Method for preparing 2, 5-dimethyl-2, 5-hexanediol

Abstract

The invention discloses a method for preparing 2, 5-dimethyl-2, 5-hexanediol, which comprises the following steps: taking 2, 5-dimethylhexane and chlorine as raw materials, carrying out substitution reaction under the illumination of an acid-binding agent and ultraviolet rays, and then reacting with sodium hydroxide to obtain the 2, 5-dimethyl-2, 5-hexanediol. The method is short in reaction period and high in reaction efficiency, the obtained 2, 5-dimethyl-2, 5-hexanediol is stable in quality, the problems that in a traditional process, consumed time is long, production efficiency is low, reaction safety is poor, and the amount of waste water is large are solved, and a new thought is provided for industrial production of 2, 5-dimethyl-2, 5-hexanediol.

Description

Technical Field

[0001] The present invention relates to a method for preparing 2,5-dimethyl-2,5-hexanediol, belonging to the technical field of compound preparation. Background Art

[0002] 2,5-Dimethyl-2,5-hexanediol (abbreviated as DHAG) is a vicinal diol, and is one of the chemical raw materials for a variety of organic syntheses. It is mainly used for preparing pyrethroids, spices, artificial musks, organic peroxides, cross-linking agents for polyethylene plastics, rubber bis(2,5-dimethyl-2,5-hexanediol) vulcanizing agents. It is also the main raw material for the intermediate 2,5-dimethyl-2,4-hexadiene of pharmaceutical fine chemicals, and is an important and widely used fine chemical.

[0003] Currently, in industrial production, acetylene and acetone are mostly used as synthesis raw materials. Usually, 2,5-dimethyl-3-hexyne-2,5-diol (DHYG) is obtained by atmospheric pressure alkynylation or pressure alkynylation, and then 2,5-dimethyl-2,5-hexanediol is obtained through a hydrogenation reaction.

[0004] Among them, patent document CN103910606A discloses a method for producing 2,5-dimethyl-2,5-hexanediol by an alkynylation condensation method. The method includes the following steps: ① preparing a feed liquid containing hexynediol from acetylene and acetone; ② separating in a potassium hydroxide separation kettle; ③ sending an aqueous potassium hydroxide solution into a nickel alloy continuous evaporator to distill and concentrate the aqueous potassium hydroxide solution; ④ sending the concentrated potassium hydroxide solution into an inorganic impurity separation device to remove organic impurities; ⑤ sending the potassium hydroxide aqueous solution after impurity removal into a cast iron evaporator to evaporate the water to become solid potassium hydroxide; then continuously heating to make the solid potassium hydroxide in a molten state, and then naturally cooling to make it recrystallize; ⑦ using a slicing machine to slice the recrystallized potassium hydroxide as a catalyst raw material for recycling.

[0005] Patent document CN1247181A discloses a one-step synthesis method for 2,5-dimethyl-2,5-hexanediol. The synthesis method includes acetylene and acetone being synthesized into 2,5-dimethyl-3-ethynyl-2,5-diol in an o-xylene solution with potassium isobutoxide as a catalyst under atmospheric pressure, and after hydrolysis, neutralization, concentration, crystallization and centrifugal separation, in a medium (high) pressure reaction kettle, using Raney nickel as a catalyst, hydrogenation is carried out at a pressure of 0 - 5.5 MPa to obtain 2,5-dimethyl-2,5-hexanediol.

[0006] Patent document CN101234950A discloses a new process for producing 2,5-dimethyl-2,5-hexanediol by extraction and vacuum distillation. It uses acetylene and acetone to condense with potassium hydroxide in benzene solvent, then neutralizes with hydrochloric acid to obtain a feed liquid containing hexynediol, oil phase and benzene, conducts catalytic hydrogenation reaction through two concentration and extraction operations, and then conducts two vacuum distillations on the reaction product to obtain the target product.

[0007] Patent document CN115894172A discloses a continuous production system and method for 2,5-dimethyl-2,5-hexanediol. The synthesis process includes an alkynylation reaction system, a solvent separation system, a hydrogenation reaction system and an evaporation and purification system connected in sequence. Through the above four reaction systems, high-quality 2,5-dimethyl-2,5-hexanediol can be efficiently and continuously produced.

[0008] In summary, the traditional synthesis method of 2,5-dimethyl-2,5-hexanediol often uses alkynylation and hydrogenation for the reaction. This reaction process not only takes a long time, has low production efficiency, but also the quality of the obtained product is unstable. At the same time, there are many problems such as poor reaction safety and large amount of waste water. Summary of the Invention

[0009] Aiming at the deficiencies of the existing technology, the present invention provides a method for preparing 2,5-dimethyl-2,5-hexanediol. This method uses 2,5-dimethylhexane and chlorine as raw materials, undergoes a substitution reaction under an acid-binding agent and ultraviolet light irradiation, and then reacts with sodium hydroxide to obtain 2,5-dimethyl-2,5-hexanediol. The method of the present invention has a short reaction cycle, high reaction efficiency, and the obtained 2,5-dimethyl-2,5-hexanediol has stable quality, overcoming the problems of long time consumption, low production efficiency, poor reaction safety, large amount of waste water, etc. in the traditional process, and providing a new idea for the industrial production of 2,5-dimethyl-2,5-hexanediol.

[0010] The specific technical solution of the present invention is as follows:

[0011] A method for preparing 2,5-dimethyl-2,5-hexanediol, which includes the following steps:

[0012] 1) Carry out a substitution reaction on 2,5-dimethylhexane and chlorine under an acid-binding agent and ultraviolet light irradiation;

[0013] 2) Add a sodium hydroxide solution to the reaction product of step 1) for reaction;

[0014] 3) Add the reaction solution of step 2) to an organic solvent for extraction, and remove the solvent from the obtained organic phase to obtain 2,5-dimethyl-2,5-hexanediol.

[0015] Further, in step 1), the acid-binding agent is a nitrogen-containing organic base. On the one hand, the organic base acts as a catalyst to activate the tertiary hydrogen on the isopropyl group, promote the departure of hydrogen, and improve the reactivity of the tertiary hydrogen. On the other hand, it can capture the by-product hydrogen chloride and promote the forward reaction. Exemplarily, the organic base can be at least one of triethylamine, pyridine, hexamethylenetetramine, etc.

[0016] Further, in step 1), when the acid-binding agent is triethylamine, the product yield is higher and the operability is stronger.

[0017] Further, in step 1), the molar ratio of 2,5-dimethylhexane to the nitrogen in the organic base is 1:(2 - 2.2).

[0018] Further, in step 1), the reaction is carried out in a reaction kettle, and chlorine gas is introduced into the reaction kettle in the form of gas. A tail gas absorption device is provided on the reaction kettle. Preferably, 2,5-dimethylhexane and the acid-binding agent are first added into the reaction kettle, and then chlorine gas is continuously introduced into the mixture of 2,5-dimethylhexane and the acid-binding agent. To ensure sufficient contact between chlorine gas and 2,5-dimethylhexane and the acid-binding agent, chlorine gas is preferably introduced from the bottom of the reaction kettle. During the whole reaction process, chlorine gas is continuously introduced into the reaction kettle, and the pressure of chlorine gas in the system is ≤0.1 Mpa.

[0019] Further, in step 1), the wavelength of the ultraviolet light emitted by the ultraviolet lamp is preferably 350 - 365 nm.

[0020] Further, in step 1), the reaction temperature is 0°C - 20°C, such as 0°C, 5°C, 10°C, 15°C, 20°C.

[0021] Further, in step 1), the introduction of chlorine gas can be stopped when 2,5-dimethylhexane is completely converted. In actual production, the content of 2,5-dimethylhexane can be detected, and when its content in the system is less than 1%, the reaction can be considered complete; or the weight gain of the system can be detected, and when the weight gain of the system is 50% and above of the added mass of 2,5-dimethylhexane, the reaction can be considered complete. Generally, within this reaction temperature range, the reaction time is 2.5 - 5 h.

[0022] Further, in step 2), the sodium hydroxide solution is a dilute solution, for example, the concentration can be 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, and preferably 20 - 35 wt%.

[0023] Further, in step 2), the sodium hydroxide solution is preferably added dropwise.

[0024] Further, in step 2), the molar ratio of sodium hydroxide to 2,5-dimethylhexane is (2 - 2.4):1.

[0025] Further, in step 2), the reaction temperature is 40°C to 55°C, such as 40°C, 45°C, 50°C, 55°C. Within this temperature range, the reaction time is generally 30 min to 2 h, such as 30 min, 1 h, 1.5 h, 2 h.

[0026] Further, in step 3), the organic solvent is ether, dichloromethane or chloroform. The mass ratio of the organic solvent to 2,5-dimethylhexane is (1 - 2.5):1.

[0027] Further, in step 3), after extraction, the organic phase is obtained by liquid separation, and the organic solvent is removed from the organic phase by vacuum distillation or atmospheric distillation.

[0028] The present invention has the following beneficial effects:

[0029] (1) The present invention provides a new reaction route for the synthesis of 2,5-dimethyl-2,5-hexanediol. Compared with the traditional synthesis method, the conversion rate of the present invention is higher, and the quality of the target product obtained is better.

[0030] (2) The present invention uses a nitrogen-containing organic base as the catalyst and acid-binding agent in the first-step reaction. On the one hand, the organic base can activate the tertiary hydrogen on the methyl group in 2,5-dimethylhexane, promote the departure of hydrogen ions, and improve the reaction activity; on the other hand, the organic base can act as an acid-binding agent to capture the hydrogen chloride generated in the reaction, promote the forward reaction of the reaction, and make the reaction more complete. The presence of the organic base not only improves the reaction efficiency but also improves the reaction yield.

[0031] (3) The present invention uses an aqueous sodium hydroxide solution as the raw material in the second-step reaction. The reaction temperature is low, the conditions are mild, the reaction time is short, and the synthesis efficiency is high.

[0032] (4) The present invention has high raw material utilization rate, few side reactions, little waste water, and high reaction safety.

[0033] (5) The product obtained by the present invention is a white solid, the product purity ≥ 99%, the yield ≥ 92.3%, the quality is good, meets the use requirements, and has industrial application value. Specific embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Unless otherwise specified, the concentrations hereinafter are all mass percentages.

[0036] In the following Examples and Comparative Examples, the calculation formula for the product yield is as follows:

[0037]

[0038] Example 1

[0039] A new method for preparing 2,5-dimethyl-2,5-hexanediol, and the reaction equation is as follows:

[0040]

[0041] The reaction includes the following steps:

[0042] (1) Put 100 g of 2,5-dimethylhexane and 186.03 g of triethylamine into a dry and clean reaction kettle, lower the temperature of the reaction kettle to 10 °C, slowly introduce chlorine gas into the bottom of the reaction kettle under ultraviolet light irradiation with a wavelength of 350 - 365 nm, and continuously stir, while maintaining the temperature of the reaction system at 10 °C - 15 °C and the pressure at ≤0.1 Mpa. The reaction kettle is connected to a tail gas absorption device to absorb the overflowing chlorine gas. Continuously introduce chlorine gas into the reaction kettle. After reacting for 3.5 h, the total mass of the reaction materials in the reaction kettle increases by 50 g. Stop introducing chlorine gas, and the reaction is completed to obtain a mixed solution A.

[0043] (2) Heat the obtained mixed solution A to 40 °C, then add dropwise 256.79 g of an aqueous sodium hydroxide solution with a mass fraction of 30%, and react at 45 °C - 50 °C for 1 h to obtain a mixed solution B;

[0044] (3) Mix the obtained mixed solution B with 150 g of dichloromethane, then let it stand for liquid separation. The obtained organic phase is distilled to remove dichloromethane at 40 °C to obtain 120.63 g of the final 2,5-dimethyl-2,5-hexanediol product.

[0045] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol is 99.57%, the yield (calculated based on 2,5-dimethylhexane) is 93.8%, and the appearance is a white powdery solid.

[0046] Example 2

[0047] Prepare 2,5-dimethyl-2,5-hexanediol according to the method of Example 1, except that in step (1), 186.03 g of triethylamine is replaced by 145.42 g of pyridine.

[0048] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 99.45%, the yield (calculated based on 2,5-dimethylhexane) was 93.4%, and the appearance was a white powdery solid.

[0049] Example 3

[0050] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (1), 186.03 g of triethylamine was replaced with 63.81 g of hexamethylenetetramine.

[0051] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 99.51%, the yield (calculated based on 2,5-dimethylhexane) was 92.8%, and the appearance was a white powdery solid.

[0052] Example 4

[0053] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (1), the reaction temperature was 5°C to 10°C.

[0054] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 99.36%, the yield (calculated based on 2,5-dimethylhexane) was 92.3%, and the appearance was a white powdery solid.

[0055] Example 5

[0056] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (1), 186.03 g of triethylamine was replaced with 194.89 g of triethylamine.

[0057] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 99.60%, the yield (calculated based on 2,5-dimethylhexane) was 93.2%, and the appearance was a white powdery solid.

[0058] Example 6

[0059] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (2), “react at 45°C to 50°C for 1 h” was replaced with “react at 50°C to 55°C for 1 h”.

[0060] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 99.42%, the yield (calculated based on 2,5-dimethylhexane) was 93.0%, and the appearance was a white powdery solid.

[0061] Example 7

[0062] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (2), 256.79 g of an aqueous sodium hydroxide solution with a mass fraction of 30% was replaced by 385.19 g of an aqueous sodium hydroxide solution with a mass fraction of 20%.

[0063] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 99.21%, the yield (calculated based on 2,5-dimethylhexane) was 92.6%, and the appearance was a white powdery solid.

[0064] Comparative Example 1

[0065] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (1), "the temperature of the reaction kettle was lowered to 10 °C, and chlorine gas was slowly introduced into the bottom of the reaction kettle under ultraviolet light irradiation with a wavelength of 350 - 365 nm and continuously stirred, and the temperature of the reaction system was maintained at 10 °C - 15 °C and the pressure ≤ 0.1 Mpa." was replaced by "at room temperature, chlorine gas was slowly introduced into the bottom of the reaction kettle under ultraviolet light irradiation with a wavelength of 350 - 365 nm and continuously stirred, and the temperature of the reaction system was maintained at 25 °C - 30 °C and the pressure ≤ 0.1 Mpa."; other steps and conditions were the same as in Example 1.

[0066] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 92.77%, the yield (calculated based on 2,5-dimethylhexane) was 84.8%, and the appearance was a white powdery solid.

[0067] Comparative Example 2

[0068] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (1), "continuously introduce chlorine gas into the reaction kettle, after reacting for 3.5 h, the total mass of the reaction materials in the reaction kettle increased by 50 g, and stop introducing chlorine gas" was replaced by "continuously introduce chlorine gas into the reaction kettle, after reacting for 2 h, the total mass of the reaction materials in the reaction kettle increased by 30 g, and stop introducing chlorine gas.

[0069] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 91.58%, the yield (calculated based on 2,5-dimethylhexane) was 81.2%, and the appearance was a white powdery solid.

[0070] Comparative Example 3

[0071] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (1), triethylamine was not added.

[0072] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 89.34%, the yield (calculated based on 2,5-dimethylhexane) was 70.5%, and the appearance was a white powdery solid.

[0073] Comparative Example 4

[0074] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (1), 186.03 g of triethylamine was replaced with 97.43 g of sodium carbonate.

[0075] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 98.84%, the yield (calculated based on 2,5-dimethylhexane) was 82.1%, and the appearance was a white powdery solid.

[0076] Comparative Example 5

[0077] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (2), “heating the obtained mixed solution A to 40°C, and then dropping 256.79 g of a 30% sodium hydroxide aqueous solution into it, and reacting at 45°C - 50°C for 1 h” was replaced with “heating the obtained mixed solution A to room temperature, and then dropping 256.79 g of a 30% sodium hydroxide aqueous solution into it, and reacting at 25°C - 30°C for 1 h”.

[0078] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 98.16%, the yield (calculated based on 2,5-dimethylhexane) was 86.2%, and the appearance was a white powdery solid.

[0079] Comparative Example 6

[0080] 2,5-Dimethyl-2,5-hexanediol was prepared according to the method of Example 1, except that: in step (2), 256.79 g of a 30% sodium hydroxide aqueous solution was replaced with 154.08 g of a 50% sodium hydroxide aqueous solution.

[0081] After detection and measurement, the purity (GC) of the obtained 2,5-dimethyl-2,5-hexanediol was 97.33%, the yield (calculated based on 2,5-dimethylhexane) was 88.3%, and the appearance was a white powdery solid.

[0082] The above examples are only used to help understand the method of the present invention and its core idea. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing 2,5-dimethyl-2,5-hexanediol, characterized in that It includes the following steps: 1) Carry out a substitution reaction on 2,5-dimethylhexane and chlorine gas under the action of an acid-binding agent and ultraviolet light irradiation; 2) Add a sodium hydroxide solution to the reaction product of step 1) for reaction; 3) Add the reaction solution of step 2) to an organic solvent for extraction, and remove the solvent from the obtained organic phase to obtain 2,5-dimethyl-2,5-hexanediol.

2. The method according to claim 1, wherein: In step 1), the acid-binding agent is a nitrogen-containing organic base; preferably, the acid-binding agent is at least one of triethylamine, pyridine, and hexamethylenetetramine.

3. The method according to claim 2, characterized in that: In step 1), the molar ratio of 2,5-dimethylhexane to nitrogen in the organic base is 1:(2-2.2).

4. The method according to claim 1, 2 or 3, characterized in that: In step 1), chlorine gas is continuously introduced into the mixture of 2,5-dimethylhexane and the acid-binding agent, and the pressure of chlorine gas in the system is ≤0.1 Mpa.

5. The method according to claim 1, 2 or 3, characterized in that: In step 1), the wavelength of the ultraviolet light is 350-365 nm.

6. The method according to claim 1, 2 or 3, characterized in that: In step 1), the reaction temperature is 0°C-20°C; preferably, in step 1), when the mass increase of the reaction system is 50% or more of the mass of 2,5-dimethylhexane, stop introducing chlorine gas.

7. The method according to claim 1, characterized in that: In step 2), the molar ratio of sodium hydroxide to 2,5-dimethylhexane is (2-2.4):

1.

8. The method according to claim 1 or 7, characterized in that: In step 2), the mass fraction of the sodium hydroxide solution is 20%-35%.

9. The method according to claim 1 or 7, characterized in that: In step 2), the reaction temperature is 40°C-55°C, and the reaction time is 30 min-2 h.

10. The method according to claim 1, characterized in that: In step 3), the organic solvent is diethyl ether, dichloromethane or chloroform; preferably, the mass ratio of the organic solvent to 2,5-dimethylhexane is (1-2.5):1.

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