Preparation and application of acrylic acid hydration catalyst

Abstract

The present invention relates to a solid superacid catalyst for acrylic acid hydration, the preparation method of which comprises the following steps: (1) carrier preparation, (2) active component loading, and (3) partial reduction. The present invention uses valence-adjustable cerium oxide as a carrier. After loading the superacid, the vacant sites generated by partial reduction promote the adsorption of active groups of the reactants, thereby improving the reaction activity. The present invention has the advantages of readily available raw materials, mild reaction conditions, and high product selectivity.

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 of acrylic acid and water on a solid superacid. Background Art

[0002] In recent years, the problem of "white pollution" has become increasingly serious. The long degradation cycles of traditional plastics have triggered a series of environmental issues, which have attracted increasing international attention. Polyhydroxyalkanoates (PHAs) have become a research hotspot in recent years due to their excellent biodegradability. Among them, poly (3-hydroxypropionic acid) (P3HP) exhibits excellent properties such as hardness, tensile strength, ductility, and biocompatibility, showing potential application value. 3-Hydroxypropionic acid, as a key monomer in the synthesis of P3HP, is a widely used chemical raw material.

[0003] Currently, there are numerous reports on the biological synthesis of 3-hydroxypropionic acid. However, these methods are difficult to manufacture on a large scale due to their long fermentation process, low yield, and complex separation and purification procedures. Chemical methods for the synthesis of 3-hydroxypropionic acid include hydrolysis of β-propiolactone, acidification of β-hydroxypropionitrile, oxidation of 3-hydroxypropanal, carbonylation of vinyl acetate, oxidation of allyl alcohol, and hydration of acrylic acid. The hydration of acrylic acid offers relatively mild reaction conditions and easy-to-control operating conditions.

[0004] There are few reports on the preparation of 3-hydroxypropionic acid by acrylic acid hydration. Patent CN102746141A reports a method for preparing 3-hydroxypropionic acid by hydrating acrylic acid catalyzed by inorganic acid, molecular sieve, and resin. The reaction is carried out in a kettle reactor at 60-280°C for 1-24 hours to produce 3-hydroxypropionic acid. Patent CN110981718B reports that acid-modified β-type molecular sieves can reduce the reaction temperature and by-product selectivity of acrylic acid hydration, thereby increasing the yield of 3-hydroxypropionic acid. Patent CN113461512A reports a method for preparing 3-hydroxypropionic acid by hydrating acrylic acid catalyzed by saturated organic acid, and the catalyst is easy to separate and recover. During the acrylic acid hydration reaction, the main side reactions are the self-polymerization of acrylic acid under high temperature and strong acidic conditions and the etherification of 3-hydroxypropionic acid. The currently reported technologies generally have problems such as low efficiency and side reactions, and lack of efficient catalytic systems.

[0005] The present invention develops a new method for preparing a catalyst for the hydration of acrylic acid to 3-hydroxypropionic acid. Using valence-adjustable cerium oxide as a carrier, the catalyst is loaded with sulfuric acid and then partially reduced. The resulting defect sites promote the adsorption of active groups, thereby improving reaction activity. Summary of the Invention

[0006] In view of the above problems existing in the prior art, the present invention provides a high-efficiency catalyst for preparing 3-hydroxypropionic acid by continuous hydration of acrylic acid, which can improve the hydration reaction efficiency, inhibit side reactions, and improve product selectivity.

[0007] The technical solution is:

[0008] The method for preparing a catalyst for producing 3-hydroxypropionic acid by hydrating acrylic acid comprises the following steps:

[0009] (1) Carrier preparation: The raw salt is prepared into an aqueous solution, the pH value of the solution is adjusted and continuously stirred to form a gel, and the carrier is obtained after washing, drying, and calcining;

[0010] (2) Active component loading: The carrier is added to a sulfuric acid aqueous solution, and the catalyst precursor is obtained after impregnation, filtration, drying, and calcination;

[0011] (3) Partial Reduction: The catalyst precursor is partially reduced in a reducing atmosphere to obtain a catalyst for the hydration of acrylic acid to 3-hydroxypropionic acid. This step is a key step in the present invention. Its purpose is to obtain an appropriate amount of oxygen vacancies through partial reduction, which is beneficial for the adsorption of active groups in the reactant molecules, thereby improving the efficiency of the main reaction and suppressing side reactions.

[0012] Preferably, in step (1), the raw salt is Ce(NO3)3·6H2O; the pH regulator is ammonia water, and the pH value is 10-11; stirring for 10-12 hours, washing with deionized water to neutrality; drying at 110-130°C for 6-12 hours, and calcining at 450-550°C for 4-6 hours to obtain a carrier.

[0013] Preferably, in step (2), the active component is sulfate, and the active component content is 10-40wt%; the carrier content is 60-90wt%; the concentration of the sulfuric acid solution used is 0.5-2mol / L; after impregnation at room temperature for 4-6h, the solid product is filtered to obtain a solid product, which is dried at 110-130°C for 6-12h and calcined at 450-550°C for 4-6h to obtain a catalyst precursor.

[0014] Preferably, the reducing atmosphere in step (3) is hydrogen or a mixture of hydrogen and nitrogen (or argon, or helium), the volume proportion of hydrogen in the mixture is 20-60%; the reduction temperature is 300-400°C; and the reduction time is 2-4h.

[0015] The invention discloses an application of a solid superacid catalyst for preparing 3-hydroxypropionic acid by hydrating acrylic acid.

[0016] Preferably, a fixed bed reactor is used, the raw material is an aqueous solution of acrylic acid, the mass concentration of which is 15-75%, preferably 25-50%; the polymerization inhibitor is one or more of hydroquinone, p-methoxyphenol and phenothiazine, 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; and the mass space velocity is 0.75-2h based on the mass of the raw material. -1 .

[0017] The present invention uses valence-adjustable cerium oxide as a carrier. After loading a superacid, the vacant sites generated by partial reduction can promote the adsorption of reactive groups of reactants, thereby improving reaction activity. The present invention has the advantages of readily available raw materials, mild reaction conditions, and high product selectivity.

[0018] Beneficial technical effects

[0019] 1. The present invention prepares an acrylic acid hydration catalyst by carrier preparation, active component loading, and partial reduction. The steps are simple, the conditions are mild, and the process is controllable. The prepared catalyst has both strong acid centers and vacancies, which facilitate the adsorption of active groups and improve reaction activity.

[0020] 2. The catalyst has the advantages of low reaction temperature, high selectivity, and good stability. The reaction process is simple, controllable, and easy to operate, and has broad application prospects. DETAILED DESCRIPTION

[0021] 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.

[0022] Example 1

[0023] (1) Support preparation: 5.0 g of Ce(NO3)3·6H2O was weighed and dissolved in 100 mL of deionized water. 3.4 mol / L of ammonia was added to adjust the pH to 11.0. The mixture was stirred for 8 h to form a gel. The gel was washed with deionized water until neutral, dried at 120°C for 12 h, and calcined at 500°C for 4 h to obtain the support. XRD results showed that the synthesized support was CeO2.

[0024] (2) Active component impregnation: Weigh 2.0 g of the support prepared in step (1), add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a catalyst precursor;

[0025] (3) Partial reduction: The catalyst precursor prepared in step (2) was placed in a quartz tube furnace and reduced at 400°C for 3 h in a H2 atmosphere (flow rate 50 mL / min) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. X-ray photoelectron spectroscopy results showed that Ce was present in the form of Ce.4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 1.

[0026] (4) Catalyst evaluation: The catalyst was evaluated in a fixed-bed tubular reactor. The raw material was a 50% aqueous solution of acrylic acid, the mass concentration of the polymerization 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 ; Product analysis: 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.

[0027] Comparative Example 1

[0028] Comparative Example 1 differs from Example 1 in that the partial reduction process of step (3) is omitted, and the remaining processes and conditions are identical to those of Example 1; the resulting catalyst is designated as Catalyst 2. Catalyst evaluation: The reaction was conducted in a fixed-bed tubular reactor. The raw material was a 50% mass concentration aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor hydroquinone was 0.1%, the reaction temperature was 100°C, the reaction pressure was 0.1 MPa, and the mass space velocity was 5.0 h -1 , the product analysis conditions are exactly the same as those in Example 1.

[0029] Example 2: Carrier Synthesis Precursor Salt Type - Ce(SO4)2·4H2O

[0030] Weigh 5.0 g of Ce(SO4)2·4H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 10.0, stir for 16 h to form a gel, wash with deionized water until neutral, dry at 130 ° C for 6 h, and calcine at 650 ° C for 2 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0031] Weigh 2.0 g of the support, add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, which is then dried at 130 °C for 6 h and calcined at 650 °C for 2 h to obtain a catalyst precursor;

[0032] The catalyst precursor was placed in a quartz tube furnace and reduced at 400 ° C for 3 h in a H2 atmosphere (flow rate 50 mL / min) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. X-ray photoelectron spectroscopy results showed that Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 3.

[0033] The catalyst evaluation conditions and process were the same as those in Example 1.

[0034] Example 3: Carrier Synthesis Precursor Salt Type - CeCl3·7H2O

[0035] Weigh 5.0 g of CeCl3·7H2O and dissolve it in 100 mL of deionized water. Add 3.4 mol / L of ammonia water to adjust the pH to 12.0. Stir for 1 h to form a gel. Wash with deionized water until neutral. Dry at 110°C for 12 h and calcine at 400°C for 8 h to obtain a support (XRD results show that the synthesized support is CeO2).

[0036] Weigh 2.0 g of the support, add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, which is then dried at 110°C for 12 h and calcined at 400°C for 8 h to obtain a catalyst precursor;

[0037] The catalyst precursor was placed in a quartz tube furnace and reduced at 400 ° C for 3 h in a H2 atmosphere (flow rate 50 mL / min) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. X-ray photoelectron spectroscopy results showed that Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 4.

[0038] The catalyst evaluation conditions and process were the same as those in Example 1.

[0039] Example 4: Sulfuric acid concentration increases

[0040] Weigh 5.0 g of Ce(NO3)3·6H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 11.0, stir for 8 h to form a gel, wash with deionized water until neutral, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0041] Weigh 2.0 g of the support, add 2 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, dry it at 120°C for 12 h, and calcine it at 500°C for 4 h to obtain a catalyst precursor;

[0042] The catalyst precursor was placed in a quartz tube furnace and reduced at 400 ° C for 3 h in a H2 atmosphere (flow rate 50 mL / min) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. X-ray photoelectron spectroscopy results showed that Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 5.

[0043] The catalyst evaluation conditions and process were the same as those in Example 1.

[0044] Example 5: Sulfuric acid concentration reduction

[0045] Weigh 5.0 g of Ce(NO3)3·6H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 11.0, stir for 8 h to form a gel, wash with deionized water until neutral, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0046] Weigh 2.0 g of the support, add 0.5 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, which is then dried at 120 °C for 12 h and calcined at 500 °C for 4 h to obtain a catalyst precursor;

[0047] The catalyst precursor was placed in a quartz tube furnace and reduced at 400 ° C for 3 h in a H2 atmosphere (flow rate 50 mL / min) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. X-ray photoelectron spectroscopy results showed that Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 6.

[0048] The catalyst evaluation conditions and process were the same as those in Example 1.

[0049] Example 6: Extended immersion time

[0050] Weigh 5.0 g of Ce(NO3)3·6H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 11.0, stir for 8 h to form a gel, wash with deionized water until neutral, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0051] Weigh 2.0 g of the support, add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 10 h, and then filter to obtain a solid product, dry it at 120°C for 12 h, and calcine it at 500°C for 4 h to obtain a catalyst precursor;

[0052] The catalyst precursor was placed in a quartz tube furnace and reduced at 400 ° C for 3 h in a H2 atmosphere (flow rate 50 mL / min) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. X-ray photoelectron spectroscopy results showed that Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 7.

[0053] The catalyst evaluation conditions and process were the same as those in Example 1.

[0054] Example 7: Shortened immersion time

[0055] Weigh 5.0 g of Ce(NO3)3·6H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 11.0, stir for 8 h to form a gel, wash with deionized water until neutral, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0056] Weigh 2.0 g of the support, add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 1 h, and then filter to obtain a solid product, dry it at 120°C for 12 h, and calcine it at 500°C for 4 h to obtain a catalyst precursor;

[0057] The catalyst precursor was placed in a quartz tube furnace and reduced at 400 ° C for 3 h in a H2 atmosphere (flow rate 50 mL / min) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. X-ray photoelectron spectroscopy results showed that Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 8.

[0058] The catalyst evaluation conditions and process were the same as those in Example 1.

[0059] Example 8: Reduction conditions, reducing atmosphere, reducing temperature, reducing time

[0060] Weigh 5.0 g of Ce(NO3)3·6H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 11.0, stir for 8 h to form a gel, wash with deionized water until neutral, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0061] Weigh 2.0 g of the support, add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, dry it at 120°C for 12 h, and calcine it at 500°C for 4 h to obtain a catalyst precursor;

[0062] The catalyst precursor was placed in a quartz tube furnace and reduced at 350 ° C for 6 h in a H2 / N2 (flow rate 50 mL / min) mixed atmosphere (H2 volume ratio 10%) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. The X-ray photoelectron spectroscopy results showed that the Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 9.

[0063] The catalyst evaluation conditions and process were the same as those in Example 1.

[0064] Example 9: Reduction conditions, reducing atmosphere, reducing temperature, reducing time

[0065] Weigh 5.0 g of Ce(NO3)3·6H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 11.0, stir for 8 h to form a gel, wash with deionized water until neutral, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0066] Weigh 2.0 g of the support, add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, dry it at 120°C for 12 h, and calcine it at 500°C for 4 h to obtain a catalyst precursor;

[0067] The catalyst precursor was placed in a quartz tube furnace and reduced at 300 ° C for 6 h in a H2 / N2 (flow rate 50 mL / min) mixed atmosphere (H2 volume ratio 50%) to obtain a partially reduced cerium oxide-supported sulfuric acid catalyst. The X-ray photoelectron spectroscopy results showed that the Ce element was Ce 4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 10.

[0068] The catalyst evaluation conditions and process were the same as those in Example 1.

[0069] Example 10: Reduction conditions, reducing atmosphere, reducing temperature, reducing time

[0070] Weigh 5.0 g of Ce(NO3)3·6H2O, dissolve it in 100 mL of deionized water, add 3.4 mol / L ammonia water to adjust the pH to 11.0, stir for 8 h to form a gel, wash with deionized water until neutral, dry at 120°C for 12 h, and calcine at 500°C for 4 h to obtain a support (XRD results show that the synthesized support is CeO2);

[0071] Weigh 2.0 g of the support, add 1 mol / L sulfuric acid at a solid-liquid ratio of 1:5, stir for 2 h, and filter to obtain a solid product, dry it at 120°C for 12 h, and calcine it at 500°C for 4 h to obtain a catalyst precursor;

[0072] The catalyst precursor was placed in a quartz tube furnace and reduced at 400 ° C for 2 h in a H2 / N2 (flow rate 50 mL / min) mixed atmosphere (H2 volume ratio is 90%) to obtain a partially reduced cerium oxide supported sulfuric acid catalyst. The X-ray photoelectron spectroscopy results showed that the Ce element was Ce4+ and Ce 3+ Coexisting on the catalyst surface, Ce 3+ The relative content is 26%, recorded as catalyst 11.

[0073] The catalyst evaluation conditions and process were the same as those in Example 1.

[0074] Example 11: Reaction conditions, raw materials, temperature, pressure, space velocity

[0075] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 15 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization 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 ; Product analysis is the same as in Example 1.

[0076] Example 12: Reaction conditions, raw materials, temperature, pressure, space velocity

[0077] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 75 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization 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 ; Product analysis is the same as in Example 1.

[0078] Example 13: Reaction conditions, raw materials, temperature, pressure, space velocity

[0079] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor phenothiazine was 0.01%, the reaction temperature was 180°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 1.0 h -1 ; Product analysis is the same as in Example 1.

[0080] Example 14: Reaction conditions, raw materials, temperature, pressure, space velocity

[0081] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the concentration of the polymerization inhibitor p-methoxyphenol was 1%, the reaction temperature was 180°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 1.0 h -1 ; Product analysis is the same as in Example 1.

[0082] Example 15: Reaction conditions, raw materials, temperature, pressure, space velocity

[0083] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor hydroquinone was 0.1%, the reaction temperature was 100°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 1.0 h-1 ; Product analysis is the same as in Example 1.

[0084] Example 16: Reaction conditions, raw materials, temperature, pressure, space velocity

[0085] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor hydroquinone was 0.1%, the reaction temperature was 200°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 1.0 h -1 ; Product analysis is the same as in Example 1.

[0086] Example 17: Reaction conditions, raw materials, temperature, pressure, space velocity

[0087] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor hydroquinone was 0.1%, the reaction temperature was 180°C, the reaction pressure was 0.1 MPa, and the mass space velocity was 1.0 h -1 ; Product analysis is the same as in Example 1.

[0088] Example 18: Reaction conditions, raw materials, temperature, pressure, space velocity

[0089] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor hydroquinone was 0.1%, the reaction temperature was 180°C, the reaction pressure was 2.0 MPa, and the mass space velocity was 1.0 h -1 ; Product analysis is the same as in Example 1.

[0090] Example 19: Reaction conditions, raw materials, temperature, pressure, space velocity

[0091] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor hydroquinone was 0.1%, the reaction temperature was 180°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 0.5 h -1 ; Product analysis is the same as in Example 1.

[0092] Example 20: Reaction conditions, raw materials, temperature, pressure, space velocity

[0093] Catalyst 1 was used in a fixed-bed tubular reactor. The raw material was a 50 wt% aqueous solution of acrylic acid, the mass concentration of the polymerization inhibitor hydroquinone was 0.1%, the reaction temperature was 180°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 5 h -1 ; Product analysis is the same as in Example 1.

[0094] Table 1 below lists the reaction evaluation results of the catalyst prepared by the method of the present invention

[0095]

[0096] From Example 1 and Comparative Example 1, it can be seen that partial reduction is beneficial to improving the conversion rate of acrylic acid and the selectivity of 3-hydroxypropionic acid; from Examples 1, 2 and 3, it can be seen that the reaction activity of the catalyst synthesized using Ce(NO3)3·6H2O as the raw material is slightly higher than that of Ce(SO4)2·4H2O or CeCl3·7H2O; from Examples 1, 4-7, it can be seen that the reaction activity gradually increases with the increase of sulfuric acid concentration and the extension of immersion time, and the activity changes little when the concentration is further increased; from Examples 1, 8-10, it can be seen that the reducing atmosphere, reduction temperature and reduction time have a significant impact on the activity of the catalyst, and suitable reaction conditions are required; from Examples 1 and 11, 12, 19 and 20, it can be seen that the lower the concentration of the reactant raw materials and the smaller the weight hourly space velocity, the higher the reaction activity; from Examples 1, 13 and 14, it can be seen that the inhibitor has little effect on the conversion rate of acrylic acid, while the selectivity of 3-hydroxypropionic acid is slightly different; from Examples 1, 15-18, it can be seen that under appropriate conditions, the higher the reaction temperature and the greater the pressure, the higher the reaction activity, and further increasing the temperature and pressure does not change much in the reaction efficiency.

Claims

1. A method for preparing a solid superacid catalyst, characterized in that: The solid super acid catalyst comprises an active component and a carrier, wherein the active component is sulfate ion and the carrier is a partially reduced rare earth Ce oxide; the content of the active component is 5-50wt%; The preparation of the solid superacid catalyst comprises the following steps: (1) Preparation of carrier precursor: Prepare the raw salt into an aqueous solution, adjust the pH value of the solution and stir to form a gel, wash with water, dry and calcine to obtain the carrier precursor. The raw salt is one or more of Ce(NO3)3·6H2O, Ce(SO4)2·4H2O or CeCl3·7H2O, and the pH adjuster is ammonia water with a pH value of 9-12. Stir for 8-16 h and wash with deionized water until neutral. (2) Active component loading: The carrier precursor is added to a sulfuric acid aqueous solution, and the catalyst precursor is obtained after impregnation, filtration, drying, and calcination. The concentration of the sulfuric acid solution used is 0.5-2 mol / L; (3) Partial reduction: The catalyst precursor is partially reduced in a reducing atmosphere to obtain a catalyst for the hydration of acrylic acid to 3-hydroxypropionic acid. The reducing atmosphere is hydrogen or a mixture of hydrogen and an inert atmosphere gas, wherein the volume proportion of hydrogen in the mixture is 10-90%. The reduction temperature is 300-450 °C and the reduction time is 2-8 h.

2. The method according to claim 1, characterized in that: The active component content is 10-40wt%.

3. The method according to claim 1, wherein: In step (1), the pH value is 10-11, stirring is performed for 10-12 h, drying is performed at 110-130 °C for 6-12 h, and calcination is performed at 400-650 °C for 2-8 h.

4. The method according to claim 3, characterized in that: Calcinate at 450-550℃ for 4-6 hours.

5. The method according to claim 1, characterized in that: In step (2), after impregnation at room temperature for 1-10 h, the solid product is filtered to obtain a solid product, dried at 110-130 °C for 6-12 h, and calcined at 400-650 °C for 2-8 h to obtain a catalyst precursor.

6. The method according to claim 5, characterized in that: After soaking at room temperature for 4-6 hours, the solid product was filtered and calcined at 450-550°C for 4-6 hours.

7. The method according to claim 1, characterized in that: In step (3), the inert atmosphere gas is one or more of nitrogen, argon or helium, and the volume proportion of hydrogen in the mixed gas is 20-60%; the reduction temperature is 300-400 °C; and the reduction time is 2-4 h.

8. The method according to claim 1, characterized in that: The ratio of raw material salt to water for preparing aqueous solution is 1.0-10 g:100 mL.

9. A solid super acid catalyst obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the solid superacid catalyst according to claim 9 in a process for catalyzing the hydration of acrylic acid to prepare 3-hydroxypropionic acid.

11. The use according to claim 10, 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; and the mass space velocity is 0.5-5h based on the mass of the raw material. -1 .

12. The use according to claim 11, characterized in that: The raw material is an aqueous solution of acrylic acid with a mass concentration of 25-50%, and the mass ratio of the polymerization inhibitor to acrylic acid is 0.05-0.2%; the reaction temperature is 120-180 ℃; the reaction pressure is 0.5-1.5 MPa; based on the mass of the raw material, the mass space velocity is 0.75-2h -1 .

Images