A method for preparing prenol

Abstract

The present application relates to the technical field of organic synthesis, in particular to a preparation method of isopentenol, and further to a method for preparing 3-methyl-2-buten-1-ol from 2-methyl-3-buten-2-ol as raw material. In the method, the hydroxyl group in methylbutenol is replaced by chlorination to generate 3-chloroisopentenol, and then isomerization is performed to obtain a mixture containing 1-chloroisopentenol, and the mixture containing 1-chloroisopentenol is hydrolyzed to obtain isopentenol. In the method, methylbutenol is converted into isopentenol through a simple process, the overall yield is more than 95%, and no expensive catalyst is needed; the whole process is simple to operate and easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a method for preparing isopentenol, and more specifically, to a method for preparing 3-methyl-2-buten-1-ol from 2-methyl-3-buten-2-ol as a raw material. Background Technology

[0002] Isopentenol is mainly used in the reaction with trimethyl orthoacetate to synthesize methyl benzoate, and is an important raw material for the preparation of dichloroquine, a key intermediate in the production of pyrethroids. The main methods for synthesizing isopentenol include the acetone method, the isobutylene method, and the isoprene method. The acetone method uses acetylene as a raw material, which is costly, has a long process route, low product yield, and requires catalytic hydrogenation with precious metal catalysts, resulting in high production costs. The acetone method for synthesizing isopentenol has been gradually phased out industrially. The isobutylene method uses formaldehyde and isobutylene as raw materials, generating 3-methyl-3-buten-1-ol through the Prince reaction, followed by catalytic isomerization to obtain isopentenol. This method requires the synthesis of 3-methyl-3-buten-1-ol under high temperature and high pressure conditions, which are very demanding, requiring sophisticated equipment and posing certain safety risks.

[0003] The isoprene method uses isoprene and hydrogen chloride as raw materials to obtain 1-chloro-3-methyl-2-butene (1-chloroisopentene) and 3-chloro-3-methyl-1-butene (3-chloroisopentene). The chloroisopentene is then hydrolyzed to produce 3-methyl-2-buten-1-ol (isopentenol) and 2-methyl-3-buten-2-ol (methylbutenol). Because the two alcohols have significantly different boiling points, they can be separated in a distillation column using only a few theoretical plates. Even after isomerization, the chloroproduct 1-chloroisopentene still contains approximately 10% of the non-target product 3-chloroisopentene, and the two chloroproducts are difficult to separate, resulting in a high yield of methylbutenol as a byproduct, while the isoprene alcohol yield is only around 85%. However, this method has mild reaction conditions and low equipment requirements. If the process can be improved to increase the yield, isoprene alcohol synthesized via this route will have greater market competitiveness.

[0004] In 2020, BASF disclosed a patent for the synthesis of isopentenol from methylbutenol via isomerization, using a platinum catalyst supported on alumina. The conversion rate of methylbutenol was about 45%, and the catalyst cost was relatively high. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 3-methyl-2-buten-1-ol from 2-methyl-3-buten-2-ol as a raw material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing isopentenol involves using methylbutenol as a raw material, chlorinating and substituting the hydroxyl group in methylbutenol to generate 3-chloroisopentene, then isomerizing it to obtain a mixture containing 1-chloroisopentene, and hydrolyzing the mixture containing 1-chloroisopentene to obtain isopentenol.

[0008] Specifically:

[0009] (1) Mix methylbutenol and catalyst A, heat to 30-80℃ and slowly add thionyl chloride dropwise. After the dropwise addition is complete, keep the temperature at the dropwise temperature for 2-3 hours. Then distill at atmospheric pressure to 105-110℃ to obtain 3-chloroisopentene.

[0010] (2) Add catalyst B to the 3-chloroisopentene obtained above, and carry out the isomerization reaction at a temperature of 5-30℃ for 5-7 hours. Filter to obtain a mixture of 1-chloroisopentene (85%-90%) and 3-chloroisopentene (10%-15%).

[0011] The reaction equation is as follows:

[0012]

[0013] (3) Mix the mixture obtained in step (2), the inorganic alkaline aqueous solution and the solvent, heat to 40-80℃ and keep warm for 2-5 hours for hydrolysis; after the reaction, collect the oil layer in layers, remove the solvent through a distillation tower, and then separate the product isopentenol by negative pressure distillation.

[0014] The catalyst A is N,N-dimethylformamide, and its addition amount is 0.01%-0.5% of the weight of methylbutenol, preferably 0.04-0.06%; the molar ratio of methylbutenol to thionyl chloride is 1:1.1-1.5, preferably 1:1.1-1.4.

[0015] The temperature is raised to 55℃-65℃ and thionyl chloride is slowly added dropwise; the molar ratio of methylbutenol to thionyl chloride is 1:1.2; the amount of N,N-dimethylformamide added is 0.04-0.06% of the weight of methylbutenol.

[0016] Catalyst B is the main catalyst and co-catalyst. The main catalyst is a metal chloride, and its addition amount is 0.1%-1% of the weight of 3-chloroisoprene. The co-catalyst is selected from one or more of water, methanol, ethanol, ethylene glycol, formaldehyde and acetic acid, and its addition amount is 0.01%-0.5% of the weight of 3-chloroisoprene.

[0017] The isomerization temperature is 15-20℃; the main catalyst is selected from stannous chloride, cuprous chloride or titanyl chloride, and the amount of the main catalyst added is 0.4-0.6% of the weight of 3-chloroisoprene; the amount of the co-catalyst added is 0.02-0.03% of the weight of 3-chloroisoprene.

[0018] The inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; the molar ratio of methylbutenol to the inorganic base is 1:1.1-5; the solvent is selected from one or more of benzene, toluene, n-hexane, cyclohexane, and heptane.

[0019] The molar ratio of methylbutenol to inorganic base is 1:1.4-2.3.

[0020] The layered oil is collected and the solvent is removed by a distillation column at atmospheric pressure and a bottom temperature of 125℃-130℃. Then, methylbutenol and isopentenol are separated by negative pressure distillation at an absolute pressure of 45-50 mmHg. The distillation temperature of methylbutenol is 80℃-90℃, and the distillation temperature of isopentenol is 90℃-100℃. The collected methylbutenol is recycled to step (1) for chlorination.

[0021] After the reaction in step (2), the catalyst is filtered and separated for recycling; after the hydrolysis reaction in step (3), the solvent is collected in layers for recycling.

[0022] Advantages of this invention:

[0023] This invention prepares isopentenol from methylbutenol via chlorination, isomerization, and hydrolysis, avoiding the low conversion rate of direct conversion of methylbutenol to isopentenol. Furthermore, the raw materials can be reused during the reaction, resulting in an overall yield exceeding 95%. This invention features a simple process that eliminates the need for expensive catalysts and is easily industrialized. Detailed Implementation

[0024] The following examples further illustrate specific embodiments of the present invention. It should be noted that the specific embodiments described herein are merely for illustration and explanation and are not intended to limit the scope of the present invention.

[0025] This invention prepares isopentenol from methylbutenol. First, 3-chloroisopentene is generated by chlorination of the hydroxyl group in methylbutenol. Then, the 3-chloroisopentene is isomerizes to obtain 1-chloroisopentene. Finally, the 1-chloroisopentene is hydrolyzed to obtain isopentenol. Because methylbutenol can be recycled in the reaction, the overall yield of this method can reach over 95%.

[0026] Example 1:

[0027] (1) In a 500 mL four-necked glass flask equipped with a thermometer and a stirrer, 86.1 g (1.0 mol) of methylbutenol (2-methyl-3-buten-2-ol) and 0.043 g (0.00059 mol) of N,N-dimethylformamide were added. The temperature was raised to 55℃-60℃, and 129.3 g (1.2 mol) of thionyl chloride was slowly added dropwise over 2 hours. After the addition was completed, the temperature was maintained for another 2 hours. Then, the mixture was distilled at atmospheric pressure to 105-110℃ to obtain 102.8 g of 3-chloroisoprene with a purity of 99.2%.

[0028] (2) In a 250 mL four-necked glass flask equipped with a thermometer and a stirrer, 102.5 g (0.98 mol) of 3-chloroisopentene, 0.52 g (0.005 mol) of cuprous chloride and 0.03 g (0.0017 mol) of water were added and kept at 15℃-20℃ for 5 h. The cuprous chloride was removed by filtration to obtain a mixture of 1-chloroisopentene and 3-chloroisopentene. Gas chromatography analysis showed that the content of 1-chloroisopentene was 89.2% and the content of 3-chloroisopentene was 9.1%.

[0029] (3) In a 500mL four-necked glass flask equipped with a thermometer and a stirrer, add 100.4g (0.96mol) of a mixture of 1-chloroisoprene and 3-chloroisoprene, 100g of toluene, and 200g (1.5mol) of a 30% sodium hydroxide aqueous solution. Heat to 40℃-45℃ and maintain for 2 hours. The mixture separates into layers. The pressure for solvent removal in the oil layer is atmospheric pressure. The tower height is 1m, and the bottom temperature is 125℃-130℃. 81.8g of a mixture of isopentenol and methylbutenol is collected. Gas chromatography analysis is performed. The mixture contains 90.6% isopentenol and 8.5% methylbutenol. The absolute pressure of the mixture during negative pressure distillation is 45-50 mmHg. It is collected at 80-90℃, yielding 6.9g of methylbutenol with a purity of 98.5%. It is collected at 90-100℃, yielding 74.1g of isopentenol (3-methyl-2-buten-1-ol) with a purity of 99.1%, resulting in a yield of 86.1%. This yield is a single-step yield. The collected methylbutenol can be used as a raw material to obtain isopentenol through chlorination, isomerization, and hydrolysis.

[0030] Examples 2-5

[0031] The operation process was similar to that in Example 1, except that the co-catalyst in catalyst B was adjusted. The results are shown in Table 1 below:

[0032] Table 1

[0033]

[0034] Table 1 shows that different co-catalysts have different isomerization effects on 1-chloroisoprene, and the corresponding isopentenol yields also vary. Formaldehyde has a better isomerization effect and a higher yield; however, different co-catalysts have no significant effect on the isopentenol content.

[0035] Examples 6-10

[0036] The operation process was similar to that in Example 1, except that the methylbutenol obtained from the distillation in Example 1 was carried over to the chlorination process in Example 6 in one step. The results are shown in Table 2 below:

[0037] Table 2

[0038]

[0039] As can be seen from Table 2, the methylbutenol obtained by distillation was reused multiple times, and the yield was above 95%, and the content of isopentenol was greater than 99%.

[0040] Example 11

[0041] To verify the industrial feasibility of the present invention, synthesis was carried out using a 30L glass reactor in the laboratory.

[0042] (1) In a 30L glass autoclave, 8.6kg (100mol) of methylbutenol (2-methyl-3-buten-2-ol) and 4.3g (0.059mol) of N,N-dimethylformamide were added. The temperature was raised to 55℃-60℃, and 12.9kg (120mol) of thionyl chloride was slowly added dropwise over 2 hours. After the addition was completed, the temperature was maintained for another 2 hours. Then, the autoclave was distilled at atmospheric pressure to 105-110℃ to obtain 10.4kg of 3-chloroisoprene with a purity of 99.2%.

[0043] (2) In a 30L glass autoclave, 10.4kg (99mol) of 3-chloroisopentene, 52g (0.5mol) of cuprous chloride and 3.0g (0.17mol) of water were added and kept at 15℃-20℃ for 5h. The cuprous chloride was removed by filtration to obtain a mixture of 1-chloroisopentene and 3-chloroisopentene. Gas chromatography analysis showed that the content of 1-chloroisopentene was 89.8% and the content of 3-chloroisopentene was 8.3%.

[0044] (3) In a 30L glass reactor, add 5 kg (48 mol) of a mixture of 1-chloroisoprene and 3-chloroisoprene, 5 kg of toluene, and 10 kg (75 mol) of a 30% sodium hydroxide aqueous solution. Heat to 40℃-45℃ and maintain for 2 hours. The mixture separates into layers. The pressure for solvent removal on the oil layer in the tower is atmospheric pressure. The tower height is 1 m, and the tower bottom temperature is 125℃-130℃. Collect 4.0 kg of a mixture of isopentenol and methylbutenol. Perform gas chromatography. Analysis showed that the isopentenol content was 90.2% and the methylbutenol content was 8.3%. The mixture was subjected to negative pressure distillation at an absolute pressure of 45-50 mmHg. Distillation was carried out at 80-90℃, yielding 325g of methylbutenol with a purity of 98.8%. Distillation was carried out at 90-100℃, yielding 3.6kg of isopentenol (3-methyl-2-buten-1-ol) with a purity of 99.2% and a yield of 87.0%. After scale-up, the normalized isopentenol content was greater than 99%.

Claims

1. A method for preparing isopentenol, characterized in that: Using methylbutenol as a raw material, 3-chloroisopentene is generated by chlorination to replace the hydroxyl group in methylbutenol, and then isomerization is carried out to obtain a mixture containing 1-chloroisopentene. The mixture containing 1-chloroisopentene is then hydrolyzed to obtain isopentenol. Specifically: (1) Mix methylbutenol and catalyst A, heat to 30℃-80℃ and slowly add thionyl chloride dropwise. After the addition is complete, keep warm at the addition temperature for 2h-3h. Then distill at atmospheric pressure to 105℃-110℃ to obtain 3-chloroisopentene. (2) Add catalyst B to the 3-chloroisopentene obtained above, and carry out the isomerization reaction at a temperature of 5℃-30℃ for 5h-7h. Filter to obtain a mixture of 1-chloroisopentene and 3-chloroisopentene. (3) Mix the mixture obtained in step (2), the inorganic alkaline aqueous solution and the solvent, heat to 40℃-80℃ and keep warm for 2h-5h for hydrolysis; after the reaction, collect the oil layer in layers, remove the solvent through a distillation tower, and then separate the product isopentenol by negative pressure distillation. The catalyst A is N,N-dimethylformamide, and its addition amount is 0.01%-0.5% of the weight of methylbutenol; the molar ratio of methylbutenol to thionyl chloride is 1:1.1-1.5; Catalyst B is the main catalyst and co-catalyst. The main catalyst is selected from stannous chloride, cuprous chloride or titanyl chloride, and its addition amount is 0.1%-1% of the weight of 3-chloroisoprene. The co-catalyst is selected from one or more of water, methanol, ethanol, ethylene glycol, formaldehyde and acetic acid, and its addition amount is 0.01%-0.5% of the weight of 3-chloroisoprene.

2. The method for preparing isopentenol according to claim 1, characterized in that: Heat the mixture to 55℃-65℃ and slowly add thionyl chloride dropwise; the molar ratio of methylbutenol to thionyl chloride is 1:1.2; the amount of N,N-dimethylformamide added is 0.04%-0.06% of the weight of methylbutenol.

3. The method for preparing isopentenol according to claim 1, characterized in that: The isomerization temperature is 15℃-20℃; the amount of main catalyst added is 0.4%-0.6% of the weight of 3-chloroisoprene; and the amount of co-catalyst added is 0.02%-0.03% of the weight of 3-chloroisoprene.

4. The method for preparing isopentenol according to claim 1, characterized in that: The inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; the molar ratio of methylbutenol to the inorganic base is 1:1.1-5; the solvent is selected from one or more of benzene, toluene, n-hexane, cyclohexane, and heptane.

5. The method for preparing isopentenol according to claim 4, characterized in that: The molar ratio of methylbutenol to inorganic base is 1:1.4-2.

3.

6. The method for preparing isopentenol according to claim 1, characterized in that: The layered oil is collected and the solvent is removed by a distillation column at atmospheric pressure and a bottom temperature of 125℃-130℃. Then, methylbutenol and isopentenol are separated by negative pressure distillation at an absolute pressure of 45mmHg-50mmHg. The distillation temperature of methylbutenol is 80℃-90℃, and the distillation temperature of isopentenol is 90℃-100℃. The collected methylbutenol is recycled to step (1) for chlorination.

7. The method for preparing isopentenol according to claim 1, characterized in that: After the reaction in step (2), the catalyst is filtered and separated for recycling; after the hydrolysis reaction in step (3), the solvent is collected in layers for recycling.

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