Production method of anhydrous p-toluenesulfonic acid

Abstract

The invention discloses a production method of anhydrous p-toluenesulfonic acid, and belongs to the technical field of organic synthesis, at-20 to-15 DEG C, a sulfur trioxide-sulfur dioxide solution is added into toluene for reaction to obtain a reaction solution, the reaction solution adopts silica gel resin to adsorb an ortho-meta-position benzenesulfonic acid mixture, so that p-toluenesulfonic acid is separated from the reaction solution, and the anhydrous p-toluenesulfonic acid is obtained. Anhydrous p-toluenesulfonic acid is obtained; the production method of the anhydrous p-toluenesulfonic acid is ingenious in design, toluene and sulfur trioxide are adopted to generate methyl benzenesulfonic acid, and methyl benzenesulfonic acid and sulfur dioxide are adopted to generate methyl pyrosulfinic acid; van der Waals' force is formed between the obtained methylpyrosulfinic acid and the silica gel resin, Van der Waals' force formed by p-toluene pyrosulfinic acid is weakest, and when the temperature is raised to about-8 DEG C, the formed Van der Waals' force is broken, so that desorption is realized; the o-tosylsulfinic acid and the meta-tosylsulfinic acid can be desorbed with the resin at a high temperature, so that the separation of p-toluenesulfonic acid from o-tosylsulfinic acid and meta-tosylsulfinic acid is

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, in particular to a method for producing anhydrous p-toluenesulfonic acid. Background Art

[0002] p-Toluenesulfonic acid (PTS) is an important fine chemical raw material and a commonly used acid catalyst in organic synthesis. It is the main raw material for the synthesis of p-toluenesulfonyl chloride, p-cresol, and p-toluenesulfonamide. As an organic reaction catalyst, it is mainly used in esterification, acetalization, dehydration, alkylation, Beckmann rearrangement, polymerization and depolymerization.

[0003] There are two main industrial processes for p-toluenesulfonic acid. One is the toluene-sulfuric acid sulfonation method. When concentrated sulfuric acid sulfonates toluene, a large amount of water is generated, which reduces the concentration of concentrated sulfuric acid. When the concentration is lower than a certain value, the reaction is difficult to continue, so a large amount of waste acid is generated, which is not conducive to environmental protection. The second is the toluene-sulfur trioxide sulfonation method, which is an advanced sulfonation process that can achieve stoichiometric reaction. In theory, no waste acid and wastewater are generated, but sulfur trioxide directly sulfonates toluene, and the reaction is violent, resulting in the production of ortho-, meta-, and over-sulfonated products. In general, a certain amount of water is added to the system in post-treatment to make p-toluenesulfonic acid form monohydrate p-toluenesulfonic acid crystals to achieve the purpose of purification. At present, the bulk of the market is sold as monohydrate p-toluenesulfonic acid, but in the organic catalytic reaction involving p-toluenesulfonic acid, anhydrous p-toluenesulfonic acid is more required to participate in the reaction. Therefore, it is of certain market value to develop a high-purity anhydrous p-toluenesulfonic acid preparation method and industrial equipment.

[0004] The literature (J.Phys.Chem.A 2018, 122, 3, 762–772) studied the mutual hydrogen bonding between p-toluenesulfonic acid and water molecules through the stretching movement of the sulfonate -OH by infrared absorption spectroscopy. The literature pointed out that the crystal water of p-toluenesulfonic acid exists independently in organic solvents. When in aqueous solution, there is hydrogen bonding between water molecules and π electrons. The report only studied the intermolecular interaction between p-toluenesulfonic acid-hydrate, and there is no specific method for preparing anhydrous p-toluenesulfonic acid. The literature (Org.Process Res.Dev.2021, 25, 1383-1390) reported a method for preparing p-toluenesulfonic acid by dehydrating p-toluenesulfonic acid monohydrate in methyl tert-butyl ether, with a yield of 65%. The yield of the literature method is low, and only one set of data is provided. It does not involve the screening and comparison of other solvents, and there is no complete introduction to the separation process. The document (Research on the Production Technology of Anhydrous p-toluenesulfonic Acid [J]. Zhejiang Chemical Industry, 2015, 46 (08)) reports a method for preparing anhydrous p-toluenesulfonic acid, wherein the anhydrous p-toluenesulfonic acid is obtained by directly concentrating the dichloromethane in the reaction solution and then cooling and crystallizing. In this method, the solubility of p-toluenesulfonic acid in dichloromethane is too high, resulting in a too fast crystallization speed after concentration and cooling, and the crystals are seriously entrained with impurities. Simple washing cannot remove impurities, and the purification effect is poor. The produced anhydrous p-toluenesulfonic acid is low in purity and cannot meet the purity requirements of catalytic organic reactions. None of the above reports involve a complete process for preparing high-purity anhydrous p-toluenesulfonic acid. Summary of the invention

[0005] In order to solve the problem of synthesizing anhydrous p-toluenesulfonic acid, the present invention aims to provide a method for producing anhydrous p-toluenesulfonic acid.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for producing anhydrous p-toluenesulfonic acid comprises the following steps: adding a sulfur trioxide-sulfur dioxide solution into toluene at -20 to -15°C to react and obtaining a reaction liquid; using a silica gel resin to adsorb an o- and m-benzenesulfonic acid mixture on the reaction liquid to separate p-toluenesulfonic acid from the reaction liquid and obtain anhydrous p-toluenesulfonic acid.

[0008] Preferably, the method comprises the following steps:

[0009] ① Add sulfur trioxide to the sulfur dioxide solution, stir and dissolve, and cool to -20 to -15°C to form a sulfur trioxide-sulfur dioxide solution; the mass ratio of the sulfur dioxide solution to sulfur trioxide is 10:0.5 to 2;

[0010] ② Add toluene to the reaction kettle, cool it to -20 to -15°C, add the sulfur trioxide-sulfur dioxide solution obtained in step ① thereto, the temperature of the reaction kettle is -20 to -15°C during the addition, keep the temperature for reaction for 1 to 3 hours after the addition is completed, and obtain a sulfur dioxide solution of p-toluenesulfonic acid; wherein the molar ratio of toluene to sulfur trioxide in step ① is 1 to 1.2:1;

[0011] ③ Add the silica gel resin to the sulfur dioxide solution of p-toluenesulfonic acid obtained in step ②, raise the temperature to -10 to -5°C, keep stirring for 2 to 4 hours, and filter by pressure to obtain an adsorption resin and a filtrate;

[0012] ④ After removing sulfur dioxide from the filtrate obtained in step ③ by vacuum distillation, the temperature is lowered to -18 to -15°C, crystallized for 2 to 4 hours, and filtered to obtain anhydrous p-toluenesulfonic acid and mother liquor, wherein the mother liquor is used in the next batch of crystallization process;

[0013] ⑤ The adsorption resin obtained in step ③ is heated to 70-80° C. for desorption treatment for 2-4 hours, filtered, and the filter cake is washed with toluene to obtain a mixture of o-toluenesulfonic acid and m-toluenesulfonic acid and a regenerated silica gel resin, wherein the regenerated silica gel resin can be used in the next batch of adsorption process.

[0014] Preferably, the silicone resin is one or more of NDA-99, DAX-1, and NDA-150.

[0015] Preferably, the mass ratio of the silica gel resin in step ③ to the toluene in step ② is 0.1-0.5:10.

[0016] Preferably, the sulfur trioxide-sulfur dioxide solution obtained in step ① is added dropwise at a rate of 5 to 10 drops per minute.

[0017] Preferably, the desorption temperature in step ⑤ is 75-80°C.

[0018] Preferably, the mass ratio of sulfur dioxide solution to sulfur trioxide is 10:1-2.

[0019] Preferably, the molar ratio of toluene to sulfur trioxide in step ① is 1.05-1.1:1. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the liquid phase spectrum of p-toluenesulfonic acid product.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The production method of anhydrous p-toluenesulfonic acid of the present invention is ingeniously designed. First, toluene and sulfur trioxide are used to generate methylbenzenesulfonic acid (including p-toluenesulfonic acid, o-toluenesulfonic acid, and m-toluenesulfonic acid), and methylbenzenesulfonic acid and sulfur dioxide are used to generate methylpyrosulfinic acid, the structural formula of which is Secondly, van der Waals force is formed between the obtained methylpyrosulfinic acid and the silica gel resin. Among them, the van der Waals force formed by p-toluenepyrosulfinic acid is the weakest due to the electron-donating effect of the methyl group. When the temperature rises to about -8°C, the formed van der Waals force breaks and desorption occurs. The van der Waals force formed between ortho- and meta-toluenesulfinic acid and the resin is relatively stable, and high temperature is required to achieve desorption, thereby achieving the separation of p-toluenesulfonic acid from ortho- and meta-toluenesulfonic acid. DETAILED DESCRIPTION

[0023] The object of the present invention is to provide a method for producing anhydrous p-toluenesulfonic acid. The present invention will be further described below in conjunction with specific embodiments.

[0024] The reaction equation for the reaction of toluene and sulfur trioxide is:

[0025]

[0026] The toluenesulfonic acid formed in this reaction reacts with sulfur dioxide to form The formed methylpyrosulfinic acid forms a van der Waals force with the silica gel resin. Among them, p-toluenepyrosulfinic acid has the weakest van der Waals force due to the electron-donating effect of the methyl group. When the temperature rises to about -8°C, the formed van der Waals force breaks and desorption occurs. The van der Waals force formed between o- and m-benzenesulfinic acid and the resin is relatively stable, and high temperature is required to achieve desorption, thereby achieving the separation of p-toluenesulfonic acid and o- and m-benzenesulfonic acid.

[0027] The weight content ratios of p-toluenesulfonic acid, o-toluenesulfonic acid, and m-toluenesulfonic acid in the embodiments of the present invention are determined by gas phase derivatization, and the chromatographic conditions are shown in Table 1. The liquid phase spectra of the p-toluenesulfonic acid product in Examples 1 to 5 are shown in Figure 1 shown.

[0028] Table 1 Chromatographic conditions of gas phase derivatization

[0029]

[0030]

[0031] Embodiment 1 A method for producing anhydrous p-toluenesulfonic acid comprises the following steps:

[0032] ① Add 80g of sulfur trioxide to 1600g of sulfur dioxide solution, stir to dissolve, and cool to -20℃ to form a sulfur trioxide-sulfur dioxide solution;

[0033] ② Add 92g of toluene to the reactor, cool it to -20°C, and add the sulfur trioxide-sulfur dioxide solution obtained in step ① thereto. The temperature of the reactor is -20°C during the addition. After the addition is completed, keep the temperature for 3 hours to obtain a sulfur dioxide solution of p-toluenesulfonic acid; (wherein the content of p-toluenesulfonic acid accounts for 96.7%, o-toluenesulfonic acid 3.1%, and m-toluenesulfonic acid 0.2%);

[0034] ③ Add 0.4 g of silica gel resin NDA-150 and 0.52 g of silica gel resin DAX-1 to the sulfur dioxide solution of p-toluenesulfonic acid obtained in step ②, heat to -10°C, keep stirring for 4 hours, filter press to obtain an adsorption resin and a filtrate; the p-toluenesulfonic acid content in the filtrate is 98.9%, o-toluenesulfonic acid is 1.1%, and m-toluenesulfonic acid is 0%;

[0035] ④ The filtrate obtained in step ③ was subjected to reduced pressure distillation to remove sulfur dioxide, cooled to -18°C, crystallized for 2 hours, and filtered to obtain anhydrous p-toluenesulfonic acid (165.3 g, yield 96.0%) and mother liquor, wherein the mother liquor was used in the next batch of crystallization process; the content of anhydrous p-toluenesulfonic acid obtained was 99.8%, o-toluenesulfonic acid was 0.2%, and m-toluenesulfonic acid was 0%;

[0036] ⑤ The adsorption resin obtained in step ③ is heated to 70° C. for desorption treatment for 2 hours, filtered, and the filter cake is washed with toluene to obtain a mixture of o-toluenesulfonic acid and m-toluenesulfonic acid and regenerated silica gel resin, wherein the regenerated silica gel resin can be used in the next batch of adsorption process.

[0037] Embodiment 2 A method for producing anhydrous p-toluenesulfonic acid comprises the following steps:

[0038] ① Add 80g of sulfur trioxide to 400g of sulfur dioxide solution, stir to dissolve, and cool to -15°C to form a sulfur trioxide-sulfur dioxide solution;

[0039] ② Add 110.4 g of toluene to the reactor, cool to -15°C, and add the sulfur trioxide-sulfur dioxide solution obtained in step ① thereto. The temperature of the reactor is -15°C during the addition. After the addition is completed, keep the temperature for 1 hour to obtain a p-toluenesulfonic acid sulfur dioxide solution; wherein the p-toluenesulfonic acid content is 96.5%, the o-toluenesulfonic acid content is 3.2%, and the m-toluenesulfonic acid content is 0.3%;

[0040] ③ Add 5.52 g of silica gel resin NDA-150 to the sulfur dioxide solution of p-toluenesulfonic acid obtained in step ②, heat to -5°C, keep warm and stir for 2 hours, filter press to obtain an adsorption resin and a filtrate; the p-toluenesulfonic acid content in the filtrate is 98.7%, o-toluenesulfonic acid is 1.3%, and m-toluenesulfonic acid is 0%;

[0041] ④ After removing sulfur dioxide from the filtrate obtained in step ③ by vacuum distillation, the temperature was lowered to -18°C, crystallized for 4 hours, and filtered to obtain anhydrous p-toluenesulfonic acid (168.4 g, yield 97.8%) and mother liquor, wherein the mother liquor was used in the next batch of crystallization process;

[0042] ⑤ The adsorption resin obtained in step ③ is heated to 80° C. for desorption treatment for 2 hours, filtered, and the filter cake is washed with toluene to obtain a mixture of o-toluenesulfonic acid and m-toluenesulfonic acid and regenerated silica gel resin, wherein the regenerated silica gel resin can be used in the next batch of adsorption process.

[0043] Embodiment 3 A method for producing anhydrous p-toluenesulfonic acid comprises the following steps:

[0044] ① Add 80g of sulfur trioxide to 800g of sulfur dioxide solution, stir to dissolve, and cool to -16°C to form a sulfur trioxide-sulfur dioxide solution; the mass ratio of sulfur dioxide solution to sulfur trioxide is 10:1;

[0045] ② Add 101.2 g of toluene to the reactor, cool to -16°C, and dropwise add the sulfur trioxide-sulfur dioxide solution obtained in step ① at a dropping speed of 5 drops / minute. Control the temperature of the reactor to be -16°C. After the addition is completed, keep the reaction temperature for 1.5 hours to obtain a p-toluenesulfonic acid sulfur dioxide solution; wherein the p-toluenesulfonic acid content is 96.9%, the o-toluenesulfonic acid content is 2.9%, and the m-toluenesulfonic acid content is 0.2%;

[0046] ③ Add 2.05 g of silica gel resin NDA-99 to the sulfur dioxide solution of p-toluenesulfonic acid obtained in step ②, heat to -6°C, keep warm and stir for 3 hours, filter by pressure to obtain an adsorption resin and a filtrate; the p-toluenesulfonic acid content in the filtrate is 99.1%, o-toluenesulfonic acid is 0.9%, and m-toluenesulfonic acid is 0%;

[0047] ④ After removing sulfur dioxide from the filtrate obtained in step ③ by vacuum distillation, the temperature was lowered to -16°C, crystallized for 2.5 hours, and filtered to obtain anhydrous p-toluenesulfonic acid (169.1 g, yield 98.2%) and mother liquor, wherein the mother liquor was used in the next batch of crystallization process;

[0048] ⑤ The adsorption resin obtained in step ③ is heated to 75° C. for desorption treatment for 2.5 hours, filtered, and the filter cake is washed with toluene to obtain a mixture of o-toluenesulfonic acid and m-toluenesulfonic acid and regenerated silica gel resin, wherein the regenerated silica gel resin can be used in the next batch of adsorption process.

[0049] Embodiment 4 A method for producing anhydrous p-toluenesulfonic acid comprises the following steps:

[0050] ① Add 80g of sulfur trioxide to 457g of sulfur dioxide solution, stir to dissolve, and cool to -18°C to form a sulfur trioxide-sulfur dioxide solution;

[0051] ② Add 96.6 g of toluene to the reactor, cool to -16°C, and dropwise add the sulfur trioxide-sulfur dioxide solution obtained in step ① at a dropping speed of 10 drops / minute. Control the temperature of the reactor to be -16°C. After the addition is completed, keep the reaction temperature for 1.5 hours to obtain a p-toluenesulfonic acid sulfur dioxide solution; wherein the p-toluenesulfonic acid content is 97.1%, the o-toluenesulfonic acid content is 2.5%, and the m-toluenesulfonic acid content is 0.4%;

[0052] ③ Add 3.87 g of silica gel resin DAX-1 to the sulfur dioxide solution of p-toluenesulfonic acid obtained in step ②, heat to -6°C, keep warm and stir for 2.5 hours, filter press to obtain an adsorption resin and a filtrate; the p-toluenesulfonic acid content in the filtrate is 99.2%, o-toluenesulfonic acid is 0.8%, and m-toluenesulfonic acid is 0%;

[0053] ④ After removing sulfur dioxide from the filtrate obtained in step ③ by vacuum distillation, the temperature was lowered to -16°C, crystallized for 2.5 hours, and filtered to obtain anhydrous p-toluenesulfonic acid (168.9 g, yield 98.1%) and mother liquor, wherein the mother liquor was used in the next batch of crystallization process;

[0054] ⑤ The adsorption resin obtained in step ③ is heated to 78° C. for desorption treatment for 2.5 hours, filtered, and the filter cake is washed with toluene to obtain a mixture of o-toluenesulfonic acid and m-toluenesulfonic acid and regenerated silica gel resin, wherein the regenerated silica gel resin can be used in the next batch of adsorption process.

[0055] Embodiment 5 A method for producing anhydrous p-toluenesulfonic acid comprises the following steps:

[0056] ① Add 80g of sulfur trioxide to 533.3g of sulfur dioxide solution, stir to dissolve, and cool to -16°C to form a sulfur trioxide-sulfur dioxide solution;

[0057] ② Add 101.2 g of toluene to the reactor, cool to -18°C, and dropwise add the sulfur trioxide-sulfur dioxide solution obtained in step ① at a dropping speed of 8 drops / minute. Control the temperature of the reactor to be -18°C. After the addition is completed, keep the reaction temperature for 2.5 hours to obtain a p-toluenesulfonic acid sulfur dioxide solution; wherein the p-toluenesulfonic acid content is 97.1%, the o-toluenesulfonic acid content is 2.6%, and the m-toluenesulfonic acid content is 0.3%;

[0058] ③ Add 1.5 g of silica gel resin NDA-99 and 1.5 g of silica gel resin DAX-1 to the sulfur dioxide solution of p-toluenesulfonic acid obtained in step ②, heat to -8°C, keep warm and stir for 3.5 hours, filter press to obtain an adsorption resin and a filtrate; the p-toluenesulfonic acid content in the filtrate is 99.2%, o-toluenesulfonic acid is 0.8%, and m-toluenesulfonic acid is 0%;

[0059] ④ After removing sulfur dioxide from the filtrate obtained in step ③ by vacuum distillation, the temperature was lowered to -16°C, crystallized for 3.5 hours, and filtered to obtain anhydrous p-toluenesulfonic acid (169.4 g, yield 98.4%) and mother liquor, wherein the mother liquor was used in the next batch of crystallization process;

[0060] ⑤ The adsorption resin obtained in step ③ is heated to 80° C. for desorption treatment for 3.5 hours, filtered, and the filter cake is washed with toluene to obtain a mixture of o-toluenesulfonic acid and m-toluenesulfonic acid and regenerated silica gel resin, wherein the regenerated silica gel resin can be used in the next batch of adsorption process.

Claims

1. A method for producing anhydrous p-toluenesulfonic acid, characterized in that: At -20 to -15°C, sulfur trioxide-sulfur dioxide solution is added to toluene to react to obtain a reaction solution, and the reaction solution is adsorbed with an o- and m-benzenesulfonic acid mixture by silica gel resin, thereby separating p-toluenesulfonic acid from the reaction solution to obtain anhydrous p-toluenesulfonic acid.

2. The method for producing anhydrous p-toluenesulfonic acid according to claim 1, wherein: The following steps are involved: ① Add sulfur trioxide to the sulfur dioxide solution, stir to dissolve, and cool to -20 to -15°C to form a sulfur trioxide-sulfur dioxide solution; The mass ratio of sulfur dioxide solution to sulfur trioxide is 10:0.5-2; ② Add toluene to the reaction kettle, cool it to -20 to -15°C, add the sulfur trioxide-sulfur dioxide solution obtained in step ① thereto, the temperature of the reaction kettle is -20 to -15°C during the addition, keep the temperature for reaction for 1 to 3 hours after the addition is completed, and obtain a sulfur dioxide solution of p-toluenesulfonic acid; wherein the molar ratio of toluene to sulfur trioxide in step ① is 1 to 1.2:1; ③ Add the silica gel resin to the sulfur dioxide solution of p-toluenesulfonic acid obtained in step ②, raise the temperature to -10 to -5°C, keep stirring for 2 to 4 hours, and filter by pressure to obtain an adsorption resin and a filtrate; ④ After removing sulfur dioxide from the filtrate obtained in step ③ by vacuum distillation, the temperature is lowered to -18 to -15°C, crystallized for 2 to 4 hours, and filtered to obtain anhydrous p-toluenesulfonic acid and mother liquor, wherein the mother liquor is used in the next batch of crystallization process; ⑤ The adsorption resin obtained in step ③ is heated to 70-80° C. for desorption treatment for 2-4 hours, filtered, and the filter cake is washed with toluene to obtain a mixture of o-toluenesulfonic acid and m-toluenesulfonic acid and a regenerated silica gel resin, wherein the regenerated silica gel resin can be used in the next batch of adsorption process.

3. The method for producing anhydrous p-toluenesulfonic acid according to claim 2, characterized in that: The silicone resin is one or more of NDA-99, DAX-1 and NDA-150.

4. The method for producing anhydrous p-toluenesulfonic acid according to claim 2, characterized in that: The mass ratio of the silica gel resin in step ③ to the toluene in step ② is 0.1-0.5:

10.

5. The method for producing anhydrous p-toluenesulfonic acid according to claim 2, characterized in that: In step ②, the sulfur trioxide-sulfur dioxide solution obtained in step ① is added dropwise at a rate of 5 to 10 drops per minute.

6. The method for producing anhydrous p-toluenesulfonic acid according to claim 2, characterized in that: The desorption temperature in step ⑤ is 75-80°C.

7. The method for producing anhydrous p-toluenesulfonic acid according to claim 2, characterized in that: The mass ratio of sulfur dioxide solution to sulfur trioxide is 10:1-2.

8. The method for producing anhydrous p-toluenesulfonic acid according to claim 2, characterized in that: The molar ratio of toluene to sulfur trioxide in step ① is 1.05-1.1:1.

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