Process and system for preparing octanol from n-butyraldehyde

Abstract

The invention belongs to the technical field of chemical synthesis, and particularly relates to a process and a system for preparing octanol from n-butyraldehyde. The process comprises the following steps: (S1) introducing a first alkali liquor as a catalyst into an n-butyraldehyde raw material to carry out n-butyraldehyde condensation reaction to obtain a first mixed liquor containing octenal and unreacted n-butyraldehyde; (S2) supplementing second alkali liquor into the first mixed liquor to promote unreacted n-butyraldehyde in the first mixed liquor to perform condensation reaction so as to increase the content of octenal and obtain second mixed liquor; (S3) refining and separating the second mixed solution to obtain purified octenal; and (S4) carrying out catalytic hydrogenation reaction on the octenal obtained in the step (S3), and converting the octenal into octanol. The system comprises a front condensation reactor, a rear condensation reactor, a refining unit and a hydrogenation reactor. The process and the system for preparing octanol from n-butyraldehyde have the advantages of high butyraldehyde conversion rate, good octenol selectivity, low alkali liquor consumption, high hydrogenation catalysis efficiency, low catalysis cost and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and particularly relates to a process and system for preparing octanol from n-butyraldehyde. Background Art

[0002] The core of the process of producing octanol from n-butyraldehyde is to efficiently convert n-butyraldehyde into octanol through two steps of condensation and hydrogenation. As a key raw material for a variety of industrial products, the market demand for octanol continues to grow, but efficiency and cost control in the production process have become key factors restricting the development of the industry.

[0003] In the prior art, the process of preparing octanol from n-butyraldehyde mainly relies on the condensation reaction in a kettle reactor. However, this method has significant defects: first, the mass transfer effect of the reactor is poor, resulting in limited n-butyraldehyde conversion rate, a large amount of unreacted n-butyraldehyde residue, and increased complexity and cost of subsequent treatment; second, due to the unsatisfactory mixing effect of the materials in the reactor, the residence time of the reactants is long, which is easy to induce side reactions, reducing the selectivity of the target product octenal, while increasing energy consumption and material consumption.

[0004] In order to improve these problems, patent CN216024790 U proposed a micro-interface strengthening system, which increases the contact area between alkali solution and n-butyraldehyde through micro-droplet technology, thereby enhancing the reaction rate and conversion rate to a certain extent. However, although this method has brought positive effects, it still needs in-depth research and improvement in improving octenal selectivity, further reducing the amount of alkali catalyst, and optimizing the performance of hydrogenation catalysts.

[0005] In addition, the design of hydrogenation catalyst and its reactor is also a key factor affecting the production cost and quality of octanol. Patent CN 109988618 A and others proposed a flexible single-stage two-dose hydrocracking process, aiming to reduce catalyst costs and improve product quality by optimizing the operation strategy of hydrogenation catalyst and reactor. However, in practical applications, these technologies still face challenges such as catalyst deactivation and difficulty in accurately controlling reaction conditions, resulting in high overall production costs.

[0006] In summary, the main problems faced by the current process of producing octanol from n-butyraldehyde include: first, the conversion rate of n-butyraldehyde is low, which is limited by the mass transfer effect of the reactor, resulting in a large amount of unreacted n-butyraldehyde residue; second, the reactants stay in the reactor for a long time, which is easy to cause side reactions and reduce the selectivity of the target product octenal; third, the performance of the hydrogenation catalyst needs to be improved, and it gradually deactivates with the operation of the device, and the catalyst cost is relatively high. Summary of the invention

[0007] The purpose of the present invention is to solve the problems of low n-butyraldehyde conversion rate, low octenal selectivity and high hydrogenation catalytic cost mentioned in the background technology, thereby providing a process and system for preparing octanol from n-butyraldehyde.

[0008] In order to achieve the above object, the present invention provides a process for preparing octanol from n-butyraldehyde in a first aspect, comprising the following steps:

[0009] (S1) introducing alkali solution as a catalyst into the n-butyraldehyde raw material to carry out a n-butyraldehyde condensation reaction to obtain a first mixed solution containing octenal and unreacted n-butyraldehyde;

[0010] (S2) adding a second alkali solution to the first mixed solution to promote the condensation reaction of unreacted n-butyraldehyde therein to increase the content of octenal, thereby obtaining a second mixed solution;

[0011] (S3) refining and separating the second mixed solution to obtain purified octenal;

[0012] (S4) subjecting the octenal obtained in step (S3) to a catalytic hydrogenation reaction to convert the octenal into octanol.

[0013] A second aspect of the present invention provides a system for preparing octanol from n-butyraldehyde, comprising:

[0014] A front condensation reactor is used to receive the n-butyraldehyde raw material and introduce the first alkali solution as a catalyst to carry out a n-butyraldehyde condensation reaction to obtain a first mixed solution containing octenal and unreacted n-butyraldehyde;

[0015] The post-condensation reactor is connected to the pre-condensation reactor and is used to receive the first mixed solution and the added second alkali solution to promote the condensation reaction of the unreacted n-butyraldehyde therein to increase the content of octenal and obtain a second mixed solution;

[0016] A refining unit connected to the post-condensation reactor is used to purify and separate the second mixed liquid to obtain purified octenal;

[0017] The hydrogenation reactor is connected to the refining unit and is used to receive the purified octenal and perform a catalyst hydrogenation reaction to convert the octenal into octanol.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention divides the process of preparing octenal by condensing n-butyraldehyde into a pre-condensation reaction and a post-condensation reaction, and uses a low molar amount of base as a catalyst in the pre-condensation reaction to preferentially complete the condensation of most n-butyraldehyde, and then adds base in the post-condensation reaction to completely convert the remaining n-butyraldehyde, which can greatly reduce the residence time of each condensation reaction and reduce the occurrence of side reactions.

[0020] 2. In the process of preparing octenal by condensation of n-butyraldehyde, the present invention can flexibly adjust the amount of alkali solution, reaction temperature and residence time of the front condensation reaction and the rear condensation reaction, thereby improving the efficiency of the process of preparing octenal by n-butyraldehyde.

[0021] 3. In the process of preparing octanol by octenal hydrogenation catalysis, the present invention uses two hydrogenation reactors that can be switched to be connected in series or in parallel, and adjusts the operating state of the hydrogenation reactor according to the catalytic life stage of the hydrogenation catalyst, thereby improving the catalytic efficiency of the hydrogenation catalyst and reducing the cost of using the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention provides a schematic diagram of a process for preparing octanol from n-butyraldehyde. DETAILED DESCRIPTION

[0023] The present invention is further described below by means of specific embodiments. The embodiments of the present invention are only used as illustrations of the present invention and do not mean that the scope of the present invention is limited thereto.

[0024] In the present invention, the percentages or percentage contents involved are all mass percentages or mass percentage contents unless otherwise specified.

[0025] like Figure 1 As shown, the first aspect of the present invention provides a process for preparing octanol from n-butyraldehyde, comprising the following steps:

[0026] (S1) introducing a first alkali solution as a catalyst into the n-butyraldehyde raw material to carry out a n-butyraldehyde condensation reaction to obtain a first mixed solution containing octenal and unreacted n-butyraldehyde;

[0027] (S2) adding a second alkali solution to the first mixed solution to promote the condensation reaction of unreacted n-butyraldehyde therein to increase the content of octenal, thereby obtaining a second mixed solution;

[0028] (S3) refining and separating the second mixed solution to obtain purified octenal;

[0029] (S4) subjecting the octenal obtained in step (S3) to a catalytic hydrogenation reaction to convert the octenal into octanol.

[0030] In some embodiments, in step (S1), the first alkali solution is a conventional alkali solution in the art, such as one or more of sodium hydroxide, potassium hydroxide, trimethylamine and triethylamine.

[0031] In a preferred embodiment, the ratio of the molar amount of alkali in the first alkali solution to the molar amount of the n-butyraldehyde raw material is (0.001-0.01):1, preferably (0.002-0.005):1.

[0032] Furthermore, under the above-mentioned molar dosage ratio, the condensation reaction in step (S1) is conducive to completing the condensation of more than 70% of the n-butyraldehyde raw material, such as 70%-90%, for example 75%, 80% or 85%, while suppressing the side reaction of n-butyraldehyde polymerization, ultimately increasing the yield of octenal EPA.

[0033] In some embodiments, in step (S1), the reaction temperature of the condensation reaction is 60-150°C, preferably 80-100°C;

[0034] The residence time of the condensation reaction is 5-65 min, preferably 10-20 min.

[0035] In some embodiments, in step (S2), the second alkali solution is a conventional alkali solution in the art, such as sodium hydroxide, potassium hydroxide, trimethylamine and triethylamine; wherein the first alkali solution and the second alkali solution may be the same or different.

[0036] The present invention has no special requirements on the mass fractions of the first alkali solution and the second alkali solution. They can be alkali solutions with higher mass fractions or lower mass fractions. It is only necessary to ensure that the ratio of the molar amount of alkali in the alkali solution to the molar amount of the n-butyraldehyde raw material in step (S1) and step (S2) meets the requirements.

[0037] In a preferred embodiment, after adding the second alkali solution, the ratio of the molar amount of alkali in the total alkali solution (i.e. the sum of the amounts of the first alkali solution and the second alkali solution) to the molar amount of the n-butyraldehyde raw material is (0.004-0.016):1, preferably (0.008-0.01):1.

[0038] In some embodiments, in step (S2), the reaction temperature of the condensation reaction is 80-200°C, preferably 100-140°C;

[0039] Furthermore, the residence time of the condensation reaction is 2-30 min, preferably 5-10 min.

[0040] In the present invention, through the two-step condensation reaction, the conversion rate of the n-butyraldehyde raw material can be above 99.5% (such as above 99.9%), the selectivity is above 98%, and the total amount of alcohol and ketone substances in the second mixed liquid is less than 150ppm.

[0041] In step (S3), the refining separation is used to remove water, reaction by-products (such as sodium butyrate, etc.) and alkaline catalyst in the second mixed liquor to purify the obtained octenal product, so as to facilitate the subsequent hydrogenation and light component removal of the second mixed liquor; wherein, through the refining separation, part of the alkali liquor separated from the second mixed liquor can also be recycled, for example, after simple treatment, they can be used as the first alkali liquor and / or the second alkali liquor to catalyze n-butyraldehyde.

[0042] In step (S3), the purification and separation method can be selected from at least one of chromatography, extraction, distillation and membrane separation, preferably one or two of chromatography and membrane separation. The specific separation is well known in the art and will not be described here.

[0043] In some embodiments, in step (S3), the water content of the purified octenal is below 5 wt%, such as 0.1-5 wt%, for example 2-3 wt%.

[0044] In some embodiments, in step (S4), the conditions of the catalytic hydrogenation reaction are known in the art, for example, may be as follows:

[0045] The temperature is 120-200°C;

[0046] The pressure is 0.3-0.6MPa;

[0047] Time is 0.5-20min;

[0048] Airspeed is 0.1-1h -1 .

[0049] The catalyst used can be a hydrogenation catalyst commonly used in the art for catalyzing the hydrogenation of octenal to produce octanol, and its active site can be at least one of copper, nickel and cobalt series, which are specifically well known in the art, such as NCH6-1 type and NCH6-2 type.

[0050] In step (S4), the chromaticity of the obtained octanol can be 10-100, preferably 10-50. After simple purification, the chromaticity index within 10 can be met.

[0051] It is known to those skilled in the art that chromaticity is a quality indicator of octanol. The lower the chromaticity, the better the downstream application.

[0052] In some embodiments, in step (S4), the catalytic hydrogenation is carried out in two hydrogenation reactors (which may be tubular fixed bed reactors) that are switchably connected in series and in parallel, wherein:

[0053] At the beginning of the life of the hydrogenation catalyst (i.e. when the raw materials are fed from top to bottom, the height of the hot spot temperature zone is less than 30% of the reactor bed height), the two hydrogenation reactors are switched to parallel operation;

[0054] In the middle of the life of the hydrogenation catalyst (i.e., the height of the hot spot temperature zone is 30-60% of the reactor bed height), the two hydrogenation reactors are switched to series operation;

[0055] At the end of the life of the hydrogenation catalyst (i.e., the height of the hot spot temperature zone is higher than 60% of the reactor bed height), one of the two hydrogenation reactors is kept in operation, and the other is cut out to replace a new catalyst;

[0056] Those skilled in the art will understand that the catalytic hydrogenation of n-butyraldehyde is an exothermic reaction. As the reaction proceeds, the catalyst bed of the tubular fixed bed reactor will heat up. At this time, the (catalyst) area with the highest temperature is the hotspot temperature zone of the reactor, and the height of the hotspot temperature zone is a key parameter for controlling the reaction conditions and ensuring the stability of the catalyst performance.

[0057] In the present invention, step (S4) can be flexibly scheduled according to the processing capacity and downstream customer indicators to avoid losses caused by stopping the machine to change the agent.

[0058] A second aspect of the present invention provides a system for preparing octanol from n-butyraldehyde, the system comprising:

[0059] A front condensation reactor is used to receive the n-butyraldehyde raw material and introduce the first alkali solution as a catalyst to carry out a n-butyraldehyde condensation reaction to obtain a first mixed solution containing octenal and unreacted n-butyraldehyde;

[0060] The post-condensation reactor is connected to the pre-condensation reactor and is used to receive the first mixed solution and the added second alkali solution to promote the condensation reaction of the unreacted n-butyraldehyde therein to increase the content of octenal and obtain a second mixed solution;

[0061] A refining unit connected to the post-condensation reactor is used to purify and separate the second mixed liquid to obtain purified octenal;

[0062] The hydrogenation reactor is connected to the refining unit and is used to receive the purified octenal and perform a catalyst hydrogenation reaction to convert the octenal into octanol.

[0063] In some embodiments, the hydrogenation reactor includes two hydrogenation reactors that can be switched to be connected in series or in parallel. The specific connection of the two hydrogenation reactors can be seen in Figure 1 , as follows:

[0064] At the beginning of the catalyst life, hydrogenation reactors A and B are in a parallel connection state. At this time, the two reactors share a common feed main pipe, that is, the raw materials enter reactors A and B at the same time; the discharge ports of the two reactors also share a common discharge main pipe, that is, the discharges of reactors A and B are combined and output together to form a second mixed liquid containing octenal.

[0065] In the middle of the catalyst life, hydrogenation reactors A and B are switched to a series connection state. At this time, the discharge port of reactor A is directly connected to the feed port of reactor B, that is, the material processed by reactor A directly enters reactor B for further processing; only the discharge port of reactor B outputs the second mixed liquid containing octenal to the outside.

[0066] At the end of the catalyst life, hydrogenation reactors A and B are again connected in parallel, where one of the reactors (assumed to be reactor A) remains in operation while the other (reactor B) is cut out to replace a new catalyst; once reactor B has replaced the catalyst and restarted, both reactors are in operation and connected in parallel again until the catalyst needs to be replaced again.

[0067] This design allows the reactor's operating mode to be flexibly adjusted according to the performance and life of the catalyst to maintain production efficiency and product quality.

[0068] In the present invention, the percentages or percentage contents involved are all mass percentages or mass percentage contents unless otherwise specified.

[0069] The present invention will be described in detail below through specific embodiments.

[0070] Example 1

[0071] (S1) In a 300 mL pre-condensation reactor A, under the conditions of a temperature of 80° C., a residence time of 10 min, and a liquid level of 80%, a condensation reaction of the n-butyraldehyde raw material is carried out in the presence of a NaOH solution (aqueous solution with a mass fraction of 0.12%) to obtain a first mixed solution containing octenal and unreacted n-butyraldehyde; wherein,

[0072] The dosage of the n-butyraldehyde raw material is 10.4 g / min, and the dosage of the NaOH solution is 9.63 g / min. After calculation, the ratio of the molar dosage of NaOH in the NaOH solution to the molar dosage of the n-butyraldehyde raw material is 0.002:1;

[0073] The temperature of the pre-condensation reactor A is 80°C.

[0074] (S2) transferring the first mixed solution into a 300 mL post-condensation reactor B, and adding the above-mentioned NaOH solution thereto, and carrying out a condensation reaction of the unreacted n-butyraldehyde under the conditions of a temperature of 100° C., a residence time of 5 min, and a liquid level of 82%, to obtain a second mixed solution; wherein,

[0075] The amount of the additional NaOH solution is 76.54 g / min, that is, the total amount of the NaOH solution is 9.63+76.54=86.17 g / min. After calculation, the ratio of the molar amount of NaOH in the total NaOH solution to the molar amount of n-butyraldehyde is 0.018:1;

[0076] The temperature of the post-condensation reactor B was 100°C.

[0077] (S3) In a distillation device for crude EPA, the second mixed liquid is purified and separated under the conditions of a temperature of 45° C., a pressure of 0.6 MPa, and a residence time of 10 min to obtain purified octenal (with a water content of 2%).

[0078] (S4) In two flexible and switchable series-parallel fixed-bed reactors, at a temperature of 175°C, a pressure of 0.55 MPa, and a space velocity of 0.4 h -1 Under the conditions of , the purified octenal is continuously subjected to catalytic hydrogenation reaction (the catalyst is commercially available NCH6-1 type) to obtain octanol.

[0079] Example 2

[0080] Refer to Example 1, the only difference is:

[0081] In step (S1),

[0082] The dosage of n-butyraldehyde is 4.16 g / min. After calculation, the ratio of the molar dosage of NaOH to the molar dosage of n-butyraldehyde in the NaOH solution is 0.005:1;

[0083] The temperature of the pre-condensation reactor A is 100°C.

[0084] In step (S2),

[0085] The amount of the added NaOH solution is 9.63 g / min, that is, the total amount of the NaOH solution is 9.63+9.63=19.26 g / min. After calculation, the ratio of the molar amount of NaOH in the total NaOH solution to the molar amount of n-butyraldehyde is 0.01:1.

[0086] The temperature of the post-condensation reactor B was 120°C.

[0087] Example 3

[0088] Refer to Example 1, the only difference is:

[0089] In step (S1),

[0090] The dosage of the n-butyraldehyde is 0.54 g / min, and the dosage of the NaOH solution is 2.52 g / min. After calculation, the ratio of the molar dosage of NaOH in the NaOH solution to the molar dosage of n-butyraldehyde is 0.01:1;

[0091] The temperature of the pre-condensation reactor A is 120°C.

[0092] In step (S2),

[0093] The amount of the added NaOH solution is 1.51 g / min, that is, the total amount of NaOH solution is 2.52+1.51=4.03 g / min. After calculation, the ratio of the molar amount of NaOH in the total alkali solution to the molar amount of n-butyraldehyde is 0.016:1.

[0094] The temperature of the post-condensation reactor B was 160°C.

[0095] Comparative Example 1

[0096] Refer to Example 3, the only difference is:

[0097] In step (S1), the dosage of the n-butyraldehyde raw material is 5.2 g / min, and the dosage of the NaOH solution is 28.85 g / min. After calculation, the ratio of the molar dosage of NaOH in the NaOH solution to the molar dosage of the n-butyraldehyde raw material is 0.012:1.

[0098] In step (S2),

[0099] The amount of the additional NaOH solution is 9.63 g / min, that is, the total amount of the NaOH solution is 28.85+9.63=38.48 g / min, that is, the ratio of the molar amount of NaOH in the NaOH solution to the molar amount of n-butyraldehyde is 0.016:1, which is the same as in Example 3.

[0100] Comparative Example 2

[0101] Refer to Example 2, the only difference is:

[0102] In step (S2),

[0103] The amount of the added NaOH solution is 25.04 g / min, that is, the total amount of the NaOH solution is 9.63+25.04=34.67 g / min. After calculation, the ratio of the molar amount of NaOH in the total NaOH solution to the molar amount of n-butyraldehyde is 0.018:1.

[0104] Comparative Example 3

[0105] Refer to Example 1, the only difference is:

[0106] In step (S1), the residence time is 15 min.

[0107] The dosage of the NaOH solution is 86.17 g / min. After calculation, the ratio of the molar dosage of NaOH in the NaOH solution to the molar dosage of the n-butyraldehyde raw material is 0.018:1.

[0108] Without performing step (S2), the first mixed solution obtained in step (S1) is directly subjected to purification and separation in step S3 to obtain purified octenal.

[0109] The products of reactor A and reactor B in the above example were analyzed by gas chromatography, and the n-butyraldehyde conversion rate and EPA selectivity in reactor A and reactor B were calculated respectively. The results are shown in Table 1

[0110] Table 1:

[0111]

[0112] Among them, the A conversion rate is the conversion rate of the n-butyraldehyde raw material in the front condensation reactor A, the B conversion rate is the conversion rate of the n-butyraldehyde raw material in the rear condensation reactor B, and the total conversion rate is the total conversion rate of the n-butyraldehyde raw material after passing through the front condensation reactor A and the rear condensation reactor B;

[0113] A selectivity is the selectivity of the n-butyraldehyde raw material to EPA in the front condensation reactor A, B selectivity is the selectivity of the n-butyraldehyde raw material to EPA in the rear condensation reactor B, and the total selectivity is the total selectivity of the n-butyraldehyde raw material to EPA after passing through the front condensation reactor A and the rear condensation reactor B.

[0114] From the comparison between Example 3 and Comparative Example 1, it can be seen that only increasing the molar amount of the base in the pre-condensation reaction will increase the conversion rate of the pre-condensation reaction and slightly increase the total conversion rate, but will significantly reduce the selectivity and total selectivity of the pre-condensation reaction.

[0115] From the comparison between Example 2 and Comparative Example 2, it can be seen that only increasing the molar amount of the base in the post-condensation reaction will slightly increase the conversion rate and the total conversion rate of the post-condensation reaction, but the selectivity of the unreacted butyraldehyde in the post-condensation reaction is reduced, and the total selectivity is also reduced.

[0116] From the comparison between Example 1 and Comparative Example 3, it can be seen that when the total alkali dosage is maintained consistent with the residence time, only the post-condensation reaction system is cancelled. At this time, the total conversion rate of n-butyraldehyde is significantly reduced, and the product selectivity is not optimal, which will lead to the need to process the unreacted butyraldehyde in industrial production, resulting in additional costs.

[0117] In summary, the present invention divides the process of preparing octenal by condensation of n-butyraldehyde into a front condensation reaction and a rear condensation reaction, and uses a low molar amount of alkali as a catalyst in the front condensation reaction to preferentially complete the condensation of most n-butyraldehyde, and then adds alkali in the rear condensation reaction to completely convert the remaining n-butyraldehyde, which can greatly reduce the residence time of each condensation reaction, reduce the occurrence of side reactions, and maintain a high n-butyraldehyde conversion rate. Relative to the molar amount of n-butyraldehyde, increasing the molar amount of alkali can appropriately increase the total conversion rate of n-butyraldehyde, but it will reduce the total selectivity of EPA.

Claims

1. A process for preparing octanol from n-butyraldehyde, characterized in that: The process comprises the following steps: (S1) introducing a first alkali solution as a catalyst into the n-butyraldehyde raw material to carry out a n-butyraldehyde condensation reaction to obtain a first mixed solution containing octenal and unreacted n-butyraldehyde; (S2) adding a second alkali solution to the first mixed solution to promote a condensation reaction of unreacted n-butyraldehyde therein to increase the content of octenal, thereby obtaining a second mixed solution; (S3) refining and separating the second mixed solution to obtain purified octenal; (S4) subjecting the octenal obtained in step (S3) to a catalytic hydrogenation reaction to convert the octenal into octanol.

2. The process according to claim 1, characterized in that In step (S1), The first alkali solution is at least one of sodium hydroxide, potassium hydroxide, trimethylamine and triethylamine; The ratio of the molar amount of the alkali in the first alkali solution to the molar amount of the n-butyraldehyde raw material is (0.001-0.01):1, preferably (0.002-0.005):

1.

3. The process according to claim 1 or 2, characterized in that In step (S1), the reaction temperature of the condensation reaction is 60-150°C, preferably 80-100°C; The residence time of the condensation reaction is 5-65 min, preferably 10-20 min.

4. The process according to any one of claims 1 to 3, characterized in that In step (S2), the second alkali solution is at least one of sodium hydroxide, potassium hydroxide, trimethylamine and triethylamine; After the second alkali solution is added, when the condensation reaction is carried out, the ratio of the molar amount of alkali in the total alkali solution to the molar amount of the n-butyraldehyde raw material is (0.004-0.016):1, preferably (0.008-0.01):

1.

5. The process according to any one of claims 1 to 4, characterized in that In step (S2), The reaction temperature of the condensation reaction is 80-200°C, preferably 100-140°C; The residence time of the condensation reaction is 2-30 min, preferably 5-10 min.

6. The process according to any one of claims 1 to 5, characterized in that In step (S3), The purification and separation method is selected from at least one of chromatography, extraction, distillation and membrane separation, preferably one or two of chromatography and membrane separation; Preferably, after refining and separation, the water content of the purified octenal obtained is 0.1-5wt%, preferably 2-3wt%.

7. The process according to any one of claims 1 to 6, characterized in that In step (S4), The conditions of the catalytic hydrogenation reaction include: The temperature is 120-200°C; The pressure is 0.3-0.6MPa; Time is 0.5-20min; Airspeed is 0.1-1h -1 ; The active site of the catalyst is at least one of copper, nickel and cobalt.

8. The process according to any one of claims 1 to 7, characterized in that In step (S4), the catalytic hydrogenation reaction is carried out in two hydrogenation reactors that can be switched in series and in parallel; wherein, At the beginning of the life of the hydrogenation catalyst, the two hydrogenation reactors are switched to parallel operation; In the middle of the life of the hydrogenation catalyst, the two hydrogenation reactors are switched to operate in series; At the end of the life of the hydrogenation catalyst, one of the two hydrogenation reactors is kept in operation, and the other is switched out to be replaced with a new catalyst.

9. A system for preparing octanol from n-butyraldehyde, characterized in that: The system comprises: A front condensation reactor is used to receive the n-butyraldehyde raw material and introduce the first alkali solution as a catalyst to carry out a n-butyraldehyde condensation reaction to obtain a first mixed solution containing octenal and unreacted n-butyraldehyde; The post-condensation reactor is connected to the pre-condensation reactor and is used to receive the first mixed solution and the added second alkali solution to promote the condensation reaction of the unreacted n-butyraldehyde therein to increase the content of octenal and obtain a second mixed solution; A refining unit connected to the post-condensation reactor is used to purify and separate the second mixed liquid to obtain purified octenal; The hydrogenation reactor is connected to the refining unit and is used to receive the purified octenal and perform a catalyst hydrogenation reaction to convert the octenal into octanol.

10. The system for producing octanol from n-butyraldehyde according to claim 9, characterized in that: The hydrogenation reactor includes two hydrogenation reactors that can be switched to be connected in series or in parallel.

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