A process for the preparation of methyl isopentyl ketone

Abstract

This invention relates to a method for preparing methyl isopentyl ketone, comprising the following steps: acetone and isobutyraldehyde are mixed and passed through a fixed-bed reaction section packed with a layered metal oxide condensation catalyst; acetone and isobutyraldehyde are recovered by distillation for reuse; the condensation product enters a fixed-bed hydrogenation section, where it reacts with hydrogen under the action of a hydrogenation catalyst to obtain methyl isopentyl ketone. This invention separates the key reaction steps of condensation and hydrogenation. Firstly, the condensation catalyst designed based on the aldehyde-ketone condensation mechanism has higher condensation selectivity, forming the MIAK hydrogenation precursor, thus avoiding the self-condensation reaction of acetone and isobutyraldehyde and also avoiding the conversion of acetone to alcohol.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and more specifically, to a method for preparing methyl isopentyl ketone. Background Technology

[0002] Methyl isopentyl ketone, also known as 5-methyl-2-hexanone (MIAK for short), is a colorless and transparent liquid with extremely strong dissolving power, low evaporation rate, and high stability. It is commonly used in high-solids coatings, such as polyurethane paint resins, to improve leveling properties and film fullness, imparting a glossy effect similar to projection. Adding a certain amount can significantly improve film performance. It can also be used in the synthesis of acrylic resins, utilizing its solvent properties to improve compatibility between resins. Furthermore, methyl isopentyl ketone is a raw material for synthesizing 7PPD antioxidants, which possess excellent resistance to heat aging and ozonolysis, providing good protection against weathering and fatigue aging.

[0003] Currently, methyl isopentyl ketone can be synthesized in two or one step using a catalyst, through condensation, dehydration, and hydrogenation reactions of the reactants. MIAK research on this topic is relatively limited. CN 114436794 A reports a one-step method for synthesizing methyl isopentyl ketone using a bifunctional palladium / phosphonic acid resin catalyst; however, this method results in a low conversion rate of isobutyraldehyde (only 44.2%), and also suffers from drawbacks such as numerous byproducts, significant feed loss, and a complex and difficult desalination process. CN116462580A provides a method for synthesizing methyl isopentyl ketone in a trickle-bed reactor. Although this method improves the conversion rate of isobutyraldehyde, the feed flow is complex, making long-term stable operation difficult. Summary of the Invention

[0004] To address the technical problems of existing MIAK synthesis technology, such as numerous byproducts, high raw material losses, and complex and difficult desalination processes, this invention provides a method for preparing methyl isopentyl ketone. This method features high raw material conversion rate, solvent recyclability, and high product yield.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] After mixing acetone and isobutyraldehyde, the mixture is passed through a fixed-bed reaction section containing a layered metal oxide condensation catalyst. The acetone and isobutyraldehyde are then recovered by distillation for reuse. The condensation product enters a fixed-bed hydrogenation section, where it reacts with hydrogen under the action of a hydrogenation catalyst to obtain methyl isopentyl ketone.

[0007] The metal oxide condensation catalyst is a layered metal oxide composed of Ce, Mg and Al. Specifically, the ratio of Ce to Al in the metal oxide is 0.1 to 0.5:1, preferably 0.1 to 0.25:1; the ratio of Mg to Al in the metal oxide is 1 to 4:1, preferably 2:1.

[0008] The ratio of Ce to Al in the metal oxide is 0.1 to 0.25:1, and the ratio of Mg to Al in the metal oxide is 2:1.

[0009] The hydrogenation catalyst is activated carbon supported by the noble metal Pt or Pd; preferably, the noble metal is Pt or Pd; the mass percentage of the noble metal Pt or Pd in ​​the chlorination catalyst is 0.5%;

[0010] The hydrogenation catalyst is supported on coconut shell carbon; preferably, the specific surface area of ​​the coconut shell carbon is ≥1000 m². 2 / g, pore volume is 0.3-2.5g / ml, pore size is 0.5-2.5nm, ash content is ≤5%, and water absorption rate is 40-85%.

[0011] The condensation process conditions are as follows: reaction pressure of 1 MPa to 2 MPa, reaction temperature of 60°C to 100°C, and total volume hourly space velocity (VHSV) of acetone and isobutyraldehyde of 3 h⁻¹. -1 The molar ratio of ketone to aldehyde is 1.5:1 to 5:1.

[0012] The distillation recovery column has a pressure of 0.1 MPa, a top temperature of 120°C, a bottom temperature of 100°C, and a reflux ratio of 4.

[0013] The hydrogenation process conditions are as follows: reaction pressure of 1 MPa to 2 MPa, reaction temperature of 100°C to 180°C, and liquid hourly space velocity of 3 h⁻¹. -1 The hydrogen-to-oil ratio is 200:1.

[0014] Compared with the prior art, the embodiments of this application have at least the following advantages or beneficial effects:

[0015] This invention separates the key reaction steps of condensation and hydrogenation. First, the condensation catalyst designed based on the aldehyde-ketone condensation mechanism has higher condensation selectivity, forming the MIAK hydrogenation precursor, avoiding the self-condensation reaction of acetone and isobutyraldehyde, and also avoiding the conversion of acetone to alcohol. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process of the present invention.

[0017] Among them, 1-acetone, 2-isobutyraldehyde, 3-aldehyde-ketone mixture, 4-condensation product, 5-recovered acetone and isobutyraldehyde, 6-condensation product, 7-methylisoamyl ketone; A-condensation reaction tube, B-distillation recovery tower, C-hydrogenation reaction tube. Detailed Implementation

[0018] 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] like Figure 1 As shown, 1-acetone and 2-isobutyraldehyde are mixed and passed through an A-condensation reaction tube containing layered metal oxides. Then, acetone and isobutyraldehyde are recovered and reused through a B-distillation column. The 6-condensation product enters a C-hydrogenation reactor and reacts with hydrogen to obtain 7-methylisoamyl ketone.

[0020] Example 1

[0021] A method for preparing methyl polycarbonate includes the following steps:

[0022] Acetone and isobutyraldehyde were mixed at a molar ratio of 1.5:1 and then pumped into a fixed-bed reactor containing layered metal oxides (with Ce, Mg, and Al in a ratio of 0.25:2:1) for a condensation reaction (reaction temperature 100℃, reaction pressure 1 MPa, space velocity 3.0 h⁻¹). -1 The acetone and isobutyraldehyde were recovered and reused via a distillation recovery column (pressure 0.1 MPa, top temperature 120℃, bottom temperature 100℃, reflux ratio 4). The condensation product was then fed into a hydrogenation fixed-bed reactor packed with 0.5% Pd / C and reacted with hydrogen gas (reaction pressure 2 MPa, reaction temperature 180℃, reaction liquid hourly space velocity 3.0 h⁻¹). -1 (with a hydrogen-to-oil ratio of 200:1), methyl isopentyl ketone was obtained.

[0023] The calculation methods for isobutyraldehyde conversion rate and MIAK selectivity are as follows:

[0024] The molar conversion rate of isobutyraldehyde = (moles of isobutyraldehyde in the raw material - moles of isobutyraldehyde in the product) / moles of isobutyraldehyde in the raw material;

[0025] Molar selectivity of MIAK = (moles of MIAK in the product) / (moles of isobutyraldehyde in the raw material - moles of isobutyraldehyde in the product)

[0026] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 95.77%, the MIAK selectivity was 92.15%, the by-product (methyl isobutyl ketone) selectivity was 7.38%, and the content of unreacted intermediates in the product was less than 5%.

[0027] Example 2

[0028] This embodiment is basically the same as Example 1, except that the molar ratio of acetone to isobutyraldehyde is 3:1.

[0029] Gas chromatography (GC) analysis of the components in the reaction mixture and the finished product showed that the isobutyraldehyde conversion rate was 99.89%, the MIAK selectivity was 84.16%, the byproduct (methyl isobutyl ketone) selectivity was 11.75%, and the content of unreacted intermediates in the product was less than 5%.

[0030] Example 3

[0031] This embodiment is basically the same as Example 1, except that the molar ratio of acetone to isobutyraldehyde is 5:1.

[0032] Gas chromatography (GC) analysis of the components in the reaction mixture and the finished product showed that the isobutyraldehyde conversion rate was 99.99%, the MIAK selectivity was 67.11%, the by-product (methyl isobutyl ketone) selectivity was 31.34%, and the content of unreacted intermediates in the product was less than 5%.

[0033] Example 4

[0034] This embodiment is basically the same as Example 1, except that the ratio of Ce, Mg and Al in the condensation catalyst is 0:2:1.

[0035] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 96.12%, the MIAK selectivity was 89.13%, the by-product (methyl isobutyl ketone) selectivity was 10.22%, and the content of unreacted intermediates in the product was less than 5%.

[0036] Example 5

[0037] This embodiment is basically the same as Example 1, except that the ratio of Ce, Mg and Al in the condensation catalyst is 0.1:2:1.

[0038] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 95.44%, the MIAK selectivity was 92.76%, the by-product (methyl isobutyl ketone) selectivity was 6.82%, and the content of unreacted intermediates in the product was less than 5%.

[0039] Example 6

[0040] This embodiment is basically the same as Embodiment 1, except that the reaction temperature of the condensation stage is 60°C.

[0041] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 56.44%, the MIAK selectivity was 90.14%, the by-product (methyl isobutyl ketone) selectivity was 8.37%, and the content of unreacted intermediates in the product was less than 5%.

[0042] Example 7

[0043] This embodiment is basically the same as Embodiment 1, except that the reaction pressure of the condensation section is 2 MPa.

[0044] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 98.21%, the MIAK selectivity was 93.55%, the by-product (methyl isobutyl ketone) selectivity was 4.79%, and the content of unreacted intermediates in the product was less than 5%.

[0045] Example 8

[0046] This embodiment is basically the same as Example 1, except that the hydrogenation catalyst is a 0.5% Pt / C catalyst.

[0047] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 98.21%, the MIAK selectivity was 90.12%, the by-product (methyl isobutyl ketone) selectivity was 8.11%, and the content of unreacted intermediates in the product was less than 5%.

[0048] Example 9

[0049] This embodiment is basically the same as Example 1, except that the reaction temperature of the hydrogenation section is 100°C and the reaction pressure is 1 MPa.

[0050] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 95.35%, the MIAK selectivity was 91.13%, the by-product (methyl isobutyl ketone) selectivity was 8.24%, and the content of unreacted intermediates in the product was greater than 40%.

[0051] Example 10

[0052] This embodiment is basically the same as Embodiment 1, except that the reaction temperature of the hydrogenation section is 150°C and the reaction pressure is 1.5 MPa.

[0053] Gas chromatography (GC) analysis of the components in the reaction solution and the finished product showed that the isobutyraldehyde conversion rate was 94.27%, the MIAK selectivity was 92.13%, the by-product (methyl isobutyl ketone) selectivity was 7.54%, and the content of unreacted intermediates in the product was greater than 20%.

[0054] Comparative Example 1

[0055] Compared with Example 1, in this embodiment, acetone and isobutyraldehyde were mixed in a molar ratio of 1:5:1 and then pumped into a hydrogenation fixed-bed reactor filled with 0.5% Pd / C to react with hydrogen (reaction pressure 2 MPa, reaction temperature 180°C, reaction liquid hourly space velocity 3.0 h⁻¹, hydrogen-to-oil ratio 200:1), and the resulting product was analyzed.

[0056] Gas chromatography (GC) analysis of the components in the reaction mixture and the finished product revealed a conversion rate of 42.37% for isobutyraldehyde, a MIAK selectivity of 22.15%, a selectivity of 18.32% for the byproduct (methyl isobutyl ketone), and a selectivity of 44.17% for isopropanol. Combining the condensation and hydrogenation steps into one process makes it difficult to control the self-condensation and hydrogenation of acetone, resulting in an excessive amount and variety of byproducts.

[0057] Comparative Example 2

[0058] Compared with Example 1, this embodiment uses acidic resin for condensation treatment in the condensation stage, and the condensation catalyst is phosphonic acid resin (water content 35wt%, total acid 2mmol / g). Other reaction conditions are basically the same.

[0059] Gas chromatography (GC) analysis of the components in the reaction mixture and the finished product showed that the isobutyraldehyde conversion rate was 90.88%, the MIAK selectivity was 85.24%, the byproduct (methyl isobutyl ketone) selectivity was 12.16%, and the content of unreacted intermediates in the product was less than 50%. Compared with the phosphonic resin used as the condensation catalyst in the comparative example, the metal oxide used as the condensation catalyst in this example is safer and has stronger condensation activity.

Claims

1. A method for preparing methyl isopentyl ketone, characterized in that, Includes the following steps: After mixing acetone and isobutyraldehyde, the mixture is passed through a fixed-bed reaction section packed with a layered metal oxide condensation catalyst. The acetone and isobutyraldehyde are then recovered by distillation for reuse. The condensation product enters a fixed-bed hydrogenation section, where it reacts with hydrogen under the action of a hydrogenation catalyst to obtain methyl isopentyl ketone.

2. The method according to claim 1, characterized in that, The metal oxide condensation catalyst is a layered metal oxide composed of Ce, Mg and Al. Specifically, the ratio of Ce to Al in the metal oxide is 0.1 to 0.25:1; the ratio of Mg to Al in the metal oxide is 1 to 4:1, and preferably, the ratio of Mg to Al in the metal oxide is 2:

1.

3. The method according to claim 1, characterized in that, The ratio of Ce to Al in the metal oxide is 0.1 to 0.25:1, and the ratio of Mg to Al in the metal oxide is 2:

1.

4. The method according to claim 1, characterized in that, The hydrogenation catalyst is activated carbon supported by the noble metal Pt or Pd; the mass percentage of the noble metal Pt or Pd in ​​the chlorination catalyst is 0.5%.

5. The process according to claim 1, wherein the support of the hydrogenation catalyst is coconut shell charcoal; the specific surface area of the coconut shell charcoal is ≥ 1000 m 2 / g, the pore volume is 0.3-2.5 g / ml, the pore size is 0.5-2.5 nm, the ash content is ≤ 5%, and the water absorption is 40-85%.

6. The method according to claim 1, characterized in that, The condensation process conditions are as follows: reaction pressure is 1-2 MPa, reaction temperature is 60-100℃, total volume space velocity of acetone and isobutyraldehyde is 3h -1 , and molar ratio of ketone aldehyde is 1.5:1-5:

1.

7. The method according to claim 1, characterized in that, The distillation recovery column has a pressure of 0.1 MPa, a top temperature of 120°C, a bottom temperature of 100°C, and a reflux ratio of 4.

8. The method according to claim 1, characterized in that, The hydrogenation process conditions are as follows: reaction pressure is 1-2 MPa, reaction temperature is 100-180℃, reaction liquid volume space velocity is 0.1-5.0 h -1 -1 , hydrogen / oil volume ratio is 200:1.​

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