A catalyst, its preparation method and application

Abstract

This application discloses a catalyst, its preparation method, and its application. The catalyst is used for the oxidative preparation of 3-hydroxybutyric acid; it includes an active component and a support; the active component is CoCr2O4; the support is ZSM-5 molecular sieve; and the mass ratio of the active component to the support is 0.2–0.5:1. The catalyst provided in this application can be applied to the oxidative preparation of 3-hydroxybutyric acid, improving the conversion rate of 3-hydroxybutyraldehyde and the selectivity of the generated 3-hydroxybutyric acid. It exhibits a fast reaction rate, high yield, and can be applied to large-scale production. The catalyst preparation method is stable, controllable, and reproducible.

Description

Technical Field

[0001] This application relates to a catalyst, its preparation method, and its application, and belongs to the field of chemical engineering. Background Technology

[0002] 3-Hydroxybutyric acid (PHB) is an important monomer for the preparation of biodegradable plastics. Its polymer, poly(3-hydroxybutyrate) (PHB), possesses high melting point, high crystallinity, and tensile strength (almost identical to polypropylene), along with complete biodegradability, biocompatibility, UV resistance, and low oxygen permeability. Therefore, PHB can partially replace general-purpose plastics in environmental protection materials and packaging materials, especially in single-use plastic products. Furthermore, it has unique applications in biofunctional materials and medical devices. Thus, the chemical synthesis research of 3-hydroxybutyric acid has significant environmental and economic implications.

[0003] Currently, the preparation of 3-hydroxybutyric acid using biochemical or fermentation methods is costly, has low yield, and is expensive. Hydrolysis produces few byproducts, but the cyanide is highly toxic and pollutes the environment. Acetaldehyde and acetic acid prepared under lithium naphthylene catalysis have readily available raw materials, few side reactions, and are easily scalable for continuous production. While lithium naphthylene is used in large quantities, it only acts as a catalyst and can be reused, thus holding potential for industrial production. Oxidation methods, due to the presence of hydroxyl groups in the raw materials, require relatively low temperatures and pressures. 3-hydroxybutyric acid is not yet produced on a large industrial scale; it must be prepared from acetaldehyde via an aldol condensation reaction. This method is the preferred approach for industrialization. Summary of the Invention

[0004] The catalyst prepared in this patent is used in the oxidation preparation of 3-hydroxybutyric acid. The catalyst has good activity, high conversion rate of 3-hydroxybutyraldehyde and selectivity of 3-hydroxybutyric acid, and good stability.

[0005] According to one aspect of this application, a catalyst is provided for the oxidation reaction to prepare 3-hydroxybutyric acid, and the catalyst improves the conversion of 3-hydroxybutyraldehyde and the selectivity of 3-hydroxybutyric acid;

[0006] The catalyst includes an active component and a support;

[0007] The active component is CoCr2O4;

[0008] The carrier is ZSM-5 molecular sieve;

[0009] The mass ratio of the active component to the carrier is 0.2 to 0.5:1.

[0010] The mass ratio of the active component to the carrier is selected from 0.2:1, 0.3:1, 0.4:1, and 0.5:1.

[0011] According to another aspect of this application, a method for preparing the above-mentioned catalyst is provided, comprising the following steps:

[0012] The active component is obtained by mixing raw materials containing cobalt source, chromium source and solvent, ultrasonically grinding, drying and calcining.

[0013] The active component is mixed with the support and calcined to obtain the catalyst.

[0014] The cobalt source is selected from at least one of cobalt monoxide, cobalt oxalate, and cobalt hydroxide.

[0015] The chromium source is selected from chromium trioxide and / or chromium powder;

[0016] The molar ratio of the cobalt source to the chromium source is 0.9 to 2:2;

[0017] The upper limit of the molar ratio of the cobalt source to the chromium source is selected from 2:2 and 1.9:2, and the lower limit is selected from 0.9:2 and 1:2.

[0018] Wherein, the molar amount of the cobalt source is expressed in terms of the molar amount of cobalt element;

[0019] The molar amount of the chromium source is expressed in terms of the molar amount of chromium element;

[0020] The solvent is selected from at least one of methanol, ethanol, or acetone;

[0021] Furthermore, the solvent is ethanol.

[0022] The solid-liquid ratio of the total mass of the cobalt source and the chromium source to the volume of the solvent is 1:10-30 g / ml;

[0023] The upper limit of the solid-liquid ratio of the total mass of the cobalt source and the chromium source to the volume of the solvent is selected from 1:10 g / ml and 1:20 g / ml, and the lower limit is selected from 1:30 g / ml and 1:20 g / ml.

[0024] The drying temperature is 80–110°C; the drying temperature is any value among 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, and 110°C, or a range between any two.

[0025] The drying time is 2 to 5 hours; the drying time is any value among 2 hours, 3 hours, 4 hours, and 5 hours, or a range between any two.

[0026] The roasting temperature is 600–1200°C; the roasting temperature is any value or a range between any two of 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, and 1200°C.

[0027] The roasting time is 4 to 8 hours; the roasting time is any value among 4 hours, 5 hours, 6 hours, 7 hours, and 8 hours, or any range between two of them.

[0028] The mixing method of the active component and the carrier is selected from either mechanical mixing or wet mixing.

[0029] The calcination temperature is 500-600℃; the calcination temperature is any value among 500℃, 550℃, and 600℃, or any range between two of them.

[0030] The calcination time is 2 to 6 hours; the calcination time is any value among 2 hours, 3 hours, 4 hours, 5 hours, and 6 hours, or a range between any two.

[0031] According to another aspect of this application, a method for preparing 3-hydroxybutyric acid is provided, comprising the following steps:

[0032] A mixture containing oxygen and 3-hydroxybutyraldehyde is reacted with a catalyst to obtain a product containing 3-hydroxybutyric acid.

[0033] The catalyst is selected from the catalysts described above or the catalysts prepared by the methods described above.

[0034] Furthermore, in a fixed-bed reactor, a mixture containing oxygen and 3-hydroxybutyraldehyde is introduced and reacted to obtain a product containing 3-hydroxybutyric acid.

[0035] The fixed-bed reactor is filled with a catalyst;

[0036] The oxygen flow rate is 0.1 to 0.5 L / min; the oxygen flow rate is any value among 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, and 0.5 L / min, or a range between any two.

[0037] The mass ratio of the catalyst to the 3-hydroxybutyraldehyde is 0.2 to 1:100; the mass ratio of the catalyst to the 3-hydroxybutyraldehyde is selected from 0.2:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, and 1:100.

[0038] The reaction temperature is 40–80°C; the reaction temperature is any value among 40°C, 50°C, 60°C, 70°C, and 80°C, or a range between any two.

[0039] The reaction time is 3 to 6 hours; the reaction time is any value among 3 hours, 4 hours, 5 hours, and 6 hours, or any range between two of them.

[0040] The 3-hydroxybutyraldehyde is an aqueous solution with a mass fraction of 20 to 50 wt%; the 3-hydroxybutyraldehyde is any value among 20 wt%, 30 wt%, 40 wt%, and 50 wt% or any range between two of them.

[0041] The beneficial effects that this application can produce include:

[0042] 1) The catalyst provided in this application can be applied to the reaction of oxidative preparation of 3-hydroxybutyric acid, and improves the conversion rate of 3-hydroxybutyraldehyde and the selectivity of the generated 3-hydroxybutyric acid.

[0043] 2) The preparation method of the catalyst provided in this application is stable, controllable, and reproducible.

[0044] 3) The method for preparing 3-hydroxybutyric acid by oxidation provided in this application uses the catalyst provided in this application, which has a fast reaction rate and high yield, and can be applied to large-scale production. Attached Figure Description

[0045] Figure 1 Catalyst 1 # X-ray powder diffraction pattern of the active component CoCr2O4. Detailed Implementation

[0046] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0047] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0048] The gas chromatograph used was an Agilent 7890B gas chromatograph.

[0049] Example 1

[0050] Preparation of catalysts

[0051] Taking sample 1 in Table 1 as an example, cobalt monoxide and chromium trioxide with a molar ratio of 2:2 were mixed in an ethanol solution (solid-liquid ratio of 1:20 g / ml), ultrasonicated, ground, and dried in an oven at 100℃ for 4 hours; then calcined in a high-temperature furnace at 1000℃ for 4 hours to obtain CoCr2O4 sample 1. # Sample 1 of CoCr2O4 # The composite catalyst, denoted as catalyst 1, is obtained by wet mixing with ZSM-5 molecular sieve at a mass ratio of 0.3:1 and calcining at 500℃ for 4 hours.# .

[0052] Following the steps below, adjust the type and amount of each raw material and the reaction parameters to obtain a series of catalysts numbered 2 to 28, denoted as catalyst 2. # ~Catalyst 28 # As shown in Table 1 below:

[0053] Table 1

[0054]

[0055]

[0056]

[0057] The explanations for each column in Table 1 above are as follows:

[0058] Cobalt sources: cobalt monoxide (Co1), cobalt oxalate (Co2), cobalt hydroxide (Co3).

[0059] Chromium sources: Chromium trioxide (Cr1), chromium powder (Cr2).

[0060] Solvents: methanol (solution 1), ethanol (solution 2), acetone (solution 3).

[0061] Calcination: Calcination during the preparation of CoCr2O4.

[0062] Calcination: Calcination of CoCr2O4 mixed with a support.

[0063] XRD characterization

[0064] Catalyst 1 was analyzed using a Miniflex 600 X-ray diffractometer with a Cu target. # The active component CoCr2O4 powder was diffracted to obtain catalyst 1. # The diffraction peaks of the active component CoCr2O4 conform to the characteristic peaks of CoCr2O4 (e.g. Figure 1 (As shown).

[0065] Example 2

[0066] The catalyst is used in the oxidation reaction to prepare 3-hydroxybutyric acid.

[0067] Catalysts 1 to 28 prepared in Example 1 # ~Catalyst 28 # In the oxidation preparation of 3-hydroxybutyric acid, the reaction temperature was 60℃, the reaction time was 5h, the O2 flow rate was 0.3L / min, the mass fraction of the 3-hydroxybutyraldehyde aqueous solution was 50%, and the mass ratio of catalyst to raw material was 1:100.

[0068] After the reaction stabilized, both the reactants and products were analyzed using online gas chromatography. The results are shown in Table 2. It can be seen that under the same reaction conditions, catalyst 1... # It has the highest yield in the oxidation preparation of 3-hydroxybutyric acid.

[0069] Table 2

[0070]

[0071]

[0072] Example 3

[0073] Catalyst 1 prepared in Table 1 # The oxidation reaction to prepare 3-hydroxybutyric acid was carried out. After the reaction parameters were varied and the reaction stabilized, both the reactants and products were analyzed using online gas chromatography. The results are shown in Table 3. It can be seen that the mass ratio of catalyst to reactants has a significant impact on the yield of the oxidation reaction to prepare 3-hydroxybutyric acid.

[0074] Table 3

[0075]

[0076]

[0077] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing 3-hydroxybutyric acid, characterized in that, Includes the following steps: A mixture containing oxygen and 3-hydroxybutyraldehyde is reacted with a catalyst to obtain a product containing 3-hydroxybutyric acid. The oxygen flow rate is 0.1~0.5 L / min; The reaction temperature is 40~70℃; The catalyst includes an active component and a support; The active component is CoCr2O4; The carrier is ZSM-5 molecular sieve; The mass ratio of the active component to the carrier is 0.2~0.5:1; The mass ratio of the catalyst to the 3-hydroxybutyraldehyde is 0.5~1:

100.

2. A preparation method according to claim 1, characterized in that, The catalyst preparation method includes the following steps: The active component is obtained by mixing raw materials containing cobalt source, chromium source and solvent, drying and calcining. The active component is mixed with the support and calcined to obtain the catalyst.

3. The preparation method according to claim 2, characterized in that, The cobalt source is selected from at least one of cobalt monoxide, cobalt oxalate, or cobalt hydroxide. The chromium source is selected from chromium trioxide and / or chromium powder; The molar ratio of the cobalt source to the chromium source is 0.9~2:2; Wherein, the molar amount of the cobalt source is expressed in terms of the molar amount of cobalt element; The molar amount of the chromium source is expressed in terms of the molar amount of chromium element; The solvent is selected from at least one of methanol, ethanol, or acetone; The solid-liquid ratio of the total mass of the cobalt source and the chromium source to the volume of the solvent is 1:10~30 g / ml.

4. The preparation method according to claim 2, characterized in that, The drying temperature is 80~110℃; The drying time is 2-5 hours.

5. The preparation method according to claim 2, characterized in that, The roasting temperature is 600~1200℃; The roasting time is 4 to 8 hours.

6. The preparation method according to claim 2, characterized in that, The calcination temperature is 500~600℃; The calcination time is 2-6 hours.

7. The preparation method according to claim 1, characterized in that, The reaction time is 3-6 hours.

8. The preparation method according to claim 1, characterized in that, The 3-hydroxybutyraldehyde is an aqueous solution with a mass fraction of 20~50wt%.

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