Method for preparing p-methoxybenzaldehyde

Abstract

The present invention relates to the technical field of chemical engineering, and particularly relates to a method for preparing p-methoxybenzaldehyde. The method uses p-hydroxybenzaldehyde and dimethyl carbonate as starting materials, and prepares p-methoxybenzaldehyde by means of a methylation reaction using dimethyl carbonate in the presence of a solvent and a basic catalyst. The methylation reaction of dimethyl carbonate is carried out at a temperature of 150 °C to 160 °C in an autoclave. In the present application, the methylation reaction using dimethyl carbonate is controlled at a high temperature (150 °C to 160 °C) and is carried out in an autoclave, such that dimethyl carbonate can be mainly present in a liquid state in the reaction system at a temperature far exceeding the boiling point, thereby promoting the methylation reaction of dimethyl carbonate, and improving the purity of the prepared p-methoxybenzaldehyde final product, the yield, and the energy-efficiency.

Description

A method for producing p-methoxybenzaldehyde Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for producing p-methoxybenzaldehyde. Background Technology

[0002] p-Methoxybenzaldehyde (PMBA), also known as p-methoxybenzaldehyde or anisaldehyde, is an important fine chemical with the molecular formula C8H8O2. At room temperature, it is a colorless or pale yellow oily liquid with a persistent hawthorn aroma. It has a wide range of applications, including the development of high-value-added downstream products such as raspberry ketone; the formulation of daily-use fragrances and food flavorings, such as the main flavoring in hawthorn flower, sunflower, and lilac fragrances, and as a modifier in lily of the valley and osmanthus fragrances; an important intermediate in organic synthesis, it is an intermediate in the preparation of the antimicrobial drug hydroxycaproic acid, and also an intermediate in the synthesis of porphyrin photosensitizers; it can also be used as a fluorescent probe for the determination of biomolecules such as nucleic acids.

[0003] Currently, there are five main methods for preparing p-methoxybenzaldehyde (PMBA): plant extraction, anethole oxidation, anisole, p-methyl anisole oxidation, and p-hydroxybenzaldehyde (PHBA) methylation.

[0004] One method, plant extraction, involves adding oxidizing and decomposing agents to extracts of fennel oil, dill oil, acacia flower oil, vanilla, etc., to extract p-methoxybenzaldehyde (PMBA). However, this method is complex and has a low yield, and has been phased out.

[0005] The anethole oxidation method uses anethole as a raw material and uses an oxidant to oxidize and cleave the carbon-carbon double bond to obtain p-methoxybenzaldehyde (PHBA). However, due to the limitation of natural resources, this method is costly and is rarely used now.

[0006] The anisole process, also known as the Sommelet reaction, involves a multi-step reaction: Blanc chloro-methylation followed by a Sommelet reaction, to achieve the formylation of anisole and synthesize p-methoxybenzaldehyde. However, this method generates large amounts of acidic wastewater and causes severe equipment corrosion, making it unsuitable for industrial production.

[0007] The oxidation of p-methyl anisole can be divided into two types: chemical oxidation and electro-oxidation. Chemical oxidation uses oxygen as an oxygen source to directly synthesize p-methoxybenzaldehyde. However, this method is prone to over-oxidation, produces many byproducts, has complex separation processes, low selectivity, and uses toxic catalysts, making the process cumbersome and unsuitable for industrial production. Electro-oxidation, on the other hand, uses p-methyl anisole as a raw material and achieves selective oxidation of p-methyl anisole in a specific electrolyte solution. This method has high selectivity, exceeding 90%, but it suffers from drawbacks such as low current efficiency and high electrode requirements.

[0008] The methylation method for p-hydroxybenzaldehyde uses p-hydroxybenzaldehyde as a raw material. Under the action of a methylating agent, a phenolic hydroxymethoxylation reaction occurs, resulting in the high-yield production of p-hydroxybenzaldehyde. This method is simple, has a high yield, and is a key research focus and hot topic. It is also the main route for the current production of p-methoxybenzaldehyde. Commonly used methylating agents include dimethyl sulfate (DMS), chloromethane, and dimethyl carbonate (DMC). Dimethyl sulfate (DMS) and chloromethane are highly toxic and hazardous substances, and chloromethane gas is flammable and explosive, posing significant safety hazards when used as methylating agents. Dimethyl carbonate, as a green and low-toxicity methylating agent that has emerged in recent years, is currently the most suitable methylating agent to replace dimethyl sulfate and halomethanes due to its low toxicity and minimal environmental impact. With the growing call for green chemistry in recent years, the application of dimethyl carbonate as a methylating agent in industrial production will become an inevitable trend. The preparation of p-methoxybenzaldehyde by methylating dimethyl carbonate with p-hydroxybenzaldehyde has good development prospects.

[0009] In related technologies, patent document CN102452913A discloses a synthesis process for anisaldehyde. This process involves mixing p-hydroxybenzaldehyde, dimethyl sulfoxide, a phase-transfer catalyst (hexadecyltrimethylammonium bromide), potassium carbonate, and dimethyl carbonate, and then refluxing the mixture at 90-170°C and atmospheric pressure. However, this method requires continuous reflux, resulting in high energy consumption, low purity of the final product, and a high amount of dimethyl carbonate used (specifically 5-10 times the molar amount of p-hydroxybenzaldehyde), leading to high costs. Summary of the Invention

[0010] In view of this, the present invention provides a method for producing p-methoxybenzaldehyde to solve the above-mentioned technical problems of low purity, high energy consumption, and high cost.

[0011] Furthermore, the inventors discovered that the reflux reaction temperature (90-170℃) in patent document CN102452913A is higher than the boiling point of dimethyl carbonate (approximately 90℃). Because the reaction is carried out at high temperature under normal pressure, dimethyl carbonate rapidly vaporizes, resulting in poor reaction efficiency, even though the claimed yield is 88.7%. However, when the inventors produced the product according to the conditions described in the patent document, the actual yield was only around 60% at most. Clearly, the yield falls far short of the claimed level.

[0012] To achieve the above solution, the technical solution of the present invention is as follows:

[0013] In a first aspect, the present invention provides a method for producing p-methoxybenzaldehyde, wherein the p-methoxybenzaldehyde is prepared from p-hydroxybenzaldehyde and dimethyl carbonate as raw materials by a dimethyl carbonate methylation reaction in the presence of a solvent and an alkaline catalyst, wherein the dimethyl carbonate methylation reaction is carried out at a temperature of 150-160°C and in an autoclave, preferably at a temperature of 155-160°C and in an autoclave.

[0014] It should be noted that in this application, high pressure refers to pressure higher than normal pressure, and the specific pressure is the pressure that the dimethyl carbonate methylation reaction system can reach under temperature conditions of 150-160℃ (without applying external pressure separately).

[0015] For example, taking a 500ml autoclave as an example, the pressure at the end of the reaction is 6-10MPa / mol, preferably 7-10MPa / mol.

[0016] Optionally, the duration of the dimethyl carbonate methylation reaction is 6-7 hours, preferably 6.5-7 hours.

[0017] Optionally, the molar ratio of p-hydroxybenzaldehyde to dimethyl carbonate is 1:3-4, preferably 1:3.2-4.

[0018] Optionally, the solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, methanol, ethyl acetate, and water.

[0019] Optionally, in the dimethyl carbonate methylation reaction system, the concentration of p-hydroxybenzaldehyde is 2-5 mol / L, preferably 3-5 mol / L, that is, the ratio of p-hydroxybenzaldehyde to the solvent is 1 mol: 0.2-0.5 L, preferably 1 mol: 0.2-0.3 L.

[0020] Optionally, the alkaline catalyst is selected from at least one of potassium carbonate, sodium carbonate, sodium hydroxide, and β-zeolite.

[0021] Optionally, the molar ratio of the alkaline catalyst to the p-hydroxybenzaldehyde is 0.005-0.01:1, preferably 0.006-0.01:1.

[0022] Optionally, the method for producing p-methoxybenzaldehyde further includes: filtering the methylation reaction product of dimethyl percarbonate and distilling the resulting filtrate.

[0023] Optionally, the method for producing p-methoxybenzaldehyde further includes: using the filter residue obtained from vacuum filtration and / or the residue from the distillation vessel as a catalyst to prepare p-methoxybenzaldehyde.

[0024] Optionally, the method for producing p-methoxybenzaldehyde further includes: dissolving the residue obtained during the methylation reaction of dimethyl percarbonate, filtering, extracting the filtrate obtained from the filtration, washing, separating the organic phase, and distilling the obtained organic phase to collect a portion of the undistilled product; adjusting the pH of the aqueous phase to acidic to recover a small amount of unreacted raw materials.

[0025] In this application, an inorganic strong base solution is used to dissolve the reactor residue obtained during the methylation reaction of dimethyl percarbonate. Examples of inorganic strong bases include strong oxidizing agents such as sodium hydroxide and potassium hydroxide.

[0026] In this application, xylene, dichloromethane, ethyl acetate and other substances are used for extraction.

[0027] As described above, the method for producing p-methoxybenzaldehyde in this application has the following beneficial effects:

[0028] This application controls the dimethyl carbonate methylation reaction at a high temperature (150-160°C) and in a high-pressure reactor, enabling dimethyl carbonate to exist in liquid form in the reaction system at a reaction temperature far exceeding its boiling point (90°C). This promotes a smoother dimethyl carbonate methylation reaction, thereby increasing the yield, reducing energy consumption, and improving the purity of the obtained p-methoxybenzaldehyde product.

[0029] This application controls the methylation reaction of dimethyl carbonate at a high temperature (150-160°C) and in a high-pressure reactor, enabling dimethyl carbonate to exist in liquid form in the reaction system at a reaction temperature far exceeding its boiling point (90°C). This reduces the amount of dimethyl carbonate used, increases the yield (>90%), and avoids the low-temperature reflux required for high-temperature reactions under normal pressure, thus reducing the energy consumption required for the reaction.

[0030] This application uses dimethyl carbonate (DMC), a green and low-toxicity methylating agent, to prepare p-methoxybenzaldehyde, avoiding the use of highly toxic and dangerous methylating agents such as dimethyl sulfate (DMS) and chloromethane.

[0031] The method described in this application is simple to operate. The material is added to a high-pressure reactor and then heated in a sealed manner to react. After the reaction is completed, the mixture is filtered and the filtrate is distilled to obtain p-methoxybenzaldehyde.

[0032] The method described in this application is environmentally friendly and produces minimal pollution from waste.

[0033] Using the method described in this application, the filter residue and reactor residue obtained from the dimethyl carbonate methylation reaction can be reused as catalysts in the next batch of reaction, which can improve resource utilization while ensuring high yield, high purity and stable production.

[0034] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, and not for limiting the scope of protection of the present invention.

[0036] One embodiment of this application provides a method for producing p-methoxybenzaldehyde, wherein p-methoxybenzaldehyde is prepared by a dimethyl carbonate methylation reaction in the presence of a solvent and an alkaline catalyst using p-hydroxybenzaldehyde and dimethyl carbonate as raw materials. The dimethyl carbonate methylation reaction is carried out at a temperature of 150-160°C in an autoclave, and the reaction time is 6-7 hours.

[0037] The molar ratio of p-hydroxybenzaldehyde to dimethyl carbonate is 1:3-4;

[0038] The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, methanol, ethyl acetate and water;

[0039] In the dimethyl carbonate methylation reaction system, the concentration of p-hydroxybenzaldehyde is 2-5 mol / L;

[0040] The alkaline catalyst is selected from at least one of potassium carbonate, sodium carbonate, sodium hydroxide and β molecular sieve, and the molar ratio of the alkaline catalyst to the p-hydroxybenzaldehyde is 0.005-0.01:1, preferably 0.006-0.01:1;

[0041] The methylation product of dimethyl percarbonate was filtered, and the resulting filtrate was distilled.

[0042] In another embodiment of this application, the method for producing p-methoxybenzaldehyde further includes: using the filter residue obtained by vacuum filtration and / or the residue of the distillation vessel as a catalyst to prepare p-methoxybenzaldehyde.

[0043] In another embodiment of this application, the method for producing p-methoxybenzaldehyde further includes: dissolving the residue obtained during the methylation reaction of dimethyl percarbonate, filtering, extracting the filtrate obtained from the filtration, washing, separating the organic phase, and distilling the obtained organic phase to collect a portion of the undistilled product; adjusting the pH of the aqueous phase to acidic to recover a small amount of unreacted raw materials.

[0044] The present invention will be described in detail below through specific examples and embodiments. It should also be understood that the following embodiments are only for specific illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0045] Example 1

[0046] A method for producing p-methoxybenzaldehyde (i.e., anisaldehyde), the specific steps of which are as follows:

[0047] Add 4.0 g of potassium carbonate and 120 mL of N,N-dimethylformamide (DMF) to a 500 mL high-pressure reactor, then add 48.8 g (0.4 mol) of p-hydroxybenzaldehyde to the reactor and stir.

[0048] After the material has dissolved completely (i.e., the material in the system is completely dissolved), add 126.1g (about 118ml) of dimethyl carbonate (i.e., DMC, 1.4mol);

[0049] Cover the reactor, purge with nitrogen and vacuum three times, then close the valve. Heat and stir (400 rpm) until the temperature inside the reactor reaches 155°C. Maintain the reaction at 155°C with stirring for 6 hours. The reaction principle is as follows:

[0050] When the reaction is complete, the pressure inside the high-pressure reactor is 2.3 MPa (this pressure is due to the CO2 produced by the decomposition of DMC in the system and the high temperature). The temperature inside the reactor is cooled to 30°C (at this time the pressure inside the reactor is 0.8 MPa), the pressure is released, the reactor is opened, the reaction liquid is poured out, and the mixture is filtered.

[0051] After washing the high-pressure reactor with 20 mL of N,N-dimethylformamide (DMF), pour out the solution for rinsing and then filter.

[0052] The filtrates obtained from vacuum filtration and filtration were combined, and the combined filtrates were placed in a distillation apparatus for distillation. The fore fraction at -0.097 MPa and below 120℃ (external temperature) was collected, and the product was distilled off. The fraction at -0.00001 MPa and below 85-100℃ (external temperature) was collected to obtain 49.8 g of colorless oily liquid product (i.e., p-methoxybenzaldehyde finished product) and 8.7 g of residue in the reactor. The yield was calculated to be 90.74%.

[0053] The content of p-methoxybenzaldehyde in a colorless, oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) was determined by gas chromatography.

[0054] The purity of the p-methoxybenzaldehyde product was tested and found to be 99.12%.

[0055] according to

[0056] Where: E - total energy consumption, n - energy-consuming equipment, P i -Equipment power, t i - Equipment working time, r- Electricity to standard coal equivalent coefficient (0.1229 kgee / (kW·h)) Calculation of energy consumption for producing p-methoxybenzaldehyde product according to the method of this embodiment.

[0057] Calculations show that the energy consumption for producing p-methoxybenzaldehyde according to the method described in this embodiment is approximately 2.23 kgee / mol.

[0058] Example 2

[0059] The difference between this embodiment and Embodiment 1 is that the filter residue obtained from filtration in Embodiment 1 and the reactor residue obtained in Embodiment 1 are used to replace potassium carbonate.

[0060] In this embodiment, 51.4g of colorless oily liquid product (i.e., p-methoxybenzaldehyde finished product) was obtained, and 13.3g of residue was obtained in the reactor. The yield was calculated to be 93.35%.

[0061] The content of p-methoxybenzaldehyde in a colorless, oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) was determined by gas chromatography.

[0062] The purity of the p-methoxybenzaldehyde product was found to be 98.80% after testing.

[0063] The energy consumption for producing p-methoxybenzaldehyde according to the energy consumption calculation formula in Example 1 is calculated.

[0064] Calculations show that the energy consumption for producing p-methoxybenzaldehyde according to the method described in this embodiment is 2.16 kgee / mol.

[0065] Example 3

[0066] The difference between this embodiment and embodiment 1 is that the filter residue obtained from filtration in embodiment 2 and the reactor residue obtained in embodiment 2 are used to replace potassium carbonate.

[0067] In this embodiment, 51.6g of colorless oily liquid product (i.e., p-methoxybenzaldehyde finished product) was obtained, and 14.5g of residue was obtained in the reactor. The yield was calculated to be 93.88%.

[0068] The content of p-methoxybenzaldehyde in a colorless, oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) was determined by gas chromatography.

[0069] The purity of the p-methoxybenzaldehyde product was tested and found to be 98.88%.

[0070] The energy consumption for producing p-methoxybenzaldehyde according to the energy consumption calculation formula in Example 1 is calculated.

[0071] Calculations show that the energy consumption for producing p-methoxybenzaldehyde according to the method described in this embodiment is 2.15 kgee / mol.

[0072] Example 4

[0073] The difference between this embodiment and embodiment 1 is that the filter residue obtained from the filtration in embodiment 3 and the reactor residue obtained in embodiment 3 are used to replace potassium carbonate.

[0074] In this embodiment, 51.7g of colorless oily liquid product (i.e., p-methoxybenzaldehyde finished product) was obtained, and 18.4g of residue was obtained in the reactor. The yield was calculated to be 93.82%.

[0075] The content of p-methoxybenzaldehyde in a colorless, oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) was determined by gas chromatography.

[0076] The purity of the p-methoxybenzaldehyde product was tested and found to be 98.72%.

[0077] The energy consumption for producing p-methoxybenzaldehyde according to the energy consumption calculation formula in Example 1 is calculated.

[0078] Calculations show that the energy consumption for producing p-methoxybenzaldehyde according to the method described in this embodiment is 2.15 kgee / mol.

[0079] The 18.4g residue obtained in this example was dissolved in 50mL of 1mol / L KOH solution and filtered. The filtrate was extracted with 30mL of xylene, washed, and the organic phase was separated. The organic phase was then distilled to separate 3.5g of colorless oily anisaldehyde liquid. The pH of the aqueous phase was adjusted to acidic, and a light brownish-yellow solid precipitated. 6.2g of solid (98.23% p-hydroxybenzaldehyde content) was collected.

[0080] Example 5

[0081] The difference between this embodiment and embodiment 1 is that the filter residue obtained from filtration in embodiment 4 is used instead of potassium carbonate.

[0082] In this embodiment, 52.2g of colorless oily liquid product (i.e., p-methoxybenzaldehyde finished product) was obtained, and 17.4g of residue was obtained in the reactor. The yield was calculated to be 94.37%.

[0083] The content of p-methoxybenzaldehyde in a colorless, oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) was determined by gas chromatography.

[0084] The purity of the p-methoxybenzaldehyde product was found to be 98.44% after testing.

[0085] The energy consumption for producing p-methoxybenzaldehyde according to the energy consumption calculation formula in Example 1 is calculated.

[0086] Calculations show that the energy consumption for producing p-methoxybenzaldehyde according to the method described in this embodiment is 2.14 kgee / mol.

[0087] The 17.4g residue obtained in this example was dissolved in 50mL of 1mol / L KOH solution and filtered. The filtrate was extracted with 30mL of xylene, washed, and the organic phase was separated. The organic phase was then distilled to separate 2.8g of colorless oily anisaldehyde liquid. The pH of the aqueous phase was adjusted to acidic, and a light brownish-yellow solid precipitated. 5.5g of solid (97.00% p-hydroxybenzaldehyde content) was collected.

[0088] Comparative Example 1

[0089] The difference between this comparative example and Example 1 is that an atmospheric pressure reaction device is used instead of a high-pressure reaction vessel, and a distillation device is set up. DMC is added dropwise at a temperature of 155°C, and the distilled fraction is repeatedly added dropwise to the reaction liquid. The gas phase detection shows that the product content no longer changes.

[0090] This comparative example yielded 31.7g of a colorless, oily liquid product (i.e., p-methoxybenzaldehyde finished product) and 10.2g of residue in the reactor. The calculated yield was 79.98%.

[0091] The content of p-methoxybenzaldehyde in a colorless, oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) was determined by gas chromatography.

[0092] The purity of the p-methoxybenzaldehyde product was tested and found to be 96.75%.

[0093] The energy consumption for producing p-methoxybenzaldehyde according to the energy consumption calculation formula in Example 1 is calculated.

[0094] Calculations show that the energy consumption for producing p-methoxybenzaldehyde according to the method described in this embodiment is 9.81 kgee / mol.

[0095] Comparative Example 2

[0096] The specific steps for producing p-methoxybenzaldehyde according to the method in CN1024592913A are as follows:

[0097] 0.1 mol of p-hydroxybenzaldehyde was placed in a 250 mL four-necked flask equipped with a stirrer and reflux device. 100 mL of dimethyl sulfoxide was added, followed by 0.03 mol of phase transfer catalyst cetyltrimethylammonium bromide and 0.08 mol of potassium carbonate. Under nitrogen protection at atmospheric pressure, 1 mol of dimethyl carbonate was added dropwise at 80 °C. After the addition was complete, the temperature was raised to 110 °C and refluxed. The reaction was monitored by thin-layer chromatography. After 5 h of reaction, the reaction solution was filtered to recover potassium carbonate. The remaining dimethyl carbonate was distilled off under atmospheric pressure. The solution was then distilled under reduced pressure, and the fraction below -0.097 MPa and 120 °C (external temperature) was collected. The product was then distilled off, and the fraction below -0.00001 MPa and 85-100 °C (external temperature) was collected. The yield was calculated.

[0098] The calculated yield was 60.14%.

[0099] The content of p-methoxybenzaldehyde in a colorless, oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) was determined by gas chromatography.

[0100] The purity of the p-methoxybenzaldehyde product was found to be 98.55% after testing.

[0101] The energy consumption for producing p-methoxybenzaldehyde according to the energy consumption calculation formula in Example 1 is calculated.

[0102] Calculations show that the energy consumption for producing p-methoxybenzaldehyde according to the method described in this embodiment is approximately 29.48 kgee / mol.

[0103] As can be seen from the above examples, using filter residue as a catalyst to prepare p-methoxybenzaldehyde product still maintains a high level of yield and purity (yield > 93%, purity > 98%). This result indicates that using the method of this application, with the residue obtained from the dimethyl carbonate methylation reaction (i.e., filter residue) as a catalyst, can ensure stable production with high yield and high purity while improving resource utilization.

[0104] As can be seen from Example 1 and Comparative Examples 1-2 above, compared with Comparative Example 1 (atmospheric pressure reactor) and Comparative Example 2 (under atmospheric pressure), Example 1 (high pressure reactor) showed a significantly improved yield, significantly reduced energy consumption, and significantly increased purity of the obtained p-methoxybenzaldehyde product. This result indicates that by controlling the dimethyl carbonate methylation reaction at a high temperature (150-160℃) and using a high-pressure reactor as the reaction vessel, this application enables dimethyl carbonate to exist in a liquid form in the reaction system, promoting a smoother dimethyl carbonate methylation reaction, thereby improving the yield, reducing energy consumption, and simultaneously increasing the purity of the obtained p-methoxybenzaldehyde product.

[0105] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for producing p-methoxybenzaldehyde, wherein the p-methoxybenzaldehyde is prepared from p-hydroxybenzaldehyde and dimethyl carbonate via a dimethyl carbonate methylation reaction in the presence of a solvent and an alkaline catalyst, characterized in that... The dimethyl carbonate methylation reaction was carried out at a temperature of 150-160°C in an autoclave.

2. The method for producing p-methoxybenzaldehyde as described in claim 1, characterized in that, The methylation reaction of the dimethyl carbonate lasts for 6-7 hours.

3. The method for producing p-methoxybenzaldehyde as described in claim 1, characterized in that, The molar ratio of p-hydroxybenzaldehyde to dimethyl carbonate is 1:3-4.

4. The method for producing p-methoxybenzaldehyde as described in claim 1, characterized in that, The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, methanol, ethyl acetate, and water.

5. In the method for producing p-methoxybenzaldehyde as described in claim 1, the concentration of p-hydroxybenzaldehyde in the dimethyl carbonate methylation reaction system is 2-5 mol / L.

6. The method for producing p-methoxybenzaldehyde as described in claim 1, characterized in that, The catalyst is selected from at least one of potassium carbonate, sodium carbonate, sodium hydroxide, and β-zeolite.

7. The method for producing p-methoxybenzaldehyde as described in claim 1, characterized in that, The molar ratio of the alkaline catalyst to the p-hydroxybenzaldehyde is 0.005-0.01:

1.

8. The method for producing p-methoxybenzaldehyde as described in claim 1, characterized in that, The method for producing p-methoxybenzaldehyde further includes: filtering the methylation reaction product of dimethyl percarbonate and distilling the resulting filtrate.

9. The method for producing p-methoxybenzaldehyde as described in claim 8, characterized in that, The method for producing p-methoxybenzaldehyde further includes: using the filter residue obtained from vacuum filtration and / or the residue from the distillation vessel as a catalyst to prepare p-methoxybenzaldehyde.

10. The method for producing p-methoxybenzaldehyde as described in claim 1, characterized in that, The method for producing p-methoxybenzaldehyde further includes: dissolving the residue obtained during the methylation reaction of dimethyl percarbonate, filtering, extracting the filtrate obtained from the filtration, washing, separating the organic phase, and distilling the obtained organic phase to collect some undistilled product; adjusting the pH of the aqueous phase to acidic to recover a small amount of unreacted raw materials.

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