A composite catalyst for preparing 3-hydroxybutyraldehyde by condensation of acetaldehyde, and a preparation method and application thereof

Abstract

The application discloses a composite catalyst for preparing 3-hydroxybutyraldehyde through acetaldehyde condensation as well as a preparation method and application of the composite catalyst, wherein an active component is MgCr2O4, and a carrier is SiO2 or activated carbon. The application further discloses a preparation method of the catalyst, which comprises the following steps: preparing MgCr2O4 by using a molten salt method and a high-temperature calcination method, mixing the MgCr2O4 with SiO2 or activated carbon, and obtaining the catalyst after calcination.

Description

Technical Field

[0001] This application relates to a composite catalyst for the condensation of acetaldehyde to prepare 3-hydroxybutyraldehyde, its preparation method and application, belonging to the field of chemical engineering. Background Technology

[0002] Aldol condensation can be carried out under acidic or alkaline conditions. Homogeneous (liquid phase) or heterogeneous (gas phase, solid phase, liquid-solid phase) aldol condensation has been studied. In particular, the gas-solid phase aldol condensation under the action of solid catalyst to prepare butenal has been industrialized, and the downstream products are all important basic chemical raw materials. However, there is less research on the gas-solid phase reaction of acetaldehyde. Since it can promote the development of green catalysis, it is a research hotspot in the field of acetaldehyde aldol condensation reaction.

[0003] The homogeneous aldol condensation reaction uses NaOH solution as a catalyst in a liquid phase. The degree of condensation is mainly controlled by the contact time between the NaOH solution and the acetaldehyde solution, and further condensation is stopped by adding acetic acid to neutralize the catalytic effect of NaOH. It has been reported that the condensation reaction temperature is controlled at 40-50℃, the reaction pressure at 0.05 MPa, and the condensation rate at 60-65%. This technology is relatively mature, but due to the inherent corrosiveness and salt residue treatment issues, a greener and cleaner production process needs to be developed.

[0004] Chinese invention patent (CN100450986C) discloses a method for preparing 1,3-butanediol, which first prepares 3-hydroxybutanal by adding a small amount of carboxylic acid to sodium hydroxide, and then hydrogenates it to prepare 1,3-butanediol. Chinese invention patent (CN1807381A) discloses a method for preparing butenal, which uses a weak base organic amine as a catalyst to condense acetaldehyde to generate 2-hydroxybutanal, and then dehydrates 2-hydroxybutanal under acidic conditions to form butenal. Chinese invention patents (CN105585448A), (CN110790634A), (CN206396080U), and (CN208883742U) disclose a two-step process for preparing 1,3-butanediol from acetaldehyde using acetaldehyde as a raw material, first condensing it under an alkaline catalyst to generate 3-hydroxybutanal, and then hydrogenating it. The aforementioned patents all employ batch reactors and liquid alkalis (such as NaOH, KOH, LiOH, trimethylamine, and triethylamine) as catalysts. Due to the high viscosity of 3-hydroxybutyraldehyde and its tendency to dehydrate easily during prolonged contact with the catalyst or at high temperatures, further purification is extremely difficult. Subsequent product refining processes are cumbersome, increasing production costs and significantly impacting product purity and price. Therefore, developing a solid catalyst for the acetaldehyde-hydroxyallocondensation reaction to prepare 3-hydroxybutyraldehyde using a fixed-bed reactor is of great significance. Summary of the Invention

[0005] The catalyst prepared in this application is used in the reaction of acetaldehyde condensation to prepare 3-hydroxybutyraldehyde. The catalyst is sintered at high temperature, has high crystallinity and good activity, and has high acetaldehyde conversion rate and 3-hydroxybutyraldehyde selectivity, as well as good stability.

[0006] According to one aspect of this application, a composite catalyst for the condensation of acetaldehyde to prepare 3-hydroxybutyraldehyde is provided, comprising a support and an active component supported on the surface of the support;

[0007] The carrier is selected from SiO2 and / or activated carbon;

[0008] The active component is selected from MgCr2O4.

[0009] In the composite catalyst, the mass ratio of the active component to the support is 1.6 to 25.5.

[0010] Optionally, in the composite catalyst, the mass ratio of the active component to the support is any value from 1.6, 2, 5, 10, 15, 20, 25, 25.5 or any range between the two.

[0011] According to another aspect of this application, a method for preparing the above-mentioned composite catalyst for the condensation of acetaldehyde to 3-hydroxybutyraldehyde is provided, comprising the following steps:

[0012] (1) Mix raw materials containing magnesium source, chromium source, molten salt and ethanol, dry and calcine to obtain MgCr2O4;

[0013] (2) Mix the MgCr2O4 obtained in (1) with the support II and calcine II to obtain the composite catalyst for the preparation of 3-hydroxybutyraldehyde by acetaldehyde condensation.

[0014] The magnesium source is selected from at least one of magnesium nitrate, magnesium oxide, and magnesium hydroxide;

[0015] The chromium source is selected from at least one of chromium nitrate, chromium oxide, and chromium hydroxide;

[0016] The molar ratio of the magnesium source to the chromium source is (0.9-1):2;

[0017] Optionally, the molar ratio of the magnesium source and the chromium source is any value among 0.9:2, 0.95:2:1:2, or any range between the two.

[0018] The molar ratio of the magnesium source to the molten salt is 1:(0.9~1);

[0019] Optionally, the molar ratio of the magnesium source to the molten salt is any value among 1:0.9, 1:0.95, and 1:1, or any range between two of them.

[0020] The molten salt is selected from KCl-NaCl and / or KCl-ZnCl2;

[0021] The molar ratio of KCl to NaCl is (0-1):1;

[0022] Optionally, the molar ratio of KCl to NaCl is 0:1, 0.5:1, or 1:1.

[0023] The molar ratio of KCl to ZnCl2 is (0-1):1.

[0024] Optionally, the molar ratio of KCl to ZnCl2 is 0:1, 0.5:1, or 1:1.

[0025] The mixture I includes ultrasonic grinding and mixing;

[0026] The drying temperature is 80–110°C;

[0027] Optionally, the drying temperature is any value among 80°C, 90°C, 100°C, and 110°C, or a range between any two.

[0028] The drying time is 2 to 5 hours;

[0029] Optionally, the drying time is any value among 2h, 3h, 4h, and 5h, or a range between any two.

[0030] The calcination temperature I is 600–1200°C;

[0031] Optionally, the calcination temperature I is any value among 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, and 1200℃, or a range between any two.

[0032] The calcination time is 4 to 8 hours.

[0033] Optionally, the calcination time I is any value among 4h, 5h, 6h, 7h, and 8h, or a range between any two.

[0034] The molar ratio of MgCr2O4 obtained in (1) to the support is (0.5-8):1;

[0035] Optionally, the molar ratio of MgCr2O4 obtained in (1) to the support is any value among 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or any range between the two.

[0036] The mixing method II is selected from mechanical mixing or wet mixing;

[0037] The calcination temperature II is 500–600°C;

[0038] Optionally, the calcination temperature II is any value among 500°C, 550°C, and 600°C, or a range between any two.

[0039] The calcination time for II is 2–6 hours;

[0040] Optionally, the calcination time II is any value among 2h, 3h, 4h, 5h, and 6h, or a range between any two.

[0041] The atmosphere for calcination II is a non-reactive gas atmosphere;

[0042] The inactive gas is selected from at least one of nitrogen, helium, and argon.

[0043] After calcination II, the mixture is washed with deionized water until it is no longer turbid when tested with AgNO3, and then dried.

[0044] Specifically, the synthesis method of the composite catalyst includes the following steps:

[0045] (1) Mix magnesium source, chromium source, molten salt and ethanol in a certain molar ratio, sonicate and grind for a period of time, and then dry in an oven for a period of time.

[0046] (2) Place the sample obtained in step (1) in a high-temperature furnace for a period of time, wash it with deionized water until no turbidity can be detected by AgNO3, and dry it to obtain MgCr2O4.

[0047] (3) The prepared MgCr2O4 is mixed with SiO2 or activated carbon at a certain molar ratio and calcined for a period of time to obtain the composite catalyst.

[0048] According to another aspect of this application, a method for preparing 3-hydroxybutyraldehyde by acetaldehyde condensation reaction is provided, comprising the following steps:

[0049] In a reactor, a raw material containing an aqueous solution of acetaldehyde is introduced and reacted with a catalyst to obtain a product containing 3-hydroxybutyraldehyde.

[0050] The catalyst is selected from the composite catalyst for the preparation of 3-hydroxybutyraldehyde by acetaldehyde condensation described above or the composite catalyst for the preparation of 3-hydroxybutyraldehyde by acetaldehyde condensation prepared by the above preparation method.

[0051] In the acetaldehyde aqueous solution, the mass ratio of acetaldehyde to water is 3:1 to 3:9;

[0052] Optionally, the mass ratio of acetaldehyde to deionized water is any value among 3:1, 3:3, 3:6, and 3:9, or any range between the two.

[0053] The mass hourly space velocity (MSV) of the raw material is 0.1–1.5 h⁻¹. -1 ;

[0054] Optionally, the mass-to-mass ratio of the mass space velocity is 0.1h. -1 0.3h -1 0.5h -1 0.7h -1 0.9h -1 1.1h -1 1.3h -1 1.5h -1 Any value in the range or any value between the two.

[0055] The reaction temperature is 15–45°C;

[0056] Optionally, the temperature of the reaction is any value of 15°C, 25°C, 35°C, 45°C, or a range between any two.

[0057] The reaction time is 2 to 3 hours.

[0058] Optionally, the reaction time is any value of 2h or 3h, or a range between both.

[0059] The reactor is a fixed-bed reactor.

[0060] The beneficial effects that this application can produce include:

[0061] 1) The catalyst provided in this application can be applied to the acetaldehyde condensation reaction to prepare 3-hydroxybutyraldehyde, and improves the conversion rate of acetaldehyde and the selectivity of the generated 3-hydroxybutyraldehyde.

[0062] 2) The preparation method of the catalyst provided in this application is stable, controllable, and reproducible.

[0063] 3) The method for preparing 3-hydroxybutyraldehyde by acetaldehyde condensation 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

[0064] Figure 1 Catalyst 1 # X-ray powder diffraction pattern of MgCr2O4 in [the sample]. Detailed Implementation

[0065] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0066] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0067] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially. The gas chromatograph used was an Agilent 7890B gas chromatograph.

[0068] Examples 1-28

[0069] Preparation of catalysts

[0070] Magnesium oxide, chromium oxide, and molten salt (with a molar ratio of 1:2, KCl-ZnCl2 at a molar ratio of 0.5:1, and a molar ratio of 1:1 for magnesium oxide and KCl-ZnCl2) were mixed in an ethanol solution. The mixture was ultrasonically sonicated and then ground for a period of time. It was then dried in a 100°C oven for 4 hours. Afterward, it was calcined in a high-temperature furnace at 1000°C for 4 hours. The mixture was washed with deionized water until no turbidity was detected by AgNO3, and then dried to obtain MgCr2O4. The MgCr2O4 sample was then mixed with SiO2 at a specific molar ratio of 5:1 using a wet mixing method and calcined at 500°C for 4 hours to obtain the composite catalyst 1. # .

[0071] 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:

[0072] Table 1

[0073]

[0074]

[0075] Table 2

[0076]

[0077]

[0078] The explanations for columns 1 and 2 above are as follows:

[0079] Magnesium sources: magnesium nitrate (Mg1), magnesium oxide (Mg2), magnesium hydroxide (Mg3).

[0080] Chromium sources: chromium nitrate (Cr1), chromium oxide (Cr2), chromium hydroxide (Cr3).

[0081] Molten salts: KCl-NaCl (molten 1), KCl-ZnCl2 (molten 2).

[0082] Mixing methods: mechanical mixing (method 1), wet mixing (method 2).

[0083] XRD characterization

[0084] Catalyst 1 was analyzed using a Miniflex 600 X-ray diffractometer with a Cu target. # Powder diffraction yielded catalyst 1. # The MgCr2O4 diffraction peaks in the sample conform to the characteristic peaks of MgCr2O4 (e.g., Figure 1 (As shown).

[0085] Gas chromatography characterization

[0086] The composition of the acetaldehyde condensation reaction products was analyzed using an Agilent 7890B gas chromatograph (FID detector, HP-5 capillary column).

[0087] The conversion rate and selectivity calculation formulas in the embodiments of this application are as follows (using acetaldehyde conversion rate as the evaluation index):

[0088] Acetaldehyde conversion rate = (initial carbon number of acetaldehyde - carbon number of acetaldehyde in the product) * 100 / initial molar number of acetaldehyde

[0089] 3-Hydroxybutyraldehyde selectivity = (number of carbon atoms in 3-hydroxybutyraldehyde) * 100 / ∑(number of carbon atoms in 3-hydroxybutyraldehyde + number of carbon atoms in other products)

[0090] Application Example 1

[0091] The catalyst is used in the acetaldehyde condensation reaction to prepare 3-hydroxybutyraldehyde.

[0092] Catalysts 1-28 prepared in Examples 1-28 # ~Catalyst 28 # This compound was used to prepare 3-hydroxybutyraldehyde by acetaldehyde condensation. The mass ratio of acetaldehyde to deionized water in the raw materials was 3:3. The reaction was carried out at a temperature of 35°C for 2 hours and a mass hourly space velocity (HHSV) of 0.5 h⁻¹. -1 The raw materials are fed into a fixed-bed reactor containing 3g of the catalyst, and a condensation reaction is carried out to produce 3-hydroxybutyraldehyde.

[0093] After the reaction stabilized, both the reactants and products were analyzed using online gas chromatography. The results are shown in Table 3.

[0094] Table 3

[0095]

[0096]

[0097] Application Example 2

[0098] Catalyst 1 prepared using the catalysts in Tables 1-2 # The reaction to prepare 3-hydroxybutyraldehyde by acetaldehyde condensation was carried out. After the reaction parameters were changed and the reaction stabilized, the reactants and products were analyzed by online gas chromatography. The reaction results are shown in Table 4.

[0099] Table 4

[0100]

[0101]

[0102] 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-hydroxybutyraldehyde by acetaldehyde condensation reaction, characterized in that, Includes the following steps: In a reactor, a raw material containing an aqueous solution of acetaldehyde is introduced and reacted with a catalyst to obtain a product containing 3-hydroxybutyraldehyde. In the acetaldehyde aqueous solution, the mass ratio of acetaldehyde to water is 3:1 to 3:9; The mass hourly space velocity (MSV) of the raw material is 0.1 ~ 0.9 h. -1 ; The reaction temperature is 25~45℃; The catalyst comprises a support and an active component supported on the surface of the support; The carrier is selected from SiO2 and / or activated carbon; The active component is selected from MgCr2O4; The mass ratio of the active component to the carrier is 1.6 to 25.

5.

2. The method for preparing 3-hydroxybutyraldehyde by acetaldehyde condensation reaction according to claim 1, wherein the catalyst preparation method comprises the following steps: (1) Mix raw materials containing magnesium source, chromium source, molten salt and ethanol, dry and calcine to obtain MgCr2O4; (2) Mix the MgCr2O4 obtained in (1) with the support II and calcine II to obtain a composite catalyst for the preparation of 3-hydroxybutyraldehyde by acetaldehyde condensation.

3. The method according to claim 2, characterized in that, The magnesium source is selected from at least one of magnesium nitrate, magnesium oxide, and magnesium hydroxide; The chromium source is selected from at least one of chromium nitrate, chromium oxide, and chromium hydroxide.

4. The method according to claim 2, characterized in that, The molar ratio of the magnesium source to the chromium source is (0.9~1):2; The molar ratio of the magnesium source to the molten salt is 1:(0.9~1). The molten salt is selected from KCl-NaCl and / or KCl-ZnCl2; The molar ratio of KCl to NaCl is (0~1):1; The molar ratio of KCl to ZnCl2 is (0~1):

1.

5. The method according to claim 2, characterized in that, The mixture I includes ultrasonic grinding and mixing; The drying temperature is 80~110℃; The drying time is 2-5 hours; The calcination temperature I is 600~1200℃; The calcination time is 4-8 hours.

6. The method according to claim 2, characterized in that, The molar ratio of MgCr2O4 obtained in (1) to the support is (0.5~8):1; The mixing method II is selected from mechanical mixing. The calcination temperature II is 500~600℃; The calcination time for II is 2-6 hours; The atmosphere for calcination II is a non-reactive gas atmosphere; The inactive gas is selected from at least one of nitrogen, helium, and argon.

7. The method according to claim 2, characterized in that, The molar ratio of MgCr2O4 obtained in (1) to the support is (0.5~8):1; The mixture II is selected from the wet mixing method; The calcination temperature II is 500~600℃; The calcination time for II is 2-6 hours; The atmosphere for calcination II is a non-reactive gas atmosphere; The inactive gas is selected from at least one of nitrogen, helium, and argon.

8. The method according to claim 2, characterized in that, After calcination II, the mixture is washed with deionized water until it is no longer turbid when tested with AgNO3, and then dried.

9. The method according to claim 1, characterized in that, The reaction time for the acetaldehyde condensation reaction to prepare 3-hydroxybutyraldehyde is 2-3 hours.

10. The method according to claim 1, characterized in that, The reactor used for the acetaldehyde condensation reaction to prepare 3-hydroxybutyraldehyde is a fixed-bed reactor.

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