Esterification reaction method

Abstract

The present invention provides an esterification reaction method, which comprises that two or more hydroxyl groups in a polyol molecule and an organic acid are subjected to an esterification reaction in the presence of a catalyst to prepare an esterification product, and the catalyst comprises an ionic liquid and a carrier; the polyol comprises at least three hydroxyl groups and contains 3 to 16 carbon atoms; and the organic acid is C3-C18 saturated carboxylic acid or unsaturated carboxylic acid. The method provided by the invention adopts a newly designed catalyst, realizes excellent catalytic performance, can prepare a high-quality target esterification product with high yield, significantly inhibits the generation of by-products, and also can avoid corrosion to reaction equipment, efficiently recover and reuse the catalyst, and avoid the problems of wastewater generation and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysis, and particularly relates to a method for catalyzing esterification reaction by using polyol as raw material. BACKGROUND

[0002] Esters formed by polyol and organic carboxylic acid have a wide range of uses. For example, pentaerythritol triacrylate (PET3A) formed by esterification reaction of pentaerythritol and acrylic acid is a typical representative, which is an important functional monomer and is widely used in the fields of photocuring coating, ink, adhesive and the like, and has a great demand in various fields.

[0003] However, in contrast to the great demand, the synthesis method of polyol esters represented by PET3A has always been unsatisfactory. For example, the catalyst used in the esterification method for preparing PET3A often leads to significant side reactions (such as carbonization, dehydration, etc.), which seriously affects the yield and purity of the target product; the catalysts such as concentrated sulfuric acid, methane sulfonic acid and p-toluene sulfonic acid used will cause serious corrosion to the reaction equipment, and after the esterification reaction, complex post-treatment operations (such as neutralization, water washing, etc.) are required, and the catalyst cannot be recovered, which further reduces the economy, practicability and environmental protection of the production process. Although relevant enterprises and research institutions have invested a lot of funds and efforts in research, they have always failed to effectively overcome the above problems, and there is a great need to develop a new process which can overcome the above defects.

[0004] Ionic liquids have the advantages of low volatility, high thermal stability and designability, and are considered as an ideal green catalyst. However, in esterification reaction, homogeneous ionic liquid still has problems such as separation difficulty, poor reusability, high viscosity and limited mass transfer. In recent years, supported ionic liquid catalysts have become a hot spot in green chemistry research due to their unique designability, high catalytic activity and easy recovery. By immobilizing functional ionic liquids on porous carriers such as silica, molecular sieves or polymers, the high catalytic efficiency of ionic liquids can be retained, and the recycling of heterogeneous catalysts can be realized, which significantly reduces the cost of industrial production. However, the early supported ionic liquid catalysts prepared by physical adsorption method have a high loss rate of ionic liquid, and the catalyst activity decreases by more than 30% after 3 cycles. Therefore, it is necessary to develop a supported ionic liquid formed by chemical bonding to realize the strong interaction between the carrier and the ionic liquid and reduce the loss of ionic liquid during the use of the catalyst. SUMMARY

[0005] In view of the above problems, the inventors of the present application have successfully developed a brand new esterification reaction method, which unexpectedly solves the problems in the prior art.

[0006] The present application provides an esterification method, which comprises esterifying two or more hydroxyl groups in a polyol molecule with an organic acid in the presence of a catalyst to produce an esterification product, characterized in that,

[0007] The catalyst comprises an ionic liquid and a carrier;

[0008] The polyol comprises at least three hydroxyl groups and contains 3-16 carbon atoms;

[0009] The organic acid is a C3-C18 saturated carboxylic acid or an unsaturated carboxylic acid.

[0010] According to one embodiment of the present application, the ionic liquid contains a cation and an anion. According to another embodiment of the present application, the cation is selected from at least one of imidazolium ion, pyrrolidinium ion, pyridinium ion, phosphonium ion, quaternary ammonium ion. According to another embodiment of the present application, the anion is selected from at least one of halide, aluminate, chloroaluminate, tetrafluoroborate, hexafluorophosphate, sulfate, bisulfate, sulfonate, hydrogenphosphate, dihydrogenphosphate, carboxylate, fluorocarboxylate, chlorocarboxylate, chlorometalate, and a complex anion formed by two or more of the above.

[0011] According to another embodiment of the present application, the ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium chloroaluminate, 1-(3-sulfopropyl)-3-methylimidazolium bisulfate, 1-(3-sulfopropyl)-triethylammonium bisulfate, 1-ethyl-3-methylimidazolium bisulfate, 1-ethyl-3-methylimidazolium hydrogenphosphate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-(3-sulfopropyl)-3-methylimidazolium chlorozincate.

[0012] According to another embodiment of the present application, the carrier in the catalyst has a porous structure and is selected from one or more of silica, alumina, aluminosilicate, zeolite, molecular sieve.

[0013] According to another embodiment of the present application, the content of the ionic liquid in the catalyst is 10-90% by weight, based on the total weight of the catalyst.

[0014] According to another embodiment of the present application, the catalyst is prepared by mixing raw materials for forming a carrier with an ionic liquid, and then reacting the raw materials for forming a carrier in the presence of the ionic liquid to form a carrier having a porous structure, and the ionic liquid is at least partially combined or adsorbed in the porous structure and / or on the surface of the carrier.

[0015] According to another embodiment of the present application, the raw material for forming the carrier includes a silicon source and / or an aluminum source, and the carrier with a porous structure is formed by hydrolysis reaction, condensation reaction and / or self-assembly reaction.

[0016] According to another embodiment of the present application, the polyol is selected from at least one of pentaerythritol, glycerol, trimethylol ethane, trimethylol propane, xylitol, sorbitol.

[0017] According to another embodiment of the present application, the organic acid is selected from at least one of acrylic acid, methacrylic acid, oleic acid, undecylenic acid.

[0018] According to another embodiment of the present application, the esterification reaction further uses one or more of a polymerization inhibitor, an antioxidant, a solvent.

[0019] According to another embodiment of the present application, the polymerization inhibitor is selected from at least one of phenothiazine, hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-p-cresol, 2-tert-butyl-hydroquinone, p-benzoquinone, methylhydroquinone and chloranil.

[0020] According to another embodiment of the present application, the antioxidant is selected from at least one of hypophosphorous acid and sodium hypophosphite.

[0021] According to another embodiment of the present application, the solvent is selected from at least one of cyclohexane, toluene, benzene, n-heptane, n-hexane.

[0022] According to another embodiment of the present application, the ratio of the molar amount of the polyol to the molar amount of the organic acid in the esterification reaction is 1:3 to 1:20.

[0023] According to another embodiment of the present application, the amount of the catalyst added is 4.0-8.0 wt%, the amount of the polymerization inhibitor added is 0.4-0.8 wt%, and the amount of the antioxidant added is 0.5-1.0 wt%, based on the total weight of all the materials (excluding the solvent) added to the esterification reaction.

[0024] According to another embodiment of the present application, the amount of the solvent added is 100-150 parts by weight, based on 100 parts by weight of the total weight of all the materials (excluding the solvent) added to the esterification reaction.

[0025] In the detailed description of the application hereafter, the method and the polymer product of the present application are further described with reference made to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 SEM images of the supported catalyst synthesized according to the embodiments of the present application are shown.

[0027] Figure 2 A gas chromatogram of the esterification product synthesized according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0028] The ranges disclosed herein are presented in the form of a lowest value and a highest value. There can be one or more lower values and one or more upper values. A given range is defined by selecting a lower value and an upper value. The selected lower and upper values define the boundaries of a particular range. All ranges defined in this manner are inclusive and combinable, i.e., any lower value can be combined with any upper value to form a range. For example, where ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4 and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0029] In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing each and every individual number that is within the range, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers within the range "0-5" have been listed herein, and "0-5" is merely a shorthand way of describing those numerical combinations.

[0030] In the present application, unless otherwise stated, all embodiments and preferred embodiments mentioned herein can be combined with each other to form new technical solutions.

[0031] In the present application, unless otherwise stated, all technical features and preferred features mentioned herein can be combined with each other to form new technical solutions.

[0032] In the present application, unless otherwise stated, "comprising" mentioned herein indicates an open-ended, and can also be closed. For example, the "comprising" can indicate that it can also contain other components not listed, or can only include the listed components.

[0033] According to an embodiment of the present application, the esterification reaction is an esterification reaction of two or more hydroxyl groups in the polyol with the organic acid to generate the esterification product.

[0034] According to one embodiment of the present application, the polyol used in the esterification reaction contains at least three hydroxyl groups and 3-16 carbon atoms per molecule. According to one specific embodiment of the present application, the polyol contains 3-16 hydroxyl groups per molecule, or 3-12 hydroxyl groups, or 3-6 hydroxyl groups, or 3, 4 or 5 hydroxyl groups. According to another specific embodiment of the present application, the polyol contains 3-16 carbon atoms per molecule, such as 3-12 carbon atoms, or 3-8 carbon atoms, or 4-6 carbon atoms. According to another specific embodiment of the present application, the polyol is selected from at least one of the following: pentaerythritol, glycerol, trimethylol ethane, trimethylol propane, xylitol, sorbitol; preferably pentaerythritol.

[0035] According to another embodiment of the present application, the organic acid used in the esterification reaction includes saturated carboxylic acids (i.e. no carbon-carbon double or triple bonds in the molecule) and unsaturated carboxylic acids (i.e. one or more carbon-carbon double or triple bonds in the molecule). The organic acid contains 3-18 carbon atoms per molecule, such as 3-15 carbon atoms, or 3-12 carbon atoms, or 3-9 carbon atoms, or 3-6 carbon atoms. The organic acid contains one, two, three, four, five or six carboxyl groups per molecule, preferably 1-3 carboxyl groups, more preferably one carboxyl group. According to one preferred embodiment of the present application, the organic acid is acrylic acid, methacrylic acid, oleic acid (octadec-9-enoic acid), undecylenic acid (undec-10-enoic acid), or a combination of two or more thereof.

[0036] According to one embodiment of the present application, in the esterification reaction, at least one of the hydroxyl groups in the polyol is not esterified.

[0037] According to one specific embodiment of the present application, in the esterification reaction, the polyol is pentaerythritol, the organic acid is acrylic acid or methacrylic acid, and three hydroxyl groups in the pentaerythritol are esterified to form the target product pentaerythritol tri(meth)acrylate, such as PET3A. The method of the present application is illustrated below by way of example using the synthesis of PET3A, but the scope of protection of the present application is not limited thereto.

[0038] The catalyst used in the esterification reaction method of the present application is a supported catalyst, which contains a solid carrier component and an ionic liquid component supported on the carrier.

[0039] According to one embodiment of the present application, the ionic liquid comprises a cation and an anion. The cation is selected from at least one of imidazolium ion, pyrrolidinium ion, pyridinium ion, phosphonium ion, quaternary ammonium ion. For the above imidazolium ion, pyrrolidinium ion, pyridinium ion, one or more substituents can be optionally attached to the imidazole ring, pyrrole ring and pyridine ring structure (e.g. to the ring carbon atoms, ring nitrogen atoms) as needed, the phosphonium ion, quaternary ammonium ion can be attached with different substituents as needed, the substituents can be selected from one or more of the following: C1-C12 alkyl, C1-C12 alkoxy, halogen, C1-C12 haloalkyl, C3-C16 cycloalkyl, C6-C16 aryl, sulfonic acid-C1-C12 alkyl, carboxylic acid-C1-C12 alkyl, halogenated C1-C12 alkyl.

[0040] According to another embodiment of the present application, the anion is selected from at least one of halide, aluminate, chloroaluminate, tetrafluoroborate, hexafluorophosphate, sulfate, bisulfate, sulfonate, hydrogenphosphate, dihydrogenphosphate, carboxylate, fluorocarboxylate, chlorocarboxylate, chlorometalate, and a complex anion formed by two or more of the above.

[0041] In the present application, halogen includes fluorine, chlorine, bromine, iodine; halo includes fluoro, chloro, bromo, iodo; halide includes fluoride, chloride, bromide, iodide.

[0042] According to one embodiment of the present application, the chlorometalate is selected from one or more of chlorozincate, chlorocobaltate, chlorochromate, chlorostannate, chloroplatinate, chloroaurate.

[0043] According to one exemplary embodiment of the present application, the ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium chloroaluminate, 1-(3-sulfopropyl)-3-methylimidazolium bisulfate, 1-(3-sulfopropyl)-triethylammonium bisulfate, 1-ethyl-3-methylimidazolium bisulfate, 1-ethyl-3-methylimidazolium dihydrogenphosphate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-(3-sulfopropyl)-3-methylimidazolium chlorozincate.

[0044] According to another embodiment of the present application, the solid support in the catalyst has a porous structure, such as microporous structure (pore size less than 1 nanometer), mesoporous structure (pore size between 1-1000 nanometers), macroporous structure (pore size greater than 1000 nanometers, i.e. greater than 1 micrometer), or the solid support can comprise any two or three of the above microporous structure, mesoporous structure, macroporous structure at the same time. According to one preferred embodiment, the solid support comprises at least mesoporous structure.

[0045] According to another embodiment of the present application, the solid support in the catalyst comprises one or more of the following materials: silica, alumina, aluminosilicate, zeolite, molecular sieve.

[0046] According to one embodiment of the present application, the content of the ionic liquid in the catalyst is 10-90 wt%, for example 30-85 wt%, or 50-80 wt%, or 60-75 wt%, or 70-75 wt%, based on the total weight of the catalyst.

[0047] According to another embodiment of the present application, the catalyst is prepared by mixing raw materials for forming a support with an ionic liquid, and then allowing the raw materials for forming a support to react in the presence of the ionic liquid to form a support having a porous structure, and the ionic liquid is at least partially incorporated or adsorbed in the porous structure and / or on the surface of the support. According to a further embodiment, the raw materials for forming a support include a silicon source and / or an aluminum source, and a support having a porous structure is formed by allowing hydrolysis reaction, condensation reaction and / or self-assembly reaction to occur.

[0048] Specific examples of the silicon source include various silicates (e.g. tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, etc.), silicates (e.g. sodium silicate), water glass, silica gel, silicon tetrachloride, silicon trichlorohydride, white carbon black, siloxane, etc. Specific examples of the aluminum source include alkyl aluminum (e.g. methyl aluminum, ethyl aluminum, sec-butyl aluminum), alkyl aluminum oxide (e.g. isopropyl aluminum oxide), organic aluminum salt (e.g. aluminum acetate, aluminum stearate), inorganic aluminum salt (e.g. aluminum chloride, aluminum sulfate, polyaluminum sulfate), aluminum oxide (e.g. alumina, hydrated alumina, bauxite, pseudo-boehmite), etc.

[0049] According to one exemplary embodiment of the present application, the catalyst of the present application is prepared by mixing an ionic liquid (e.g. 1-butyl-3-methylimidazolium chloroaluminate) and raw materials for preparing a solid support (e.g. tetraethyl orthosilicate) in a reaction kettle, so that the mass ratio of the ionic liquid to the raw materials for preparing a solid support is 1:1 to 1:6, or 1:2 to 1:5, or 1:2.5 to 1:3; and allowing the mixed reaction materials to react under heating conditions to obtain the desired supported catalyst. According to one embodiment of the present application, an organic solvent such as methanol, ethanol, propanol, butanol, etc. can be added to the reaction kettle as needed. According to another embodiment of the present application, the above reaction can be carried out at a pH of 3-4. According to another embodiment of the present application, the reaction temperature can be 40-120°C, for example 50-100°C, or 60-70°C. After the above reaction is carried out, the reaction product is dried to obtain the supported catalyst.

[0050] According to another embodiment of the present application, other additives such as surfactants, templates, stabilizers, pH adjusters, activity promoters, pore-forming agents, etc. can also be added as needed when preparing the supported catalyst.

[0051] The esterification method of the present application comprises adding the catalyst, polyol and organic acid described above into an esterification reactor, so that the two or more hydroxyl groups in the polyol are esterified with the organic acid. According to one embodiment of the present application, the molar ratio of the polyol to the organic acid fed into the esterification reaction is 1:3 to 1:20; for example, the molar ratio is 1:3 to 1:16; or the molar ratio is 1:3 to 1:12; or the molar ratio is 1:3 to 1:8; or the molar ratio is 1:3 to 1:6; or the molar ratio is 1:3 to 1:5.

[0052] According to one embodiment of the present application, in addition to the catalyst, polyol and organic acid described above, one or more of the following components can also be added into the esterification reactor: polymerization inhibitor, antioxidant, solvent, etc.

[0053] The amount of catalyst added is 4.0-8.0% by weight, the amount of polymerization inhibitor added is 0.4-0.8% by weight, and the amount of antioxidant added is 0.5-1.0% by weight, based on the total weight of all materials (excluding solvent) fed into the esterification reaction (i.e. based on the total weight of the catalyst, polyol, organic acid, and possibly added polymerization inhibitor and antioxidant fed into the esterification reactor);

[0054] The amount of solvent added is 100-150 parts by weight, based on 100 parts by weight of the total weight of all materials (excluding solvent) fed into the esterification reaction.

[0055] According to one embodiment of the present application, the polymerization inhibitor is selected from at least one of the following: phenothiazine, hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-p-cresol, 2-tert-butyl-hydroquinone, p-benzoquinone, methylhydroquinone and chloranil.

[0056] According to another embodiment of the present application, the antioxidant is selected from at least one of the following: hypophosphorous acid, sodium hypophosphite.

[0057] According to another embodiment of the present application, the solvent is selected from at least one of the following: cyclohexane, toluene, benzene, n-heptane, n-hexane.

[0058] According to another embodiment of the present application, air can also be continuously introduced during the esterification reaction. For example, the flow rate of air can be 50-100 mL / min.

[0059] According to another embodiment of the present application, the reaction temperature of the esterification reaction is 80-130°C, for example 100-120°C.

[0060] According to an exemplary embodiment of the present application, the esterification method of the present application is performed by the following steps: adding polyol (for example, pentaerythritol), organic acid (for example, acrylic acid), catalyst, polymerization inhibitor, antioxidant and solvent into a reaction kettle for performing esterification reaction; continuously feeding air into the kettle; heating to the esterification temperature to start the esterification reaction; performing reflux dehydration during the esterification reaction; when the reaction kettle can no longer reflux water, it indicates that the esterification reaction has ended; after cooling the liquid in the reaction kettle to room temperature, filtering to recover the catalyst; after treating the organic phase with solid basic adsorbent, removing the solvent by vacuum distillation, and finally obtaining the target esterification product by filtration.

[0061] The beneficial effects of the present application mainly lie in that the catalyst of the present application can achieve excellent catalytic effect, promote the progress of esterification reaction, obtain the target esterification product with high purity at excellent yield, reduce the generation of by-products, reduce the generation of waste water and waste materials, have excellent environmental protection performance, and the catalyst can be conveniently recovered and recycled, and the recycled catalyst retains excellent catalytic activity.

[0062] In the following examples, the method of the present application is introduced by taking the reaction of pentaerythritol and acrylic acid to synthesize PET3A as an example.

[0063] Embodiments

[0064] The 1-butyl-3-methylimidazolium chloroaluminate ionic liquid used in the following examples was purchased from Shanghai Titan Science and Technology Co., Ltd., tetraethyl orthosilicate was purchased from Alfa Aesar (China) Chemical Co., Ltd., and all other reagents were commercially available analytical reagents without further treatment. The water used in the following examples was deionized water.

[0065] Example 1

[0066] In this example, the synthesis of the catalyst of the present application was performed by the following steps.

[0067] Into a reaction kettle, 31 g of 1-butyl-3-methylimidazolium chloroaluminate ionic liquid and 83 g of tetraethyl orthosilicate were added and mixed thoroughly, then 120 mL of anhydrous ethanol was added into the reaction kettle, the reaction kettle was heated to 60°C, and the stirring was continued for 3 hours at this temperature. Then the pH value of the solution formed in the reaction kettle was adjusted to about 3.5 using hydrochloric acid with a concentration of 0.1 M, and the stirring was continued for 5 hours, during which the pH value of the material in the reaction kettle was continuously monitored, and the pH value was maintained at about 3.5. Then the stirring was stopped, and the material in the reaction kettle was left to stand and age overnight. A gel was formed in the reaction kettle, which was transferred into a vacuum drying oven, and dried at a temperature of 100°C for 6 hours under vacuum to obtain a solid product. The specific surface area of the product was measured to be 758 m 2 / g using an Autosorb-1-C chemisorption / physiosorption analyzer produced by Quantachrome Instruments, USA.

[0068] The solid product was characterized by scanning electron microscopy (SEM), and as shown in FIG. 1, it was indicated that a porous silica-supported ionic liquid catalyst was prepared. Figure 1

[0069] Example 2

[0070] In this example, the esterification reaction was carried out using the catalyst prepared in Example 1.

[0071] Specifically, into a reaction kettle for carrying out the esterification reaction, 136 g of pentaerythritol, 216 g of acrylic acid, 2 g of p-hydroxyanisole, 18 g of the catalyst prepared in Example 1, 2 g of hypophosphorous acid, and 400 g of cyclohexane were added, and the stirring device was started to mix the materials in the reaction kettle thoroughly. Air was continuously introduced into the reaction kettle at a flow rate of 50 mL / min, and the reaction kettle was heated so that the temperature of the reaction kettle was increased to 120°C, and the continuous reflux dehydration was carried out as the esterification reaction proceeded. After the reaction was continued for 4 hours, no water was removed any more, at which time the esterification reaction was stopped, the temperature of the reaction kettle was decreased to room temperature, and then the materials in the reaction kettle were taken out and filtered to recover the catalyst therein. The organic phase was treated with 10 g of a solid basic adsorbent (purchased from Shanghai Adamas Reagent Co., Ltd.) for 2 hours, and then filtered again to remove the adsorbent. The organic phase was collected, and the solvent was removed by distillation under reduced pressure at 80°C. The colorless transparent product was obtained by filtering again. The yield was calculated by weighing to be 98%.

[0072] The colorless transparent product was characterized by gas chromatography, and as shown in FIG. 2, it was proved to be a pentaerythritol acrylate mixture (containing pentaerythritol monoacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate (PET3A), and pentaerythritol tetraacrylate), in which the content of pentaerythritol triacrylate (PET3A) as the target product was 62.5%. Figure 2 ​​

[0073] Example 3

[0074] In this example, the esterification reaction was carried out again (the third round of esterification reaction) using the catalyst which was reacted, recovered, washed and dried in Example 3.

[0075] Specifically, 136 grams of pentaerythritol, 216 grams of acrylic acid, 2 grams of p-hydroxyanisole, 18 grams of the catalyst recovered from Example 2, 2 grams of hypophosphorous acid and 400 grams of cyclohexane were added into the reaction kettle for esterification reaction, the stirring device was started to mix the materials in the reaction kettle thoroughly. Air was continuously introduced into the reaction kettle at a flow rate of 50 mL / min, the reaction kettle was heated so that the temperature of the reaction kettle rose to 120°C, and continuous reflux dehydration was carried out as the esterification reaction proceeded. After the reaction continued for 4 hours, no water was removed any more, at which time the esterification reaction was stopped, the temperature of the reaction kettle was lowered to room temperature, and then the materials in the reaction kettle were taken out, the catalyst was recovered by filtration, the organic phase was treated with 10 grams of solid basic adsorbent (purchased from Shanghai Adamas Reagent Co., Ltd.) for 2 hours, then filtered again to remove the adsorbent, the organic phase was collected, and the solvent was removed by distillation under reduced pressure at 80°C, and the colorless transparent product was obtained by filtration again. Its weight was calculated to have a yield of 98%.

[0076] The colorless transparent product was characterized by gas chromatography, which proved to be a pentaerythritol acrylic acid ester mixture (containing pentaerythritol monoacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate (PET3A) and pentaerythritol tetraacrylate), in which the content of pentaerythritol triacrylate (PET3A) as the target product was 62.3% by weight.

[0077] Example 4

[0078] In this example, the esterification reaction was carried out again (the third round of esterification reaction) using the catalyst which was reacted, recovered, washed and dried in Example 3.

[0079] Specifically, 136 grams of pentaerythritol, 216 grams of acrylic acid, 2 grams of p-hydroxyanisole, 18 grams of the catalyst recovered from Example 3, 2 grams of hypophosphorous acid and 400 grams of cyclohexane were added to a reaction kettle for esterification reaction, and the stirring device was started to mix the materials in the reaction kettle thoroughly. Air was continuously introduced into the reaction kettle at a flow rate of 50 mL / min, and the reaction kettle was heated so that the temperature of the reaction kettle rose to 120°C. As the esterification reaction proceeded, continuous reflux dehydration was carried out. After the reaction continued for 4 hours, no water was released any more, at which point the esterification reaction was stopped, the temperature of the reaction kettle was lowered to room temperature, and then the materials in the reaction kettle were taken out, the catalyst therein was recovered by filtration, the organic phase was treated with 10 grams of solid basic adsorbent (purchased from Shanghai Adamas Reagent Co., Ltd.) for 2 hours, and then filtration was carried out again to remove the adsorbent. The organic phase was collected, and the solvent was removed by distillation under reduced pressure at 80°C. Filtration again gave colorless transparent product. Its weight was taken to calculate the yield as 97%.

[0080] The colorless transparent product was characterized by gas chromatography, which proved to be a pentaerythritol acrylic acid ester mixture (containing pentaerythritol monoacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate (PET3A) and pentaerythritol tetraacrylate), wherein the content of pentaerythritol triacrylate (PET3A) as the target product was 62.0% by weight.

[0081] Example 5

[0082] In this example, the esterification reaction was carried out again (the fourth round of esterification reaction) using the catalyst that had been reacted in Example 4 and recovered, washed and dried.

[0083] Specifically, 136 grams of pentaerythritol, 216 grams of acrylic acid, 2 grams of p-hydroxyanisole, 18 grams of the catalyst recovered from Example 4, 2 grams of hypophosphorous acid and 400 grams of cyclohexane were added to a reaction kettle for esterification reaction, and the stirring device was started to mix the materials in the reaction kettle thoroughly. Air was continuously introduced into the reaction kettle at a flow rate of 50 mL / min, and the reaction kettle was heated so that the temperature of the reaction kettle rose to 120°C. As the esterification reaction proceeded, continuous reflux dehydration was carried out. After the reaction continued for 4 hours, no water was released any more, at which point the esterification reaction was stopped, the temperature of the reaction kettle was lowered to room temperature, and then the materials in the reaction kettle were taken out, the catalyst therein was recovered by filtration, the organic phase was treated with 10 grams of solid basic adsorbent (purchased from Shanghai Adamas Reagent Co., Ltd.) for 2 hours, and then filtration was carried out again to remove the adsorbent. The organic phase was collected, and the solvent was removed by distillation under reduced pressure at 80°C. Filtration again gave colorless transparent product. Its weight was taken to calculate the yield as 96%.

[0084] The colorless transparent product was characterized using gas chromatography, proving it to be a pentaerythritol acrylate mixture (containing pentaerythritol monoacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate (PET3A) and pentaerythritol tetraacrylate), wherein the content of pentaerythritol triacrylate (PET3A) as the target product was 61.6% by weight.

[0085] Example 6

[0086] In this example, the esterification reaction was carried out again using the catalyst that had been reacted, recovered, washed and dried in Example 5 (fifth round of esterification reaction).

[0087] Specifically, 136 grams of pentaerythritol, 216 grams of acrylic acid, 2 grams of p-hydroxyanisole, 18 grams of the catalyst recovered from Example 5, 2 grams of hypophosphorous acid and 400 grams of cyclohexane were added to the reaction kettle used for the esterification reaction, the stirring device was started and the materials in the reaction kettle were mixed thoroughly. Air was continuously introduced into the reaction kettle at a flow rate of 50 mL / min, the reaction kettle was heated so that the temperature of the reaction kettle rose to 120°C, and continuous reflux dehydration was carried out as the esterification reaction proceeded. After the reaction continued for 4 hours, no more water was removed, at which point the esterification reaction was stopped, the temperature of the reaction kettle was lowered to room temperature, and then the materials in the reaction kettle were taken out, the catalyst therein was recovered by filtration, the organic phase was treated with 10 grams of solid basic adsorbent (purchased from Shanghai Adamas Reagent Co., Ltd.) for 2 hours, then filtered again to remove the adsorbent, the organic phase was collected, and the solvent was removed by distillation under reduced pressure at 80°C, and the colorless transparent product was obtained by filtration again. The yield was calculated by weighing to be 95%.

[0088] The colorless transparent product was characterized using gas chromatography, proving it to be a pentaerythritol acrylate mixture (containing pentaerythritol monoacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate (PET3A) and pentaerythritol tetraacrylate), wherein the content of pentaerythritol triacrylate (PET3A) as the target product was 61.2% by weight.

[0089] Example 7

[0090] In this example, the esterification reaction was carried out again using the catalyst that had been reacted, recovered, washed and dried in Example 6 (sixth round of esterification reaction).

[0091] Specifically, 136 grams of pentaerythritol, 216 grams of acrylic acid, 2 grams of p-hydroxyanisole, 18 grams of the catalyst recovered from Example 6, 2 grams of hypophosphorous acid and 400 grams of cyclohexane were added to a reaction kettle for esterification reaction, the stirring device was started to mix the materials in the reaction kettle thoroughly. Air was continuously introduced into the reaction kettle at a flow rate of 50 mL / min, the reaction kettle was heated to raise the temperature of the reaction kettle to 120°C, and continuous reflux dehydration was carried out as the esterification reaction proceeded. After the reaction continued for 4 hours, no water was removed any more, at which time the esterification reaction was stopped, the temperature of the reaction kettle was lowered to room temperature, and then the materials in the reaction kettle were taken out, the catalyst was recovered by filtration, the organic phase was treated with 10 grams of solid basic adsorbent (purchased from Shanghai Adamas Reagent Co., Ltd.) for 2 hours, then filtration was carried out again to remove the adsorbent, the organic phase was collected, and the solvent was removed by distillation under reduced pressure at 80°C, and filtration again to obtain a colorless transparent product. Its weight was calculated to have a yield of 94%.

[0092] The colorless transparent product was characterized by gas chromatography, which proved to be a pentaerythritol acrylic acid ester mixture (containing pentaerythritol monoacrylic acid ester, pentaerythritol diacrylic acid ester, pentaerythritol triacrylic acid ester (PET3A) and pentaerythritol tetraacrylic acid ester), wherein the content of pentaerythritol triacrylic acid ester (PET3A) as the target product was 59.8% by weight.

[0093] As can be seen from the above examples, the method of the present application achieves excellent catalytic activity, obtains the target esterification product PET3A with high purity at a very high yield, reduces the generation of by-products, reduces the generation of waste water and waste materials, has excellent environmental protection performance, and the catalyst can be conveniently recovered and recycled, and the catalyst remains excellent catalytic performance after multiple cycles.

Claims

1. A method for esterification, comprising reacting two or more hydroxyl groups in a polyol molecule with an organic acid in the presence of a catalyst to obtain an esterified product, characterized in that, The catalyst comprises an ionic liquid and a support; The polyol contains at least three hydroxyl groups and 3-16 carbon atoms; The organic acid is a C3-C18 saturated carboxylic acid or an unsaturated carboxylic acid.

2. The esterification reaction method according to claim 1, characterized in that, The ionic liquid contains cations and anions. The cation is selected from at least one of the following: imidazolium ion, pyrrolomium ion, pyridinium ion, phosphonium ion, quaternary ammonium ion; The anion is selected from at least one of the following: halide ions, aluminate, chloroaluminate, tetrafluoroborate, hexafluorophosphate, sulfate, hydrogen sulfate, sulfonate, hydrogen phosphate, dihydrogen phosphate, carboxylate, fluorocarboxylate, chlorocarboxylate, chlorometallic acid, and composite anions formed by two or more of the above.

3. The esterification reaction method according to claim 2, characterized in that, The ionic liquid is selected from at least one of the following: 1-butyl-3-methylimidazolium chloride aluminate, 1-(3-sulfopropyl)-3-methylimidazolium hydrogen sulfate, 1-(3-sulfopropyl)-triethylammonium hydrogen sulfate, 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium hydrogen phosphate, 1-butyl-3-methylimidazolium trifluoroacetate, and 1-(3-sulfopropyl)-3-methylimidazolium chloride zincate.

4. The esterification reaction method according to claim 1, characterized in that, The support in the catalyst has a porous structure and is selected from one or more of the following: silica, alumina, aluminosilicate, zeolite, and molecular sieve.

5. The esterification reaction method according to claim 1, characterized in that, Based on the total weight of the catalyst, the ionic liquid content in the catalyst is from 10% to 90% by weight.

6. The esterification reaction method according to claim 1, characterized in that, The catalyst is prepared by the following steps: mixing a raw material for forming a support with an ionic liquid, and then, in the presence of the ionic liquid, causing the raw material for forming the support to react to form a support with a porous structure, wherein the ionic liquid is at least partially bound to or adsorbed in and / or on the porous structure of the support.

7. The esterification reaction method according to claim 6, characterized in that, The raw materials used to form the carrier include silicon and / or aluminum sources, which undergo hydrolysis, condensation and / or self-assembly reactions to form a carrier with a porous structure.

8. The esterification reaction method according to claim 1, characterized in that, The polyol is selected from at least one of the following: pentaerythritol, glycerol, trimethylolethane, trimethylolpropane, xylitol, sorbitol; The organic acid is selected from at least one of the following: acrylic acid, methacrylic acid, oleic acid, and undecenoic acid.

9. The esterification reaction method according to claim 1, characterized in that, The esterification reaction also uses one or more of the following: polymerization inhibitors, antioxidants, and solvents; The polymerization inhibitor is selected from at least one of the following: phenothiazine, hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-p-cresol, 2-tert-butyl-p-cresol, p-benzoquinone, methylhydroquinone, and tetrachlorobenzoquinone. The antioxidant is selected from at least one of the following: hypophosphite, sodium hypophosphite; The solvent is selected from at least one of the following: cyclohexane, toluene, benzene, n-heptane, and n-hexane.

10. The esterification reaction method according to claim 9, characterized in that, The molar ratio of the polyol to the organic acid added to the esterification reaction is 1:3 to 1:

20. Based on the total weight of all materials added to the esterification reaction (excluding solvents), the amount of catalyst added is 4.0-8.0% by weight, the amount of polymerization inhibitor added is 0.4-0.8% by weight, and the amount of antioxidant added is 0.5-1.0% by weight. The amount of solvent added is 100-150 parts by weight, based on a total weight of 100 parts by weight of all materials added to the esterification reaction (excluding solvent).

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