A method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol

Abstract

The present invention relates to a method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol. The preparation method is as follows: in the first step, acetaldehyde and ethyl acrylate undergo a Baylis-Hillman reaction under a triethylenediamine catalyst to generate an enoate; in the second step, the enoate generated in the first step and ethyl acrylate undergo a one-step dehydration and Diels-Alder reaction to obtain cyclohexenedicarboxylate; in the third step, cyclohexenedicarboxylate undergoes selective hydrogenation under a metal catalyst to generate cyclohexanedicarboxylate; and under a dual-bed metal catalyst, complete hydrogenation is carried out to generate cyclohexanedimethanol. The reaction conditions of the present invention are simple, the catalyst is simple and easily available, and the cost is low. It is a method for synthesizing plasticizers by a biomass route with very promising industrialization prospects.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of fine chemicals, and particularly relates to a new method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol. Background Art

[0002] Fossil energy (oil, coal and natural gas) has always occupied an unshakable position in people's daily life and production, and has also deeply affected the world economy, policies and military situations. On the one hand, it has brought great progress and convenience to the whole society, and on the other hand, it has also brought profound environmental problems such as the greenhouse effect, acid rain, land desertification and smog, etc., which have a great impact on people's physical conditions and daily travel, especially the healthy growth of children. Therefore, developing new energy that can replace fossil resources has important strategic significance and application prospects. As a carbon dioxide-neutral, oxygen-rich and renewable organic carbon source, biomass energy has been widely used by scientists to synthesize various oxygen-containing fine chemicals.

[0003] A plasticizer is a substance added to plastics or resins (especially PVC materials) to improve their processability, plasticity, flexibility and stretchability. Adding a plasticizer can reduce the melt viscosity, glass transition temperature and elastic modulus of the product without changing the basic chemical properties of the plasticized material. At present, the global production capacity of plasticizers is about 6.4 million tons / year, and the annual output is about 4.3 million tons. Most of them are centered around phthalate esters, such as the most commonly used diisooctyl phthalate (DEHP) and diisononyl phthalate (DINP), and these two plasticizers account for 63% of this market. Recently, with the progress of people's awareness of environmental protection, plastics such as medical and food packaging, daily necessities and toys have put forward higher purity and cleanliness requirements for plasticizers. PVC environmental protection plasticizers have won a broad market and received more and more attention. Among them, cyclohexanedicarboxylate and cyclohexanedimethanol are environmental protection plasticizers. Industrially, plasticizers are prepared by phthalic anhydride from downstream products of petroleum and corresponding alcohols, and this method completely depends on non-renewable fossil energy. Therefore, exploring the synthesis of common plasticizers by biomass routes has important practical significance and broad application prospects.

[0004] Ethanol, as a very common industrial raw material, can be obtained from biomass through microbial fermentation, namely so-called "bioethanol", and has been industrialized in countries such as the United States and Brazil. It can be prepared into acetaldehyde through an oxidation reaction (J. Am. Chem. Soc. 2013, 135, 14032). Biomass can be obtained from microbial fermentation to produce lactic acid, and ethyl acrylate can be generated through simple esterification and dehydration reactions of lactic acid. This patent has developed a new method for preparing plasticizers using acetaldehyde and ethyl acrylate as renewable raw materials. Summary of the Invention

[0005] The object of the present invention is to provide a biomass route for a new method of preparing plasticizers using acetaldehyde and ethyl acrylate as renewable raw materials.

[0006] The present invention is achieved through the following technical solutions:

[0007] The preparation of cyclohexanedicarboxylate and cyclohexanedimethanol is divided into three reaction steps:

[0008] In the first step, acetaldehyde and acrylate undergo a Baylis-Hillman reaction under a triethylenediamine catalyst to form an enoate.

[0009] In the second step, the enoate obtained in the first step and ethyl acrylate undergo dehydration and a Diels-Alder reaction under an acid catalyst to obtain cyclohexenedicarboxylate.

[0010] In the third step, cyclohexenedicarboxylate undergoes selective hydrogenation under a metal catalyst to form cyclohexanedicarboxylate; or undergoes complete hydrogenation under a dual-bed metal catalyst to form cyclohexanedimethanol.

[0011] Based on the above scheme, preferably, in the second reaction step, adding an inhibitor can improve the yield of cyclohexenedicarboxylate. The inhibitor is one of 2,6-di-tert-butyl-4-methylphenol, 2,2,6,6-tetramethylpiperidine oxide, p-methoxyphenol, and hydroquinone; the molar ratio of the inhibitor added to the enoate formed in the first reaction step is 0.05 - 0.2.

[0012] Based on the above scheme, preferably, the reaction medium for each step is as follows:

[0013] In the first step, this reaction step is carried out under solvent-free conditions;

[0014] In the second step, the reaction medium is one of organic solvents; the organic solvents are one of cyclohexane, ethylene glycol, dimethyl sulfoxide, N,N-dimethylformamide, and tetrahydrofuran;

[0015] In the third step, the solvent used is ethanol.

[0016] Based on the above scheme, preferably, the catalyst for each step is as follows:

[0017] In the first step, the molar ratio of the triethylenediamine catalyst to the reaction substrate acetaldehyde is 0.05 - 0.2;

[0018] In the second step, the acid catalyst is a Lewis acid or a Bronsted acid; the Lewis acid is one of ZnCl2 and FeCl3; the Bronsted acid is one of H2SO4, HCl, HNO3, HCOOH, CF3CO2H, and CF3SO3H; wherein, when the acid catalyst is HCOOH, CF3CO2H, or CF3SO3H, the molar ratio of the added acid catalyst to the enoate formed in the first step is 1-4, preferably 3-4; when the acid catalyst is of other types above, the molar ratio of the added acid catalyst to the enoate formed in the first step is 0.05-0.2, preferably 0.1-0.2;

[0019] In the third step, the metal catalyst used for selective hydrogenation has a noble metal as the active component and a carbon material or a metal oxide as the carrier;

[0020] In the third step, in the dual-bed metal catalyst used for complete hydrogenation, the first-bed metal catalyst has a noble metal as the active component and a carbon material or a metal oxide as the carrier; the second-bed metal catalyst has a non-noble metal as the active component.

[0021] As a further preference of the above solution, the catalysts for each step are specifically as follows:

[0022] In the second step, the Lewis acid is one of ZnCl2 and FeCl3; the Bronsted acid is one of H2SO4, HCl, and HNO3; the molar ratio of the acid catalyst to the enoate formed in the first step is 0.1-0.2;

[0023] In the third step, the metal catalyst used for selective hydrogenation is one of Pd / C, Pd / Al2O3, Ru / C, and Ru / Al2O3;

[0024] In the third step, in the dual-bed metal catalyst used for complete hydrogenation, the first-bed metal catalyst is one of Pd / C and Pt / C; the second-bed metal catalyst is one of Cu / SiO2 and Cu / Zn / Al.

[0025] Based on the above solution, preferably, the specific reaction conditions are as follows:

[0026] In the first step, the molar ratio of the substrate acetaldehyde to ethyl acrylate is 0.5-2; the reaction temperature is 20-40 °C, and the reaction time is between 24-96 h;

[0027] In the second step, the molar ratio of ethyl acrylate to the enoate product of the first step is between 0.5-5; the reaction temperature is between 120-180 °C, and the reaction time is between 6-18 h;

[0028] Step 3: For selective hydrogenation, the hydrogen pressure is between 0.1 - 2 MPa, the selective hydrogenation reaction temperature is between 20 - 50 °C, and the space velocity is between 2.3 - 6.3 h -1 -1; for complete hydrogenation, the hydrogen pressure is between 0.1 - 6 MPa, the complete hydrogenation reaction temperature is between 180 - 240 °C, and the space velocity is between 1 - 3 h -1 -1.

[0029] As a further preference of the above solution, the specific reaction conditions are as follows:

[0030] Step 1: The molar ratio of the substrate acetaldehyde to ethyl acrylate is 1 - 2; the reaction temperature is 20 - 30 °C, and the reaction time is between 72 - 96 h;

[0031] Step 2: The molar ratio of ethyl acrylate to the enoate product of Step 1 is between 2 - 3; the reaction temperature is between 140 - 160 °C, and the reaction time is between 10 - 14 h;

[0032] Step 3: For selective hydrogenation, the reaction temperature is between 20 - 40 °C, and the space velocity is between 4 - 10 h -1 -1; for complete hydrogenation, the hydrogen pressure is between 4 - 6 MPa, the complete hydrogenation reaction temperature is between 200 - 240 °C, and the space velocity is between 1.5 - 2.5 h -1 -1.

[0033] The present invention has the following advantages:

[0034] The traditional synthesis route uses petroleum resources as raw materials. However, fossil resources are becoming increasingly depleted, and carbon dioxide is released during the production process, polluting the environment. The plasticizer synthesis route provided by the present invention is green and environmentally friendly. It uses renewable biomass platform compounds as starting materials, and the dehydration and D - A reaction can be carried out in one step. The reaction conditions are simple, the catalyst is simple and easy to obtain, and the cost is low. Therefore, the present invention is a method for synthesizing plasticizers via a biomass route with great industrialization prospects. Description of the Drawings

[0035] Figure 1 ... GC spectrum of the Reiss - Hillman reaction of triethylenediamine - catalyzed acetaldehyde and ethyl acrylate;

[0036] Figure 2 ... GC spectrum of the preparation of diethyl cyclohexenedicarboxylate from enoate and ethyl acrylate;

[0037] Figure 3 ... GC spectrum of the reaction of hydrogenating dimethyl cyclohexenedicarboxylate to cyclohexanedicarboxylate;

[0038] Figure 4 ... GC spectrum of the reaction of hydrogenating dimethyl cyclohexenedicarboxylate to cyclohexanedimethanol;

[0039] Figure 5 . H-NMR spectra of the enoate product from the Baylis-Hillman reaction of acetaldehyde and ethyl acrylate catalyzed by triethylenediamine 1 ;

[0040] Figure 6 . C-NMR spectra of the enoate product from the Baylis-Hillman reaction of acetaldehyde and ethyl acrylate catalyzed by triethylenediamine 13 ;

[0041] Figure 7 . H-NMR spectra of diethyl cyclohexenedicarboxylate prepared from enoate and ethyl acrylate 1 ;

[0042] Figure 8 . C-NMR spectra of diethyl cyclohexenedicarboxylate prepared from enoate and ethyl acrylate 13 ;

[0043] Figure 9 . H-NMR spectra of cyclohexanedicarboxylate prepared by hydrogenation of dimethyl cyclohexenedicarboxylate 1 ;

[0044] Figure 10 . C-NMR spectra of cyclohexanedicarboxylate prepared by hydrogenation of dimethyl cyclohexenedicarboxylate 13 ;

[0045] Figure 11 . H-NMR spectra of cyclohexanedimethanol prepared by hydrogenation of dimethyl cyclohexenedicarboxylate 1 ;

[0046] Figure 12 . C-NMR spectra of cyclohexanedimethanol prepared by hydrogenation of dimethyl cyclohexenedicarboxylate 13 ;

[0047] Figure 13 . Reaction route diagram for preparing cyclohexanedicarboxylate and cyclohexanedimethanol from acetaldehyde and ethyl acrylate Detailed implementation mode

[0048] The present invention will be described below with specific examples, but the protection scope of the present invention is not limited to these examples.

[0049] 1. Acetaldehyde and ethyl acrylate undergo a Baylis-Hillman reaction under the catalysis of triethylenediamine (DABCO) to form enoate

[0050] In a 35 mL test tube, the catalyst, acetaldehyde, and ethyl acrylate are added in sequence for reaction.

[0051]

[0052] Table 1. Influence of Reaction Conditions on the Reaction

[0053]

[0054] As can be seen from the results in Table 1, when adding 10 mol% of triethylenediamine catalyst, without solvent, at 25 °C, with the molar ratio of acetaldehyde to ethyl acrylate being 1.5:1 and reacting for 72 h, the yield of the enoate can reach 96%. If reacting for 96 h, the yield can reach 97%.

[0055] 2. The enoate and ethyl acrylate undergo a one-step dehydration and Diels-Alder reaction

[0056] In a 35 mL test tube, add enoate 3 and ethyl acrylate 2, then add the catalyst and the reaction solvent (3 mL), and carry out the reaction at a certain temperature, then diethyl cyclohexenedicarboxylate 4a and 4b are obtained.

[0057]

[0058] Table 2. Influence of Different Conditions on the Dehydration / D-A Reaction

[0059]

[0060]

[0061] As can be seen from the results in Table 2, when adding 10 mol% of H2SO4 catalyst, using N,N-dimethylformamide as the reaction medium, at 150 °C, with the molar ratio of the enoate generated in the first step to ethyl acrylate being 1:5 and reacting for 12 h, the yield of diethyl cyclohexenedicarboxylate can reach 60%. If the molar ratio of the enoate generated in the first step to ethyl acrylate is 1:2 and reacting for 12 h, the yield of diethyl cyclohexenedicarboxylate can reach 55%.

[0062] In a 35 mL test tube, add enoate 3 (0.72 g, 5 mmol) and ethyl acrylate 2 (1.09 mL, 10 mmol), then add the catalyst (10 mol%), add the inhibitor, and the reaction solvent (3 mL), and react at 150 °C, then diethyl cyclohexenedicarboxylate 4a and 4b are obtained.

[0063]

[0064] Table 3. Influence of Inhibitors on the Dehydration / D-A Reaction

[0065]

[0066]

[0067] As can be seen from the results in Table 3, when 10 mol% H2SO4 is used as the catalyst, 1 mol% hydroquinone is added as the inhibitor, and the reaction is carried out at 150 °C for 12 h, the yield of the target product diethyl cyclohexenedicarboxylate can reach 77%. If 350 mol% HCOOH is used as the catalyst, 10 mol% hydroquinone is added as the inhibitor, and the reaction is carried out at 150 °C for 12 h, the yield of the target product diethyl cyclohexenedicarboxylate can reach 75%.

[0068] 3. (1) Partial hydrogenation of diethyl cyclohexenedicarboxylates 4a and 4b

[0069] Using a fixed-bed reactor, an ethanol solution (2 wt%) of diethyl cyclohexenedicarboxylates 4a and 4b is added, and then a catalyst is added to obtain diethyl cyclohexanedicarboxylates 5a and 5b.

[0070]

[0071] Table 4. Influence of reaction conditions on the selective hydrogenation reaction

[0072]

[0073] As can be seen from the results in Table 4, when Pd / C is used as the catalyst, ethanol is used as the reaction medium, and the reaction is carried out under 0.1 MPa hydrogen at 25 °C, the yield of the target product diethyl cyclohexanedicarboxylate can reach 99%.

[0074] (2) Complete hydrogenation of diethyl cyclohexenedicarboxylates 4a and 4b

[0075] Using a fixed-bed reactor, an ethanol solution (2 wt%) of diethyl cyclohexenedicarboxylates 4a and 4b is added, and then a catalyst is added to obtain cyclohexanedimethanol 6a and 6b.

[0076]

[0077] Table 5. Influence of catalysts on the selective hydrogenation reaction

[0078]

[0079] Using a fixed-bed reactor, an ethanol solution (2 wt%) of diethyl cyclohexenedicarboxylates 4a and 4b is added, and then the catalysts Pd / C and Cu / Zn / Al are added to obtain cyclohexanedimethanol 6a and 6b.

[0080]

[0081] Table 6. Influence of reaction conditions on the complete hydrogenation

[0082]

[0083] As can be seen from the results in Table 4 and Table 5, Pd / C is the catalyst for the first bed, Cu / Zn / Al is the catalyst for the second bed, and the space velocity is 2.5 h -1 , which can completely hydrogenate cyclohexene dicarboxylate to produce cyclohexane dimethanol. Under the conditions of 200 °C and 6 MPa hydrogen, the yield of the target product cyclohexane dimethanol can reach 99%.

Claims

1. A method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol, characterized in that: The preparation of cyclohexanedicarboxylate and cyclohexanedimethanol is divided into three-step reactions: In the first step, acetaldehyde and ethyl acrylate undergo a Baylis-Hillman reaction under a triethylenediamine catalyst to form an enoate; In the second step, the enoate obtained in the first step and ethyl acrylate undergo dehydration and a Diels-Alder reaction under an acid catalyst to obtain cyclohexenedicarboxylate; the acid catalyst is a Lewis acid or a Bronsted acid; In the third step, cyclohexenedicarboxylate undergoes selective hydrogenation under a metal catalyst to form cyclohexanedicarboxylate; or undergoes complete hydrogenation under a dual-bed metal catalyst to form cyclohexanedimethanol; In the third step, the metal catalyst used for selective hydrogenation is one of Pd / C, Pd / Al2O3, Ru / C, Ru / Al2O3; In the third step, in the dual-bed metal catalyst used for complete hydrogenation, the first-bed metal catalyst is one of Pd / C, Pt / C; the second-bed metal catalyst is one of Cu / SiO2, Cu / Zn / Al.

2. The method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol according to claim 1, characterized in that: The second-step reaction is carried out under the condition of adding an inhibitor; the inhibitor is one of 2,6-di-tert-butyl-4-methylphenol, 2,2,6,6-tetramethylpiperidine oxide, p-methoxyphenol, hydroquinone; the molar ratio of the inhibitor to the enoate formed in the first step is 0.05-0.

2.

3. The method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol according to claim 1, characterized in that: In the first step, the reaction is carried out under solvent-free conditions; In the second step, the reaction medium is one of organic solvents; the organic solvent is one of cyclohexane, ethylene glycol, dimethyl sulfoxide, N,N-dimethylformamide, tetrahydrofuran; In the third step, the solvent used is ethanol.

4. The method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol according to claim 1, characterized in that: In the first step, the molar ratio of the triethylenediamine catalyst to the reaction substrate acetaldehyde is 0.05-0.2; In the second step, the Lewis acid is one of ZnCl2, FeCl3; the Bronsted acid is one of H2SO4, HCl, HNO3, HCOOH, CF3CO2H, CF3SO3H; wherein, when the acid catalyst is HCOOH, CF3CO2H, CF3SO3H, the molar ratio of the added acid catalyst to the enoate formed in the first step is 1-4; when the acid catalyst is the other types, the molar ratio of the added acid catalyst to the enoate formed in the first step is 0.05-0.

2.

5. The method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol according to claim 4, characterized in that: In the second step, the Lewis acid is one of ZnCl2, FeCl3; the Bronsted acid is one of H2SO4, HCl, HNO3; the molar ratio of the acid catalyst to the enoate formed in the first step is 0.1-0.

2.

6. The method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol according to claim 1, characterized in that: First step, the molar ratio of the substrate acetaldehyde to ethyl acrylate is 0.5 - 2; the reaction temperature is 20 - 40 o °C, and the reaction time is between 24 - 96 h; Second step: the molar ratio of ethyl acrylate to the product enoate in the first step is between 0.5 and 5; the reaction temperature is between 120 and 180 o °C, and the reaction time is between 6 and 18 h; Step 3: For selective hydrogenation, the hydrogen pressure is between 0.1 - 2 MPa, the selective hydrogenation reaction temperature is between 20 - 50 o °C, and the space velocity is between 2.3 - 6.3 h -1 -1; for complete hydrogenation, the hydrogen pressure is between 0.1 - 6 MPa, the complete hydrogenation reaction temperature is between 180 - 240 o °C, and the space velocity is between 1 - 3 h -1 -1.

7. The method for preparing cyclohexanedicarboxylate and cyclohexanedimethanol according to claim 6, characterized in that: First step, the molar ratio of the substrate acetaldehyde to ethyl acrylate is 1-2; the reaction temperature is 20-30 o °C, and the reaction time is between 72-96h; Second step, the molar ratio of ethyl acrylate to the product enoate in the first step is between 2 and 3; the reaction temperature is between 140 and 160 o °C, and the reaction time is between 10 and 14 h; In the third step, the selective hydrogenation reaction temperature is between 20 and 40 o °C, and the space velocity is between 4 and 10 h -1 ; the complete hydrogenation hydrogen pressure is between 4 and 6 MPa, and the complete hydrogenation reaction temperature is between 200 and 240 o °C, and the space velocity is between 1.5 and 2.5 h -1 .

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