Process for the preparation of acids by oxidation of aldehydes and use thereof

Abstract

The present application relates to the field of catalytic oxidation, and discloses a method for preparing acid by aldehyde oxidation and application. The method for preparing acid by aldehyde oxidation comprises mixing a catalyst, a solvent, aldehyde and an oxidant for reaction, wherein the catalyst is selected from at least one of alpha-hydroxy carboxylic acid, alpha-hydroxy carboxylic acid salt, beta-hydroxy carboxylic acid, beta-hydroxy carboxylic acid salt, gamma-hydroxy carboxylic acid and gamma-hydroxy carboxylic acid salt. The scheme provided by the present application can improve the selectivity of the aldehyde oxidation reaction for preparing acid and the yield of organic acid, reduce the generation of by-products, and improve the product quality. In addition, the method for preparing acid by aldehyde oxidation provided by the present application has a simple process and is conducive to industrialization.

Description

Technical Field

[0001] This invention relates to the field of catalytic oxidation, and more specifically, to a method and application for the oxidation of aldehydes to prepare acids. Background Technology

[0002] Aldehyde oxidation to produce acids, as an important acid production route, has been studied for many years. For example, the oxidation of acetaldehyde to produce acetic acid has become a mature industrial technology with a large production capacity.

[0003] Isooctanoic acid, also known as 2-ethylhexanoic acid, is a colorless and transparent liquid at room temperature. It is a widely used fine chemical with applications in industries such as coatings, plastics, pharmaceuticals, cosmetics, and food. Isooctanoic acid is a downstream product of the propylene carbonyl synthesis to butanol and octanol process, mainly produced via the n-butyraldehyde route and the isooctanoic acid oxidation route. The n-butyraldehyde oxidation route offers advantages such as better atom economy, lower energy consumption, less waste generation, and lower production costs.

[0004] It is generally believed that aldehyde oxidation of acid is a free radical mechanism involving the Baeyer-Villiger rearrangement. During the rearrangement process, the rearrangement of α-H atoms can yield the target product isooctanoic acid, while the rearrangement of alkyl groups yields byproducts. Therefore, it is necessary to design an efficient catalyst system to reduce alkyl transfer and increase the α-H migration rate, thereby improving the yield of the target product. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a method and application for the preparation of acids by aldehyde oxidation.

[0006] To achieve the above objectives, the present invention provides a method for preparing an acid by aldehyde oxidation, wherein a catalyst, a solvent, an aldehyde, and an oxidant are mixed and reacted, wherein the catalyst is selected from at least one compound with the structure shown in Formula 1.

[0007]

[0008] In Formula 1, R is an alkyl group with 1-30 carbon atoms, M is at least one of H, alkali metal, alkaline earth metal, manganese, iron, cobalt, copper and zinc, and x is 0, 1 or 2.

[0009] A second aspect of the present invention provides the use of the compound of Formula 1 in improving the feed conversion rate and / or the selectivity of the target product in the preparation of acids from aldehyde oxidation.

[0010] The above technical solutions improve the selectivity of aldehyde oxidation to acid production and the yield of organic acids while reducing the formation of by-products and enhancing product quality. Furthermore, the aldehyde oxidation to acid production method provided by this invention has a simple process, which is conducive to industrialization. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] This invention provides a method for preparing an acid by oxidizing an aldehyde, comprising mixing a catalyst, a solvent, an aldehyde, and an oxidant to carry out the reaction, wherein the catalyst is selected from at least one compound with the structure shown in Formula 1.

[0013]

[0014] In Formula 1, R is an alkyl group with 1-30 carbon atoms, M is at least one of H, alkali metal, alkaline earth metal, manganese, iron, cobalt, copper and zinc, and x is 0, 1 or 2.

[0015] In structural formula 1 of this invention, n refers to the valence state of M. It can be understood that when M is H, the catalyst is a hydroxycarboxylic acid and n is 1; when M is a metal, the catalyst is a hydroxycarboxylic acid salt and n is the valence state of the metal, which can be 1, 2 or 3.

[0016] According to the present invention, preferably, the weight ratio of the aldehyde to the solvent is 1:0.01-99, which can be any two values ​​formed by 1:0.01, 1:0.5, 1:1, 1:5, 1:10, 1:20, 1:30, 1:50, 1:60, 1:70, 1:90, 1:95, and 1:99, or values ​​within that range. More preferably, it is 1:1-99, and even more preferably, it is 1:4-20. Using the aldehyde-to-solvent weight ratio described above in this invention can further improve the aldehyde conversion rate and acid selectivity.

[0017] According to the present invention, preferably, the amount of catalyst used relative to 5g of aldehyde is 0.002-5g, which can be any two values ​​formed by 0.002g, 0.5g, 1g, 1.5g, 2g, 3g, 4g, 4.5g, and 5g, or a value within that range; more preferably, it is 0.003-1g; and more preferably, it is 0.005-0.05g. Using catalyst within the range described in the present invention can further improve the performance of aldehyde oxidation to acid production while reducing the amount of catalyst used.

[0018] In this invention, the oxidant is an oxygen-containing gas, which can be at least one of air, oxygen-enriched air, or air mixed with nitrogen. Preferably, the oxidant is oxygen-enriched air, wherein the oxygen content in the gas is 5-80% by volume.

[0019] According to the present invention, preferably, the amount of oxygen used is 0.5-8 mol relative to each mole of aldehyde, more preferably 0.5-4 mol.

[0020] According to the present invention, preferably, the aldehyde is a branched aldehyde having 1-10 carbon atoms and / or a straight-chain aldehyde having 1-10 carbon atoms, more preferably at least one selected from formaldehyde, acetaldehyde, propionaldehyde, isopropionaldehyde, butyraldehyde, 2-methylpropionaldehyde, pentanal, 3-methylbutyraldehyde, hexanal, 4-methylpentanal, octanal, 2-methylheptanal, 2-ethylhexanal, 2-ethyl-4-methylpentanal, 2-propylpentanal, nonanal, 3,5,5-trimethylhexanal, decanal, 2-propylheptanal, and 2-propyl-4-methylhexanal.

[0021] According to the present invention, preferably, the solvent is a carboxylic acid corresponding to an aldehyde. Choosing an acid corresponding to an aldehyde as the solvent facilitates subsequent processing. More preferably, it is at least one selected from formic acid, acetic acid, propionic acid, isopropionic acid, butyric acid, 2-methylpropionic acid, valeric acid, 3-methylbutyric acid, hexanoic acid, 4-methylvaleric acid, octanoic acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 2-ethyl-4-methylvaleric acid, 2-propylvaleric acid, nonanoic acid, 3,5,5-trimethylhexanoic acid, decanoic acid, 2-propylheptanoic acid, and 2-propyl-4-methylhexanoic acid.

[0022] According to the present invention, preferably, the aldehyde is a branched aldehyde with 4-10 carbon atoms, more preferably at least one selected from 2-methylpropionaldehyde, 3-methylbutanal, 4-methylpentanal, 2-methylheptanal, 2-ethylhexanal, 2-ethyl-4-methylpentanal, 2-propylpentanal, 3,5,5-trimethylhexanal, 2-propylheptanal, and 2-propyl-4-methylhexanal, and more preferably 2-ethylhexanal. Using the above-mentioned branched aldehydes of the present invention is beneficial to improving the selectivity of the product.

[0023] According to the present invention, preferably, the solvent is a branched carboxylic acid having 4-10 carbon atoms, more preferably at least one selected from 2-methylpropionic acid, 3-methylbutyric acid, 4-methylvaleric acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 2-ethyl-4-methylvaleric acid, 2-propylvaleric acid, 3,5,5-trimethylhexanoic acid, 2-propylheptanoic acid, and 2-propyl-4-methylhexanoic acid, and more preferably 2-ethylhexanoic acid.

[0024] In this invention, the catalyst has the structure shown in Formula 1, wherein when x is 0, the catalyst is α-hydroxycarboxylic acid or an α-hydroxycarboxylic acid salt; when x is 1, the catalyst is β-hydroxycarboxylic acid or a β-hydroxycarboxylic acid salt; and when x is 2, the catalyst is γ-hydroxycarboxylic acid or a γ-hydroxycarboxylic acid salt. Preferably, the catalyst is α-hydroxyacetic acid, α-hydroxypropionic acid, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-hydroxyvalerate, α-hydroxyisovalerate, α-hydroxyhexanoic acid, α-hydroxyisohexanoic acid, α-hydroxyheptanoic acid, α-hydroxyheptanoic acid, α-hydroxyoctanoic acid, α-hydroxyisooctanoic acid, α-hydroxynonanoic acid, α-hydroxyisononanoic acid, α-hydroxydecanoic acid, α-hydroxyisodecanoic acid, β-hydroxyacetic acid, β-hydroxypropionic acid, β-hydroxybutyric acid, β-hydroxyisobutyric acid, β-hydroxyvalerate, β-hydroxyisovalerate, β-hydroxyhexanoic acid, β-hydroxyisohexanoic acid, β-hydroxyhept ... β-hydroxyoctanoic acid, β-hydroxyisooctanoic acid, β-hydroxynonanoic acid, β-hydroxyisononanoic acid, β-hydroxydecanoic acid, β-hydroxyisodecanoic acid, γ-hydroxyacetic acid, γ-hydroxypropionic acid, γ-hydroxybutyric acid, γ-hydroxyisobutyric acid, γ-hydroxyvalerate, γ-hydroxyisovalerate, γ-hydroxyhexanoic acid, γ-hydroxyisohexanoic acid, γ-hydroxyheptanoic acid, γ-hydroxyoctanoic acid, γ-hydroxyisooctanoic acid, γ-hydroxynonanoic acid, γ-hydroxyisononanoic acid, γ-hydroxydecanoic acid, γ-hydroxyisodecanoic acid, and at least one of the alkali metal salts, alkaline earth metal salts, manganese salts, cobalt salts, copper salts, iron salts, and zinc salts of the above carboxylic acids.

[0025] In this invention, the catalyst simultaneously contains an amphiphilic carboxylic acid or carboxylate. The amphiphilic structure refers to the presence of both a hydroxyl group and a carboxyl group, with the hydroxyl group positioned one, two, or three carbons away from the carboxylic acid. The amphiphilic carboxylic acid or carboxylate can form cyclic microdomains rich in hydroxyl or carboxyl groups. The oxygen on these groups can form hydrogen bonds with α-H atoms, making the α-H atoms more electron-rich and easier to migrate, facilitating the extraction of α-H atoms. Simultaneously, the steric hindrance of these microdomains reduces alkyl rearrangements, thereby suppressing the formation of byproducts and further ensuring high selectivity for the target acid product.

[0026] According to the present invention, preferably, the reaction conditions include: a temperature of 30-120°C, a pressure of 0-6 MPa, and a time of 1-5 h; more preferably, the reaction conditions include: a temperature of 40-70°C, a pressure of 3-5 MPa, and a time of 1.5-3 h.

[0027] According to the present invention, preferably, the mixing method is a conventional method in the art, which only requires the aldehyde, solvent, oxidant and catalyst to be mixed evenly, preferably at least one of stirring, bubbling, spraying or rinsing.

[0028] According to the present invention, preferably, the reaction is carried out in a batch reactor, a microchannel reactor or a reflux reactor.

[0029] A second aspect of the present invention provides the use of the compound of Formula 1 in improving the conversion rate of raw materials and / or the selectivity of target products in the preparation of acids from aldehyde oxidation.

[0030] The present invention will be described in detail below through examples. In the following examples, all reagents are from the same batch and are commercially available.

[0031] Conversion rate refers to the percentage of acidic substances participating in the reaction relative to the total amount of acidic substances fed into the reactor.

[0032] Selectivity refers to the percentage of acid used to generate isooctanoic acid relative to the amount of acid reacted.

[0033] Yield refers to the percentage of acid used to generate isooctanoic acid relative to the total amount of acid fed into the feed.

[0034] This invention uses gas chromatography to detect the concentration of each substance in the reaction mixture before and after the reaction, thereby calculating the conversion rate, selectivity, and yield.

[0035] Example 1

[0036] 5g of isooctaldehyde, 0.0066g of sodium α-hydroxyacetate, and 60g of isooctanoic acid were mixed and added to a high-pressure reactor lined with polytetrafluoroethylene. Air was blown into the bottom of the reactor through a gas cylinder at a flow rate of 15mL / min, and stirring was started. The pressure inside the reactor was adjusted to 4.5MPa using a back pressure valve. The reactor was heated using a jacket, and the reaction temperature was controlled at 50℃. The reaction time was 2 hours. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity, and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0037] Example 2

[0038] 5g of isooctaldehyde, 3.42g of sodium α-hydroxyacetate, and 60g of isooctanoic acid were mixed and added to a high-pressure reactor lined with polytetrafluoroethylene. Air was blown into the bottom of the reactor through a gas cylinder at a flow rate of 15mL / min, and stirring was started. The pressure inside the reactor was adjusted to 4.5MPa using a back pressure valve. The reactor was heated using a jacket, and the reaction temperature was controlled at 50℃. The reaction time was 2 hours. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity, and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0039] Example 3

[0040] 5g of isooctaldehyde, 0.066g of sodium α-hydroxyacetate, and 60g of isooctanoic acid were mixed and added to a high-pressure reactor lined with polytetrafluoroethylene. Air was blown into the bottom of the reactor through a gas cylinder at a flow rate of 15mL / min, and stirring was started. The pressure inside the reactor was adjusted to 4.5MPa using a back pressure valve. The reactor was heated using a jacket, and the reaction temperature was controlled at 50℃. The reaction time was 2 hours. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity, and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0041] Example 4

[0042] 5g of isooctaldehyde, 0.0066g of sodium β-hydroxypropionate, and 60g of isooctanoic acid were mixed and added to a high-pressure reactor lined with polytetrafluoroethylene. Air was blown into the bottom of the reactor through a gas cylinder at a flow rate of 15mL / min, and stirring was started. The pressure inside the reactor was adjusted to 4.5MPa using a back pressure valve. The reactor was heated using a jacket, and the reaction temperature was controlled at 50℃. The reaction time was 2 hours. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity, and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0043] Example 5

[0044] 5g of isooctaldehyde, 3.42g of sodium β-hydroxypropionate, and 60g of isooctanoic acid were mixed and added to a high-pressure reactor lined with polytetrafluoroethylene. Air was blown into the bottom of the reactor through a gas cylinder at a flow rate of 15mL / min, and stirring was started. The pressure inside the reactor was adjusted to 4.5MPa using a back pressure valve. The reactor was heated using a jacket, and the reaction temperature was controlled at 50℃. The reaction time was 2 hours. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity, and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0045] Example 6

[0046] 5g of isooctaldehyde, 0.0066g of sodium γ-hydroxybutyrate, and 60g of isooctanoic acid were mixed and added to a high-pressure reactor lined with polytetrafluoroethylene. Air was blown into the bottom of the reactor through a gas cylinder at a flow rate of 15mL / min, and stirring was started. The pressure inside the reactor was adjusted to 4.5MPa using a back pressure valve. The reactor was heated using a jacket, and the reaction temperature was controlled at 50℃. The reaction time was 2 hours. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity, and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0047] Example 7

[0048] 5g of isooctaldehyde, 3.42g of sodium γ-hydroxybutyrate, and 60g of isooctanoic acid were mixed and added to a high-pressure reactor lined with polytetrafluoroethylene. Air was blown into the bottom of the reactor through a gas cylinder at a flow rate of 15mL / min, and stirring was started. The pressure inside the reactor was adjusted to 4.5MPa using a back pressure valve. The reactor was heated using a jacket, and the reaction temperature was controlled at 50℃. The reaction time was 2 hours. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity, and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0049] Example 8

[0050] The reaction was carried out according to Example 3, except that the pressure inside the reactor was 3.5 MPa. After the reaction, the concentration of each substance before and after the reaction was detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0051] Example 9

[0052] The reaction was carried out according to Example 3, except that the pressure inside the reactor was 5.5 MPa. After the reaction, the concentration of each substance before and after the reaction was detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0053] Example 10

[0054] The reaction was carried out according to Example 3, except that the reaction temperature was 40°C. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0055] Example 11

[0056] The reaction was carried out according to Example 3, except that the reaction temperature was 60°C. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0057] Example 12

[0058] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with α-hydroxyacetic acid. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0059] Example 13

[0060] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with β-hydroxypropionic acid. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0061] Example 14

[0062] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with γ-hydroxybutyric acid. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0063] Example 15

[0064] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with potassium α-hydroxyacetate. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0065] Example 16

[0066] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with zinc α-hydroxyacetate. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0067] Example 17

[0068] The reaction was carried out according to Example 1, except that the amount of sodium α-hydroxyacetate added was 0.033 g. After the reaction, the concentration of each substance before and after the reaction was detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0069] Example 18

[0070] The reaction was carried out according to Example 3, except that isooctaldehyde was replaced with 2-propylheptanal and isooctanoic acid was replaced with 2-propylheptanic acid. After the reaction, the concentration of each substance before and after the reaction was detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0071] Comparative Example 1

[0072] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with ethanol. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0073] Comparative Example 2

[0074] The reaction was carried out according to Example 1, except that 0.0066 g of sodium α-hydroxyacetate was replaced with 0.033 g of sodium acetate. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0075] Comparative Example 3

[0076] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with sodium δ-hydroxyacetate (x is 3). After the reaction, the concentration of each substance before and after the reaction was detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0077] Comparative Example 4

[0078] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with tridecacarboxylic acid. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0079] Comparative Example 5

[0080] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with sodium pentadecyl carboxylate. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0081] Comparative Example 6

[0082] The reaction was carried out according to Example 3, except that sodium α-hydroxyacetate was replaced with aluminum α-hydroxyacetate. After the reaction, the concentrations of each substance before and after the reaction were detected by gas chromatography, and the conversion rate, selectivity and isooctanoic acid yield were calculated. The results are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] As can be seen from the results in Table 1, the preferred embodiments of the present invention can achieve higher aldehyde conversion rates, organic acid selectivity, and yields. The results of the examples demonstrate that using the catalyst and conditions for aldehyde oxidation to acid preparation provided by the present invention can achieve higher aldehyde conversion rates, organic acid selectivity, and yields. Comparative examples and comparative examples show that using the hydroxycarboxylic acid or hydroxycarboxylate salt with the structure of Formula 1 provided by the present invention can achieve higher aldehyde conversion rates, organic acid selectivity, and yields while reducing the formation of byproducts.

[0087] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing an acid by aldehyde oxidation, characterized in that, A catalyst, solvent, aldehyde, and oxidant are mixed to carry out a reaction, wherein the catalyst is selected from at least one compound with the structure shown in Formula 1: In Formula 1, R is an alkyl group with 1-30 carbon atoms, M is at least one of H, alkali metal, alkaline earth metal, manganese, iron, cobalt, copper and zinc, and x is 0, 1 or 2.

2. The method according to claim 1, wherein, The weight ratio of the aldehyde to the solvent is 1:0.01-99, preferably 1:1-99, and more preferably 1:4-20; And / or, relative to 5g of aldehyde, the amount of the catalyst is 0.002-5g, preferably 0.003-1g, and more preferably 0.005-0.05g.

3. The method according to claim 1, wherein, The oxidant is a gas containing oxygen; Preferably, the oxygen content in the oxidant is 5-80% by volume; And / or, the amount of oxygen used is 0.5-8 mol relative to each mole of aldehyde, preferably 0.5-4 mol.

4. The method according to claim 1, wherein, The aldehyde is a branched aldehyde with 1-10 carbon atoms and / or a straight-chain aldehyde with 1-10 carbon atoms. Preferably, the aldehyde is at least one selected from formaldehyde, acetaldehyde, propionaldehyde, isopropionaldehyde, butyraldehyde, 2-methylpropionaldehyde, pentanal, 3-methylbutyraldehyde, hexanal, 4-methylpentanal, octanal, 2-methylheptanal, 2-ethylhexanal, 2-ethyl-4-methylpentanal, 2-propylpentanal, nonanal, 3,5,5-trimethylhexanal, decanal, 2-propylheptanal, and 2-propyl-4-methylhexanal; And / or, the solvent is a carboxylic acid corresponding to an aldehyde, preferably at least one of formic acid, acetic acid, propionic acid, isopropionic acid, butyric acid, 2-methylpropionic acid, valeric acid, 3-methylbutyric acid, hexanoic acid, 4-methylvaleric acid, octanoic acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 2-ethyl-4-methylvaleric acid, 2-propylvaleric acid, nonanoic acid, 3,5,5-trimethylhexanoic acid, decanoic acid, 2-propylheptanoic acid, and 2-propyl-4-methylhexanoic acid.

5. The method according to claim 1, wherein, The aldehyde is a branched aldehyde with 4-10 carbon atoms; Preferably, the aldehyde is at least one selected from 2-methylpropionaldehyde, 3-methylbutanal, 4-methylpentanal, 2-methylheptanal, 2-ethylhexanal, 2-ethyl-4-methylpentanal, 2-propylpentanal, 3,5,5-trimethylhexanal, 2-propylheptanal, and 2-propyl-4-methylhexanal. More preferably, the aldehyde is 2-ethylhexanal; And / or, the solvent is a branched carboxylic acid with 4-10 carbon atoms; Preferably, the solvent is at least one selected from 2-methylpropionic acid, 3-methylbutyric acid, 4-methylvaleric acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 2-ethyl-4-methylvaleric acid, 2-propylvaleric acid, 3,5,5-trimethylhexanoic acid, 2-propylheptanoic acid, and 2-propyl-4-methylhexanoic acid. More preferably, the solvent is 2-ethylhexanoic acid.

6. The method according to claim 1, wherein, The catalyst is α-hydroxyacetic acid, α-hydroxypropionic acid, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-hydroxyvalerate, α-hydroxyisovalerate, α-hydroxyhexanoic acid, α-hydroxyisohexanoic acid, α-hydroxyheptanoic acid, α-hydroxyisoheptanoic acid, α-hydroxyoctanoic acid, α-hydroxyisooctanoic acid, α-hydroxynonanoic acid, α-hydroxyisononanoic acid, α-hydroxydecanoic acid, α-hydroxyisodecanoic acid, β-hydroxyacetic acid, β-hydroxypropionic acid, β-hydroxybutyric acid, β-hydroxyisobutyric acid, β-hydroxyvalerate, β-hydroxyisovalerate, β-hydroxyhexanoic acid, β-hydroxyisohexanoic acid, β-hydroxyheptanoic acid, β-hydroxyisoheptanoic ...heptanoic acid, β-hydroxypropionic acid, β-hydroxybutyric acid, β-hydroxyisoheptanoic acid, β-hydroxypropionic acid, β-hydroxycaprylic acid, β-hydroxyisohexanoic acid, β-hydroxyheptanoic acid, β-hydroxypropionic acid, β-hydroxycaprylic acid, β-hydroxyisoheptanoic acid, β-hydroxypropionic acid, β-hydroxycaprylic acid, β-hydroxyheptano γ-hydroxyoctanoic acid, β-hydroxyisooctanoic acid, β-hydroxynonanoic acid, β-hydroxyisononanoic acid, β-hydroxydecanoic acid, β-hydroxyisodecanoic acid, γ-hydroxyacetic acid, γ-hydroxypropionic acid, γ-hydroxybutyric acid, γ-hydroxyisobutyric acid, γ-hydroxyvalerateic acid, γ-hydroxyisovalerateic acid, γ-hydroxyhexanoic acid, γ-hydroxyisohexanoic acid, γ-hydroxyheptanoic acid, γ-hydroxyoctanoic acid, γ-hydroxyisooctanoic acid, γ-hydroxynonanoic acid, γ-hydroxyisononanoic acid, γ-hydroxydecanoic acid, γ-hydroxyisodecanoic acid, and at least one of the alkali metal salts, alkaline earth metal salts, manganese salts, cobalt salts, copper salts, iron salts, and zinc salts of the above acids.

7. The method according to claim 1, wherein, The reaction conditions include: temperature of 30-120℃, pressure of 0-6MPa, and time of 1-5h; Preferably, the reaction conditions include: a temperature of 40-70°C, a pressure of 3-5 MPa, and a time of 1.5-3 h.

8. The method according to claim 1, wherein, The mixing method is at least one of stirring, bubbling, spraying, or spraying.

9. The method according to any one of claims 1-8, wherein, The reaction is carried out in a batch reactor, a microchannel reactor, or a reflux reactor.

10. Application of the compound shown in Formula 1 in improving the conversion rate of raw materials and / or the selectivity of target products in the oxidation of aldehydes to acids.

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