Preparation method of catalyst for synthesizing isooctylamine by continuous reduction and amination of isooctyl aldehyde and application thereof

Abstract

The application discloses a preparation method of a catalyst for synthesizing isooctylamine through continuous reduction and amination of isooctyl aldehyde and application thereof. The non-noble metal cobalt-based catalyst is prepared by adopting a precipitation deposition method. The anchoring effect of hydroxyl groups and alkaline groups on the surface of the additives MgO and Al2O3 on the active metal precursor effectively inhibits the formation of metal clusters, so that the active metal is highly uniformly distributed. The preparation process is simple and easy to be industrialized and enlarged, and the catalyst can be applied to a process for synthesizing isooctylamine through reduction and amination of isooctyl aldehyde as raw material, so that the batch stability and conversion rate can be improved.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a catalyst preparation method for the continuous reduction amination of isooctaldehyde to synthesize isooctylamine and its application. Background Technology

[0002] Isooctylamine (2-ethylhexylamine) and its derivatives are important fine chemical intermediates, widely used in surfactants, pesticide synergists, pharmaceuticals, dyes, metal extractants, and rubber additives. With the continuous expansion of downstream application markets, developing efficient, low-cost, and simple isooctylamine synthesis processes has remained a research hotspot in this field.

[0003] Currently, the main process routes for synthesizing isooctylamine are divided into two aspects: One is to use n-butyraldehyde as a starting material, generating the unsaturated intermediate octenal through aldol condensation, followed by reductive amination to synthesize isooctylamine. For example, the one-pot process disclosed in Chinese invention patent CN114105780B uses nickel or copper as a skeletal catalyst to catalyze the aldol condensation and reductive amination of n-butyraldehyde to obtain isooctylamine. Although this simplifies the separation process, it faces significant challenges in heat removal and batch stability due to the gradient temperature control requirements of the condensation stage and the two-stage atmosphere switching operation. The second approach uses isooctyl alcohol as a raw material, directly reacting it with ammonia (or amine) under high-pressure hydrogen conditions through a catalytic dehydration amination reaction. For example, Chinese invention patent CN1250517C discloses a reduction amination process using isooctyl alcohol as raw material and Cu-Co / Al2O3-diatomaceous earth catalyst. The catalyst shows good stability and selectivity of over 95% during 240 hours of continuous operation. However, this route is a hydrogen-borrowing reaction between alcohol and amine, which requires overcoming the high activation energy barrier of carbon-oxygen bond breaking and subsequent imine hydrogenation, resulting in a limited single-pass conversion rate (<71%), which increases process energy consumption and operating costs. Summary of the Invention

[0004] To address at least one of the aforementioned technical deficiencies, the present invention provides the following technical solution: This application discloses a method for preparing a catalyst for the continuous reducing amination of isooctaldehyde to synthesize isooctylamine, comprising the following steps: Step 1: Cobalt salt, magnesium oxide, and aluminum oxide are mixed in water at a molar ratio of 0.8-1.2:2.5-3.2:2.5-3.2 to form a first aqueous solution. Sodium carbonate and sodium hydroxide are dissolved in water to form a second aqueous solution. The first and second aqueous solutions are mixed, aged, and then separated into solid and liquid components and dried to obtain the metal precursor. Step 2: The metal precursor obtained in Step 1 is calcined and ground to obtain the desired catalyst.

[0005] Furthermore, the cobalt salt is any one or a combination of multiple of cobalt sulfate heptahydrate, cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt carbonate.

[0006] Furthermore, in step one, the molar ratio of sodium carbonate to cobalt salt is 0.3-0.6:1; the molar ratio of sodium hydroxide to cobalt salt is 1.0-2.0:1.

[0007] Furthermore, in step one, after mixing the first aqueous solution and the second aqueous solution, the mixture is stirred for 10-60 minutes, and the aging time is 6-12 hours.

[0008] Furthermore, in step two, the roasting temperature is 400-600℃ and the time is 4-12h.

[0009] This application discloses the application of the catalyst prepared by the above preparation method in the synthesis of isooctylamine.

[0010] Furthermore, the following steps are included: Step 1: Mix isooctaldehyde in methanol with ammonia in methanol to obtain the raw material solution; Step 2: Prepare isooctylamine by hydrogenation amination reaction at a temperature of 30-130℃ and a pressure of 0.5-1MPa.

[0011] Furthermore, in step one, the mass ratio of isooctaldehyde to methanol is 4:15-350.

[0012] Furthermore, in step two, the catalyst is loaded into the fixed-bed reactor, the feed liquid obtained in step one is input into the fixed-bed reactor, and hydrogen is transported to the fixed-bed reactor.

[0013] Furthermore, the feed rate of the raw material liquid is 0.2-0.4 ml / min, and the hydrogen flow rate is 10-20 ml / min.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention directly synthesizes isooctaldehyde from isooctaldehyde via reductive amination, avoiding the intermediate step of butyraldehyde aldol condensation in existing one-pot methods. It eliminates the need for atmosphere switching and gradient temperature control, thus removing the side reaction risks and operational complexity associated with this step from the outset. Furthermore, the reductive amination of the aldehyde C=O bond does not require the high activation energy barrier step of C–O bond breaking found in alcohol routes, resulting in milder reaction conditions and significantly improved process controllability.

[0015] 2. Based on the synthetic route of isooctaldehyde-isooctylamine, a catalyst was designed and prepared by precipitation deposition method. The hydroxyl and basic groups on the surface of the promoters MgO and Al2O3 effectively inhibited the formation of metal clusters by anchoring the active metal precursor, resulting in a highly uniform distribution of the active metal. This can reduce reaction conditions and risks during the synthesis of isooctylamine.

[0016] 3. This invention employs a fixed-bed continuous reaction process, which is simple to operate and stable in operation. Under the action of the aforementioned cobalt-based catalyst, it exhibits high conversion rate (100%) and high selectivity (97%) in the isooctaldehyde reduction amination reaction to isooctylamine. The catalyst can operate stably for a long period of 1776 hours, showing good prospects for industrial application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a picture of the catalyst.

[0019] Figure 2 This is a TEM image of the catalyst.

[0020] Figure 3 This is a picture of the finished product, isooctylamine.

[0021] Figure 4 It is a reaction flow chart. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] 1. The method for preparing catalysts by precipitation deposition is as follows: Example 1 A method for preparing a catalyst for the continuous reducing amination of isooctaldehyde to synthesize isooctylamine includes the following steps: Step 1: Mix cobalt sulfate heptahydrate, magnesium oxide, and aluminum oxide in a molar ratio of 1:3:3 in water with a total mass of 20 times that of the three to form the first aqueous solution.

[0024] Sodium carbonate and sodium hydroxide are dissolved in water in a volume 20 times their total mass to form a second aqueous solution, wherein the molar ratios of sodium carbonate, sodium hydroxide and cobalt nitrate are 0.4:1 and 1.5:1, respectively.

[0025] The first aqueous solution was added dropwise to the second aqueous solution, stirred for 60 min, and then aged for 10 h. After aging, the solution was filtered and washed to separate the solid and liquid components. The resulting solid component was then dried to obtain the metal precursor.

[0026] Step 2: The metal precursor obtained in Step 1 is placed in a muffle furnace and calcined at a heating rate of 5℃ / min to 500℃ for 5 hours. After natural cooling to room temperature, it is ground, granulated using a tablet press, and screened into 20-40 mesh particles, which is the desired catalyst. Figure 1 As shown, its TEM image is as follows Figure 2 As shown.

[0027] Example 2 Compared to Example 1, cobalt chloride is used instead of cobalt sulfate heptahydrate in this example.

[0028] Example 3 Compared to Example 1, cobalt nitrate is used instead of cobalt sulfate heptahydrate in this example.

[0029] Example 4 Compared to Example 1, cobalt acetate is used instead of cobalt sulfate heptahydrate in this example.

[0030] Example 5 Compared to Example 1, cobalt carbonate is used instead of cobalt sulfate heptahydrate in this example.

[0031] The catalysts prepared above were tested by ICP-OES, and the results are shown in Table 1. The actual loading is close to the theoretical value with a small deviation (where the theoretical loading of cobalt is calculated as M). Co / (M Co +M 载体 )×100%, M Co and M 载体 (These represent the mass of the cobalt precursor and the carrier, respectively).

[0032] 2. The preparation steps of isooctylamine are as follows: Synthesis example 1 A method for synthesizing isooctaldehyde by continuous reducing amination includes the following steps: Step 1: Mix isooctaldehyde in methanol with ammonia in methanol to obtain the raw material solution.

[0033] The methanol solution of isooctaldehyde is prepared as follows: the mass ratio of isooctaldehyde to methanol is 4:250, and the ammonia methanol solution (CAS: 7664-41-7) is added in an amount that is 5 times the molar amount of isooctaldehyde, based on ammonia.

[0034] Step 2: Prepare isooctylamine by hydrogenation amination reaction at 100℃ and 1MPa.

[0035] First, 5g of the catalyst prepared in Example 1 was loaded into a fixed-bed reactor, and the catalyst bed was washed with 200mL of methanol. The reaction feed liquid was continuously fed into the fixed-bed reactor via a constant-pressure horizontal flow pump for hydrogenation amination to synthesize isooctylamine. The reaction temperature was controlled at 100℃, the pressure at 1MPa, the feed liquid flow rate at 0.2mL / min, and the hydrogen flow rate at 20mL / min (hydrogen purity ≥99.999%). The finished isooctylamine product was as follows: Figure 3 As shown, the reaction process is as follows Figure 4 As shown.

[0036] Synthesis example 2 The difference from Synthesis Example 1 is that the catalyst in this example was prepared in Example 2.

[0037] Synthesis example 3 The difference from Synthesis Example 1 is that the catalyst in this example was prepared in Example 3.

[0038] Synthesis example 4 The difference from Synthesis Example 1 is that the catalyst in this example was prepared in Example 4.

[0039] Synthesis example 5 The difference from Synthesis Example 1 is that the catalyst in this example was prepared in Example 5.

[0040] The reaction products prepared in the above synthesis example were analyzed by gas chromatography, and the results are shown in Table 1. Chromatographic conditions: HP-5 capillary column (50m × 0.32mm × 0.52μm) and flame ionization detector (FID).

[0041] Table 1

[0042] ; .

[0043] As shown in Table 1, the performance is most significant when the cobalt salt is cobalt nitrate.

[0044] The following describes the preparation of Synthetic Examples 6-11. The difference between Synthetic Example 3 and Synthetic Example 6 is the temperature, as detailed in Table 2.

[0045] Table 2

[0046] The following describes the preparation of Synthetic Examples 12-16. The difference between Synthetic Example 3 and Synthetic Example 3 is the different ammonia equivalents, as detailed in Table 3.

[0047] Table 3

[0048] The following are the preparations of Comparative Examples 1-4. Compared with Synthesis Example 3, the difference lies in the support of the catalyst. In Comparative Example 1, magnesium oxide was used instead of the composite support of magnesium oxide and aluminum oxide in the catalyst preparation. In Comparative Example 2, aluminum oxide was used instead of the composite support of magnesium oxide and aluminum oxide in the catalyst preparation. In Comparative Example 3, silica was used instead of the composite support of magnesium oxide and aluminum oxide in the catalyst preparation. In Comparative Example 4, silica was used instead of magnesium oxide in the catalyst preparation. The detection results of the prepared isooctylamine samples are shown in Table 4.

[0049] Table 4

[0050] The following is the preparation of Comparative Example 5. Compared with Synthetic Example 3, the difference is that the aging process was omitted during catalyst preparation. The detection of the prepared isooctylamine sample is shown in Table 5.

[0051] Table 5

[0052] The aged catalysts exhibit superior catalytic activity and selectivity.

[0053] The following is the preparation of Comparative Example 6. Compared with Synthetic Example 3, the difference is that butyraldehyde was used instead of isooctaldehyde. The detection of the prepared isooctylamine sample is shown in Table 6.

[0054] Table 6

[0055] The following are the stability tests under the process conditions. The catalyst prepared in Example 3 was continuously used in a fixed bed for the time shown in Table 7, and the test results are shown in Table 7.

[0056] Table 7

[0057] It can be seen that this catalyst has excellent stability and has certain industrialization prospects in the synthesis of isooctylamine.

[0058] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for the continuous reducing amination of isooctaldehyde to synthesize isooctylamine, characterized in that, Includes the following steps: Step 1: Cobalt salt, magnesium oxide, and aluminum oxide are mixed in water at a molar ratio of 0.8-1.2:2.5-3.2:2.5-3.2 to form a first aqueous solution. Sodium carbonate and sodium hydroxide are dissolved in water to form a second aqueous solution. The first and second aqueous solutions are mixed, aged, and then separated into solid and liquid components and dried to obtain the metal precursor. Step 2: Calcine and grind the metal precursor obtained in Step 1 to obtain the desired catalyst; The cobalt salt is any one or a combination of cobalt sulfate heptahydrate, cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt carbonate; In step one, the molar ratio of sodium carbonate to cobalt salt is 0.3-0.6:1; the molar ratio of sodium hydroxide to cobalt salt is 1.0-2.0:

1. In step one, after mixing the first aqueous solution and the second aqueous solution, stir for 10-60 minutes, and the aging time is 6-12 hours; In step two, the roasting temperature is 400-600℃ and the time is 4-12h.

2. The application of the catalyst prepared by the method of claim 1 in the synthesis of isooctylamine.

3. The application as described in claim 2, characterized in that: Includes the following steps: Step 1: Mix isooctaldehyde in methanol with ammonia in methanol to obtain the raw material solution; Step 2: Prepare isooctylamine by hydrogenation amination reaction at a temperature of 30-130℃ and a pressure of 0.5-1MPa.

4. The application as described in claim 3, characterized in that: In step one, the mass ratio of isooctaldehyde to methanol is 4:15-350.

5. The application as described in claim 3, characterized in that: In step two, the catalyst is loaded into the fixed-bed reactor, the feed liquid obtained in step one is fed into the fixed-bed reactor, and hydrogen is transported to the fixed-bed reactor.

6. The application as described in claim 5, characterized in that: The feed rate of the raw material liquid is 0.2-0.4 L / min, and the hydrogen flow rate is 10-20 ml / min.

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