A method for preparing phthalate

Abstract

The present invention relates to a method for preparing phthalic acid esters. The method for preparing phthalic acid esters comprises the following steps: first, acetaldehyde and ethyl acrylate undergo a Bayes-Hillman reaction in the presence of triethylenediamine as a catalyst to produce an enester; second, the enester produced in the first reaction undergoes a one-step dehydration and Diels-Alder reaction with ethyl acrylate to produce cyclohexene dicarboxylic acid ester; and third, the cyclohexene dicarboxylic acid ester undergoes a dehydrogenation reaction in the presence of a metal catalyst to produce the phthalic acid ester. The method has simple reaction conditions, readily available catalysts, and low cost, and is a biomass-based method for synthesizing plasticizers with great industrial potential.

Description

Technical Field

[0001] The invention belongs to the field of fine chemical preparation, and particularly relates to a method for preparing phthalate esters. Background Art

[0002] Fossil energy (oil, coal, and natural gas) has always held an unshakable position in people's daily lives and production, and has also profoundly influenced the global economy, policies, and military situation. While it has brought tremendous progress and convenience to society as a whole, it has also brought about profound environmental problems, such as the greenhouse effect, acid rain, desertification, and smog. These have a significant impact on people's health and daily travel, especially the healthy development of children. Therefore, the development of new energy sources that can replace fossil resources has important strategic significance and application prospects. Biomass energy, as a carbon dioxide-neutral, oxygen-rich, and renewable organic carbon source, has been widely used by scientists to synthesize various oxygenated fine chemicals, replacing the dominant position of fossil energy.

[0003] Benzoate esters and their derivatives are important chemical raw materials, serving as intermediates in the synthesis of organic pharmaceuticals and industrially used as plasticizers for various polyvinyl chloride materials, such as the commercially available diethylene glycol dibenzoate (DEDB), dioctyl phthalate (DOP), dibutyl phthalate (DBP), and trioctyl trimellitate (TOTM). Of particular note, terephthalate esters are a key bulk organic raw material, primarily used in the large-scale production of polyethylene terephthalate (PET), resulting in polyester fibers, polyester film, and polyester bottles. These esters are widely used in various sectors of the national economy, including chemical fibers, light industry, electronics, and construction, and are closely linked to the quality of life of the people. Currently, the industrial preparation of terephthalate monomers primarily involves the selective oxidation of petroleum-derived p-xylene (PX), a method that is highly dependent on non-renewable fossil energy. Therefore, exploring biomass-based synthesis routes for benzoate esters and their derivatives, particularly terephthalate esters, holds significant practical significance and holds broad application prospects.

[0004] Ethanol, as a very common industrial raw material, can be obtained from biomass through microbial fermentation, the so-called "bioethanol", which has been industrialized in countries such as the United States and Brazil. It can be used to produce acetaldehyde through an oxidation reaction (J.Am.Chem.Soc.2013,135,14032). Biomass can be fermented with microorganisms to produce lactic acid, which can be converted into ethyl acrylate through a simple esterification and dehydration reaction. This patent has developed a new method for preparing benzoic acid esters and their derivatives using acetaldehyde and ethyl acrylate as renewable raw materials. The raw materials and catalysts used are cheap and readily available, and all the reaction processes are simple, with promising industrial application prospects. Summary of the Invention

[0005] The present invention aims to provide a new method for preparing plasticizers by using acetaldehyde and acrylate as renewable raw materials through a biomass route.

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

[0007] The method for preparing phthalate esters using acetaldehyde and ethyl acrylate as raw materials is divided into three steps:

[0008] In the first step, acetaldehyde and acrylate undergo Baylis-Hillman reaction in the presence of triethylenediamine catalyst to produce enester;

[0009] In the second step, the first step product, the enester, and ethyl acrylate undergo dehydration and Diels-Alder reaction in the presence of an acid catalyst to obtain cyclohexene dicarboxylate;

[0010] In the third step, cyclohexene dicarboxylic acid ester undergoes dehydrogenation reaction in the presence of a metal catalyst to generate phthalic acid ester.

[0011] Based on the above scheme, preferably, in the second step reaction, adding a polymerization inhibitor can improve the yield of cyclohexene dicarboxylic acid ester. The polymerization inhibitor is one of 2,6-di-tert-butyl-4-methylphenol, 2,2,6,6-tetramethylpiperidinyl oxide, p-hydroxyanisole, and hydroquinone; and the molar ratio of the polymerization inhibitor to the enester produced by the first step reaction is 0.01-0.2.

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

[0013] The first step is carried out under solvent-free conditions;

[0014] In the second step, the reaction medium is an organic solvent; the organic solvent is one of cyclohexane, ethylene glycol, and N,N-dimethylformamide;

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

[0016] Based on the above scheme, preferably, the catalyst and conditions required for each step of the reaction are 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; wherein the molar ratio of the acid catalyst to the enester produced by the first step is 0.05-4;

[0019] In the third step, the metal catalyst used has precious metals as active components and carbon materials as carriers.

[0020] As a further preference of the above scheme, the catalyst and conditions required for each step of the reaction are as follows:

[0021] In the second step, 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 enester generated in the first reaction is 1-4, preferably 3-4; when the acid catalyst is other types mentioned above, the molar ratio of the added acid catalyst to the enester generated in the first reaction is 0.05-0.2, preferably 0.1-0.2;

[0022] In the third step, the metal catalyst used is one of Pd / C and Ru / C.

[0023] Based on the above scheme, preferably, the specific reaction conditions of each step are as follows:

[0024] 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 hours;

[0025] In the second step, the molar ratio of ethyl acrylate to the olefin ester 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 hours;

[0026] In the third step, the dehydrogenation reaction temperature is between 180-260℃ and the space velocity is between 2.3-6.3h -1 between.

[0027] As a further preference of the above scheme, the specific reaction conditions of each step are as follows:

[0028] In the first step, 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 hours;

[0029] In the second step, the molar ratio of ethyl acrylate to the olefin ester product of the first step is between 2-3; the reaction temperature is between 140-160°C, and the reaction time is between 10-14 hours;

[0030] In the third step, the dehydrogenation reaction temperature is between 200-240℃ and the space velocity is between 4.3-6.3h -1 between.

[0031] The present invention has the following advantages:

[0032] Traditional synthetic routes use petroleum resources as raw materials, but fossil resources are becoming increasingly depleted, and the production process releases carbon dioxide, polluting the environment. The plasticizer synthesis route provided by the present invention is environmentally friendly, using renewable biomass platform compounds as starting materials, and the dehydration and DA reactions can be carried out in a single step. The reaction conditions are simple, the catalyst is readily available, and the cost is low. Therefore, the present invention is a biomass-based method for synthesizing plasticizers with great industrial potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 GC spectrum of the Reese-Hillman reaction of acetaldehyde and ethyl acrylate catalyzed by triethylenediamine;

[0034] Figure 2 GC spectrum of diethyl cyclohexene dicarboxylate prepared from cyclohexene ester and ethyl acrylate;

[0035] Figure 3 GC spectrum of the dehydrogenation reaction of dimethyl cyclohexene dicarboxylate to prepare phthalate esters;

[0036] Figure 4 The product of Baylis-Hillman reaction of acetaldehyde and ethyl acrylate catalyzed by triethylenediamine 1 H-NMR spectrum;

[0037] Figure 5 The product of Baylis-Hillman reaction of acetaldehyde and ethyl acrylate catalyzed by triethylenediamine 13 C-NMR spectrum;

[0038] Figure 6 . Cyclohexene dicarboxylic acid diethyl ester prepared from ethyl acrylate 1 H-NMR spectrum;

[0039] Figure 7 . Cyclohexene dicarboxylic acid diethyl ester prepared from ethyl acrylate 13 C-NMR spectrum;

[0040] Figure 8 . The product of phthalate prepared by dehydrogenation of dimethyl cyclohexene dicarboxylate 1 H-NMR spectrum;

[0041] Figure 9 . The product of phthalate prepared by dehydrogenation of dimethyl cyclohexene dicarboxylate 13 C-NMR spectrum;

[0042] Figure 10 .Reaction route for the preparation of phthalates using acetaldehyde and ethyl acrylate as raw materials. DETAILED DESCRIPTION

[0043] The present invention will be described below with reference to specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0044] 1. Acetaldehyde and ethyl acrylate undergo Baylis-Hillman reaction in the presence of triethylenediamine (DABCO) catalyst to generate enester

[0045] In a 35 mL test tube, catalyst, acetaldehyde and ethyl acrylate were added in sequence to react.

[0046]

[0047] Table 1. Effect of reaction conditions on the reaction

[0048]

[0049]

[0050] As can be seen from the results in Table 1, when 10 mol% triethylenediamine catalyst is added, no solvent is present, at 25°C, the molar ratio of acetaldehyde to ethyl acrylate is 1.5:1, and the reaction time is 72 hours, the yield of the enester can reach 96%. If the reaction time is 96 hours, the yield can reach 97%.

[0051] 2. One-step dehydration and Diels-Alder reaction of olefin ester and ethyl acrylate

[0052] In a 35 mL test tube, add enester 3 and ethyl acrylate 2, then add a catalyst, an inhibitor hydroquinone (1 mol%), and a reaction solvent (3 mL). The reaction is carried out at a certain temperature to obtain diethyl cyclohexenedicarboxylate 4a and 4b.

[0053]

[0054] Table 2. Effects of different conditions on dehydration / DA reaction

[0055]

[0056]

[0057]

[0058] As can be seen from the results in Table 2, when 350 mol% HCOOH catalyst, 1 mol% hydroquinone inhibitor were added, N,N-dimethylformamide was used as the reaction medium, the molar ratio of the olefin ester to ethyl acrylate generated in the first step was 1:2, and the reaction was carried out for 12 hours, the yield of cyclohexene dicarboxylic acid ester could reach 75%.

[0059] 3. (1) Dehydrogenation of diethyl cyclohexenedicarboxylates 4a and 4b

[0060] Using a fixed bed as a reactor, ethyl acetate solutions (2 wt%) of diethyl cyclohexenedicarboxylates 4a and 4b were added, followed by a catalyst. The nitrogen pressure was normal pressure, and the reactions were carried out at different temperatures to obtain phthalates 5a and 5b.

[0061]

[0062] Table 3. Effect of reaction conditions on dehydrogenation reaction

[0063]

[0064]

[0065] From the results in Table 3, it can be seen that with Pd / C as catalyst, ethyl acetate as reaction medium, normal pressure nitrogen, 240℃, and space velocity of 6.3h -1 Under the following reaction conditions, the yield of the target product phthalate can reach 91%.

Claims

1. A method for preparing phthalic acid esters, characterized in that: The preparation of phthalates is divided into three steps: In the first step, acetaldehyde 1 and ethyl acrylate 2 undergo Baylis-Hillman reaction in the presence of triethylenediamine catalyst to produce enester 3; In the second step, the first-step product, olefin ester 3, and ethyl acrylate undergo dehydration and Diels-Alder reaction in the presence of an acid catalyst, to obtain cyclohexenedicarboxylates 4a and 4b; the acid catalyst is a Lewis acid or a Bronsted acid. In the third step, cyclohexenedicarboxylates 4a and 4b are dehydrogenated in the presence of a metal catalyst to produce phthalates 5a and 5b; the metal catalyst used is Pd / C. 。 2. The method for preparing phthalate according to claim 1, wherein: The second step reaction is carried out under the condition of adding a polymerization inhibitor; the molar ratio of the polymerization inhibitor to the enester 3 generated in the first step reaction is 0.01-0.

2.

3. The method for preparing phthalate according to claim 1, wherein: In the first step, the reaction is carried out under solvent-free conditions; In the second step, the reaction medium is an organic solvent; the organic solvent is one of cyclohexane, ethylene glycol, and N,N-dimethylformamide; In the third step, the solvent used is ethyl acetate.

4. The method for preparing phthalate according to claim 1, wherein: In the first step, the molar ratio of the triethylenediamine catalyst to the reaction substrate acetaldehyde 1 is 0.05-0.

2.

5. The method for preparing phthalate according to claim 4, wherein: In the second step, 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, CF3SO3H, or CF3SO3H, the molar ratio of the added acid catalyst to the enester 3 generated in the first reaction is 1-4; when the acid catalyst is other types, the molar ratio of the added acid catalyst to the enester 3 generated in the first reaction is 0.05-0.

2.

6. The method for preparing phthalate according to claim 1, wherein: In the first step, the molar ratio of the substrate acetaldehyde 1 to ethyl acrylate 2 is 0.5-2; the reaction temperature is 20-40°C, and the reaction time is between 24-96 hours; In the second step, the molar ratio of ethyl acrylate to the first step product, olefin ester 3, is between 0.5 and 5; the reaction temperature is between 120 and 180° C., and the reaction time is between 6 and 18 hours; In the third step, the dehydrogenation reaction temperature is between 180-260℃ and the space velocity is between 2.3-6.3h -1 between.

7. The method for preparing phthalate according to claim 6, wherein: In the first step, the molar ratio of substrate acetaldehyde 1 to ethyl acrylate 2 is 1:1-2:1; the reaction temperature is 20-30°C, and the reaction time is between 72-96 hours; In the second step, the molar ratio of ethyl acrylate to the first step product, olefin ester 3, is between 2 and 3; the reaction temperature is between 140 and 160° C., and the reaction time is between 10 and 14 hours; In the third step, the dehydrogenation reaction temperature is between 200-240℃ and the space velocity is between 4.3-6.3h -1 between.

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