A method for preparing diacetone alcohol by acetone condensation

Abstract

This application discloses a method for preparing diacetone alcohol by acetone condensation, comprising the following steps: in a reactor, acetone is contacted with a catalyst, stirred, and reacted to obtain diacetone alcohol; the catalyst is selected from a molecular sieve treated with ammonia; the molecular sieve is selected from at least one of MCM-41 molecular sieve, MCM-48 molecular sieve, and SBA-15 molecular sieve. This method has advantages such as high acetone conversion rate and diacetone alcohol yield, good catalyst recycling performance, simple post-reaction treatment, and no waste salt or wastewater generated.

Description

Technical Field

[0001] This application relates to a method for preparing diacetone alcohol by acetone condensation, which belongs to the field of chemical engineering. Background Technology

[0002] Diacetone alcohol is mainly used as a medium-boiling-point solvent to dissolve resins, cellulose acetate, cellulose nitrate, ethyl cellulose, polyvinyl acetate, polystyrene, and plexiglass. It is also used as a wood preservative, metal cleaner, anti-settling agent for pharmaceuticals, and a raw material for organic synthesis, in the preparation of products such as isopropylidene acetone and methyl isobutyl ketone. Diacetone alcohol can be prepared by the condensation reaction of acetone in the presence of alkaline conditions such as NaOH and Ba(OH)₂. However, this method involves catalysts that cannot be recycled, requires neutralization of the reaction solution, generates large amounts of waste salt and wastewater, and has complex post-treatment processes, easily producing byproducts such as isopropylidene acetone. Under the catalysis of alkaline ion exchange resins, acetone can be condensed to produce diacetone alcohol, but the recycling performance of alkaline ion exchange resin catalysts is poor. Currently, in the process of preparing diacetone alcohol by acetone condensation, the single-pass conversion rate of acetone is generally less than 25%, and the yield of diacetone alcohol is generally less than 24%. Summary of the Invention

[0003] To address the problems of catalyst non-recyclability or poor recycling performance, complex post-reaction treatment, and large amounts of waste salt and wastewater generated in the current acetone condensation preparation of diacetone alcohol, this application provides a method for acetone condensation preparation of diacetone alcohol, which has advantages such as high acetone conversion rate and diacetone alcohol yield, good catalyst recycling performance, simple post-reaction treatment, and no waste salt and wastewater generation.

[0004] According to one aspect of this application, a method for preparing diacetone alcohol by acetone condensation is provided, comprising the following steps:

[0005] In a reactor, acetone is contacted with a catalyst, stirred, and reacted to obtain diacetone alcohol;

[0006] The catalyst is selected from molecular sieves treated with ammonia.

[0007] The molecular sieve is selected from at least one of MCM-41 molecular sieve, MCM-48 molecular sieve, and SBA-15 molecular sieve.

[0008] The temperature for ammonia treatment is 700–900°C;

[0009] Optionally, the temperature for the ammonia treatment is independently selected from any value of 700°C, 750°C, 800°C, 850°C, 900°C, or a range between any two.

[0010] The ammonia treatment time is 2-4 hours;

[0011] Optionally, the ammonia treatment time is independently selected from any value of 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any range between two.

[0012] The pressure for ammonia treatment is 0.1–1.0 MPa.

[0013] Optionally, the pressure for ammonia treatment is independently selected from any value of 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1.0 MPa, or a range between any two.

[0014] The mass of the catalyst is 1 to 10 wt% of the mass of acetone.

[0015] Optionally, the mass of the catalyst is independently selected from any value of 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt% of the mass of acetone, or a range between any two.

[0016] The reaction temperature is -5 to 25°C;

[0017] Optionally, the reaction temperature is independently selected from any value or a range between -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, and 25°C.

[0018] The reaction time is 1 to 4 hours.

[0019] Optionally, the reaction time is independently selected from any value of 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or a range between any two.

[0020] The stirring speed is 200-500 rpm.

[0021] Optionally, the stirring speed is independently selected from any value or a range between 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm.

[0022] According to this application, the catalyst is extremely important. Without a catalyst or with low catalyst activity, diacetone alcohol products cannot be obtained, or the diacetone alcohol yield is very low. High catalyst activity and selectivity are necessary to achieve high conversion rates of acetone and high yields of diacetone alcohol. Good catalyst stability is also essential for excellent catalytic recycling performance.

[0023] The beneficial effects that this application can produce include:

[0024] The method for preparing diacetone alcohol by acetone condensation provided in this application has advantages such as high acetone conversion rate and diacetone alcohol yield, good catalyst recycling performance, simple post-processing, and no waste salt or wastewater generated, and has good prospects for industrial application. Detailed Implementation

[0025] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0026] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0027] Unless otherwise specified, all testing methods shall be conventional.

[0028] In the embodiments of this application, the conversion rate and yield are calculated as follows:

[0029]

[0030] This application uses Agilent 7890A-5975C gas chromatography-mass spectrometry to determine the acetone conversion rate and diacetone alcohol yield.

[0031] Example 1

[0032] 5.0 g of MCM-41 molecular sieve was placed in a stainless steel reaction tube, heated to 700 °C under nitrogen protection, ammonia was introduced, and the reaction was carried out at 0.1 MPa for 4 hours. After cooling to room temperature, 5.0 g of nitrogen-doped MCM-41 molecular sieve catalyst I was obtained.

[0033] Example 2

[0034] 5.0 g of MCM-48 molecular sieve was placed in a stainless steel reaction tube, heated to 800 °C under nitrogen protection, ammonia was introduced, and the reaction was carried out at 0.5 MPa for 3 hours. After cooling to room temperature, 5.0 g of nitrogen-doped MCM-48 molecular sieve catalyst II was obtained.

[0035] Example 3

[0036] 5.0 g of SBA-15 molecular sieve was placed in a stainless steel reaction tube, heated to 900 °C under nitrogen protection, ammonia was introduced, and the reaction was carried out at 1.0 MPa for 2 hours. After cooling to room temperature, 5.0 g of nitrogen-doped SBA-15 molecular sieve catalyst III was obtained.

[0037] Example 4

[0038] 20g of acetone and 2.0g of nitrogen-doped MCM-41 molecular sieve catalyst I were mixed and reacted at -5℃ and 200 rpm for 4 hours. The conversion rate of acetone and the yield of diacetone alcohol were determined by gas chromatography-mass spectrometry.

[0039] Example 5

[0040] 20g of acetone and 1.0g of nitrogen-doped MCM-48 molecular sieve catalyst II were mixed and stirred at 0℃ and 400 rpm for 2 hours. The conversion rate of acetone and the yield of diacetone alcohol were determined by gas chromatography-mass spectrometry.

[0041] Example 6

[0042] 20g of acetone and 0.2g of nitrogen-doped SBA-15 molecular sieve catalyst III were mixed and reacted at 25°C and 500 rpm for 1 hour. The conversion rate of acetone and the yield of diacetone alcohol were determined by gas chromatography-mass spectrometry.

[0043] Example 7

[0044] The reaction mixture obtained in Example 4 was centrifuged, and the resulting solid catalyst was mixed with 20g of acetone. The mixture was stirred at -5°C and 200 rpm for 4 hours. The acetone conversion rate was 25%, and the diacetone alcohol yield was 25%. After the catalyst was recycled 20 times, the acetone conversion rate and the diacetone alcohol yield were still 25%.

[0045] Comparative Examples 1-2

[0046] Comparative Examples 1 and 2 are similar to Example 1, except that different molecular sieves are used, while other reaction conditions are the same as in Example 1.

[0047] The difference between Comparative Example 1 and Example 1 is that 5.0g of ZSM-5 molecular sieve was used instead of 5.0g of MCM-41 molecular sieve, resulting in 5.0g of nitrogen-doped ZSM-5 molecular sieve catalyst IV.

[0048] The difference between Comparative Example 2 and Example 1 is that 5.0g of β molecular sieve was used instead of 5.0g of MCM-41 molecular sieve, resulting in 5.0g of nitrogen-doped β molecular sieve catalyst V.

[0049] Comparative Examples 3-6

[0050] Comparative Examples 3-6 are similar to Example 4, except that different catalysts are used, while other reaction conditions are the same as in Example 4.

[0051] The difference between Comparative Example 3 and Example 4 is that no catalyst was used, and no diacetone alcohol product was obtained.

[0052] The difference between Comparative Example 4 and Example 4 is that 2.0g of MCM-41 molecular sieve was used instead of 2.0g of nitrogen-doped MCM-41 molecular sieve catalyst I, and no diacetone alcohol product was obtained.

[0053] The difference between Comparative Example 5 and Example 4 is that 2.0g of nitrogen-doped ZSM-5 molecular sieve catalyst IV was used instead of 2.0g of nitrogen-doped MCM-41 molecular sieve catalyst I. As a result, the acetone conversion rate was 6% and the diacetone alcohol yield was 6%.

[0054] The difference between Comparative Example 6 and Example 4 is that 2.0 g of nitrogen-doped β molecular sieve catalyst V was used instead of 2.0 g of nitrogen-doped MCM-41 molecular sieve catalyst I. As a result, the acetone conversion rate was 8% and the diacetone alcohol yield was 8%.

[0055] Comparative Examples 3-6 show that the catalyst has a significant impact on the acetone conversion and diacetone alcohol yield in the reaction described in this invention. No diacetone alcohol product was obtained without using a catalyst or using an undoped molecular sieve as a catalyst; both the acetone conversion and diacetone alcohol yield were very low when using nitrogen-doped ZSM-5 molecular sieves and nitrogen-doped β-molecular sieves as catalysts. This may be because, compared with microporous molecular sieves such as ZSM-5 and β-zeolites, MCM-41, MCM-48, and SBA-15 molecular sieves have mesoporous amorphous structures with larger pore sizes and larger specific surface areas. Nitrogen is more easily incorporated into the surface or framework of MCM-41, MCM-48, and SBA-15 molecular sieves. The nitrogen-doped MCM-41, MCM-48, and SBA-15 molecular sieves obtained have higher nitrogen content and stronger basicity compared with nitrogen-doped ZSM-5 and β-zeolites, which is more conducive to promoting the condensation of acetone to diacetone alcohol and obtaining diacetone alcohol in high yield.

[0056] Example 7 illustrates that the nitrogen-doped MCM-41 molecular sieve catalyst has good recycling performance, which may be because nitrogen is chemically bonded to the molecular sieve, resulting in good stability and thus excellent catalytic recycling performance.

[0057] In summary, this application involves stirring and reacting a mixture containing acetone and a catalyst to obtain diacetone alcohol. The catalyst is nitrogen-doped molecular sieve I, selected from at least one of nitrogen-doped MCM-41, MCM-48, and SBA-15 molecular sieves. Nitrogen-doped molecular sieve I is prepared by reacting molecular sieve II with ammonia, where molecular sieve II is selected from at least one of MCM-41, MCM-48, and SBA-15 molecular sieves. This method offers advantages such as high acetone conversion and diacetone alcohol yield, good catalyst recycling performance, simple post-reaction treatment, and no waste salt or wastewater generation.

[0058] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing diacetone alcohol by acetone condensation, characterized in that, Includes the following steps: In a reactor, acetone is contacted with a catalyst, stirred, and reacted to obtain diacetone alcohol; The catalyst is selected from molecular sieves treated with ammonia. The molecular sieve is selected from at least one of MCM-41 molecular sieve, MCM-48 molecular sieve, and SBA-15 molecular sieve.

2. The method according to claim 1, characterized in that, The temperature for ammonia treatment is 700–900°C; The ammonia treatment time is 2-4 hours; The pressure for ammonia treatment is 0.1–1.0 MPa.

3. The method according to claim 1, characterized in that, The mass of the catalyst is 1 to 10 wt% of the mass of acetone.

4. The method according to claim 1, characterized in that, The reaction temperature is -5 to 25°C; The reaction time is 1 to 4 hours.

5. The method according to claim 1, characterized in that, The stirring speed is 200-500 rpm.

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