A method for preparing vanillin by catalytic oxidation of vanillyl alcohol
By regulating the catalyst performance through the ionic liquid reaction system and inhibiting the peroxidation side reaction, highly selective and efficient preparation of vanillin at low temperature and normal pressure is achieved, solving the problems of low selectivity and harsh conditions in the preparation of vanillin from vanillin alcohol in the existing technology, and achieving a green and environmentally friendly catalytic oxidation effect.
Patent Information
- Application Number
- CN202311398645.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-26
- Publication Date
- 2025-09-19
- Estimated Expiration
- 2043-10-26
AI Technical Summary
In the prior art, the peroxidation side reaction in the preparation of vanillin from vanillyl alcohol is serious, resulting in low vanillin selectivity, and the conventional oxidation reaction conditions are harsh.
An ionic liquid reaction system is used to influence the catalytic performance of the catalyst by regulating the structure of the ionic liquid, inhibit the peroxidation side reaction, and catalytically oxidize vanillin to produce vanillin in a one-step process at low temperature and normal pressure. The ionic liquid is used as the reaction solvent, combined with a specific catalyst and hydrogen peroxide for the reaction.
The selectivity and yield of vanillin are improved, the operating conditions are mild, it conforms to the concept of green process engineering, the catalytic activity is high, and it is environmentally friendly.
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing vanillin by catalytic oxidation of vanillyl alcohol, and belongs to the technical field of biomass. Background Art
[0002] Vanillin, also known as 4-hydroxy-3-methoxybenzaldehyde, is a widely used, high-value-added industrial chemical. It is used in the food industry as a flavoring, the cosmetics industry as a fragrance, and the pharmaceutical industry as an odor masking agent. It is also an intermediate in the synthesis of various pharmaceuticals, such as L-dopa, methyldopa, and papaverine. Vanillin can be directly extracted from vanilla beans, but the difficulty of growing vanilla beans limits the production of natural vanillin. Therefore, most industries use petrochemical raw materials to artificially synthesize vanillin. However, petrochemical resources are non-renewable, and finding renewable raw materials to produce vanillin is of great significance for its industrial production.
[0003] Vanillyl alcohol is an important lignin derivative that can be obtained through lignin depolymerization, making it renewable and inexpensive. Vanillin can be produced by converting vanillyl alcohol to a product called vanillin using hydrogen peroxide. However, existing processes often suffer from peroxidation side reactions, leading to the formation of vanillic acid, a peroxidation byproduct, resulting in low selectivity for the target vanillin. For example, Valange et al. (UltrasonSonochem, 2017, 36, 27-35) used cobalt-containing spinel in catalytic oxidation experiments. Due to peroxidation and other side reactions, the vanillin yield was only 7% and the selectivity was only 23%. Lin et al. (Chemical Papers, 2018, 72, 2315-2325) used Cr- and Fe-containing MOFs to catalyze the hydrogen peroxide oxidation of vanillyl alcohol, producing a mixture of vanillin, vanillic acid, and guaiacol. The maximum vanillin yield did not exceed 40%. Therefore, inhibiting peroxidation side reactions during the vanillin production process is of significant research significance for promoting the development of vanillin production processes from vanillyl alcohol.
[0004] Targeting this research direction, the present invention has developed an ionic liquid reaction system. By manipulating the ionic liquid structure to influence the catalytic performance of the catalyst, the present invention suppresses peroxidation side reactions and improves vanillin product selectivity. Furthermore, the present invention enables the production of vanillin through a single-step catalytic oxidation of vanillyl alcohol at relatively low temperatures and atmospheric pressure. This process, characterized by mild operating conditions, high catalytic activity, and environmental friendliness, aligns with the principles of green process engineering. Summary of the Invention
[0005] The object of the present invention is to provide a method for preparing vanillin by catalytic oxidation of vanillyl alcohol with high selectivity, environmental friendliness, high catalytic activity and mild conditions.
[0006] The technical solution adopted by the present invention is: a method for preparing vanillin by catalytic oxidation of vanillyl alcohol, wherein an ionic liquid is used as a reaction solvent, vanillyl alcohol, acetic acid, a catalyst and hydrogen peroxide are added to the ionic liquid and heated with stirring under certain temperature and time conditions, after the reaction is completed, the reaction is cooled to room temperature, deionized water is added, and a certain amount of ethyl acetate is added to the system for extraction to obtain vanillin.
[0007] Furthermore, the ionic liquid is one or a combination of triethylamine acetate, triethylamine phosphate, triethylamine sulfate, and triethylamine hydrochloride.
[0008] Furthermore, the concentration of the hydrogen peroxide is 30 wt.%.
[0009] Furthermore, the catalyst is one or more of cobalt sulfate, copper sulfate, ferrous sulfate, manganese sulfate, nickel sulfate, cerium sulfate, and ferric sulfate.
[0010] Furthermore, in the catalytic oxidation experiment, the mass ratio of vanillyl alcohol: ionic liquid: acetic acid: catalyst: hydrogen peroxide = 100 mg: 5-10 mL: 5-10 mL: 12-18 mg: 0.6-1.8 mL.
[0011] Furthermore, the heating and stirring temperature in the catalytic oxidation experiment is 40 to 120° C., and the time is 2 to 10 h.
[0012] The beneficial effects of the present invention are:
[0013] 1. To address the problem of peroxidation side reactions, the present invention adopts an ionic liquid reaction system to change the catalytic performance of the catalyst, inhibit the peroxidation reaction, and improve the selectivity of the vanillin product.
[0014] 2. In response to the problem of harsh conditions in conventional oxidation reactions, the present invention adopts a low vapor pressure ionic liquid reaction system, which allows the reaction to be completed at a lower temperature and normal pressure. The operating conditions are mild, the catalytic activity is high, and it is green and environmentally friendly, in line with the concept of green process engineering. DETAILED DESCRIPTION
[0015] For a better understanding of the present invention, the present invention is further described below with reference to examples, but the embodiments of the present invention are not limited thereto.
[0016] Example 1
[0017] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 6 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 90.2% and a vanillin yield of 8.75%.
[0018] Example 2
[0019] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 80°C for 6 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 86.11% and a vanillin yield of 7.16%.
[0020] Example 3
[0021] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 4 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 85.71% and a vanillin yield of 6.97%.
[0022] Example 4
[0023] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer, heated and stirred at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product, and the supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 81.65% and a vanillin yield of 11.85%.
[0024] Example 5
[0025] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 18 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 78.21% and a vanillin yield of 5.07%.
[0026] Example 6
[0027] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of catalyst manganese sulfate, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 71.59% and a vanillin yield of 10.35%.
[0028] Example 7
[0029] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of nickel sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 70.9% and a vanillin yield of 4.5%.
[0030] Example 8
[0031] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of copper sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 79.9% and a vanillin yield of 3.99%.
[0032] Example 9
[0033] 100 mg of vanillyl alcohol, 5 mL of triethylamine phosphate, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 83.8% and a vanillin yield of 4.2%.
[0034] Example 10
[0035] 100 mg of vanillyl alcohol, 5 mL of triethylamine hydrochloride, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer. The mixture was heated and stirred at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 65.56% and a vanillin yield of 4.35%.
[0036] Example 11
[0037] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.8 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer, heated and stirred at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product, and the supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 83.87% and a vanillin yield of 3.76%.
[0038] Example 12
[0039] 100 mg of vanillyl alcohol, 5 mL of triethylamine acetate, 5 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 0.6 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 81.01% and a vanillin yield of 3.14%.
[0040] Comparative Example 1
[0041] 100 mg of vanillyl alcohol, 10 mL of triethylamine acetate, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 83.42% and a vanillin yield of 2.36%.
[0042] Comparative Example 2
[0043] 100 mg of vanillyl alcohol, 10 mL of acetic acid, 12 mg of cobalt sulfate catalyst, and 1.2 mL of hydrogen peroxide (30 wt.%) were added to a reaction flask equipped with a reflux condenser and a magnetic stirrer and heated with stirring at 60°C for 2 hours. After the reaction, the resulting mixture was mixed with deionized water in a 1:2 ratio. 10 mL of ethyl acetate was added to the system to extract the product. The supernatant was collected for qualitative and quantitative analysis by gas chromatography (GC). The analysis results showed a vanillyl alcohol conversion rate of 86.11% and a vanillin yield of 2.53%.
[0044] In summary, Example 4 achieved the highest vanillin conversion rate of 81.65%, and the vanillin yield of 11.85%. This is because, on the one hand, the ionic liquid anion coordinates with the metal ion, regulating its catalytic hydrogen peroxide oxidation activity, and on the other hand, the proton released by acetic acid polarizes the reactant vanillin hydroxyl group, promoting its nucleophilic attack and oxidation reaction. Under the above synergistic effect, Example 4 achieved the highest reaction efficiency. Comparative Example 1 did not add acetic acid, and the reaction efficiency was lower. This is because the lack of proton activation and the low activity of the reactant. Comparative Example 2 did not add ionic liquid, and the reaction efficiency was lower. This is because the lack of ionic liquid coordination on the catalytic center, that is, the lack of the ionic liquid's regulatory effect on the catalytic activity, resulting in the occurrence of side reactions such as peroxidation, which reduces the reaction efficiency.
[0045] The above is an exemplary description of the present invention. Without departing from the core of the present invention, any simple deformation, modification, substitution, combination, and simplification are equivalent replacement methods and are included in the scope of protection of the present invention.
Claims
1. A method for preparing vanillin by catalytic oxidation of vanillyl alcohol, characterized in that: Ionic liquid is used as the reaction solvent. Vanillyl alcohol, acetic acid, a catalyst, and hydrogen peroxide are added to the ionic liquid and heated with stirring under certain temperature and time conditions. After the reaction is completed, the mixture is cooled to room temperature, deionized water is added, and a certain amount of ethyl acetate is added to the system for extraction to obtain vanillin. The ionic liquid is one or a combination of triethylamine acetate, triethylamine phosphate, triethylamine sulfate, and triethylamine hydrochloride; The catalyst is one or more of cobalt sulfate, copper sulfate, ferrous sulfate, manganese sulfate, nickel sulfate, cerium sulfate and ferric sulfate.
2. The method for preparing vanillin by catalytic oxidation of vanillyl alcohol according to claim 1, characterized in that: The concentration of hydrogen peroxide was 30 wt.%.
3. The method for preparing vanillin by catalytic oxidation of vanillyl alcohol according to claim 1, characterized in that: By mass ratio, vanillyl alcohol: ionic liquid: acetic acid: catalyst: hydrogen peroxide = 100 mg: 5-10 mL: 5-10 mL: 12-18 mg: 0.6-1.8 mL.
4. The method for preparing vanillin by catalytic oxidation of vanillyl alcohol according to claim 1, characterized in that: The heating and stirring temperature is 40 to 120°C and the time is 2 to 10 hours.