A method for preparing phenylacetaldehyde

Abstract

The invention discloses a method for preparing phenylacetaldehyde, which comprises the following steps: preparing liquid A: dissolving cinnamaldehyde and methanol in a light solvent to obtain liquid A, wherein the light solvent is insoluble in water, and the density and boiling point of the light solvent are both lower than those of water; preparing liquid B: preparing liquid B by mixing a water-soluble strong base and hydrogen peroxide with water; first reaction: slowly adding liquid A to the upper layer of liquid B at 0-5°C; adding hydrogen peroxide to liquid B to adjust so that the mass concentration of hydrogen peroxide in liquid B is maintained at 20%-40%; removing volatiles: retaining liquid A after the reaction is completed, evaporating liquid A at 40-60°C to obtain liquid C; filtering liquid C at 0-5°C to obtain solid D; second reaction: mixing solid D with a formic acid aqueous solution and heating under reflux to react, to obtain a reaction liquid containing phenylacetaldehyde. The method for preparing phenylacetaldehyde provided by the invention has the effect of reducing the mutual consumption of methanol and hydrogen peroxide and facilitating the control of the reaction rate.

Description

Technical Field

[0001] The invention belongs to the technical field of organic compound preparation, and in particular relates to a method for preparing phenylacetaldehyde. Background Art

[0002] Phenylacetaldehyde is a spice with the aroma of hosta. It is one of the important spices for blending a variety of floral flavors. It has important uses in the spice and cosmetics industries. It is also an important raw material for fine chemicals such as synthetic drugs, food additives and agricultural chemicals.

[0003] At present, the preparation methods of phenylacetaldehyde mainly include oxidation method, reduction method and Daren method. The oxidation method mainly oxidizes β-phenylethanol or phenylethylene glycol to phenylacetaldehyde under the action of metal catalysts or microorganisms; the reduction method usually uses phenylacetic acid or phenylacetic acid ester as raw materials, and converts the carboxyl group or ester group into an aldehyde group under the action of a reducing agent; the Daren method uses benzaldehyde and ethyl chloroacetate as raw materials, and generates epoxy esters under the action of base catalysis, and then the substance is subjected to alkaline hydrolysis and decarboxylation to obtain phenylacetaldehyde.

[0004] There is a method that uses cinnamaldehyde as a raw material, oxidizes it with hydrogen peroxide, and then heats it under acidic conditions to decarboxylate it to obtain phenylacetaldehyde. In this method, methanol is used to adjust the concentration of cinnamaldehyde to control the reaction rate. However, in this method, methanol and hydrogen peroxide are prone to react during the mixing stage, resulting in mutual consumption and the generation of by-products, which wastes raw materials and affects subsequent purification work. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for preparing phenylacetaldehyde.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] A method for preparing phenylacetaldehyde comprises the following steps:

[0008] Preparation of liquid A: dissolving cinnamaldehyde and methanol in a light solvent to obtain liquid A, wherein the light solvent is insoluble in water, and the density and boiling point of the light solvent are both lower than those of water;

[0009] Preparation of liquid B: prepare liquid B by mixing water-soluble strong alkali and hydrogen peroxide with water;

[0010] First reaction: at 0-5°C, liquid A is slowly added to the upper layer of liquid B to separate liquid A and liquid B; hydrogen peroxide is added to the liquid B to adjust the mass concentration of hydrogen peroxide in the liquid B to be maintained at 20%-40%, and the reaction is stopped when the concentration of hydrogen peroxide in the liquid B tends to be stable;

[0011] Remove volatiles: After the reaction is completed, keep liquid A, evaporate liquid A at 40-60°C to volatilize methanol, and obtain liquid C; filter liquid C at 0-5°C to obtain solid D;

[0012] Second reaction: Solid D is mixed with aqueous formic acid solution and then heated under reflux to react, thereby obtaining a reaction solution containing phenylacetaldehyde.

[0013] In the present invention, when removing volatiles, methanol has a small molecular weight and a low boiling point. At 40-60° C., methanol evaporates in large quantities while the amount of light solvent evaporates in small quantities. If the evaporation temperature is less than 40° C., the evaporation treatment time will be too long; if the evaporation temperature is greater than 60° C., a large amount of light solvent will also evaporate, affecting the yield.

[0014] Preferably, the method further comprises purification: adding solid magnesium hydroxide to the reaction solution containing phenylacetaldehyde until the pH value is 6-7, filtering, washing the filtrate with water until it is neutral, desolventizing, and distilling to obtain phenylacetaldehyde.

[0015] In the present invention, the carboxyl-containing compound produced in the decarboxylation process and other carboxyl-containing compounds can react with magnesium hydroxide to produce an acid-base neutralization reaction, thereby producing a non-volatile and non-soluble solid precipitate, which is beneficial to subsequent desolventizing work and improves the purity of the product.

[0016] Preferably, the distillation step is achieved by distillation under reduced pressure.

[0017] Preferably, in the step of preparing liquid A, the mass ratio of the cinnamaldehyde to the methanol is 1:(1-5).

[0018] Preferably, the volume ratio of the liquid A to the liquid B is 1:(0.1-0.5).

[0019] Preferably, in the step of preparing liquid A, the light solvent is selected from one or more of benzene, ethyl acetate, diethyl ether and cyclohexane.

[0020] In the present invention, the light solvent is specifically selected from ethyl acetate.

[0021] Preferably, in the step of preparing liquid B, the water-soluble strong base is selected from one or more of sodium hydroxide and potassium hydroxide.

[0022] In the present invention, the water-soluble strong base is specifically selected from sodium hydroxide.

[0023] Preferably, in the step of preparing liquid B, the mass concentration of hydrogen peroxide in the liquid B is 30% to 40%.

[0024] Preferably, in the step of preparing liquid B, the mass concentration of the water-soluble strong base in liquid B is 15% to 30%.

[0025] Preferably, the mass concentration of the formic acid aqueous solution is 25% to 45%, the mass ratio of the solid D to the formic acid aqueous solution is 1:(0.2 to 1.0), and the duration of the heating reflux reaction is 1 to 6 hours.

[0026] The main raw materials of the present invention are introduced as follows:

[0027] Methanol: Methanol is often used as a diluent to reduce the concentration of reactants due to its volatility and good solubility. When methanol is used to dilute reactants, it can reduce the concentration of reactants by mixing with the reactants, thereby controlling the reaction rate to a certain extent. In addition, the volatility of methanol makes it easier to remove during the reaction, thereby avoiding unnecessary effects on the final product. This property makes methanol an ideal diluent in certain specific chemical reactions.

[0028] When the concentration of cinnamaldehyde in liquid A is too high, the heat release is intense, the reaction is difficult to control, and the risk of material rushing may occur; when the concentration of cinnamaldehyde in liquid A is too low, the reaction takes a long time. In the present invention, methanol is used to control the concentration of cinnamaldehyde in liquid A.

[0029] Ethyl acetate: Ethyl acetate has excellent dissolving power and is an ideal solvent. Ethyl acetate has high volatility and can evaporate quickly. At the same time, ethyl acetate has low toxicity. In the present invention, when the reaction system generates a large amount of heat in a short time, the rapid volatilization of ethyl acetate can absorb a large amount of heat.

[0030] Compared with the prior art, the advantages of the present invention include:

[0031] (1) The present invention provides a method for preparing phenylacetaldehyde, which uses cinnamaldehyde as a raw material, oxidizes it with hydrogen peroxide, and then heats it under acidic conditions to decarboxylate it to obtain phenylacetaldehyde; methanol and hydrogen peroxide are dissolved in liquid A and liquid B respectively, so as to avoid methanol from contacting hydrogen peroxide too early and reduce the mutual consumption of methanol and hydrogen peroxide;

[0032] (2) In the prior art, methanol and hydrogen peroxide react to produce carbonic acid. At low temperatures, the decomposition rate of carbonic acid slows down, making the reaction environment acidic and increasing side reactions. The method for preparing phenylacetaldehyde provided by the present invention avoids premature contact of methanol with hydrogen peroxide, which is beneficial to reducing the generation of by-products;

[0033] (3) The present invention provides a method for preparing phenylacetaldehyde, in which the reaction mainly occurs at the interface between liquid A and liquid B, and the reaction rate is controllable, thereby avoiding the generation of a large amount of heat in a short time;

[0034] (4) In the method for preparing phenylacetaldehyde provided by the present invention, the reaction occurs at the AB interface, and the reaction rate depends on the area of ​​the AB interface. Using a reaction vessel with a larger cross-section is beneficial to increasing the reaction rate;

[0035] (5) The present invention provides a method for preparing phenylacetaldehyde, wherein the reaction rate can be controlled by adding hydrogen peroxide to liquid B and adjusting the rate of adding hydrogen peroxide. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to understand the characteristics and effects of the present application, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the common meanings understood by those skilled in the art for the present application. In case of conflict, the definitions in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present application in any way, that is, the content of the present application can be implemented without being limited by any specific theory or mechanism.

[0038] As used herein, "this application" means "the present invention" or "the present disclosure".

[0039] The use of "one", "an", "a kind" or similar expressions to describe the components and technical features described in this application is merely for the convenience of expression and to provide a general meaning to the scope of this application. Therefore, such description should be understood to include one or at least one, and the singular also includes the plural, unless it is obvious that it refers to another meaning.

[0040] In this document, "or its combination" means "or any combination thereof", and "any one", "any one" means "any one", "any one" or "any one".

[0041] As used herein, the terms "comprises," "including," "having," "containing," or any other similar terms are open-ended transitional phrases that are intended to cover non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or article. In addition, unless otherwise expressly stated, the term "or" refers to an inclusive "or" rather than an exclusive "or." For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, in this article, the terms "comprising", "including", "having", and "containing" should be interpreted as being specifically disclosed and simultaneously covering closed conjunctions such as "consisting of", "consisting of", and "the remainder is", as well as conjunctions such as "consisting essentially of", "mainly consisting of", "mainly consisting of", "basically containing", "essentially consisting of", "essentially consisting of", and "essentially containing".

[0042] In this article, all features or conditions such as numerical values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions), especially integer values. For example, the range description of "1.0 to 8.0" or "between 1.0 and 8.0" or "between 1.0 and 8.0" should be deemed to have specifically disclosed all sub-ranges such as 1.0 to 8.0, 1.0 to 7.0, 2.0 to 8.0, 2.0 to 6.0, 3.0 to 6.0, 4.0 to 8.0, 3.0 to 8.0, etc., and should be deemed to cover endpoint values, especially sub-ranges defined by integer values, and should be deemed to have specifically disclosed individual values ​​such as 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, etc. Unless otherwise indicated, the foregoing method of interpretation applies to all contents of the entire application, regardless of whether the scope is broad or not.

[0043] If the quantity, concentration or other numerical value or parameter is expressed as a range, a preferred range (or a better range) or a series of upper and lower limits, it should be understood that all ranges consisting of any pair of the upper limit or preferred value (or a better value) of the range and the lower limit or preferred value (or a better value) of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, if a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0044] In this document, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range of 39.50 to 40.49.

[0045] In this article, for the use of Markush groups or optional terms to describe the features or examples of the present application, those skilled in the art should understand that all subgroups or any individual elements in the Markush group or option list can also be used to describe the present application. For example, if X is described as "selected from the group consisting of X1, X2 and X3", it also means that the claim that X is X1 and the claim that X is X1 and / or X2 and / or X3 have been fully described. Furthermore, for the use of Markush groups or optional terms to describe the features or examples of the present application, those skilled in the art should understand that any combination of subgroups or individual members of all elements in the Markush group or option list can also be used to describe the present application. Accordingly, for example, if X is described as "selected from the group consisting of X1, X2 and X3", and Y is described as "selected from the group consisting of Y1, Y2 and Y3", it means that the claim that X is X1 and / or X2 and / or X3 and Y is Y1 and / or Y2 and / or Y3 has been fully described.

[0046] Unless otherwise specified, in this application, a compound refers to a chemical substance formed by two or more elements connected by chemical bonds, including small molecule compounds and polymer compounds, but not limited thereto. The interpretation of a compound in this article is not limited to a single chemical substance, but can also be interpreted as the same type of chemical substances with the same composition or the same properties.

[0047] If not otherwise specified, in this application, polymer refers to the product formed by monomer through polymerization reaction, often including many polymer aggregates, each polymer is formed by many simple structural units repeatedly connected by covalent bonds, and monomer is a compound of synthetic polymer. Polymer can include homopolymer, copolymer, prepolymer, etc., and is not limited to this. Homopolymer refers to a polymer polymerized by a monomer. Copolymer includes random copolymer (structure is such as -AABABBBAAABBA-), alternating copolymer (structure is such as -ABABABAB-), graft copolymer (structure is such as -AA(A-BBBB)AA(A-BBBB)AAA-) and block copolymer (structure is such as -AAA AA-BBBBBB-AAAAA-) etc. Prepolymer refers to a polymer with a lower molecular weight between the monomer and the final polymer, and the prepolymer contains reactive functional groups that can further undergo polymerization reaction to obtain a product with a higher molecular weight that is fully cross-linked or hardened. Polymer certainly includes oligomers, and is not limited to this. Oligomers, also known as low polymers, are polymers composed of 2 to 20 repeating units, usually 2 to 5 repeating units.

[0048] Unless otherwise specified, the "resin" in this application is a customary name for a synthetic polymer, which may include monomers, polymers thereof, combinations of monomers, combinations of polymers thereof, or combinations of monomers and polymers thereof, etc., and is not limited thereto.

[0049] If not otherwise specified, in the present application, modified products include products after modification of reactive functional groups of each resin, products after prepolymerization of each resin with other resins, products after crosslinking of each resin with other resins, products after copolymerization of each resin with other resins, and the like.

[0050] If not otherwise specified, the unsaturated bonds described in the present application refer to reactive unsaturated bonds, such as but not limited to unsaturated double bonds that can undergo cross-linking reactions with other functional groups, such as but not limited to unsaturated carbon-carbon double bonds that can undergo cross-linking reactions with other functional groups.

[0051] The unsaturated carbon-carbon double bonds described in the present application preferably include, but are not limited to, vinyl, vinylbenzyl, (meth)acryloyl, allyl or a combination thereof. Vinyl should be interpreted to include vinyl and vinylidene. (Meth)acryloyl should be interpreted to include acryloyl and methacryloyl.

[0052] Unless otherwise specified, the hydrocarbon groups described in this application include, but are not limited to, alkyl, alkenyl or alkynyl, and include their various isomers when interpreted. For example, a C1-C6 divalent hydrocarbon group is interpreted to include a C1-C6 divalent straight-chain hydrocarbon group, a C2-C6 divalent branched hydrocarbon group or a C3-C6 divalent cyclic hydrocarbon group. For another example, a propyl group should be interpreted to include n-propyl and isopropyl.

[0053] Unless otherwise specified, in this application, parts by weight represent relative parts by weight in a composition, which may be any weight unit, such as but not limited to kilograms, kilograms, grams, pounds, etc. For example, 100 parts by weight of polyphenylene ether resin may represent 100 kilograms of polyphenylene ether resin or 100 pounds of polyphenylene ether resin.

[0054] It should be understood that the features disclosed in the various embodiments herein may be arbitrarily combined to form the technical solution of the present application, as long as there is no contradiction in the combination of these features.

[0055] The present application will be described below with specific implementations and examples. It should be understood that these specific implementations and examples are merely illustrative and are not intended to limit the scope of the present application and its use.

[0056] Unless otherwise stated, the methods, reagents and conditions used in the following preparation examples, comparative examples and examples are conventional methods, reagents and conditions in the art.

[0057] In the following descriptions:

[0058] Cinnamaldehyde: active ingredient content ≥99%;

[0059] Hydrogen peroxide: concentration 50%;

[0060] Formic acid: active ingredient content ≥99%;

[0061] Preparation Example

[0062] Preparation Example 1

[0063] The raw materials used in this preparation example include: 100 g of cinnamaldehyde, 100 g of methanol, and 2000 g of ethyl acetate.

[0064] The preparation method of this preparation example includes:

[0065] Z1. Cool cinnamaldehyde, methanol and ethyl acetate to 0°C;

[0066] Z2. In an ice-water mixture environment, mix cinnamaldehyde, methanol and ethyl acetate evenly to obtain liquid A.

[0067] Preparation Example 2

[0068] The difference between this preparation example and preparation example 1 is that the amount of methanol used is 300 g.

[0069] Preparation Example 3

[0070] The difference between this preparation example and preparation example 1 is that the amount of methanol used is 500 g.

[0071] Table 1 Raw materials used in Preparation Examples 1 to 3

[0072] Preparation Example Preparation Example 1 Preparation Example 2 Preparation Example 3 Cinnamaldehyde 100 100 100 Methanol 100 300 500 Ethyl acetate 2000 2000 2000

[0073] Preparation Example 4

[0074] The raw materials used in this preparation example include: 300 g of sodium hydroxide, 600 g of 50% hydrogen peroxide, and 100 g of deionized water.

[0075] The preparation method of this preparation example comprises: mixing sodium hydroxide, 50% hydrogen peroxide and deionized water and then cooling the mixture to 0° C. to obtain liquid B.

[0076] Preparation Example 5

[0077] The difference between this preparation example and preparation example 4 is: 200 g of sodium hydroxide, 700 g of 50% hydrogen peroxide, and 100 g of deionized water.

[0078] Preparation Example 6

[0079] The difference between this preparation example and preparation example 4 is: 150 g of sodium hydroxide, 800 g of 50% hydrogen peroxide, and 50 g of deionized water.

[0080] Table 2 Raw materials used in Preparation Examples 4 to 6

[0081] Preparation Example Preparation Example 4 Preparation Example 5 Preparation Example 6 Sodium hydroxide 300 200 150 50% Hydrogen Peroxide 600 700 800 Deionized water 100 100 50

[0082] Comparative Example

[0083] Comparative Example 1

[0084] The raw materials used in this comparative example include: 100 g of cinnamaldehyde, 100 g of methanol, 2000 g of ethanol, 100 ml of liquid A obtained in Preparation Example 1, and 100 ml of liquid B obtained in Preparation Example 3.

[0085] The inner diameter of the reaction vessel used in the first reaction in this example is 5 cm.

[0086] The preparation method of this comparative example comprises:

[0087] D1. Cool cinnamaldehyde, methanol and ethanol to 0°C;

[0088] Z2. In an ice-water mixture environment, mix cinnamaldehyde, methanol and ethanol evenly to obtain liquid A.

[0089] D1. First reaction: at 0°C, add 100 ml of liquid A and 100 ml of liquid B into a reaction container and mix them evenly. Use a hydrogen peroxide detector to detect the concentration of hydrogen peroxide in the mixed solution. Add 40% hydrogen peroxide to the mixed solution to adjust the mass concentration of hydrogen peroxide in the mixed solution to 20% to 40%. Stop the reaction when the reading of the hydrogen peroxide detector does not change within 1 minute.

[0090] D2. Remove volatiles: After the first reaction is completed, evaporate the mixed solution at 50°C to volatilize the alcohol to obtain liquid C; filter liquid C at 0°C to obtain solid D;

[0091] D3, mixing solid D with 25% formic acid solution and heating under reflux for reaction, wherein the mass ratio of solid D to the formic acid aqueous solution is 1:0.2, and the heating under reflux for reaction is 6 hours to obtain a reaction solution containing phenylacetaldehyde;

[0092] D4. Purification: solid magnesium hydroxide is added to the reaction solution containing phenylacetaldehyde until the pH is 6.5, and then heated to remove the solvent contained therein, and then filtered. The filtrate is washed with water until neutral and then distilled under reduced pressure and heating conditions to obtain phenylacetaldehyde.

[0093] In this comparative example, the amount of hydrogen peroxide used is 22.3 ml of 40% hydrogen peroxide.

[0094] Example

[0095] Example 1

[0096] The raw materials used in this example include: 100 ml of solution A obtained in Preparation Example 1 and 100 ml of solution B obtained in Preparation Example 4.

[0097] The reaction vessel used in the first reaction in this example has an inner diameter of 5 cm.

[0098] The preparation method of this embodiment includes:

[0099] S1. First reaction: at 0°C, add liquid B into the reaction container, then slowly add liquid A into the upper layer of liquid B, and use a hydrogen peroxide detector to detect the concentration of hydrogen peroxide in the lower layer of liquid B; add 40% hydrogen peroxide to liquid B through a long dropper to adjust the mass concentration of hydrogen peroxide in liquid B to 20% to 40%, and stop the reaction when the reading of the hydrogen peroxide detector does not change within 1 minute, and record the total time of adding hydrogen peroxide;

[0100] S2, removing volatiles: after the first reaction is completed, retain liquid A, evaporate liquid A at 50°C to volatilize methanol, and obtain liquid C; filter liquid C at 0°C to obtain solid D;

[0101] S3, mixing solid D with 25% formic acid solution and heating under reflux for reaction, wherein the mass ratio of solid D to the formic acid aqueous solution is 1:0.2, and the heating under reflux for reaction is 6 hours to obtain a reaction solution containing phenylacetaldehyde;

[0102] S4, purification: adding solid magnesium hydroxide to the reaction solution containing phenylacetaldehyde until the pH is 6.5, heating to remove the solvent contained therein, filtering, washing the filtrate with water until it is neutral, and then distilling under reduced pressure and heating to obtain phenylacetaldehyde.

[0103] In this embodiment, the amount of hydrogen peroxide used is 16.6 ml of 40% hydrogen peroxide, and the time for adding hydrogen peroxide is 1.2 hours.

[0104] Example 2

[0105] The difference between this embodiment and embodiment 1 is that: liquid A comes from preparation example 2, the amount of liquid B used is 300 ml, and liquid B comes from preparation example 5; the concentration of formic acid in step S3 is 35%, the mass ratio of solid D to the formic acid aqueous solution is 1:0.6, and the heating reflux reaction time is 3 hours.

[0106] Example 3

[0107] The difference between this embodiment and embodiment 1 is that: liquid A comes from preparation example 3, the amount of liquid B used is 500 ml, and liquid B comes from preparation example 6; the concentration of formic acid in step S3 is 45%, the mass ratio of solid D to the formic acid aqueous solution is 1:1, and the heating reflux reaction time is 1 hour.

[0108] Example 4

[0109] The difference between this embodiment and embodiment 1 is that the inner diameter of the reaction container used in the first reaction is 10 cm.

[0110] In this embodiment, the duration of adding hydrogen peroxide is 1.1 h.

[0111] Example 5

[0112] The difference between this embodiment and embodiment 1 is that the inner diameter of the reaction container used in the first reaction is 15 cm.

[0113] In this embodiment, the duration of adding hydrogen peroxide is 0.8h.

[0114] Experimental Results

[0115] By comparing Example 1 with Comparative Example 1, it can be seen that the amount of hydrogen peroxide used in Example 1 is less than that in Comparative Example 1. The possible reason is that in Example 1, methanol and hydrogen peroxide are dissolved in liquid A and liquid B respectively, which prevents methanol from contacting hydrogen peroxide too early and reduces the mutual consumption of methanol and hydrogen peroxide.

[0116] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, some simple deductions or substitutions can be made without departing from the concept of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing phenylacetaldehyde, characterized in that, The steps include: Preparation of liquid A: dissolving cinnamaldehyde and methanol in a light solvent to obtain liquid A, wherein the light solvent is insoluble in water, and the density and boiling point of the light solvent are both lower than those of water; Preparation of liquid B: prepare liquid B by mixing water-soluble strong alkali and hydrogen peroxide with water; First reaction: at 0-5°C, liquid A is slowly added to the upper layer of liquid B to separate liquid A and liquid B; hydrogen peroxide is added to the liquid B to adjust the mass concentration of hydrogen peroxide in the liquid B to be maintained at 20%-40%, and the reaction is stopped when the concentration of hydrogen peroxide in the liquid B tends to be stable; Remove volatiles: After the reaction is completed, keep liquid A, evaporate liquid A at 40-60°C to volatilize methanol, and obtain liquid C; filter liquid C at 0-5°C to obtain solid D; Second reaction: Solid D is mixed with aqueous formic acid solution and then heated under reflux to react, thereby obtaining a reaction solution containing phenylacetaldehyde.

2. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: The method also includes purification: adding solid magnesium hydroxide to the reaction solution containing phenylacetaldehyde until the pH value is 6-7, filtering, washing the filtrate with water until it is neutral, then desolventizing and distilling to obtain phenylacetaldehyde.

3. A method for preparing phenylacetaldehyde according to claim 2, characterized in that: The distillation step is achieved by distillation under reduced pressure.

4. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: In the step of preparing liquid A, the mass ratio of the cinnamaldehyde to the methanol is 1:(1-5).

5. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: The volume ratio of the A liquid to the B liquid is 1:(0.1-0.5).

6. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: In the step of preparing liquid A, the light solvent is selected from one or more of benzene, ethyl acetate, ether and cyclohexane.

7. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: In the step of preparing liquid B, the water-soluble strong base is selected from one or more of sodium hydroxide and potassium hydroxide.

8. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: In the step of preparing liquid B, the mass concentration of hydrogen peroxide in the liquid B is 30% to 40%.

9. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: In the step of preparing liquid B, the mass concentration of the water-soluble strong base in liquid B is 15% to 30%.

10. A method for preparing phenylacetaldehyde according to claim 1, characterized in that: The formic acid aqueous solution The mass concentration of the solid D is 25% to 45%, the mass ratio of the solid D to the formic acid aqueous solution is 1: (0.2 to 1.0), The heating reflux reaction time is 1 to 6 hours.