Industrial production method of 2, 5-dimethyl-2, 5-hexanediol

Abstract

The invention discloses an industrial production method of 2, 5-dimethyl-2, 5-hexanediol, which belongs to the technical field of chemical engineering, and comprises the following steps: adding acetylene and acetone as raw materials and a catalyst into a solvent, carrying out ethynylation condensation reaction to prepare hexynediol, and then separating by alkali liquor, neutralizing an organic phase, evaporating and recycling the solvent, washing with water, concentrating, centrifuging and vaporizing to obtain 2, 5-dimethyl-2, 5-hexanediol. The preparation method comprises the following steps: firstly, preparing 2, 5-dimethyl-3-hexyne-2, 5-diol, and finally, preparing 2, 5-dimethyl-3-hexyne-2, 5-diol, and selecting one of cyclohexane, methyl cyclohexane, methyl tert-butyl ether and ethyl tert-butyl ether as a solvent for the ethynylation condensation reaction; according to the method, the problems that the viscosity of a suspension liquid in the ethynylation condensation reaction process in 2, 5-dimethyl-2, 5-diol production is high, reaction heat is not easy to exchange, and the reaction effect is influenced are solved, and the problems that a traditional solvent is toxic to human and pollutes the environment, and safety and environmental protection risks and management cost are high in production are also solved.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to an industrial method for the production of 2,5-dimethyl-2,5-hexanediol. Background Technology

[0002] 2,5-Dimethyl-3-hexyn-2,5-diol, abbreviated as DHAG, is an important chemical raw material.

[0003] The general steps for producing 2,5-dimethyl-3-hexyn-2,5-diol are as follows: using benzene compounds such as benzene, toluene, and xylene as solvents and potassium hydroxide as catalysts, acetylene and acetone undergo an acetylation condensation reaction under normal pressure and a certain temperature to obtain hexyn-diol. Then, the product undergoes alkaline separation, neutralization of the oil phase with inorganic acid, solvent evaporation and recovery, water washing, concentration, centrifugation, and vaporization to finally obtain 2,5-dimethyl-3-hexyn-2,5-diol.

[0004] In the above steps, since benzene, toluene, xylene and other benzene series compounds are used as solvents, there are at least the following disadvantages: (1) In the later stage of the acetylation condensation reaction, the viscosity of the solution in the reactor is very high, which affects the effective exchange of reaction heat by the jacket water; (2) It is difficult to mix the multiphase raw materials and catalysts well. Increasing the amount of solvent is not economical and will increase the risk of benzene series compounds being toxic to humans and polluting the environment; (3) The above benzene series solvents are all toxic substances that are harmful to humans and the environment. The VOC emission standards are extremely high, the critical amount of which constitutes a major hazard source is low, and it is easy to form a major hazard source, which brings difficulties to safety management and environmental supervision. Summary of the Invention

[0005] One of the objectives of this invention is to provide an industrial production method for 2,5-dimethyl-2,5-hexanediol to solve the above-mentioned problems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an industrial production method for 2,5-dimethyl-3-hexyn-2,5-diol, comprising the following steps: adding acetylene and acetone, as well as a catalyst, to a solvent to carry out an acetylation condensation reaction to obtain hexyn-diol; then separating the product with an alkaline solution, neutralizing the organic phase, evaporating and recovering the solvent, washing with water, concentrating, centrifuging, and vaporizing to finally obtain 2,5-dimethyl-3-hexyn-2,5-diol; wherein the solvent for the acetylation condensation reaction is selected from one of cyclohexane, methylcyclohexane, methyl tert-butyl ether, and ethyl tert-butyl ether.

[0007] The inventors of this application, taking into account factors such as the boiling point, water insolubility, availability, economy, and environmental friendliness of solvents for acetylation condensation reactions, and through extensive experiments, selected cyclohexane (boiling point 80.7℃), methylcyclohexane (boiling point 100.9℃), methyl tert-butyl ether (boiling point 55.2℃), and ethyl tert-butyl ether (boiling point 72.8℃) as solvents for acetylation condensation reactions in the production of 2,5-dimethyl-2,5-diol. This solution addresses the problems of high suspension viscosity and poor heat exchange in the acetylation condensation reaction process, which affect the reaction efficiency. It also solves the problems of toxicity to humans and pollution to the environment caused by traditional solvents, as well as the safety and environmental risks and high management costs in production.

[0008] Specifically, regarding the selection of solvent boiling points, a range of approximately 50–105°C is suitable. Boiling points that are too low are detrimental to the reaction, while those that are too high increase solvent recovery costs. For example, the inventors tried using cyclopentane (boiling point 49.3°C), cycloheptane (boiling point 118°C), ethylcyclohexane (boiling point 131.8°C), propylcyclohexane (boiling point 155°C), and propyl tert-butyl ether (boiling point 97.45°C), but none of these met the above requirements, at least in terms of boiling point. Although propyl tert-butyl ether has a boiling point of 97.45°C, which is within this stable range, its price is too high, making large-scale procurement as a solvent difficult and increasing costs for the same consumption. Regarding water insolubility, the inventors found that if the reaction solvent used has excessively high water solubility, it would cause difficulties in separating from the potassium hydroxide solution after hydrolysis. Therefore, they screened for solvents with appropriate water compatibility.

[0009] As a preferred technical solution, the solvent for the acetylation condensation reaction is methylcyclohexane or ethyl tert-butyl ether. Using either of these two solvents can achieve higher conversion and yield, while also being more economical.

[0010] As a preferred technical solution, the acetylation condensation reaction is carried out at atmospheric pressure and a temperature of 30℃ to 55℃.

[0011] As a preferred technical solution, during the acetylation condensation reaction, acetone, acetylene and catalyst are first added to a solvent and stirred thoroughly to obtain a suspension. The weight ratio of acetone to the suspension is 1:8 to 15, and the molar ratio of acetone to acetylene is 1.8 to 2.2.

[0012] As a preferred technical solution, carbon dioxide is used for neutralization of the organic phase.

[0013] As a preferred technical solution, the solvent is evaporated and recovered, and then reused in the acetylation condensation reaction.

[0014] As a preferred technical solution, the catalyst is powdered potassium hydroxide, preferably with a water content of 6wt% to 20wt%.

[0015] Compared with the prior art, the advantages of the present invention are as follows: (1) It solves the problem that the suspension viscosity is high and the heat of reaction is not easy to exchange, which affects the reaction effect in the acetylation condensation reaction process of 2,5-dimethyl-2,5-diol production; (2) It solves the problem of the toxicity to humans and the pollution to the environment caused by benzene series (benzene, toluene, xylene) solvents in the production process of 2,5-dimethyl-2,5-diol; (3) It solves the problems of safety and environmental risks and high management costs in production. Detailed Implementation

[0016] The present invention will be further described below with reference to embodiments. Example

[0017] A suspension was obtained by charging 320 g of methylcyclohexane and 35 g of potassium hydroxide powder (90 wt% purity) into a jacketed reactor equipped with a stirrer. The suspension was then heated to 35 °C and maintained at this temperature during the reaction. 35.6 g of acetone and 7.9 g of acetylene were then added simultaneously over 4 hours. After a 2-hour post-reaction period, the batch was hydrolyzed with 74 g of water. The organic phase was then removed and neutralized with 6 g of citric acid, and 36.1 g of dimethylhexynyl diol was separated with a conversion of 97% (based on acetone) (corresponding to a yield of 83%). The batch remained stirable throughout the reaction (viscosity 17 Pa·s at 35 °C). Example

[0018] A suspension was obtained by charging 320 g of cyclohexane and 35 g of potassium hydroxide powder (90 wt% purity) into a jacketed reactor equipped with a stirrer. The suspension was then heated to 35 °C and maintained at this temperature during the reaction. 35.6 g of acetone and 7.9 g of acetylene were then added simultaneously over 4 hours. After a 2-hour post-reaction period, the batch was hydrolyzed with 74 g of water. The organic phase was then removed and neutralized with 5.8 g of citric acid, and 30.4 g of dimethylhexynyl diol was separated with a conversion of 93% (based on acetone) (corresponding to a 73% yield). The reaction batch became an unstirrable solid (viscosity 26 Pa·s at 35 °C) near the end of the reaction.

[0019] Both cyclohexane and benzene exhibit the phenomenon that the reaction batch becomes an unstirrable solid near the end of the reaction. The reaction can be completed, but the yield is poor. However, cyclohexane and benzene are much less harmful to the environment. Example

[0020] A suspension was prepared by charging 320 g of methyl tert-butyl ether and 35 g of potassium hydroxide powder (90 wt% purity) into a jacketed reactor equipped with a stirrer. The suspension was then heated to 35 °C and maintained at this temperature during the reaction. 35.6 g of acetone and 7.9 g of acetylene were then added simultaneously over 4 hours. After a 2-hour post-reaction period, the batch was hydrolyzed with 74 g of water. After removing the organic phase and neutralizing with 6 g of acid, 34.04 g of dimethylhexynyl diol was separated with a 95% conversion (based on acetone) (corresponding to an 80% yield). The batch remained stirable throughout the reaction (viscosity 16 Pa·s at 35 °C). Example

[0021] A suspension was prepared by charging 320 g of ethyl tert-butyl ether and 35 g of potassium hydroxide powder (90 wt% purity) into a jacketed reactor equipped with a stirrer. The suspension was then heated to 35 °C and maintained at this temperature during the reaction. 35.6 g of acetone and 7.9 g of acetylene were added simultaneously over 4 hours. After a 2-hour post-reaction period, the batch was hydrolyzed with 74 g of water. After removing the organic phase and neutralizing with 6 g of acid, 36 g of dimethylhexynyl diol was separated with a conversion of 98% (based on acetone) (corresponding to a yield of 82%). The batch remained stirable throughout the reaction (viscosity 18 Pa·s at 35 °C).

[0022] The fact that Examples 1 and 4 above do not "become unstirrable solids" indicates that "the batch remains stirable throughout the reaction process". Comparative Example 1: Compared with Example 1 above, this comparative example only replaced the solvent methylcyclohexane used in Example 1 with benzene in equal amounts, and the rest remained unchanged. The result was that 30 grams of dimethylhexynediol was separated with a conversion rate of 93% (based on acetone) (corresponding to a yield of 72%). The reaction batch became an unstirrable solid (viscosity 25 Pa·s at 35°C) at the end of the reaction.

[0023] Comparative Example 2: Compared with Example 1 above, this comparative example only replaced the solvent methylcyclohexane used in Example 1 with cyclopentane in equal amounts, while keeping everything else the same. 28.5 g of dimethylhexynediol was separated with a conversion rate of 91% (based on acetone) (corresponding to a yield of 72%). The reaction batch became an unstirrable solid (viscosity 25 Pa·s at 35°C) at the end of the reaction.

[0024] Comparative Example 3 Compared with Example 1 above, this comparative example only replaced the solvent methylcyclohexane used in Example 1 with cyclopentane in an equal amount, and the rest remained unchanged. The result was that 27.5 g of dimethylhexynediol was separated with a conversion rate of 90% (based on acetone) (corresponding to a yield of 70%).

[0025] Comparative Example 4 Compared with Example 1 above, this comparative example only replaced the solvent methylcyclohexane used in Example 1 with an equal amount of ethylcyclohexane, and all other aspects remained the same. The result was that 27.3 g of dimethylhexynediol was separated with a conversion rate of 91% (based on acetone) (corresponding to a yield of 69%).

[0026] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An industrial method for producing 2,5-dimethyl-3-hexyne-2,5-diol, comprising the steps of: In a solvent, acetylene and acetone, along with a catalyst, are added to undergo an acetylation condensation reaction to obtain hexynediol. The product is then separated by alkaline solution, neutralized with organic phase, recovered by solvent evaporation, washed with water, concentrated, centrifuged, and vaporized to finally obtain 2,5-dimethyl-3-hexyn-2,5-diol. The characteristic feature is that the solvent used in the acetylation condensation reaction is selected from one of cyclohexane, methylcyclohexane, methyl tert-butyl ether, and ethyl tert-butyl ether.

2. The method according to claim 1, characterized in that, The solvent for the acetylation condensation reaction is methylcyclohexane or ethyl tert-butyl ether.

3. The method according to claim 1, characterized in that, The acetylation condensation reaction is carried out at atmospheric pressure and at a temperature of 30°C to 55°C.

4. The method according to claim 1, characterized in that, During the acetylation condensation reaction, acetone, acetylene, and catalyst are first added to a solvent and stirred thoroughly to obtain a suspension. The weight ratio of acetone to the suspension is 1:8 to 15, the molar ratio of acetone to acetylene is 1.8 to 2.2, and the molar ratio of catalyst to acetone is 1.0 to 1.6 to 1.

5. The method according to claim 1, characterized in that, When neutralizing the organic phase, carbon dioxide is used for neutralization.

6. The method according to claim 1, characterized in that, The solvent is evaporated and recovered, and then reused in the acetylation condensation reaction.

7. The method according to claim 1, characterized in that, The catalyst is powdered potassium hydroxide.