Method for preparing diphenylmethane dicarbamate by self-separation sulfonic acid ionic liquid catalyst

Abstract

The invention provides a method for preparing diphenylmethane dicarbamate by using a self-separation sulfonic acid ionic liquid catalyst, which comprises the following steps: mixing phenyl carbamate, trioxymethylene and a sulfonic acid ionic liquid catalyst, and carrying out condensation reaction to obtain the diphenylmethane dicarbamate. The synthesis of the diphenylmethane dicarbamate can be realized under the solvent-free condition by utilizing the sulfonic acid ionic liquid catalyst, and the size required by a reactor is greatly reduced; meanwhile, after the sulfonic acid ionic liquid reacts, the catalyst can be recycled through simple phase separation, and the method has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of catalysis technology, specifically relating to a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. Background Technology

[0002] Diphenylmethane diisocyanate (MDI) is a crucial raw material in the polyurethane industry. Based on the number of benzene rings, it can be classified into 2-MDI, 3-MDI, and 4-MDI. Among them, 2-MDI has shown excellent performance in high-end applications such as rocket propellants, high-performance coatings, and medical device components. Methyl diphenylmethane dicarboxylate (MDC) is an important intermediate in the non-phosgene route for MDI synthesis and is a vital raw material in the polyurethane industry. Traditionally, it is prepared using highly toxic phosgene, and the reaction process is uncontrollable. The condensation of methyl phenylcarboxylate (MPC) with formaldehyde to prepare MDC allows for controllable production of the MDC product, which is significant for developing non-phosgene green MDI synthesis technology. Currently, the condensation of MPC with formaldehyde to prepare MDC suffers from numerous byproducts, making the development of efficient catalysts crucial for MDC synthesis. Currently, publicly reported catalysts can be classified into three categories: liquid acid catalysts, solid acid catalysts, and ionic liquid catalysts.

[0003] CN 1775354A, CN 107434774A, CN 101440048A, and CN 113926403A all disclose methods for preparing MDC using hydrochloric acid, sulfuric acid, nitric acid, or a complex acid of acetic acid and sulfuric acid as catalysts and water, o-dichlorobenzene, or dimethyl carbonate as solvents. Homogeneous liquid acid catalysts exhibit high catalytic activity but are highly corrosive and polluting, and difficult to recover. CN106565545A discloses a method for preparing MDC using a supported heteropoly solid acid catalyst at 160°C with diethylene glycol dimethyl ether as a solvent. Solid acid heterogeneous catalysts have advantages such as easy separation and recovery, but suffer from problems such as high reaction temperature, low reaction efficiency, and numerous byproducts. Furthermore, the above methods cannot avoid using large amounts of solvent, increasing the cost of the recovery process and requiring larger reactors. Therefore, providing a novel green catalyst for the solvent-free condensation of MPC and trioxymethylene to prepare MDC is of great significance for the industrial production of MDC.

[0004] CN 102516128A discloses a process for synthesizing diphenylmethane dicarboxylate using Brønsted-Lewis dual-acidic ionic liquid catalysis. The ionic liquid acts as both a catalyst and a solvent. However, the homogeneous ionic liquid catalyst is completely miscible with the product MDC, and post-processing methods such as extraction, vacuum distillation, and freeze crystallization are required to obtain the product, which is complex.

[0005] Ionic liquids possess excellent chemical stability, superior molecular designability, and reusability. Among them, triethylamine ionic liquids exhibit high acid density and good fluidity. They are insoluble in most organic solvents at room temperature, but can form a homogeneous catalysis with the reaction mixture after heating and stirring. They are also readily precipitated upon cooling to room temperature, making them suitable for the synthesis of MDC under solvent-free conditions. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. This invention utilizes a self-separating sulfonic acid ionic liquid catalyst to efficiently synthesize diphenylmethane dicarboxylate under solvent-free conditions, significantly reducing the required reactor size. Furthermore, the catalyst recovery method is simple, demonstrating promising prospects for industrial application.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst, the method comprising:

[0009] The diphenylmethane dicarboxylate is obtained by condensation reaction of a mixture of phenylcarboxylate, trioxymethane, and sulfonic acid ionic liquid catalyst.

[0010] The reaction process of the diphenylmethane dicarboxylate described in this invention is as follows:

[0011]

[0012] Where R is methyl or ethyl.

[0013] In this invention, the fusion of phenylcarbamate and trioxymethane can be achieved without solvent. The trioxymethane decomposes into formaldehyde under acidic conditions, and then undergoes a catalytic condensation reaction with phenylcarbamate under the action of a sulfonic acid ionic liquid catalyst to obtain the diphenylmethane dicarbamate.

[0014] As a preferred embodiment of the present invention, the phenylcarbamate includes methyl phenylcarbamate or ethyl phenylcarbamate.

[0015] Preferably, the structural formula of the sulfonic acid ionic liquid catalyst is:

[0016]

[0017] Where n is 1 or 2; X - It includes any one of sulfate ions, p-toluenesulfonate ions, or phosphate ions.

[0018] As a preferred embodiment of the present invention, the molar ratio of phenylcarbamate to trioxymethylene is 5.0 to 25.0:1, for example, it can be 5.0:1, 10.0:1, 15.0:1, 20.0:1 or 25.0:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the mass of the sulfonic acid ionic liquid catalyst is 1 to 30 wt% of the mass of the phenylcarbamate, for example, it can be 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] As a preferred embodiment of the present invention, the temperature of the condensation reaction is 60~120℃, for example, it can be 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the condensation reaction time is 0.5 to 10 hours, for example, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In this invention, a high temperature in the condensation reaction will lead to over-reaction, resulting in the generation of byproducts such as 3-MDC, while a low temperature will result in a slower reaction rate.

[0023] As a preferred embodiment of the present invention, the condensation reaction is further followed by a cooling process and a phase separation process performed sequentially.

[0024] The present invention remains a mixed solution at the end of the condensation reaction. After cooling, the reaction product and the sulfonic acid ionic liquid catalyst undergo phase separation, achieving effective catalyst recovery and showing good prospects for industrial application.

[0025] As a preferred embodiment of the present invention, the sulfonic acid ionic liquid catalyst is prepared by the following method:

[0026] (1) Triethylamine and solvent are mixed to obtain a first mixed solution, and sulfolactone and solvent are mixed to obtain a second mixed solution;

[0027] (2) The second mixed solution is added dropwise to the first mixed solution to carry out a reaction, and then the first washing and first drying are carried out in sequence to obtain the intermediate product;

[0028] (3) Mix the intermediate product and the inorganic solvent to obtain a third mixed solution, and mix the acid solution and the inorganic solvent to obtain a fourth mixed solution;

[0029] (4) The fourth solution is added dropwise to the third solution to carry out a secondary reaction, and then the second washing and the second drying are carried out in sequence to obtain the sulfonic acid ionic liquid catalyst.

[0030] This invention prepares a sulfonic acid ionic liquid catalyst using triethylamine and sulfonyl lactone as raw materials. The catalyst has good fluidity and can form a homogeneous catalysis with the reaction reagents after heating, which greatly reduces the required size of the reactor.

[0031] As a preferred technical solution of the present invention, the solvent in step (1) includes any one or at least two combinations of ethyl acetate, chloroform or acetonitrile. Typical but non-limiting combinations include: a combination of ethyl acetate and chloroform, a combination of ethyl acetate and acetonitrile, a combination of chloroform and acetonitrile, or a combination of ethyl acetate, chloroform and acetonitrile.

[0032] Preferably, the sulfonyl lactone in step (1) includes 1,3-propanesulfonyl lactone or 1,4-butanesulfonyl lactone.

[0033] Preferably, the molar ratio of triethylamine to solvent in step (1) is 1:1.5 to 5.0, for example, it can be 1:1.5, 1:2.0, 1:2.5, 1:3.0, 1:3.5, 1:4.0, 1:4.5 or 1:5.0, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the molar ratio of sulfonyl lactone to solvent in step (1) is 1:1.5 to 5.0, for example, it can be 1:1.5, 1:2.0, 1:2.5, 1:3.0, 1:3.5, 1:4.0, 1:4.5 or 1:5.0, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] As a preferred technical solution of the present invention, the temperature of the first reaction in step (2) is 60~65℃, for example, it can be 60℃, 61℃, 62℃, 63℃, 64℃ or 65℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the reaction time in step (2) is 12 to 72 hours, for example, 12 hours, 24 hours, 36 hours, 48 ​​hours, 60 hours or 72 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the dripping rate in step (2) is 2~3 s / drop, for example, it can be 2 s / drop, 2.2 s / drop, 2.4 s / drop, 2.6 s / drop, 2.8 s / drop or 3 s / drop, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] It is worth noting that the first mixed solution needs to be stirred during the process of adding the second mixed solution in step (2). The present invention does not limit the speed of stirring during the process, as long as the reaction can be achieved in one step.

[0039] Preferably, the washing solution used in step (2) for the first washing includes any one or a combination of at least two of ethyl acetate, chloroform, or tetrahydrofuran. For example, it may be a combination of ethyl acetate and chloroform, a combination of ethyl acetate and tetrahydrofuran, a combination of chloroform and tetrahydrofuran, or a combination of ethyl acetate, chloroform, and tetrahydrofuran.

[0040] Preferably, the temperature of the first drying in step (2) is 60~80℃, for example, it can be 60℃, 64℃, 68℃, 72℃, 76℃ or 80℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the drying time in step (2) is 12 to 48 hours, for example, it can be 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours or 48 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] As a preferred technical solution of the present invention, the inorganic solvent in step (3) includes deionized water.

[0043] Preferably, the acid solution in step (3) includes any one of sulfuric acid, p-toluenesulfonic acid, or phosphoric acid.

[0044] Preferably, the molar ratio of the intermediate product and the inorganic solvent in step (3) is 1:20 to 40, for example, it can be 1:20, 1:24, 1:28, 1:32, 1:36 or 1:40, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] Preferably, the molar ratio of acid and inorganic solvent in step (3) is 1:20 to 40, for example, it can be 1:20, 1:24, 1:28, 1:32, 1:36 or 1:40, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] As a preferred technical solution of the present invention, the dripping rate in step (4) is 2~3s / drop, for example, it can be 2s / drop, 2.2s / drop, 2.4s / drop, 2.6s / drop, 2.8s / drop or 3s / drop, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the temperature of the secondary reaction in step (4) is 75~80℃, for example, it can be 75℃, 76℃, 77℃, 78℃, 79℃ or 80℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the time for the secondary reaction in step (4) is 12 to 72 hours, for example, it can be 12 hours, 24 hours, 36 hours, 48 ​​hours, 60 hours or 72 hours, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, the washing solution used in step (4) for the second washing includes any one or at least two of ethyl acetate, chloroform, or tetrahydrofuran. Typical but non-limiting combinations include: a combination of ethyl acetate and chloroform, a combination of ethyl acetate and tetrahydrofuran, a combination of chloroform and tetrahydrofuran, or a combination of ethyl acetate, chloroform, and tetrahydrofuran.

[0050] Preferably, the temperature of the second drying step (4) is 60~80℃, for example, it can be 60℃, 64℃, 68℃, 72℃, 76℃ or 80℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the second drying time in step (4) is 12 to 48 hours, for example, it can be 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours or 48 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] It is worth noting that the first drying and the second drying in steps (2) and (4) of this invention are vacuum drying. This invention does not limit the degree of vacuum in the drying process, as long as the product can be dried.

[0053] As a preferred embodiment of the present invention, the preparation method of the sulfonic acid ionic liquid catalyst includes the following steps:

[0054] (1) Triethylamine and solvent are mixed to obtain a first mixed solution, and sulfolactone and solvent are mixed to obtain a second mixed solution;

[0055] Wherein, the molar ratio of triethylamine to solvent is 1:1.5~5.0; the molar ratio of sulcolactone to solvent is 1:1.5~5.0;

[0056] (2) The second mixed solution is added dropwise to the first mixed solution at a rate of 2~3s / drop to carry out a single reaction, followed by a first washing and a first drying to obtain the intermediate product;

[0057] The temperature of the first reaction is 60~65℃ and the time is 12~72h;

[0058] The first drying temperature is 60~80℃, and the time is 12~48h;

[0059] (3) Mix the intermediate product and deionized water to obtain a third mixed solution, and mix the acid solution and deionized water to obtain a fourth mixed solution;

[0060] Wherein, the molar ratio of the intermediate product to deionized water is 1:20~40; the molar ratio of the acid solution to deionized water is 1:20~40;

[0061] (4) The fourth solution is added dropwise to the third solution at a rate of 2~3s / drop to carry out a secondary reaction, and then the second washing and the second drying are carried out in sequence to obtain the sulfonic acid ionic liquid catalyst;

[0062] The secondary reaction is carried out at a temperature of 75-80°C for 12-72 hours.

[0063] The second drying temperature is 60~80℃, and the time is 12~48h.

[0064] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) The present invention utilizes sulfonic acid ionic liquid catalyst to achieve mild preparation of diphenylmethane dicarboxylate under solvent-free conditions, which greatly reduces the required size of the reactor;

[0067] (2) After the condensation reaction described in this invention, the sulfonic acid ionic liquid catalyst can be recovered through simple phase separation, which has good prospects for industrial application. Detailed Implementation

[0068] 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.

[0069] The raw materials used in the following examples and comparative examples are all commercially available.

[0070] Example 1

[0071] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The method includes:

[0072] A mixture of methyl phenylcarbamate, trioxymethane, and a sulfonic acid ionic liquid catalyst is subjected to a condensation reaction followed by a cooling process to achieve phase separation between the sulfonic acid ionic liquid catalyst and the reaction products, thereby obtaining the diphenylmethane dicarbamate and recovering the catalyst.

[0073] The molar ratio of methyl phenylcarbamate to trioxymethylene is 15.0:1; the mass of the sulfonic acid ionic liquid catalyst is 6 wt% of the mass of methyl phenylcarbamate.

[0074] The condensation reaction was carried out at a temperature of 95°C for 3.5 hours.

[0075] The preparation method of the sulfonic acid ionic liquid catalyst includes the following steps:

[0076] (1) Triethylamine and ethyl acetate were mixed to obtain a first mixed solution, and 1,3-propanesulfonyl lactone and ethyl acetate were mixed to obtain a second mixed solution;

[0077] Wherein, the molar ratio of triethylamine to ethyl acetate is 1:3.0; the molar ratio of 1,3-propanesulfonyl lactone to ethyl acetate is 1:3.0;

[0078] (2) The second mixed solution is added dropwise to the first mixed solution at a rate of 2s / drop to carry out a single reaction, followed by a first wash and a first dry to obtain the intermediate product;

[0079] The temperature of the first reaction is 60°C and the time is 12 hours.

[0080] The washing solution used in the first washing is ethyl acetate, and the first washing is performed 5 times; the first drying temperature is 80℃, and the time is 12 hours.

[0081] (3) Mix the intermediate product and deionized water to obtain a third mixed solution, and mix sulfuric acid and deionized water to obtain a fourth mixed solution;

[0082] Wherein, the molar ratio of the intermediate product to deionized water is 1:30; the molar ratio of the sulfuric acid to deionized water is 1:30;

[0083] (4) The fourth solution is added dropwise to the third solution at a rate of 2s / drop to carry out a secondary reaction, and then the second washing and the second drying are carried out in sequence to obtain the sulfonic acid ionic liquid catalyst;

[0084] The secondary reaction was carried out at a temperature of 80°C for 24 hours.

[0085] The washing solution used in the second washing is ethyl acetate, and the first washing is performed 5 times; the second drying temperature is 80℃ and the time is 12 hours.

[0086] Example 2

[0087] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The method includes:

[0088] Ethyl phenylcarbamate, trioxymethylene, and sulfonic acid ionic liquid catalyst are mixed and subjected to a condensation reaction followed by a cooling process to achieve phase separation between the sulfonic acid ionic liquid catalyst and the reaction products, thereby obtaining the diphenylmethane dicarbamate and recovering the catalyst.

[0089] The molar ratio of ethyl phenylcarbamate to trioxymethylene is 25.0:1; the mass of the sulfonic acid ionic liquid catalyst is 15 wt% of the mass of ethyl phenylcarbamate.

[0090] The condensation reaction was carried out at a temperature of 60°C for 10 hours.

[0091] The preparation method of the sulfonic acid ionic liquid catalyst includes the following steps:

[0092] (1) Triethylamine and chloroform are mixed to obtain a first mixed solution, and 1,4-butanesulfonyl lactone and chloroform are mixed to obtain a second mixed solution;

[0093] Wherein, the molar ratio of triethylamine to chloroform is 1:4.0; the molar ratio of 1,4-butanesulfonyl lactone to chloroform is 1:4.0;

[0094] (2) The second mixed solution is added dropwise to the first mixed solution at a rate of 3s / drop to carry out a single reaction, followed by a first wash and a first dry to obtain the intermediate product;

[0095] The temperature of the first reaction is 60°C and the time is 16 hours.

[0096] The first washing process uses chloroform as the washing solution and involves 5 washing cycles; the first drying process is carried out at a temperature of 60°C for 48 hours.

[0097] (3) Mix the intermediate product and deionized water to obtain a third mixed solution, and mix p-toluenesulfonic acid and deionized water to obtain a fourth mixed solution;

[0098] Wherein, the molar ratio of the intermediate product to deionized water is 1:30; the molar ratio of p-toluenesulfonic acid to deionized water is 1:30;

[0099] (4) The fourth solution is added dropwise to the third solution at a rate of 3s / drop to carry out a secondary reaction, and then the second washing and the second drying are carried out in sequence to obtain the sulfonic acid ionic liquid catalyst;

[0100] The secondary reaction was carried out at a temperature of 75°C for 24 hours.

[0101] The washing solution used in the second washing is chloroform, and the washing is performed 5 times; the temperature of the second drying is 60°C, and the time is 48 hours.

[0102] Example 3

[0103] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The method includes:

[0104] A mixture of methyl phenylcarbamate, trioxymethane, and a sulfonic acid ionic liquid catalyst is subjected to a condensation reaction followed by a cooling process to achieve phase separation between the sulfonic acid ionic liquid catalyst and the reaction products, thereby obtaining the diphenylmethane dicarbamate and recovering the catalyst.

[0105] The molar ratio of methyl phenylcarbamate to trioxymethylene is 9.0:1; the mass of the sulfonic acid ionic liquid catalyst is 1 wt% of the mass of methyl phenylcarbamate.

[0106] The condensation reaction was carried out at a temperature of 120°C for 0.5 hours.

[0107] The preparation method of the sulfonic acid ionic liquid catalyst includes the following steps:

[0108] (1) Triethylamine and acetonitrile are mixed to obtain a first mixed solution, and 1,3-propanesulfonyl lactone and acetonitrile are mixed to obtain a second mixed solution;

[0109] Wherein, the molar ratio of triethylamine to acetonitrile is 1:3.0; the molar ratio of 1,3-propanesulfonyl lactone to acetonitrile is 1:3.0;

[0110] (2) The second mixed solution is added dropwise to the first mixed solution at a rate of 2.5 s / drop to carry out a single reaction, followed by a first washing and a first drying to obtain the intermediate product;

[0111] The temperature of the first reaction was 65°C, and the time was 48 hours.

[0112] The first washing solution used is tetrahydrofuran, and the washing is performed 5 times; the first drying temperature is 70°C, and the time is 36 hours.

[0113] (3) Mix the intermediate product and deionized water to obtain a third mixed solution, and mix phosphoric acid and deionized water to obtain a fourth mixed solution;

[0114] Wherein, the molar ratio of the intermediate product to deionized water is 1:20; the molar ratio of phosphoric acid to deionized water is 1:20;

[0115] (4) The fourth solution is added dropwise to the third solution at a rate of 2.5 s / drop to carry out a secondary reaction, and then the second washing and the second drying are carried out in sequence to obtain the sulfonic acid ionic liquid catalyst;

[0116] The secondary reaction was carried out at a temperature of 75°C for 36 hours.

[0117] The second washing solution used is tetrahydrofuran, and the washing is performed 5 times; the second drying temperature is 70°C, and the time is 36 hours.

[0118] Example 4

[0119] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0120] In this embodiment, the preparation method of the sulfonic acid ionic liquid catalyst is adjusted as follows:

[0121] A mixture of triethylamine, ethyl acetate and 1,3-propanesulfonyl lactone was reacted once, followed by a first wash and a first dry to give the intermediate product.

[0122] The intermediate product, deionized water, and sulfuric acid are mixed and subjected to a secondary reaction, followed by a second washing and a second drying, to obtain the sulfonic acid ionic liquid catalyst.

[0123] Example 5

[0124] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0125] In this embodiment, the temperature of the condensation reaction is adjusted to 50°C.

[0126] Example 6

[0127] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0128] In this embodiment, the temperature of the condensation reaction is adjusted to 130°C.

[0129] Example 7

[0130] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0131] In this embodiment, the mass of the sulfonic acid ionic liquid catalyst is adjusted to 40 wt% of the mass of the phenylcarbamate.

[0132] Example 8

[0133] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0134] In this embodiment, the mass of the sulfonic acid ionic liquid catalyst is adjusted to 0.5 wt% of the mass of the phenylcarbamate.

[0135] Example 9

[0136] This embodiment provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0137] In this embodiment, the molar ratio of phenylcarbamate and trioxymethylene is adjusted to 3.0:1.

[0138] Comparative Example 1

[0139] This comparative example provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0140] In this comparative example, the trioxymethylene was adjusted to an equal amount of formaldehyde.

[0141] Comparative Example 2

[0142] This comparative example provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0143] In this comparative example, the sulfonic acid ionic liquid catalyst was adjusted to an equal amount of triethylamine sulfate.

[0144] Comparative Example 3

[0145] This comparative example provides a method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst. The only difference between this method and Example 1 is that:

[0146] In this comparative example, the triethylamine in step (1) of the method for preparing the sulfate ionic liquid catalyst is adjusted to an equal amount of pyridine.

[0147] The diphenylmethane dicarboxylate provided in the above examples and comparative examples were sampled and detected by gas chromatography. The yield and selectivity of the diphenylmethane dicarboxylate were analyzed and calculated. The results are shown in Table 1.

[0148] Table 1

[0149]

[0150] According to Table 1, the following points can be observed:

[0151] (1) Comprehensive analysis of Examples 1-3 shows that the method provided by the present invention can synthesize diphenylmethane dicarboxylate under solvent-free conditions with high catalytic efficiency; and the catalyst can be recovered through simple phase separation, thereby achieving efficient conversion of phenylcarboxylate and efficient synthesis of diphenylmethane dicarboxylate.

[0152] (2) A comprehensive analysis of Examples 1 and 4 shows that the selection of process conditions during the preparation of the sulfonic acid ionic liquid catalyst will affect the catalytic effect of the catalyst;

[0153] Compared to Example 1, the preparation method provided in Example 4 results in a decrease in catalyst yield from 95% to 88%;

[0154] (3) Comprehensive analysis of Examples 1 and 5-6 shows that a higher temperature in the condensation reaction will lead to excessive reaction and the generation of byproducts such as 3-MDC, which will reduce product selectivity; while a lower temperature will lead to a slower reaction rate.

[0155] A comprehensive analysis of Examples 1 and 7-8 shows that an excessive amount of sulfur ionic liquid catalyst added during the condensation reaction will lead to over-reaction and the generation of byproducts such as 3-MDC, reducing product selectivity; while an insufficient amount will result in a slower reaction rate.

[0156] A comprehensive analysis of Examples 1 and 9 shows that an excessive amount of paraformaldehyde added during the condensation reaction can lead to over-condensation, generating byproducts and reducing product selectivity.

[0157] (4) Comprehensive analysis of Example 1 and Comparative Example 1 shows that if the trioxymethylene is adjusted to an equal amount of formaldehyde, the reaction system will become a liquid-liquid two-phase reaction, the reaction rate will slow down, and the product yield will decrease.

[0158] A comprehensive analysis of Example 1 and Comparative Example 2 shows that if the sulfonic acid ionic liquid catalyst is adjusted to an equal amount of triethylamine sulfate, the product yield will decrease, and the catalyst cannot be self-separated after the reaction.

[0159] A comprehensive analysis of Example 1 and Comparative Example 3 shows that adjusting triethylamine to an equal amount of pyridine leads to a decrease in product yield, and the catalyst cannot be self-separated after the reaction.

[0160] In summary, this invention utilizes a sulfonic acid ionic liquid catalyst to synthesize diphenylmethane dicarboxylate under solvent-free conditions, significantly reducing the required reactor size. Furthermore, the catalyst can be recovered through simple phase separation after the sulfonic acid ionic liquid reaction, demonstrating promising prospects for industrial application.

[0161] The applicant declares that the specific embodiments described above further illustrate the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing diphenylmethane dicarboxylate using a self-separating sulfonic acid ionic liquid catalyst, characterized in that, The method includes: The diphenylmethane dicarboxylate is obtained by condensation reaction of a mixture of phenylcarboxylate, trioxymethane, and sulfonic acid ionic liquid catalyst.

2. The method according to claim 1, characterized in that, The phenylcarbamate includes methyl phenylcarbamate or ethyl phenylcarbamate; The structural formula of the sulfonic acid ionic liquid catalyst is: Where n is 1 or 2; X - It includes any one of sulfate ions, p-toluenesulfonate ions, or phosphate ions.

3. The method according to claim 2, characterized in that, The molar ratio of phenylcarbamate to trioxymethylene is 5.0~25.0:1; The mass of the sulfonic acid ionic liquid catalyst is 1 to 30 wt% of the mass of the phenylcarbamate.

4. The method according to claim 1, characterized in that, The temperature of the condensation reaction is 60~120℃; The condensation reaction takes 0.5 to 10 hours.

5. The method according to claim 1, characterized in that, The condensation reaction is followed by a cooling process and a phase separation process.

6. The method according to claim 1, characterized in that, The sulfonic acid ionic liquid catalyst was prepared using the following method: (1) Triethylamine and solvent are mixed to obtain a first mixed solution, and sulfolactone and solvent are mixed to obtain a second mixed solution; (2) The second mixed solution is added dropwise to the first mixed solution to carry out a reaction, and then the first washing and first drying are carried out in sequence to obtain the intermediate product; (3) Mix the intermediate product and the inorganic solvent to obtain a third mixed solution, and mix the acid solution and the inorganic solvent to obtain a fourth mixed solution; (4) The fourth solution is added dropwise to the third solution to carry out a secondary reaction, and then the second washing and the second drying are carried out in sequence to obtain the sulfonic acid ionic liquid catalyst.

7. The method according to claim 6, characterized in that, The solvent in step (1) includes any one or a combination of at least two of ethyl acetate, chloroform, or acetonitrile; The sulfonyl lactone in step (1) includes 1,3-propanesulfonyl lactone or 1,4-butanesulfonyl lactone; The molar ratio of triethylamine to solvent in step (1) is 1:1.5~5.0; The molar ratio of sulfonyl lactone and solvent in step (1) is 1:1.5~5.

0.

8. The method according to claim 6, characterized in that, The temperature of the first reaction in step (2) is 60~65℃ and the time is 12~72h; The dropping rate in step (2) is 2~3 s / drop; Step (2) The washing solution used for the first washing includes any one or a combination of at least two of ethyl acetate, chloroform or tetrahydrofuran.

9. The method according to claim 6, characterized in that, The inorganic solvent in step (3) includes deionized water; The acid solution mentioned in step (3) includes any one of sulfuric acid, p-toluenesulfonic acid, or phosphoric acid; The molar ratio of the intermediate product to the inorganic solvent in step (3) is 1:20~40; The molar ratio of acid and inorganic solvent in step (3) is 1:20~40.

10. The method according to claim 6, characterized in that, The dropping rate in step (4) is 2~3 s / drop; The temperature of the secondary reaction in step (4) is 75~80℃, and the time is 12~72h; Step (4) The washing solution used for the second washing includes any one or a combination of at least two of ethyl acetate, chloroform or tetrahydrofuran.

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