A composite catalyst for the hydrolysis of cyanoacetic acid and a method for synthesizing malonate.

Abstract

This invention provides a composite catalyst for the hydrolysis of cyanoacetic acid and a method for synthesizing malonic acid ester. This invention belongs to the field of fine chemical technology. The composite catalyst includes an active component, a modifier, and a support. The active component includes a main active component and an auxiliary component. The main active component contains Fe. 3+ The additive component comprises ruthenium, copper, cobalt, and cerium metal ions, and the modifier is a sulfosuccinate surfactant. This invention solves the problem of side reactions caused by the use of strong acid catalysts during the hydrolysis of cyanoacetic acid in the prior art. It also solves the problems of low product yield and large amounts of waste, achieving efficient synthesis of malonic acid and malonic esters while reducing production costs and environmental pollution, thus facilitating the large-scale industrial production of malonic acid esters.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, and in particular relates to a composite catalyst for the hydrolysis of cyanoacetic acid and a method for synthesizing malonate. Background Technology

[0002] Dimethyl malonate (DMM), commonly known as dimethyl carotene, is a colorless, transparent liquid with an aromatic odor. It is slightly soluble in water and soluble in many organic solvents, including ether, alcohol, benzene, and chloroform. The industrial grade is a pale yellow, transparent liquid. The DMM molecule contains an active methylene group, allowing it to undergo various substitution reactions such as alkylation, acylation, hydroxyalkylation, and amidation. It is an important raw material for the synthesis of pharmaceuticals, pesticides, fragrances, dyes, antioxidants, and many other fine chemicals. For example, DMM is a crucial raw material for the synthesis of the precious fragrance methyl dihydrojasmonate, and it can also be used as a hydrogenation feedstock to synthesize 1,3-propanediol. It is also a key raw material for the production of pharmaceuticals such as pipemidic acid and coumarin dimethyl malonate.

[0003] Currently, the industrial production of dimethyl malonate involves esterification using chloroacetic acid as a raw material. The process includes neutralization with sodium carbonate, cyanidation with sodium cyanide, acidification, and then esterification with methanol to obtain dimethyl malonate. This method is relatively mature and can achieve stable production. However, it suffers from a long process flow, low yield, and the generation of large amounts of waste salt and wastewater, making post-treatment complex and prone to causing serious environmental pollution, resulting in high production costs for dimethyl malonate.

[0004] CN103319338A discloses a method for synthesizing dimethyl malonate from chloroacetic acid through neutralization, cyanation, acidification, and esterification processes. The method and catalyst for the esterification reaction are also disclosed. Specifically, concentrated sulfuric acid, 4-6 times the weight of methanol (based on chloroacetic acid weight), and a catalyst are added to a solution of cyanoacetic acid to carry out the reaction. The catalyst consists of 8-10 wt% lead chloride, 65-72 wt% triphenylphosphine, 10-15 wt% dimethyl sulfoxide, and 8-12 wt% hydrazine hydrate. This method still uses concentrated sulfuric acid as one of the catalytic components, and the catalyst cannot be recycled, making it impossible to avoid environmental pollution and equipment corrosion.

[0005] CN103304411A discloses a method for synthesizing malonate esters by simultaneously hydrolyzing and esterifying cyanoacetic acid in the presence of ionic liquid and water. The reaction products naturally separate into layers with the acidic water. However, this method suffers from problems such as expensive catalysts, low product yield, and difficulty in recycling and using the ionic liquid phase.

[0006] CN107540543A discloses a method for synthesizing malonic esters. Using 80wt% cyanoacetic acid as a raw material, malonic esters are synthesized via hydrogen chloride alcoholysis. Excess hydrogen chloride is neutralized with ammonia water, and then hydrogen chloride gas is absorbed by alcohol to obtain a hydrogen chloride-alcohol solution. This method uses sulfuric acid or hydrogen chloride gas as a catalyst, which not only causes severe equipment corrosion but also allows excess hydrogen chloride gas to escape into the air, leading to environmental pollution.

[0007] The literature "Improvement of Dimethyl Malonate Synthesis Process" ([J] Henan Chemical Industry, 1999, 15, (1), 90-92) studied the synthesis process of dimethyl malonate. The core technology of the cyanoesterification method consists of two aspects: first, the hydrolysis of cyanoacetic acid to generate malonic acid; second, the esterification of malonic acid with methanol to generate dimethyl malonate. Both steps are usually carried out under the action of strong inorganic acids (such as concentrated sulfuric acid), causing serious equipment corrosion and environmental pollution problems. Among them, esterification is the rate-controlling step, and the rate of esterification determines the rate of the entire reaction. In addition, the esterification reaction is an exothermic reaction. During the esterification process, as the reaction temperature increases, the decomposition of cyanoacetic acid intensifies, resulting in a low overall yield. Under strong acidic conditions, the esterification reaction is a reversible process, and the large equilibrium conversion rate limits its esterification rate. Therefore, increasing the esterification reaction rate, reducing the decomposition of cyanoacetic acid, improving the reaction yield and esterification rate, reducing waste salt and wastewater, and simplifying the post-treatment process are the key points and challenges in the synthesis of dimethyl malonate via cyanide esterification. Developing a more economical and environmentally friendly process for the synthesis of dimethyl malonate has significant economic and environmental implications. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a composite catalyst for the hydrolysis of cyanoacetic acid and a method for synthesizing malonic acid esters. This invention primarily solves the problem of side reactions caused by the use of strong acid catalysts during the hydrolysis of cyanoacetic acid in existing technologies. It also addresses the issues of low product yield and large amounts of waste, achieving efficient synthesis of malonic acid esters and malonic acid, while reducing production costs and environmental pollution, thus facilitating the large-scale industrial production of malonic acid ester products.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] On one hand, the present invention provides a composite catalyst for the hydrolysis of cyanoacetic acid, the composite catalyst comprising an active component, a modifier, and a support, wherein the active component comprises a main active component and an auxiliary component, and the main active component contains Fe. 3+ The additive component is a substance containing ruthenium, copper, cobalt, and cerium metal ions, and the modifier is a sulfosuccinate surfactant.

[0011] In this invention, the active metal ions in the composite catalyst activate the cyano group through an electron-withdrawing inductive effect, lowering the activation energy and promoting the forward hydrolysis reaction. The sulfosuccinate modifier molecules possess excellent surface properties, containing both lipophilic and hydrophilic groups, which reduce the surface tension of the support. This not only enhances the contact probability between the catalyst and the substrate, promoting efficient reaction, but also allows the carbonyl groups to bind to the substrate through hydrogen bonding, facilitating high selectivity in the hydrolysis reaction. Furthermore, the catalyst of this invention exhibits high activity, enabling the hydrolysis reaction to proceed under mild conditions, reducing the decomposition of cyanoacetic acid caused by improper temperature control and alcohol ratios, and avoiding polymer formation due to the exothermic properties of hydrolysis, further improving the selectivity of the hydrolysis reaction. Moreover, the modifiers and metal ions in this catalyst can interact, reducing the loss of active components and enabling multiple batches of catalyst recycling, thus lowering the catalyst's operating cost.

[0012] Preferably, the main active component is selected from Fe-containing... 3+ One or a combination of at least two of the sulfate, hydrochloride, nitrate and their hydrates of the ion.

[0013] Preferably, the auxiliary component is selected from one or at least two combinations of sulfates, hydrochlorides, nitrates and their hydrates containing ruthenium, copper, cobalt or cerium metal ions.

[0014] Preferably, the mass ratio of the main active component to the auxiliary component is 1 to 5:1, for example 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, preferably 3 to 5:1.

[0015] Preferably, the modifier is selected from one or a combination of at least two of sodium dioctyl sulfosuccinate, sodium dibutyl sulfosuccinate, sodium ditridecyl sulfosuccinate, sodium isodecyl sulfosuccinate, sodium methyl isobutyl sulfosuccinate, or sodium dipentyl sulfosuccinate.

[0016] Preferably, the carrier is one or a combination of at least two of ZSM-5, Al2O3, SiO2, TiO2, and La2O3.

[0017] Preferably, the mass ratio of the modifier to the carrier is 4 to 10:1, such as 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, and more preferably 6 to 8:1.

[0018] Preferably, the mass ratio of the main active component to the carrier is 0.01 to 0.09:1, for example, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1 or 0.09:1, and more preferably 0.03 to 0.05:1.

[0019] In this invention, the mass ratio of the main active component to the carrier refers to the mass ratio of the effective loading of metal ions to the mass ratio of the carrier.

[0020] On the other hand, the present invention provides a method for preparing the composite catalyst for the hydrolysis of cyanoacetic acid as described above, the preparation method comprising the following steps:

[0021] (1) Modify the carrier using a modifier to obtain the modified carrier;

[0022] (2) Add the main active component to the system obtained in step (1) and perform isothermal adsorption;

[0023] (3) Add the auxiliary component to the system obtained in step (2) and perform isothermal adsorption to obtain the composite catalyst.

[0024] In this invention, the support is modified with a modifier. The modifier has hydroxyl groups and can bind with aluminum, oxygen, silicon and other atoms exposed on the surface of the support through hydrogen bonds, thereby enabling it to be relatively stably adsorbed on the surface and in the pores of the support, which helps to construct a complete catalytic system.

[0025] Preferably, the modification in step (1) is carried out in a solvent, which is water.

[0026] Preferably, the modification in step (1) is carried out under stirring at 80℃~120℃ (e.g., 80℃, 90℃, 100℃, 110℃ or 120℃) for 2~4 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours) to complete the modification.

[0027] Preferably, the temperature of the isothermal adsorption in step (2) is 40℃~60℃ (e.g., 40℃, 45℃, 50℃, 55℃ or 60℃), and the time is 2~6 hours (e.g. 2 hours, 3 hours, 4 hours, 5 hours or 6 hours).

[0028] Preferably, the temperature of the isothermal adsorption in step (3) is 40℃~60℃ (e.g., 40℃, 45℃, 50℃, 55℃ or 60℃), and the time is 2~6 hours (e.g. 2 hours, 3 hours, 4 hours, 5 hours or 6 hours).

[0029] Preferably, after the isothermal adsorption in step (3) is completed, excess moisture is removed, and the resulting solid is dried to constant weight to obtain the composite catalyst.

[0030] On the other hand, the present invention provides a method for synthesizing malonate, the method comprising the following steps:

[0031] Cyanoacetic acid undergoes hydrolysis in the presence of the composite catalyst described above to produce malonic acid, which is then esterified with an alcohol to produce malonate.

[0032] The reaction process is as follows:

[0033] .

[0034] Preferably, the mass ratio of the composite catalyst to cyanoacetic acid is 0.03 to 0.09:1, for example, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1 or 0.09:1, and more preferably 0.05 to 0.07:1.

[0035] Preferably, the hydrolysis reaction is carried out in water as a solvent.

[0036] Preferably, the mass ratio of cyanoacetic acid to water is 1.0 to 2.0:1, for example, 1.0:1, 1.2:1, 1.5:1, 1.8:1 or 2.0:1, and more preferably 1.2 to 1.6:1.

[0037] Preferably, the hydrolysis reaction temperature is 60℃~100℃, for example 60℃, 65℃, 70℃, 75℃, 80℃, 90℃ or 100℃, and the hydrolysis reaction time is 1~4 hours, for example 1 hour, 2 hours, 3 hours or 4 hours.

[0038] Preferably, the alcohol is selected from at least one of methanol, ethanol, n-propanol, isopropanol or n-butanol, and the corresponding products are one or a combination of at least two of dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate or dibutyl malonate.

[0039] Preferably, the esterification reaction is carried out under the catalysis of an esterification catalyst.

[0040] Preferably, the esterification catalyst is a common acidic catalyst selected from p-benzenesulfonic acid and / or sulfuric acid. In this invention, the corresponding product is obtained by reacting at a conventional esterification temperature of 100~160℃ (e.g., 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃) and a time of 2~4 hours (e.g., 2 hours, 3 hours or 4 hours).

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention provides a method for simultaneously obtaining malonic acid esters and malonic acid. In actual production, production can be switched according to market conditions, which is beneficial for the large-scale industrial production of malonic acid esters. Attached Figure Description

[0043] Figure 1 This is a comparison of the mass spectrum of the product from the esterification reaction example (top image) with the standard mass spectrum of dimethyl malonate in the spectral library (bottom image);

[0044] Figure 2 A photograph of the composite catalyst prepared in Example 24 under a 200x scanning electron microscope;

[0045] Figure 3 A 1000x scanning electron microscope image of the composite catalyst prepared in Example 24 for catalyst preparation;

[0046] Figure 4 The gas phase spectrum of the dimethyl malonate product obtained in the esterification reaction example;

[0047] Figure 5 The mass spectrum of the malonic acid product obtained in Application Example 1 is shown. Detailed Implementation

[0048] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0049] Unless otherwise specified, the test reagents used in the following examples are all conventional biochemical reagents; and the experimental methods described are all conventional methods unless otherwise specified.

[0050] The mass concentration of the purchased cyanoacetic acid solution is 70%~80%. The mass concentration used in this invention is 70%, which is commonly used in industry. The amount of cyanoacetic acid used in this invention is the purified cyanoacetic acid.

[0051] Catalyst Preparation Example 1

[0052] At room temperature, sodium dipentyl sulfosuccinate (60 g, 0.1665 mol) was added to 60 ml of deionized water and stirred until homogeneous. Then, 10.0 g of support ZSM-5 was added, the temperature was raised to 100 °C, and stirred for 2 hours. After that, the temperature was lowered to 40 °C, FeCl3 (1.452 g, 8.953 mmol) was added, and after adsorption for 4 hours, RuCl3·3H2O (0.363 g, 1.39 mmol) was added. After adsorption for 6 hours, the temperature was lowered to room temperature, filtered, and the resulting filter cake was dried to constant weight to obtain catalyst No. 1.

[0053] Catalyst Preparation Examples 2-6

[0054] Examples 2-6 provide a method for preparing a composite catalyst. The only difference from Example 1 is that the sodium dipentyl sulfosuccinate modifier in Example 1 is replaced with sodium dibutyl sulfosuccinate (60g, 0.1805mol), sodium ditridecyl sulfosuccinate (60g, 0.1238mol), sodium isodecyl sulfosuccinate (60g, 0.1569mol), sodium methyl isobutyl sulfosuccinate (60g, 0.1537mol), and sodium dioctyl sulfosuccinate (60.0g, 0.1350mol), while keeping the types and amounts of the main active metal salt, auxiliary metal salt, and support unchanged.

[0055] Catalyst Preparation Examples 7-10

[0056] Examples 7-10 of this catalyst preparation method provide a method for preparing a composite catalyst. The only difference from Example 1 is that the main active metal salt FeCl3 in Example 1 is replaced with FeSO4·7H2O, Fe(NO3)3·9H2O, Fe(NH4)2·(SO4)2·6H2O, and FeCl3·6H2O respectively, while keeping the types and amounts of auxiliary metals, modifiers and supports unchanged. See Table 1 for details.

[0057] Table 1

[0058]

[0059] Catalyst Preparation Examples 11-13

[0060] Examples 11-13 of this catalyst preparation method provide a method for preparing a composite catalyst. The only difference from Example 1 is that the auxiliary metal salt RuCl3·3H2O in Example 1 is replaced with CuSO4·5H2O (0.363g, 1.454mmol), Co(NO3)2·6H2O (0.363g, 1.247mmol), and Ce(NO3)2·6H2O (0.363g, 0.836mmol) respectively, while keeping the types and amounts of the main active metal, modifier, and support unchanged.

[0061] Catalyst Preparation Examples 14-17

[0062] Examples 14-17 of this catalyst preparation method provide a method for preparing a composite catalyst. The difference from Example 1 is that the loading of the main active metal is 0.01:1, 0.03:1, 0.07:1, and 0.09:1, respectively, and the amount of auxiliary metal salt is adjusted as shown in Table 2.

[0063] Table 2

[0064]

[0065] Catalyst Preparation Examples 18-20

[0066] Examples 18-20 of this catalyst preparation method provide a method for preparing a composite catalyst. The difference from Example 1 is that the mass ratio of the main active metal salt FeCl3 and the auxiliary active metal salt RuCl3·3H2O is 1:1, 3:1 and 5:1, respectively, while keeping the types and amounts of the main active metal salt, modifier and support unchanged, as shown in Table 3.

[0067] Table 3

[0068]

[0069] Catalyst Preparation Examples 21-23

[0070] Examples 21-23 of this catalyst preparation method provide a method for preparing a composite catalyst. The difference from Example 1 is that the mass ratio of the support and the modifier is adjusted to 1:4, 1:8 and 1:10 respectively, while keeping the types and amounts of the main active metal salt, modifier and support unchanged, as shown in Table 4.

[0071] Table 4

[0072]

[0073] Catalyst Preparation Examples 24-27

[0074] Examples 24-27 of this catalyst preparation provide a method for preparing a composite catalyst. The difference from Example 1 is that the support ZSM-5 is adjusted to Al2O3, SiO2, TiO2, and La2O3, while keeping the types and amounts of the main active metal salt, auxiliary metal salt, modifier, and support unchanged.

[0075] Figure 2 A 200x scanning electron microscope image of the composite catalyst prepared in Example 24. Figure 3 The image shows the composite catalyst prepared in Example 24 under a 1000x scanning electron microscope (SEM). The SEM instrument is a JEOL JSM-6701F.

[0076] Catalyst Preparation Examples 28-35

[0077] Examples 28-35 provide a method for preparing a heterogeneous catalyst. The only difference from Example 1 is the adjustment of the modification temperature and time, and the adjustment of the adsorption temperature and time of the main active metal and the auxiliary metal, as shown in Table 5.

[0078] Table 5

[0079]

[0080] Comparative Example 1

[0081] At room temperature, 10.0 g of support ZSM-5 was added to 60 ml of deionized water, followed by FeCl3 (1.452 g, 8.953 mmol). After heating to 40 °C and maintaining the temperature for 4 hours for adsorption, RuCl3·3H2O (0.363 g, 1.39 mmol) was added, and the temperature was maintained for 6 hours for adsorption. The mixture was then cooled to room temperature, filtered, and the resulting filter cake was dried to constant weight to obtain catalyst No. 1 of Comparative Example.

[0082] Comparative Example 2

[0083] At room temperature, sodium dipentyl sulfosuccinate (60 g, 0.1665 mol) was added to 60 ml of deionized water and stirred until homogeneous. Then, 10.0 g of support ZSM-5 was added, the temperature was raised to 100 °C, and stirred for 2 hours. After that, the temperature was lowered to 40 °C, and FeCl3 (1.452 g, 8.953 mmol) was added. After adsorption for 4 hours, the temperature was lowered to room temperature, filtered, and the resulting filter cake was dried to constant weight to obtain catalyst No. 2 of Comparative Example.

[0084] Catalyst Application Examples

[0085] Application Example 1

[0086] In a 250 ml three-necked flask, 50.0 g of cyanoacetic acid (purified mass), 2.5 g of composite catalyst (the composite catalyst prepared in Example 1, catalyst concentration 5.0%), and 50.0 g of deionized water (cyanoacetic acid to water mass ratio 1:1) were added. The mixture was heated to 80 °C and reacted for 2 hours. Excess water was removed to obtain white malonic acid crystals. The calculated yield was 98.24%. The mass spectrum of the product is shown below. Figure 5 As shown.

[0087] Application Examples 2-4

[0088] The only difference between Application Examples 2-4 and Application Example 1 is that the molar ratio of cyanoacetic acid to water is adjusted to 1:1.0, 1:1.2, 1:1.6, and 1:2.0, respectively, with corresponding water amounts of 10.58g, 12.70g, 16.93g, and 21.16g. The rest is the same as Application Example 1, and the results are shown in Table 6.

[0089] Application Examples 5-8

[0090] The only difference between Application Examples 5-8 and Application Example 1 is the change in hydrolysis reaction temperature and time; otherwise, they are the same as Application Example 1. The temperatures for Application Examples 5 and 6 are 60℃ and 100℃, respectively; otherwise, they are the same as Application Example 1. The reaction times for Application Examples 7 and 8 are 1 hour and 4 hours, respectively; otherwise, they are the same as Application Example 1. The results are shown in Table 6.

[0091] Application Examples 9-11

[0092] The only difference between Application Examples 9-11 and Application Example 1 is that the catalyst concentration was changed to 3.0%, 7.0%, and 9.0% respectively, and the corresponding catalyst dosage was 1.5g, 3.5g, and 4.5g respectively. Everything else was the same as Application Example 1. The results are shown in Table 6.

[0093] Application Examples 12-45

[0094] Application Examples 12-45 each provide a composite catalyst, which is the composite phase catalyst provided in Examples 2-35 above, and is used for the hydrolysis reaction of cyanoacetic acid, otherwise the same as in Application Example 1. The results are shown in Table 6.

[0095] Application Comparative Examples 1-2

[0096] Comparative Examples 1 and 2 of this application provide an application of a composite catalyst, differing from Application Example 1 only in that the composite catalysts used in Comparative Examples 1 and 2 are employed sequentially; otherwise, they are the same as in Application Example 1. The results are shown in Table 6.

[0097] Table 6

[0098]

[0099] Catalyst application examples

[0100] The catalyst recovered in Application Example 1 was washed with deionized water 2-3 times to obtain the recovered catalyst. The catalyst was then reused, with the first use of the recovered catalyst being considered as 1 reuse, the second use as 2 reuses, and so on. The specific results are shown in Table 7.

[0101] Table 7

[0102]

[0103] Esterification reaction examples

[0104] The malonic acid obtained in the above application example is reacted with methanol to prepare dimethyl malonate. The specific steps are as follows:

[0105] In a 250 ml three-necked flask, 50.0 g of malonic acid, 100 g of methanol, and 5.0 g of concentrated sulfuric acid were added sequentially. Stirring was started, and the temperature was raised to 100 °C and maintained for 2 hours. After the reaction was complete, unreacted alcohol was recovered by vacuum distillation, and 60.43 g of dimethyl malonate was obtained by fractional distillation, with a calculated yield of 95.20%. The mass spectrum of the product is shown below. Figure 1 As shown, the gas phase spectrum of the product is as follows: Figure 4 As shown in the table below, the analysis results of the gas phase spectrum are as follows.

[0106] Table 8

[0107]

[0108] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the composite catalyst and the synthesis method of malonic acid ester, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A composite catalyst for the hydrolysis of cyanoacetic acid, characterized in that, The composite catalyst comprises an active component, a modifier, and a support. The active component includes a main active component and an auxiliary component. The main active component contains Fe. 3+ The additive component is a substance containing ruthenium, copper, cobalt or cerium metal ions, and the modifier is a sulfosuccinate surfactant, which modifies the carrier.

2. The composite catalyst for catalyzing the hydrolysis of cyanoacetic acid according to claim 1, characterized in that, The main active component is selected from Fe-containing... 3+ One or a combination of at least two of the sulfates, hydrochlorides, nitrates and their hydrates of the ions; The auxiliary component is selected from one or at least two combinations of sulfates, hydrochlorides, nitrates and their hydrates containing ruthenium, copper, cobalt or cerium metal ions; The mass ratio of the main active component to the auxiliary component is 1~5:

1.

3. The composite catalyst for catalyzing the hydrolysis of cyanoacetic acid according to claim 1, characterized in that, The modifier is selected from one or a combination of at least two of sodium dioctyl sulfosuccinate, sodium dibutyl sulfosuccinate, sodium ditridecyl sulfosuccinate, sodium isodecyl sulfosuccinate, sodium methyl isobutyl sulfosuccinate, or sodium dipentyl sulfosuccinate. The carrier is one or a combination of at least two of ZSM-5, Al2O3, SiO2, TiO2, and La2O3; The mass ratio of the modifier to the carrier is 4~10:1; The mass ratio of the main active component to the carrier is 0.01~0.09:

1.

4. The composite catalyst for catalyzing the hydrolysis of cyanoacetic acid according to claim 2 or 3, characterized in that, The mass ratio of the main active component to the auxiliary component is 3~5:1; The mass ratio of the modifier to the carrier is 6-8:1; The mass ratio of the main active component to the carrier is 0.03~0.05:

1.

5. The method for preparing the composite catalyst for the catalytic hydrolysis of cyanoacetic acid according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: (1) Modify the carrier using a modifier to obtain the modified carrier; (2) Add the main active component to the system obtained in step (1) and perform isothermal adsorption; (3) Add the auxiliary component to the system obtained in step (2) and perform isothermal adsorption to obtain the composite catalyst.

6. The preparation method according to claim 5, characterized in that, The modification in step (1) is carried out in a solvent, namely water; The modification described in step (1) is carried out under stirring at 80℃~120℃ for 2~4 hours to complete the modification; The temperature for isothermal adsorption in step (2) is 40℃~60℃, and the time is 2~6 hours; The temperature for isothermal adsorption in step (3) is 40℃~60℃, and the time is 2~6 hours; After the isothermal adsorption in step (3) is completed, remove excess moisture and dry the resulting solid to constant weight to obtain the composite catalyst.

7. A method for synthesizing malonate, characterized in that, The synthesis method includes the following steps: Cyanoacetic acid undergoes hydrolysis in the presence of the composite catalyst described in any one of claims 1-4 to produce malonic acid, which is then esterified with an alcohol to produce malonate.

8. The synthesis method according to claim 7, characterized in that, The mass ratio of the composite catalyst to cyanoacetic acid is 0.03~0.09:1; The hydrolysis reaction is carried out in water as a solvent; The mass ratio of cyanoacetic acid to water is 1.0~2.0:1; The hydrolysis reaction temperature is 60℃~100℃, and the hydrolysis reaction time is 1~4 hours.

9. The synthesis method according to claim 7, characterized in that, The alcohol is selected from at least one of methanol, ethanol, n-propanol, isopropanol, or n-butanol; The esterification reaction is carried out under the catalysis of an esterification catalyst; The esterification catalyst is an acidic catalyst, which is p-benzenesulfonic acid and / or sulfuric acid; The esterification reaction is carried out at a temperature of 100-160°C for 2-4 hours.

10. The synthesis method according to claim 8 or 9, characterized in that, The mass ratio of the composite catalyst to cyanoacetic acid is 0.05~0.07:1; The mass ratio of cyanoacetic acid to water is 1.2~1.6:1.

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