Hydroxypropyl acrylate supported catalyst, its preparation method and application

Abstract

The application discloses a hydroxypropyl acrylate supported catalyst and a preparation method and application thereof. The catalyst is prepared by loading active metal ions and a polymerization inhibitor group on an amino-functionalized modified molecular sieve NH2-MCM-41, and is used in a hydroxypropyl acrylate reaction system, so that the synergistic catalysis of the metal ions and the tertiary amine group is realized, and no polymerization inhibitor needs to be added. The catalyst has the advantages of good catalytic activity, strong stability, easy separation and recyclability, overcomes the problems of difficult separation of a traditional homogeneous catalyst and easy coloring of a product, and is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis and relates to a supported catalyst, its preparation method, and its application in the preparation of hydroxypropyl acrylate. Background Technology

[0002] Hydroxypropyl acrylate, or HPA for short, is a colorless and transparent liquid with both carbon-carbon double bonds and hydroxyl groups. It has a wide range of applications and can be used as an active diluent and adhesive in fiber processing, coatings, UV-curable resins, rubber and other fields.

[0003] Currently, the main synthesis process for HPA is the batch ring-opening reaction method, which involves the reaction of acrylic acid and propylene oxide in the presence of a catalyst and a polymerization inhibitor. Polymerization inhibitors include hydroquinone, p-hydroxyanisole, phenothiazine, and copper dibutyldithiocarbamate, while commonly used catalysts include pyridine, chromium trichloride, chromium acetate, chromium acetylacetone, ferric chloride, or organoferric compounds.

[0004] Patent CN102584581A discloses a method for preparing hydroxypropyl acrylate, which involves reacting under vacuum and nitrogen protection in the presence of a preferred chromium acetate catalyst and hydroquinone or p-hydroxyanisole as a polymerization inhibitor.

[0005] Patent US6465681B2 uses chromium acetate as a catalyst and p-hydroxyanisole as a polymerization inhibitor. The reaction temperature is 55-70℃ and the reaction time is 6.5h. The yield of HPA prepared by the reaction is 94.3%. Among them, the chromium catalyst exhibits good catalytic activity and selectivity, but the catalyst is difficult to recover and process.

[0006] Patent CN103524343A discloses a supported KF-Fe2O3 / ZrO2 solid base catalyst, using p-hydroxyanisole as a polymerization inhibitor, to prepare HPA by reacting acrylic acid and propylene oxide at a reaction temperature of 70-110℃, with a propylene oxide conversion rate of 97.7%. The catalyst in this patent is recyclable, but the reaction process requires the addition of an additional polymerization inhibitor.

[0007] Patent CN103288641A discloses a method for synthesizing hydroxypropyl methacrylate (HPMA) using magnetic zeolite molecular sieves as catalysts. Methacrylic acid and propylene oxide react at a reaction temperature of 80-85°C to prepare HPMA, achieving a yield of over 96%. The catalyst in this invention is recyclable, requiring no additional polymerization inhibitors; after 8 cycles, the HPMA yield remains at 93%. In contrast, when iron salts are used as polymerization inhibitors, their mechanism of action is generally considered to be a single-electron transfer reaction. As the metal valence state decreases, the catalytic activity of the molecular sieve gradually declines, leading to a decrease in HPMA yield after multiple cycles.

[0008] In the existing technology for preparing hydroxypropyl acrylate from acrylic acid and propylene oxide, the reaction must be carried out under the conditions of catalyst and polymerization inhibitor. Moreover, the catalyst is generally difficult to recover or its activity decreases significantly after recycling. The polymerization inhibitor is generally a phenolic structure such as hydroquinone or p-hydroxyanisole, which is an aerobic polymerization inhibitor and has poor polymerization inhibition effect under high temperature and nitrogen atmosphere. Summary of the Invention

[0009] To address the above technical problems, this invention proposes a hydroxypropyl acrylate supported catalyst, its preparation method, and its application.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] In a first aspect, the present invention provides a method for preparing a supported catalyst of hydroxypropyl acrylate, comprising the following steps:

[0012] (1) Preparation of amino-functionalized modified molecular sieve NH2-MCM-41: The amino-containing silane coupling agent and MCM-41 molecular sieve were refluxed in an organic solvent, and then filtered, washed and vacuum dried to obtain amino-functionalized NH2-MCM-41 molecular sieve.

[0013] (2) The amino-functionalized NH2-MCM-41 molecular sieve obtained in step (1) above is used as a support and reacted with tetramethylpiperidinol nitroxide radical in a solvent under reflux. After filtration, washing and vacuum drying, NH2-MCM-41 molecular sieve with polymer inhibition groups is obtained.

[0014] (3) The above-mentioned NH2-MCM-41 molecular sieve with supported polymerization inhibitors was impregnated and modified in a chromium or iron metal salt solution, and then filtered, washed and vacuum dried to obtain a supported catalyst of hydroxypropyl acrylate.

[0015] Preferably, in step (1), the amino-containing silane coupling agent is selected from 3-aminopropyltriethoxysilane and / or 3-aminopropyltrimethoxysilane;

[0016] Preferably, in step (1), the organic solvent is selected from one or more of methanol, ethanol, n-propanol, and isobutanol;

[0017] Preferably, in step (1), the reflux reaction temperature is 60-110℃ and the time is 10-24h;

[0018] Preferably, the MCM-41 molecular sieve can be synthesized using a conventional hydrothermal crystallization method, or a commercially available product can be purchased. Further, the silicon source for the conventional hydrothermal crystallization method can be selected from at least one of the following: silica sol, tetraethyl orthosilicate, sodium silicate, water glass, silica gel powder, silica fume, and silica powder; the crystallization temperature is 50℃-200℃, and the crystallization time is 0-72 hours; the template agent used can be selected from at least one of the following: ethylamine, propylamine, ethylenediamine, triethylamine, n-butylamine, tetrapropylammonium hydroxide, hexadecyltrimethylammonium bromide, and tetrapropylammonium bromide.

[0019] Preferably, in step (1), the mass ratio of MCM-41 molecular sieve, amino-containing silane coupling agent and organic solvent is 1:0.5-10:50-100.

[0020] In this invention, the amino-functionalized NH2-MCM-41 molecular sieve obtained in step (1) has primary amine groups; preferably, in step (2), the molar ratio of primary amine groups to tetramethylpiperidinol nitroxide radicals in the amino-functionalized NH2-MCM-41 molecular sieve is 1:2-5; wherein, the molar amount of the primary amine groups is calculated by the nitrogen content in the amino-functionalized NH2-MCM-41 molecular sieve.

[0021] Preferably, in step (2), the solvent is selected from one or more of cumene, toluene, and ethylbenzene;

[0022] Preferably, in step (2), the reflux reaction temperature is 110-160℃ and the time is 12-24h;

[0023] In step (2) of this invention, the primary amine group in the amino-functionalized NH2-MCM-41 molecular sieve bonds with the polymerization inhibitor group to form a tertiary amine structure, thus obtaining an NH2-MCM-41 molecular sieve loaded with polymerization inhibitor groups. The polymerization inhibitor structure (i.e., the tertiary amine structure) is shown below:

[0024]

[0025] Preferably, in step (3), the chromium metal salt is one or more of chromium acrylate, chromium acetate, chromium chloride, and chromium acetylacetonate; the iron metal salt is one or more of ferric phosphate, ferric acetate, ferric chloride, and ferric acetylacetonate.

[0026] Preferably, in step (3), the solvent of the metal salt solution is one or more of water, ethanol, n-propanol, and n-butanol, and the concentration of the metal salt solution is preferably 0.02-0.8 wt%; the concentration of the NH2-MCM-41 molecular sieve loaded with polymerization inhibitor groups in the metal salt solution is 80-120 g / L.

[0027] Preferably, in step (3), the immersion temperature is room temperature, preferably 20-25°C, and the time is 8-24 hours.

[0028] The preparation method of the present invention also includes operations such as filtration, washing, and vacuum drying, which are all conventional technical means in the field and are not particularly limited by the present invention; preferably, the vacuum drying temperature is 60-100℃ and the time is 6-12h.

[0029] Secondly, the present invention provides a supported catalyst for hydroxypropyl acrylate prepared by the above method, wherein the chromium or iron metal loading is 0.1-1 wt% based on the total mass of the catalyst.

[0030] Thirdly, the present invention also provides an application of the above-mentioned catalyst in the preparation process of hydroxypropyl acrylate.

[0031] For example, the present invention provides a method for preparing hydroxypropyl acrylate using acrylic acid and propylene oxide as raw materials, comprising the following steps: uniformly loading a catalyst into a fixed bed or tubular reactor, controlling the nitrogen pressure at 0.3-0.6 MPaA, heating to 60-90°C, then pumping acrylic acid and propylene oxide into the reactor in a fixed ratio, adjusting the residence time according to the reaction temperature and catalyst dosage, taking samples from the reactor outlet for analysis, cooling and discharging the material after the acrylic acid conversion reaches 99.9%, and transferring it to the subsequent separation process.

[0032] Preferably, in the above method for preparing hydroxypropyl acrylate, the molar ratio of acrylic acid to propylene oxide is 1:1.025-1.05.

[0033] Preferably, in the above method for preparing hydroxypropyl acrylate, the mass ratio of acrylic acid to catalyst is 100:10-40; and the reaction time is 1-4 hours.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The catalyst support of this invention is modified with amino-functionalized mesoporous molecular sieve. Its large specific surface area in the pores is conducive to the catalytic reaction of active components and avoids the active metal being covered by macromolecular polymers. The tertiary amine structure can synergistically carry out the catalytic reaction with the supported metal, and can achieve high catalytic activity.

[0036] 2. The catalyst supported by this invention is immobilized with highly efficient nitrogen and oxygen radical inhibition groups, with a wide operating temperature range and can also be used in a nitrogen atmosphere. Since the inhibition structure is in the form of immobilization, there is no problem of separating color codes.

[0037] 3. In the synthesis of hydroxypropyl acrylate, the catalyst supported by this invention provides mild reaction conditions, with an acrylic acid conversion rate of ≥99.9% and a hydroxypropyl acrylate yield of ≥96%. Qualified products can be obtained through simple short-path evaporation, and the catalyst is easy to separate, can be used for a long period, reduces production costs, and is suitable for industrial production. Detailed Implementation

[0038] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0039] Unless otherwise specified, the main raw materials and reagents involved in this invention are all purchased from commercially available finished products.

[0040] reagents Specification Manufacturer MCM-41 molecular sieve 3-5nm Xianfeng Nanomaterials Tetramethylpiperidinol nitroxide radical 99％ Nanjing Huikang Biotechnology 3-Aminopropyltriethoxysilane 97％ Aladdin Reagents Anhydrous ethanol ≥99.5％ Aladdin Reagents Chromium acetate 99.9％ Aladdin Reagents Chromium acetylacetonate 99.9％ Aladdin Reagents Ferric chloride 99.9％ Aladdin Reagents propylene oxide 55％ Aladdin Reagents

[0041] Gas chromatography (GC): Composition analysis of epoxidation reaction solution, model Shimadzu GC-2010-plus; Parameters: DB-5 column, column temperature: initial temperature 50℃, ramp to 300℃, hold for 10 min, injection port temperature: 280℃, detector temperature: 300℃, air flow rate: 400 ml / min, hydrogen flow rate: 40 ml / min, make-up gas flow rate: 30 ml / min, pressure: 77.7 kPa.

[0042] Nitrogen, chromium, and iron element analysis: An Agilent-720 inductively coupled plasma atomic emission spectrometer was used; parameters: power 1.2KW, plasma gas flow rate 15.0L / min, nebulizer flow rate 0.8L / min, auxiliary gas flow rate 1.5L / min, instrument stabilization time 15s, sample injection delay 50s, and cleaning time 50s.

[0043]

Example 1

[0044] The supported catalyst was prepared according to the following method:

[0045] (1) 3-aminopropyltriethoxysilane and commercially available MCM-41 molecular sieve were refluxed in anhydrous ethanol at 78°C for 10 h; wherein the mass ratio of MCM-41 molecular sieve, 3-aminopropyltriethoxysilane and anhydrous ethanol was 1:1:50. After filtration, the mixture was washed with anhydrous ethanol and dried under vacuum at 60°C for 6 h to obtain amino-functionalized NH2-MCM-41 molecular sieve.

[0046] (2) 200g of the above-mentioned amino-functionalized NH2-MCM-41 molecular sieve (N 2.66wt%, 0.38mol primary amino groups), 130.9g (0.76mol) of tetramethylpiperidinol nitroxide radicals and 600g of cumene solution were mixed and stirred under reflux at 154℃ for 24h. The resulting solid was washed with anhydrous ethanol and dried under vacuum at 60℃ for 12h to obtain the NH2-MCM-41 molecular sieve catalyst with supported polymerization inhibitor groups.

[0047] (3) 100g of the above-mentioned NH2-MCM-41 molecular sieve catalyst with supported polymerization inhibitory groups was added to 1L of 0.1% chromium acetate aqueous solution. After stirring and impregnation at room temperature for 24h, the catalyst was filtered, washed with anhydrous ethanol, and dried under vacuum at 100℃ for 8h to obtain the supported catalyst.

[0048] The chromium loading of the active component is 0.23 wt% based on the total mass of the catalyst.

[0049] Synthesis of hydroxypropyl acrylate:

[0050] 4.21 g of the above-mentioned supported catalyst was uniformly loaded into a 316 L fixed-bed reactor; the fixed-bed reactor had a diameter of 7 mm and a height of 1 m; the reactor was heated to 90 °C under a nitrogen pressure of 0.6 MPaA via a jacket; then acrylic acid and propylene oxide were reacted at a mass hourly space velocity (H₂S₀) of 9.13 h⁻¹. -1 (Molar ratio PO / AA = 1.025) was pumped into a fixed bed, with a residence time of 1 hour. The outlet sample analysis showed that the acrylic acid conversion rate was 99.95% and the product HPA selectivity was 96.5%.

[0051] Under the above conditions, after continuous operation for approximately 2200 hours, sampling analysis showed an acrylic acid conversion rate of 99.9% and a product HPA selectivity of 92.5%.

[0052]

Example 2

[0053] The supported catalyst was prepared according to the following method:

[0054] (1) Disperse 200g of silica in 1L of deionized water, adjust the pH to 12 with 30% sodium hydroxide solution, stir the formed gel at room temperature for 1h, add 280g of 20% hexadecyltrimethylammonium bromide aqueous solution, stir at 60℃ for 1h, load the mixed gel into a stainless steel autoclave lined with PTFE, carry out hydrothermal synthesis reaction at 180℃, after 12h, take out the solid product, filter, wash, dry in an oven at 100℃ for 6h, and then calcine in a muffle furnace at 550℃ in an air atmosphere for 8h to obtain MCM-41 molecular sieve;

[0055] 3-Aminopropyltrimethoxysilane was reacted with the prepared MCM-41 molecular sieve in n-propanol under reflux at 97°C for 24 h; wherein the mass ratio of MCM-41 molecular sieve, 3-aminopropyltrimethoxysilane and n-propanol was 1:10:100. After filtration, the mixture was washed with anhydrous ethanol and dried under vacuum at 100°C for 12 h to obtain amino-functionalized NH2-MCM-41 molecular sieve.

[0056] (2) 200g of the above-mentioned amino-functionalized NH2-MCM-41 molecular sieve (N 4.2wt%, 0.6mol primary amino groups), 258.3g (1.5mol) of tetramethylpiperidinol nitroxide radicals were mixed with 1000g of ethylbenzene solution and stirred and refluxed at 136℃ for 24h. The obtained solid was washed with anhydrous ethanol and dried under vacuum at 80℃ for 6h to obtain the NH2-MCM-41 molecular sieve catalyst with supported polymerization inhibitor groups.

[0057] (3) 100g of the above-mentioned NH2-MCM-41 molecular sieve catalyst with supported polymerization inhibitory groups was added to 1L of 0.68% acetylacetone chromium ethanol solution, stirred and impregnated at room temperature for 8h, filtered, washed with anhydrous ethanol, and vacuum dried at 60℃ for 10h to obtain the supported catalyst.

[0058] The chromium loading of the active component is 1 wt% based on the total mass of the catalyst.

[0059] Synthesis of hydroxypropyl acrylate:

[0060] 0.52 g of the above-mentioned supported catalyst was uniformly loaded into a 316 L tubular reactor; the tubular reactor had an outer diameter of 6 mm, an inner diameter of 4 mm, and a length of 3000 mm; the reactor was heated to 80 °C in an oil bath under a nitrogen pressure of 0.4 MPa; then acrylic acid and propylene oxide were reacted at a mass hourly space velocity (HHSV) of 18.12 h⁻¹. -1 (Molar ratio PO / AA = 1.03) was pumped into a tubular reactor, with a residence time of 4 hours. The outlet sample analysis showed that the acrylic acid conversion rate was 99.97% and the product HPA selectivity was 96.9%.

[0061] Under the above conditions, after continuous operation for approximately 2800 hours, sampling analysis showed an acrylic acid conversion rate of 99.89% and a product HPA selectivity of 93.2%.

[0062]

Example 3

[0063] The supported catalyst was prepared according to the following method:

[0064] (1) 3-aminopropyltriethoxysilane and commercially available MCM-41 molecular sieve were refluxed in isobutanol at 105°C for 12 h; wherein the mass ratio of MCM-41 molecular sieve, 3-aminopropyltriethoxysilane and isobutanol was 1:4:70. After filtration, the mixture was washed with anhydrous ethanol and dried under vacuum at 80°C for 10 h to obtain amino-functionalized NH2-MCM-41 molecular sieve.

[0065] (2) 200g of the above-mentioned amino-functionalized NH2-MCM-41 molecular sieve (N 3.15wt%, 0.45mol primary amino groups), 172.2g (1.0mol) of tetramethylpiperidinol nitroxide radicals were mixed with 700g of toluene solution and stirred and refluxed at 110℃ for 20h. The obtained solid was washed with anhydrous ethanol and dried under vacuum at 80℃ for 6h to obtain the NH2-MCM-41 molecular sieve catalyst with supported polymerization inhibitor groups.

[0066] (3) 100g of the above-mentioned NH2-MCM-41 molecular sieve catalyst with supported polymerization inhibitors was stirred with 1L of 0.03% ferric chloride aqueous solution at room temperature for 12h, filtered, washed with anhydrous ethanol, and dried under vacuum at 90℃ for 6h to obtain the supported catalyst.

[0067] The iron loading of the active component is 0.1 wt% based on the total mass of the catalyst.

[0068] Synthesis of hydroxypropyl acrylate:

[0069] 1.36 g of the above-mentioned supported catalyst was uniformly loaded into a 316 L tubular reactor; the tubular reactor had an outer diameter of 6 mm, an inner diameter of 4 mm, and a length of 1000 mm; the reactor was heated to 60 °C in an oil bath under a nitrogen pressure of 0.3 MPa; then acrylic acid and propylene oxide were reacted at a mass hourly space velocity (HHSV) of 4.62 h⁻¹. -1 (Molar ratio PO / AA = 1.05) was pumped into a tubular reactor, with a residence time of 2 hours. The outlet sample analysis showed that the acrylic acid conversion rate was 99.98% and the product HPA selectivity was 96.9%.

[0070] Under the above conditions, after continuous operation for approximately 4200 hours, the acrylic acid conversion rate was 99.94% and the product HPA selectivity was 94.0%.

[0071] Comparative Example 1

[0072] Referring to Example 3, the method for synthesizing hydroxypropyl acrylate was modified by using commercially available chromium acetate catalyst (0.2% by mass of acrylic acid) and tetramethylpiperidinol nitroxide radical (0.1% by mass of acrylic acid) as the polymerization inhibitor. Other operations and conditions remained unchanged. The reaction was carried out intermittently for 4 hours. Gas phase analysis showed that the acrylic acid conversion rate was 81.0% and the product HPA selectivity was 87.2%. Since the catalyst was dissolved in the reaction solution, it was subsequently separated from the heavy components by short-path evaporation and could not be recovered by simple engineering methods.

[0073] Comparative Example 2

[0074] The catalyst was prepared according to the method in Example 3, except that step (1) amino functionalization was omitted, and the MCM-41 molecular sieve was directly processed in steps (2) and (3), while other operations and conditions remained unchanged, and the supported catalyst was obtained.

[0075] The iron loading of the active component is 0.1 wt% based on the total mass of the catalyst.

[0076] When the above catalyst was used in the synthesis method of hydroxypropyl acrylate in Example 3, the conversion rate of acrylic acid was 67.0% and the selectivity of product HPA was 76.4% by gas phase analysis. Since the catalyst could not be loaded with a polymerization inhibitor, the acrylic acid polymerization caused the reaction tube to become blocked after about 8 hours of continuous operation.

[0077] Comparative Example 3

[0078] The catalyst was prepared according to the method in Example 3, except that step (3) of loading iron was omitted, and the MCM-41 molecular sieve was directly processed in steps (1) and (2), while other operations and conditions remained unchanged, and the loaded catalyst was obtained.

[0079] The above catalyst was used in the synthesis method of hydroxypropyl acrylate in Example 3. The acrylic acid conversion rate was 89.7% and the HPA selectivity of the product was 92.9% when the outlet sample was analyzed.

[0080] Under the above conditions, after continuous operation for approximately 4200 hours, sampling analysis showed an acrylic acid conversion rate of 88.6% and a product HPA selectivity of 87.4%.

[0081] Comparative Example 4

[0082] The catalyst was prepared according to the method in Example 3, except that step (2) of loading the polymerization inhibitor group was omitted, and the MCM-41 molecular sieve was directly processed in steps (1) and (3), while other operations and conditions remained unchanged, and the loaded catalyst was obtained.

[0083] The above catalyst was used in the synthesis method of hydroxypropyl acrylate in Example 3, except that 0.1 wt% tetramethylpiperidinol nitroxide radicals were dissolved in the acrylic acid. Other operations and conditions remained unchanged. The conversion rate of acrylic acid was 69.7% and the HPA selectivity of the product was 85.8% when the sample was taken from the outlet.

[0084] Under the above conditions, after continuous operation for approximately 4200 hours, the acrylic acid conversion rate was 63.6% and the product HPA selectivity was 82.9%.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a supported catalyst of hydroxypropyl acrylate, characterized by, The method comprises the following steps: (1) Preparation of amino-functionalized modified molecular sieve NH2-MCM-41: refluxing amino-containing silane coupling agent with MCM-41 molecular sieve in organic solvent, then filtering, washing and drying to obtain amino-functionalized NH2-MCM-41 molecular sieve; (2) Refluxing the amino-functionalized NH2-MCM-41 molecular sieve obtained in step (1) with tetramethyl-piperidinol nitroxide in solvent, then filtering, washing and drying to obtain NH2-MCM-41 molecular sieve loaded with polymerization inhibitor group forming a tertiary amine structure; (3) Immersing the NH2-MCM-41 molecular sieve loaded with polymerization inhibitor group forming a tertiary amine structure in a solution of chromium or iron metal salt, then filtering, washing and drying to obtain hydroxypropyl acrylate loaded catalyst.

2. The method of claim 1, wherein, In step (1), the amino-containing silane coupling agent is selected from 3-aminopropyl triethoxysilane and / or 3-aminopropyl trimethoxysilane.

3. The method of claim 1, wherein, In step (1), the organic solvent is one or more of methanol, ethanol, n-propanol and isobutanol.

4. The method of claim 1, wherein, In step (1), the refluxing temperature is 60-110°C, and the refluxing time is 10-24h.

5. The method of claim 1, wherein, In step (1), the drying temperature after refluxing is 60-100°C, and the drying time is 6-12h.

6. The method according to any one of claims 1 to 5, characterized in that, In step (1), the mass ratio of MCM-41 molecular sieve, amino-containing silane coupling agent and organic solvent is 1:0.5-10:50-100.

7. The method of claim 1, wherein, In step (2), the solvent is selected from one or more of isopropylbenzene, toluene and ethylbenzene.

8. The method of claim 1, wherein, In step (2), the refluxing temperature is 110-160°C, and the refluxing time is 12-24h.

9. The method of claim 1, wherein, In step (2), the NH2-MCM-41 molecular sieve contains primary amine groups, and the molar ratio of the primary amine groups to tetramethyl-piperidinol nitroxide is 1:2-5.

10. The method of claim 1, wherein, In step (3), the chromium metal salt is one or more of chromium acrylate, chromium acetate, chromium chloride and chromium acetylacetone; and the iron metal salt is one or more of iron phosphate, iron acetate, iron chloride and iron acetylacetone.

11. The method of claim 10, wherein, In step (3), the loading amount of chromium or iron metal is 0.1-1wt% based on the total mass of the catalyst.

12. The method of claim 1, wherein, In step (3), the immersion temperature is room temperature, and the immersion time is 8-24h.

13. The method of claim 1, wherein, In step (3), the drying temperature is 60-100°C, and the drying time is 6-12h.

14. A method of preparing hydroxypropyl acrylate, characterized by, The method comprises the following steps: uniformly loading the catalyst prepared by the method of any one of claims 1-13 into a fixed bed or tubular reactor, controlling the nitrogen pressure to be 0.3-0.6MpaA, heating to 60-90°C, then pumping acrylic acid and propylene oxide into the reactor according to a fixed ratio, adjusting the residence time according to the reaction temperature and catalyst dosage, and sampling and analyzing the acrylic acid conversion rate at the reactor outlet until the acrylic acid conversion rate reaches 99.9%, and then discharging the reactor after cooling.

15. The method of claim 14, wherein, The molar ratio of acrylic acid to propylene oxide is 1:1.025-1.

05.

16. The method according to any one of claims 14 or 15, characterized in that, The mass ratio of acrylic acid to catalyst is 100:10-40; and the reaction time is 1-4h.

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