Solid acid catalyst and application thereof in esterification reaction of polyethoxy dihydric alcohol and acrylic acid

Abstract

The invention provides a solid acid catalyst and application thereof in esterification reaction of polyethoxy dihydric alcohol and acrylic acid, and relates to the technical field of preparation of polyethylene glycol diacrylate. The solid acid catalyst is a UIO-66-SO3H catalyst based on a UIO-66 framework, the catalyst is prepared from ZrCl4, formic acid, terephthalic acid and 2-sulfonic acid terephthalic acid through a reaction, the catalyst can catalyze an esterification reaction of polyethyoxyl dihydric alcohol and acrylic acid under the solvent-free condition, a subsequent desolventizing step is avoided, energy consumption is reduced, and the method is suitable for industrial production. And the prepared polyethoxy glycol diacrylate product is colorless and transparent in color, high in purity, low in polymerization degree, moderate in viscosity and wider in application space.

Description

Technical Field

[0001] This invention relates to the field of polyethylene glycol diacrylate preparation technology, specifically to a solid acid catalyst and its application in the esterification reaction of polyethoxydiol and acrylic acid. Background Technology

[0002] Polyethylene glycol (PEG) and acrylate can be esterified to produce polyethoxylated glycol diacrylate (PEGDA). PEGDA is an important functional polymer material, widely used in biomedicine, materials science, and industry due to its excellent water solubility, crosslinking properties, and biocompatibility. PEGDA can be used to prepare biodegradable materials, coatings, age meters, sensors, and electronic materials. With technological advancements, the application areas of PEGDA continue to expand, demonstrating an increasingly important role in various aspects of life.

[0003] Publication No. CN 1659212 A discloses a process for preparing polyalkoxyl acrylates using methylcyclohexane as a solvent and sulfuric acid as a catalyst. This process does not involve purification, and the mixed product is directly used as a SAP crosslinking agent. However, the product prepared by this invention has low purity and is light yellow in color, thus limiting its application range.

[0004] Publication No. CN 106518664 A discloses an esterification process of PEG400 and acrylic acid using toluene as a solvent, p-toluenesulfonic acid as a catalyst, and p-hydroxyanisole as a polymerization inhibitor. After the reaction, the product is obtained by washing with salt, alkali, and water to remove the solvent. In this patent, toluene is used as the solvent. Since the solvent is difficult to remove completely, toluene residue remains, affecting product quality and human safety. Furthermore, the solvent removal process is energy-intensive.

[0005] Publication No. CN 116376006 A discloses an esterification process of PEG600 and acrylic acid using cyclohexane and n-propyl acetate as solvents, methanesulfonic acid as a catalyst, and p-hydroxyanisole as a polymerization inhibitor. After the reaction, the mixture is purified by alkali neutralization and washing, and then desolventized under a vacuum exceeding -0.097 MPa. This patent requires a high vacuum during desolventization, resulting in significant energy consumption.

[0006] Therefore, it is crucial to design and develop a PEGDA production method that reduces solvent use, minimizes aromatic solvent residue, and ensures product purity and viscosity. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a solid acid catalyst and its application in the esterification reaction of polyethoxydiol and acrylic acid. The esterification reaction does not use solvents, has no solvent removal step, saves energy, and leaves no solvent residue. Moreover, the prepared product is colorless and transparent, has high purity, low degree of polymerization, and moderate viscosity, thus having a wider range of applications.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A solid acid catalyst, wherein the solid acid catalyst is a UIO-66-SO3H catalyst based on the UIO-66 framework, and the preparation method of the UIO-66-SO3H catalyst includes the following steps:

[0010] S1-1. ZrCl4, formic acid, terephthalic acid and 2-sulfonic terephthalic acid are dissolved together in a solvent and reacted at 120-140℃ for 8-12 hours to obtain a mixed reactant for later use.

[0011] S1-2. Add formic acid to the mixed reactants, reflux for 5-10 hours, cool and filter, and collect the precipitate.

[0012] S1-3. The precipitate was washed alternately with solvent and methanol and then dried to obtain UIO-66-SO3H catalyst.

[0013] Preferably, in step S1-1, the molar ratio of ZrCl4, formic acid, terephthalic acid and 2-sulfonic acid terephthalic acid is 1:0.1-0.5:0.5-1.

[0014] Preferably, the solvent in step S1-1 is one or a mixture of DMF, DMAC, dimethyl sulfoxide, water, methanol, ethanol, γ-valerolactone, or ionic liquid.

[0015] Preferably, the reflux temperature in step S1-2 is 50-80℃, and more preferably 60-70℃.

[0016] Preferably, the drying method in steps S1-3 is drying in a supercritical CO2 environment at 60°C.

[0017] The application of the above-mentioned UIO-66-SO3H catalyst in the esterification reaction of polyethoxydiol and acrylic acid, the application method includes the following steps:

[0018] S2-1. Polyethoxydiol, acrylic acid, UIO-66-SO3H catalyst, CuCl, and BHT are mixed and added to a reactor, and the reaction is carried out at a temperature of 90-105℃ to obtain the reaction mixture.

[0019] S2-2. The reactants are neutralized with alkali and washed with salt, and then dried to obtain the polyethoxydiol diacrylate product.

[0020] Preferably, in step S2-1, the mass ratio of polyethoxydiol, acrylic acid, UIO-66-SO3H catalyst, CuCl, and BHT is 150-225:64.8:8:0.03:0.42-0.5.

[0021] Preferably, in step S2-1, the reaction process is controlled in a slightly negative pressure environment, and the pressure range of the slightly negative pressure is -1 kPa to -10 kPa.

[0022] This invention provides a solid acid catalyst and its application in the esterification reaction of polyethoxydiol and acrylic acid. Compared with existing technologies, its advantages are:

[0023] This invention prepares a solid strong acid catalyst, UIO-66-SO3H, based on the UIO-66 framework. This catalyst can prepare polyethoxydiol diacrylate (PEGDA) in a solvent-free manner. Furthermore, the use of this catalyst in the esterification reaction of polyethoxydiol and acrylic acid can accelerate the reaction rate, solving the problems of yellowing and polymerization caused by the long reaction time in solvent-free esterification under conventional catalysts. The solvent-free method eliminates the subsequent solvent removal process, reduces energy consumption, and improves the purity of the final product. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1:

[0026] Preparation of UIO-66-SO3H catalyst:

[0027] (1) Weigh 4.66g ZrCl4, 6.64g terephthalic acid, and 19.9g 2-sulfonic acid terephthalic acid, add 285ml DMF, dissolve evenly, transfer to a reaction vessel, seal and place in an oven, adjust the temperature to 125℃, and end the reaction after 8h.

[0028] (2) After cooling, take out the mixture, add 10 ml of formic acid, place it in a three-necked flask, and reflux it in an oil bath at 50°C for 6 hours.

[0029] (3) After cooling to room temperature, the precipitate was collected by centrifugation, washed three times each with DMF and methanol, and dried at 60℃ with supercritical CO2 for 8h to obtain UIO-66-SO3H catalyst.

[0030] The specific surface area of ​​the above-mentioned UIO-66-SO3H catalyst was tested and found to be 762 cm². 2 / g, with a sulfonic acid loading of 8.8wt%.

[0031] Example 2:

[0032] Preparation of polyethoxylated glycol (400) diacrylate (PEG(400)DA):

[0033] (1) Weigh 150g PEG400, 64.8g acrylic acid, 8g UIO-66-SO3H catalyst, 0.03g CuCl and 0.42g BHT and add them to the reactor. The reaction is carried out at 98℃, and the pressure inside the reactor is kept at -5kPa during the reaction to promote the removal of water.

[0034] (2) Measure the amount of water in the lower layer of the Dean-Stark separator. When the water output reaches more than 95% of the theoretical output, shut off the reaction. Count the reaction time. After the reaction is completed, add the crude product to the separatory funnel, add 10% NaOH solution for washing, let stand and separate to remove the aqueous phase, add saturated brine for washing, let stand and separate to remove the aqueous phase, and vacuum dry the upper organic phase to obtain a colorless oily liquid as PEGDA product with a viscosity of 161 mPa·s / 25℃.

[0035] Example 3:

[0036] Preparation of polyethoxylated glycol (600) diacrylate (PEG(600)DA):

[0037] (1) Weigh 225g PEG600, 64.8g acrylic acid, 8g UIO-66-SO3H catalyst, 0.03g CuCl, and 0.5g BHT and add them to the reactor. The reaction is carried out at 103℃, and the pressure inside the reactor is maintained at -5kPa during the reaction to promote the removal of water.

[0038] (2) Measure the amount of water in the lower layer of the Dean-Stark separator. When the water output reaches more than 95% of the theoretical output, shut off the reaction. Count the reaction time. After the reaction is completed, add the crude product to the separatory funnel, add 10% NaOH solution for washing, let stand and separate to remove the aqueous phase, add saturated brine for washing, let stand and separate to remove the aqueous phase, and vacuum dry the upper organic phase to obtain a colorless oily liquid as PEGDA product with a viscosity of 335 mPa·s / 25℃.

[0039] Comparative Example 1:

[0040] Preparation of polyethoxylated glycol (400) diacrylate (PEG(400)DA):

[0041] (1) Weigh 150g PEG400, 64.8g acrylic acid, 1.3g concentrated sulfuric acid, 0.03g CuCl and 0.42g BHT and add them to the reactor. The reaction is carried out at 105℃, and the pressure inside the reactor is kept at -5kPa during the reaction to promote the removal of water.

[0042] (2) Measure the amount of water in the lower layer of the Dean-Stark separator. When the outflow reaches more than 95% of the theoretical outflow, shut off the reaction. Count the reaction time. After the reaction is completed, add the crude product to the separatory funnel, add 10% NaOH solution for washing, let stand and separate to remove the aqueous phase, add saturated brine for washing, let stand and separate to remove the aqueous phase, and dry the upper organic phase to obtain a light yellow viscous oily liquid, which is the PEGDA product with a viscosity of 196 mPa·s / 25℃.

[0043] Comparative Example 2:

[0044] Preparation of polyethoxylated glycol (400) diacrylate (PEG(400)DA):

[0045] (1) Weigh 150g PEG400, 64.8g acrylic acid, 0.03g CuCl, 12g solid acid catalyst (Sulfatedzirconia catalyst, Alfa Aesar), and 0.42g BHT and add them to a 500ml reaction flask. The reaction is carried out at 95℃, and a slightly negative pressure environment is controlled during the reaction to promote the removal of water.

[0046] (2) Measure the amount of water in the lower layer of the Dean-Stark separator. When the water output reaches more than 95% of the theoretical output, shut off the reaction. Count the reaction time. After the reaction is completed, add the crude product to the separatory funnel, add 10% NaOH solution for washing, let stand and separate to remove the aqueous phase, add saturated brine for washing, let stand and separate to remove the aqueous phase, and dry the upper organic phase to obtain a light yellow viscous oily liquid, which is the PEGDA product with a viscosity of 182 mPas / 25℃.

[0047] Detection:

[0048] The reaction times of Examples 2-3 and Comparative Example 11-2, as well as the viscosity of the final PEGDA product, were measured. The specific results are shown in the table below:

[0049] Group reaction time Viscosity (tested at 25℃) Example 2 5.5h 161 mPa·s Example 3 6h 335 mPa·s Comparative Example 1 10h 196 mPa·s Comparative Example 2 8.5h 182 mPa·s

[0050] As can be seen from the above tests, the use of UIO-66-SO3H catalyst in Examples 1-2 to prepare PEGDA products significantly increased the reaction rate, reduced the sulfonation and polymerization degree of the product, ensured the quality of the product, and the overall reaction was solvent-free, avoiding the introduction of solvents and solving the problem of possible trace solvents remaining in the product, making it more green, environmentally friendly and energy-saving.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solid acid catalyst, characterized in that, The solid acid catalyst is a UIO-66-SO3H catalyst based on the UIO-66 framework, and the preparation method of the UIO-66-SO3H catalyst includes the following steps: S1-1, ZrCl4 or ZrOCl 2· H2O, terephthalic acid, and 2-sulfonic terephthalic acid are dissolved together in a solvent and reacted at 120-140℃ for 8-12 hours to obtain a mixed reactant for later use. S1-2. Add formic acid to the mixed reactants, reflux for 5-10 hours, cool and filter, and collect the precipitate. S1-3. The precipitate was washed alternately with solvent and methanol and then dried to obtain UIO-66-SO3H catalyst.

2. The solid acid catalyst according to claim 1, characterized in that: In step S1-1, ZrCl4 or ZrOCl 2· The molar ratio of H2O, terephthalic acid, and 2-sulfonic acid terephthalic acid is 1:0.1-0.5:0.5-1.

3. The solid acid catalyst according to claim 1, characterized in that: In step S1-1, the solvent is one or a mixture of DMF, DMAC, dimethyl sulfoxide, water, methanol, ethanol, γ-valerolactone, or ionic liquid.

4. A solid acid catalyst according to claim 1, characterized in that: The reflux temperature in step S1-2 is 50℃-80℃.

5. A solid acid catalyst according to claim 1, characterized in that: The drying method in steps S1-3 is drying in a supercritical CO2 environment at 60℃.

6. The application of the solid acid catalyst as described in any one of claims 1-5 in the esterification reaction of polyethoxydiol and acrylic acid, characterized in that, The application method includes the following steps: S2-1. Polyethoxydiol, acrylic acid, UIO-66-SO3H catalyst, CuCl, and BHT are mixed and added to a reactor, and the reaction is carried out at a temperature of 90-105℃ to obtain the reaction mixture. S2-2. The reactants are neutralized with alkali and washed with salt, and then dried to obtain the polyethoxydiol diacrylate product.

7. The application according to claim 6, characterized in that: In step S2-1, the mass ratio of polyethoxydiol, acrylic acid, UIO-66-SO3H catalyst, CuCl, and BHT is 150-225:64.8:8:0.03:0.42-0.

5.

8. The application according to claim 6, characterized in that: In step S2-1, the reaction process is controlled under a slightly negative pressure environment, and the pressure range of the slightly negative pressure is from -3 kPa to -10 kPa.