A method for preparing a monovalent carboxylic acid by a carbonylation reaction using a monovalent alcohol or ether as a raw material

Abstract

The application relates to the technical field of dicarboxylic acid preparation, and particularly discloses a method for preparing monocarboxylic acid by a carbonylation reaction with a monohydric alcohol or ether as raw material, wherein the method comprises the following steps: adding a monohydric alcohol or ether with n carbon atoms, water, a noble metal catalyst and an iodine-containing promoter into a reaction kettle to form a reaction system, wherein n is an integer greater than or equal to 2; 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 under the condition of temperature rise, a monocarboxylic acid with n+1 carbon atoms is synthesized by a carbonylation reaction with high selectivity. In the application, water is used as an additive, the selectivity of the monocarboxylic acid is significantly improved without the interference of organic acid, the byproduct of 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 no organic acid solvent, high yield and high reaction efficiency, and has good commercial value.

Description

Technical Field

[0001] This invention relates to the field of monocarboxylic acid preparation technology, and in particular to a method for preparing monocarboxylic acids from monohydric alcohols or ethers via a carbonylation reaction. Background Technology

[0002] Propionic acid (CH3CH2COOH) is an important short-chain fatty acid with wide applications in multiple fields. Its importance is mainly reflected in the following aspects: 1. Preservatives in the food industry: Propionic acid and its salts (sodium propionate, calcium propionate) effectively inhibit the growth of molds, yeasts, and certain bacteria, and are widely used in bread, pastries, cheese, and other foods, significantly extending shelf life. 2. Chemical and industrial raw materials: Propionic acid is an important raw material for the synthesis of many chemicals, used in the production of coatings, plastics, and fragrances. Herbicides: such as 2,4-D propionic acid (2,4-DP). Cellulose plastics: used in the manufacture of thermoplastic materials. Solvents and processing aids: used as solvents or reaction media in the pharmaceutical and rubber industries. 3. Applications in the pharmaceutical field: Drug synthesis: Propionic acid derivatives are key components of many drugs, such as: Non-steroidal anti-inflammatory drugs (NSAIDs): such as ibuprofen and naproxen, used for anti-inflammatory and analgesic purposes. Antifungal drugs: Some propionic acid derivatives have antimicrobial activity. Pharmaceutical excipients: Propionates can be used as drug carriers or sustained-release agents.

[0003] In the 1960s, Monsanto developed a method to obtain monoacids or dicarboxylic acids using alcohols as substrates, rhodium as catalysts, acetic acid as solvents, and a carbon monoxide atmosphere (US Patent 4060547). Chinese Patent CN113004139A discloses a method to obtain propionic acid via carbonylation using ethanol as a substrate, rhodium iodide as a catalyst, hydroiodic acid, lithium iodide, iodoethane as iodine reagents, bis(diphenylphosphine)methane monosulfide as a ligand, and propionic acid as a solvent. Chinese Patent CN 102794198A discloses a copolymer rhodium catalyst, ethanol, co-catalyst iodoethane, and accelerator lithium iodide, with a carbon monoxide pressure of 4.0-6.0 MPa and a reaction temperature of 130-220°C. In 1987, Gustave Bitsi reported the carbonylation of ethanol at 200 °C with ruthenium as a catalyst, iodine as a co-catalyst, and 450 bar of carbon monoxide, but the yield was only 42%, with diethyl ether and ethane as byproducts (Journal of Molecular Catalysts, 40 (1987) 71-82). In 1997, RV Chaudhari reported the carbonylation of ethanol at 220 °C with nickel as a catalyst, hydroiodic acid as a promoter, isoquinoline as a ligand, propionic acid as a solvent, and H2 / CO (961.52 kPa / 2885 kPa) to obtain propionic acid (Journal of Molecular Catalysis A: Chemical 118 (1997) 9-19).

[0004] As can be seen from the above, the preparation of propionic acid from ethanol usually requires a large amount of solvents, additives, ligands, etc., and the selectivity of obtaining the target product propionic acid is low, which limits its application in the industrial field.

[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 monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction. This method aims to solve the problems that existing methods for preparing propionic acid usually require large amounts of solvents, additives, ligands, etc., and the selectivity of the target product propionic acid is low, which limits its application in the industrial field.

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

[0008] A method for preparing a monocarboxylic acid from a monohydric alcohol or ether via a carbonylation reaction, comprising the steps of:

[0009] A reaction system is formed by adding a monohydric alcohol or 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 2, and the ether is one of diethyl ether, n-propyl ether, n-butyl ether, n-pentyl ether and propylene oxide.

[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 the elevated temperature conditions, a monocarboxylic acid with n+1 carbon atoms is synthesized with high selectivity through a carbonylation reaction.

[0011] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the noble metal catalyst is a rhodium salt catalyst or an iridium salt catalyst.

[0012] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the rhodium salt catalyst is RhI3, Rh(acac)(CO)2, or Rh[Cl(CO)]. 2, One of [RhCl(COD)]2 and RhCl3; the iridium salt catalyst is one of IrCl3 and IrI3.

[0013] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the molar ratio of the noble metal catalyst to the monohydric alcohol or ether is 1:10 to 1:10000.

[0014] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the iodine-containing promoter is one of iodine, organic iodine, and hydroiodic acid aqueous solution, and the molar ratio of iodine in the iodine-containing promoter to the noble metal in the noble metal catalyst is 0.1:1-10:1.

[0015] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the monohydric alcohol is one of ethanol, n-propanol, and n-butanol.

[0016] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the molar ratio of the noble metal catalyst to the monohydric alcohol or ether is 1:100 - 1:2000.

[0017] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the pressure of the hydrogen gas is 0-10 MPa.

[0018] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein the pressure of carbon monoxide is 0.2-10 MPa.

[0019] The method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction, wherein 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 180-280℃ and the stirring and heating time is 2-45h.

[0020] Beneficial effects: This invention provides a method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation reaction. Compared with the previous carbonylation methods that required 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 1 This is a flowchart of a method for preparing monocarboxylic acids from monohydric alcohols or ethers via a carbonylation 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 propionic acid. Detailed Implementation

[0025] This invention provides a method for preparing monocarboxylic acids from monohydric alcohols or ethers via a carbonylation 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.

[0026] Existing technologies for preparing carboxylic acids from alcohols or ethers must rely on organic acid solvents such as acetic acid, which leads to the following problems: high cost, large quantities of organic acid solvents are required and recycling is energy-intensive; separation is difficult, as the product carboxylic acid has similar physical properties to the organic acid solvent, requiring complex distillation / crystallization processes.

[0027] Based on this, the present invention provides a method for preparing monocarboxylic acids from monohydric alcohols or ethers via a carbonylation reaction, such as... Figure 1 As shown, it includes the following steps:

[0028] S10. Add a monohydric alcohol or ether with n carbon atoms, water, a noble metal catalyst and an iodine-containing promoter to a reaction vessel to form a reaction system, where n is an integer greater than or equal to 2, and the ether is one of diethyl ether, n-propyl ether, n-butyl ether, n-pentyl ether and propylene oxide.

[0029] 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, a monocarboxylic acid with n+1 carbon atoms is synthesized with high selectivity through a carbonylation reaction.

[0030] Compared to conventional carbonylation methods that require large amounts of organic acid solvents, the method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation provided by this invention does not require organic acid solvents. Only a small amount of water is needed as an additive. The monohydric alcohol or ether can undergo carbonylation directly by 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 a monocarboxylic acid with n+1 carbon atoms. This method does not require organic acid solvents, significantly improves the selectivity of monocarboxylic acids in a solvent-free system, results in higher purity of the target product, and simplifies the separation process. Therefore, this method has the advantages of high yield and high reaction efficiency of monocarboxylic acids and has great commercial value.

[0031] Specifically, the reaction in this invention is essentially a noble metal-catalyzed, iodine-promoted alcohol / ether carbonylation reaction, with the key steps as follows (taking a monohydric alcohol R-OH as the raw material and HI as an iodine-containing promoter as an example):

[0032] First, the iodination activation reaction occurs: the monohydric alcohol (R–OH) reacts with an iodine-containing accelerator (HI) to produce an alkyl iodide (R–I): R OH + HI → R I + H₂O;

[0033] Then an oxidative addition reaction occurs: that is, the alkyl iodine reacts with a low-valence active metal catalyst species (usually denoted as [M]). - For example, [Rh(CO)2I2] - Or [Ir(CO)2I2] - An oxidative addition reaction occurs. The metal center is oxidized, the Cl bond breaks, and an alkyl metal complex and an iodide ion are formed: [M] - + RI → R-[M]-I;

[0034] Then a carbonylation reaction occurs: carbon monoxide (CO) coordinates and inserts between the metal-alkyl bonds (MC), which is a key step in carbon chain growth: R-[M]-I + CO → RC(O)-[M]-I;

[0035] Finally, hydrolysis produces an acid and regenerated HI: water molecules nucleophilically attack the carbonyl carbon in the acyl metal complex, reacting to produce the final product carboxylic acid (R-COOH) and a hydrogen-containing metal iodide species (usually denoted as [HMI]): RC(O)-[M]-I + H2O → R-COOH + [HMI]

[0036] The resulting carboxylic acid is R-COOH, and its carbon chain length is the number of carbons in the R- group + 1 (the carbon from CO). For example: ethanol (CH3CH2OH, n=2) → iodoethane (CH3CH2I) → CO insertion → propionyl complex (CH3CH2C(O)-[M]-I) → propionic acid (CH3CH2COOH, n+1=3)

[0037] The generated [HMI] species is unstable and reacts rapidly with CO to regenerate the active low-valent metal catalyst [M]. - It releases hydroiodic acid (HI), which then returns to the initial step to convert more alcohols into alkyl iodides (RI), completing the entire catalytic cycle.

[0038] Taking diethyl ether as an example, its reaction process is explained as follows:

[0039] Diethyl ether needs to be activated (cracked) into a species (alcohol) that can react with iodine before it can enter the catalytic cycle similar to that of a monohydric alcohol.

[0040] Symmetrical ethers (RORs, such as diethyl ether CH3CH2OCH2CH3): Under acidic and iodine-containing conditions, ethers can undergo SN2 nucleophilic substitution or acid-catalyzed cleavage. Main pathway: Reaction with HI, cleavage to produce two molecules of alcohol, i.e., OR + 2HI → 2 ROH + 2I. - .

[0041] The resulting alcohol (ROH) can be iodinated to RI by HI via the mechanism described above, and then enter the carbonylation cycle. For example, diethyl ether (CH3CH2OCH2CH3, total C 4) → two molecules of propionic acid (CH3CH2COOH, total C 6 = 4 + 2*1). For diethyl ether (n=4), its "effective n" is generally considered to be 2 (i.e., each -OC2H5 unit), and the product is propionic acid with n+1=3 units.

[0042] 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.

[0043] In some embodiments, the noble metal catalyst is a rhodium salt catalyst or an iridium salt catalyst, wherein the rhodium salt catalyst is RhI3, Rh(acac)(CO)2, or Rh[Cl(CO)]. 2, The catalyst is one of [RhCl(COD)]2 and RhCl3, but not limited thereto; the iridium salt catalyst is one of IrCl3 and IrI3, but not limited thereto.

[0044] In some embodiments, the iodine-containing accelerator is one of iodine, organic iodine, and hydroiodic acid aqueous solution, and the molar ratio of iodine in the iodine-containing accelerator to the noble metal in the noble metal catalyst is 0.1:1-10:1, but is not limited thereto.

[0045] In some embodiments, the monohydric alcohol is one of ethanol, n-propanol, and n-butanol, but is not limited thereto.

[0046] In some embodiments, the molar ratio of the noble metal catalyst to the monohydric alcohol or ether is 1:100 to 1:2000.

[0047] In some embodiments, the pressure of the hydrogen is 0-10 MPa, and the pressure of the carbon monoxide is 0.2-10 MPa.

[0048] 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 180-280°C and the stirring and heating time is 2-45 hours.

[0049] The present invention will be further explained and illustrated below through specific embodiments:

[0050] The general experimental methods used in the embodiments of the present invention are as follows:

[0051] 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 monohydric alcohol or ether, and water were accurately weighed and added 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.

[0052] The liquid chromatography conditions were as follows: the instrument for detecting the concentration of monocarboxylic 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).

[0053] Nuclear Magnetic Resonance (NMR): Dissolve an appropriate amount of the monocarboxylic 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 then insert the probe. Set parameters such as the 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.

[0054] The yield of monocarboxylic acids is an important indicator for measuring production capacity and quality. It is calculated as follows: Yield of monocarboxylic acids = (Actual yield of monocarboxylic acids / Theoretical yield of monocarboxylic acids) × 100%.

[0055] Example 1

[0056] 100 mmol of 95% ethanol, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding propionic acid in a yield of 72%.

[0057] The product obtained in Example 1 was 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 The liquid chromatogram of the propionic acid standard shown reveals that... Figure 2 It appears at 4.917 min. Figure 4 The chromatographic peaks were completely identical to those of the standard, and the peaks were symmetrical and free of impurities. According to the principle of qualitative analysis by liquid chromatography, the retention times were consistent, indicating that the product of Example 1 contained the same compound as the propionic acid standard.

[0058] The 1H NMR spectrum reflects the chemical environment of hydrogen atoms in a molecule through chemical shifts (δ values) and peak shapes. The typical 1H NMR characteristics of propionic acid (CH3CH2COOH) are as follows: -COOH (carboxylic acid hydrogen): the chemical shift is usually in the range of 10-13 ppm, and it is a broad peak due to intermolecular hydrogen bonding; -CH2- (methylene hydrogen): affected by the electron-withdrawing effect of carboxylic acid, the chemical shift is in the range of 2.3-2.5 ppm, and it is a triplet (coupling of adjacent -CH3); -CH3 (methyl hydrogen): the chemical shift is in the range of 1.0-1.3 ppm, and it is a quartet (coupling of adjacent -CH2-).

[0059] from Figure 3 As can be seen, the product in Example 1 exhibits a broad peak at δ≈11.8 ppm, corresponding to the carboxylic acid hydrogen of **-COOH**, consistent with propionic acid characteristics; a triplet at δ≈2.4 ppm, corresponding to the methylene hydrogen of **-CH2-**, consistent with the structure of propionic acid; and a quartet at δ≈1.1 ppm, corresponding to the methyl hydrogen of **-CH3**, also consistent with the structure of propionic acid. Therefore, Figure 3 The chemical shift and peak shape of the 1H NMR spectrum perfectly match the molecular structure of propionic acid, further confirming that the product of this embodiment is propionic acid, and the absence of obvious impurity peaks indicates that the product has high purity.

[0060] Example 2

[0061] 100 mmol of 95% ethanol, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 1.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 1 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 200 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding a propionic acid yield of 46%.

[0062] Example 3

[0063] 100 mmol of 95% ethanol, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 1.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 3 MPa and carbon monoxide at 3 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding propionic acid in a yield of 35%.

[0064] Example 4

[0065] 100 mmol of 95% ethanol, 0.1 mmol of RhI3, 1.2 mmol of elemental iodine, and 1.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 1 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding a propionic acid yield of 54%.

[0066] Example 5

[0067] 100 mmol of 95% ethanol, 0.1 mmol of IrCl3, 1.2 mmol of elemental iodine, and 1.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 1 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was brought to a final volume, filtered, and used for subsequent analysis, yielding propionic acid in a yield of 56%.

[0068] Example 6

[0069] 100 mmol of 95% n-propanol, 0.1 mmol of IrCl3, 1.2 mmol of hydroiodic acid aqueous solution, and 1.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was completed, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding butyric acid in a yield of 63%.

[0070] Example 7

[0071] 100 mmol of diethyl ether, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding propionic acid in a yield of 71%.

[0072] Example 8

[0073] A 50 ml reactor was purged with 100 mmol of ethylene oxide gas, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 1.0 ml of water, then the reactor was sealed. Hydrogen gas at 1 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to volume, filtered, and used for subsequent analysis, yielding a propionic acid yield of 66%.

[0074] Example 9

[0075] 100 mmol of n-propyl ether, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 16 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding butyric acid in a yield of 56%.

[0076] Example 10

[0077] 100 mmol of n-butyl ether, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding valeric acid in a yield of 68%.

[0078] Example 11

[0079] 100 mmol of n-pentyl ether, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding hexanoic acid in a yield of 63%.

[0080] Comparative Example 1

[0081] 100 mmol of 95% ethanol, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water were added to a 50 ml reaction vessel, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reaction vessel was heated to 150 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding a propionic acid yield of 5%.

[0082] Comparative Example 2

[0083] 100 mmol of diethyl ether, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of LiI, and 2.0 ml of water were added to a 50 ml reactor, which was then sealed. Hydrogen gas at 2 MPa and carbon monoxide at 4 MPa were introduced, and the reactor was heated to 180 °C and stirred for 20 h. After the reaction was complete, the reaction solution was diluted to a final volume, filtered, and used for subsequent analysis, yielding a propionic acid yield of 7%.

[0084] Comparing the data from Example 1 and Comparative Example 1 reveals that when the reactor temperature is 150°C (below 180°C), the yield of the target product, propionic acid, is extremely low, indicating that the catalyst has low catalytic activity under these temperature conditions and cannot effectively catalyze the formation of propionic acid. Comparing the data from Example 7 and Comparative Example 2 shows that when LiI is used as an iodine-containing promoter, the yield of the target product, propionic acid, is also extremely low, indicating that LiI is not suitable as a promoter for the preparation of monocarboxylic acids from monohydric alcohols or ethers in systems without organic acid solvents.

[0085] In summary, the method for preparing monocarboxylic acids from monohydric alcohols or ethers via carbonylation provided by this invention does not require organic acid solvents. The monohydric alcohols or ethers can undergo carbonylation directly upon heating in a mixed atmosphere of carbon monoxide and hydrogen, under the action of a noble metal catalyst and an iodine-containing promoter, thereby generating a monocarboxylic acid with n+1 carbon atoms. This method does not require organic acid solvents, and the selectivity of monocarboxylic 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 yield and high reaction efficiency of monocarboxylic acids, and has great commercial value.

[0086] 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 monocarboxylic acids from monohydric alcohols via a carbonylation reaction, characterized in that, Add 100 mmol of 95% ethanol, 0.1 mmol of RhCl3·3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 2 MPa hydrogen and 4 MPa carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, propionic acid was obtained.

2. A method for preparing monocarboxylic acids from monohydric alcohols via a carbonylation reaction, characterized in that, Add 100 mmol of 95% ethanol, 0.1 mmol of RhI3, 1.2 mmol of elemental iodine, and 1.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 1 MPa of hydrogen and 4 MPa of carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, propionic acid was obtained.

3. A method for preparing monocarboxylic acids from monohydric alcohols via a carbonylation reaction, characterized in that, Add 100 mmol of 95% ethanol, 0.1 mmol of IrCl3, 1.2 mmol of elemental iodine, and 1.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 1 MPa of hydrogen and 4 MPa of carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, propionic acid was obtained.

4. A method for preparing monocarboxylic acids from monohydric alcohols via a carbonylation reaction, characterized in that, Add 100 mmol of 95% n-propanol, 0.1 mmol of IrCl3, 1.2 mmol of hydroiodic acid aqueous solution, and 1.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 2 MPa of hydrogen and 4 MPa of carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, butyric acid was obtained.

5. A method for preparing monocarboxylic acids from ethers via a carbonylation reaction, characterized in that, Add 100 mmol of diethyl ether, 0.1 mmol of RhCl3 · 3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 2 MPa hydrogen and 4 MPa carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, propionic acid was obtained.

6. A method for preparing monocarboxylic acids from ethers via a carbonylation reaction, characterized in that, The reactor was filled with 100 mmol of ethylene oxide gas, 0.1 mmol of RhCl3 · 3H2O, 1.2 mmol of elemental iodine, and 1.0 ml of water, and then the reactor was sealed. By introducing 1 MPa of hydrogen and 4 MPa of carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, propionic acid was obtained.

7. A method for preparing monocarboxylic acids from ethers via a carbonylation reaction, characterized in that, Add 100 mmol of n-propyl ether, 0.1 mmol of RhCl3 · 3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 2 MPa hydrogen and 4 MPa carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 16 hours, butyric acid was obtained.

8. A method for preparing monocarboxylic acids from ethers via a carbonylation reaction, characterized in that, Add 100 mmol of n-butyl ether, 0.1 mmol of RhCl3 · 3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 2 MPa of hydrogen and 4 MPa of carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, valeric acid was obtained.

9. A method for preparing monocarboxylic acids from ethers via a carbonylation reaction, characterized in that, Add 100 mmol of n-pentyl ether, 0.1 mmol of RhCl3 · 3H2O, 1.2 mmol of elemental iodine, and 2.0 ml of water to a 50 ml reaction vessel, then seal the reaction vessel. By introducing 2 MPa of hydrogen and 4 MPa of carbon monoxide, heating the reactor to 180°C, and stirring the reaction for 20 hours, hexanoic acid was obtained.

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