yield 88%.

Characteristic signals of the ¹ H NMR spectrum of the mixture of compounds 3а-c, ¹ H NMR spectrum (400 MHz, CDCl ₃ , δ, ppm, J / Hz): compound 3а: 2.39 dd (1Н, Н-3, 16.4, 6.0) , 2.79 dd (1H, H-3, 16.4, 9.0), 3.65 ddd (1H, H-2, 9.5, 9.0, 6.0), 5.01 dm (1H, H-1 ', 9.5). Compound 3b (E-isomer): 3.31 s (2H, H-3), 6.73 dm (1H, H-2 ', 10.2). Compound 3c (Z-isomer): 3.20 s (2H, H-3), 5.79 dm (1H, H-2 ', 9.8).

Example 4. Synthesis of compound 1 with a purity of 75%.

A) To 0.25 mol of NaH was added 30 ml of DMF, a solution of 42 ml (0.25 mol) of diethyl succinate and 26 ml (0.275 mol) of isobutyraldehyde in 50 ml of DMF was added at room temperature. The reaction mixture was stirred at 60 ° С for 3 h. 25 ml (0.288 mol) of ethyl bromide was added, the reaction mixture was stirred at Т60 ° С for 2 h. 0.288 mol of NaH and 27 ml (0.288 mol) of isobutyraldehyde in 30 ml were added DMF. The reaction mixture was stirred at 60 ° С for 3 h. 25 ml (0.288 mol) of ethyl bromide were added, the reaction mixture was stirred at 60 ° С for 2 h. The reaction mixture was cooled, diluted with water, and extracted with MTBE. The combined organic phase was washed with saturated NaCl solution, dried with MgSO ₄ . The desiccant was filtered off, the solvent was distilled off on a rotary evaporator. Received 30.39 g of a mixture of compounds 4а-е, yield 43%. According to CMS data, the ratio of compounds 4а-е in the mixture was 16.7: 15: 6.8: 6.5: 4: 1.

B) A solution of 29.39 g (0.104 mol) of compounds 4а-е in 60 ml EtOH (96%) and a suspension of Rennay nickel prepared from 5.00 g of Rennay alloy (I.B. Repinskaya, M.S. Schwarzberg, Selected methods for the synthesis of organic compounds, Novosibirsk: Novosibirsk University Press, 2000, p. 80), in 20 ml EtOH (96%). Hydrogenation was carried out at a hydrogen pressure of 100 atm. at 180 ° C and a reaction time of 20 h. The solvent was distilled off, 23.98 g of oil was obtained, which was distilled in vacuum, the fraction with Tb = 120-140 ° C (3 mm Hg) was collected, and 13.35 g of compound 1 with a purity of 60 %. The resulting fraction was distilled in vacuum again, the fraction with Tbp = 100 - 120 ° C (1 mm Hg) was taken, 6.62 g of compound 1 was obtained with a purity of 75% by CMS, the yield was 22%.

Example 5. Synthesis of compound 1 with a purity of 96%.

A) To 0.159 mol of NaH was added 30 ml of DMF, cooled to 0 ° С, a solution of 36.19 g (0.159 mol) of compound 3 (mixture of isomers) and 19.1 ml (0.206 mol) of isobutyraldehyde in 40 ml of DMF was added. The reaction mixture was stirred at 60 ° С for 3 h. 14.5 ml (0.190 mol) of ethyl bromide was added, the reaction mixture was stirred at ° С for 2 h. The reaction mixture was cooled, diluted with 450 ml of water, and extracted with MTBE. The combined organic phase was washed with saturated NaCl solution, dried with MgSO ₄ . The desiccant was filtered off, the solvent was distilled off on a rotary evaporator. Received 41.79 g of a mixture of compounds 4а-е in the ratio 45: 29: 10: 7: 5: 3 according to CMS data, yield 94%. After distillation in vacuum (5 mm Hg), 26.75 g of compound 4 with Bp = 126-158 ° C was obtained, yield 60%.

B) A solution of 26.75 g (0.095 mol) of compound 4 in 70 ml of EtOH (96%) and a suspension of Rennay nickel prepared from 4.50 g of Rennay's alloy in 20 ml of EtOH (96%) were placed in a steel autoclave with a capacity of 0.5 L. Hydrogenation was carried out at a hydrogen pressure of 100 atm and T = 180 ° C and a reaction time of t = 24 h. The solvent was distilled off on a rotary evaporator to obtain 23.86 g of oil. The substance was distilled in a vacuum, a fraction with Tb = 121-148 ° C (3 mm Hg) was taken, and 19.97 g of compound 1 was obtained with a purity of 93%. The resulting fraction was distilled in vacuum again, the fraction with Tb = 100 - 116 ° C (1 mm Hg) was taken, 16.70 g of compound 1 with a purity of 96% by CMS was obtained, the yield was 61%.

NMR ¹ H (400 MHz, CDCl ₃ , δ, ppm, J / Hz): 0.84, 0.87 d (6H + 6H, 4CH ₃ , 6.1), 0.99-1.10 m (2H, H-1 '), 1.22, 1.24 t (3H + 3H, 2OCH ₂ CH ₃ , 7.0), 1.37-1.69 m (4H, 2H-1 ', 2H-2'), 2.60-2.71 m (2H, H-2, H-3) , 4.06-4.20 m (4H, 2OCH ₂ ).

Example 6. Synthesis of compound 1 with a purity of 99%.

A) To 0.12 mol of NaH was added 20 ml of DMF, cooled to 0 ° С, and a solution of 20 ml (0.12 mol) of diethyl succinate and 12.2 ml (0.132 mol) of isobutyraldehyde in 25 ml of DMF was added. The reaction mixture was stirred at 60 ° С for 3 h. 10.4 ml (0.138 mol) of ethyl bromide was added, the reaction mixture was stirred at 60 ° С for 2 h. 0.138 mol of NaH in 25 ml of DMF was added. A solution of 12.8 ml (0.138 mol) of isobutyraldehyde in 13 ml of DMF was added. The reaction mixture was stirred at 60 ° С for 3 h. 10.4 ml (0.138 mol) of ethyl bromide was added, the reaction mixture was stirred at 60 ° С for 2 h. The reaction mixture was cooled, diluted with water, and extracted with MTBE. The combined organic phase was washed with saturated NaCl solution, dried with MgSO ₄ . The desiccant was filtered off, the solvent was distilled off on a rotary evaporator. Received 27.97 g of a mixture of compounds 4а-е, yield 83%. After distillation in a vacuum (5 mm Hg), 17.98 g of substance 4 with Tb = 128-158 ° C was obtained, the yield was 53%. According to CMS data, the ratio of compounds 4а-е in the mixture was 33: 29: 8: 6: 2: 3.

B) A solution of 17.98 g (0.064 mol) of compound 4 in 100 ml EtOH (96%) and a suspension of Rennay nickel prepared from 3.00 g of Rennay's alloy in 20 ml of EtOH (96%) were placed in a steel autoclave with a capacity of 0.5 L. Hydrogenation was carried out at a hydrogen pressure of 100 atm and T = 180 ° C and a reaction time of t = 24 h.The solvent was distilled off on a rotary evaporator, 17.22 g of oil was obtained, which was distilled in a vacuum, a fraction with Tb = 123-133 ° C (3 mm Hg), 7.31 g of compound 1 with a purity of 93% were obtained. The resulting fraction was distilled in vacuum again, the fraction with Tb = 122 - 128 ° C (3 mm Hg) was taken, 5.64 g of compound 1 was obtained with a purity of> 99% by CMS, the yield was 31%.

Example 7. Preparation of a propylene polymerization catalyst using compound 1 with a purity of 75% as an internal donor.

The preparation of the catalyst was carried out in three stages: (1) preparation of the organomagnesium compound (product I); (2) preparation of a magnesium-containing carrier (product II); (3) preparation of the catalyst. These steps were carried out according to example 1 in US Pat. RU 2152404 C1.

Preparation of Intermediate I

Magnesium powder (26 g, 1.07 g / atom) was charged into a three-necked flask equipped with a reflux condenser, dropping funnel and stirrer. The flask was purged with nitrogen, the magnesium powder was heated for 1 h at 80 ° C, and a mixture of 173 ml of di-n-butyl ether and 80 ml of chlorobenzene was added. Then, 0.03 g of iodine and 3 ml of n-butane chloride are added successively to the reaction mixture. After the disappearance of the iodine coloration, the temperature of the reaction mixture is increased to 97 ° C and 250 ml of chlorobenzene is metered in within 2.5 hours. The resulting dark reaction mixture was stirred for 8 hours at 97 ° C. Then, stirring and heating were stopped, the solid product was allowed to settle for 48 h. After the solution was decanted over the precipitate, a solution of product I with a concentration of 1.0 mol Mg / L was obtained.

Preparation of Intermediate II

A solution of product I (100 ml, 1.0 mol / L), obtained as described above, is loaded into the reactor. This solution was cooled to 0 ° C and a solution of 11.2 ml of tetraethoxysilane (TES) in 38 ml of di-n-butyl ether was added over 2 h with stirring. After adding the solution, the reaction mixture was kept for 0.5 h at 0 ° С, then the temperature was increased to 60 ° С and kept for another 1 h at 60 ° С. Thereafter, stirring and heating are stopped and the solid is allowed to settle for 30 minutes. The supernatant is removed by decantation. The solid is washed 5 times with 150 ml of heptane. A light yellow substance is obtained — 13.5 g of product II, suspended in 40 ml of heptane.

Preparation of the catalyst

A 500 ml reactor was purged with nitrogen and charged with 300 ml of titanium tetrachloride at room temperature. Then the reactor is heated to 115 ° C in a glycerol bath and a suspension containing 12 g of product II in 40 ml of heptane is added. After that, 4.2 g of stereoregulating electron donor agent 1 obtained in example 4 (diethyl 2,3-diisobutyl succinate with a purity of 75%) is added to the reactor, and the reaction mixture is stirred at 115 ^° C for 1.5 h. After that, stirring is stopped and solid the substance is allowed to settle for 30 minutes. The supernatant is removed by decantation, after which 300 ml of chlorobenzene is added to the reactor, the reactor is heated to 100 ° C and held for 20 minutes. The stirring is then stopped and the solid is allowed to settle for 30 minutes. The supernatant is removed by decantation, after which a mixture of 150 ml of titanium tetrachloride and 150 ml of chlorobenzene is added to the reactor. The reaction mixture is heated to 115 ° C and stirred for 30 minutes, followed by the above-described precipitation and decantation procedure. The last cycle is repeated once more. The resulting solid was washed 5 times with 300 ml of heptane at 60 ° C., and thereafter, a catalyst suspended in heptane was obtained.

Polymerization of propylene

The polymerization of propylene was carried out according to example 1 in US Pat. RU 2152404 C1. The stainless steel polymerization reactor is purged with nitrogen and then filled with dried heptane (290 ml) free of oxygen. Then a solution of 1.2 mmol of triethylaluminum in 5 ml of heptane, 0.06 mmol of cyclohexylmethyldimethoxysilane (donor D ₂ ) dissolved in 5 ml of heptane and 0.01 g of catalyst in the form of a suspension in 1 ml of heptane is introduced into the reactor. Then add 33 ml (under normal conditions) of hydrogen and propylene until a pressure of 0.05 MPa is reached. Stirring is turned on and the reactor is quickly heated to a polymerization temperature of 70 ° C, propylene is fed to a pressure of 0.6 MPa, and under these conditions, the polymerization process is carried out for 1 hour. After that, the pressure is reduced to atmospheric, the contents of the reactor are drained and the polymer powder is separated from heptane. After that, the polypropylene powder is dried in a vacuum oven and weighed.

The polymerization results are shown in Table 1.

Example 8.

The catalyst was prepared analogously to example 7, except that compound 1 obtained in example 5 (diethyl 2,3-diisobutyl succinate with a purity of 96%) was used as a stereoregulating electron-donor agent.

The polymerization is carried out analogously to example 7. The results of the polymerization are shown in Table 1.

Example 9.

The catalyst was prepared analogously to example 7, except that compound 1 obtained in example 6 (diethyl 2,3-diisobutyl succinate with a purity of 99%) was used as a stereoregulating electron-donor agent.

The polymerization is carried out analogously to example 7. The results of the polymerization are shown in table 1.

Table 1. Results of experiments on propylene polymerization

¹⁾ 1 - diethyl 2,3-di-isobutyl succinate.

²⁾ Determination of the amount of the PP fraction soluble in xylene (XS) was carried out according to the method described in the US standard ASTM D-5492.

³⁾ The isotacticity index (II) of the polypropylene powder was calculated as 100 - XS.

⁴⁾ Polypropylene polydispersity (M _w / M _n ) was determined at 160 ° C by gel permeation chromatography.

The catalysts have an average particle size of 17 μm (according to laser diffraction data) and high activity (PP yield). Catalysts 2 and 3, prepared with samples of diethyl 2,3-diisobutyl succinate having a purity of ≥ 95%, make it possible to obtain PP with the required high isotacticity (II values> 97%). The prepared catalysts also make it possible to obtain PP with the required broad molecular weight distribution (the M _w / M _n value is in the range 5-6).

List of sources used

G. Morini, G. Balbontin, Y. Gulevich, R. Kelder, H. Duijghuisen, P. Klusener, F. Korndorffer. Components and catalysts for the polymerization of olefins // Patent WO 2000063261 A1.

T. Taniike, M. Terano. The Use of Donors to Increase the Isotacticity of Polypropylene. In: Kaminsky W. (eds) Polyolefins: 50 years after Ziegler and Natta I. // Advances in Polymer Science, vol 257, 81-98. Springer, Berlin, Heidelberg.

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Claims (7)

1. A method of obtaining dialkyl 2,3-di-isobutyl-succinates of formula 1 from succinic acid diester,

comprising the steps of double condensation of isobutyl aldehyde with a diester of succinic acid in an aprotic solvent or in an anhydrous protic solvent, preferably DMF; 1-1.3 equivalent of a metal hydride of the formula MeH _n or a metal alkoxide (RO) _n Me is used as a base, where Me is a metal of the first or second group of the Periodic system, n is the valence of the metal, R is the remainder of the C1-C4 alcohol group, the reaction carried out by heating in the temperature range of 40–100 ° C for 3-5 hours, with the formation of a mixture of mono- and bis-ethylidene compounds, with intermediate esterification and the subsequent stage of hydrogenation of the mixture of dienes. 2. The method according to claim 1, characterized in that at the first stage the diester of succinic acid is reacted with isobutyl aldehyde, the monoester of 2-isobutylidene succinate obtained during the reaction is converted into the diester of 2-isobutylidene succinate by interaction with an alkylating agent. 3. The method according to claim 1, characterized in that in the second stage a mixture of 2-isobutylidene succinic diesters is reacted with isobutyl aldehyde, the monoester of 2,3-bis-isobutylidene succinate obtained during the reaction is converted into a bis- isobutylidene succinate. 4. The method according to claim 1, characterized in that in the third stage, the mixture of isomeric bis-isobutylidene-substituted succinates without preliminary separation is hydrogenated with hydrogen at temperatures of 100-200 ° C and a pressure of 60-200 bar on hydrogenation catalysts: palladium, platinum on carbon, 5 -10% skeletal nickel. 5. The method according to claim 1, characterized in that the first and second stages of condensation of isobutyl aldehyde with succinic acid diester are carried out "in one vessel", without isolating intermediate 2-isobutylidene succinic diesters.

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