A method for preparing octenal by self-condensation of n-butyraldehyde

Abstract

The present invention provides a method for preparing octenal through the self-condensation of n-butyraldehyde. A catalyst is placed in a fixed-bed reactor, and the n-butyraldehyde is pumped into the fixed-bed reactor through a feed pump. The catalyst includes a metal oxide and other additives, and the metal oxide includes MgO and CeO2. The reaction of preparing octenal through the self-condensation of n-butyraldehyde is carried out in a fixed-bed reactor. The conversion rate of n-butyraldehyde and the selectivity of octenal are both higher than 95%, and the catalyst has good stability in use and can maintain good catalytic activity after long-term use. When the catalyst catalyzes the synthesis of octenal, no alkaline wastewater is generated, and there is no need to separate the product and the catalyst. The process is simple, low-cost, and environmentally friendly, and can meet the requirements for industrialization of preparing octenal through the self-condensation of n-butyraldehyde.

Description

Technical Field

[0001] The invention belongs to the technical field of compound synthesis, and in particular relates to a method for preparing octenal through self-condensation of n-butyraldehyde. Background Art

[0002] Octanol (2-ethylhexanol, 2-EH), commonly referred to as octanol refers to isooctyl alcohol, which is mainly used to manufacture dioctyl phthalate (DOP / DEHP) and dioctyl terephthalate (DOTP). It is also used in diesel additives, synthetic lubricants, antioxidants, solvents and defoaming agents. It can also be used in paper sizing, photography, latex and printing and dyeing. It is an important basic organic chemical raw material and chemical auxiliary raw material.

[0003] Currently, the industrial preparation of octanol mainly involves three steps: (1) using propylene and synthesis gas as raw materials to produce n-butyraldehyde through carbonylation reaction;

[0004] (2) n-Butyraldehyde undergoes self-condensation reaction under the catalysis of base to generate octenal (2-ethyl-2-hexenal):

[0005] 2CH3CH2CH2CHO→CH3CH2CH2CH=C(CH2CH3)CHO+H2O

[0006] (3) Octenal is hydrogenated to produce octanol:

[0007] CH3CH2CH2CH=C(CH2CH3)CHO+H2→CH3CH2CH2CH2CH(CH2CH3)CH2OH

[0008] Among them, liquid inorganic base (mainly dilute NaOH solution) is used as a catalyst for the industrial catalytic self-condensation of n-butyraldehyde. Although a high n-butyraldehyde conversion rate and octenal yield can be achieved, the production process has many disadvantages, such as severe equipment corrosion, non-reusable catalysts, large discharge of alkaline wastewater, high production costs, and serious environmental pollution. It is difficult to meet the current green chemical industry requirements.

[0009] To overcome the shortcomings of traditional liquid inorganic base catalysts, the development of new, environmentally friendly base catalysts is of great significance. Solid bases are solids that can accept protons or donate electron pairs. Alkali metal or alkaline earth metal oxide catalysts are common solid base catalysts. Compared with traditional liquid inorganic base catalysts, solid base catalysts offer many advantages, including high catalytic activity, high selectivity, easy separation, and reusability. However, solid base catalysts are often sensitive to air and moisture, have poor stability, and have other limitations, such as low strength and low specific surface area, which limit their application in industry.

[0010] Patent CN102070419A describes a method for preparing octenal by the self-condensation of n-butyraldehyde catalyzed by magnesium oxide. This method involves preparing the magnesium oxide catalyst hydrothermally and then catalyzing the reaction in the presence of a solvent. This method requires a large amount of solvent, reaching 10-20 times the mass of the raw n-butyraldehyde. This not only increases production costs and reduces production efficiency, but also requires further separation of the product and solvent, increasing process complexity and cost. Therefore, this method is not suitable for industrial production.

[0011] Patent CN102093183A reports a method for preparing octenal using a series of supported solid base catalysts for the self-condensation of n-butyraldehyde. While these supported catalysts can achieve n-butyraldehyde conversion rates exceeding 90%, octenal selectivity is less than 70%, and the preparation process also requires a large amount of solvent, making it unsuitable for industrial production.

[0012] Patent CN113087605A uses activated alumina as a solid base catalyst to catalyze the self-condensation of n-butyraldehyde to produce octenal. The catalyst exhibits high initial catalytic activity, with both n-butyraldehyde conversion and octenal selectivity exceeding 90%. However, the catalyst exhibits poor lifespan stability. After five reuses, both n-butyraldehyde conversion and octenal selectivity were less than 90%, requiring reactivation for further use. Furthermore, the catalyst's harsh catalytic conditions, requiring a reaction pressure of 5 MPa, hinder its industrial application.

[0013] Therefore, there is still a need to develop a solid base catalyst with high activity, long life and industrial application value. Summary of the Invention

[0014] In view of this, the present invention aims to provide a method for preparing octenal by self-condensation of n-butyraldehyde, so as to solve the problems of poor catalyst life stability and harsh catalytic conditions of the catalyst.

[0015] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0016] A method for preparing octenal by self-condensation of n-butyraldehyde, comprising placing a catalyst in a fixed-bed reactor, and pumping n-butyraldehyde into the fixed-bed reactor through a feed pump;

[0017] The catalyst includes metal oxides and other additives, and the metal oxides include MgO and CeO2.

[0018] Furthermore, the reaction temperature is 90-140°C, the reaction pressure is 0.25-2.5 MPa, and the n-butyraldehyde feed space velocity is 0.1-5.0 h -1 .

[0019] Furthermore, the molar ratio of MgO to CeO2 in the catalyst is 1:0.5-1.5.

[0020] Furthermore, other adjuvants include magnesium fatty acid;

[0021] Preferably, the fatty acid magnesium comprises a saturated or unsaturated fatty acid of C4-C20 and Mg 2+ The organic magnesium salt is preferably composed of one or more of magnesium butyrate, magnesium octanoate, magnesium myristate, magnesium stearate and magnesium oleate.

[0022] Furthermore, the mass ratio of the metal oxide to the other additives is 1:0.05-0.15.

[0023] A method for preparing a catalyst in a method for preparing octenal by self-condensation of n-butyraldehyde comprises the following steps:

[0024] S1: adding magnesium salt and cerium salt to water and stirring to obtain a mixed solution;

[0025] S2: adding an excess amount of alkaline solution dropwise to the mixed solution in step S1 under stirring;

[0026] S3: The precipitate produced in step S2 is removed by filtration, washed thoroughly until neutral, and then dried to obtain a dried product;

[0027] S4: calcining the dried product in step S3 to obtain a calcined solid;

[0028] S5: uniformly mixing the calcined solid obtained in S4 with other additives, and forming the solid base catalyst.

[0029] Furthermore, the magnesium salt in step S1 is magnesium nitrate, and the cerium salt in step S1 is cerium nitrate;

[0030] The alkaline substance of the alkaline solution in step S2 includes one or more of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate, and potassium carbonate;

[0031] Preferably, the step S2 comprises uniformly adding an excess amount of alkaline solution to the mixed solution in S1, and aging the mixed solution for 6-24 hours after precipitation is complete.

[0032] Furthermore, step S3 includes filtering out the precipitate in step S2, washing it with water until it is neutral, and then drying it in an oven at a temperature of 100-120 degrees Celsius for 24 hours.

[0033] Furthermore, the step S4 includes drying the product and calcining it at 500-900° C. for 2-5 hours.

[0034] Furthermore, the metal oxide obtained in S4 is uniformly mixed with other additives in a certain proportion, and formed into tablets or strips by a method of extrusion to obtain the solid base catalyst;

[0035] Preferably, the solid base catalyst obtained in step S5 has a size of 10-20 mesh;

[0036] Preferably, the mass ratio of the metal oxide to other additives is 1:0.05-0.15.

[0037] Compared with the prior art, the method for preparing octenal by self-condensation of n-butyraldehyde described in the present invention has the following advantages:

[0038] The present invention discloses a method for preparing octenal through the self-condensation reaction of n-butyraldehyde. The method utilizes a highly active and stable solid base catalyst, achieving a high conversion rate of the raw material n-butyraldehyde and high selectivity for the product octenal during the reaction. Furthermore, the solid base catalyst is non-corrosive and generates no alkaline wastewater. The solid base catalyst can be loaded into a fixed-bed reactor, and the reaction materials can be directly collected after leaving the reactor, eliminating the need to separate the reaction materials from the catalyst. The method has a simple process flow, low cost, and is environmentally friendly, meeting the requirements for industrialized production of octenal through the self-condensation of n-butyraldehyde. DETAILED DESCRIPTION

[0039] The technical solutions of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods described, unless otherwise specified, are all conventional methods.

[0040] Example 1

[0041] Preparation of solid base catalyst:

[0042] S1: Magnesium nitrate and cerium nitrate were weighed in a molar ratio of 1:0.5, dissolved in deionized water, and mixed well to prepare a mixed solution;

[0043] S2: Slowly add 20% by mass of ammonia water to the mixed solution prepared in S1 under mechanical stirring until no new precipitation is produced, and age for 8 hours;

[0044] S3: The precipitate in S2 is removed by filtration, washed thoroughly with deionized water, and then dried in an oven to remove moisture;

[0045] S4: The dried product was calcined at 850° C. in air atmosphere for 2.5 h to obtain the main component of the solid base catalyst.

[0046] S5: The main component obtained in S5 is mixed evenly with magnesium butyrate (the addition amount is 10% of the mass of the main component), and the mixture is formed into tablets, crushed and sieved to obtain a 10-20 mesh solid base catalyst.

[0047] Solid base catalyst evaluation:

[0048] The prepared catalyst was placed in a fixed bed reactor, and n-butyraldehyde was pumped into the fixed bed reactor through a feed pump at a space velocity of 1 h -1 The reaction temperature was 130°C and the reaction pressure was 0.7 MPa. Samples were taken periodically during the reaction and the composition of the product was analyzed by gas chromatography. The catalyst evaluation results are shown in Table 1.

[0049] Example 2

[0050] Preparation of solid base catalyst:

[0051] S1: Magnesium nitrate and cerium nitrate were weighed in a molar ratio of 1:0.75, dissolved in deionized water, and mixed well to prepare a mixed solution;

[0052] S2: Slowly add 20% by mass of sodium carbonate to the mixed solution prepared in S1 under mechanical stirring until no new precipitation is generated, and age for 10 hours;

[0053] S3: The precipitate in S2 is removed by filtration, washed thoroughly with deionized water, and then dried in an oven to remove moisture;

[0054] S4: The dried product was calcined in air at 550° C. for 4.5 h to obtain the main component of the solid base catalyst.

[0055] S5: The main component obtained in S5 is mixed evenly with magnesium octoate (the addition amount is 10% of the mass of the main component), and the mixture is formed into tablets, crushed and sieved to obtain a solid base catalyst of 10-20 mesh.

[0056] Solid base catalyst evaluation:

[0057] The prepared catalyst was placed in a fixed bed reactor, and n-butyraldehyde was pumped into the fixed bed reactor through a feed pump at a space velocity of 1.5 h -1 The reaction temperature was 120°C and the reaction pressure was 1.5 MPa. Samples were taken periodically during the reaction and the composition of the product was analyzed by gas chromatography. The catalyst evaluation results are shown in Table 1.

[0058] Example 3

[0059] Preparation of solid base catalyst:

[0060] S1: Magnesium nitrate and cerium nitrate were weighed in a molar ratio of 1:1, dissolved in deionized water, and mixed well to prepare a mixed solution;

[0061] S2: Slowly add 20% by mass of sodium hydroxide to the mixed solution prepared in S1 under mechanical stirring until no new precipitation is generated, and age at room temperature for 12 hours;

[0062] S3: The precipitate in S2 is removed by filtration, washed thoroughly with deionized water, and then dried in an oven to remove moisture;

[0063] S4: The dried product is calcined at 800° C. in air atmosphere for 3 h to obtain the main component of the solid base catalyst.

[0064] S5: The main component obtained in S5 is mixed evenly with magnesium oleate (the addition amount is 10% of the mass of the main component), and the mixture is formed into tablets, crushed and sieved to obtain a 10-20 mesh solid base catalyst.

[0065] Solid base catalyst evaluation:

[0066] The prepared catalyst was placed in a fixed bed reactor, and n-butyraldehyde was pumped into the fixed bed reactor through a feed pump at a space velocity of 1.0 h -1 The reaction temperature was 110°C and the reaction pressure was 1.0 MPa. Samples were taken periodically during the reaction and the composition of the product was analyzed using a gas chromatograph. The catalyst evaluation results are shown in Table 1.

[0067] Example 4

[0068] Preparation of solid base catalyst:

[0069] S1: Magnesium nitrate and cerium nitrate were weighed in a molar ratio of 1:1.25, dissolved in deionized water, and mixed to obtain a mixed solution;

[0070] S2: Slowly add 20% by mass of potassium hydroxide to the mixed solution prepared in S1 under mechanical stirring until no new precipitation is generated, and age for 16 hours;

[0071] S3: The precipitate in S2 is removed by filtration, washed thoroughly with deionized water, and then dried in an oven to remove moisture;

[0072] S4: The dried product is calcined in air at 700° C. for 3.5 h to obtain the main component of the solid base catalyst.

[0073] S5: The main component obtained in S5 is mixed evenly with magnesium stearate (the addition amount is 10% of the mass of the main component), and the mixture is formed into tablets, crushed and sieved to obtain a solid base catalyst of 10-20 mesh.

[0074] Solid base catalyst evaluation:

[0075] The prepared catalyst was placed in a fixed bed reactor, and n-butyraldehyde was pumped into the fixed bed reactor through a feed pump at a space velocity of 0.6 h -1 The reaction temperature was 100°C and the reaction pressure was 0.9 MPa. Samples were taken periodically during the reaction and the composition of the product was analyzed using a gas chromatograph. The catalyst evaluation results are shown in Table 1.

[0076] Example 5

[0077] Preparation of solid base catalyst:

[0078] S1: Magnesium nitrate and cerium nitrate were weighed in a molar ratio of 1:1.5, dissolved in deionized water, and mixed well to prepare a mixed solution;

[0079] S2: Slowly add 20% by mass of potassium carbonate to the mixed solution prepared in S1 under mechanical stirring until no new precipitation is generated, and age for 14 hours;

[0080] S3: The precipitate in S2 is removed by filtration, washed thoroughly with deionized water, and then dried in an oven to remove moisture;

[0081] S4: The dried product is calcined at 600° C. in air atmosphere for 4 h to obtain the main component of the solid base catalyst.

[0082] S5: The main component obtained in S5 is mixed evenly with magnesium myristate (the addition amount is 10% of the mass of the main component), and the mixture is formed into tablets, crushed and sieved to obtain a 10-20 mesh solid base catalyst.

[0083] Solid base catalyst evaluation:

[0084] The prepared catalyst was placed in a fixed bed reactor, and n-butyraldehyde was pumped into the fixed bed reactor through a feed pump at a space velocity of 1.8 h -1 The reaction temperature was 140°C and the reaction pressure was 1.2 MPa. Samples were taken periodically during the reaction and the composition of the product was analyzed using a gas chromatograph. The catalyst evaluation results are shown in Table 1.

[0085] Example 6

[0086] Preparation of solid base catalyst:

[0087] S1: Magnesium nitrate and cerium nitrate were weighed in a molar ratio of 1:1, dissolved in deionized water, and mixed well to prepare a mixed solution;

[0088] S2: Slowly add 20% by mass of sodium hydroxide to the mixed solution prepared in S1 under mechanical stirring until no new precipitation is generated, and age for 20 hours;

[0089] S3: The precipitate in S2 is removed by filtration, washed thoroughly with deionized water, and then dried in an oven to remove moisture;

[0090] S4: The dried product is calcined at 800° C. in air atmosphere for 3 h to obtain the main component of the solid base catalyst.

[0091] S5: The main component obtained in S5 is mixed evenly with magnesium oleate (the addition amount is 5% of the mass of the main component), and the mixture is formed into tablets, crushed and sieved to obtain a solid base catalyst of 10-20 mesh.

[0092] Solid base catalyst evaluation:

[0093] The prepared catalyst was placed in a fixed bed reactor, and n-butyraldehyde was pumped into the fixed bed reactor through a feed pump at a space velocity of 1.0 h -1 The reaction temperature was 110°C and the reaction pressure was 1.0 MPa. Samples were taken periodically during the reaction and the composition of the product was analyzed using a gas chromatograph. The catalyst evaluation results are shown in Table 1.

[0094] Example 7

[0095] Preparation of solid base catalyst:

[0096] S1: Magnesium nitrate and cerium nitrate were weighed in a molar ratio of 1:1, dissolved in deionized water, and mixed well to prepare a mixed solution;

[0097] S2: Slowly add 20% by mass of sodium hydroxide to the mixed solution prepared in S1 under mechanical stirring until no new precipitation is generated, and age for 22 hours;

[0098] S3: The precipitate in S2 is removed by filtration, washed thoroughly with deionized water, and then dried in an oven to remove moisture;

[0099] S4: The dried product is calcined at 800° C. in air atmosphere for 3 h to obtain the main component of the solid base catalyst.

[0100] S5: The main component obtained in S5 is mixed evenly with magnesium oleate (the addition amount is 15% of the mass of the main component), and the mixture is formed into tablets, crushed and sieved to obtain a solid base catalyst of 10-20 mesh.

[0101] Solid base catalyst evaluation:

[0102] The prepared catalyst was placed in a fixed bed reactor, and n-butyraldehyde was pumped into the fixed bed reactor through a feed pump at a space velocity of 1.0 h -1 The reaction temperature was 110°C and the reaction pressure was 1.0 MPa. Samples were taken periodically during the reaction and the composition of the product was analyzed using a gas chromatograph. The catalyst evaluation results are shown in Table 1.

[0103] Comparative Example 1

[0104] No fatty acid magnesium was added during the catalyst preparation process, and the other conditions were the same as in Example 3.

[0105] Comparative Example 2

[0106] No magnesium nitrate was added during the catalyst preparation process, and the other conditions were the same as in Example 3.

[0107] Comparative Example 3

[0108] No cerium nitrate was added during the catalyst preparation process, and the other conditions were the same as in Example 3.

[0109] Table 1 Catalyst evaluation results in various examples and comparative examples

[0110]

[0111] From the above experimental results we can see that:

[0112] (1) By comparing Example 3 with Comparative Example 1, it can be seen that fatty acid magnesium was added during the preparation of the solid base catalyst in Example 3, while fatty acid magnesium was not added during the preparation of the solid base catalyst in Comparative Example 1. During long-term use, the long-term conversion rate and selectivity of the catalyst in Comparative Example 1 were significantly lower than those of the catalyst in Example 3.

[0113] (2) Comparison of Example 3 and Comparative Example 2 shows that the catalyst containing only CeO2 and fatty acid magnesium has almost no catalytic activity;

[0114] (3) By comparing Example 3 with Comparative Example 3, it can be seen that the solid base catalyst in Comparative Example 3 does not contain CeO2 components, and the initial and long-term conversion rates and selectivity of the catalyst in Comparative Example 3 are significantly lower than the conversion rates and selectivity of the catalyst in Example 3.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing octenal by self-condensation of n-butyraldehyde, characterized in that: The catalyst is placed in a fixed bed reactor, and n-butyraldehyde is pumped into the fixed bed reactor through a feed pump; The catalyst includes metal oxides and other additives, and the metal oxides include MgO and CeO2; Other adjuvants include one or more of magnesium butyrate, magnesium octanoate, magnesium myristate, magnesium stearate, and magnesium oleate.

2. The method for preparing octenal by self-condensation of n-butyraldehyde according to claim 1, wherein: The reaction temperature is 90-140℃, the reaction pressure is 0.25-2.5MPa, and the feed space velocity of n-butyraldehyde is 0.1-5.0h -1 .

3. The method for preparing octenal by self-condensation of n-butyraldehyde according to claim 1, wherein: The molar ratio of MgO to CeO2 in the catalyst is 1:0.5-1.

5.

4. The method for preparing octenal by self-condensation of n-butyraldehyde according to claim 1, wherein: The mass ratio of metal oxide to other additives is 1:0.05-0.

15.

5. A method for preparing a catalyst in a method for preparing octenal by self-condensation of n-butyraldehyde according to any one of claims 1 to 4, characterized in that: The steps include: S1: adding magnesium salt and cerium salt to water and stirring to obtain a mixed solution; S2: adding an excess amount of alkaline solution dropwise to the mixed solution in step S1 under stirring; S3: The precipitate produced in step S2 is removed by filtration, washed thoroughly until neutral, and then dried to obtain a dried product; S4: calcining the dried product in step S3 to obtain a calcined solid; S5: uniformly mixing the calcined solid obtained in S4 with other additives, and forming the solid base catalyst.

6. The method for preparing the catalyst according to claim 5, wherein: The magnesium salt in step S1 is magnesium nitrate, and the cerium salt in step S1 is cerium nitrate; The alkaline substance of the alkaline solution in step S2 includes one or more of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate, and potassium carbonate.

7. The method for preparing the catalyst according to claim 6, wherein: The step S2 comprises uniformly adding an excess amount of alkaline solution to the mixed solution in S1, and aging the mixed solution for 6-24 hours after precipitation is complete.

8. The method for preparing the catalyst according to claim 5, wherein: The step S3 comprises filtering out the precipitate in S2, washing it with water until it is neutral, and then drying it in an oven.

9. The method for preparing the catalyst according to claim 5, wherein: The step S4 includes calcining the dried product at 500-900° C. for 2-5 hours.

10. The method for preparing the catalyst according to claim 5, wherein: The metal oxide obtained in S4 is uniformly mixed with other additives, and the mixture is formed into tablets or strips by a method of extrusion to obtain the solid base catalyst.

11. The method for preparing the catalyst according to claim 10, characterized in that: The solid base catalyst obtained in step S5 has a size of 10-20 mesh.

12. The method for preparing the catalyst according to claim 10, characterized in that: The mass ratio of metal oxide to other additives is 1:0.05-0.15.

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