A reactor and apparatus for the production of acids from aldehyde oxidation

Abstract

The utility model discloses an aldehyde oxidation preparation acid's reactor and device. The device includes oxidation reactor and oxidation fractionating column, the upper portion of oxidation reactor casing is provided with liquid distributor, and the lower portion is arranged with gas distributor, and the outside of oxidation reactor is provided with oxidation reaction circulating pump and oxidation reaction circulating heat abstractor, and the acid-containing liquid phase product export of oxidation reactor is connected with oxidation reaction circulating pump import, and the export of oxidation reaction circulating pump is connected with oxidation reaction circulating heat abstractor import and oxidation fractionating column import respectively, and the export of oxidation reaction circulating heat abstractor is connected with oxidation reactor feed inlet, and the top of oxidation fractionating column is equipped with incondensable gas export, and the bottom is equipped with heavy component export, and the upper portion is equipped with light component export and product acid export from top to bottom in proper order. The utility model can realize the uniform dispersion and sufficient contact of gas-liquid two-phase material, significantly improve mass transfer efficiency and reaction rate, and ensure high conversion rate of aldehyde raw material and high selectivity of carboxylic acid product.

Description

Technical Field

[0001] This utility model relates to the chemical industry, and in particular to a reactor and apparatus for the oxidation of aldehyde compounds to prepare acids. Background Technology

[0002] With the continuous development of modern organic synthesis industry, carboxylic acid compounds, as important basic chemical raw materials and intermediates, including medium and short chain fatty acids such as acetic acid, propionic acid, butyric acid, isobutyric acid and hexanoic acid, are not only important components of solvents, plasticizers and resin monomers, but also play a key role in the synthesis of pharmaceutical intermediates and agrochemicals, and the market demand continues to grow.

[0003] Among existing methods for preparing carboxylic acids, aldehyde oxidation is considered a mature, feasible, and industrially viable technology. This process uses aldehyde compounds as raw materials, selectively oxidizing them with oxygen or air to directly generate the corresponding carboxylic acid products. For example, the oxidation of n-butyraldehyde to butyric acid and isobutyraldehyde to isobutyric acid have become the mainstream industrial production methods for these products. Compared with traditional carboxylic acid synthesis methods, aldehyde oxidation has advantages such as a wide availability and low cost of raw materials, mild reaction conditions, relatively simple operation, and fewer byproducts, making it particularly suitable for the large-scale production of medium- and short-chain fatty acids.

[0004] From a technological perspective, aldehyde oxidation mainly includes two types: gas-phase oxidation and liquid-phase oxidation. Gas-phase oxidation is usually carried out at high temperatures, resulting in a faster reaction rate, but it also involves more side reactions, poor selectivity, and requires equipment with high heat and corrosion resistance. Liquid-phase oxidation, on the other hand, is carried out at lower temperatures, offering relatively better selectivity and easier control, making it the more common industrial route. To further improve conversion and selectivity, some processes employ metal salts or supported catalysts to regulate the reaction mechanism and product distribution. However, catalytic oxidation processes also have many problems, such as high catalyst costs, susceptibility to deactivation, and the need for frequent replacements, leading to increased operating costs; furthermore, catalyst recovery and waste disposal impose additional environmental pressures.

[0005] In recent years, some enterprises and research institutions have explored liquid-phase air oxidation processes under catalyst-free conditions. Through process intensification and equipment improvements, they have achieved stable production with lower investment and operating costs. These processes offer advantages such as simplified procedures and reduced costs, but they also expose new challenges: aldehydes are highly reactive, prone to polymerization and coking, and the oxidation process is a strongly exothermic reaction, posing risks of explosive polymerization and runaway. How to effectively control the release of reaction heat and achieve efficient oxygen utilization while ensuring safety has become the core challenge in reactor design.

[0006] Traditional reaction equipment, such as batch reactors, bubble columns, stirred tanks, and some fixed-bed reactors, generally have the following shortcomings when applied to aldehyde oxidation reactions:

[0007] (1) The gas-liquid phase contact efficiency is low and the oxygen mass transfer rate is insufficient, resulting in low oxygen utilization and limited aldehyde conversion rate.

[0008] (2) The temperature control method is limited, and local overheating is likely to occur during the reaction process, which will increase the side reactions and even trigger the risk of polymerization and explosive polymerization;

[0009] (3) Uneven distribution of material residence time leads to poor reaction selectivity and large fluctuations in product quality;

[0010] (4) Some equipment has a complex structure, which increases manufacturing and maintenance costs and is not conducive to large-scale continuous operation;

[0011] (5) Insufficient heat dissipation and mass transfer capacity limits the scale-up and high-load operation of the device. Utility Model Content

[0012] The purpose of this invention is to provide a reactor and apparatus for aldehyde oxidation to produce acid, addressing the shortcomings of existing equipment in terms of heat transfer, mass transfer, and safety. Through structural optimization, this invention not only achieves efficient conversion of aldehyde raw materials and highly selective preparation of the target product, but also extends the operating cycle of the apparatus, reduces downtime losses, and improves overall economic efficiency.

[0013] To achieve the above objectives, the technical solution of this utility model is as follows:

[0014] A reactor for the oxidation of aldehydes to produce acids is characterized in that: the reactor is an oxidation reactor, with a feed inlet at the top, an oxidation reaction tail gas outlet at the top, an air / oxygen inlet at the bottom, and an acid-containing liquid phase product outlet at the bottom; a liquid distributor is provided in the upper part of the reactor shell, with the feed inlet connected to the liquid distributor; a gas distributor is arranged in the lower part of the reactor shell, with the air / oxygen inlet connected to the gas distributor; the gas distributor consists of a gas distribution pipe and a gas injection pipe; the liquid distributor mainly consists of a liquid distribution plate, a liquid injection pipe, and a liquid distribution pipe; the liquid injection pipe is installed above the liquid distribution plate, and the liquid distribution pipe is correspondingly connected below the liquid distribution plate.

[0015] Preferably, the gas distribution pipe has an overall annular structure, and the gas injection pipe includes a main injection pipe that passes through the center of the gas distribution pipe, and four short pipes that extend radially outward from the center. The four short pipes are arranged in a cross-shaped orthogonal manner and are all connected to the gas distribution pipe.

[0016] Preferably, the surface of the gas distribution pipe is uniformly provided with a plurality of small holes, the shape of which is round, rectangular, rhomboid or square.

[0017] Preferably, the liquid distribution plate has a plurality of circular holes evenly distributed on it, the diameter of which is 5 to 35 mm, and the liquid distribution pipe is connected to the bottom of the circular holes of the liquid distribution plate.

[0018] Preferably, the liquid distribution pipe is arranged perpendicularly to the liquid distribution plate, and a plurality of openings are evenly provided on the side wall of the liquid distribution pipe, the total area of ​​the openings being controlled to be 2 to 6 times the area of ​​the circular holes of the liquid distribution plate.

[0019] This utility model also provides an apparatus for preparing acid by aldehyde oxidation, which includes an oxidation reactor and an oxidation fractionation tower. The oxidation reactor is as described above. An oxidation reaction circulation pump and an oxidation reaction circulation heat exchanger are installed externally on the oxidation reactor. The outlet of the acid-containing liquid product of the oxidation reactor is connected to the inlet of the oxidation reaction circulation pump. The outlet of the oxidation reaction circulation pump is connected to the inlet of the oxidation reaction circulation heat exchanger and the inlet of the oxidation fractionation tower, respectively. The outlet of the oxidation reaction circulation heat exchanger is connected to the feed inlet of the oxidation reactor. The oxidation fractionation tower has a non-condensable gas outlet at the top, a heavy component outlet at the bottom, and a light component outlet and a product acid outlet in sequence from top to bottom at the top.

[0020] Preferably, the oxidation reactor is provided as one unit or multiple units connected in series.

[0021] Preferably, the oxidation reaction cycle heat exchanger is a water cooler or an air cooler.

[0022] This invention relates to a continuous process for the oxidation of aliphatic aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, and isobutyraldehyde with oxygen or air to produce the corresponding carboxylic acid products. This technology is widely used in industries such as fine chemicals, solvent manufacturing, pharmaceutical intermediates, and fragrances.

[0023] The advantages of this utility model compared with the prior art are as follows:

[0024] This invention achieves uniform dispersion and full contact of gas-liquid two-phase materials by incorporating a liquid distributor and a gas distributor inside the oxidation reactor, significantly improving mass transfer efficiency and reaction rate, thereby ensuring high conversion rates of aldehyde raw materials and high selectivity of acid products. Simultaneously, the matching of an external circulating pump and a circulating heat exchanger allows for the timely removal of the large amount of reaction heat generated by the reaction system, effectively preventing local overheating that could exacerbate side reactions or deactivate the catalyst, ensuring the safety and stability of the reaction process. Compared with traditional single cooling methods, this circulating heat exchange mode is more flexible and efficient, adaptable to the strongly exothermic aldehyde oxidation reaction. Furthermore, the rational configuration of the oxidation fractionation tower allows for the graded discharge of light components, main products, and byproducts, improving the purity of the target product and facilitating the collection and treatment of byproducts, ensuring continuous and stable operation of the device. This invention features a compact overall structure, a wide operating range, and can maintain high conversion rates (≥90%) and yields at industrial scale, demonstrating good economic benefits and significant application value.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of the present invention. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an apparatus for preparing acid by aldehyde oxidation according to the present invention;

[0027] Figure 2 This is a top view of a gas distributor in a reactor for the oxidation of aldehydes to produce acids according to this utility model;

[0028] Figure 3 This is a front view of the gas distributor in a reactor for the oxidation of aldehydes to produce acids according to this utility model.

[0029] Figure 4 This is a schematic diagram of the gas distribution pipe in a reactor for the oxidation of aldehydes to prepare acids according to this utility model;

[0030] Figure 5 This is a schematic diagram of the liquid distribution plate in a reactor for the preparation of acid by aldehyde oxidation according to the present invention;

[0031] Figure 6 This is a front view of a liquid distributor in a reactor for the preparation of acid by aldehyde oxidation according to this utility model;

[0032] Figure 7 This is a front view of the liquid distribution plate in a reactor for the preparation of acid by aldehyde oxidation according to this invention.

[0033] The reference numerals in the figure are:

[0034] 1. Oxidation reactor; 2. Oxidation reaction circulating pump; 3. Oxidation reactor circulating heat exchanger; 4. Oxidation fractionation tower; 5. Liquid distributor; 6. Gas distributor; 7. Gas distribution pipe; 8. Gas injection pipe; 9. Liquid distribution plate; 10. Liquid injection pipe; 11. Liquid distribution pipe. Detailed Implementation

[0035] The present invention will now be further described with reference to the accompanying drawings.

[0036] like Figure 1-7 As shown, this utility model discloses a reactor and apparatus for the preparation of acid by aldehyde oxidation.

[0037] like Figure 1 As shown, this utility model discloses an apparatus for preparing acid by aldehyde oxidation, which includes an oxidation reactor 1 and an oxidation fractionation tower 4. The oxidation reactor 1 has a feed inlet at the top, an oxidation reaction tail gas outlet at the top, an air / oxygen inlet at the bottom, and an acid-containing liquid product outlet at the bottom. The acid-containing liquid product outlet of the oxidation reactor 1 is connected to the inlet of the oxidation reaction circulation pump 2. The outlet of the oxidation reaction circulation pump 2 is connected to the inlet of the oxidation reaction circulation heat exchanger 3 and the inlet of the oxidation fractionation tower 4, respectively. The outlet of the oxidation reaction circulation heat exchanger 3 is connected to the feed inlet of the oxidation reactor 1. The oxidation fractionation tower 4 has a non-condensable gas outlet at the top, a heavy component outlet at the bottom, and a light component outlet and a product acid outlet in sequence from top to bottom at the top.

[0038] An oxidation reaction circulation pump 2 and an oxidation reaction circulation heat exchanger 3 are installed outside the oxidation reactor 1. The outlet of the acid-containing liquid product of the oxidation reactor 1 is connected to the inlet of the oxidation reaction circulation pump 2. The outlet of the oxidation reaction circulation pump 2 is connected to the inlet of the oxidation reaction circulation heat exchanger 3 and the inlet of the oxidation fractionation tower 4. The outlet of the oxidation reaction circulation heat exchanger 3 is connected to the feed inlet of the oxidation fractionation tower 4. The oxidation fractionation tower 4 has a non-condensable gas outlet at the top, a heavy component outlet at the bottom, and a light component outlet and a product acid outlet in sequence from top to bottom at the top.

[0039] The oxidation reactor 1, together with the oxidation reaction circulation pump 2 and the oxidation reaction circulation heat exchanger 3, constitute a complete circulation and heat exchange system.

[0040] A liquid distributor 5 is provided in the upper part of the shell of the oxidation reactor 1. The feed inlet of the oxidation reactor 1 is connected to the liquid distributor 5. The liquid distributor 5 is used to uniformly distribute and introduce the liquid material entering the reactor. A gas distributor 6 is arranged in the lower part of the shell of the oxidation reactor 1. The air / oxygen inlet is connected to the gas distributor 6. The gas distributor 6 is used to uniformly disperse air / oxygen in the liquid phase.

[0041] This invention, through its corresponding liquid and gas distribution devices, ensures sufficient contact and a highly uniform distribution of the gas and liquid phases during the reaction process. This effectively avoids problems such as excessively high local concentrations, incomplete reactions, or aggravated side reactions caused by uneven fluid distribution. This combination of top-down liquid distribution and bottom-up gas distribution creates an ideal countercurrent contact mode, significantly improving mass transfer efficiency and reaction selectivity, while also ensuring the stability and controllability of the device during continuous operation.

[0042] As shown in Figure 2-4, the gas distributor 6 consists of a gas distribution pipe 7 and a gas injection pipe 8, featuring a compact structure and reasonable arrangement. The gas distribution pipe 7 has an overall annular structure, forming an annular distribution channel along the inner wall of the lower shell of the reactor. The gas injection pipe 8 includes a main injection pipe penetrating the center of the gas distribution pipe 7, and four short pipes extending radially outward from the center. These four short pipes are arranged in a cross-shaped orthogonal arrangement, meaning that the four short pipes extend radially from the center of the gas distribution pipe 7 and are arranged in a cross-shaped orthogonal arrangement, with all four short pipes connected to the gas distribution pipe 7. This gas distributor 6 not only ensures that the gas is fully and evenly distributed before entering the reaction zone of the oxidation reactor, but also, through the combination of the annular and cross-shaped structure, allows the gas to diffuse from the center outwards and then be evenly released along the annular ring, effectively eliminating the problem of excessively high local gas concentrations. This gas distributor structure enhances the uniformity and permeability of the gas in the reaction zone, ensuring that the oxidant can fully contact the liquid aldehyde material, thereby improving the reaction rate and selectivity.

[0043] The surface of the gas distribution pipe 7 is uniformly perforated with multiple small holes, serving as the main outlet for gas release. These holes can be designed in various forms, such as round, rectangular, diamond, or square holes, to accommodate different gas flow rates and dispersion requirements. The diverse design of hole diameter and shape allows gas to enter the liquid-phase reaction zone uniformly in the form of microbubbles, significantly increasing the contact area between the gas and liquid phases and enhancing mass transfer and mixing. Uniform perforations not only effectively prevent liquid disturbance caused by concentrated gas ejection but also avoid a decrease in reaction efficiency due to uneven gas flow rates. Through reasonable optimization of hole diameter distribution, shape, and density, this gas distribution device can achieve high gas utilization and excellent reaction performance while maintaining stable system operation, making it particularly suitable for strongly exothermic aldehyde oxidation reactions.

[0044] like Figure 5-7As shown, the liquid distributor 5 mainly consists of key components such as a liquid distribution plate 9, a liquid injection pipe 10, and a liquid distribution pipe 11. The liquid injection pipe 10 is installed above the liquid distribution plate (9) and serves as the main channel for liquid materials to enter the distributor. The liquid distribution plate 9 has several evenly spaced circular holes, whose size and distribution are strictly designed to ensure that the liquid can fall evenly into the lower liquid distribution pipe 11. The liquid distribution pipe 11 is connected one-to-one with the circular holes of the distribution plate, and is located below the circular holes of the liquid distribution plate 9, further guiding the liquid into the reaction space of the reactor. To ensure suitable flow rate and droplet formation, the diameter of the circular holes in the liquid distribution plate 9 is typically between 5 and 35 mm. Within this range, sufficient liquid flow is ensured while avoiding excessively large droplets that could reduce mass transfer efficiency. This structural design allows for good pre-dispersion of the liquid before it enters the reaction zone, significantly improving the gas-liquid contact area and reaction rate.

[0045] The liquid distribution pipe 11 is arranged perpendicularly to the liquid distribution plate 9, allowing the liquid to flow evenly from top to bottom into the reaction zone primarily due to gravity, preventing liquid deviation or accumulation inside the shell. The side wall of the liquid distribution pipe 11 has several evenly distributed openings to enhance the lateral spraying and dispersion effect of the liquid. The total area of ​​these openings is controlled to be 2 to 6 times the area of ​​the circular holes in the liquid distribution plate 9. This ratio balances liquid flow rate and dispersion effect, enabling the liquid to form finer droplets or streams, promoting full gas-liquid contact and mixing. Through this multi-stage distribution and multi-directional spraying design, the liquid forms a uniform liquid film or droplet cluster within the reactor, improving the uniformity of material residence in the reaction zone and avoiding incomplete reactions and excessively high local concentrations, thus achieving a highly efficient and stable reaction process.

[0046] In the operation of the apparatus for aldehyde oxidation to acid, a large amount of circulating liquid is first pressurized by the oxidation reactor circulation pump 2, then enters the oxidation reaction circulation heat exchanger 3 for effective heat exchange, and subsequently flows back into the oxidation reactor 1 through the feed inlet. Through this circulation process, the exothermic reaction generated in the reaction system can be removed in a timely manner, thereby avoiding excessively high local temperatures that could lead to aggravated side reactions or catalyst deactivation. Simultaneously, the stable and efficient circulating heat exchange method of this invention ensures the uniformity of the temperature field inside the reactor, keeping the reaction within a controllable and ideal operating range. Therefore, the apparatus for aldehyde oxidation to acid of this invention not only improves the safety and stability of system operation but also optimizes reaction selectivity and raw material conversion rate. Compared with traditional single cooling methods, the circulating heat exchange scheme of this device is more flexible and efficient, especially suitable for strongly exothermic aldehyde oxidation reactions, ensuring continuous and large-scale industrial application of the process, and providing strong support for improving product quality and reducing energy consumption.

[0047] The oxidation reaction cycle heat exchanger 3 mentioned above can be a water cooler or an air cooler.

[0048] The simple operation process of the apparatus for preparing acid by aldehyde oxidation according to this utility model is as follows:

[0049] Aldehyde raw materials are mixed with external circulating liquid and fed into the oxidation reactor 1 through the feed inlet into the liquid distributor 5. Air / oxygen enters the gas distributor 6 through the air / oxygen inlet from the lower part of the oxidation reactor 1. The feed material, which is uniformly distributed by the liquid distributor 5, and the air / oxygen, which is uniformly distributed by the gas distributor 6, react in opposite directions in the reactor reaction zone. The aldehyde is oxidized into acid, generating an acid-containing liquid phase product.

[0050] The acid-containing liquid product in the oxidation reactor 1 exits through the acid-containing liquid product outlet of the oxidation reactor 1, is pressurized by the oxidation reaction circulation pump 2, and then part of it is sent to the oxidation fractionation tower 4 for fractionation as a liquid product, while the other part is heated by the oxidation reaction circulation heat exchanger 3 and then returned to the oxidation reactor 1. The oxidation reaction tail gas in the oxidation reactor 1 is discharged from the top of the oxidation reactor 1.

[0051] After fractionation, the acid-containing liquid product entering the oxidation fractionation tower 4 is discharged from the device separately or mixed with the oxidation reaction tail gas discharged from the top of the oxidation reactor 1. The light oxidation components in the oxidation fractionation tower 4 are extracted from the top or upper part of the tower. The acid product after rectification is extracted from the upper part of the oxidation fractionation tower 4, and the heavy components are discharged from the bottom of the oxidation fractionation tower 4.

[0052] The oxidation reactor 1 typically operates at a temperature between 30 and 200°C and a pressure range of 0.2 to 4.0 MPaG. Under preferred conditions, the temperature is controlled between 40 and 100°C, and the pressure is maintained between 0.5 and 2.0 MPaG. Because aldehydes with different carbon numbers exhibit differences in physical properties, reactivity, and volatility, this reactor can operate independently as a single unit or be flexibly combined in series to meet different process requirements and production scales. During operation, the gas-liquid contact inside the reactor is enhanced, and the heat of reaction is promptly removed through a high-efficiency heat exchange system, preventing localized overheating and effectively suppressing side reactions. Through precise temperature and pressure control and a reasonable process layout, the overall conversion rate of aldehyde raw materials can be guaranteed to reach over 90%, with high yield and low impurity content of the target carboxylic acid product.

[0053] The oxidation fractionation tower 4, as a crucial separation unit of this apparatus, primarily functions to efficiently separate and purify the liquid products discharged from the oxidation reactor 1. The oxidized liquid products first enter the oxidation fractionation tower 4, where effective separation of components with different boiling points is achieved through rectification and fractionation. During the separation process, the non-condensable gases and some oxidation tail gases generated during the reaction rise along with the lighter components and are eventually extracted from the top or upper part of the tower. This portion of gas is then mixed with the oxidation tail gas and discharged outside the apparatus or further treated, thus avoiding pressure buildup and cross-contamination within the apparatus. The light oxidized components extracted from the top or upper part of the tower mainly include incompletely converted low-molecular-weight aldehydes, low-boiling-point byproducts, and a small amount of dissolved gases. These light components can be recycled or centrally processed according to process requirements. The middle section of the tower is the main product outlet, where the target carboxylic acid, after rectification, is extracted at a higher purity and discharged as a qualified product to an external storage tank or subsequent refining unit. By optimizing the tray structure or packing design, the product yield and purity in the middle of the column are significantly improved, effectively ensuring the stability and economy of downstream applications. Furthermore, some heavy components or byproducts with high boiling points are inevitably generated during the oxidation reaction. These substances are difficult to be carried out in the upper or middle part of the column, and therefore eventually concentrate at the bottom and are continuously discharged in liquid form. The heavy components discharged from the bottom can be collected separately, reducing contamination of the target product and facilitating the subsequent resource utilization or harmless treatment of byproducts. Through this top-down staged separation method, the oxidative distillation column 4 not only achieves efficient separation of light, heavy, and main products, but also ensures continuous and stable operation of the entire unit, improves product quality and yield, and effectively controls byproduct emissions.

[0054] The above are merely typical embodiments of this utility model. Those skilled in the art can make appropriate modifications and improvements based on them, but those that are substantially the same as this utility model also fall within the protection scope of this utility model.

Claims

1. A reactor for the oxidation of aldehydes to prepare acids, characterized in that: The reactor for aldehyde oxidation to prepare acid is an oxidation reactor (1). The oxidation reactor (1) has a feed inlet at the top, an oxidation reaction tail gas outlet at the top, an air / oxygen inlet at the bottom, and an acid-containing liquid product outlet at the bottom. A liquid distributor (5) is installed in the upper part of the shell of the oxidation reactor (1). The feed inlet of the oxidation reactor (1) is connected to the liquid distributor (5). A gas distributor (6) is arranged in the lower part of the shell of the oxidation reactor (1). The air / oxygen inlet is connected to the gas distributor (6). The gas distributor (6) consists of a gas distribution pipe (7) and a gas injection pipe (8). The liquid distributor (5) mainly consists of a liquid distribution plate (9), a liquid injection pipe (10), and a liquid distribution pipe (11). The liquid injection pipe (10) is installed above the liquid distribution plate (9), and the liquid distribution pipe (11) is connected to the liquid distribution plate (9) below.

2. The reactor for the preparation of acid by aldehyde oxidation according to claim 1, characterized in that: The gas distribution pipe (7) has an overall ring structure. The gas injection pipe (8) includes a main injection pipe that runs through the center of the gas distribution pipe (7) and four short pipes that extend radially outward from the center. The four short pipes are arranged in a cross-shaped orthogonal manner and are all connected to the gas distribution pipe (7).

3. The reactor for aldehyde oxidation to prepare acid according to claim 2, characterized in that: The surface of the gas distribution pipe (7) is uniformly provided with a plurality of small holes, the shape of which is round, rectangular, rhomboid or square.

4. The reactor for aldehyde oxidation to prepare acid according to claim 1, characterized in that: The liquid distribution plate (9) is provided with several circular holes with a diameter of 5 to 35 mm. The liquid distribution pipe (11) is connected to the bottom of the circular holes of the liquid distribution plate (9).

5. The reactor for aldehyde oxidation to prepare acid according to claim 4, characterized in that: The liquid distribution pipe (11) is arranged perpendicularly to the liquid distribution plate (9). Several openings are evenly provided on the side wall of the liquid distribution pipe (11), and the total area of ​​the openings is controlled to be 2 to 6 times the area of ​​the circular hole of the liquid distribution plate (9).

6. An apparatus for preparing an acid by aldehyde oxidation, characterized in that: The apparatus for oxidizing aldehydes to produce acids includes an oxidation reactor (1) and an oxidation fractionation tower (4). The oxidation reactor (1) is as described in any one of claims 1-5. An oxidation reaction circulation pump (2) and an oxidation reaction circulation heat exchanger (3) are provided outside the oxidation reactor (1). The outlet of the acid-containing liquid product of the oxidation reactor (1) is connected to the inlet of the oxidation reaction circulation pump (2). The outlet of the oxidation reaction circulation pump (2) is connected to the inlet of the oxidation reaction circulation heat exchanger (3) and the inlet of the oxidation fractionation tower (4), respectively. The outlet of the oxidation reaction circulation heat exchanger (3) is connected to the feed inlet of the oxidation reactor (1). The oxidation fractionation tower (4) is provided with a non-condensable gas outlet at the top, a heavy component outlet at the bottom, and a light component outlet and a product acid outlet in sequence from top to bottom at the top.

7. The apparatus for preparing acid by aldehyde oxidation according to claim 6, characterized in that: The oxidation reactor (1) may be a single unit or multiple units connected in series.

8. The apparatus for preparing acid by aldehyde oxidation according to claim 6, characterized in that: The oxidation reaction cycle heat exchanger (3) is a water cooler or an air cooler.

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