Preparation method of 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanedione
By combining hard carbon-supported transition metal oxide catalysts and desiccants, the problems of high temperature and low yield in the synthesis of 2,2,4,4-tetramethyl-1,3-cyclobutanedione were solved, achieving a low-energy-consumption, high-yield, and environmentally friendly preparation process.
Patent Information
- Application Number
- CN202511480721.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-16
- Publication Date
- 2026-01-09
AI Technical Summary
Existing methods for synthesizing 2,2,4,4-tetramethyl-1,3-cyclobutanedione suffer from problems such as high-temperature reactions, low product yields, and environmental pollution, especially the isobutyric acid method, which generates high-concentration saline wastewater.
2,2,4,4-Tetramethyl-1,3-cyclobutanedione was synthesized via a dehydration dimerization reaction at 150–200 °C using a hard carbon-supported transition metal oxide catalyst. Desiccant such as magnesium chloride and calcium chloride were used to control the reaction temperature and time, and organic solvents were added for post-treatment.
This method achieves higher product yield at lower temperatures, reduces energy consumption, minimizes the generation of high-concentration saline wastewater, and makes the process more environmentally friendly.
Smart Images
Figure CN121293089A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of compound synthesis technology, specifically relating to a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione. Background Technology
[0002] 2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) is an important diol polyester monomer, mainly used in the production of high-performance polyester materials. Adding CBDO to copolyesters can significantly improve the polyester's temperature resistance, transparency, chemical resistance, and impact strength. 2,2,4,4-Tetramethyl-1,3-cyclobutanedione (TMCB) is an important intermediate in the preparation of CBDO, making its efficient synthesis crucial. Currently, the main methods for synthesizing TMCB include the isobutyryl chloride method, the dimethylmalonic acid method, the isobutyric acid method, and the isobutyric anhydride method. However, all four methods have certain problems. For example, the isobutyryl chloride method produces salty byproducts, resulting in high-concentration saline wastewater, which puts significant environmental pressure on the environment. The dimethylmalonic acid and isobutyric anhydride methods use relatively expensive raw materials. The isobutyric acid method uses inexpensive isobutyric acid, but requires high temperatures (above 400℃) and yields a low product yield (below 50%). Therefore, how to reduce the reaction temperature of the isobutyric acid method while increasing the product yield has become a challenge in this field. Summary of the Invention
[0003] The purpose of this invention is to provide a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione. The preparation method provided by this invention has a lower reaction temperature and a higher product yield.
[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, comprising: Isobutyric acid, catalyst and desiccant were mixed and subjected to dehydration dimerization to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione; The catalyst comprises hard carbon and transition metal oxides supported on the surface of the hard carbon; The temperature for the dehydration dimerization reaction is 150~200℃.
[0005] Preferably, the transition metal in the transition metal oxide includes one or more of Fe, Cu, Zn and Mn.
[0006] Preferably, the mass ratio of the catalyst to isobutyric acid is (0.05~0.2):1.
[0007] Preferably, the method for preparing the catalyst includes the following steps: (1) Impregnate hard carbon with a transition metal salt solution of equal volume to obtain a precursor; (2) The precursor obtained in step (1) is calcined to obtain the catalyst.
[0008] Preferably, the concentration of the transition metal salt in the transition metal salt solution in step (1) is 0.15~0.45 mol / L.
[0009] Preferably, the roasting temperature in step (2) is 300~500℃ and the roasting time is 3~5h.
[0010] Preferably, the desiccant includes one or more of magnesium chloride, calcium chloride, and magnesium sulfate.
[0011] Preferably, the mass ratio of the desiccant to isobutyric acid is (0.25~0.75):1.
[0012] Preferably, the dehydration dimerization reaction takes 5 to 15 hours.
[0013] Preferably, the temperature of the dehydration dimerization reaction is 150~180℃.
[0014] This invention provides a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, comprising: mixing isobutyric acid, a catalyst, and a desiccant, and carrying out a dehydration dimerization reaction to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione; the catalyst comprises hard carbon and a transition metal oxide supported on the surface of the hard carbon; the temperature of the dehydration dimerization reaction is 150~200℃. The addition of a catalyst in this invention enables isobutyric acid to decompose at a lower temperature under the action of the catalyst to generate dimethyl ketene, which then dimerizes to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione, while simultaneously improving the product yield. Results from the examples show that the preparation method provided by this invention, with a reaction temperature of 150~200℃, achieves a molar yield of over 69%. Attached Figure Description
[0015] Figure 1 The image shows the XRD pattern of the hard carbon in Example 1. Figure 2 Here is a SEM image of the hard carbon in Example 1; Figure 3 The XRD pattern of the catalyst prepared in Example 1; Figure 4 SEM image of the catalyst prepared in Example 1; Figure 5 The carbon NMR spectrum of 2,2,4,4-tetramethyl-1,3-cyclobutanedione prepared in Example 1; Figure 6 The XRD pattern of the catalyst prepared in Example 2; Figure 7 SEM image of the catalyst prepared in Example 2; Figure 8 The XRD pattern of the catalyst prepared in Example 3; Figure 9 This is a SEM image of the catalyst prepared in Example 3. Detailed Implementation
[0016] This invention provides a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, comprising: Isobutyric acid, catalyst, and desiccant were mixed and subjected to a dehydration dimerization reaction to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione.
[0017] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and commercially available products well known to those skilled in the art can be used.
[0018] In this invention, the catalyst comprises hard carbon and a transition metal oxide supported on the surface of the hard carbon.
[0019] The catalyst provided by this invention comprises hard carbon. In this invention, the hard carbon serves as a support.
[0020] In one embodiment, the hard carbon is PBSAC spherical hard carbon produced by Shenzhen Global Greenland New Materials Co., Ltd.
[0021] The catalyst provided by this invention further includes a transition metal oxide supported on the surface of the hard carbon. In this invention, the transition metal oxide serves as the catalytically active component.
[0022] In this invention, the transition metal in the transition metal oxide preferably includes one or more of Fe, Cu, Zn and Mn.
[0023] In this invention, the loading of transition metal oxides in the catalyst is preferably 5-8 wt%. As one embodiment, the loading of transition metal oxides in the catalyst can specifically be 5 wt%, 6 wt%, 7 wt%, or 8 wt%. By controlling the loading of transition metal oxides within the above range, this invention can further improve the catalytic performance of the catalyst.
[0024] In this invention, the method for preparing the catalyst preferably includes the following steps: (1) Impregnate hard carbon with a transition metal salt solution of equal volume to obtain a precursor; (2) The precursor obtained in step (1) is calcined to obtain the catalyst.
[0025] The present invention preferably involves impregnating hard carbon with a transition metal salt solution in equal volumes to obtain a precursor.
[0026] In this invention, the transition metal salt in the transition metal salt solution is preferably a hydrochloride salt or a nitrate salt of a transition metal.
[0027] In this invention, the transition metal in the transition metal salt preferably includes one or more of Fe, Cu, Zn, and Mn. In this invention, the transition metal salt subsequently reacts to form a transition metal oxide.
[0028] In this invention, the solvent in the transition metal salt solution is preferably water.
[0029] In this invention, the concentration of the transition metal salt in the transition metal salt solution is preferably 0.15~0.45 mol / L. As one embodiment, the concentration of the transition metal salt in the transition metal salt solution can specifically be 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, or 0.45 mol / L.
[0030] In this invention, the immersion temperature is preferably 20~30℃.
[0031] The present invention does not have any special limitations on the operation of the equal volume impregnation, and any equal volume impregnation technical solution known to those skilled in the art can be used.
[0032] After obtaining the precursor, the present invention preferably calcines the precursor to obtain the catalyst.
[0033] In this invention, the calcination temperature is preferably 300~500℃; the calcination time is preferably 3~5h; and the calcination is preferably carried out in a nitrogen atmosphere. As one embodiment, the calcination temperature can specifically be 300℃, 350℃, 400℃, 450℃, or 500℃; and the calcination time can specifically be 3h, 3.5h, 4h, 4.5h, or 5h.
[0034] After calcination, the present invention preferably cools the calcined product to obtain a catalyst.
[0035] The present invention does not impose any special limitations on the cooling operation; any cooling technique known to those skilled in the art can be used to cool the material to room temperature.
[0036] In this invention, the preferred mass ratio of the catalyst to isobutyric acid is (0.05~0.2):1. As one embodiment, the mass ratio of the catalyst to isobutyric acid can specifically be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, or 0.2:1. The addition of a catalyst in this invention can lower the reaction temperature and increase the product yield. Controlling the mass ratio of the catalyst to isobutyric acid within the above range can further improve the product yield.
[0037] In this invention, the desiccant preferably includes one or more of magnesium chloride, calcium chloride, and magnesium sulfate.
[0038] In this invention, the preferred mass ratio of the desiccant to isobutyric acid is (0.25~0.75):1. As one embodiment, the mass ratio of the desiccant to isobutyric acid can specifically be 0.25:1, 0.3:1, 0.4:1, 0.44:1, 0.5:1, 0.6:1, 0.7:1, or 0.75:1. By controlling the mass ratio of the desiccant to isobutyric acid within the above range, this invention can further improve the product yield.
[0039] The present invention does not have any special limitations on the mixing operation of the isobutyric acid, catalyst and desiccant. The components can be mixed evenly by means of technical solutions known to those skilled in the art.
[0040] In this invention, the temperature of the dehydration dimerization reaction is 150-200°C; the time of the dehydration dimerization reaction is preferably 5-15 hours; the dehydration dimerization reaction is preferably carried out under stirring conditions; the stirring rate is preferably 350-450 rpm, more preferably 400 rpm; the dehydration dimerization reaction is preferably carried out under reflux conditions. As one embodiment, the temperature of the dehydration dimerization reaction can specifically be 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C; the time of the dehydration dimerization reaction can specifically be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or 15 hours. By controlling the temperature and time of the dehydration dimerization reaction within the above ranges, this invention ensures the reaction proceeds fully and further improves the product yield.
[0041] After the dehydration dimerization reaction is completed, the present invention preferably adds an organic solvent to the product of the dehydration dimerization reaction, filters to obtain an organic phase, then rotary evaporates the organic phase, and then recrystallizes the product after rotary evaporation to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione.
[0042] In this invention, the organic solvent is preferably a hydrocarbon solvent, more preferably cyclohexane, n-hexane or n-heptane.
[0043] In this invention, the preferred mass ratio of isobutyric acid to organic solvent is 1 g: (1~2) mL. As one embodiment, the specific mass ratio of isobutyric acid to organic solvent can be 1 g: 1 mL, 1 g: 1.1 mL, 1 g: 1.2 mL, 1 g: 1.3 mL, 1 g: 1.4 mL, 1 g: 1.5 mL, 1 g: 1.6 mL, 1 g: 1.7 mL, 1 g: 1.8 mL, 1 g: 1.9 mL, or 1 g: 2 mL.
[0044] The present invention does not impose any special limitations on the operation of the filtration; solids can be removed by using filtration techniques well known to those skilled in the art.
[0045] In this invention, the preferred temperature for rotary evaporation is 40-50°C. There is no specific limitation on the time for rotary evaporation; the goal is simply to remove the organic solvent completely.
[0046] In this invention, the solvent used for recrystallization is preferably isobutyl isobutyrate; the volume ratio of the solvent to the product after rotary evaporation during recrystallization is preferably (18~22):1, more preferably 20:1.
[0047] The present invention controls the post-processing, which can further improve the purity of the product.
[0048] This invention incorporates a catalyst, enabling isobutyric acid to decompose at a lower temperature under the catalyst's action to generate dimethyl ketene (DMK), which then dimers to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione (TMCB). By controlling parameters such as reaction temperature and time, the yield and purity of the product are improved. The post-processing is simple and does not generate large amounts of high-concentration saline wastewater, making it more environmentally friendly. The entire preparation process has low energy consumption, a simple process, and few byproducts, showing good prospects for industrial application.
[0049] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0050] Example 1 A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows: 25g of isobutyric acid, 2.5g of catalyst, and 10g of calcium chloride are mixed and transferred to a three-necked flask. A reflux condenser is installed, and the mixture is heated to 150℃ at a stirring rate of 400rpm and refluxed for 10h. Heating is then stopped, and 35mL of cyclohexane is added to the reaction mixture. The mixture is filtered to obtain the organic phase, which is then rotary evaporated at 40℃. The product is recrystallized from isobutyl isobutyrate (volume ratio of isobutyl isobutyrate to the rotary evaporated product is 20:1) to obtain 14.91g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione with a purity of 99%, representing a molar yield of 75%. The catalyst consists of hard carbon and Fe2O3 supported on the surface of the hard carbon; The catalyst is prepared by: (1) impregnating hard carbon (PBSAC spherical hard carbon produced by Shenzhen Global Greenland New Materials Co., Ltd.) and ferric chloride aqueous solution (the concentration of ferric chloride in the ferric chloride aqueous solution is 0.30 mol / L) in equal volumes to obtain a precursor; (2) The precursor obtained in step (1) was calcined at 350°C for 4 hours in a nitrogen atmosphere and cooled to room temperature to obtain a catalyst. The loading of Fe2O3 in the catalyst was 5wt%, denoted as 5%Fe@C.
[0051] The XRD pattern of hard carbon in Example 1 is shown below. Figure 1 As shown, the SEM image of hard carbon is as follows: Figure 2 As shown.
[0052] The XRD pattern of the catalyst prepared in Example 1 is shown below. Figure 3 As shown, the SEM image of the prepared catalyst is as follows. Figure 4 As shown.
[0053] The carbon NMR spectrum of 2,2,4,4-tetramethyl-1,3-cyclobutanedione prepared in Example 1 is as follows: Figure 5 As shown.
[0054] Example 2 A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows: 25g of isobutyric acid, 2.5g of catalyst, and 11g of calcium chloride are mixed and transferred to a three-necked flask. A reflux condenser is installed, and the mixture is heated to 150℃ at a stirring rate of 400rpm and refluxed for 10h. Heating is then stopped, and 35mL of cyclohexane is added to the reaction mixture. The mixture is filtered to obtain the organic phase, which is then rotary evaporated at 45℃. The product is recrystallized from isobutyl isobutyrate (volume ratio of isobutyl isobutyrate to the rotary evaporated product is 20:1) to obtain 13.82g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione with a purity of 99%, representing a molar yield of 69%. The catalyst consists of hard carbon and CuO supported on the surface of the hard carbon; The catalyst is prepared by: (1) impregnating hard carbon (PBSAC spherical hard carbon produced by Shenzhen Global Greenland New Materials Co., Ltd.) and copper chloride aqueous solution (the concentration of copper chloride in the copper chloride aqueous solution is 0.25mol / L) in equal volumes to obtain a precursor; (2) The precursor obtained in step (1) was calcined at 400°C for 3 hours in a nitrogen atmosphere and cooled to room temperature to obtain a catalyst. The CuO loading in the catalyst was 5wt%, denoted as 5%Cu@C.
[0055] The XRD pattern of the catalyst prepared in Example 2 is shown below. Figure 6 As shown, the SEM image of the prepared catalyst is as follows. Figure 7 As shown.
[0056] Example 3 A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows: 25g of isobutyric acid, 2.5g of catalyst, and 10g of magnesium chloride are mixed and transferred to a three-necked flask. A reflux condenser is installed, and the mixture is heated to 150℃ at a stirring rate of 400rpm and refluxed for 10h. Heating is then stopped, and 35mL of cyclohexane is added to the reaction mixture. The mixture is filtered to obtain the organic phase, which is then rotary evaporated at 40℃. The product is recrystallized from isobutyl isobutyrate (volume ratio of isobutyl isobutyrate to the rotary evaporated product is 20:1) to obtain 16.27g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione with a purity of 99%, representing a molar yield of 82%. The catalyst consists of hard carbon and ZnO supported on the surface of the hard carbon; The catalyst is prepared by: (1) impregnating hard carbon (PBSAC spherical hard carbon produced by Shenzhen Global Greenland New Materials Co., Ltd.) and zinc chloride aqueous solution (the concentration of zinc chloride in the zinc chloride aqueous solution is 0.3mol / L) in equal volumes to obtain a precursor; (2) The precursor obtained in step (1) was calcined at 500°C for 5 hours in a nitrogen atmosphere and cooled to room temperature to obtain a catalyst. The ZnO loading in the catalyst was 5 wt%, denoted as 5%Zn@C.
[0057] The XRD pattern of the catalyst prepared in Example 3 is shown below. Figure 8 As shown, the SEM image of the prepared catalyst is as follows. Figure 9 As shown.
[0058] Example 4 A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows: 25g of isobutyric acid, 2.5g of catalyst, and 10g of magnesium chloride are mixed and transferred to a three-necked flask. A reflux condenser is installed, and the mixture is heated to 180℃ at a stirring rate of 400rpm and refluxed for 15h. Heating is then stopped, and 40mL of n-hexane is added to the reaction mixture. The mixture is filtered to obtain the organic phase, which is then rotary evaporated at 42℃. The product is recrystallized from isobutyl isobutyrate (volume ratio of isobutyl isobutyrate to the rotary evaporated product is 20:1) to obtain 17.32g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione with a purity of 99%, representing a molar yield of 87%. The catalyst consists of hard carbon and Fe2O3 supported on the surface of the hard carbon; The catalyst is prepared by: (1) impregnating hard carbon (PBSAC spherical hard carbon produced by Shenzhen Global Greenland New Materials Co., Ltd.) and ferric chloride aqueous solution (the concentration of ferric chloride in the ferric chloride aqueous solution is 0.35mol / L) in equal volumes to obtain a precursor; (2) The precursor obtained in step (1) was calcined at 400°C for 5 hours in a nitrogen atmosphere and cooled to room temperature to obtain a catalyst. The loading of Fe2O3 in the catalyst was 7wt%, denoted as 7%Fe@C.
[0059] Example 5 A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows: 30g of isobutyric acid, 4.5g of catalyst, and 15g of calcium chloride are mixed and transferred to a three-necked flask. A reflux condenser is installed, and the mixture is heated to 170℃ at a stirring rate of 400rpm and refluxed for 12h. Heating is then stopped, and 33mL of n-heptane is added to the reaction mixture. The mixture is filtered to obtain the organic phase, which is then rotary evaporated at 45℃. The product is recrystallized from isobutyl isobutyrate (volume ratio of isobutyl isobutyrate to the rotary evaporated product is 20:1) to obtain 19.34g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione with a purity of 99%, representing a molar yield of 81%. The catalyst consists of hard carbon and CuO supported on the surface of the hard carbon; The catalyst is prepared by: (1) impregnating hard carbon (PBSAC spherical hard carbon produced by Shenzhen Global Greenland New Materials Co., Ltd.) and copper chloride aqueous solution (the concentration of copper chloride in the copper chloride aqueous solution is 0.30 mol / L) in equal volumes to obtain a precursor; (2) The precursor obtained in step (1) was calcined at 400°C for 4 hours in a nitrogen atmosphere and cooled to room temperature to obtain a catalyst. The CuO loading in the catalyst was 8wt%, denoted as 8%Cu@C.
[0060] As can be seen from the above embodiments, the preparation method provided by the present invention has a low reaction temperature, below 200°C, and the product has a high yield, above 69%.
[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, comprising: Isobutyric acid, catalyst and desiccant were mixed and subjected to dehydration dimerization to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione; The catalyst comprises hard carbon and transition metal oxides supported on the surface of the hard carbon; The temperature for the dehydration dimerization reaction is 150~200℃.
2. The preparation method according to claim 1, characterized in that, The transition metal in the transition metal oxide includes one or more of Fe, Cu, Zn, and Mn.
3. The preparation method according to claim 1, characterized in that, The mass ratio of the catalyst to isobutyric acid is (0.05~0.2):
1.
4. The preparation method according to claim 1, characterized in that, The method for preparing the catalyst includes the following steps: (1) Impregnate hard carbon with a transition metal salt solution of equal volume to obtain a precursor; (2) The precursor obtained in step (1) is calcined to obtain the catalyst.
5. The preparation method according to claim 4, characterized in that, In step (1), the concentration of the transition metal salt in the transition metal salt solution is 0.15~0.45 mol / L.
6. The preparation method according to claim 4, characterized in that, The roasting temperature in step (2) is 300~500℃ and the roasting time is 3~5h.
7. The preparation method according to claim 1, characterized in that, The desiccant includes one or more of magnesium chloride, calcium chloride, and magnesium sulfate.
8. The preparation method according to claim 7, characterized in that, The mass ratio of the desiccant to isobutyric acid is (0.25~0.75):
1.
9. The preparation method according to claim 1, characterized in that, The dehydration dimerization reaction takes 5 to 15 hours.
10. The preparation method according to claim 1, characterized in that, The temperature for the dehydration dimerization reaction is 150~180℃.