A method for preparing dicarboxylic acid by a double carbonylation reaction using dihydric alcohol or cyclic ether as a raw material

Abstract

The application relates to the technical field of dicarboxylic acid preparation, and particularly discloses a method for preparing dicarboxylic acid by a double carbonylation reaction with dihydric alcohol or a cyclic ether as raw material, wherein the method comprises the following steps: sequentially adding dihydric alcohol or a cyclic ether with n carbon atoms, water, a noble metal catalyst and an iodine-containing promoter into a reaction kettle to form a reaction system, n is an integer greater than or equal to 3; after carbon monoxide or a mixed gas atmosphere of carbon monoxide and hydrogen is introduced into the reaction kettle, the reaction system is stirred and heated, and dicarboxylic acid with n+2 carbon atoms is synthesized by a double carbonylation reaction under the condition of temperature rise. In the application, water is used as an additive, the selectivity of dicarboxylic acid is significantly improved without the interference of organic acid, byproduct esterification is avoided, the purity of the target product is higher, and the separation process is simplified, so that the method has the advantages of high dicarboxylic acid yield and high reaction efficiency, and has good commercial value.

Description

Technical Field

[0001] This invention relates to the field of dicarboxylic acid preparation technology, and in particular to a method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction. Background Technology

[0002] Dicarboxylic acids are crucial in the chemical industry, widely used as monomers, plasticizers, and additives in the preparation of polyamides, polyesters, and polyurethane resins. For example, the polyesters and polyamides produced by the polycondensation of dicarboxylic acids with diols and diamines are fundamental raw materials for the plastics and fiber industries. The carboxyl esterification, acylation, and decarboxylation reactivity of dicarboxylic acids allows for the synthesis of pharmaceuticals, fragrances, pesticides, and other fine chemicals. Furthermore, dicarboxylic acids serve as pickling agents, complexing agents, and pH adjusters in metal processing, water treatment, and textile printing and dyeing. Therefore, dicarboxylic acids play an irreplaceable role in modern industry.

[0003] The preparation of dicarboxylic acids from diol carbonylation offers advantages such as high atom utilization, environmental friendliness, and readily available and renewable raw materials. Taking adipic acid, a popular chemical, as an example, its industrial production began in 1937 when DuPont first achieved large-scale production by oxidizing cyclohexanol (obtained from the hydrogenation of phenol) with nitric acid. With the rise of petrochemicals, cyclohexane gradually replaced phenol as a cheaper raw material. Scientific Design Corporation (SD) developed a cyclohexane oxidation process using anhydrous boric acid as a catalyst, increasing the selectivity of KA oil (a mixture of cyclohexanol and cyclohexanone) to 85%-90%. This two-step process (cyclohexane → KA oil → adipic acid) significantly reduced costs and became the mainstream route for adipic acid production. However, this route uses nitric acid as an oxidant, generating large amounts of nitrogen oxides, leading to severe environmental pollution. This high pollution and energy consumption make the process unsuitable for modern chemical industry development and put it under pressure for transformation. Diols are widely available and inexpensive basic chemicals that can be used to prepare dicarboxylic acids through dicarbonylation. However, due to the poor selectivity of this reaction and the low utilization rate of raw materials, they are rarely used in industrial production.

[0004] The earliest process for preparing carboxylic acids from alcohol carbonylation was achieved by Monsanto in the 1980s using a rhodium catalyst to carbonylate methanol to produce acetic acid, significantly reducing the production cost of acetic acid. This method has become the mainstream technology for acetic acid production, but it is difficult to apply in the carbonylation of diols. In 1977, Monsanto reported the synthesis of dicarboxylic acids from diols via dicarbonylation using rhodium and iridium catalyst precursors. However, this reaction requires a large amount of organic acid, such as acetic acid, as a solvent, and the low selectivity of the resulting dicarboxylic acid limits its industrial application. In 2023, Yang et al. used a rhodium catalyst, iodine promoter, hydrogen, and carbon monoxide at a total pressure of 6 MPa and a reaction temperature of 170 °C to achieve a high-selectivity preparation of dicarboxylic acids from cyclic ethers or diols via carbonylation with a yield of 84%. However, this method also requires acetic acid as a solvent, and it is difficult to maintain its yield and selectivity at high concentrations.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction. This method aims to solve the problems of low product selectivity, the need for organic acids as solvents, high production costs, difficult product separation, and excessive energy consumption in the preparation of dicarboxylic acids from diols or cyclic ethers via carbonylation reaction.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, comprising the steps of:

[0009] A reaction system is formed by sequentially adding a diol or cyclic ether with n carbon atoms, water, a noble metal catalyst, and an iodine-containing promoter to a reaction vessel, where n is an integer greater than or equal to 3.

[0010] After introducing carbon monoxide or a mixture of carbon monoxide and hydrogen into the reaction vessel, the reaction system is stirred and heated. Under elevated temperature conditions, dicarboxylic acids with n+2 carbon atoms are synthesized with high selectivity through a dicarbonylation reaction.

[0011] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the noble metal catalyst is a rhodium salt catalyst.

[0012] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the rhodium salt catalyst is RhI3, Rh(acac)(CO)2, or Rh[Cl(CO)]. 2,One of [RhCl(COD)]2 and RhCl3.

[0013] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the concentration of the noble metal element in the noble metal catalyst in the reaction system is 0.001-1 mol / L.

[0014] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the iodine-containing catalyst is one of iodine, organic iodine, and hydroiodic acid aqueous solution, and the molar ratio of iodine in the iodine-containing catalyst to the noble metal in the noble metal catalyst is 0.1:1-1000:1.

[0015] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the diol is one of 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol; and the cyclic ether is one of oxetane, tetrahydrofuran, and tetrahydropyran.

[0016] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the molar ratio of the noble metal catalyst to the diol or cyclic ether is 1:10 to 1:10000.

[0017] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the pressure of the hydrogen gas is 0-10 MPa and the pressure of the carbon monoxide gas is 0.2-10 MPa.

[0018] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction includes a step of stirring and heating the reaction system after introducing carbon monoxide or a mixed atmosphere of carbon monoxide and hydrogen into the reaction vessel. The stirring and heating temperature is 100-280℃, and the stirring and heating time is 2-45h.

[0019] The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, wherein the mass ratio of diol or cyclic ether to water in the reaction system is 1:0.01-100.

[0020] Beneficial effects: This invention provides a method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction. Compared with previous carbonylation methods that require a large amount of organic acid solvents, the method of this invention has the advantages of no organic acid solvents, high yield, and high reaction efficiency, and has great commercial value. Attached Figure Description

[0021] Figure 1This is a flowchart of a method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, according to the present invention.

[0022] Figure 2 This is a liquid chromatography result of the product obtained in Example 1 of the present invention.

[0023] Figure 3 This is the hydrogen NMR spectrum of the product obtained in Example 1 of the present invention.

[0024] Figure 4 This is the liquid phase standard curve for adipic acid.

[0025] Figure 5 The standard curve for 2-methylglutaric acid is shown in the liquid phase. Detailed Implementation

[0026] This invention provides a method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] Existing technologies (such as Monsanto and Yang methods) require organic acid solvents such as acetic acid to prepare dicarboxylic acids, which leads to the following problems: high cost, large quantities of organic acid solvents are required and recovery is energy-intensive; separation is difficult, as the product dicarboxylic acid has similar physical properties to the organic acid solvent and requires complex distillation / crystallization processes.

[0028] Based on this, the present invention provides a method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, such as... Figure 1 As shown, it includes the following steps:

[0029] S10. Add a diol or cyclic ether with n carbon atoms, water, a noble metal catalyst and an iodine-containing promoter to the reactor in sequence to form a reaction system, where n is an integer greater than or equal to 3.

[0030] S20. After introducing carbon monoxide or a mixture of carbon monoxide and hydrogen into the reaction vessel, the reaction system is stirred and heated. Under the heating condition, dicarboxylic acids with n+2 carbon atoms are synthesized with high selectivity through a dicarbonylation reaction.

[0031] Compared to conventional carbonylation methods that require large amounts of organic acid solvents, the method for preparing dicarboxylic acids from diols or cyclic ethers via dicarbonylation provided by this invention does not require organic acid solvents. Only a small amount of water is needed as an additive. The diol can undergo dicarbonylation directly upon heating in an atmosphere of carbon monoxide or a mixture of carbon monoxide and hydrogen, under the action of a noble metal catalyst and an iodine-containing promoter, thereby generating dicarboxylic acids with n+2 carbon atoms. This method eliminates the need for organic acid solvents, significantly improves the selectivity of dicarboxylic acids in a solvent-free system, resulting in higher purity of the target product and a simplified separation process. Therefore, this method has the advantages of high dicarboxylic acid yield and high reaction efficiency, and has significant commercial value.

[0032] Specifically, the reaction in this invention is essentially a dicarbonylation tandem reaction, and the key steps are as follows (taking a diol as the raw material and HI as an iodine-containing accelerator as an example):

[0033] First, the iodination activation reaction occurs: that is, the diol (HO-R-OH) reacts with the iodine-containing accelerator (HI) to produce iodohydrin (HO-RI): HO-R-OH + HI → HO-R-I + H2O;

[0034] Then the first carbonylation reaction occurs: namely, the reaction of iodoethanol with [Rh(CO)2I2] - The complex undergoes oxidative addition, followed by CO insertion to generate an acyl rhodium intermediate, which is then hydrolyzed to yield ω-iodocarboxylic acid.

[0035] Then a second iodination and carbonylation occur: ω-iodocarboxylic acid (HOOC-RI) repeats the above steps to generate a dicarboxylic acid (HOOC-R-COOH):

[0036]

[0037] The method of this invention does not require organic acid solvents. Water, as an additive, can directly participate in the final hydrolysis reaction of carbonylation (to generate carboxylic acid), replacing the protonation pathway of carboxylate in acetic acid solvents. Iodine-containing promoters (such as HI) can dissociate into I in the aqueous phase. - and H + To maintain the iodine ion concentration required for the catalytic cycle and ensure the presence of elemental iodine in [Rh(CO)2]. - Active species exist stably.

[0038] In some embodiments, the noble metal catalyst is a rhodium salt catalyst, wherein the rhodium salt catalyst is RhI3, Rh(acac)(CO)2, or Rh[Cl(CO)]. 2, It is one of [RhCl(COD)]2 and RhCl3, but not limited to this.

[0039] In some embodiments, the concentration of the noble metal element in the noble metal catalyst in the reaction system is 0.001-1 mol / L.

[0040] In some embodiments, the iodine-containing catalyst is one of iodine, organic iodine, and hydroiodic acid aqueous solution, and the molar ratio of iodine in the iodine-containing catalyst to the noble metal in the noble metal catalyst is 0.1:1-1000:1, but is not limited thereto.

[0041] In some embodiments, the diol is one of 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol; the cyclic ether is one of oxetane, tetrahydrofuran, and tetrahydropyran, but is not limited thereto.

[0042] In some embodiments, the molar ratio of the noble metal catalyst to the diol or cyclic ether is 1:10 to 1:10000.

[0043] In some embodiments, the pressure of the hydrogen is 0-10 MPa, and the pressure of the carbon monoxide is 0.2-10 MPa.

[0044] In some embodiments, in the step of introducing carbon monoxide or carbon monoxide and hydrogen into the reaction vessel and then stirring and heating the reaction system, the stirring and heating temperature is 100-280°C and the stirring and heating time is 2-45 hours.

[0045] In some embodiments, the mass ratio of diol or cyclic ether to water in the reaction system is 1:0.01-100.

[0046] The present invention will be further explained and illustrated below through specific embodiments:

[0047] The general experimental method for the reaction mode used in the embodiments of the present invention is as follows:

[0048] The reaction was carried out in a 50 mL high-temperature, high-pressure reactor, with a temperature-controlled jacket heating system. The precious metal catalyst, iodine promoter, raw material diol or cyclic ether, and water were accurately weighed and added sequentially to the reactor. A carbon monoxide atmosphere or a mixture of carbon monoxide and hydrogen was introduced, and stirring and heating were initiated to start the reaction. After the reaction was completed, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, including liquid chromatography and nuclear magnetic resonance.

[0049] The liquid chromatography conditions were as follows: the instrument for detecting the concentration of dicarboxylic acids was a Waters H-Class series high-performance liquid chromatograph (RID detector, Alltech OA-1000 Organic Acids HPLC (300mm × 6.5mm), flow rate 1.0mL / min, column temperature 50℃, and mobile phase consisting of 10% methanol and 90% 0.1g / L trifluoroacetic acid aqueous solution).

[0050] Nuclear Magnetic Resonance (NMR): Dissolve an appropriate amount of the dicarboxylic acid sample to be tested in a suitable deuterated solvent to prepare a solution of appropriate concentration, controlled at 50 mg / mL. Power on the NMR spectrometer to allow it to warm up and stabilize. Tune the instrument to match the radio frequency with the hydrogen nuclei, and shim the field to ensure uniformity. Sample introduction and testing: Inject the sample solution into the NMR tube and place the probe. Set parameters such as pulse sequence and sampling frequency, and acquire the time-domain signal. Perform Fourier transform on the acquired signal, and after phase correction and baseline correction, obtain an analyzable 1H NMR spectrum.

[0051] The yield of dicarboxylic acids is an important indicator for measuring production capacity and quality. It is calculated as follows: Yield of dicarboxylic acids = (Actual yield of dicarboxylic acids / Theoretical yield of dicarboxylic acids) × 100%.

[0052] Example 1

[0053] In a 50 ml high-pressure reactor, 5.4 g of 1,4-butanediol, a small amount of water (5 g), 0.022 g of Rh(acac)(CO)₂, and 0.50 g of elemental iodine were added sequentially. Hydrogen gas at 4 MPa and carbon monoxide at 4 MPa were then introduced, and the reactor was heated to 160 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 68%, and the yield of 2-methylglutaric acid was 10%.

[0054] The products obtained in the examples were analyzed by liquid chromatography and nuclear magnetic resonance, and the results are as follows: Figures 2-3 As shown, where, Figure 2 To obtain the liquid chromatography results of the product. Figure 3 The hydrogen NMR spectrum of the product was obtained. (Combined with...) Figures 2-3 and refer to Figure 4 and Figure 5 The liquid chromatography standard plots of adipic acid and 2-methylglutaric acid shown reveal that... Figure 2 The liquid chromatogram shows two main chromatographic peaks with retention times (RT) and... Figure 4 (Adipic acid standard curve) and Figure 5 The retention times of the target analytes in the (2-methylglutaric acid standard curve) are consistent, with peak 1's retention time matching that of adipic acid standard. Figure 4This indicates the presence of adipic acid, and the retention time of peak 2 matches that of 2-methylglutaric acid standard. Figure 5 The presence of 2-methylglutaric acid is indicated by the chromatogram. Therefore, the liquid chromatography confirms that the product contains both adipic acid and 2-methylglutaric acid. Figure 3 The 1H NMR spectrum showed the following characteristic peaks (chemical shifts δ): δ 1.6 ppm (multiplex): corresponding to the proton of the methylene chain (-CH2-CH2-) in adipic acid; δ 2.3 ppm (triplet): corresponding to the proton of the ortho-methylene group (-CH2-COOH) in adipic acid; δ 1.1 ppm (doublet): corresponding to the proton of the methyl group (-CH3) in 2-methylglutaric acid; δ 2.0–2.6 ppm (complex multiplet): corresponding to the protons of the methine (>CH-) and methylene (-CH2-) groups in 2-methylglutaric acid. Therefore, the chemical shifts in the 1H NMR spectrum perfectly match the molecular structures of the two target products. Liquid chromatography (retention time matching) and 1H NMR (characteristic proton peak matching) both verified that the products of Example 1 were adipic acid (main product) and 2-methylglutaric acid (byproduct).

[0055] Example 2

[0056] In a 50 ml high-pressure reactor, 5.4 g of 1,4-butanediol, 3 g of water (required for the reaction), 0.054 g of RhI3, and 0.50 g of elemental iodine were added sequentially. Then, hydrogen gas at 4 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 180 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 35%, and the yield of 2-methylglutaric acid was 26%.

[0057] Example 3

[0058] Add 5.4 g of 1,4-butanediol, a small amount of water (2 g), and 0.026 g of Rh[Cl(CO)] to a 50 ml high-pressure reactor. 2, After adding 0.50 g of elemental iodine, hydrogen gas at 2 MPa and carbon monoxide at 3 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 15 h. After the reaction was completed, the reaction solution was diluted to a final volume, filtered, and used for subsequent testing and analysis, yielding adipic acid with a yield of 55% and 2-methylglutaric acid with a yield of 25%.

[0059] Example 4

[0060] In a 50 ml high-pressure reactor, 5.4 g of 1,4-butanediol, a small amount of water (3 g), 0.049 g of [RhCl(COD)]₂, and 0.54 g of iodomethane were added sequentially. Then, hydrogen gas at 4 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 180 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 63%, and the yield of 2-methylglutaric acid was 13%.

[0061] Example 5

[0062] In a 50 ml high-pressure reactor, 5.4 g of 1,4-butanediol, a small amount of water (3 g), 0.1 g of [RhCl(COD)]₂, and 0.15 g of elemental iodine were added sequentially. Then, hydrogen gas at 2 MPa and carbon monoxide at 3 MPa were introduced, and the reactor was heated to 180 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 57%, and the yield of 2-methylglutaric acid was 22%.

[0063] Example 6

[0064] In a 50 ml high-pressure reactor, 5.4 g of 1,3-propanediol, a small amount of water (5 g), 0.1 g of Rh(acac)(CO)₂, and 0.15 g of elemental iodine were added sequentially. Then, hydrogen gas (4 MPa) and carbon monoxide gas (4 MPa) were introduced, and the reactor was heated to 160 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of glutaric acid was 50%, and the yield of 2-methylsuccinic acid was 20%.

[0065] Example 7

[0066] 5.4 g of 1,4-butanediol, 5 g of water (required for the reaction), 0.1 g of Rh(acac)(CO)₂, and 0.15 g of HI were added sequentially to a 50 ml high-pressure reactor, and the reactor was then sealed. Hydrogen gas at 0 MPa and carbon monoxide at 5 MPa were introduced, and the reactor was heated to 160 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 73%, and the yield of 2-methylglutaric acid was 12%.

[0067] Example 8

[0068] In a 50 ml high-pressure reactor, 5.4 g of 1,4-butanediol, a small amount of water (5 g), 0.022 g of Rh(acac)(CO)₂, and 0.15 g of elemental iodine were added sequentially. Then, hydrogen gas (4 MPa) and carbon monoxide gas (4 MPa) were introduced, and the reactor was heated to 120 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 30%, and the yield of 2-methylglutaric acid was 5%.

[0069] Example 9

[0070] In a 50 ml high-pressure reactor, 5.4 g of 1,5-pentanediol, a small amount of water (4 g), 0.1 g of Rh(acac)(CO)₂, and 0.15 g of elemental iodine were added sequentially. Then, hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 180 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of pimelic acid was 65%, and the yield of 2-methyladipic acid was 16%.

[0071] Example 10

[0072] In a 50 ml high-pressure reactor, 5.4 g of tetrahydrofuran, a small amount of water (4 g), 0.1 g of Rh(acac)(CO)₂, and 0.15 g of elemental iodine were added sequentially. Then, hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 180 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 78%, and the yield of 2-methylglutaric acid was 11%.

[0073] Example 11

[0074] 5.4 g of oxetane, 3 g of water, 0.1 g of Rh(acac)(CO)₂, and 0.1 g of HI were added sequentially to a 50 ml high-pressure reactor, followed by sealing. Hydrogen gas at 0 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 170 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of glutaric acid was 62%, and the yield of 2-methylsuccinic acid was 16%.

[0075] Example 12

[0076] In a 50 ml high-pressure reactor, 5.4 g of tetrahydropyran, a small amount of water (3 g), 0.055 g of [RhCl(COD)]₂, and 0.54 g of iodomethane were added sequentially. Then, hydrogen gas at 4 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 190 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of pimelic acid was 56%, and the yield of 2-methyladipic acid was 21%.

[0077] Comparative Example 1

[0078] In a 50 ml high-pressure reactor, 5.4 g of 1,4-butanediol, a small amount of water (5 g), 0.022 g of IrCl3, and 0.50 g of iodine were added sequentially. Then, hydrogen gas (4 MPa) and carbon monoxide gas (4 MPa) were introduced, and the reactor was heated to 160 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 3%, and the yield of 2-methylglutaric acid was 4%.

[0079] Comparative Example 2

[0080] In a 50 ml high-pressure reactor, 5.4 g of 1,4-butanediol, a small amount of water (10 g), 0.022 g of Rh(acac)(CO)₂, and 0.50 g of LiI were added sequentially, and the reactor was then sealed. Hydrogen gas at 4 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 160 °C and stirred for 15 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis. The yield of adipic acid was 1%, and the yield of 2-methylglutaric acid was 3%.

[0081] Comparing the data from Example 1 and Comparative Example 1 reveals that when IrCl3 is used as a catalyst, the yields of the target products, adipic acid and 2-methylglutaric acid, are extremely low, indicating poor catalytic performance and unsuitability as a catalyst for the preparation of dicarboxylic acids from diols or cyclic ethers in a solvent system without organic acids. Comparing the data from Example 1 and Comparative Example 2 reveals that when LiI is used as an iodine-containing catalyst, the yields of the target products, adipic acid and 2-methylglutaric acid, are also extremely low, indicating that LiI is unsuitable as a promoter for the preparation of dicarboxylic acids from diols or cyclic ethers in a solvent system without organic acids.

[0082] Comparing the data from Example 1 and Example 8 reveals that the only difference between the two is the reaction temperature. Although the target products adipic acid and 2-methylglutaric acid can be generated at both 120°C and 160°C, the yield of the target product in Example 8 is significantly lower than that in Example 1. This indicates that within a certain range, the higher the temperature, the more conducive it is to the dicarbonylation reaction, and the higher the yield of the target product can be obtained.

[0083] In summary, the method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction provided by this invention does not require organic acid solvents. The diols or cyclic ethers can undergo a dicarbonylation reaction directly upon heating in a mixed atmosphere of carbon monoxide and hydrogen, under the action of an Rh salt catalyst and an iodine-containing promoter, thereby generating dicarboxylic acids with n+2 carbon atoms. This method does not require organic acid solvents, and the selectivity of dicarboxylic acids is significantly improved without the interference of organic acids, resulting in higher purity of the target product and a simplified separation process. Therefore, this method has the advantages of high dicarboxylic acid yield and high reaction efficiency, and has good commercial value.

[0084] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction, characterized in that, Including the following steps: A diol or cyclic ether with n carbon atoms, water, a rhodium salt catalyst, and an iodine-containing promoter are sequentially added to a reaction vessel to form a reaction system, where n is an integer greater than or equal to 3. The rhodium salt catalyst is Rh(acac)(CO)2 or Rh[Cl(CO)]. 2, One of [RhCl(COD)]2 and RhCl3; the iodine-containing accelerator is one of iodine, iodomethane, and hydroiodic acid aqueous solution; the diol is one of 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol; the cyclic ether is one of oxetane, tetrahydrofuran, and tetrahydropyran. After introducing carbon monoxide or a mixture of carbon monoxide and hydrogen into the reaction vessel, the reaction system is stirred and heated. Under elevated temperature conditions, dicarboxylic acids with n+2 carbon atoms are synthesized with high selectivity through a dicarbonylation reaction. The stirring and heating temperature is 160-180℃.

2. The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction according to claim 1, characterized in that, The concentration of the noble metal element in the rhodium salt catalyst in the reaction system is 0.001-1 mol / L.

3. The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction according to claim 1, characterized in that, The molar ratio of iodine in the iodine-containing accelerator to the noble metal in the rhodium salt catalyst is 0.1:1-1000:

1.

4. The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction according to claim 1, characterized in that, The molar ratio of the rhodium salt catalyst to the diol or cyclic ether is 1:10 - 1:10000.

5. The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction according to claim 1, characterized in that, The pressure of the hydrogen gas is 0-10 MPa, and the pressure of the carbon monoxide gas is 0.2-10 MPa.

6. The method for preparing dicarboxylic acids from diols or cyclic ethers via a dicarbonylation reaction according to claim 1, characterized in that, In the reaction system, the mass ratio of diol or cyclic ether to water is 1:1-100.

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