Synthetic method of methyl heptenone

Abstract

The invention relates to the field of chemical engineering, in particular to a synthetic method of methyl heptenone. Comprising the following steps: preparing a high-efficiency catalyst; activating the methyl acetoacetate; the invention relates to condensation of activated methyl acetoacetate and 2-methyl-3-butene-2-ol. According to the method, methyl acetoacetate is activated through a lewis acid catalyst aluminum isopropoxide, coordination can be formed between the aluminum isopropoxide and carbonyl oxygen of methyl acetoacetate, the electron density of carbonyl is reduced, the alkylation reaction of methyl acetoacetate can be catalyzed subsequently, and the yield of methyl acetoacetate is increased. The methyl acetoacetate is more easily used as a nucleophilic reagent to be subjected to a condensation reaction with 2-methyl-3-butene-2-alcohol which subsequently provides an alkyl group to generate a new C-C bond, so that synthesis of a methyl heptenone precursor is promoted in a dropwise adding heat preservation reaction, and the methyl heptenone precursor is converted into methyl heptenone in a subsequent rectification process; the generation of by-products is reduced, so that the purity of the methyl heptenone is improved, and the yield of the methyl heptenone is also improved.

Description

Technical Field

[0001] The present invention relates to the chemical industry field, and particularly to a method for synthesizing methyl heptenone. Background Art

[0002] Methyl heptenone is a colorless or light yellow liquid with a fresh fruity aroma and can be used as a food flavor. However, due to its strong chemical reaction ability and the ability to derive various products, it is usually used as an important organic intermediate in the fragrance and medical fields.

[0003] The main synthesis routes of methyl heptenone include the acetylene-acetone method, the isobutene method, and the isoprene method. The acetylene-acetone method uses acetone as the starting material, acetylene adds to acetone to obtain alkynol, then reduces to obtain enol, and the enol undergoes Carroll rearrangement reaction to obtain methyl heptenone. This route requires acetylene, with poor atom economy and more three wastes. The isobutene method uses isobutene, acetone, and formaldehyde as raw materials to first synthesize α-methyl heptenone by heating and pressurization, and then obtain methyl heptenone under the action of iron carbonyl catalyst. Its cost is low but there are many by-products, with difficult separation and low purity of the obtained methyl heptenone. The isoprene method uses isoprene as the raw material, first undergoes hydrogen chloride addition to obtain isopentenyl chloride, and then isopentenyl chloride condenses with acetone to obtain methyl heptenone. Although isoprene raw materials are cheap and available, the condensation ability of isopentenyl chloride and acetone is poor, resulting in low yield of methyl heptenone. Summary of the Invention

[0004] In order to solve the above technical defects, the present invention has developed a method for synthesizing methyl heptenone, which can make full use of reaction raw materials, reduce the generation of by-products, and obtain methyl heptenone with high purity and high yield.

[0005] A method for synthesizing methyl heptenone includes the following steps:

[0006] S1: Preparation of highly efficient catalyst

[0007] Dissolve the mixture of tetrabutylammonium hydroxide, Mg(NO 3 ) 2 and TiCl 4 and tetraethylammonium fluoride in different portions of solvents respectively to obtain solution A, solution B, and solution C. Under stirring, slowly drop solution B into solution A, then keep stirring and slowly drop in solution C, and then transfer to a high-pressure reactor for heating. After uniformly cooling to room temperature, perform centrifugal separation to obtain solid particles. Place the solid particles in a tubular furnace, uniformly heat up in an air atmosphere, then perform heat preservation calcination, cool to room temperature, and then uniformly heat up in a reducing atmosphere and perform heat preservation reduction calcination to obtain a Ti-MgF 2 highly efficient catalyst;

[0008] S2: Activation of methyl acetoacetate

[0009] Putting isopropanol in a reaction kettle, then adding aluminum isopropoxide and tannic acid, stirring and heating until the solid matter is completely dissolved, then cooling to room temperature to obtain an activated solution, adding methyl acetoacetate from a high-level tank into the reaction kettle and mixing with the activated solution, stirring and heating, and then keeping warm to obtain activated methyl acetoacetate;

[0010] S3: Condensation of activated methyl acetoacetate with 2-methyl-3-butene-2-ol

[0011] Activated methyl acetoacetate, molecular sieve and Ti-MgF 2 A high-efficiency catalyst is placed in a reaction kettle and heated, and then 2-methyl-3-butene-2-ol is added dropwise while being refluxed and taken out, and after the addition is completed, the reaction is kept warm, and then sampling is performed for chromatographic analysis. After the reaction is completed, the reaction is cooled to room temperature, and then the material is discharged and filtered to obtain a crude reaction product, and the crude reaction product is transferred to a crude distillation kettle for distillation, and after cooling, it is transferred to a rectification kettle, the vacuum degree is adjusted, and a falling film circulation heater of the rectification tower is turned on, and the fractions are collected to obtain methyl heptenone.

[0012] Furthermore, the preparation of the high-efficiency catalyst in step S1 comprises the following steps:

[0013] S1.1: Add 1.5-2 parts by weight of tetrabutylammonium hydroxide to a container containing 100-120 parts by weight of solvent, stir for 25-30 minutes to completely dissolve the tetrabutylammonium hydroxide to obtain solution A, and add 0.8-1 parts by weight of Mg(NO 3 ) 2 and 0.1-0.2 parts by weight of TiCl 4 The mixture is placed in a container, and then 20-25 parts by weight of a solvent is added and stirred until the solid matter is completely dissolved to obtain a solution B. 0.2-0.3 parts by weight of tetraethylamine fluoride is placed in a container, and 15-20 parts by weight of a solvent is added and stirred to dissolve to obtain a solution C.

[0014] S1.2: Slowly drop solution B into solution A while stirring at room temperature for 1-1.5 hours, then slowly drop solution C, continue stirring at room temperature during the dropping process for 1.5-2 hours, then transfer to an autoclave and place in an oven, heat at 95-100°C for 12-15 hours, then cool to room temperature at a rate of 6-8°C / h, then centrifuge to obtain solid particles;

[0015] S1.3: The solid particles obtained in step S2.2 are placed in a tube furnace, heated to 500-550°C at a heating rate of 3-5°C / min in an air atmosphere, and then maintained at the temperature for calcination for 4-5 hours. After cooling to room temperature, the solid particles are heated to 550-600°C at a heating rate of 5-6°C / min in a reducing atmosphere, and maintained at the temperature for reduction calcination for 2-3 hours to obtain Ti-MgF 2 Highly efficient catalyst.

[0016] Further, step S2, the activation of methyl acetoacetate, comprises the following steps:

[0017] S2.1: 4-5 parts by weight of isopropanol are placed in a reaction kettle, and then 1-1.5 parts by weight of aluminum isopropoxide and 0.2-0.3 parts by weight of tannic acid are added, and heated to 60-65° C. while stirring, and the temperature is maintained until the solid matter is completely dissolved, and then naturally cooled to room temperature to obtain an activation solution;

[0018] S2.2: 50-60 parts by weight of methyl acetoacetate is added from the header tank into the reactor and mixed with the activation solution. After stirring for 25-30 minutes, the reactor is heated to a temperature of 80-85° C. The stirring is continued and the temperature is kept at this temperature for 30-40 minutes to obtain activated methyl acetoacetate.

[0019] Further, step S3 activates the condensation of methyl acetoacetate and 2-methyl-3-butene-2-ol, comprising the following steps:

[0020] S3.1: The activated methyl acetoacetate prepared in step S2.2, 0.4-0.5 parts by weight of molecular sieve and 0.3-0.4 parts by weight of Ti-MgF 2 The high-efficiency catalyst is placed in a reaction kettle, the temperature in the kettle is heated to 120-130°C, and then 40-45 parts by weight of 2-methyl-3-butene-2-ol is added dropwise, and reflux and extraction are performed while dropping. The dropping time is controlled to be 12-14 hours. After the dropping is completed, the reaction is kept warm for 2-3 hours, and then sampling is performed for chromatographic analysis. After the reaction is completed, it is naturally cooled to room temperature, and then the material is discharged. When the material is discharged, the molecular sieve and Ti-MgF 2 Highly efficient catalyst to obtain the crude product;

[0021] S3.2: The crude reaction product is transferred to a crude distillation kettle, heated at 80-100°C for 2-3 hours under normal pressure, then cooled and transferred to a distillation kettle, the vacuum degree is adjusted to 2-2.4 kPa, and then the falling film circulation heater of the distillation tower is turned on, and the fraction at 73-75°C is collected to obtain methyl heptenone.

[0022] Furthermore, the solvents in step S1.1 are all anhydrous ethanol.

[0023] Furthermore, in the reducing atmosphere of step S1.3, H 2 The volume fraction ratio of Ar is 1:(9-10).

[0024] Furthermore, the component of the molecular sieve in step S3.1 is hydrated aluminosilicate microporous crystals.

[0025] Furthermore, during the process of dropwise adding 2-methyl-3-butene-2-ol in step S3.1, the temperature in the reactor is maintained at 125-140°C and the top temperature of the tower is maintained at 40-60°C.

[0026] Furthermore, the reaction in step S3.1 is completed with the main product content being greater than 80%, and methyl acetoacetate being less than 1%.

[0027] Furthermore, the distillation kettle in step S3.2 is equipped with a three-stage vacuum pump and a falling film circulation heater, the top of the tower is equipped with a primary water cooling, a secondary refrigeration cooling system and a receiving tank, and the top of the receiving tank is equipped with a low-temperature condenser.

[0028] The beneficial effects are as follows: 1. In the present invention, methyl acetoacetate is first activated by using a Lewis acid catalyst aluminum isopropoxide, which can not only form coordination with the carbonyl oxygen of methyl acetoacetate to reduce the electron density of the carbonyl group, but also catalyze the subsequent alkylation reaction of methyl acetoacetate, so that methyl acetoacetate is more easily used as a nucleophilic reagent to undergo a condensation reaction with 2-methyl-3-butene-2-ol that subsequently provides an alkyl group to generate a new CC bond, thereby promoting the synthesis of a methyl heptenone precursor in a dropwise addition and heat preservation reaction, and converting the methyl heptenone precursor into methyl heptenone in a subsequent distillation process, reducing the generation of by-products, thereby improving the purity of the methyl heptenone, and also improving the yield of the methyl heptenone.

[0029] 2. The present invention first prepares a solution A containing tetrabutylammonium hydroxide, containing Mg(NO 3 ) 2 and TiCl 4 Solution B and solution C containing tetraethylammonium fluoride are added to solution A in turn, and the mixture is placed in a high-pressure reactor for a temperature-raising reaction. In this process, the generated Ti nanosheets are highly dispersed in the MgF 2 The surface of the carrier is formed so that the obtained solid particles form a uniform microsphere layered structure, and then calcined in an air atmosphere to oxidize the Ti nanosheets into TiO 2 Nanosheets, and then TiO 2 The reduction of nanosheets into Ti nanosheets not only enhances the interaction between Ti and the carrier, but also obtains Ti-MgF nanosheets with smaller particle size, higher dispersion and three-dimensional layered microsphere structure. 2The high-efficiency catalyst exposes more active sites of the catalyst, and has excellent catalytic performance in the subsequent condensation reaction of activated methyl acetoacetate and 2-methyl-3-butene-2-ol, which greatly improves the efficiency of the overall reaction, increases the yield of methyl heptenone, and avoids the waste of reaction raw materials.

[0030] 3. The present invention is prepared by dissolving aluminum isopropoxide and tannic acid in isopropanol and then heating the mixture. During the process, the phenolic hydroxyl group of the tannic acid coordinates with the aluminum isopropoxide, so that the Lewis acidity of the aluminum isopropoxide is enhanced to obtain an activated solution. In the subsequent process of co-heating and stirring methyl acetoacetate with the activated solution, the aluminum isopropoxide with enhanced Lewis acidity can more strongly carry out oxygen coordination with the carbonyl group of methyl acetoacetate, and the tannic acid in the activated solution can form a hydrogen bond network with the carbonyl oxygen of methyl acetoacetate through a plurality of phenolic hydroxyl groups. Under the synergistic effect of the hydrogen bond network and the strong oxygen coordination of the aluminum isopropoxide, the electron cloud density of the carbonyl group of methyl acetoacetate can be further reduced, so that the reaction transition state of the subsequent condensation reaction is stabilized, the reaction energy barrier is reduced, the reaction efficiency is improved, and the generation of by-products is reduced, thereby improving the yield and purity of methyl heptenone. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a process flow chart of the synthesis method of methyl heptenone used in the embodiments of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] A synthetic method of methyl heptenone, such as Figure 1 As shown, the following steps are included:

[0035] S1: Preparation of efficient catalysts

[0036] S1.1: Add 1.5 parts by weight of tetrabutylammonium hydroxide to a container containing 100 parts by weight of anhydrous ethanol, stir for 25 minutes to completely dissolve the tetrabutylammonium hydroxide to obtain solution A, and add 0.8 parts by weight of Mg(NO 3 ) 2 and 0.1 parts by weight of TiCl 4The mixture was placed in a container, and then 20 parts by weight of anhydrous ethanol was added and stirred until the solid matter was completely dissolved to obtain a solution B. 0.2 parts by weight of tetraethylammonium fluoride was placed in a container, and 15 parts by weight of anhydrous ethanol was added and stirred to dissolve to obtain a solution C.

[0037] S1.2: slowly drop solution B into solution A while stirring at room temperature for 1 hour, then slowly drop solution C into solution A, continue stirring at room temperature during the dropping process for 1.5 hours, then transfer to an autoclave and place in an oven, heat at 95°C for 12 hours, then cool to room temperature at a rate of 6°C / h, then centrifuge to obtain solid particles;

[0038] S1.3: The solid particles obtained in step S2.2 are placed in a tube furnace, heated to 500°C at a heating rate of 3°C / min in an air atmosphere, and then maintained at the temperature for calcination for 4 hours. After cooling to room temperature, the solid particles are heated to 550°C at a heating rate of 5°C / min in a reducing atmosphere, wherein the reducing atmosphere contains H 2 The volume fraction ratio of Ar was 1:9, and the Ti-MgF 2 Highly efficient catalyst.

[0039] S2: Activation of methyl acetoacetate

[0040] S2.1: 4 parts by weight of isopropanol are placed in a reaction kettle, and then 1 part by weight of aluminum isopropoxide and 0.2 parts by weight of tannic acid are added, and the mixture is heated to 60° C. while stirring, and the temperature is maintained until the solid matter is completely dissolved, and then naturally cooled to room temperature to obtain an activation solution;

[0041] S2.2: 50 parts by weight of methyl acetoacetate is added from the header tank into the reactor and mixed with the activation solution. After stirring for 25 minutes, the reactor is heated to a temperature of 80° C. The stirring is continued and the temperature is kept at this temperature for 30 minutes to obtain activated methyl acetoacetate.

[0042] S3: Condensation of activated methyl acetoacetate with 2-methyl-3-butene-2-ol

[0043] S3.1: The activated methyl acetoacetate prepared in step S2.2, 0.4 parts by weight of hydrated aluminosilicate microporous crystals and 0.3 parts by weight of Ti-MgF 2The high-efficiency catalyst is placed in a reaction kettle, the temperature in the kettle is heated to 120°C, and then 40 parts by weight of 2-methyl-3-butene-2-ol is dripped, and reflux and extraction are performed while dripping, the temperature in the reaction kettle is maintained at 125°C, the top temperature of the tower is maintained at 40°C, the dripping time is controlled within 12 hours, and the temperature is kept for 2 hours after the dripping is completed, and then sampling is performed for chromatographic analysis. When the content of the main product is greater than 80% and the content of methyl acetoacetate is less than 1%, the reaction is completed, and then the reaction is naturally cooled to room temperature, and then the material is discharged, and the molecular sieve and Ti-MgF are filtered out during the discharge. 2 Highly efficient catalyst to obtain the crude product;

[0044] S3.2: The crude reaction product is transferred to a crude distillation kettle, heated at 80°C for 2 hours under normal pressure, then cooled and transferred to a distillation kettle, which is equipped with a three-stage vacuum pump and a falling film circulation heater. The top of the tower is equipped with a primary water cooling, a secondary refrigeration cooling system and a receiving tank. The top of the receiving tank is equipped with a low-temperature condenser. The vacuum degree is adjusted to 2kPa, and then the falling film circulation heater of the distillation tower is turned on to collect the 73°C fraction to obtain methyl heptenone.

[0045] Example 2

[0046] A synthetic method of methyl heptenone, such as Figure 1 As shown, the following steps are included:

[0047] S1: Preparation of efficient catalysts

[0048] S1.1: Add 2 parts by weight of tetrabutylammonium hydroxide to a container containing 120 parts by weight of anhydrous ethanol and stir for 25 minutes to completely dissolve the tetrabutylammonium hydroxide to obtain solution A. Add 1 part by weight of Mg(NO 3 ) 2 and 0.2 parts by weight of TiCl 4 The mixture was placed in a container, and then 25 parts by weight of anhydrous ethanol was added and stirred until the solid matter was completely dissolved to obtain a solution B. 0.3 parts by weight of tetraethylammonium fluoride was placed in a container, and 20 parts by weight of anhydrous ethanol was added and stirred to dissolve to obtain a solution C.

[0049] S1.2: slowly drop solution B into solution A while stirring at room temperature for 1 hour, then slowly drop solution C into solution A, continue stirring at room temperature during the dropping process for 1.5 hours, then transfer to an autoclave and place in an oven, heat at 95°C for 12 hours, then cool to room temperature at a rate of 6°C / h, then centrifuge to obtain solid particles;

[0050] S1.3: The solid particles obtained in step S2.2 are placed in a tube furnace, heated to 500°C at a heating rate of 3°C / min in an air atmosphere, and then maintained at the temperature for calcination for 4 hours. After cooling to room temperature, the solid particles are heated to 550°C at a heating rate of 5°C / min in a reducing atmosphere, wherein the reducing atmosphere contains H 2 The volume fraction ratio of Ar was 1:9, and the Ti-MgF 2 Highly efficient catalyst.

[0051] S2: Activation of methyl acetoacetate

[0052] S2.1: 5 parts by weight of isopropanol are placed in a reaction kettle, and then 1.5 parts by weight of aluminum isopropoxide and 0.3 parts by weight of tannic acid are added, and the mixture is heated to 60° C. while stirring, and the temperature is maintained until the solid matter is completely dissolved, and then naturally cooled to room temperature to obtain an activation solution;

[0053] S2.2: 60 parts by weight of methyl acetoacetate was added from the header tank into the reactor and mixed with the activation solution. After stirring for 25 minutes, the reactor was heated to a temperature of 80° C. The stirring was continued and the temperature was kept at this temperature for 30 minutes to obtain activated methyl acetoacetate.

[0054] S3: Condensation of activated methyl acetoacetate with 2-methyl-3-butene-2-ol

[0055] S3.1: The activated methyl acetoacetate prepared in step S2.2, 0.5 parts by weight of hydrated aluminosilicate microporous crystals and 0.4 parts by weight of Ti-MgF 2 The high-efficiency catalyst is placed in a reaction kettle, the temperature in the kettle is heated to 120°C, and then 45 parts by weight of 2-methyl-3-butene-2-ol is dripped, and reflux and extraction are performed while dripping, the temperature in the reaction kettle is maintained at 125°C, the top temperature of the tower is maintained at 40°C, the dripping time is controlled within 12 hours, and the temperature is kept for 2 hours after the dripping is completed, and then sampling is performed for chromatographic analysis. When the content of the main product is greater than 80% and the content of methyl acetoacetate is less than 1%, the reaction is completed, and then the reaction is naturally cooled to room temperature, and then the material is discharged, and the molecular sieve and Ti-MgF are filtered out during the discharge. 2 Highly efficient catalyst to obtain the crude product;

[0056] S3.2: The crude reaction product is transferred to a crude distillation kettle, heated at 80°C for 2 hours under normal pressure, then cooled and transferred to a distillation kettle, which is equipped with a three-stage vacuum pump and a falling film circulation heater. The top of the tower is equipped with a primary water cooling, a secondary refrigeration cooling system and a receiving tank. The top of the receiving tank is equipped with a low-temperature condenser. The vacuum degree is adjusted to 2kPa, and then the falling film circulation heater of the distillation tower is turned on to collect the 73°C fraction to obtain methyl heptenone.

[0057] Example 3

[0058] A synthetic method of methyl heptenone, such as Figure 1 As shown, the following steps are included:

[0059] S1: Preparation of efficient catalysts

[0060] S1.1: Add 1.5 parts by weight of tetrabutylammonium hydroxide to a container containing 100 parts by weight of anhydrous ethanol, stir for 30 minutes to completely dissolve the tetrabutylammonium hydroxide to obtain solution A, and add 0.8 parts by weight of Mg(NO 3 ) 2 and 0.1 parts by weight of TiCl 4 The mixture was placed in a container, and then 20 parts by weight of anhydrous ethanol was added and stirred until the solid matter was completely dissolved to obtain a solution B. 0.2 parts by weight of tetraethylammonium fluoride was placed in a container, and 15 parts by weight of anhydrous ethanol was added and stirred to dissolve to obtain a solution C.

[0061] S1.2: Slowly drop solution B into solution A while stirring at room temperature for 1.5 hours, then slowly drop solution C, continue stirring at room temperature during the dropping process for 2 hours, then transfer to an autoclave and place in an oven, heat at 100°C for 15 hours, then cool to room temperature at a cooling rate of 8°C / h, and then centrifuge to obtain solid particles;

[0062] S1.3: The solid particles obtained in step S2.2 are placed in a tube furnace, heated to 550°C at a heating rate of 5°C / min in an air atmosphere, and then maintained at the temperature for calcination for 4 hours. After cooling to room temperature, the solid particles are heated to 600°C at a heating rate of 6°C / min in a reducing atmosphere, wherein the reducing atmosphere contains H 2 The volume fraction ratio of Ar was 1:10, and the Ti-MgF 2 Highly efficient catalyst.

[0063] S2: Activation of methyl acetoacetate

[0064] S2.1: 4 parts by weight of isopropanol are placed in a reaction kettle, and then 1 part by weight of aluminum isopropoxide and 0.2 parts by weight of tannic acid are added, and the mixture is heated to 65° C. while stirring, and the temperature is maintained until the solid matter is completely dissolved, and then naturally cooled to room temperature to obtain an activation solution;

[0065] S2.2: 50 parts by weight of methyl acetoacetate was added from the header tank into the reactor and mixed with the activation solution. After stirring for 30 minutes, the reactor was heated to a temperature of 85° C. The stirring was continued and the temperature was kept at this temperature for 40 minutes to obtain activated methyl acetoacetate.

[0066] S3: Condensation of activated methyl acetoacetate with 2-methyl-3-butene-2-ol

[0067] S3.1: The activated methyl acetoacetate prepared in step S2.2, 0.4 parts by weight of hydrated aluminosilicate microporous crystals and 0.3 parts by weight of Ti-MgF 2 The high-efficiency catalyst is placed in a reaction kettle, the temperature in the kettle is heated to 130°C, and then 45 parts by weight of 2-methyl-3-butene-2-ol is dripped, and reflux and extraction are performed while dripping, the temperature in the reaction kettle is maintained at 140°C, the top temperature of the tower is maintained at 60°C, the dripping time is controlled at 14 hours, and the temperature is kept for 3 hours after the dripping is completed, and then sampling is performed for chromatographic analysis. When the content of the main product is greater than 80% and the content of methyl acetoacetate is less than 1%, the reaction is completed, and then the reaction is naturally cooled to room temperature, and then the material is discharged, and the molecular sieve and Ti-MgF are filtered out during the discharge. 2 Highly efficient catalyst to obtain the crude product;

[0068] S3.2: The crude reaction product is transferred to a crude distillation kettle, heated at 100°C for 3 hours under normal pressure, then cooled and transferred to a distillation kettle, which is equipped with a three-stage vacuum pump and a falling film circulation heater. The top of the tower is equipped with a primary water cooling, a secondary refrigeration cooling system and a receiving tank. The top of the receiving tank is equipped with a low-temperature condenser. The vacuum degree is adjusted to 2.4 kPa, and then the falling film circulation heater of the distillation tower is turned on to collect the 75°C fraction to obtain methyl heptenone.

[0069] Comparative Example 1

[0070] Compared with Example 1, the difference of Comparative Example 1 is that step S1 is removed in Comparative Example 1, and Ti-MgF is not added in step S3.1. 2 The remaining steps are the same as those in Example 1, and the obtained methyl heptenone is recorded as Comparative Example 1.

[0071] Comparative Example 2

[0072] Compared with Example 1, the difference of Comparative Example 2 is that tannic acid is not added in step S2.1 of Comparative Example 2, and the remaining steps are the same as those of Example 1. The obtained methyl heptenone is recorded as Comparative Example 2.

[0073] Comparative Example 3

[0074] Compared with Example 1, the difference of Comparative Example 3 is that aluminum isopropoxide is not added in step S3.1 of Comparative Example 3, and the remaining steps are the same as those of Example 1. The obtained methyl heptenone is recorded as Comparative Example 3.

[0075] Experiment 1: Take 60 g of 2-methyl-3-buten-2-ol from the same batch, and then divide it into 6 equal parts. The preparation of methylheptenone is carried out through the processes of Examples 1-3 and Comparative Examples 1-3 respectively. After weighing, the purity of the methylheptenone prepared in Examples 1-3 and Comparative Examples 1-3 is measured by gas chromatography-mass spectrometry. The methylheptenone yield = (mass × purity) / theoretical yield × 100%. Calculate and record the data to form a table as shown in Table 1. It can be seen that the purity of the methylheptenone prepared in Examples 1-3 is greater than that of Comparative Example 1 and Comparative Example 3, and it can also be seen that the yield of the methylheptenone prepared in Examples 1-3 is greater than that of the methylheptenone prepared in Comparative Examples 1-3. It can be proved that the process of the examples can not only reduce the generation of by-products and improve the purity of methylheptenone, but also improve the yield of methylheptenone. At the same time, it can be proved that the preparation of Ti-MgF 2 The high-efficiency catalyst can improve the reaction efficiency, thereby increasing the yield of methylheptenone. According to Table 1, it can also be seen that the yields of Comparative Example 2 and Comparative Example 3 are not much different but are both less than the yield of methylheptenone in Example 1. It can be proved that there is a synergistic effect between aluminum isopropoxide and tannic acid, which can produce an effect of 1 + 1 > 2, thereby increasing the yield and purity of methylheptenone.

[0076] Table 1: Mass, purity and yield of methylheptenone

[0077] Methyl heptenone mass / g Purity of methyl heptenone / % Methyl heptenone yield / % Example 1 14.7 94.5 93.4 Example 2 14.59 94.1 92.8 Example 3 14.84 93.8 94.1 Comparative Example 1 13.88 85.2 79.7 Comparative Example 2 14.32 86.4 83.6 Comparative Example 3 14.41 83.5 81.3

[0078] The above examples are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above examples without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for synthesizing methyl heptenone, characterized in that: The following steps are involved: S1: Preparation of efficient catalysts A mixture of tetrabutylammonium hydroxide, Mg(NO3)2 and TiCl4 and tetraethylammonium fluoride are dissolved in different portions of solvent to obtain solution A, solution B and solution C respectively; solution B is slowly added dropwise to solution A under stirring; solution C is then slowly added dropwise while stirring is maintained; the mixture is transferred to a high-pressure reactor for heating; the mixture is cooled to room temperature at a uniform rate and then centrifuged to obtain solid particles; the solid particles are placed in a tubular furnace, the temperature is uniformly increased in an air atmosphere, and then the mixture is heat-insulated and calcined; after cooling to room temperature, the temperature is uniformly increased in a reducing atmosphere and the mixture is heat-insulated and reduced to obtain a Ti-MgF2 high-efficiency catalyst; S2: Activation of methyl acetoacetate Putting isopropanol in a reaction kettle, then adding aluminum isopropoxide and tannic acid, stirring and heating until the solid matter is completely dissolved, then cooling to room temperature to obtain an activated solution, adding methyl acetoacetate from a high-level tank into the reaction kettle and mixing with the activated solution, stirring and heating, and then keeping warm to obtain activated methyl acetoacetate; S3: Condensation of activated methyl acetoacetate with 2-methyl-3-butene-2-ol Activated methyl acetoacetate, molecular sieve and Ti-MgF2 high-efficiency catalyst are placed in a reaction kettle and heated, and then 2-methyl-3-butene-2-ol is added dropwise while refluxing and withdrawing. After the addition is completed, the reaction is kept warm and then sampled for chromatographic analysis. After the reaction is completed, the reaction is cooled to room temperature, and then discharged and filtered to obtain a crude reaction product. The crude reaction product is transferred to a crude distillation kettle for distillation, and after cooling, it is transferred to a rectification kettle, the vacuum degree is adjusted, and the falling film circulation heater of the rectification tower is turned on to collect the fractions to obtain methyl heptenone.

2. The method for synthesizing methyl heptenone according to claim 1, characterized in that: Step S1: Preparation of a high-efficiency catalyst, comprising the following steps: S1.1: 1.5-2 parts by weight of tetrabutylammonium hydroxide is added to a container containing 100-120 parts by weight of a solvent, and stirred for 25-30 minutes to completely dissolve the tetrabutylammonium hydroxide to obtain a solution A; 0.8-1 parts by weight of Mg(NO3)2 and 0.1-0.2 parts by weight of TiCl4 are mixed and placed in a container, and then 20-25 parts by weight of a solvent are added and stirred until the solid matter is completely dissolved to obtain a solution B; 0.2-0.3 parts by weight of tetraethylammonium fluoride is placed in a container, and 15-20 parts by weight of a solvent are added and stirred to dissolve to obtain a solution C; S1.2: Slowly drop solution B into solution A while stirring at room temperature for 1-1.5 hours, then slowly drop solution C, continue stirring at room temperature during the dropping process for 1.5-2 hours, then transfer to an autoclave and place in an oven, heat at 95-100°C for 12-15 hours, then cool to room temperature at a rate of 6-8°C / h, then centrifuge to obtain solid particles; S1.3: The solid particles obtained in step S2.2 are placed in a tubular furnace, heated to 500-550°C at a heating rate of 3-5°C / min in an air atmosphere, and then calcined at the temperature for 4-5 hours. After cooling to room temperature, the solid particles are heated to 550-600°C at a heating rate of 5-6°C / min in a reducing atmosphere, and reduced and calcined for 2-3 hours to obtain a Ti-MgF2 high-efficiency catalyst.

3. The method for synthesizing methyl heptenone according to claim 1, characterized in that: Step S2: Activation of methyl acetoacetate, comprising the following steps: S2.1: 4-5 parts by weight of isopropanol are placed in a reaction kettle, and then 1-1.5 parts by weight of aluminum isopropoxide and 0.2-0.3 parts by weight of tannic acid are added, and heated to 60-65° C. while stirring, and the temperature is maintained until the solid matter is completely dissolved, and then naturally cooled to room temperature to obtain an activation solution; S2.2: 50-60 parts by weight of methyl acetoacetate is added from the header tank into the reactor and mixed with the activation solution. After stirring for 25-30 minutes, the reactor is heated to a temperature of 80-85° C. The stirring is continued and the temperature is kept at this temperature for 30-40 minutes to obtain activated methyl acetoacetate.

4. The method for synthesizing methyl heptenone according to claim 1, characterized in that: Step S3 activates the condensation of methyl acetoacetate and 2-methyl-3-butene-2-ol, comprising the following steps: S3.1: Place the activated methyl acetoacetate obtained in step S2.2, 0.4-0.5 parts by weight of molecular sieve and 0.3-0.4 parts by weight of Ti-MgF2 high-efficiency catalyst in a reaction kettle, heat the temperature in the kettle to 120-130°C, then drop 40-45 parts by weight of 2-methyl-3-butene-2-ol, reflux and extract while dropping, the dropping time is controlled to 12-14 hours, keep the temperature for reaction for 2-3 hours after the dropping is completed, then take samples for chromatographic analysis, cool naturally to room temperature after the reaction is completed, and then discharge, filter out the molecular sieve and Ti-MgF2 high-efficiency catalyst during the discharge, and obtain a crude reaction product; S3.2: The crude reaction product is transferred to a crude distillation kettle, heated at 80-100°C for 2-3 hours under normal pressure, then cooled and transferred to a distillation kettle, the vacuum degree is adjusted to 2-2.4 kPa, and then the falling film circulation heater of the distillation tower is turned on, and the fraction at 73-75°C is collected to obtain methyl heptenone.

5. The method for synthesizing methyl heptenone according to claim 2, characterized in that: The solvent in step S1.1 is all anhydrous ethanol.

6. The method for synthesizing methyl heptenone according to claim 2, characterized in that: The volume fraction ratio of H2 and Ar in the reducing atmosphere of step S1.3 is 1:(9-10).

7. The method for synthesizing methyl heptenone according to claim 4, characterized in that: The component of the molecular sieve in step S3.1 is hydrated aluminosilicate microporous crystals.

8. The method for synthesizing methyl heptenone according to claim 4, characterized in that: During the process of adding 2-methyl-3-butene-2-ol dropwise in step S3.1, the temperature in the reactor was maintained at 125-140°C and the top temperature of the tower was maintained at 40-60°C.

9. The method for synthesizing methyl heptenone according to claim 4, characterized in that: The reaction in step S3.1 is completed with the main product content being greater than 80% and methyl acetoacetate being less than 1%.

10. The method for synthesizing methyl heptenone according to claim 4, characterized in that: The distillation kettle in step S3.2 is equipped with a three-stage vacuum pump and a falling film circulation heater, and the top of the tower is equipped with a primary water cooling, a secondary refrigeration cooling system and a receiving tank, and the top of the receiving tank is equipped with a low-temperature condenser.

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