A method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde
By using a green synthesis method with bio-based raw materials and DBU catalyst, the problems of low yield, numerous byproducts, and difficulty in catalyst recovery in the production of 4-hydroxy-2-pentanone from the reaction of acetone and acetaldehyde in the existing technology have been solved. This method achieves the production of 4-hydroxy-2-pentanone with high purity and high yield, which is suitable for large-scale industrial application.
Patent Information
- Application Number
- CN202610455856.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-08
- Publication Date
- 2026-07-10
AI Technical Summary
The existing method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde has problems such as low product yield, many by-products, dark product color, strong odor, difficulty in catalyst recovery, and environmental pollution, and does not meet the requirements of green chemical development.
Using bio-based acetone and acetaldehyde as raw materials and DBU as a catalyst, a DBU-H2O catalytic system is formed through molecular sieve dehydration treatment and deionized water pretreatment. The reaction conditions are controlled to carry out aldol condensation reaction, and the catalyst is recycled through two-stage distillation separation and purification.
It improves product yield and purity, reduces production costs, and realizes green and low-cost production of 4-hydroxy-2-pentanone. The catalyst can be reused 5-8 times, which meets the requirements of green chemical development.
Abstract
Description
Technical Field
[0001] This invention relates to the field of fine chemical intermediate synthesis technology, and in particular to a method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde. Background Technology
[0002] 4-Hydroxy-2-pentanone is an important fine chemical intermediate with reactive hydroxyl and carbonyl functional groups. It exhibits high chemical activity, undergoing various reactions including dehydration, oxidation, and substitution. It is widely used in the preparation of bakelite, the synthesis of flavorings and fragrances, the synthesis of pharmaceutical intermediates, and as an organic solvent. Currently, the main industrial method for producing 4-hydroxy-2-pentanone is the aldol condensation reaction of acetone with aldehydes, primarily involving the condensation of acetone with formaldehyde. However, this method has significant technical limitations.
[0003] In existing technologies, the production of 4-hydroxy-2-pentanone by the condensation of acetone and formaldehyde often employs a mixed catalyst of strongly basic anion exchange resin and magnesium hydroxide. This catalyst requires a complex pretreatment process and is prone to deactivation during catalysis, making it difficult to recover and reuse, thus increasing production costs. Simultaneously, formaldehyde, as an electrophile, lacks α-H, requiring a secondary addition side reaction to supplement the carbon source during acetone condensation, leading to an increase in byproducts (such as formaldehyde self-polymerization products and acetone self-polymerization products). The product yield is only around 80%, and the byproducts contribute to the product's dark color and strong odor, making subsequent purification difficult and energy-intensive. Furthermore, some processes use inorganic strong bases (such as sodium hydroxide and potassium hydroxide) as catalysts. While these can promote the aldol condensation reaction, their strong nucleophilicity easily triggers side reactions such as acetaldehyde self-condensation and acetone self-polymerization, further reducing product purity and yield. Moreover, the catalyst is difficult to separate after the reaction, generating large amounts of alkaline waste liquid, polluting the environment and failing to meet the requirements of green chemical development.
[0004] Furthermore, existing technologies have reported the use of organic bases such as triethylamine and diisopropylethylamine as catalysts. However, these catalysts exhibit low catalytic efficiency, long reaction times, and unsatisfactory product yields and purity, making them unsuitable for industrial production. For instance, in the existing patented method for preparing m-trifluoromethylcinnamaldehyde, DBU is used as a catalyst to improve product purity. However, this method targets the condensation reaction of aromatic aldehydes with acetaldehyde, which differs significantly from the aliphatic aldol condensation reaction of acetone and acetaldehyde in terms of mechanism and reaction conditions, making it unsuitable for direct application in the production of 4-hydroxy-2-pentanone. Simultaneously, existing processes primarily utilize petroleum-based feedstocks, which contradicts the current industrial trend towards green, environmentally friendly, and sustainable development. Moreover, the low feedstock recycling rate further increases production costs.
[0005] Therefore, developing a method for producing 4-hydroxy-2-pentanone from acetone by reacting with acetaldehyde under mild reaction conditions, with easily recoverable catalysts, high product yield, high purity, and environmental friendliness, and suitable for large-scale industrial production, has become an urgent technical problem to be solved in this field. Summary of the Invention
[0006] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide a method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde. This method solves the technical pain points of the prior art, such as low product yield, many by-products, dark product color, strong odor, difficulty in catalyst recovery, and environmental pollution, and achieves green, efficient and low-cost production of 4-hydroxy-2-pentanone.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] A method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde includes the following steps:
[0009] (1) Raw material pretreatment: Bio-based acetone and bio-based acetaldehyde were dehydrated by molecular sieves to control the moisture content to ≤0.1%; deionized water was boiled and cooled to remove dissolved carbon dioxide and set aside for later use.
[0010] The raw materials are bio-based acetone and bio-based acetaldehyde, which are derived from the fermentation of biomass such as corn and straw. This meets the requirements of green chemical development and has a purity of ≥99.5%, which can reduce the interference of impurities on the reaction. Molecular sieve dehydration treatment can remove trace amounts of moisture from the raw materials, avoiding excessive moisture from affecting the reaction yield and catalyst activity. Boiling and cooling with deionized water can remove dissolved carbon dioxide in the water, preventing carbon dioxide from reacting with DBU and interfering with the alkaline catalytic effect of DBU.
[0011] (2) Preparation of catalytic system: 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is mixed with the deionized water after step (1) and stirred evenly to form a DBU-H2O catalytic system, wherein the mass ratio of DBU to deionized water is 1:10;
[0012] DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) is a strong non-nucleophilic organic base with a pKa of approximately 13.5 and a pH of 12.8 in a 1% aqueous solution. The lone pair electrons of the two nitrogen atoms (hybridized) in its molecule work synergistically to exert a basic effect, effectively abstracting the α-H atom from acetone to generate an enol anion, thus driving the aldol condensation reaction. Simultaneously, the non-nucleophilic nature of DBU effectively inhibits side reactions such as acetaldehyde self-condensation and acetone self-polymerization, reducing byproduct formation and improving product purity and yield. DBU requires no complex pretreatment and can be used directly. It is readily soluble in the reaction system, exhibits strong stability in a catalytic system with deionized water, and allows for catalyst recycling.
[0013] (3) Aldol condensation reaction: Pretreated bio-based acetone and bio-based acetaldehyde were added to the reaction vessel at a molar ratio of 1.0~1.3:1, and then the catalytic system prepared in step (2) was added, wherein the amount of DBU was 3%~7% of the total mass of acetone and acetaldehyde; stirring was started, and the stirring speed was controlled to react at low temperature first, and then the temperature was increased to react to obtain the reaction solution.
[0014] The molar ratio of acetone to acetaldehyde is controlled at 1.0~1.3:1, preferably 1.2:1, with a slight excess of acetone, which can effectively suppress the self-condensation side reaction of acetaldehyde and improve the conversion rate of acetaldehyde. The amount of DBU is controlled at 3%~7%, preferably 5%. Too little DBU will result in insufficient catalytic activity, slow reaction rate, and low yield, while too much DBU will increase production costs and may trigger a small number of side reactions. The stirring speed is controlled at 120~180 r / min, preferably 150 r / min, which can ensure that the raw materials and catalyst are fully mixed and improve the reaction rate and uniformity. The reaction is first carried out at a low temperature of 0~10℃ for 0.5~1.5h (preferably 1h) to suppress the occurrence of side reactions, and then the temperature is raised to 75~85℃ (the suitable reaction temperature of the DBU catalytic system) and maintained for 4~7h (preferably 5h) to promote the reaction to proceed fully and improve the product yield.
[0015] The reactor is lined with polytetrafluoroethylene, which is resistant to alkaline corrosion and avoids interference from the reactor material on the reaction. The pressure is controlled at atmospheric pressure (0.1MPa) during the reaction, eliminating the need for high-pressure equipment, reducing production costs and operational difficulty. The heating rate is ≤10℃ / h to avoid sudden temperature changes that could lead to uncontrolled reaction or an increase in byproducts.
[0016] The reaction mechanism in this step is as follows: DBU acts as a basic catalyst, its active center abstracts the α-H from the acetone molecule, undergoing a deprotonation reaction to generate a strongly nucleophilic enol anion. At the same time, DBU itself protonates to form The enol anion acts as a nucleophile, attacking the partially positively charged carbonyl carbon in the acetaldehyde molecule, undergoing nucleophilic addition to form a 5-carbon oxygen anion intermediate. The intermediate undergoes proton transfer with water molecules in the reaction system, thus capturing... Protonation is completed, producing 4-hydroxy-2-pentanone; simultaneously, After deprotonation with intermediate Combined, DBU is regenerated, achieving catalyst recycling. The reaction equation is as follows:
[0017] .
[0018] (4) Separation and purification: The reaction solution obtained in step (3) is filtered and centrifuged to remove impurities, and then subjected to two-stage distillation. The first stage is atmospheric distillation, with the temperature controlled at 110~120℃, to recover DBU; the second stage is vacuum distillation, with the vacuum degree controlled at 0.07~0.09MPa and the temperature at 80~85℃, to collect the fraction and obtain the 4-hydroxy-2-pentanone product.
[0019] Vacuum filtration with filter paper pore size of 0.22~0.45μm removes small amounts of insoluble impurities from the reaction solution. Centrifugation at 3000r / min for 10~15min further removes impurities and improves subsequent distillation efficiency. The two-stage distillation design achieves efficient separation of DBU and product while removing unreacted raw materials and trace byproducts: the first stage, atmospheric distillation, recovers DBU (DBU has a boiling point of approximately 195℃; at atmospheric pressure (110~120℃), DBU and low-boiling-point impurities can be distilled off together, facilitating subsequent purification); the second stage, vacuum distillation, lowers the product's boiling point, preventing product decomposition at high temperatures. By controlling the vacuum level at 0.07~0.09MPa and the temperature at 80~85℃, high-purity 4-hydroxy-2-pentanone product with a purity ≥98.5% can be collected.
[0020] (5) Catalyst recovery: The DBU recovered from the first stage of distillation is purified by vacuum distillation, with the vacuum degree controlled at 0.09MPa and the temperature at 180~190℃, to obtain a reusable DBU catalyst.
[0021] After being purified by vacuum distillation, the recovered DBU can remove trace impurities and restore catalytic activity. After being reused 5 to 8 times, the catalytic activity still remains above 90% of the initial activity, effectively reducing production costs and realizing the green recycling of catalysts.
[0022] Compared with the prior art, the present invention has the following advantages:
[0023] 1. High product yield and purity: This invention uses DBU as a catalyst, whose strong non-nucleophilicity can effectively inhibit side reactions such as acetaldehyde self-condensation and acetone self-polymerization. At the same time, the reaction parameters are optimized to ensure that the reaction proceeds fully. The product yield is ≥85%, the product purity is ≥98.5%, and the product is light in color and odorless. It does not require complicated decolorization and deodorization treatment, which solves the pain points of low product purity, dark color and strong odor in the prior art.
[0024] 2. The catalyst is easy to recover and can be recycled: DBU does not require complicated pretreatment and can be used directly. It can be efficiently recovered through two-stage distillation and can be reused 5 to 8 times after purification. The catalytic activity is stable. Compared with existing mixed catalysts and inorganic strong base catalysts, it significantly reduces the cost of catalysts and reduces waste emissions.
[0025] 3. Mild reaction conditions and simple operation: The reaction is carried out under normal pressure and the temperature is controlled at 75~85℃. No high pressure or high temperature equipment is required. The operation is simple and energy consumption is low. The heating rate is controllable, avoiding reaction runaway. It is safe and suitable for large-scale industrial production.
[0026] 4. Green and environmentally friendly, in line with industry trends: The raw materials are bio-based acetone and bio-based acetaldehyde, which are derived from renewable biomass and replace traditional petroleum-based raw materials, meeting the requirements of green chemical development; no large amount of alkaline waste liquid is generated during the reaction process, the catalyst can be recycled, and the waste emissions are low, which is environmentally friendly; at the same time, unreacted raw materials can be recovered and reused through distillation, further improving the utilization rate of raw materials and reducing production costs.
[0027] 5. Wide applicability: The 4-hydroxy-2-pentanone prepared by this invention has high purity and stable quality, and can be widely used in the preparation of bread ketone, the synthesis of flavors and fragrances, the synthesis of pharmaceutical intermediates, organic solvents and other fields, and has good industrial application prospects. Detailed Implementation
[0028] The present invention will be further described in detail below with reference to specific embodiments.
[0029] Example 1
[0030] A method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde includes the following steps:
[0031] (1) Raw material pretreatment: Take 120g of bio-based acetone with a purity of 99.5% and 58g of bio-based acetaldehyde with a purity of 99.5%, respectively dehydrated by 3A molecular sieve, and control the moisture content ≤0.1%; take 100mL of deionized water, boil and cool it for later use.
[0032] (2) Preparation of the catalytic system: Take 8.9g of DBU and mix it with 89g of deionized water treated in step (1), stir evenly, and form Catalytic system;
[0033] (3) Aldol condensation reaction: Pretreated bio-based acetone and bio-based acetaldehyde were added to a 1000ml polytetrafluoroethylene-lined reactor, and the above catalytic system was added. Stirring was started and the stirring speed was controlled at 150r / min. The reaction was first carried out at 5℃ for 1h, and then the temperature was increased to 80℃ at a heating rate of 8℃ / h. The reaction was maintained for 5h to obtain the reaction solution.
[0034] (4) Separation and purification: The reaction solution was vacuum filtered (filter paper pore size 0.45μm) to remove insoluble impurities, and then centrifuged at 3000r / min for 10min to collect the supernatant; the supernatant was added to a distillation flask, and the first stage was distilled at atmospheric pressure at a temperature of 115℃ to recover DBU; the second stage was distilled under reduced pressure at a vacuum of 0.08MPa and a temperature of 82℃ to collect the fraction and obtain the 4-hydroxy-2-pentanone product;
[0035] (5) Catalyst recovery: The DBU recovered from the first stage of distillation is purified by vacuum distillation, with the vacuum degree controlled at 0.09 MPa and the temperature at 185℃, to obtain a reusable DBU catalyst.
[0036] The purity of the 4-hydroxy-2-pentanone product obtained in this example was 98.8%, and the reaction yield was 86.2%. The purity of the recovered DBU catalyst was 99.2%, and after being reused 5 times, the catalytic activity was still 92.3% of the initial activity.
[0037] Example 2
[0038] A method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde includes the following steps:
[0039] (1) Raw material pretreatment: Take 110g of bio-based acetone with a purity of 99.6% and 58g of bio-based acetaldehyde with a purity of 99.6%, respectively dehydrated by 3A molecular sieve, and control the moisture content ≤0.1%; take 100mL of deionized water, boil and cool it for later use.
[0040] (2) Preparation of catalytic system: Take 6.8g of DBU and mix it with 68g of deionized water after step (1), stir evenly to form DBU-H2O catalytic system;
[0041] (3) Aldol condensation reaction: Pretreated bio-based acetone and bio-based acetaldehyde were added to a 1000ml polytetrafluoroethylene-lined reactor, and the above catalytic system was added. Stirring was started and the stirring speed was controlled at 120r / min. The reaction was first carried out at 0℃ for 1.5h, and then the temperature was increased to 75℃ at a heating rate of 10℃ / h. The reaction was maintained for 7h to obtain the reaction solution.
[0042] (4) Separation and purification: The reaction solution was vacuum filtered (filter paper pore size 0.22μm) to remove insoluble impurities, and then centrifuged at 3000r / min for 15min to collect the supernatant; the supernatant was added to a distillation flask, and the first stage was distilled at atmospheric pressure at a temperature of 110℃ to recover DBU; the second stage was distilled under reduced pressure at a vacuum of 0.07MPa and a temperature of 80℃ to collect the fraction and obtain the 4-hydroxy-2-pentanone product;
[0043] (5) Catalyst recovery: The DBU recovered from the first stage of distillation is purified by vacuum distillation, with the vacuum degree controlled at 0.09 MPa and the temperature at 180℃, to obtain a reusable DBU catalyst.
[0044] The purity of the 4-hydroxy-2-pentanone product obtained in this example was 98.5%, and the reaction yield was 85.1%. The purity of the recovered DBU catalyst was 99.0%, and after being reused 6 times, the catalytic activity was still 91.5% of the initial activity.
[0045] Example 3
[0046] A method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde includes the following steps:
[0047] (1) Raw material pretreatment: Take 130g of bio-based acetone with a purity of 99.5% and 58g of bio-based acetaldehyde with a purity of 99.5%, respectively dehydrated by 3A molecular sieve, and control the moisture content ≤0.1%; take 100mL of deionized water, boil and cool it for later use.
[0048] (2) Preparation of the catalytic system: Take 9.4g of DBU and mix it with 94g of deionized water treated in step (1), stir evenly, and form Catalytic system;
[0049] (3) Aldol condensation reaction: Pretreated bio-based acetone and bio-based acetaldehyde were added to a 1000ml polytetrafluoroethylene-lined reactor, and the above-mentioned catalytic system was added. Stirring was started and the stirring speed was controlled at 180r / min. The reaction was first carried out at 10℃ for 0.5h, and then the temperature was increased to 85℃ at a heating rate of 9℃ / h. The reaction was maintained for 4h to obtain the reaction solution.
[0050] (4) Separation and purification: The reaction solution was vacuum filtered (filter paper pore size 0.3 μm) to remove insoluble impurities, and then centrifuged at 3000 r / min for 12 min to collect the supernatant; the supernatant was added to a distillation flask, and the first stage was distilled at atmospheric pressure at a controlled temperature of 120℃ to recover DBU; the second stage was distilled under reduced pressure at a controlled vacuum of 0.09 MPa and a temperature of 85℃ to collect the fraction and obtain the 4-hydroxy-2-pentanone product;
[0051] (5) Catalyst recovery: The DBU recovered from the first stage of distillation is purified by vacuum distillation, with the vacuum degree controlled at 0.09 MPa and the temperature at 190℃, to obtain a reusable DBU catalyst.
[0052] The purity of the 4-hydroxy-2-pentanone product obtained in this example was 99.0%, and the reaction yield was 85.8%. The purity of the recovered DBU catalyst was 99.3%, and after being reused 8 times, the catalytic activity was still 90.8% of the initial activity.
[0053] Comparative Example 1
[0054] The existing mixed catalyst is used: a method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde. Except that the catalyst system in step (2) is replaced with a mixed catalyst of strong basic anion exchange resin (D296 type) and magnesium hydroxide (mass ratio 2:1), the amount of which is 5% of the total mass of acetone and acetaldehyde, and the mixed catalyst needs to be pretreated (soaked in deionized water for 24 hours, soaked in 5% sodium hydroxide solution for 8 hours, rinsed until neutral, and vacuum dried), the other steps are the same as in Example 1.
[0055] The purity of the 4-hydroxy-2-pentanone product obtained in this comparative example was 96.2%, and the reaction yield was 79.5%. The catalyst could not be recovered, and the product was pale yellow in color with a slight off-odor, requiring additional decolorization and deodorization treatment.
[0056] Comparative Example 2
[0057] An inorganic strong base catalyst is used: a method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde. Except that the catalyst system in step (2) is replaced with 0.5wt% sodium hydroxide aqueous solution, and the amount is 5% of the total mass of acetone and acetaldehyde, the other steps are the same as in Example 1.
[0058] Testing revealed that the purity of the 4-hydroxy-2-pentanone product obtained in this comparative example was 95.8%, and the reaction yield was 78.3%. The product had a high content of byproducts, was dark yellow in color, had a noticeable off-odor, and generated a large amount of alkaline waste liquid after the reaction. The catalyst could not be recovered, resulting in environmental pollution.
[0059] Comparing Examples 1-3 with Comparative Examples 1-2, it can be seen that the present invention uses DBU as a catalyst, which does not require complex pretreatment. The product yield and purity are significantly higher than those of the prior art. Moreover, the product is light in color and odorless. The catalyst can be recycled, making it green and environmentally friendly. It has obvious technical advantages and industrial application value.
[0060] The above description represents a preferred embodiment of the present invention. For those skilled in the art, any changes, modifications, substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention, based on the teachings of the present invention, still fall within the protection scope of the present invention.
Claims
1. A method for producing 4-hydroxy-2-pentanone by reacting acetone with acetaldehyde, characterized in that, Includes the following steps: (1) Raw material pretreatment: Bio-based acetone and bio-based acetaldehyde were dehydrated by molecular sieves to control the moisture content to ≤0.1%; deionized water was boiled and cooled to remove dissolved carbon dioxide and set aside for later use. (2) Preparation of catalytic system: Mix DBU with deionized water after step (1) and stir evenly to form DBU-H2O catalytic system, wherein the mass ratio of DBU to deionized water is 1:10; (3) Aldol condensation reaction: Pretreated bio-based acetone and bio-based acetaldehyde were added to the reaction vessel at a molar ratio of 1.0~1.3:1, and then the catalytic system prepared in step (2) was added, wherein the amount of DBU was 3%~7% of the total mass of acetone and acetaldehyde; stirring was started, and the stirring speed was controlled to react at low temperature first, and then the temperature was increased to react to obtain the reaction solution. (4) Separation and purification: The reaction liquid obtained in step (3) is filtered and centrifuged to remove impurities, and then subjected to two-stage distillation. The first stage is atmospheric distillation, with the temperature controlled at a certain temperature, to recover DBU; the second stage is vacuum distillation, with the vacuum degree and temperature controlled, to collect the fraction and obtain the 4-hydroxy-2-pentanone product. (5) Catalyst recovery: The DBU recovered from the first stage of distillation is purified by vacuum distillation, with the vacuum degree controlled at 0.09MPa and the temperature at 180~190℃, to obtain a reusable DBU catalyst.
2. The method according to claim 1, characterized in that, In step (1), the purity of the bio-based acetone and bio-based acetaldehyde is ≥99.5%.
3. The method according to claim 1, characterized in that, In step (3), the molar ratio of bio-based acetone to bio-based acetaldehyde is 1.2:1, and the amount of DBU used is 5% of the total mass of acetone and acetaldehyde.
4. The method according to claim 1, characterized in that, In step (3), the reactor is a polytetrafluoroethylene-lined reactor, and the pressure is controlled at atmospheric pressure of 0.1 MPa and the heating rate is ≤10℃ / h during the reaction.
5. The method according to claim 1, characterized in that, In step (3), the stirring is turned on and the stirring speed is controlled at 120~180 r / min. The reaction is first carried out at a low temperature of 0~10℃ for 0.5~1.5h, and then the temperature is raised to 75~85℃ and the reaction is maintained for 4~7h to obtain the reaction solution.
6. The method according to claim 5, characterized in that, In step (3), the stirring speed is 150 r / min, the low temperature reaction time is 1 h, and the heating reaction time is 5 h.
7. The method according to claim 1, characterized in that, In step (4), the centrifugation conditions are 3000 r / min and centrifugation for 10 to 15 min; the filtration is performed by vacuum filtration, and the filter paper pore size is 0.22 to 0.45 μm.
8. The method according to claim 1 or 7, characterized in that, In step (4), the first stage is atmospheric distillation, with the temperature controlled at 110~120℃, to recover DBU; the second stage is vacuum distillation, with the vacuum degree controlled at 0.07~0.09MPa and the temperature at 80~85℃.
9. The method according to claim 8, characterized in that, In step (4), the 4-hydroxy-2-pentanone product obtained has a purity of ≥98.5% and a reaction yield of ≥85%.
10. The method according to claim 1, characterized in that, In step (5), the recovered DBU catalyst is reused 5 to 8 times and its catalytic activity remains above 90% of its initial activity.