Acrylic acid hydrated tungsten oxide-based solid superacid catalyst and its preparation and application

Abstract

The present invention relates to a tungsten oxide-based solid superacid catalyst for preparing β-hydroxypropionic acid by hydrating acrylic acid. The catalyst preparation method includes: (1) immobilizing an active component and (2) low-temperature phosphating. The present invention partially phosphates the immobilized tungsten oxide. The obtained tungsten phosphide has metallic properties and can adsorb intermediates of acrylic acid polymerization reactions, protecting 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. The catalyst preparation conditions are mild and the process is stable and controllable.

Description

Technical Field

[0001] The present 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 bio-based platform compounds designated for limited development by the U.S. Department of Energy. β-Hydroxypropionic acid can be synthesized into a range of important chemical products through oxidation, reduction, and amination. β-Hydroxypropionic acid is a key monomer in the synthesis of the biodegradable material poly (3-hydroxypropionic acid) (P3HP). P3HP exhibits excellent properties such as hardness, tensile strength, ductility, and biocompatibility, and has potential applications.

[0003] The synthesis of β-hydroxypropionic acid can be divided into two methods: biological and chemical. Currently, the biological method is the most widely reported. However, biological methods are characterized by long fermentation processes, low yields, complex separation and purification processes, and small-scale production. Chemical methods include hydrolysis of β-propiolactone (JACS, 1950, 72, 3267), acidification of β-hydroxypropionitrile, oxidation of 3-hydroxypropanal (DE4107987, DE19629371), carbonylation of vinyl acetate (US2006 / 0128985), oxidation of allyl alcohol (US9873653B2, ChemSusChem, 2009, 2, 57), oxidation of tetrahydrofuran (CN111423321A), and acrylic acid hydration (CN102746141A, CN110981718B, CN113461512A). Acrylic acid hydration offers relatively mild reaction conditions and easy-to-control operating conditions. During the acrylic acid hydration reaction, the primary side reaction is the self-polymerization of acrylic acid under high-temperature, strongly acidic conditions. Currently reported acrylic acid hydration catalysts generally suffer from low efficiency and violent self-polymerization, leading to a lack of efficient catalytic systems.

[0004] This invention develops a new method for preparing a catalyst for the hydration of acrylic acid to produce β-hydroxypropionic acid. The partially phosphated immobilized tungsten oxide produces a tungsten phosphide with metallic properties that can adsorb intermediates in the acrylic acid polymerization reaction and protect the tungsten oxide-based solid superacid used to catalyze the hydration reaction, thereby inhibiting acrylic acid polymerization, improving β-hydroxypropionic acid selectivity, and extending the catalyst's service life. 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 acrylic acid polymerization, 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) Active component immobilization: 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 phosphorus source are placed in porcelain boats, which are then sequentially loaded into a quartz tube of a tube furnace in the direction of gas flow. Heat-treated with inert gas for a specified 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 in the present invention. The tungsten phosphide obtained through partial phosphating has metallic properties and can adsorb intermediates in the acrylic acid polymerization reaction, protecting the tungsten oxide-based solid superacid used to catalyze the hydration reaction, thereby inhibiting acrylic acid polymerization, 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 reaction 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] The invention discloses an application of a solid superacid catalyst for 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 with a mass concentration of 25-50%; the polymerization inhibitor is p-methoxyphenol, and the mass ratio of the polymerization inhibitor to the acrylic acid is 0.05-0.2%; the reaction temperature is 120-180°C; the reaction pressure is 0.5-1.5 MPa; the mass space velocity is 0.75-2h based on the mass of the raw material. -1 .

[0014] The present invention partially phosphates the immobilized tungsten oxide. The resulting tungsten phosphide has metallic properties and can adsorb intermediates in acrylic acid polymerization reactions, protecting the tungsten oxide-based solid superacid used to catalyze the hydration reaction. This inhibits acrylic acid polymerization, improves the selectivity of β-hydroxypropionic acid, and extends the service life of the catalyst. The catalyst is prepared under mild conditions 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. The prepared catalyst has both a strong acid center and a metal center, which helps to adsorb 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 illustrate 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 support 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 precursor was WO3 with a content of 20 wt%;

[0021] (2) Partial phosphation: The catalyst precursor and sodium hypophosphite prepared in step (1) were placed in a porcelain boat, with the amount of sodium hypophosphite being 0.57 g. They were sequentially loaded into the quartz tube of a tubular furnace in the direction of inert gas flow, and heat-treated at 300°C for 4 h in a N2 atmosphere (flow rate 20 mL / min) and then cooled to room temperature to obtain a partially phosphated tungsten oxide-based solid superacid catalyst, designated as catalyst 1. XRD showed that the crystalline phase was a WP-WO3 mixed phase. (3) Catalyst evaluation: The catalyst was evaluated in a fixed-bed tubular reactor. The raw material was an aqueous solution with a mass concentration of 50%, the mass concentration of the inhibitor hydroquinone was 0.1%, the reaction temperature was 180°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 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. 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 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. 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 Example 1.

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

[0029] Example 4 was compared with Example 1. The process and conditions were the same as in Example 1, except that in step (2), potassium hypophosphite was used as the phosphorus source in an amount of 2.81 g. The remaining conditions were identical to those in Example 1. The resulting catalyst was designated Catalyst 5. The catalyst evaluation conditions were the same as in Example 1.

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

[0031] Example 5 was compared with Example 1. The process and conditions were the same as in Example 1, except that in step (2), ammonium hypophosphite was used as the phosphorus source in an amount of 0.22 g. The remaining conditions were identical to those in Example 1. The resulting catalyst was designated Catalyst 6. The catalyst evaluation conditions were the same as in Example 1.

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

[0033] Example 6 differs from Example 1 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. The remaining conditions are identical to those of Example 1. The resulting catalyst is designated as Catalyst 7. The catalyst evaluation conditions are the same as those of Example 1.

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

[0035] Example 7 differs from Example 1 in 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 remaining steps are identical to those in Example 1. The resulting catalyst is designated 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] Example 8 differs from Example 1 in 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. The remaining steps are identical to those in Example 1. The resulting catalyst is designated 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] Example 9 differs from Example 1 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. The remaining conditions are identical to those of Example 1. The resulting catalyst is designated as Catalyst 10. The catalyst evaluation conditions are the same as those of Example 1.

[0040] Example 10: Different types of carriers

[0041] Example 10 differs from Example 1 in that the carrier in step (1) is zirconium oxide and is dried at 80°C for 12 hours. The rest is identical to Example 1; the resulting catalyst is designated as Catalyst 11. The catalyst evaluation conditions are the same as those in Example 1.

[0042] Example 11: Different types of carriers

[0043] Example 11 differs from Example 1 in that, in step (1), the carrier is alumina, the catalyst is dried at 120°C for 6 h, and calcined at 500°C for 4 h. The remaining steps are identical to those of Example 1. The resulting catalyst is designated as Catalyst 12. The catalyst evaluation conditions are the same as those of Example 1.

[0044] Example 12: Different types of carriers

[0045] Example 12 differs from Example 1 in that in step (1), the support is titanium oxide, the catalyst is dried at 100°C for 6 h, and calcined at 700°C for 8 h. The remaining steps are identical to those of Example 1. The resulting catalyst is designated as Catalyst 13. The catalyst evaluation conditions are the same as those of Example 1.

[0046] Example 13: Different types of carriers

[0047] Example 13 differs from Example 1 in that the support in step (1) is cerium oxide and calcined at 800°C for 2 hours. The rest of the process is identical to Example 1; the resulting catalyst is designated 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 Example 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 optimal when zirconium hydroxide is used as the support.

Claims

1. Use of a partially phosphated tungsten oxide-based solid superacid catalyst in catalyzing the hydration of acrylic acid to produce β-hydroxypropionic acid, characterized in that: The catalyst is used to catalyze the hydration of acrylic acid to prepare β-hydroxypropionic acid. 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. After standing 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 use 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; the content of tungsten oxide in the catalyst precursor is 5-50 wt%; the concentration of ammonium metatungstate is 0.05-1 mol / L, and the catalyst is allowed to stand at room temperature for 4-12 hours; the catalyst is dried at 80-120°C for 6-12 hours and calcined at 500-800°C for 2-8 hours to obtain a tungsten oxide-based solid superacid catalyst precursor.

3. The use according to claim 2, characterized in that: In step (1), the carrier is zirconium hydroxide; the content of tungsten oxide in the catalyst precursor is 10-40 wt%; the concentration of ammonium metatungstate is 0.08-0.4 mol / L, and the catalyst is allowed to stand at room temperature for 4-12 hours; the catalyst is dried at 80-120°C for 6-12 hours and calcined at 650-750°C for 4 hours to obtain a tungsten oxide-based solid superacid catalyst precursor.

4. The use 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; the amount of the reducing agent is according to the P / W molar ratio of 0.1:1-10:1; the inert gas is one or more of argon and helium; the gas flow rate is 5-50 mL / min; the heat treatment temperature is 200-600 ° C; the heat treatment time is 1-8 h; after cooling to room temperature in the inert gas, a partially phosphated tungsten oxide-based solid superacid catalyst is obtained.

5. The use according to claim 4, characterized in that: In step (2), the phosphorus source is sodium hypophosphite; the inert gas is replaced by nitrogen; 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.

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

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