A catalyst for the condensation of butyraldehyde to octenal, its preparation method and application

Abstract

This application discloses a catalyst for the condensation of butyraldehyde to octenal, its preparation method, and its application. The catalyst comprises hollow Al₂O₃ and CoCr₂O₄ in a mass ratio of (10-20):1. This application also discloses a method for preparing the catalyst, comprising preparing CoCr₂O₄ using a molten salt method and a high-temperature calcination method, then mixing it with hollow Al₂O₃ and calcining it to obtain the catalyst. This application further discloses a method for using the catalyst to perform the butyraldehyde condensation reaction to prepare octenal.

Description

Technical Field

[0001] This application relates to a catalyst for the condensation of butyraldehyde to octenal, its preparation method, and its application, belonging to the field of chemical engineering. Background Technology

[0002] The self-condensation reaction of n-butyraldehyde, as a type of aldol condensation reaction, mainly has the following problems: (1) the selectivity of structure selection, regio selection and chemoselectivity is relatively low during the aldehyde alcoholization process; (2) the molecule is prone to dehydration to form α,β-unsaturated carbonyl compounds, which further generate oligomers or even polymers, reducing the selectivity of the main reaction. Therefore, many side reactions accompany the reaction process, reducing the selectivity and yield of the target product. Therefore, selecting a suitable catalyst is the key to achieving high selectivity and high yield of octenal. According to the acid-base active centers they possess, the catalysts used in aldol condensation reactions can be divided into acid catalysts, basic catalysts and acid-base bifunctional catalysts.

[0003] Solid base catalysts have become a focus of research due to their high activity, high selectivity, and ease of separation. Literature reports that solid base catalysts used for the aldol condensation of n-butyraldehyde are mainly metal oxides and supported organic solid bases, achieving activity and selectivity similar to liquid bases. However, their poor stability and difficulty in reusing hinder their industrial application. Solid acids have been reported in some aldol condensation reactions, demonstrating not only high catalytic activity but also good stability, showing broad prospects for industrial application. However, research reports on the application of solid acids in the self-condensation of n-butyraldehyde are limited.

[0004] Currently, liquid alkali NaOH is used in industry to catalyze the aldol condensation reaction of n-butyraldehyde. Although a high yield and selectivity of octenal can be obtained, this process is essentially still a catalytic reaction of n-butyraldehyde in an alkaline environment, and still has the following four disadvantages: (1) If the concentration of liquid alkali is too low, the condensation reaction is not complete and the conversion rate is low; (2) If the concentration of liquid alkali is too high, the aldol condensation reaction is more intense, and trimers or polymers are easily generated, resulting in more by-products and lower selectivity; (3) The discharge of alkaline wastewater is large, which pollutes the environment and incurs high treatment costs; (4) The cost is high because a large amount of NaOH is lost with the wastewater, resulting in high catalyst consumption; after the reaction, the aqueous phase contains a large amount of product, which needs to be extracted by processes such as extraction, which increases costs; and the treatment of wastewater requires a large amount of acid, which increases costs. Summary of the Invention

[0005] This patent constructs a solid bifunctional catalyst CoCr2O4-Al2O3, which is of great significance for developing a solid catalyst in the reaction of butyraldehyde-hydroxyaldehyde condensation to prepare octenal using a fixed-bed reactor. The catalyst has good activity, high butyraldehyde conversion rate and octenal selectivity, and good stability.

[0006] According to one aspect of this application, a catalyst for the condensation of butyraldehyde to octenal is provided, which can be applied to the reaction of butyraldehyde condensation to octenal and improve the conversion rate of butyraldehyde and the selectivity of octenal.

[0007] The catalyst comprises hollow Al2O3 and CoCr2O4;

[0008] In the catalyst, the mass ratio of CoCr2O4 to hollow Al2O3 is 1:(10-20).

[0009] According to another aspect of this application, a method for preparing the above-mentioned catalyst for the condensation of butyraldehyde to octenal is provided, comprising the following steps:

[0010] (1) Mix raw materials containing cobalt source, chromium source, molten salt and ethanol, dry them, and calcine them to obtain CoCr2O4;

[0011] (2) Mix the CoCr2O4 obtained in (1) with hollow Al2O3, and calcine it to obtain the catalyst used for the condensation of butyraldehyde to octenal.

[0012] The cobalt source is selected from at least one of cobalt nitrate, cobalt oxide, and cobalt hydroxide;

[0013] The chromium source is at least one of chromium nitrate, chromium oxide, and chromium hydroxide;

[0014] The molten salt is selected from a mixture of KCl and NaCl and / or ZnCl2;

[0015] Optionally, the molar ratio of KCl to NaCl and / or ZnCl2 is (0-1):1;

[0016] The molar ratio of the cobalt source to the chromium source is (0.9-1):2; calculated based on the cobalt or chromium element content in the cobalt or chromium source.

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

[0018] The mass ratio of the cobalt source to the molten salt is 1:(1-2).

[0019] Optionally, the mass ratio of the cobalt source to the molten salt is any value of 1:1, 1:2, or any range between the two.

[0020] The mixing I includes ultrasonic and grinding mixing;

[0021] The temperature of the drying process I is 80–110°C;

[0022] Optionally, the temperature of the drying process I is any value among 80°C, 90°C, 100°C, and 110°C, or a range between any two.

[0023] The drying time for step I is 2–5 hours;

[0024] Optionally, the drying time I is any value among 2h, 3h, 4h, and 5h, or a range between any two.

[0025] The calcination temperature I is 600–1200°C;

[0026] Optionally, the calcination temperature I is any value among 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, and 1200℃, or a range between any two.

[0027] The calcination time is 4 to 8 hours.

[0028] Optionally, the calcination time I is any value among 4h, 5h, 6h, 7h, and 8h, or a range between any two.

[0029] The mass ratio of CoCr2O4 obtained in (1) to hollow Al2O3 is 1:(10-20);

[0030] Optionally, the molar ratio of the CoCr2O4 obtained in (1) to the hollow Al2O3 is any value among 1:10, 1:15, and 1:20, or any range between the two.

[0031] The calcination temperature III is 500–600°C;

[0032] Optionally, the calcination temperature III is any value among 500°C, 550°C, and 600°C, or a range between any two.

[0033] The calcination time for the third stage is 4 to 8 hours.

[0034] Optionally, the calcination time III is any value among 4h, 5h, 6h, 7h, and 8h, or a range between any two.

[0035] The hollow Al2O3 is obtained through the following process:

[0036] The raw materials containing carbon spheres, aluminum nitrate, and ethanol are mixed (II), dried (II), and calcined (II) to obtain the hollow Al2O3;

[0037] in,

[0038] The ratio of carbon spheres, aluminum nitrate, and ethanol is 1g:(30-50)g:(200-300)ml;

[0039] Optionally, the ratio of the carbon balls, aluminum nitrate and anhydrous ethanol is any value among 1g:50g:300ml, 1g:40g:250ml, 1g:30g:200ml, or any range between the two.

[0040] The aluminum nitrate mentioned is aluminum nitrate nonahydrate.

[0041] The temperature of the drying II process is 100–120°C;

[0042] Optionally, the temperature of the drying II is any value among 100°C, 110°C, and 120°C, or a range between any two.

[0043] The drying time for step II is 6–12 hours;

[0044] Optionally, the drying time II is any value among 6h, 7h, 8h, 9h, 10h, 11h, and 12h, or a range between any two.

[0045] The calcination temperature II is 500–600°C;

[0046] Optionally, the calcination temperature II is any value among 500°C, 550°C, and 600°C, or a range between any two.

[0047] The calcination time II is 4 to 8 hours.

[0048] Optionally, the calcination time II is any value among 4h, 5h, 6h, 7h, and 8h, or a range between any two.

[0049] The mixing method II is selected from mechanical mixing and / or wet mixing;

[0050] After mixing II and before drying II, ultrasonication and settling were performed.

[0051] The duration of the ultrasound is 10–60 minutes;

[0052] Optionally, the ultrasound duration is any value among 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min, or a range between any two.

[0053] The settling time is 4 to 10 hours.

[0054] Optionally, the settling time is any value among 4h, 5h, 6h, 7h, 8h, 9h, and 10h, or a range between any two.

[0055] Specifically, the preparation method of the composite catalyst includes the following steps:

[0056] (1) Mix cobalt 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.

[0057] (2) Place the sample obtained in step (1) in a high-temperature furnace for a period of time, wash with deionized water until no turbidity can be detected by AgNO3, and dry to obtain CoCr2O4.

[0058] (3) The prepared CoCr2O4 and hollow Al2O3 are mixed at a certain mass ratio II and calcined for a period of time III to obtain the composite catalyst.

[0059] According to another aspect of this application, a method for preparing octenal by butyraldehyde condensation is provided, comprising the following steps:

[0060] In a reactor, a raw material containing butyraldehyde is introduced and reacted with a catalyst to obtain a product containing octenal.

[0061] The catalyst is selected from the above-mentioned catalyst for the condensation of butyraldehyde to octenal or the catalyst for the condensation of butyraldehyde to octenal prepared by the above-mentioned preparation method.

[0062] The reactor is a fixed-bed reactor.

[0063] The space time of the raw material is 0.1–10 g·min / ml;

[0064] Optionally, the space time of the raw material is any value or a range between 0.1 g·min / ml, 0.5 g·min / ml, 1 g·min / ml, 2 g·min / ml, 4 g·min / ml, 6 g·min / ml, 8 g·min / ml, and 10 g·min / ml.

[0065] The reaction temperature is 100–200°C;

[0066] Optionally, the temperature of the reaction is any value or a range between 100°C, 120°C, 140°C, 160°C, 180°C, and 200°C.

[0067] The reaction time is 3 to 5 hours;

[0068] Optionally, the reaction time is any value among 3h, 4h, and 5h, or a range between any two.

[0069] The reaction is carried out at a pressure of 1–5 MPa.

[0070] Optionally, the pressure of the reaction is any value of 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, or a range between any two.

[0071] The beneficial effects that this application can produce include:

[0072] 1) The catalyst provided in this application can be applied to the butyraldehyde condensation reaction to prepare octenal, and improves the conversion rate of butyraldehyde and the selectivity of the generated octenal.

[0073] 2) The preparation method of the catalyst provided in this application is stable, controllable, and reproducible.

[0074] 3) The method for preparing octenal by butyraldehyde 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

[0075] Figure 1 Catalyst 1 # X-ray powder diffraction pattern of CoCr2O4. Detailed Implementation

[0076] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0077] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0078] Examples 1-28

[0079] Preparation of catalysts

[0080] Taking item 1 in Table 1 as an example, cobalt oxide, chromium oxide, and molten salt (cobalt oxide and KCl-ZnCl2 mass ratio of 1:2) with a molar ratio of 1:2 were mixed in an ethanol solution, ultrasonicated, and then ground and mixed for a period of time. The mixture was then dried in a 100℃ oven for 15 hours; subsequently, it was calcined in a high-temperature furnace at 1200℃ for 4 hours. The mixture was washed with deionized water until no turbidity was detected by AgNO3, and then dried to obtain CoCr2O4. Al(NO3)39H2O was weighed and added to anhydrous ethanol solution (the solid-liquid ratio of carbon spheres, Al(NO3)39H2O, and anhydrous ethanol was 1:40:250 g / ml) to prepare an aluminum nitrate ethanol solution. Carbon spheres were added, ultrasonicated for 30 minutes, and then allowed to stand for 6 hours. The mixture was filtered, dried at 110℃ for 8 hours, and then calcined at 550℃ for 4 hours to obtain hollow Al2O3. CoCr2O4 and hollow Al2O3 were mixed at a mass ratio of 1:15 using a wet mixing method, and then calcined at 550℃ for 4 hours to obtain CoCr2O4-Al2O3, which was designated as catalyst 1. # .

[0081] 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:

[0082] Table 1

[0083]

[0084]

[0085] Table 2

[0086]

[0087]

[0088] The explanations for columns 1 and 2 above are as follows:

[0089] Magnesium sources: cobalt nitrate (Co1), cobalt oxide (Co2), cobalt hydroxide (Co3).

[0090] Chromium sources: chromium nitrate (Cr1), chromium oxide (Cr2), chromium hydroxide (Cr3).

[0091] Molten salts: KCl-NaCl (molten 1), KCl-ZnCl2 (molten 2).

[0092] Solvents: methanol (solution 1), ethanol (solution 2), acetone (solution 3).

[0093] Drying I: Drying during the preparation of CoCr2O4.

[0094] Drying II: Drying during the preparation of hollow Al2O3.

[0095] Calcination I: Calcination during the preparation of CoCr2O4.

[0096] Calcination II: Calcination during the preparation of hollow Al2O3.

[0097] Calcination III: Calcination during the preparation of CoCr2O4-Al2O3 catalyst.

[0098] Mixing methods: mechanical mixing (method 1), wet mixing (method 2).

[0099] XRD characterization

[0100] Catalyst 1 was analyzed using a Miniflex 600 X-ray diffractometer with a Cu target. # Powder diffraction yielded catalyst 1.# The diffraction peaks of KTiNbO5 match the characteristic peaks of CoCr2O4 (e.g., Figure 1 (As shown).

[0101] Gas chromatography characterization

[0102] The composition of the butyraldehyde condensation reaction products was analyzed using an Agilent 7890B gas chromatograph (FID detector, HP-5 capillary column).

[0103] The conversion rate and selectivity calculation formulas in the embodiments of this application are as follows (with butyraldehyde conversion rate as the evaluation index):

[0104] Butyraldehyde conversion rate = (initial carbon number of butyraldehyde - carbon number of butyraldehyde in the product) * 100 / initial molar number of butyraldehyde

[0105] Octenal selectivity = (number of carbon atoms in octenal) * 100 / ∑(number of carbon atoms in octenal + number of carbon atoms in other products)

[0106] Application Example 1

[0107] The catalyst is used in the butyraldehyde condensation reaction to prepare octenal.

[0108] Catalysts 1 to 28 prepared in Example 1 # ~Catalyst 28 # The catalyst is used to prepare octenal by butyraldehyde condensation. The reaction is carried out at a temperature of 180°C, a reaction time of 4 hours, a reaction pressure of 2 MPa, and a raw material space time of 1 g·min / ml. The raw material is fed into a fixed-bed reactor carrying 3 g of the catalyst to produce octenal by condensation reaction.

[0109] After the reaction stabilized, both the reactants and products were analyzed using online gas chromatography. The results are shown in Table 3.

[0110] Table 3

[0111]

[0112]

[0113] As can be seen from the table, the synthesized catalyst was used in the preparation of octenal, and the reaction showed high conversion and selectivity.

[0114] Application Example 2

[0115] Catalyst 1 prepared using the catalysts in Tables 1-2 # The reaction to prepare octenal by butyraldehyde 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.

[0116] Table 4

[0117]

[0118]

[0119] The table shows that reaction temperature and space-time have a significant impact on reaction conversion and selectivity.

[0120] 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 octenal by butyraldehyde condensation, characterized in that, Includes the following steps: In a reactor, a raw material containing butyraldehyde is introduced and reacted with a catalyst to obtain a product containing octenal. The space time of the raw material is 0.1 ~ 6 g·min / ml; The reaction temperature is 140~200℃; The catalyst comprises hollow Al2O3 and CoCr2O4; In the catalyst, the mass ratio of CoCr2O4 to hollow Al2O3 is 1:(10~20).

2. The method for preparing octenal by butyraldehyde condensation according to claim 1, characterized in that, The catalyst preparation method includes the following steps: (1) Mix raw materials containing cobalt source, chromium source, molten salt and ethanol, dry them, and calcine them to obtain CoCr2O4; (2) Mix the CoCr2O4 obtained in (1) with hollow Al2O3, and calcine it to obtain a catalyst for the condensation of butyraldehyde to octenal.

3. The method for preparing octenal by butyraldehyde condensation according to claim 2, characterized in that, In step (1), The cobalt source is at least one of cobalt nitrate, cobalt oxide, and cobalt hydroxide; The chromium source is at least one of chromium nitrate, chromium oxide, and chromium hydroxide; The molten salt is a mixture of KCl and at least one selected from NaCl and / or ZnCl2; The molar ratio of KCl to at least one of NaCl and / or ZnCl2 is (0.5~1):1; The molar ratio of the cobalt source to the chromium source is (0.9~1):2; calculated based on the cobalt or chromium element content in the cobalt or chromium source. The mass ratio of the cobalt source to the molten salt is 1:(1~2).

4. The method according to claim 2, characterized in that, In step (1), The mixing I includes ultrasonic and grinding mixing; The temperature of the drying process I is 80~110℃; The drying time for step I is 2-5 hours; The calcination temperature I is 600~1200℃; The calcination time is 4-8 hours.

5. The method according to claim 2, characterized in that, In step (2), The mass ratio of CoCr2O4 obtained in (1) to hollow Al2O3 is 1:(10~20). The calcination temperature III is 500~600℃; The calcination time for the third stage is 4-8 hours.

6. The method according to claim 2, characterized in that, In step (2), The hollow Al2O3 is obtained through the following process: The raw materials containing carbon spheres, aluminum nitrate, and ethanol are mixed (II), dried (II), and calcined (II) to obtain the hollow Al2O3; in, The ratio of carbon spheres, aluminum nitrate, and ethanol is 1g:(30~50)g:(200~300)ml; The temperature of the drying II process is 100~120℃; The drying time for step II is 6-12 hours; The calcination temperature II is 500~600℃; The calcination time II is 4~8 hours.

7. The method according to claim 6, characterized in that, The mixing method II is selected from mechanical mixing. After mixing II and before drying II, ultrasonication and settling were performed. The duration of the ultrasound is 10-60 minutes; The settling time is 4 to 10 hours.

8. The method according to claim 6, characterized in that, The mixing II method is selected from the wet mixing method; after mixing II and before drying II, ultrasonication and settling are performed; The duration of the ultrasound is 10–60 minutes; The settling time is 4 to 10 hours.

9. The method according to claim 1, characterized in that, The reactor used for the condensation of butyraldehyde to prepare octenal is a fixed-bed reactor.

10. The method according to claim 1, characterized in that, The reaction time for the condensation of butyraldehyde to prepare octenal is 3-5 hours. The pressure for the condensation of butyraldehyde to prepare octenal is 1-5 MPa.

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