Production method of p-methoxybenzaldehyde

Abstract

The invention relates to the technical field of chemical engineering, in particular to a production method of p-methoxybenzaldehyde. According to the production method of p-methoxybenzaldehyde, p-hydroxybenzaldehyde and dimethyl carbonate are used as raw materials, the p-methoxybenzaldehyde is prepared through a dimethyl carbonate methylation reaction in the presence of a solvent and a basic catalyst, and the dimethyl carbonate methylation reaction is carried out under the conditions that the temperature is 150-160 DEG C and an autoclave is used as a reaction container. According to the method, the methylation reaction of the dimethyl carbonate is controlled at high temperature (150-160 DEG C) and is carried out in the autoclave, so that the dimethyl carbonate mainly exists in a reaction system in a liquid form at the temperature far higher than the boiling point, the methylation reaction of the dimethyl carbonate is promoted to be carried out more smoothly, the yield is improved, the energy consumption is reduced, and meanwhile, the production cost is reduced. The purity of the prepared p-methoxybenzaldehyde finished product is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a production method of p-methoxybenzaldehyde. Background Art

[0002] p-Anisaldehyde (PMBA), also known as p-methoxybenzaldehyde and anisaldehyde, is an important fine chemical with the molecular formula C8H8O2. It is a colorless or light yellow oily liquid with a lasting hawthorn aroma at room temperature. It is widely used and can be used to develop high value-added downstream products, such as raspberry ketone; it can be used to formulate daily flavors and food flavors, such as as the main flavor in hawthorn flower, sunflower, and lilac flavors, and as a modifier in lily of the valley and osmanthus flavors; it is an important intermediate in organic synthesis, an intermediate for the preparation of the antimicrobial drug hydroxyaminocarboxylic acid penicillin, and an intermediate for the synthesis of porphyrin photosensitizers; it can also be used as a fluorescent probe for the determination of biological macromolecules such as nucleic acids.

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

[0004] Among them, the plant extraction method extracts p-methoxybenzaldehyde (PMBA) by adding oxidants and decomposing agents to extracts of fennel oil, dill oil, acacia flower oil, vanilla, etc. However, this method has complex process and low yield, and has been eliminated.

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

[0006] The anisole method refers to the Sommelet reaction method, which can achieve the anisole formylation strategy through multiple steps of reaction, Blanc chloro-methylation reaction-Sommelet reaction, and synthesize p-methoxybenzaldehyde. However, this method produces a large amount of acidic wastewater and serious equipment corrosion, which is not suitable for industrial production.

[0007] The oxidation method of p-methyl anisole can be divided into two methods: chemical oxidation and electro-oxidation. The chemical oxidation method uses oxygen as the oxygen source to directly synthesize p-methoxybenzaldehyde. However, this method is prone to over-oxidation, has many by-products, and is complicated to separate due to its low selectivity. It also uses toxic catalysts, and the process operation is cumbersome and not suitable for industrial production. The electro-oxidation method uses p-methyl anisole as the raw material and realizes the selective oxidation of p-methyl anisole in a specific electrolyte solution. This method has high selectivity, which can exceed 90%, but this method has defects such as low current efficiency and high electrode requirements.

[0008] The p-hydroxybenzaldehyde methylation method is a raw material of p-hydroxybenzaldehyde, and under the effect of a methylating agent, a phenolic hydroxyl methoxylation reaction occurs, and p-hydroxybenzaldehyde can be prepared in high yield. The method is simple to react, and the yield is higher, which is the focus and focus of research, and is also the main approach of producing p-methoxybenzaldehyde now. The methylating agent commonly used has dimethyl sulfate (DMS), methyl chloride and dimethyl carbonate (DMC). Dimethyl sulfate (DMS) and methyl chloride are highly toxic and dangerous substances, and methyl chloride gas is flammable and explosive, and there is a large potential safety hazard using the two as methylating agents. And dimethyl carbonate, as a kind of green and low-toxic methylating agent that has risen in recent years, is the methylating agent that is most suitable for replacing dimethyl sulfate, halogenated methyls, etc., because of its low toxicity and little impact on the environment. With the growing call for green chemistry in recent years, the application of dimethyl carbonate as a methylation agent in industrial production will become a general trend. The preparation of p-methoxybenzaldehyde by methylation of dimethyl carbonate with p-hydroxybenzaldehyde as raw material has good development prospects.

[0009] In the related art, the patent document with publication number CN102452913A discloses a synthesis process of anisaldehyde, in which p-hydroxybenzaldehyde, dimethyl sulfoxide, phase transfer catalyst hexadecyltrimethylammonium bromide, potassium carbonate and dimethyl carbonate are mixed and refluxed at 90-170° C. and normal pressure. However, this solution requires continuous reflux, has high energy consumption, has a low purity of the finished product, uses a large amount of dimethyl carbonate (specifically 5-10 times the molar amount of p-hydroxybenzaldehyde), and has a high cost. 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 such as low purity, high energy consumption and high cost.

[0011] In addition, the inventors also found that the reflux reaction temperature (90-170°C) of the patent document with publication number CN102452913A is higher than the boiling point (about 90°C) of dimethyl carbonate. Since dimethyl carbonate is rapidly gasified due to high temperature reaction under normal pressure, the reaction effect is poor, although it claims that the productivity (i.e., yield) can reach 88.7%. However, the inventors produced according to the conditions shown in their scheme, and the yield was actually only about 60% at most. Obviously, its yield is far from the level it claims.

[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. The p-methoxybenzaldehyde is prepared by methylating dimethyl carbonate using p-hydroxybenzaldehyde and dimethyl carbonate as raw materials in the presence of a solvent and an alkaline catalyst. The methylating reaction of dimethyl carbonate is carried out at a temperature of 150-160° C. and using an autoclave as a reaction container, preferably at a temperature of 155-160° C. and using an autoclave as a reaction container.

[0014] It should be noted that, in the present 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 the temperature condition of 150-160° C. (without applying external pressure separately).

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

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

[0017] Optionally, the molar ratio of the p-hydroxybenzaldehyde to the 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 material ratio of the 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 beta molecular sieve.

[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 comprises: filtering the dimethyl carbonate methylation reaction product by suction, and distilling the obtained filtrate.

[0023] Optionally, the method for producing p-methoxybenzaldehyde further comprises: using the filter residue obtained by suction filtration and / or the distillation still residue as a catalyst to prepare p-methoxybenzaldehyde.

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

[0025] In the present application, an inorganic strong alkali solution is used to dissolve the kettle residue obtained during the methylation reaction of dimethyl percarbonate. Examples of the inorganic strong alkali include strong sodium hydroxide, potassium hydroxide and the like.

[0026] In the present application, xylene, dichloromethane, ethyl acetate and the like are used for extraction.

[0027] As described above, the production method of p-methoxybenzaldehyde of the present application has the following beneficial effects:

[0028] The present invention controls the methylation reaction of dimethyl carbonate at a high temperature (150-160° C.) and performs the reaction in an autoclave, so that dimethyl carbonate can exist in a reaction system in a liquid form at a reaction temperature far exceeding its boiling point (90° C.), thereby promoting the methylation reaction of dimethyl carbonate to proceed more smoothly, thereby improving the yield, reducing energy consumption, and improving the purity of the obtained p-methoxybenzaldehyde product.

[0029] The present invention controls the methylation reaction of dimethyl carbonate at a high temperature (150-160° C.) and carries out the reaction in an autoclave, so that dimethyl carbonate can be present in a liquid form in the reaction system at a reaction temperature far exceeding its boiling point (90° C.), thereby reducing the amount of dimethyl carbonate used and improving the yield (>90%), avoiding the low-temperature reflux required for high-temperature reaction under normal pressure, and reducing the energy consumption required for the reaction.

[0030] The present application adopts the green and low-toxic methylation reagent dimethyl carbonate (DMC) to prepare p-methoxybenzaldehyde, avoiding the use of highly toxic and high-risk methylation reagents such as dimethyl sulfate (DMS) and monochloromethane.

[0031] The method of the present application is simple to operate. The material is added into the autoclave and then the temperature is raised to react. After the reaction is completed, the autoclave is filtered and the filtrate is distilled to obtain p-methoxybenzaldehyde.

[0032] The method of the present application is environmentally friendly and has little pollution of three wastes.

[0033] By adopting the method of the present application for production, the filter residue and kettle residue obtained from the methylation reaction of dimethyl carbonate can be applied to the next batch of reactions as catalysts, thereby ensuring high-yield, high-purity and stable production while improving resource utilization.

[0034] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The present invention can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways 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, not for limiting the scope of protection of the present invention.

[0036] An embodiment of the present application provides a method for producing p-methoxybenzaldehyde, wherein p-methoxybenzaldehyde is prepared by methylating dimethyl carbonate using p-hydroxybenzaldehyde and dimethyl carbonate as raw materials in the presence of a solvent and an alkaline catalyst, wherein the methylating reaction of dimethyl carbonate is carried out at a temperature of 150-160° C. and using an autoclave as a reaction vessel, and the duration of the methylating reaction of dimethyl carbonate 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 beta 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 dimethyl carbonate methylation reaction product is filtered off by suction, and the obtained filtrate is distilled.

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

[0043] In another embodiment of the present application, the method for producing p-methoxybenzaldehyde further includes: dissolving the kettle residue obtained during the methylation reaction of dimethyl percarbonate, filtering, extracting and filtering the filtrate obtained, washing, separating the organic phase, and distilling the obtained organic phase to collect part 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 is described in detail below by specific examples. It should also be understood that the following examples are only used to specifically illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0045] Example 1

[0046] A method for producing p-methoxybenzaldehyde (i.e. anisaldehyde), comprising the following steps:

[0047] 4.0 g of potassium carbonate and 120 mL of N,N-dimethylformamide (DMF) were added to a 500 mL autoclave, and 48.8 g (0.4 mol) of p-hydroxybenzaldehyde was added to the autoclave, and stirred;

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

[0049] Cover the reactor, replace with nitrogen and vacuum alternately three times, then close the valve, heat and stir (400r / min) until the temperature in the reactor rises to 155℃, and stir and react at 155℃ for 6h. The reaction principle is as follows:

[0050]

[0051] At the end of the reaction, the pressure in the autoclave was 2.3 MPa (the pressure was due to the CO2 and high temperature generated by the decomposition of DMC in the system), the temperature was lowered to 30°C (the pressure in the autoclave was 0.8 MPa), the pressure was released, the autoclave was opened, the reaction liquid was poured out, and suction was filtered;

[0052] Wash the autoclave with 20 mL of N,N-dimethylformamide (DMF), then pour out the rinse solution and filter;

[0053] Combine the filtrate obtained by suction filtration and the filtrate obtained by filtration, place the combined filtrate in a distillation device for distillation, collect the front fraction within 120°C (external temperature) at -0.097MPa, evaporate the product, collect the fraction at 85-100°C (external temperature) at -0..00001MPa, and obtain 49.8g of colorless oily liquid product (i.e., finished p-methoxybenzaldehyde) and 8.7g of kettle residue. The yield is calculated to be 90.74%.

[0054] The content of p-methoxybenzaldehyde in the colorless oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) is detected by gas chromatography.

[0055] After testing, the purity of the finished p-methoxybenzaldehyde was 99.12%.

[0056] according to

[0057]

[0058] Where: E-comprehensive energy consumption, n-energy consuming equipment, P i - Equipment power, t i - equipment working time, r-electricity conversion coefficient of standard coal (0.1229kgee / (kW·h)) is used to calculate the energy consumption of producing p-methoxybenzaldehyde finished product according to the method of this embodiment.

[0059] According to calculation, the energy consumption for producing the p-methoxybenzaldehyde product according to the method of this embodiment is about 2.23 kgee / mol.

[0060] Example 2

[0061] The difference between this embodiment and embodiment 1 is that the filter residue obtained by suction filtration in embodiment 1 and the kettle residue obtained in embodiment 1 are used to replace potassium carbonate.

[0062] In this example, 51.4 g of a colorless oily liquid product (i.e., the finished product of p-methoxybenzaldehyde) and 13.3 g of a kettle residue were obtained. The yield was calculated to be 93.35%.

[0063] The content of p-methoxybenzaldehyde in the colorless oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) is detected by gas chromatography.

[0064] After testing, the purity of the finished p-methoxybenzaldehyde was 98.80%.

[0065] The energy consumption of producing the p-methoxybenzaldehyde product according to the method of this embodiment is calculated according to the energy consumption calculation formula in Example 1.

[0066] According to calculation, the energy consumption for producing the p-methoxybenzaldehyde product according to the method of this embodiment is 2.16 kgee / mol.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that the filter residue obtained by suction filtration in embodiment 2 and the kettle residue obtained in embodiment 2 are used to replace potassium carbonate.

[0069] In this example, 51.6 g of a colorless oily liquid product (i.e., the finished product of p-methoxybenzaldehyde) and 14.5 g of a kettle residue were obtained. The yield was calculated to be 93.88%.

[0070] The content of p-methoxybenzaldehyde in the colorless oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) is detected by gas chromatography.

[0071] After testing, the purity of the finished p-methoxybenzaldehyde was 98.88%.

[0072] The energy consumption of producing the p-methoxybenzaldehyde product according to the method of this embodiment is calculated according to the energy consumption calculation formula in Example 1.

[0073] According to calculation, the energy consumption for producing the p-methoxybenzaldehyde product according to the method of this embodiment is 2.15 kgee / mol.

[0074] Example 4

[0075] The difference between this embodiment and embodiment 1 is that the filter residue obtained by suction filtration in embodiment 3 and the kettle residue obtained in embodiment 3 are used to replace potassium carbonate.

[0076] In this example, 51.7 g of a colorless oily liquid product (i.e., the finished product of p-methoxybenzaldehyde) and 18.4 g of a kettle residue were obtained. The yield was calculated to be 93.82%.

[0077] The content of p-methoxybenzaldehyde in the colorless oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) is detected by gas chromatography.

[0078] After testing, the purity of the finished p-methoxybenzaldehyde was 98.72%.

[0079] The energy consumption of producing the p-methoxybenzaldehyde product according to the method of this embodiment is calculated according to the energy consumption calculation formula in Example 1.

[0080] According to calculation, the energy consumption for producing the p-methoxybenzaldehyde product according to the method of this embodiment is 2.15 kgee / mol.

[0081] 18.4 g of the kettle residue obtained in this example was dissolved in 50 mL of 1 mol / L KOH solution and filtered, the filtrate was extracted with 30 mL of xylene, washed, and the organic phase was separated. The organic phase was distilled to separate 3.5 g of colorless oily anisaldehyde liquid; the pH of the aqueous phase was adjusted to acidic, a light brown solid was precipitated, and 6.2 g of solid (p-hydroxybenzaldehyde content 98.23%) was collected.

[0082] Example 5

[0083] The difference between this embodiment and embodiment 1 is that the filter residue obtained by filtration in embodiment 4 is used instead of potassium carbonate.

[0084] In this example, 52.2 g of a colorless oily liquid product (i.e., the finished product of p-methoxybenzaldehyde) and 17.4 g of a kettle residue were obtained. The yield was calculated to be 94.37%.

[0085] The content of p-methoxybenzaldehyde in the colorless oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) is detected by gas chromatography.

[0086] After testing, the purity of the finished p-methoxybenzaldehyde was 98.44%.

[0087] The energy consumption of producing the p-methoxybenzaldehyde product according to the method of this embodiment is calculated according to the energy consumption calculation formula in Example 1.

[0088] According to calculation, the energy consumption for producing the p-methoxybenzaldehyde product according to the method of this embodiment is 2.14 kgee / mol.

[0089] The 17.4 g of the kettle residue obtained in this example was dissolved in 50 mL of a 1 mol / L KOH solution and filtered, the filtrate was extracted with 30 mL of xylene, washed, and the organic phase was separated. The organic phase was distilled to separate 2.8 g of colorless oily anisaldehyde liquid; the pH of the aqueous phase was adjusted to acidic, a light brown solid was precipitated, and 5.5 g of solid (p-hydroxybenzaldehyde content 97.00%) was collected.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is that a normal pressure reaction apparatus is used instead of a high pressure reaction kettle, and a distillation apparatus is set up at the same time, DMC is added dropwise at 155°C for reaction, and then the distilled fraction is repeatedly added dropwise into the reaction liquid gas phase to detect that the product content does not change.

[0092] This comparative example obtained 31.7 g of a colorless oily liquid product (i.e., the finished product of p-methoxybenzaldehyde) and 10.2 g of a kettle residue. The yield was calculated to be 79.98%.

[0093] The content of p-methoxybenzaldehyde in the colorless oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) is detected by gas chromatography.

[0094] After testing, the purity of the finished p-methoxybenzaldehyde was 96.75%.

[0095] The energy consumption of producing the p-methoxybenzaldehyde product according to this comparative example was calculated according to the energy consumption calculation formula in Example 1.

[0096] According to calculation, the energy consumption for producing the p-methoxybenzaldehyde product according to the method of this embodiment is 9.81 kgee / mol.

[0097] Comparative Example 2

[0098] The p-methoxybenzaldehyde finished product is produced according to the method in CN1024592913A, and the specific steps are as follows:

[0099] Take 0.1 mol of p-hydroxybenzaldehyde and place it in a 250mL four-necked flask with a stirrer and a reflux device, add 100mL of dimethyl sulfoxide, then add 0.03mol of phase transfer catalyst hexadecyltrimethylammonium bromide and 0.08mol of potassium carbonate; under the protection of nitrogen at normal pressure, add 1mol of dimethyl carbonate dropwise at 80°C, after the dropwise addition is completed, raise the temperature to 110°C for reflux reaction, track the reaction by thin layer chromatography analysis, react for 5h, filter the reaction solution to recover potassium carbonate, distill the remaining dimethyl carbonate at normal pressure, then distill the solution under reduced pressure, collect the front fraction within 120°C (external temperature) at -0.097MPa, then distill out the product, collect the fraction at 85-100°C (external temperature) at -0.00001MPa, and calculate the yield.

[0100] The yield was calculated to be 60.14%.

[0101] The content of p-methoxybenzaldehyde in the colorless oily liquid product (i.e., the purity of the p-methoxybenzaldehyde finished product) is detected by gas chromatography.

[0102] After testing, the purity of the finished p-methoxybenzaldehyde was 98.55%.

[0103] The energy consumption of producing the p-methoxybenzaldehyde product according to this comparative example was calculated according to the energy consumption calculation formula in Example 1.

[0104] According to calculation, the energy consumption for producing the p-methoxybenzaldehyde product according to the method of this embodiment is about 29.48 kgee / mol.

[0105] As can be seen from the above examples, the yield and purity of the p-methoxybenzaldehyde product are still maintained at a relatively high level (yield>93%, purity>98%) when the filter residue is used as a catalyst. The results show that the method of the present application is used for production, and the residue (i.e., the filter residue) obtained by the methylation reaction of dimethyl carbonate is used as a catalyst, which can ensure high yield, high purity and stable production while improving resource utilization.

[0106] It can be seen from the above-mentioned Example 1 and Comparative Examples 1-2 that, compared with Comparative Example 1 (normal pressure reactor) and Comparative Example 2 (under normal pressure conditions), the yield of Example 1 (high pressure reactor) is significantly improved, the energy consumption is significantly reduced, and the purity of the obtained p-methoxybenzaldehyde finished product is significantly increased. The result shows that the present application controls the dimethyl carbonate methylation reaction at a high temperature (150-160° C.) and is carried out under the conditions of using an autoclave as a reaction vessel, so that dimethyl carbonate can be present in the reaction system in a liquid form, and the dimethyl carbonate methylation reaction is promoted to proceed more smoothly, thereby improving the yield and reducing energy consumption while improving the purity of the obtained p-methoxybenzaldehyde finished product.

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall 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 by methylation reaction of dimethyl carbonate in the presence of a solvent and an alkaline catalyst, characterized in that: The dimethyl carbonate methylation reaction is carried out at a temperature of 150-160° C. in an autoclave as a reaction vessel.

2. The method for producing p-anisaldehyde according to claim 1, wherein The duration of the dimethyl carbonate methylation reaction is 6-7 hours.

3. The method for producing p-methoxybenzaldehyde according to claim 1, wherein The molar ratio of the p-hydroxybenzaldehyde to the dimethyl carbonate is 1:3-4.

4. The method for producing p-methoxybenzaldehyde according to claim 1, wherein The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, methanol, ethyl acetate and water.

5. The production method of p-methoxybenzaldehyde as claimed in claim 1, wherein in the dimethyl carbonate methylation reaction system, the concentration of the p-hydroxybenzaldehyde is 2-5 mol / L.

6. The method for producing p-methoxybenzaldehyde according to claim 1, wherein The catalyst is selected from at least one of potassium carbonate, sodium carbonate, sodium hydroxide and beta molecular sieve.

7. The method for producing p-methoxybenzaldehyde according to claim 1, wherein The molar ratio of the alkaline catalyst to the p-hydroxybenzaldehyde is 0.005-0.01:

1.

8. The method for producing p-methoxybenzaldehyde according to claim 1, wherein The method for producing p-methoxybenzaldehyde further comprises: filtering the product of the methylation reaction of dimethyl carbonate by suction, and distilling the obtained filtrate.

9. The method for producing p-methoxybenzaldehyde according to claim 8, wherein The method for producing p-methoxybenzaldehyde further comprises: using the filter residue obtained by suction filtration and / or the residue in the rectification kettle as a catalyst to prepare p-methoxybenzaldehyde.

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

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