A kind of preparation method of p-toluenesulfonic acid

Abstract

The invention provides a method for preparing p-toluenesulfonic acid, and relates to the field of synthesis technology. The invention uses a silicon dioxide carrier to load a heteropoly acid to obtain a heteropoly acid@silicon dioxide sulfone formation inhibitor, thereby reducing the sulfone formation ratio of toluene in a sulfonation reaction. In addition, the invention uses a sulfur trioxide organic solution as a sulfonating agent, thereby reducing the sulfonation temperature and avoiding the generation of waste acid. The heteropoly acid@silicon dioxide of the invention is easy to separate, purify and recycle, thereby realizing the clean production of p-toluenesulfonic acid.

Description

Technical Field

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

[0002] p-Toluenesulfonic acid is a non-oxidizing organic strong acid and one of the important fine chemical products. It is widely used in synthetic medicines, pesticides, dyes and organic synthesis. It is also used as a stabilizer for polymerization reactions and a catalyst for organic synthesis.

[0003] At present, the main method for preparing p-toluenesulfonic acid is toluene sulfonation, and the sulfonation reagents used are concentrated sulfuric acid, chlorosulfonic acid and sulfur trioxide. Among them, chlorosulfonic acid has high production costs due to its high price and lacks market competitiveness. Concentrated sulfuric acid and sulfur trioxide are used as sulfonation reagents. During the reaction, about 8% of toluene will be converted into by-product xylene sulfone, resulting in a decrease in product yield.

[0004] Existing research has found that inhibiting the formation of xylene sulfone, a byproduct of toluene sulfonation, is the key to achieving efficient synthesis of p-toluenesulfonic acid. Currently, in order to inhibit the formation of xylene sulfone, the following methods are mainly used:

[0005] 1) Reasonably control the process conditions of sulfonation reaction, such as the amount of sulfonating agent, reaction temperature and the use of new sulfonation equipment;

[0006] 2) Add appropriate inhibitors to the sulfonation reaction system. The commonly used inhibitor in existing literature reports is acetic acid, but the use of acetic acid is difficult to post-process, and acetic acid will corrode the equipment, and the material requirements of the reaction device are relatively high. U.S. Patent No. 3,789,067 uses sodium sulfite as an inhibitor of toluene sulfonation reaction. Sodium sulfite has an obvious inhibitory effect only when sulfur dioxide is used as a solvent. The reaction system in the sulfur dioxide solvent is porridge-like and difficult to stir, and the introduction of sodium sulfite increases the difficulty of post-processing. Summary of the invention

[0007] In view of this, the present invention provides a method for preparing p-toluenesulfonic acid. The present invention uses silicon dioxide loaded with heteropoly acid (heteropoly acid@silica) as a sulfone formation inhibitor, thereby significantly reducing the sulfone formation ratio of toluene in the sulfonation reaction. At the same time, the heteropoly acid@silica of the present invention is easy to separate, can be recycled, and has a long service life.

[0008] The present invention is achieved by adopting the following technical solutions:

[0009] A method for preparing p-toluenesulfonic acid comprises the following steps:

[0010] S1. Preparation of silica carrier

[0011] The nano-silicon dioxide powder is soaked in dilute hydrochloric acid for 9 hours to 11 hours, filtered and washed, and then calcined at 300°C to 400°C for 1 to 3 hours to obtain a silicon dioxide carrier with a pore size of 300nm to 450nm; in the present invention, the nano-silicon dioxide powder is prepared by the following method:

[0012] Add 540.0mL of methanol and 54.0mL of water into a three-necked flask, start stirring, control the system temperature at 20°C, add 75.6mL of 25wt% ammonia water and 64.8mL of ethyl orthosilicate dropwise, and continue the reaction for 1.5h after the addition is complete. The product is centrifuged, the solid is washed with methanol and dried in an air flow at 180°C to obtain nano-silica powder.

[0013] S2. Preparation of heteropolyacid@silicon dioxide

[0014] Dissolving a heteroacid in water to obtain a heteroacid aqueous solution with a mass concentration of 3% to 5%; soaking the silica carrier in the heteroacid aqueous solution with a solid-liquid ratio of 0.08 to 0.12 g / mL, stirring at 40° C. to 45° C. for 2 h to 8 h, centrifuging, washing, and drying to obtain heteropolyacid-loaded silica, i.e., heteropolyacid@silica;

[0015] S3, sulfonation reaction to prepare p-toluenesulfonic acid

[0016] Mixing an organic solvent and toluene to obtain a toluene organic solvent; passing the organic solvent into sulfur trioxide to obtain a sulfur trioxide organic solvent;

[0017] Adding the heteropolyacid@silicon dioxide to the toluene organic solution, and then dropping the sulfur trioxide organic solution, and continuing to stir and react for 30 minutes to 70 minutes after the dropwise addition is completed, wherein the molar ratio of toluene to sulfur trioxide is 1.3:1 to 1.1:1;

[0018] After the reaction is completed, the heteropoly acid@silicon dioxide is removed by filtering to obtain a reaction solution;

[0019] S4, cooling the reaction solution to 0-5°C for crystallization, obtaining a solid product after centrifugation, and washing and drying the solid product to obtain p-toluenesulfonic acid solid.

[0020] Preferably, the mass concentration of the dilute hydrochloric acid is 10% to 15%.

[0021] Preferably, the heteroacid is one of tungstophosphoric acid, molybdophosphoric acid and silicotungstic acid.

[0022] Preferably, the organic solvent is one of dichloromethane, 1,2-dichloroethane, chloroform or carbon tetrachloride.

[0023] Preferably, the mass ratio of the heteropolyacid@silica to the toluene is 0.03:1 to 0.08:1.

[0024] Preferably, the reaction temperature of step S3 is 20°C to 30°C.

[0025] Preferably, the drying temperature in step S4 is 45°C to 60°C.

[0026] Preferably, the drying time in step S4 is 20 min to 60 min.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The invention provides a method for preparing p-toluenesulfonic acid, which is to obtain a heteropolyacid@silica sulfone-forming inhibitor by using a silicon dioxide carrier to load a heteropolyacid. By adding the inhibitor, the sulfone-forming ratio of toluene in the sulfonation reaction can be effectively reduced, the generation of each isomer in the p-toluenesulfonic acid can be reduced, and the p-toluenesulfonic acid yield can be improved. In addition, the invention uses sulfur trioxide organic solution as a sulfonating agent, reduces the sulfonation temperature, and avoids the generation of waste acid. The heteropolyacid@silica of the invention is convenient for separation, purification and recycling, and realizes the clean production of p-toluenesulfonic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 HPLC charts of toluenesulfonic acid in Examples 1 to 4 and Comparative Example 1. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the embodiments.

[0031] Example 1

[0032] A method for preparing p-toluenesulfonic acid, the specific steps are as follows:

[0033] S1. Preparation of silica carrier

[0034] The nano-silica powder was immersed in dilute hydrochloric acid with a mass concentration of 15%, and then filtered and washed after immersion for 9 hours, and then calcined at 330° C. for 3 hours to obtain a silica carrier with an average pore size of 368 nm;

[0035] S2. Preparation of tungstophosphoric acid@silicon dioxide

[0036] Dissolve 5.4g of tungstophosphoric acid in 112.5g of water to obtain a tungstophosphoric acid aqueous solution; soak 12.5g of the silica carrier in the tungstophosphoric acid aqueous solution, stir for 5h at 40°C, wash with deionized water after centrifugation, and dry at 120°C for 5h to obtain silica loaded with heteropoly acid, i.e., tungstophosphoric acid@silica;

[0037] S3, sulfonation reaction to prepare p-toluenesulfonic acid

[0038] Toluene and dichloromethane are mixed to obtain a toluene organic solution with a mass concentration of 42%; sulfur trioxide is introduced into dichloromethane to obtain a sulfur trioxide organic solution with a mass concentration of 22%;

[0039] Add 9.4g of the tungstophosphoric acid @ silicon dioxide to 320.0g of the toluene organic solution, then dropwise add 408.6g of the sulfur trioxide organic solution at a temperature of 25°C, and continue stirring and reacting for 50min after the dropwise addition is completed;

[0040] After the reaction is completed, the tungstophosphoric acid@silicon dioxide is removed by filtering to obtain a reaction solution;

[0041] S4, cooling the reaction solution to 5°C for crystallization, and obtaining a solid product after centrifugation. The solid product is washed and then dried at 55°C for 30 min to obtain p-toluenesulfonic acid solid.

[0042] Example 2

[0043] A method for preparing p-toluenesulfonic acid, the specific steps are as follows:

[0044] S1. Preparation of silica carrier

[0045] The nano-silica powder was immersed in dilute hydrochloric acid with a mass concentration of 15%, and then filtered and washed after immersion for 10 hours, and then calcined at 350° C. for 2 hours to obtain a silica carrier with an average pore size of 354 nm;

[0046] S2. Preparation of molybdophosphoric acid@silicon dioxide

[0047] Dissolve 4.1 g of molybdophosphoric acid in 83.6 g of water to obtain a molybdophosphoric acid aqueous solution; soak 9.5 g of the silica carrier in the molybdophosphoric acid aqueous solution, stir at 45° C. for 5 h, centrifuge and wash with deionized water, and dry at 120° C. for 5 h to obtain silica loaded with heteropoly acid, i.e., molybdophosphoric acid@silica;

[0048] S3, sulfonation reaction to prepare p-toluenesulfonic acid

[0049] Toluene and chloroform are mixed to obtain a toluene organic solution with a mass concentration of 38%; sulfur trioxide is introduced into chloroform to obtain a sulfur trioxide organic solution with a mass concentration of 18%;

[0050] Add 7.9 g of molybdophosphate@silicon dioxide to 350.0 g of the toluene organic solution, then dropwise add 509.9 g of the sulfur trioxide organic solution at a temperature of 25° C. After the dropwise addition is complete, continue stirring and reacting for 50 min;

[0051] After the reaction is completed, the molybdophosphoric acid@silicon dioxide is removed by filtering to obtain a reaction solution;

[0052] S4, cooling the reaction solution to 0°C for crystallization, and obtaining a solid product after centrifugation. The solid product is washed and then dried at 50°C for 40 min to obtain p-toluenesulfonic acid solid.

[0053] Example 3

[0054] A method for preparing p-toluenesulfonic acid, the specific steps are as follows:

[0055] S1, preparing a silica carrier, this step is the same as Example 2;

[0056] S2. Preparation of tungstophosphoric acid@silicon dioxide

[0057] Dissolve 5.5g of tungstophosphoric acid in 112.5g of water to obtain a tungstophosphoric acid aqueous solution; soak 12.5g of the silica carrier in the tungstophosphoric acid aqueous solution, stir for 5h at 45°C, wash with deionized water after centrifugation, and dry at 120°C for 5h to obtain silica loaded with heteropoly acid, i.e., tungstophosphoric acid@silica;

[0058] S3, sulfonation reaction to prepare p-toluenesulfonic acid

[0059] Toluene and carbon tetrachloride are mixed to obtain a toluene organic solution with a mass concentration of 40%; sulfur trioxide is introduced into the carbon tetrachloride to obtain a sulfur trioxide organic solution with a mass concentration of 20%;

[0060] Add 10.2g of the tungstophosphoric acid @ silicon dioxide to 320.0g of the toluene organic solution, then drop 428.1g of the sulfur trioxide organic solution at 25°C, and continue stirring and reacting for 50min after the dropwise addition is completed;

[0061] After the reaction is completed, the tungstophosphoric acid@silicon dioxide is removed by filtering to obtain a reaction solution;

[0062] S4, cooling the reaction solution to 0°C for crystallization, and obtaining a solid product after centrifugation. The solid product is washed and then dried at 50°C for 40 min to obtain p-toluenesulfonic acid solid.

[0063] Example 4

[0064] A method for preparing p-toluenesulfonic acid, the specific steps are as follows:

[0065] S1, preparing a silica carrier, this step is the same as Example 2;

[0066] S2. Preparation of silicotungstic acid@silicon dioxide

[0067] 4.4 g of silicotungstic acid was dissolved in 92.0 g of water to obtain a silicotungstic acid aqueous solution; 10.0 g of the silica carrier was immersed in the silicotungstic acid aqueous solution, stirred at 45° C. for 5 h, washed with deionized water after centrifugation, and dried at 120° C. for 5 h to obtain silica loaded with heteropoly acid, i.e., silicotungstic acid@silica;

[0068] S3, sulfonation reaction to prepare p-toluenesulfonic acid

[0069] Toluene and 1,2-dichloroethane are mixed to obtain a toluene organic solution with a mass concentration of 40%; sulfur trioxide is introduced into 1,2-dichloroethane to obtain a sulfur trioxide organic solution with a mass concentration of 20%;

[0070] Add 6.0 g of the silicotungstic acid@silicon dioxide to 300 g of the toluene organic solution, then dropwise add 434.8 g of the sulfur trioxide organic solution at a temperature of 25° C. After the dropwise addition is complete, continue stirring and reacting for 50 minutes;

[0071] After the reaction is completed, the silicotungstic acid@silicon dioxide is removed by filtering to obtain a reaction solution;

[0072] S4, cooling the reaction solution to 0°C for crystallization, and obtaining a solid product after centrifugation. The solid product is washed and then dried at 50°C for 40 min to obtain p-toluenesulfonic acid solid.

[0073] Comparative Example 1

[0074] A method for preparing p-toluenesulfonic acid, the specific steps are as follows:

[0075] S1. Preparation of p-toluenesulfonic acid by sulfonation reaction

[0076] Toluene and 1,2-dichloroethane are mixed to obtain a toluene organic solution with a mass concentration of 40%; sulfur trioxide is introduced into 1,2-dichloroethane to obtain a sulfur trioxide organic solution with a mass concentration of 20%;

[0077] At a temperature of 25° C., 434.8 g of the sulfur trioxide organic solution was added dropwise to 300 g of the toluene organic solution. After the addition was complete, the mixture was stirred and reacted for 50 min. After the reaction was completed, a reaction solution was obtained.

[0078] S2, cooling the reaction solution to 0°C for crystallization, and obtaining a solid product after centrifugation. The solid product is washed and then dried at 50°C for 40 min to obtain p-toluenesulfonic acid solid.

[0079] Comparative Example 2

[0080] A method for preparing p-toluenesulfonic acid, the specific steps are as follows:

[0081] S1 and S2 are the same as in Example 4;

[0082] S3, sulfonation reaction to prepare p-toluenesulfonic acid

[0083] Toluene and 1,2-dichloroethane were mixed to obtain 300g of a 40% toluene organic solution. 6.0g of the silicotungstic acid@silicon dioxide was added thereto, and then 86.9g of sulfur trioxide was added dropwise at a temperature of 25°C. After the addition was completed, the mixture was stirred and reacted for 50 minutes to obtain a reaction solution.

[0084] S4, cooling the reaction solution to 0°C for crystallization, and obtaining a solid product after centrifugation. The solid product is washed and then dried at 50°C for 40 min to obtain p-toluenesulfonic acid solid.

[0085] The p-toluenesulfonic acid solids prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were tested, as shown in Table 1.

[0086] Table 1

[0087]

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing p-toluenesulfonic acid, characterized in that: By adding heteropolyacid@silicon dioxide and dropping sulfur trioxide organic solvent, the content of toluene sulfone byproduct and p-toluenesulfonic acid isomers in p-toluenesulfonic acid is reduced; The specific preparation method is as follows: S1. Preparation of silica carrier The nano-silicon dioxide powder is immersed in dilute hydrochloric acid for 9 hours to 11 hours, filtered and washed, and then calcined at 300° C. to 400° C. for 1 to 3 hours to obtain a silicon dioxide carrier with a pore size of 300 nm to 450 nm; S2. Preparation of heteropolyacid@silicon dioxide Dissolve the heteroacid in water to obtain a heteroacid aqueous solution with a mass concentration of 3% to 5%; soak the silica carrier in the heteroacid aqueous solution, wherein the solid-liquid ratio is 0.08 to 0.12 g / mL, stir at 40° C. to 45° C. for 2 h to 8 h, centrifuge, wash and dry to obtain heteropolyacid-loaded silica, i.e., heteropolyacid@silica; the heteroacid is one of tungstophosphoric acid, molybdophosphoric acid and silicotungstic acid; S3, sulfonation reaction to prepare p-toluenesulfonic acid The organic solvent and toluene are mixed to obtain a toluene organic solvent; the organic solvent is introduced into sulfur trioxide to obtain a sulfur trioxide organic solvent; the heteropolyacid@silicon dioxide is added to the toluene organic solution, and then the sulfur trioxide organic solution is added dropwise, and the reaction is continued with stirring for 30 minutes to 70 minutes after the addition is completed, wherein the molar ratio of toluene to sulfur trioxide is 1.3:1 to 1.1:1; after the reaction is completed, the heteropolyacid@silicon dioxide is filtered out to obtain a reaction solution; the organic solvent is one of dichloromethane, 1,2-dichloroethane, chloroform or carbon tetrachloride; the mass ratio of the heteropolyacid@silicon dioxide to toluene is 0.03:1 to 0.08:1; the reaction temperature is 20°C to 30°C; S4, cooling the reaction solution to 0-5°C for crystallization, obtaining a solid product after centrifugation, and washing and drying the solid product to obtain p-toluenesulfonic acid solid.

2. The method for preparing p-toluenesulfonic acid according to claim 1, characterized in that: The mass concentration of the dilute hydrochloric acid is 10% to 15%.

3. The method for preparing p-toluenesulfonic acid according to claim 1, characterized in that: The drying temperature in step S4 is 45°C to 60°C.

4. The method for preparing p-toluenesulfonic acid according to claim 1, characterized in that: The drying time in step S4 is 20 min to 60 min.

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