A method for synthesizing ethyl vanillin

Abstract

This invention provides a method for synthesizing ethyl vanillin, belonging to the field of efficient chemical synthesis technology. The method includes the following steps: (1) under a protective atmosphere, catechol, ethanol, and Nb₂O₅ are mixed and subjected to an etherification reaction to obtain o-ethoxyphenol; (2) under a protective atmosphere, o-ethoxyphenol, formaldehyde solution, and Mo₂C are mixed and subjected to an addition reaction to obtain 3-ethoxy-4-hydroxybenzyl alcohol; (3) 3-ethoxy-4-hydroxybenzyl alcohol, water, and MnO₂ are mixed and subjected to an oxidation reaction to obtain the ethyl vanillin. This invention employs a heterogeneous catalytic reaction process, using Nb₂O₅, Mo₂C, and MnO₂ as solid catalysts. The catalysts are easily separated and recovered from the reaction system. Furthermore, the entire process does not use highly corrosive substances such as hydrochloric acid and sodium hydroxide, nor homogeneous catalysts such as phase transfer catalysts. Compared to traditional homogeneous reaction synthesis techniques, the process is green and environmentally friendly, with excellent yield and conversion rates.

Description

Technical Field

[0001] This invention relates to the field of efficient chemical synthesis technology, and in particular to a method for synthesizing ethyl vanillin. Background Technology

[0002] Ethyl vanillin, chemically known as 3-ethoxy-4-hydroxybenzaldehyde, is a compound with a strong vanilla and sweet chocolate aroma. Because its aromatic properties are 3-4 times stronger than vanillin, it can impart a more elegant and refreshing vanilla bean aroma to food even at lower addition levels. my country's National Food Safety Standard (GB2760-2014) stipulates that ethyl vanillin can be used as a flavoring agent in candies, chocolates, condiments, soft drinks, alcoholic beverages, ice cream, and baked goods. In infant and toddler formula, the permitted dosage of ethyl vanillin is 5 mg / 100 mL. Ethyl vanillin can also be used to prepare various flavoring agents and pharmaceutical flavoring agents such as ethyl gingerone, vanillin, and cinnamaldehyde derivatives, as well as drug molecules such as L-dopamine and papaverine.

[0003] Unlike vanillin, ethyl vanillin does not exist naturally; it is synthesized chemically. Currently, two main industrial synthesis techniques are used. One technique uses o-ethoxyphenol and glyoxylic acid as raw materials, which undergo a condensation reaction in the presence of sodium hydroxide to produce 3-ethoxy-4-hydroxymandelate. This is then neutralized with dilute acid, followed by oxidation with an oxidant at high temperature and hydrolysis and decarboxylation under acidic conditions. The other technique uses o-ethoxyphenol, nitroso-N,N-dimethylaniline, and hexamethylenetetramine as raw materials, which produce ethyl vanillin and a Schiff base in the presence of hydrochloric acid. The Schiff base can then be hydrolyzed to regenerate ethyl vanillin. However, these techniques use expensive raw materials, have long process routes, and result in low yields of the target product. Furthermore, the synthesis process uses many inorganic acids and bases such as hydrochloric acid and sodium hydroxide, generating large amounts of wastewater, all of which contribute to poor economic viability.

[0004] Therefore, how to overcome the above-mentioned technical problems, use readily available and inexpensive industrial chemicals as raw materials, adopt efficient catalytic reaction technology, avoid the use of large amounts of inorganic acids and bases, and obtain ethyl vanillin products in high yield is a problem that needs to be solved at present. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing ethyl vanillin, which solves the technical problems of expensive raw materials, large amount of waste liquid, large use of inorganic acids and bases, and low reaction efficiency in the existing ethyl vanillin synthesis methods.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for synthesizing ethyl vanillin, comprising the following steps:

[0008] (1) Under a protective atmosphere, catechol, ethanol and Nb2O5 are mixed and subjected to an etherification reaction to obtain o-ethoxyphenol; (2) Under a protective atmosphere, o-ethoxyphenol, formaldehyde solution and Mo2C are mixed and subjected to an addition reaction to obtain 3-ethoxy-4-hydroxybenzyl alcohol; (3) 3-ethoxy-4-hydroxybenzyl alcohol, water and MnO2 are mixed and subjected to an oxidation reaction to obtain the ethyl vanillin.

[0009] Preferably, the molar ratio of catechol to ethanol in step (1) is 1:2 to 20;

[0010] The mass ratio of catechol to Nb2O5 is 10 to 100:1.

[0011] Preferably, the temperature of the etherification reaction in step (1) is 250-350°C and the time of the etherification reaction is 1-6 hours.

[0012] Preferably, the formaldehyde solution in step (2) has a mass concentration of 5-25%;

[0013] The molar ratio of o-ethoxyphenol to formaldehyde is 1:1.5 to 5, and the mass ratio of o-ethoxyphenol to Mo2C is 5 to 20:1.

[0014] Preferably, the temperature of the addition reaction in step (2) is 200-300°C and the time of the addition reaction is 2-12 hours.

[0015] Preferably, the molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol and water in step (3) is 1:20 to 200, and the mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol and MnO2 is 10 to 100:1.

[0016] Preferably, the initial oxygen pressure of the oxidation reaction in step (3) is 0.5 to 5.0 MPa.

[0017] Preferably, the oxidation reaction in step (3) is carried out at a temperature of 120–240°C for 1–6 hours.

[0018] The present invention has the following beneficial effects:

[0019] This invention provides a method for synthesizing ethyl vanillin, comprising the following steps: (1) under a protective atmosphere, a mixture of catechol, ethanol, and Nb2O5 is subjected to an etherification reaction to obtain o-ethoxyphenol; (2) under a protective atmosphere, a mixture of o-ethoxyphenol, formaldehyde solution, and Mo2C is subjected to an addition reaction to obtain 3-ethoxy-4-hydroxybenzyl alcohol; (3) a mixture of 3-ethoxy-4-hydroxybenzyl alcohol, water, and MnO2 is subjected to an oxidation reaction to obtain the ethyl vanillin. This invention uses inexpensive catechol, ethanol, formaldehyde, and oxygen as raw materials, and the process does not consume expensive fine organic chemicals, greatly reducing the production cost of ethyl vanillin.

[0020] This invention employs heterogeneous catalytic reaction processes, using Nb2O5, Mo2C, and MnO2 as solid catalysts. The catalysts are easily separated and recovered from the reaction system. Furthermore, the entire process does not use highly corrosive substances such as hydrochloric acid and sodium hydroxide, nor homogeneous catalysts such as phase transfer catalysts. Compared to traditional homogeneous reaction synthesis technologies, the process is green and environmentally friendly, with excellent yield and conversion rates. Attached Figure Description

[0021] Figure 1 A simplified flowchart of the synthesis method of ethyl vanillin provided by the present invention. Detailed Implementation

[0022] This invention provides a method for synthesizing ethyl vanillin, comprising the following steps:

[0023] (1) Under a protective atmosphere, catechol, ethanol and Nb2O5 are mixed and subjected to an etherification reaction to obtain o-ethoxyphenol;

[0024] (2) Under a protective atmosphere, o-ethoxyphenol, formaldehyde solution and Mo2C are mixed and subjected to an addition reaction to obtain 3-ethoxy-4-hydroxybenzyl alcohol;

[0025] (3) The ethyl vanillin is obtained by mixing 3-ethoxy-4-hydroxybenzyl alcohol, water and MnO2 and carrying out an oxidation reaction.

[0026] A simplified flowchart of the method for synthesizing ethyl vanillin provided by this invention is shown below. Figure 1 As shown.

[0027] In this invention, the protective atmosphere in step (1) is preferably nitrogen.

[0028] In this invention, the molar ratio of catechol to ethanol in step (1) is preferably 1:2 to 20, more preferably 1:5 to 15, and even more preferably 1:8 to 12. The mass ratio of catechol to Nb2O5 is preferably 10 to 100:1, more preferably 30 to 80:1, and even more preferably 50 to 60:1.

[0029] In this invention, the temperature of the etherification reaction in step (1) is preferably 250-350°C, more preferably 280-320°C, and even more preferably 290-310°C. The time of the etherification reaction is preferably 1-6 hours, more preferably 2-5 hours, and even more preferably 3-4 hours.

[0030] After the etherification reaction in step (1) is completed, the system is sequentially cooled, filtered, and rotary evaporated to obtain o-ethoxyphenol. The target cooling temperature is preferably 20-30°C, more preferably 22-28°C, and even more preferably 24-26°C. The purpose of filtration is to remove Nb2O5, and the purpose of rotary evaporation is to remove ethanol.

[0031] In this invention, the protective atmosphere in step (2) is preferably nitrogen.

[0032] In this invention, the mass concentration of the formaldehyde solution in step (2) is preferably 5-25%, more preferably 10-20%, and even more preferably 12-18%. The molar ratio of o-ethoxyphenol to formaldehyde is preferably 1:1.5-5, more preferably 1:2-4.5, and even more preferably 1:2.5-4. The mass ratio of o-ethoxyphenol to Mo2C is preferably 5-20:1, more preferably 10-15:1, and even more preferably 12-13:1.

[0033] In this invention, the temperature of the addition reaction in step (2) is preferably 200-300°C, more preferably 220-280°C, and even more preferably 240-260°C. The time of the addition reaction is preferably 2-12 hours, more preferably 4-10 hours, and even more preferably 6-8 hours.

[0034] After the addition reaction in step (2) is completed, the system is sequentially cooled, filtered, and rotary evaporated to obtain 3-ethoxy-4-hydroxybenzyl alcohol. The target cooling temperature is preferably 20-30°C, more preferably 22-28°C, and even more preferably 24-26°C. The purpose of filtration is to remove Mo2C, and the purpose of rotary evaporation is to remove formaldehyde solution.

[0035] In this invention, the molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol and water in step (3) is preferably 1:20 to 200, more preferably 1:70 to 150, and even more preferably 1:100 to 120. The mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol and MnO2 is preferably 10 to 100:1, more preferably 40 to 70:1, and even more preferably 50 to 60:1.

[0036] In this invention, the initial oxygen pressure of the oxidation reaction in step (3) is preferably 0.5 to 5.0 MPa, more preferably 2 to 3.5 MPa, and even more preferably 2.5 to 3 MPa.

[0037] In this invention, the temperature of the oxidation reaction in step (3) is preferably 120-240°C, more preferably 150-210°C, and even more preferably 170-190°C. The time of the oxidation reaction is preferably 1-6 hours, more preferably 2-5 hours, and even more preferably 3-4 hours.

[0038] After the oxidation reaction in step (3) is completed, the system is sequentially cooled, filtered, and rotary evaporated to obtain ethyl vanillin. The target temperature for cooling is preferably 20-30°C, more preferably 22-28°C, and even more preferably 24-26°C. The purpose of filtration is to remove MnO2, and the purpose of rotary evaporation is to remove water.

[0039] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.

[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] Catechol, ethanol, and Nb2O5 were mixed (the molar ratio of cadmium to ethanol was 1:10, and the mass ratio of cadmium to Nb2O5 was 30:1) and placed in a sealed reactor. The oxygen in the reactor was purged with nitrogen. The reactor was then heated to 280°C for etherification reaction for 4 hours. Afterward, the reactor was cooled to 25°C, and solid Nb2O5 was removed by filtration. Ethanol was removed by rotary evaporation to obtain o-ethoxyphenol.

[0043] o-ethoxyphenol, a 10% formaldehyde solution, and Mo2C were mixed (the molar ratio of o-ethoxyphenol to formaldehyde was 1:1.5, and the mass ratio of o-ethoxyphenol to Mo2C was 5:1). The mixture was placed in a sealed reactor, and the oxygen in the reactor was purged with nitrogen. The reactor was then heated to 240°C and the addition reaction was carried out for 10 hours. After that, the reactor was cooled to 25°C, the solid Mo2C was removed by filtration, and the solvent was removed by rotary evaporation to obtain 3-ethoxy-4-hydroxybenzyl alcohol.

[0044] 3-Ethoxy-4-hydroxybenzyl alcohol and MnO2 were mixed (the mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol to MnO2 was 40:1), dissolved in water (the molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol to water was 1:140), and placed in a sealed reaction vessel. Oxygen was introduced into the reaction vessel at 25°C, and the pressure was maintained at 1.5 MPa. Then the reaction vessel was raised to 200°C and the oxidation reaction was carried out for 3 hours. After that, the reaction vessel was lowered to 25°C, the solid MnO2 was removed by filtration, and the water was removed by rotary evaporation to obtain ethyl vanillin.

[0045] Example 2

[0046] Catechol, ethanol, and Nb2O5 were mixed (the molar ratio of cadmium to ethanol was 1:5, and the mass ratio of cadmium to Nb2O5 was 20:1) and placed in a sealed reactor. The oxygen in the reactor was purged with nitrogen. The reactor was then heated to 300°C for etherification reaction for 3 hours. Afterward, the reactor was cooled to 25°C, and solid Nb2O5 was removed by filtration. Ethanol was removed by rotary evaporation to obtain o-ethoxyphenol.

[0047] o-Ethoxyphenol, a 15% formaldehyde solution, and Mo2C were mixed (the molar ratio of o-ethoxyphenol to formaldehyde was 1:2.5, and the mass ratio of o-ethoxyphenol to Mo2C was 15:1). The mixture was placed in a sealed reactor, and the oxygen in the reactor was purged with nitrogen. The reactor was then heated to 260°C and the addition reaction was carried out for 4 hours. After that, the reactor was cooled to 25°C, the solid Mo2C was removed by filtration, and the solvent was removed by rotary evaporation to obtain 3-ethoxy-4-hydroxybenzyl alcohol.

[0048] 3-Ethoxy-4-hydroxybenzyl alcohol and MnO2 were mixed (the mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol to MnO2 was 20:1), dissolved in water (the molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol to water was 1:200), and placed in a sealed reaction vessel. Oxygen was introduced into the reaction vessel at 25°C, and the pressure was maintained at 5.0 MPa. Then the reaction vessel was raised to 120°C and the oxidation reaction was carried out for 6 hours. After that, the reaction vessel was lowered to 25°C, the solid MnO2 was removed by filtration, and the water was removed by rotary evaporation to obtain ethyl vanillin.

[0049] Example 3

[0050] Catechol, ethanol, and Nb2O5 were mixed (the molar ratio of cadmium to ethanol was 1:2, and the mass ratio of cadmium to Nb2O5 was 50:1) and placed in a sealed reactor. The oxygen in the reactor was purged with nitrogen. The reactor was then heated to 340°C for etherification reaction for 2 hours. Afterward, the reactor was cooled to 25°C, and solid Nb2O5 was removed by filtration. Ethanol was removed by rotary evaporation to obtain o-ethoxyphenol.

[0051] o-ethoxyphenol, a 5% formaldehyde solution, and Mo2C were mixed (the molar ratio of o-ethoxyphenol to formaldehyde was 1:3, and the mass ratio of o-ethoxyphenol to Mo2C was 10:1). The mixture was placed in a sealed reactor, and the oxygen in the reactor was purged with nitrogen. The reactor was then heated to 300°C and the addition reaction was carried out for 2 hours. After that, the reactor was cooled to 25°C, the solid Mo2C was removed by filtration, and the solvent was removed by rotary evaporation to obtain 3-ethoxy-4-hydroxybenzyl alcohol.

[0052] 3-Ethoxy-4-hydroxybenzyl alcohol and MnO2 were mixed (the mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol to MnO2 was 10:1), dissolved in water (the molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol to water was 1:100), and placed in a sealed reaction vessel. Oxygen was introduced into the reaction vessel at 25°C, and the pressure was maintained at 3.0 MPa. Then the reaction vessel was raised to 160°C and the oxidation reaction was carried out for 5 hours. After that, the reaction vessel was lowered to 25°C, the solid MnO2 was removed by filtration, and the water was removed by rotary evaporation to obtain ethyl vanillin.

[0053] Example 4

[0054] Catechol, ethanol, and Nb2O5 were mixed (the molar ratio of cadmium to ethanol was 1:20, and the mass ratio of cadmium to Nb2O5 was 80:1) and placed in a sealed reactor. The oxygen in the reactor was purged with nitrogen. The reactor was then heated to 250°C for etherification reaction for 6 hours. Afterward, the reactor was cooled to 25°C, and solid Nb2O5 was removed by filtration. Ethanol was removed by rotary evaporation to obtain o-ethoxyphenol.

[0055] o-ethoxyphenol, a 20% formaldehyde solution, and Mo2C were mixed (the molar ratio of o-ethoxyphenol to formaldehyde was 1:2, and the mass ratio of o-ethoxyphenol to Mo2C was 10:1). The mixture was placed in a sealed reactor, and the oxygen in the reactor was purged with nitrogen. The reactor was then heated to 280°C and the addition reaction was carried out for 6 hours. After that, the reactor was cooled to 25°C, the solid Mo2C was removed by filtration, and the solvent was removed by rotary evaporation to obtain 3-ethoxy-4-hydroxybenzyl alcohol.

[0056] 3-Ethoxy-4-hydroxybenzyl alcohol and MnO2 were mixed (mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol to MnO2 was 80:1), dissolved in water (molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol to water was 1:180), and placed in a sealed reaction vessel. Oxygen was introduced into the reaction vessel at 25°C, and the pressure was maintained at 4.0 MPa. Then the reaction vessel was raised to 220°C and the oxidation reaction was carried out for 2 hours. After that, the reaction vessel was lowered to 25°C, the solid MnO2 was removed by filtration, and the water was removed by rotary evaporation to obtain ethyl vanillin.

[0057] Example 5

[0058] Catechol, ethanol, and Nb2O5 were mixed (the molar ratio of cadmium to ethanol was 1:12, and the mass ratio of cadmium to Nb2O5 was 100:1) and placed in a sealed reactor. The oxygen in the reactor was purged with nitrogen. The reactor was then heated to 350°C for etherification reaction for 1 hour. Afterward, the reactor was cooled to 25°C, and solid Nb2O5 was removed by filtration. Ethanol was removed by rotary evaporation to obtain o-ethoxyphenol.

[0059] o-ethoxyphenol, a 25% formaldehyde solution, and Mo2C were mixed (the molar ratio of o-ethoxyphenol to formaldehyde was 1:5, and the mass ratio of o-ethoxyphenol to Mo2C was 16:1). The mixture was placed in a sealed reactor, and the oxygen in the reactor was purged with nitrogen. The reactor was then heated to 200°C and the addition reaction was carried out for 12 hours. After that, the reactor was cooled to 25°C, the solid Mo2C was removed by filtration, and the solvent was removed by rotary evaporation to obtain 3-ethoxy-4-hydroxybenzyl alcohol.

[0060] 3-Ethoxy-4-hydroxybenzyl alcohol and MnO2 were mixed (mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol to MnO2 was 100:1), dissolved in water (molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol to water was 1:20), and placed in a sealed reaction vessel. Oxygen was introduced into the reaction vessel at 25°C, and the pressure was maintained at 0.5 MPa. Then the reaction vessel was raised to 240°C and the oxidation reaction was carried out for 1 hour. After that, the reaction vessel was lowered to 25°C, the solid MnO2 was removed by filtration, and the water was removed by rotary evaporation to obtain ethyl vanillin.

[0061] Example 6

[0062] Catechol, ethanol, and Nb2O5 were mixed (the molar ratio of cadmium to ethanol was 1:15, and the mass ratio of cadmium to Nb2O5 was 10:1) and placed in a sealed reactor. The oxygen in the reactor was purged with nitrogen. The reactor was then heated to 320°C for etherification reaction for 5 hours. After that, the reactor was cooled to 25°C, and solid Nb2O5 was removed by filtration. Ethanol was removed by rotary evaporation to obtain o-ethoxyphenol.

[0063] o-Ethoxyphenol, 18% formaldehyde solution and Mo2C were mixed (molar ratio of o-ethoxyphenol to formaldehyde was 1:4, mass ratio of o-ethoxyphenol to Mo2C was 12:1) and placed in a sealed reaction vessel. The oxygen in the reaction vessel was purged with nitrogen. The reaction vessel was then heated to 220°C and the addition reaction was carried out for 8 hours. After that, the reaction vessel was cooled to 25°C, the solid Mo2C was removed by filtration, and the solvent was removed by rotary evaporation to obtain 3-ethoxy-4-hydroxybenzyl alcohol.

[0064] 3-Ethoxy-4-hydroxybenzyl alcohol and MnO2 were mixed (the mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol to MnO2 was 60:1), dissolved in water (the molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol to water was 1:80), and placed in a sealed reaction vessel. Oxygen was introduced into the reaction vessel at 25°C, and the pressure was maintained at 2.5 MPa. Then the reaction vessel was raised to 180°C and the oxidation reaction was carried out for 4 hours. After that, the reaction vessel was lowered to 25°C, the solid MnO2 was removed by filtration, and the water was removed by rotary evaporation to obtain ethyl vanillin.

[0065] The reaction activity of the formation processes of o-ethoxyphenol, 3-ethoxy-4-hydroxybenzyl alcohol, and ethyl vanillin in the reaction steps of Examples 1 to 6 was tested, as shown in Table 1.

[0066] The conversion rate of reactants and the yield of products were calculated using an Agilent Technologies 8890 gas chromatograph. Liquid products from Examples 1-6 were collected and quantitatively analyzed by gas chromatography. The injection port temperature was 25°C, the column oven temperature was 150°C for 5 minutes, then increased to 150°C at a rate of 10°C / min and held for 10 minutes. An HP-5 capillary column was used, 30 m long, 0.25 mm in diameter, with a 0.25 μm membrane. Nitrogen was used as the carrier gas, the column flow rate was 1.0 mL / min, and an FID detector was used at a temperature of 250°C. The conversion rate of raw materials is 1 - m(raw material after reaction) / m(raw material before reaction) × 100%, and the product yield is m(product) / m(raw material before reaction) × 100%, where m(raw material after reaction) and m(product) are the mass (g) of the raw material after reaction and the product (g) respectively, as quantified by gas chromatography, and m(raw material before reaction) is the mass (g) of the raw material added before the reaction.

[0067] Table 1. Activity test table for each reaction step in Examples 1-6.

[0068]

[0069] As can be seen from the above embodiments, the present invention provides a method for synthesizing ethyl vanillin, comprising the following steps: (1) under a protective atmosphere, catechol, ethanol and Nb2O5 are mixed and subjected to an etherification reaction to obtain o-ethoxyphenol; (2) under a protective atmosphere, o-ethoxyphenol, formaldehyde solution and Mo2C are mixed and subjected to an addition reaction to obtain 3-ethoxy-4-hydroxybenzyl alcohol; (3) 3-ethoxy-4-hydroxybenzyl alcohol, water and MnO2 are mixed and subjected to an oxidation reaction to obtain the ethyl vanillin. The present invention adopts a heterogeneous catalytic reaction process, using Nb2O5, Mo2C and MnO2 as solid catalysts, and the catalysts are easy to separate and recover from the reaction system; and the entire process does not use strong corrosive substances such as hydrochloric acid and sodium hydroxide, or homogeneous catalysts such as phase transfer catalysts. Compared with traditional homogeneous reaction synthesis technology, the process is green and environmentally friendly, and the yield and conversion rate are excellent.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing ethyl vanillin, characterized in that, Includes the following steps: (1) Under a protective atmosphere, catechol, ethanol and Nb2O5 are mixed and subjected to an etherification reaction to obtain o-ethoxyphenol; (2) Under a protective atmosphere, o-ethoxyphenol, formaldehyde solution and Mo2C are mixed and subjected to an addition reaction to obtain 3-ethoxy-4-hydroxybenzyl alcohol; (3) The ethyl vanillin is obtained by mixing 3-ethoxy-4-hydroxybenzyl alcohol, water and MnO2 and carrying out an oxidation reaction.

2. The method for synthesizing ethyl vanillin as described in claim 1, characterized in that, The molar ratio of catechol and ethanol in step (1) is 1:2 to 20; The mass ratio of catechol to Nb2O5 is 10 to 100:

1.

3. The method for synthesizing ethyl vanillin as described in claim 1 or 2, characterized in that, The temperature of the etherification reaction in step (1) is 250-350°C, and the time of the etherification reaction is 1-6 hours.

4. The method for synthesizing ethyl vanillin as described in claim 3, characterized in that, The formaldehyde solution in step (2) has a mass concentration of 5-25%. The molar ratio of o-ethoxyphenol to formaldehyde is 1:1.5 to 5, and the mass ratio of o-ethoxyphenol to Mo2C is 5 to 20:

1.

5. The method for synthesizing ethyl vanillin as described in claim 4, characterized in that, The temperature of the addition reaction in step (2) is 200-300℃, and the time of the addition reaction is 2-12h.

6. The method for synthesizing ethyl vanillin as described in claim 4 or 5, characterized in that, In step (3), the molar ratio of 3-ethoxy-4-hydroxybenzyl alcohol to water is 1:20 to 200, and the mass ratio of 3-ethoxy-4-hydroxybenzyl alcohol to MnO2 is 10 to 100:

1.

7. The method for synthesizing ethyl vanillin as described in claim 6, characterized in that, The initial oxygen pressure for the oxidation reaction in step (3) is 0.5 to 5.0 MPa.

8. The method for synthesizing ethyl vanillin as described in claim 7, characterized in that, The oxidation reaction in step (3) is carried out at a temperature of 120–240°C for 1–6 hours.

Images