Acrylic acid hydrated tungsten oxide-based solid superacid catalyst as well as preparation and application thereof

Abstract

The invention relates to a tungsten oxide-based solid superacid catalyst for preparing beta-hydracrylic acid by hydrating acrylic acid. A preparation method of the catalyst comprises the following steps: (1) immobilizing active components; and (2) phosphorizing at low temperature. According to the invention, the immobilized tungsten oxide is partially phosphatized, and the obtained tungsten phosphide has metallicity and can adsorb an intermediate of an acrylic acid polymerization reaction and protect tungsten oxide-based solid superacid for catalyzing a hydration reaction, so that the polymerization of acrylic acid is inhibited, the selectivity of beta-hydracrylic acid is improved, and the service life of a catalyst is prolonged. The preparation conditions of the catalyst are mild, and the process is stable and controllable.

Description

Technical Field

[0001] The invention relates to a catalytic method for preparing 3-hydroxypropionic acid by hydrating acrylic acid, and in particular to a catalytic hydration method for acrylic acid and water on a partially phosphated tungsten oxide-based solid superacid. Background Art

[0002] β-Hydroxypropionic acid (3-Hydroxypropionic acid) is an important chemical raw material and one of the 12 limited development bio-based platform compounds launched by the U.S. Department of Energy. β-Hydroxypropionic acid can be synthesized into a series of important chemical products through oxidation, reduction, amination, etc. β-Hydroxypropionic acid is an important monomer for the synthesis of biodegradable material poly 3-hydroxypropionic acid (P3HP). P3HP exhibits excellent properties in hardness, tensile strength, ductility and biocompatibility, and has potential application value.

[0003] The synthesis methods of β-hydroxypropionic acid are divided into biological method and chemical method. The biological method is currently reported more. However, the biological method has a long fermentation process, low yield, complex separation and purification process, and small production scale. The chemical method includes β-propiolactone hydrolysis (JACS, 1950, 72, 3267), β-hydroxypropionitrile acidification, 3-hydroxypropanal oxidation (DE4107987, DE19629371), vinyl acetate carbonylation (US2006 / 0128985), propylene alcohol oxidation (US9873653B2, ChemSusChem, 2009, 2, 57), tetrahydrofuran oxidation (CN111423321A) and acrylic acid hydration method (CN102746141A, CN110981718B, CN113461512A). Among them, the reaction conditions of acrylic acid hydration method are relatively mild and the operating conditions are easy to control. During the hydration reaction of acrylic acid, the main side reaction is the self-polymerization of acrylic acid under high temperature and strong acid conditions. Currently reported acrylic acid hydration catalysts generally have problems such as low efficiency and violent self-polymerization of acrylic acid, and lack of efficient catalytic system.

[0004] The present invention develops a new method for preparing a catalyst for preparing β-hydroxypropionic acid by hydrating acrylic acid. The immobilized tungsten oxide is partially phosphated, and the obtained tungsten phosphide has metallic properties, can adsorb the intermediate of the acrylic acid polymerization reaction, and protect the tungsten oxide-based solid superacid used to catalyze the hydration reaction, thereby inhibiting the polymerization of acrylic acid, improving the selectivity of β-hydroxypropionic acid, and extending the service life of the catalyst. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a high-efficiency catalyst for preparing β-hydroxypropionic acid by continuous hydration of acrylic acid, which can improve the hydration reaction efficiency, inhibit the polymerization of acrylic acid, and improve the selectivity of β-hydroxypropionic acid.

[0006] The technical solution is:

[0007] The method for preparing a β-hydroxypropionic acid catalyst by reacting acrylic acid and water comprises the following steps:

[0008] (1) Immobilization of active components: Weigh a certain amount of ammonium metatungstate and dissolve it in deionized water. Add it dropwise to the carrier under constant stirring. After standing at room temperature for a certain period of time, dry and calcine to obtain a tungsten oxide-based solid superacid catalyst precursor.

[0009] (2) Low-temperature phosphating: The catalyst precursor and the phosphorus source are placed in a porcelain boat respectively, and are sequentially loaded into the quartz tube of a tube furnace according to the gas flow direction. After passing an inert gas for a certain period of time, the mixture is cooled to room temperature to obtain a partially phosphated tungsten oxide-based solid superacid catalyst. This step is a key step of the present invention, and its function is that the tungsten phosphide obtained by partial phosphating has metallic properties, can adsorb the intermediate of the acrylic acid polymerization reaction, protect the tungsten oxide-based solid superacid used to catalyze the hydration reaction, thereby inhibiting the polymerization of acrylic acid, improving the selectivity of β-hydroxypropionic acid, and extending the service life of the catalyst.

[0010] Preferably, in step (1), the carrier is zirconium hydroxide; the content of tungsten oxide is 10-40wt%; the concentration of ammonium metatungstate is 0.08-0.4mol / L, and the mixture is allowed to stand at room temperature for 4-12h; dried at 80-120°C for 6-12h, and calcined at 650-750°C for 4h to obtain a tungsten oxide-based solid superacid catalyst precursor.

[0011] Preferably, in step (2), the phosphorus source is sodium hypophosphite; the reducing agent is used in an amount according to a P / W molar ratio of 0.5:1 / 5:1; the inert gas is nitrogen, and the gas flow rate is 10-30 mL / min; the heat treatment temperature is 250-500° C., and the heat treatment time is 2-6 h; and after cooling to room temperature in the inert gas, a partially phosphated tungsten oxide-based solid superacid catalyst is obtained.

[0012] A solid superacid catalyst for preparing 3-hydroxypropionic acid by hydrating acrylic acid is used in the reaction of preparing 3-hydroxypropionic acid by hydrating acrylic acid.

[0013] Preferably, a fixed bed reactor is used, the raw material is an aqueous solution of acrylic acid, the mass concentration is 25-50%; the inhibitor is p-methoxyphenol, the mass ratio of the inhibitor to acrylic acid is 0.05-0.2%; the reaction temperature is 120-180°C; the reaction pressure is 0.5-1.5MPa; based on the mass of the raw material, the mass space velocity is 0.75-2h -1 .

[0014] The present invention partially phosphates the immobilized tungsten oxide, and the obtained tungsten phosphide has metallic properties, can adsorb the intermediate of acrylic acid polymerization reaction, protect the tungsten oxide-based solid superacid used for catalyzing hydration reaction, thereby inhibiting the polymerization of acrylic acid, improving the selectivity of β-hydroxypropionic acid, and extending the service life of the catalyst. The preparation conditions of the catalyst are mild, and the process is stable and controllable.

[0015] Beneficial technical effects

[0016] 1. The present invention prepares an acrylic acid hydration catalyst by immobilizing tungsten oxide and partially phosphating, and the prepared catalyst has both a strong acid center and a metal center, which is conducive to the adsorption of acrylic acid dimerization intermediates, improves the selectivity of β-hydroxypropionic acid, and prolongs the service life of the catalyst.

[0017] 2. The catalyst preparation process is simple, controllable and easy to operate, and has broad application prospects. DETAILED DESCRIPTION

[0018] In order to further explain the present invention in detail, several specific implementation cases are given below, but the present invention is not limited to these embodiments.

[0019] Example 1

[0020] (1) Active component immobilization: 1.33 g of ammonium metatungstate was weighed and dissolved in 5 mL of deionized water. The mixture was added dropwise to 5.0 g of zirconium hydroxide carrier under constant stirring. The mixture was allowed to stand at room temperature for 12 h, dried at 120 °C for 10 h, and calcined at 700 °C for 4 h. The tungsten oxide-based solid superacid catalyst precursor was obtained. XRD results showed that the product was WO3 with a content of 20 wt%;

[0021] (2) Partial phosphation: The catalyst precursor and sodium hypophosphite prepared in step (1) are placed in a porcelain boat respectively, with the amount of sodium hypophosphite being 0.57 g, and are sequentially loaded into the quartz tube of a tubular furnace in the direction of inert gas flow. In a N2 atmosphere (flow rate 20 mL / min), heat treatment is performed at 300°C for 4 h until the temperature drops to room temperature, thereby obtaining a partially phosphated tungsten oxide-based solid superacid catalyst, which is designated as catalyst 1. XRD shows that the crystalline phase is a WP-WO3 mixed phase. (3) Catalyst evaluation: The catalyst is evaluated in a fixed bed tubular reactor. The raw material is an aqueous solution with a mass concentration of 50%, the mass concentration of the inhibitor hydroquinone is 0.1%, the reaction temperature is 180°C, the reaction pressure is 1.0 MPa, and the mass space velocity is 1.0 h -1 The composition and content of the product were analyzed by high performance liquid chromatography, and the conversion rate of acrylic acid and the selectivity of 3-hydroxypropionic acid were calculated.

[0022] Example 2: Different W contents

[0023] Compared with Example 1, Example 2 has the same process and conditions as Example 1, except that the amount of ammonium metatungstate used in step (1) is 0.59 g, and the amount of sodium hypophosphite used in step (2) is 0.25 g, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 2. The catalyst evaluation conditions are the same as those in Example 1.

[0024] Comparative Example 1

[0025] Comparative Example 1 is compared with Example 2. The process and conditions are the same as Example 1, except that step (2) is omitted. The rest is exactly the same as Example 1. The catalyst obtained is recorded as Catalyst 3. The catalyst evaluation conditions are the same as Example 1.

[0026] Example 3: Different W contents

[0027] Compared with Example 1, Example 3 has the same process and conditions as Example 1, except that the amount of ammonium metatungstate used in step (1) is 3.54 g, and the amount of sodium hypophosphite used in step (2) is 1.52 g, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 4. The catalyst evaluation conditions are the same as those in Example 1.

[0028] Example 4: Different types and amounts of phosphorus sources

[0029] Compared with Example 1, Example 4 has the same process and conditions as Example 1, except that in step (2), potassium hypophosphite is used as the phosphorus source in an amount of 2.81 g, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 5. The catalyst evaluation conditions are the same as those in Example 1.

[0030] Example 5: Different types and amounts of phosphorus sources

[0031] Compared with Example 1, Example 5 has the same process and conditions as Example 1, except that in step (2), ammonium hypophosphite is used as the phosphorus source in an amount of 0.22 g, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 6. The catalyst evaluation conditions are the same as those in Example 1.

[0032] Example 6: Different carrier gas types, flow rates, heat treatment temperatures, and times

[0033] Compared with Example 1, Example 6 differs in that, in step (2), the carrier gas nitrogen flow rate is 10 mL / min, the heat treatment temperature is 250° C., and the heat treatment time is 6 h, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 7. The catalyst evaluation conditions are the same as those in Example 1.

[0034] Example 7: Different carrier gas types, flow rates, heat treatment temperatures, and times

[0035] The difference between Example 7 and Example 1 is that in step (2), the carrier gas argon flow rate is 30 mL / min, the heat treatment temperature is 500° C., and the heat treatment time is 4 h. The rest is exactly the same as Example 1. The obtained catalyst is recorded as Catalyst 8. The catalyst evaluation conditions are the same as those in Example 1.

[0036] Example 8: Different carrier gas types, flow rates, heat treatment temperatures, and times

[0037] The difference between Example 8 and Example 1 is that in step (2), the carrier gas helium flow rate is 10 mL / min, the heat treatment temperature is 500° C., and the heat treatment time is 2 h, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 9. The catalyst evaluation conditions are the same as those in Example 1.

[0038] Example 9: Different carrier gas types, flow rates, heat treatment temperatures, and times

[0039] Compared with Example 1, Example 9 differs in that, in step (2), the carrier gas nitrogen flow rate is 30 mL / min, the heat treatment temperature is 250° C., and the heat treatment time is 4 h, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 10. The catalyst evaluation conditions are the same as those in Example 1.

[0040] Example 10: Different carrier types

[0041] Compared with Example 1, Example 10 is different in that in step (1), the carrier is zirconium oxide and is dried at 80° C. for 12 h. The rest is exactly the same as Example 1. The obtained catalyst is recorded as Catalyst 11. The catalyst evaluation conditions are the same as those in Example 1.

[0042] Example 11: Different types of carriers

[0043] Compared with Example 1, Example 11 is different in that the carrier in step (1) is alumina, dried at 120°C for 6h, and calcined at 500°C for 4h, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 12. The catalyst evaluation conditions are the same as those in Example 1.

[0044] Example 12: Different carrier types

[0045] Compared with Example 1, Example 12 is different in that the carrier in step (1) is titanium oxide, dried at 100°C for 6 hours, and calcined at 700°C for 8 hours, and the rest is exactly the same as Example 1; the obtained catalyst is recorded as Catalyst 13. The catalyst evaluation conditions are the same as those in Example 1.

[0046] Example 13: Different carrier types

[0047] Compared with Example 1, Example 13 is different in that the carrier in step (1) is cerium oxide and calcined at 800° C. for 2 h. The rest is exactly the same as Example 1. The obtained catalyst is recorded as Catalyst 14. The catalyst evaluation conditions are the same as those in Example 1.

[0048] The following table lists the reaction evaluation results of the catalyst prepared by the method of the present invention:

[0049] Example Acrylic acid conversion rate / % 3-Hydroxypropionic acid selectivity / % Dimer selectivity / % Example 1 81.1 85.2 6.8 Example 2 71.6 77.8 14.8 Comparative Example 1 62.5 69.6 25.1 Example 3 80.1 84.8 7.0 Example 4 80.3 84.6 7.1 Example 5 76.1 80.9 10.2 Example 6 78.8 82.3 9.5 Example 7 79.1 83.3 8.9 Example 8 76.9 81.9 10.6 Example 9 74.5 82.8 9.5 Example 10 77.8 83.3 8.8 Embodiment 11 75.6 80.1 12.5 Example 12 77.6 81.8 10.9 Example 13 80.0 83.1 8.8

[0050] From Example 2 and Comparative Example 1, it can be seen that partial phosphating is beneficial to improving the conversion rate of acrylic acid and the selectivity of 3-hydroxypropionic acid, and inhibiting the formation of acrylic acid dimerization; from Examples 1-9, it can be seen that the catalyst prepared under Condition 1 has the best performance; from Examples 1 and 11-13, it can be seen that for tungsten oxide catalysts supported by zirconium oxide, aluminum oxide, titanium oxide and cerium oxide, partial phosphating treatment helps to improve the reaction activity and inhibit acrylic acid polymerization, and the performance is best when zirconium hydroxide is used as the carrier.

Claims

1. A method for preparing a partially phosphated tungsten oxide-based solid superacid catalyst, The preparation of the catalyst comprises the following steps: (1) Immobilization of active components: Weigh ammonium metatungstate and dissolve it in water, add it dropwise to the carrier under stirring, let it stand at room temperature for a certain period of time, dry and calcine to obtain a tungsten oxide-based solid superacid catalyst precursor; (2) Low-temperature phosphating: The catalyst precursor and phosphorus source are placed in porcelain boats respectively, and then loaded into the quartz tube of a tubular furnace in the direction of gas flow. After heat treatment with inert gas, the temperature is cooled to room temperature to obtain a partially phosphated tungsten oxide-based solid superacid catalyst.

2. The preparation method according to claim 1, characterized in that: In step (1), the carrier is one or more of zirconium hydroxide, zirconium oxide, aluminum oxide, titanium oxide and cerium oxide, preferably zirconium hydroxide; the content of tungsten oxide in the catalyst precursor is 5-50wt%, preferably 10-40wt%; the concentration of ammonium metatungstate is 0.05-1mol / L, preferably 0.08-0.4mol / L, and the catalyst is allowed to stand at room temperature for 4-12h; the catalyst is dried at 80-120°C for 6-12h, and then calcined at 500-800°C, preferably 650-750°C, for 2-8h (preferably 4h) to obtain a tungsten oxide-based solid superacid catalyst precursor.

3. The preparation method according to claim 1, characterized in that: In step (2), the phosphorus source is one or more of sodium hypophosphite, potassium hypophosphite and ammonium hypophosphite, preferably sodium hypophosphite; the amount of reducing agent is according to the P / W molar ratio of 0.1:1-10:1, preferably 0.5:1 / 5:1; the inert gas is one or more of nitrogen, argon and helium, preferably nitrogen; the gas flow rate is 5-50mL / min, preferably 10-30mL / min; the heat treatment temperature is 200-600°C, preferably 250-500°C; the heat treatment time is 1-8h, preferably 2-6h; after cooling to room temperature in the inert gas, a partially phosphated tungsten oxide-based solid superacid catalyst is obtained.

4. A catalyst prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the catalyst according to claim 4 in catalyzing the hydration of acrylic acid to prepare β-hydroxypropionic acid.

6. The use according to claim 5, characterized in that: A fixed bed reactor is used, the raw material is an aqueous solution of acrylic acid, the mass concentration is 15-75%, preferably 25-50%; the inhibitor is one or more of hydroquinone, p-methoxyphenol and phenothiazine, the mass ratio of the inhibitor to acrylic acid is 0.01-1%, preferably 0.05-0.2%; the reaction temperature is 100-200°C, preferably 120-180°C; the reaction pressure is 0.1-2MPa, preferably 0.5-1.5MPa; based on the mass of the raw material, the mass space velocity is 0.5-5h -1 , preferably 0.75-2h -1 .