Method for producing lithium alkylide solutions

Abstract

The invention relates to a method for producing lithium alkylide compounds for use as anionic polymerization initiators and for various organic reactions. More specifically, the present invention relates to a process for preparing a lithium alkylide solution by reacting a lithium metal having a specific surface area of 1 to 100 cm2 / g with an alkyl halide in an organic solvent medium under high turbulence conditions wherein the molar ratio of lithium metal to alkyl halide is 2.5: 1 to 5.5: 1. The technical result achieved by the invention is that a high lithium alkylide yield is achieved using a lithium metal having a low specific surface area under high turbulence conditions and at a molar ratio of lithium metal to alkyl halide of 2.5: 1 to 5.5: 1, comparable to the lithium alkylide yield achieved using finely dispersed lithium metal particles having a high specific surface area.

Description

Technical Field

[0001] The present invention relates to a method for producing a solution of an alkyllithium compound used as an anionic polymerization initiator in various organic reactions. Background Art

[0002] Alkyllithium compounds are widely used as initiators for diene polymerization and diene copolymerization, such as copolymerization of a diene with a vinyl aromatic compound.

[0003] Currently, in industry, alkyllithium is usually produced by melting lithium metal, dispersing the resulting lithium melt in oil or an alkane under high-speed stirring in an inert atmosphere, and then washing the resulting dispersed lithium metal particles from the oil with a solvent that also serves as a solvent in subsequent steps of alkyllithium synthesis. Then, an alkyl halide is added to the dispersion of lithium metal in the solvent to produce alkyllithium. This method is disclosed, for example, in patent RU 2691649 (published on June 17, 2019, by Glukhovskoy V.S., Blinov E.V., Papkov V.N., Zemsky D.N., Stepanov I.M.), where lithium metal is pre-dispersed in vaseline oil and then the dispersed lithium is washed from the oil using nefras (petroleum solvent).

[0004] The main disadvantage of this method is the need to pre-prepare a dispersion of lithium metal. This is a time-consuming and expensive procedure that requires high energy consumption for melting lithium metal, stirring the resulting highly viscous melt using a powerful stirring device, high consumption of organic solvents for washing the resulting dispersion from the oil, and the cost of separating the resulting oil emulsion and solvent. In addition, the resulting alkyllithium may contain impurities due to incomplete washing of the dispersed lithium particles from the oil residue and due to side reactions of lithium with impurities of aromatic and unsaturated compounds that may be present in the oil.

[0005] It is also known from the prior art that, to increase the efficiency of alkyllithium synthesis, it is preferable to use lithium metal in the form of particles with a particle size of less than 300 microns (US5332533, FMC Corporation, published on July 26, 1994). This is explained by the fact that the reaction of an alkyl halide with lithium mainly occurs on the surface of the metal, and therefore the smaller the metal particles, the larger the specific surface area and the faster the reaction proceeds.

[0006] Therefore, Patent RU 2095362 (published on November 10, 1997, Shcherban G.T.) discloses a method for producing n-butyllithium, which is carried out in a hydrocarbon solvent in the presence of an inert gas. In the first step, n-butyl chloride is reacted with a lithium metal dispersion with a particle size of 5 to 300 microns in a reactor at a temperature of 0 to 60 °C. Subsequently, in the second step, the reaction mass is maintained at a temperature of 65 to 90 °C. It is characterized in that in the first step, the synthesis of n-butyllithium is carried out with a molar ratio of n-butyl chloride to lithium of 0.65 - 0.85 required stoichiometrically. The resulting reaction product is separated, the unreacted lithium is fed back into the synthesis at the same component ratio, and the n-butyllithium solution obtained during separation is sent to the second step of the synthesis, which is completed after adding a second portion of the n-butyllithium solution and the remaining amount of n-butyl chloride. In addition, in the first step, the synthesis is carried out, where the reaction mass is continuously circulated through a condenser, and n-butyl chloride is fed at a mass rate of 0.25 - 2.5 hr -1 and preferably added at the point with the lowest temperature.

[0007] The main disadvantages of the disclosed method are the complexity of its practical implementation and the possibility of forming a stable suspension of lithium chloride by-products in the n-butyllithium solution under the described conditions of long-term intense mechanical stirring. Therefore, the obtained n-butyllithium contains a large amount of lithium chloride that is not separated during filtration.

[0008] Patent US7005083 (published on February 28, 2006, SQM Lithium Specialties Limited Partnership) discloses a method for preparing an alkyllithium compound in a liquid hydrocarbon solvent selected from liquid saturated aliphatic hydrocarbons containing 5 - 12 carbon atoms, saturated liquid cycloaliphatic hydrocarbons containing 6 - 12 carbon atoms, or a mixture thereof. The method is carried out by reacting an alkyl halide containing 3 - 16 carbon atoms with metal particles with a particle size of less than 300 microns (using a lithium-sodium alloy with a sodium content of 15 - 34 wt% as the metal). The method allows obtaining a high-purity alkyllithium compound with a yield of at least 90%. The disadvantages of this method for preparing an alkyllithium compound are that the handling of the lithium-sodium alloy poses a high risk of fire and explosion, and a slurry of lithium chloride and sodium chloride is formed, which is difficult to separate from the target product.

[0009] There is known a method for producing alkyllithium by reacting a lithium dispersion with an alkyl halide in a hydrocarbon solvent using lithium metal in the form of a dispersion having a particle size of at most 300 microns, said dispersion being produced by atomizing molten lithium in an argon atmosphere at a temperature of 200 - 230 °C (US7326372, CHEMETALL GMBH, published on February 5, 2008). A disadvantage of this method is the need to use complex equipment for atomizing lithium at a temperature of 200 - 230 °C.

[0010] The use of finely divided lithium particles ensures the completeness of the alkyllithium formation reaction. However, it causes technical problems, especially that too small particles tend to form cakes on the filtration equipment, which leads to frequent shutdowns.

[0011] Another important factor is that handling finely divided lithium poses a high risk of fire.

[0012] Patent US5523447 (FMC CORP, published on June 4, 1996) discloses a method for preparing an alkyllithium compound by reacting massive lithium metal weighing more than 0.5 grams with alkyl chloride in a hydrocarbon solvent in an inert atmosphere with moderate stirring or no stirring at all at a lithium to alkyl chloride molar ratio of 3:1 to 20:1.

[0013] A disadvantage of this method is the high lithium to alkyl chloride ratio of 3:1 or higher. It is also possible that unreacted lithium may be entrained in the solution containing the target product and leave the reactor and clog pipes and fittings.

[0014] Furthermore, in the case of slow stirring or no stirring at all, the metallic lithium is rapidly covered with lithium chloride sludge, and subsequent washing with fresh solvent as proposed in the above patent cannot completely remove the sludge. In addition, as the reaction proceeds, lithium chloride is formed on the surface of the lithium metal, which results in hindering the contact of butyl chloride with the uncontaminated lithium metal, and the preferential side reaction of butyl chloride with the formed butyllithium starts to proceed to produce lithium chloride and octane.

[0015] Therefore, there is still a need to provide a method for producing an alkyllithium solution that overcomes all of the above disadvantages. Summary of the Invention

[0016] The object of the present invention is to provide an effective method for producing an alkyllithium solution using lithium metal with a relatively low specific surface area while ensuring a high yield of alkyllithium, which overcomes all of the above disadvantages associated with the use of finely divided lithium metal particles (lithium with a high specific surface area).

[0017] This object is achieved by providing a method for producing an alkyllithium solution by reacting lithium having a specific surface area of 1 to 100 cm 2From 1 to 100 cm² / g of lithium metal reacts with an alkyl halide in an organic solvent medium under high-turbulence conditions, where the molar ratio of lithium metal to alkyl halide is from 2.5:1 to 5.5:1.

[0018] In the context of the present invention, the term "high turbulence" should be understood to refer to the flow state of a reaction stream with a Reynolds number greater than 10,000, characterized by extremely irregular random variations in velocity over time at each particle of the reaction stream.

[0019] The technical effect achieved by the present invention is that under high-turbulence conditions, in an organic solvent medium, using lithium metal with a specific surface area of 1 to 100 cm² 2 / g and an alkyl halide results in an alkyl lithium yield greater than 90%, with the molar ratio of lithium metal to alkyl halide being from 2.5:1 to 5.5:1, which is comparable to the alkyl lithium yield achieved using finely divided lithium metal particles with a high specific surface area.

[0020] Another technical effect achieved by the present invention is the reduction in the number of steps in the method for producing an alkyl lithium solution, as there is no need to pre-disperse the lithium metal to obtain finely divided lithium metal particles, nor to perform their subsequent washing from the dispersion medium (oil or paraffin). This also allows for minimizing the loss of lithium metal that may occur in each of these steps.

[0021] Another technical effect achieved by the present invention is the increase in the fire and explosion safety of the method for producing an alkyl lithium solution, as there is no need to use highly pyrophoric finely divided lithium metal particles.

[0022] Furthermore, the inventors have unexpectedly found that under high-turbulence conditions, using lithium metal with a specific surface area of 1 to 100 cm² 2 / g at a molar ratio of lithium metal to alkyl halide from 2.5:1 to 5.5:1 enables the synthesis of alkyl lithium with an alkyl lithium yield greater than 90%, and there is no significant increase in the reaction time compared to using finely divided lithium metal particles. Detailed Description

[0023] The following is a detailed description of the various aspects and embodiments of the present invention.

[0024] The present invention relates to a method for producing an alkyl lithium solution by reacting lithium metal with a specific surface area of 1 to 100 cm² 2 / g, preferably 5 to 70 cm² 2 / g, most preferably 10 to 30 cm² 2 / g with an alkyl halide in an organic solvent medium under high-turbulence conditions, where the molar ratio of lithium metal to alkyl halide can be from 2.5:1 to 5.5:1, preferably from 2.5:1 to 5:1, more preferably from 3:1 to 4.5:1.

[0025] The lithium metal can be used in any form, for example, in the form of a block or cylinder with a weight of 0.05 to 1 g, preferably 0.08 to 0.8 g, and most preferably 0.1 to 0.5 g.

[0026] The specific surface area of the lithium metal used can be determined by any method (calculation method and experimental method) known in the prior art, for example, by low-temperature nitrogen adsorption according to the Brunauer-Emmett-Teller method (BET). The calculation method is based on the geometric concept of the shape and size of the lithium metal. For example, the specific surface area of a cylindrical lithium metal can be determined using the following formula: the surface area of the cylinder 2πrh + 2πr 2 Divided by the mass of the cylinder, where h is the height of the cylinder and r is the diameter of the cylinder.

[0027] The sodium content of the lithium metal can be 50 - 2000 ppm, preferably 100 - 1500 ppm, more preferably 150 - 1000 ppm, and even more preferably 250 - 500 ppm.

[0028] Chlorides, bromides, or iodides can be used as alkyl halides, but chlorides are most preferably used. Alkyl chlorides include, but are not limited to: methyl chloride, ethyl chloride, n-propyl chloride, n-butyl chloride, sec-butyl chloride, tert-butyl chloride, and n-hexyl chloride. Preferred are n-butyl chloride, sec-butyl chloride, or tert-butyl chloride.

[0029] Suitable organic solvents include, but are not limited to: C5 - C7 alkanes, such as n-hexane, n-heptane; cycloalkanes, such as cyclohexane; or mixtures thereof in various proportions, such as petroleum solvents (nefras) and petroleum ether. Hexane, cyclohexane, or petroleum solvents are preferably used, and hexane and petroleum solvents are most preferably used, such as petroleum solvent P1 63 / 75, which is a hexane - heptane fraction.

[0030] The feeding rate of adding the required amount of alkyl halide to the lithium metal in the organic solvent can be any feeding rate, and it is selected such that the temperature of alkyl lithium synthesis does not exceed 75 °C, preferably 50 to 73 °C, and more preferably 60 to 70 °C. If the temperature exceeds 75 °C, a preferential side reaction of forming lithium chloride may occur.

[0031] The time for alkyl lithium synthesis can be any time sufficient to achieve zero alkyl halide content in the reaction mass. In a preferred embodiment, the time for alkyl lithium synthesis can be at most 24 hours, preferably at most 18 hours, and most preferably at most 10 hours.

[0032] After the feeding is completed, the reaction mass is maintained at a temperature of 55 - 85 °C, preferably 65 - 75 °C, for 2 - 8 hours, preferably 4 - 8 hours.

[0033] When implementing the method of the present invention, the type and stirring speed of the stirring device are not critical, and any stirring device and stirring speed can be used, provided that a turbulent energy dissipation rate (ε) of 0.01 - 0.3 m 2 / s 3 is ensured, preferably 0.02 - 0.2 m 2 / s 3 and more preferably 0.03 - 0.1 m 2 / s 3 . By maintaining the turbulent energy dissipation rate (ε) within a given range, the required conditions for high turbulence of the reaction mass flow in the reactor can be provided, which makes it possible to prevent the adhesion of lithium chloride sludge to the lithium metal surface and thus ensure the effective interaction between the lithium metal and the alkyl halide. At an energy dissipation rate (ε) higher than 0.3 m 2 / s 3 , due to the fact that the mixture of the solvent and the alkyl halide is mainly distributed near the reactor wall and has a weak interaction with the lithium metal, the yield of alkyllithium will decrease; in addition, separate circulation loops of the reaction materials may be formed, which also interact weakly with each other.

[0034] The stirring time corresponds to the total feeding time and the holding time of the reaction materials after the feeding of the alkyl halide is completed.

[0035] The method for producing an alkyllithium solution must be carried out in a reactor made of a material that is inert to the substances used in the method for producing the alkyllithium solution. In particular, the method for producing an alkyllithium solution can be carried out in a titanium reactor, a stainless steel reactor or an enamel reactor.

[0036] The synthesized alkyllithium solution is filtered to purify it from lithium chloride sludge, where the content of lithium chloride sludge in the alkyllithium solution should not exceed 0.4%, and preferably the sludge should be completely absent. The filtration can be carried out at any temperature, preferably at a temperature of 20 - 40°C, more preferably 20 - 30°C, using any filtration device known in the prior art, such as a filter with a porous filter wall and a vacuum suction filter, and preferably a vacuum suction filter is used.

[0037] The filtered alkyllithium solution can be further diluted with an organic solvent to obtain the concentration required for subsequent use as an initiator in diene polymerization and diene copolymerization, such as copolymerization with vinyl aromatic compounds, and to comply with the Agreement concerning the International Carriage of Dangerous Goods by Road (ARD). In particular, n-butyllithium in the form of a solution with a n-butyllithium concentration of 15 to 90% belongs to the category of substances capable of spontaneous combustion (category 4.2), and therefore it is transported only according to ARD.

[0038] The alkyllithium produced by the method according to the present invention can include but is not limited to: propyllithium, butyllithium, pentyllithium, hexyllithium, preferably butyllithium.

[0039] Example 1 (comparative)

[0040] 151.5 g of lithium and 2 kg of petroleum solvent (P1 63 / 75) were added to a 5 L reactor. The lithium was used in the form of a dispersion with a specific surface area of 293 cm 2 / g. The reactor contents were heated to 60 °C, and then 1 kg of n-butyl chloride was added at 300 rpm over 7 hours such that the reaction temperature did not exceed 70 °C. The molar ratio of lithium to n-butyl chloride was 2.02:1. After completion of the n-butyl chloride addition, the reaction mass was held at 65 °C for 8 hours. The yield of n-butyllithium was 99.2%.

[0041] Example 2 (comparative)

[0042] 151.5 g of lithium and 2 kg of petroleum solvent (P1 63 / 75) were added to a 5 L reactor. The lithium was used in the form of a cylinder having dimensions of 6 × 12 mm and a calculated specific surface area of 15.6 cm 2 / g. The reactor contents were heated to 60 °C, and then 1 kg of n-butyl chloride was added at 300 rpm (corresponding to 0.05 m 2 / s 3 of ε) with stirring over 7 hours such that the reaction temperature did not exceed 70 °C. The molar ratio of lithium to n-butyl chloride was 2.02:1. After completion of the n-butyl chloride addition, the reaction mass was held at 65 °C for 8 hours. The yield of n-butyllithium was 66.7%.

[0043] Example 3 (according to the present invention)

[0044] The preparation of n-butyllithium was carried out similar to Example 2, except that the molar ratio of lithium to n-butyl chloride was 3:1. The yield of n-butyllithium was 95.2%.

[0045] Example 4 (according to the present invention)

[0046] The preparation of n-butyllithium was carried out similar to Example 3, except that the stirring speed was 500 rpm (corresponding to 0.15 m 2 / s 3 of ε). The yield of n-butyllithium was 97.2%.

[0047] Example 5 (according to the present invention)

[0048] The preparation of n-butyllithium was carried out similar to Example 2, except that the molar ratio of lithium to n-butyl chloride was 4:1. The yield of n-butyllithium was 99.3%.

[0049] Example 6 (according to the present invention)

[0050] The preparation of n-butyllithium was carried out similar to Example 5, except that the stirring speed was 500 rpm (corresponding to ε of 0.15 m 2 / s 3 ). The yield of n-butyllithium was 99.4%.

[0051] Example 7 (according to the present invention)

[0052] The preparation of n-butyllithium was carried out similar to Example 5, except that the stirring speed was 600 rpm (corresponding to ε of 0.28 m 2 / s 3 ). The yield of n-butyllithium was 99.4%.

[0053] Example 8 (according to the present invention)

[0054] The preparation of n-butyllithium was carried out similar to Example 2, except that the molar ratio of lithium to n-butyl chloride was 4.5:1. The yield of n-butyllithium was 99.2%.

[0055] Example 9 (according to the present invention)

[0056] 225 g of lithium and 2 kg of petroleum solvent (P1 63 / 75) were added to a 5 L reactor. The lithium was used in the form of tablets having a size of 10×5 mm and a specific surface area of 15 cm 2 / g determined by a calculation method. The reactor contents were heated to 60 °C, and then 1 kg of n-butyl chloride was added dropwise with stirring at 300 rpm (corresponding to ε of 0.05 m 2 / s 3 ) over 7 hours such that the reaction temperature did not exceed 70 °C. The molar ratio of lithium to n-butyl chloride was 3:1. After completion of the addition of n-butyl chloride, the reaction mass was held at 65 °C for 8 hours. The yield of n-butyllithium was 94.6%.

[0057] Example 10 (according to the present invention)

[0058] The preparation of n-butyllithium was carried out similar to Example 9, except that the molar ratio of lithium to n-butyl chloride was 4.5:1. The yield of n-butyllithium was 99.2%.

[0059] Example 11 (comparative)

[0060] 300 g of lithium and 2 kg of petroleum solvent (P1 63 / 75) were added to a 5 L reactor. The lithium was used in the form of a block with a specific surface area of 6.3 cm 2 / g determined by a calculation method. The reactor contents were heated to 60 °C, and then 150 rpm (corresponding to ε of 0.006 m 2 / s 3While stirring, 1 kg of n-butyl chloride was added such that the reaction temperature did not exceed 70 °C. The molar ratio of lithium to n-butyl chloride was 4:1. After the addition of n-butyl chloride was completed, the reaction mixture was maintained at 65 °C for 8 hours. The yield of n-butyllithium was 67.8%.

[0061] Example 12 (According to the present invention)

[0062] The preparation of n-butyllithium was carried out similarly to Example 11, except that the stirring speed was 300 rpm (corresponding to 0.05 m 2 / s 3 of ε). The yield of n-butyllithium was 90.3%.

[0063] Example 13 (According to the present invention)

[0064] The preparation of n-butyllithium was carried out similarly to Example 11, except that the stirring speed was 500 rpm (corresponding to 0.15 m 2 / s 3 of ε). The yield of n-butyllithium was 92.4%.

[0065] Example 14 (According to the present invention)

[0066] 225 g of lithium and 2 kg of petroleum solvent (P1 63 / 75) were added to a 5 L reactor. The lithium was used in the form of a cylinder having dimensions of 6 × 6 mm and a specific surface area of 25.7 cm 2 / g determined by a computational method. The reactor contents were heated to 60 °C and then 1 kg of n-butyl chloride was added over 7 hours while stirring at 150 rpm (corresponding to 0.006 m 2 / s 3 of ε) such that the reaction temperature did not exceed 70 °C. The molar ratio of lithium to n-butyl chloride was 3:1. After the addition of n-butyl chloride was completed, the reaction mixture was maintained at 65 °C for 8 hours. The yield of n-butyllithium was 92.5%.

[0067] Example 15 (According to the present invention)

[0068] The preparation of n-butyllithium was carried out similarly to Example 14, except that the stirring speed was 300 rpm (corresponding to 0.05 m 2 / s 3 of ε). The yield of n-butyllithium was 97.3%.

[0069] Example 16 (According to the present invention)

[0070] The preparation of n-butyllithium was carried out similarly to Example 14, except that the stirring speed was 600 rpm (corresponding to 0.28 m 2 / s3 of ε). The yield of n-butyllithium was 99.3%.

[0071] Example 17 (comparative)

[0072] 225 g of lithium and 2 kg of petroleum solvent (P1 63 / 75) were added to a 5 L reactor. The lithium was used in the form of blocks with a specific surface area of 0.42 cm 2 / g determined by a calculation method. The reactor contents were heated to 60 °C and then 1 kg of n-butyl chloride was added dropwise over 7 hours with stirring at 300 rpm (corresponding to 0.05 m 2 / s 3 of ε) such that the reaction temperature did not exceed 70 °C. The molar ratio of lithium to n-butyl chloride was 3:1. After completion of the addition of n-butyl chloride, the reaction mass was held at 65 °C for 8 hours. The yield of n-butyllithium was 61.3%.

[0073] Example 18 (comparative)

[0074] The preparation of n-butyllithium was carried out analogously to Example 17, except that the stirring speed was 800 rpm (corresponding to 0.6 m 2 / s 3 of ε). The yield of n-butyllithium was 63%.

[0075] Example 19 (according to the invention)

[0076] 300 g of lithium and 2 kg of petroleum solvent (P1 63 / 75) were added to a 5 L reactor. The lithium was used in the form of strips (0.4 × 25 × 80 mm) with a specific surface area of 96.3 cm 2 / g determined by a calculation method. The reactor contents were heated to 60 °C and then 1 kg of n-butyl chloride was added dropwise over 7 hours with stirring at 300 rpm (corresponding to 0.05 m 2 / s 3 of ε) such that the reaction temperature did not exceed 70 °C. The molar ratio of lithium to n-butyl chloride was 4:1. After completion of the addition of n-butyl chloride, the reaction mass was held at 65 °C for 8 hours. The yield of n-butyllithium was 99.2%.

Claims

1. A method for producing alkyllithium, the method comprising reacting lithium metal having a specific surface area of 1 to 100 cm 2 / g with an alkyl halide in an organic solvent medium under high turbulence conditions, wherein the molar ratio of lithium metal to alkyl halide is from 2.5:1 to 5.5:

1.

2. The method according to claim 1, characterized in that, The lithium metal used has a specific surface area of 5 to 70 cm 2 / g, preferably 10 to 30 cm 2 / g.

3. The method according to claim 1 or 2, characterized in that, the alkyl halide used is alkyl chloride, alkyl bromide or alkyl iodide, preferably alkyl chloride.

4. The method according to claim 3, characterized in that, the alkyl chloride used is methyl chloride, ethyl chloride, n-propyl chloride, n-butyl chloride, sec-butyl chloride, tert-butyl chloride or n-hexyl chloride, preferably n-butyl chloride, sec-butyl chloride or tert-butyl chloride.

5. The method according to any one of claims 1 to 4, characterized in that, The reaction of lithium metal with alkyl halide is carried out at a turbulent energy dissipation rate (ε) of 0.01 to 0.3 m 2 / s 3 , preferably 0.02 to 0.2 m 2 / s 3 , more preferably 0.03 to 0.1 m 2 / s 3 .

6. The method according to any one of claims 1 to 5, characterized in that, the molar ratio of lithium metal to alkyl halide is from 2.5:1 to 5.5:1, preferably from 3:1 to 4.5:

1.

7. The method according to any one of claims 1 to 6, characterized in that, the organic solvent used is a C5-C7 alkane, such as n-hexane, n-heptane; a cycloalkane, such as cyclohexane; or a mixture of various proportions thereof, such as nefras (petroleum solvent) and petroleum ether.

8. The method according to claim 7, characterized in that, the organic solvent used is hexane, cyclohexane or nefras, preferably hexane and nefras.

9. The method according to any one of claims 1 to 8, characterized in that, the synthesis of alkyl lithium by adding an alkyl halide to lithium metal in an organic solvent is carried out at a temperature not exceeding 75 °C, preferably 50 to 73 °C, more preferably 60 to 70 °C.