A kind of preparation method of high-purity p-toluenesulfonic acid

Abstract

The present invention provides a method for preparing high-purity p-toluenesulfonic acid, which belongs to the field of chemical synthesis; comprising the following steps: preparing catalyst I; preparing a supported catalyst; adding a supported catalyst to prepare catalyst II; preparing p-toluenesulfonic acid. The present invention first reacts tetraethyl silicate, tetraethyl titanate, anhydrous ethanol, nitric acid solution and deionized water, then adds (3-mercaptopropyl) trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate to continue the reaction to prepare a gel, then heat treats, grinds and sieves the gel to obtain catalyst I, and when the catalyst I is used to catalyze the reaction of synthesizing p-toluenesulfonic acid from toluene and sulfur trioxide, it can not only effectively improve the conversion rate of toluene, thereby achieving the effect of increasing the output of p-toluenesulfonic acid, but also improve the selectivity of p-toluenesulfonic acid, reduce the generation of by-products such as isomers at the meta and ortho positions, so as to improve the purity of the obtained p-toluenesulfonic acid.

Description

Technical Field

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

[0002] p-Toluenesulfonic acid is an important organic compound. Due to its strong acidity, it is widely used in organic synthesis, medicine, dyes, pesticides and other fields. It can be used as a catalyst in various chemical reactions, such as esterification, acetalization, dehydration, alkylation, Beckmann rearrangement, polymerization and depolymerization. In these reactions, it has better effects than sulfuric acid because it does not cause side reactions such as oxidation and carbon formation, and the obtained products are of high purity and light color. In addition, it can also be used as an additive in phenolic, epoxy, amino plastics, furniture varnish, dyes and adhesives.

[0003] At present, the preparation method of p-toluenesulfonic acid is mainly toluene sulfonation method, and the main sulfonation reagents include concentrated sulfuric acid, chlorosulfonic acid and sulfur trioxide. When concentrated sulfuric acid is used as a sulfonation reagent, although the concentration and temperature uniformity of the reaction solution can be maintained, the selectivity of the reaction is improved, but the reaction is a reversible reaction, and 1 mol of water will be produced for every 1 mol of sulfuric acid consumed. The generation of water causes the sulfuric acid concentration to decrease. When the sulfuric acid concentration is too low, the sulfonation rate is extremely small, the toluene conversion rate is low, and a large amount of toluene is not converted, so the method has no practical value; when chlorosulfonic acid is used as a sulfonation reagent, due to the high price of chlorosulfonic acid, it is easy to increase production costs. When sulfur trioxide is used as a sulfonation reagent to synthesize p-toluenesulfonic acid, it will be accompanied by the generation of by-products such as meta- and ortho-isomers, and such isomers are difficult to be separated and refined, resulting in a low purity of p-toluenesulfonic acid.

[0004] Therefore, it is necessary to provide a method for preparing high-purity p-toluenesulfonic acid to improve the purity of the product. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing high-purity p-toluenesulfonic acid.

[0006] A method for preparing high-purity p-toluenesulfonic acid comprises the following steps:

[0007] S1: Preparation of Catalyst I

[0008] Tetraethyl silicate and tetraethyl titanate are stirred and mixed uniformly, and anhydrous ethanol, nitric acid and deionized water are added, and after heating for reaction, (3-mercaptopropyl) trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate are added, and the reaction is continued by stirring and standing to prepare a gel, and after drying, heat treatment, grinding and sieving, a catalyst I is obtained;

[0009] S2: Preparation of supported catalyst

[0010] Dissolving tannic acid and zirconium tetrachloride in deionized water respectively to prepare tannic acid solution and zirconium tetrachloride solution, then adding the zirconium tetrachloride solution into the tannic acid solution for reflux reaction to obtain a supported catalyst;

[0011] S3: Adding carrier catalyst to prepare catalyst II

[0012] Dissolve triethylenediamine in ethyl acetate, add the above-mentioned carrier catalyst, and after uniform dispersion, add 1,3-propane sultone to react to prepare an intermediate, then uniformly disperse the intermediate in deionized water, add hydrochloric acid to reflux reaction, and obtain catalyst II through rotary evaporation and ultrasonic treatment;

[0013] S4: Preparation of p-toluenesulfonic acid

[0014] Dissolve toluene in an organic solvent at a volume ratio of 1:(20-30), add the above catalyst I and the above catalyst II, then add liquid sulfur trioxide, stir and react for 1-2 hours, filter to remove catalyst I and catalyst II, cool and crystallize, centrifuge, wash and dry to obtain p-toluenesulfonic acid;

[0015] Wherein, the molar ratio of toluene to liquid sulfur trioxide is (1.2-1.4):1;

[0016] The organic solvent is one of dichloromethane, chloroform or carbon tetrachloride.

[0017] Furthermore, the preparation of catalyst I in step S1 specifically comprises the following steps:

[0018] S1.1: Tetraethyl titanate and tetraethyl silicate are stirred and mixed evenly in a molar ratio of 1: (50-60), and then placed in a 0°C ice water bath, and then anhydrous ethanol, nitric acid solution and deionized water are added, and stirred for reaction for 1-2 hours to obtain a mixed solution;

[0019] S1.2: The mixed solution is heated at 70-80°C for 1-2h, then raised to 80-90°C, and kept stirring and refluxed for 8-10h, then (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate are added, and the stirring and reflux are continued for 3-5h, and then allowed to stand for 10-12h to obtain a gel;

[0020] S1.3: Place the above gel in a drying oven, heat it at 110-120°C for 3-4h, grind and sieve to obtain catalyst I.

[0021] Furthermore, the preparation of the supported catalyst in step S2 specifically comprises the following steps:

[0022] S2.1: Add tannic acid into deionized water at a solid-liquid ratio of 1 g: (30-40) mL, stir thoroughly to dissolve, and obtain a tannic acid solution;

[0023] S2.2: Add zirconium tetrachloride into deionized water at a solid-liquid ratio of 1 g: (15-25) mL, stir thoroughly to dissolve, and obtain a zirconium tetrachloride solution;

[0024] S2.3: Heat the tannic acid solution to 70-80°C, add the zirconium tetrachloride solution, and reflux for 8-10 hours under the protection of nitrogen. After filtering, washing and drying, grind and sieve to obtain a supported catalyst.

[0025] Furthermore, the step S3 of adding a carrier catalyst to prepare catalyst II specifically comprises the following steps:

[0026] S3.1: Add triethylenediamine to ethyl acetate at a solid-liquid ratio of 1 g: (8-10) mL, stir and mix evenly, then add the supported catalyst prepared in step S2.3, stir and disperse thoroughly, and obtain a supported dispersion;

[0027] S3.2: adding 1,3-propane sultone to the carrier dispersion while stirring, and reacting for 46-50 hours under the protection of nitrogen, filtering, washing, rotary evaporation and drying to obtain an intermediate;

[0028] S3.3: Add the above intermediate into distilled water at a solid-liquid ratio of 1 g: (0.4-0.8) mL, stir and disperse thoroughly, then add hydrochloric acid while stirring, and then heat and reflux at 70-80°C for 8-9 hours under the protection of nitrogen to obtain a mixed reaction liquid;

[0029] S3.4: The mixed reaction liquid is subjected to rotary evaporation to remove excess water, and then subjected to ultrasonic treatment for 20-30 minutes. After filtration, washing and vacuum drying, catalyst II is obtained.

[0030] Furthermore, the volume ratio of anhydrous ethanol, nitric acid solution and deionized water is 1:(12-14):(20-30), the concentration of nitric acid solution is 0.1 mol / L, and the mass ratio of tetraethyl silicate to anhydrous ethanol is (2.4-2.6):1.

[0031] Furthermore, the mass ratio of (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate to tetraethyl silicate is (0.02-0.03):(1.6-1.8):(0.06-0.08):1.

[0032] Furthermore, the volume ratio of the tannic acid solution to the zirconium tetrachloride solution is (4-5):1.

[0033] Furthermore, the solid-liquid ratio of the supported catalyst to ethyl acetate is 1 g: (12-16) mL, and the mass ratio of 1,3-propane sultone to triethylenediamine is (2-3):1.

[0034] Furthermore, the solid-liquid ratio of the intermediate to hydrochloric acid is 1 g: (28-36) mL, and the concentration of hydrochloric acid is 0.2 mol / L.

[0035] Furthermore, the mass ratio of catalyst I to catalyst II is 1:(2.6-3), and the mass ratio of the total amount of catalyst I and catalyst II to toluene is 1:(23-25).

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] 1. The present invention comprises the following steps: firstly, tetraethyl silicate, tetraethyl titanate, anhydrous ethanol, nitric acid solution and deionized water are mixed for reaction, and then (3-mercaptopropyl) trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate are added for further reaction to prepare a gel, and then the gel is heat-treated, ground and sieved to obtain a catalyst I. When the catalyst I is used to catalyze the reaction of synthesizing p-toluenesulfonic acid from toluene and sulfur trioxide, not only the conversion rate of toluene can be effectively improved, thereby achieving the effect of increasing the yield of p-toluenesulfonic acid, but also the selectivity of p-toluenesulfonic acid can be improved, and the generation of by-products such as meta-isomers and ortho-isomers can be reduced, so as to improve the purity of the obtained p-toluenesulfonic acid.

[0038] 2. The present invention dissolves triethylenediamine in ethyl acetate, then uniformly disperses the prepared supported catalyst therein, then adds 1,3-propane sultone to react and prepare an intermediate, then uniformly disperses the intermediate in deionized water, and adds hydrochloric acid to react to form a composite material with catalytic effect to prepare catalyst II. When catalyst II is added to catalyst I to catalyze the reaction of synthesizing p-toluenesulfonic acid from toluene and sulfur trioxide, the selectivity of p-toluenesulfonic acid can be further improved, thereby improving the purity of the prepared p-toluenesulfonic acid.

[0039] 3. The present invention prepares a supported catalyst by first dissolving tannic acid and zirconium tetrachloride in deionized water to prepare a tannic acid solution and a zirconium tetrachloride solution, then heating the tannic acid solution and adding the zirconium tetrachloride solution to carry out a reflux reaction. Since multiple phenolic hydroxyl groups in tannic acid can form a stable complex with zirconium ions in zirconium tetrachloride, the complex has multiple acidic centers and can provide protons to promote the reaction of toluene and sulfur trioxide. Therefore, the supported catalyst can effectively catalyze the reaction of toluene and sulfur trioxide to synthesize p-toluenesulfonic acid. In addition, since the supported catalyst can produce a synergistic promoting effect with catalyst I, the catalyst II formed by the supported catalyst can synergistically improve the conversion rate of toluene with catalyst I, thereby increasing the yield of p-toluenesulfonic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable those skilled in the relevant art to make and use the present disclosure.

[0041] Figure 1 The present invention is a flow chart of the method for preparing high-purity p-toluenesulfonic acid used in the embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following is a detailed description of a method for preparing high-purity p-toluenesulfonic acid provided by the present invention in conjunction with the accompanying drawings and specific examples.

[0043] Example 1

[0044] A method for preparing high-purity p-toluenesulfonic acid, such as Figure 1 As shown, the following steps are included:

[0045] S1: Preparation of Catalyst I

[0046] S1.1: Tetraethyl titanate and tetraethyl silicate are stirred and mixed uniformly at a molar ratio of 1:50, and then placed in a 0°C ice water bath, and then anhydrous ethanol, nitric acid solution and deionized water are added, and stirred for reaction for 1 hour to obtain a mixed solution, wherein the volume ratio of anhydrous ethanol, nitric acid solution and deionized water is 1:12:20, the concentration of nitric acid solution is 0.1 mol / L, and the mass ratio of tetraethyl silicate to anhydrous ethanol is 2.4:1;

[0047] S1.2: The mixed solution was heated at 70°C for 1 hour, then raised to 80°C, and kept stirring and refluxed for 8 hours, then (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate were added, and the mixture was stirred and refluxed for 3 hours, and then allowed to stand for 10 hours to obtain a gel, wherein the mass ratio of (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate to tetraethyl silicate was 0.02:1.6:0.06:1;

[0048] S1.3: The gel was placed in a drying oven and heated at 110°C for 3 h. After grinding and sieving, catalyst I was obtained.

[0049] S2: Preparation of supported catalyst

[0050] S2.1: Add tannic acid into deionized water at a solid-liquid ratio of 1 g:30 mL, stir thoroughly to dissolve, and obtain a tannic acid solution;

[0051] S2.2: Add zirconium tetrachloride into deionized water at a solid-liquid ratio of 1 g:15 mL, stir thoroughly to dissolve, and obtain a zirconium tetrachloride solution;

[0052] S2.3: heating the tannic acid solution to 70°C, adding the zirconium tetrachloride solution, and keeping the temperature under reflux for 8 hours under the protection of nitrogen. After filtering, washing and drying, grinding and sieving to obtain a supported catalyst, wherein the volume ratio of the tannic acid solution to the zirconium tetrachloride solution is 4:1;

[0053] S3: Adding carrier catalyst to prepare catalyst II

[0054] S3.1: Add triethylenediamine to ethyl acetate at a solid-liquid ratio of 1g:8mL, stir and mix evenly, then add the supported catalyst prepared in step S2.3, stir and disperse thoroughly to obtain a supported dispersion, wherein the solid-liquid ratio of the supported catalyst to ethyl acetate is 1g:12mL;

[0055] S3.2: adding 1,3-propane sultone to the carrier dispersion while stirring, and reacting for 46 hours under the protection of nitrogen, filtering, washing, rotary evaporation and drying to obtain an intermediate, wherein the mass ratio of 1,3-propane sultone to triethylenediamine is 2:1;

[0056] S3.3: Add the intermediate to distilled water at a solid-liquid ratio of 1g:0.4mL, stir and disperse thoroughly, then add hydrochloric acid while stirring, and then heat and reflux at 70°C under nitrogen protection for 8h to obtain a mixed reaction liquid, wherein the solid-liquid ratio of the intermediate to hydrochloric acid is 1g:28mL, and the concentration of hydrochloric acid is 0.2mol / L;

[0057] S3.4: The mixed reaction liquid is subjected to rotary evaporation to remove excess water, and then subjected to ultrasonic treatment for 20 minutes. After filtering, washing and vacuum drying, catalyst II is obtained;

[0058] S4: Preparation of p-toluenesulfonic acid

[0059] Toluene is dissolved in an organic solvent at a volume ratio of 1:20, and the above-mentioned catalyst I and catalyst II are added, and then liquid sulfur trioxide is added, and the reaction is stirred for 1 hour, and after filtering to remove catalyst I and catalyst II, the temperature is lowered for crystallization, centrifugal filtration, washing and drying are performed to obtain p-toluenesulfonic acid;

[0060] Wherein, the molar ratio of toluene to liquid sulfur trioxide is 1.2:1;

[0061] The mass ratio of catalyst I to catalyst II is 1:2.6, and the mass ratio of the total amount of catalyst I and catalyst II to toluene is 1:23;

[0062] The organic solvent is one of dichloromethane, chloroform or carbon tetrachloride.

[0063] Product analysis:

[0064] The prepared p-toluenesulfonic acid was analyzed by liquid chromatography, and the conversion rate of toluene and the selectivity of p-toluenesulfonic acid were calculated. The results are shown in Table 1.

[0065] Example 2

[0066] A method for preparing high-purity p-toluenesulfonic acid, such as Figure 1 As shown, the following steps are included:

[0067] S1: Preparation of Catalyst I

[0068] S1.1: Tetraethyl titanate and tetraethyl silicate were stirred and mixed uniformly at a molar ratio of 1:55, and then placed in a 0°C ice water bath, and then anhydrous ethanol, nitric acid solution and deionized water were added, and stirred for reaction for 1.5 hours to obtain a mixed solution, wherein the volume ratio of anhydrous ethanol, nitric acid solution and deionized water was 1:13:25, the concentration of nitric acid solution was 0.1 mol / L, and the mass ratio of tetraethyl silicate to anhydrous ethanol was 2.5:1;

[0069] S1.2: The mixed solution was heated at 75°C for 1.5h, then raised to 85°C, and kept stirring and refluxed for 9h, then (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate were added, and the mixture was stirred and refluxed for 4h, and then allowed to stand for 11h to obtain a gel, wherein the mass ratio of (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate to tetraethyl silicate was 0.025:1.7:0.07:1;

[0070] S1.3: The gel was placed in a drying oven and heated at 115°C for 3.5 hours. After grinding and sieving, catalyst I was obtained.

[0071] S2: Preparation of supported catalyst

[0072] S2.1: Add tannic acid into deionized water at a solid-liquid ratio of 1 g:35 mL, stir thoroughly to dissolve, and obtain a tannic acid solution;

[0073] S2.2: Add zirconium tetrachloride into deionized water at a solid-liquid ratio of 1 g:20 mL, stir thoroughly to dissolve, and obtain a zirconium tetrachloride solution;

[0074] S2.3: heating the tannic acid solution to 75°C, adding the zirconium tetrachloride solution, and keeping the temperature under reflux for 9 hours under the protection of nitrogen. After filtering, washing and drying, grinding and sieving to obtain a supported catalyst, wherein the volume ratio of the tannic acid solution to the zirconium tetrachloride solution is 4.5:1;

[0075] S3: Adding carrier catalyst to prepare catalyst II

[0076] S3.1: Add triethylenediamine to ethyl acetate at a solid-liquid ratio of 1g:9mL, stir and mix evenly, then add the supported catalyst prepared in step S2.3, stir and disperse thoroughly to obtain a supported dispersion, wherein the solid-liquid ratio of the supported catalyst to ethyl acetate is 1g:14mL;

[0077] S3.2: adding 1,3-propane sultone to the carrier dispersion while stirring, and reacting for 48 hours under the protection of nitrogen, filtering, washing, rotary evaporation and drying to obtain an intermediate, wherein the mass ratio of 1,3-propane sultone to triethylenediamine is 2.5:1;

[0078] S3.3: Add the intermediate to distilled water at a solid-liquid ratio of 1g:0.6mL, stir and disperse thoroughly, then add hydrochloric acid while stirring, and then heat and reflux at 75°C under nitrogen protection for 8.5h to obtain a mixed reaction liquid, wherein the solid-liquid ratio of the intermediate to hydrochloric acid is 1g:32mL, and the concentration of hydrochloric acid is 0.2mol / L;

[0079] S3.4: The mixed reaction liquid is subjected to rotary evaporation to remove excess water, and then subjected to ultrasonic treatment for 25 minutes. After filtering, washing and vacuum drying, catalyst II is obtained;

[0080] S4: Preparation of p-toluenesulfonic acid

[0081] Toluene is dissolved in an organic solvent at a volume ratio of 1:25, and the above-mentioned catalyst I and catalyst II are added, and then liquid sulfur trioxide is added, and the reaction is stirred for 1.5 hours, and after filtering to remove catalyst I and catalyst II, the temperature is lowered for crystallization, centrifugal filtration, washing and drying are performed to obtain p-toluenesulfonic acid;

[0082] Wherein, the molar ratio of toluene to liquid sulfur trioxide is 1.3:1;

[0083] The mass ratio of catalyst I to catalyst II is 1:2.8, and the mass ratio of the total amount of catalyst I and catalyst II to toluene is 1:24;

[0084] The organic solvent is one of dichloromethane, chloroform or carbon tetrachloride.

[0085] Product analysis:

[0086] The prepared p-toluenesulfonic acid was analyzed by liquid chromatography, and the conversion rate of toluene and the selectivity of p-toluenesulfonic acid were calculated. The results are shown in Table 1.

[0087] Example 3

[0088] A method for preparing high-purity p-toluenesulfonic acid, such as Figure 1 As shown, the following steps are included:

[0089] S1: Preparation of Catalyst I

[0090] S1.1: Tetraethyl titanate and tetraethyl silicate are stirred and mixed uniformly at a molar ratio of 1:60, and then placed in a 0°C ice water bath, and then anhydrous ethanol, nitric acid solution and deionized water are added, and stirred for reaction for 2 hours to obtain a mixed solution, wherein the volume ratio of anhydrous ethanol, nitric acid solution and deionized water is 1:14:30, the concentration of nitric acid solution is 0.1 mol / L, and the mass ratio of tetraethyl silicate to anhydrous ethanol is 2.6:1;

[0091] S1.2: The mixed solution was heated at 80°C for 2h, then raised to 90°C, and kept stirring and refluxed for 10h, then (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate were added, and the mixture was stirred and refluxed for 5h, and then allowed to stand for 12h to obtain a gel, wherein the mass ratio of (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate to tetraethyl silicate was 0.03:1.8:0.08:1;

[0092] S1.3: The gel was placed in a drying oven and heated at 120°C for 4 h. After grinding and sieving, catalyst I was obtained.

[0093] S2: Preparation of supported catalyst

[0094] S2.1: Add tannic acid into deionized water at a solid-liquid ratio of 1 g:40 mL, stir thoroughly to dissolve, and obtain a tannic acid solution;

[0095] S2.2: Add zirconium tetrachloride into deionized water at a solid-liquid ratio of 1 g:25 mL, stir thoroughly to dissolve, and obtain a zirconium tetrachloride solution;

[0096] S2.3: heating the tannic acid solution to 80°C, adding the zirconium tetrachloride solution, and keeping the temperature under reflux for 10 hours under the protection of nitrogen. After filtering, washing and drying, grinding and sieving to obtain a supported catalyst, wherein the volume ratio of the tannic acid solution to the zirconium tetrachloride solution is 5:1;

[0097] S3: Adding carrier catalyst to prepare catalyst II

[0098] S3.1: Add triethylenediamine to ethyl acetate at a solid-liquid ratio of 1g:10mL, stir and mix evenly, then add the supported catalyst prepared in step S2.3, stir and disperse thoroughly to obtain a supported dispersion, wherein the solid-liquid ratio of the supported catalyst to ethyl acetate is 1g:16mL;

[0099] S3.2: adding 1,3-propane sultone to the carrier dispersion while stirring, and reacting for 50 hours under the protection of nitrogen, filtering, washing, rotary evaporation and drying to obtain an intermediate, wherein the mass ratio of 1,3-propane sultone to triethylenediamine is 3:1;

[0100] S3.3: Add the intermediate to distilled water at a solid-liquid ratio of 1g:0.8mL, stir and disperse thoroughly, then add hydrochloric acid while stirring, and then heat and reflux at 80°C under nitrogen protection for 9h to obtain a mixed reaction liquid, wherein the solid-liquid ratio of the intermediate to hydrochloric acid is 1g:36mL, and the concentration of hydrochloric acid is 0.2mol / L;

[0101] S3.4: The mixed reaction liquid is subjected to rotary evaporation to remove excess water, and then subjected to ultrasonic treatment for 30 minutes. After filtering, washing and vacuum drying, catalyst II is obtained;

[0102] S4: Preparation of p-toluenesulfonic acid

[0103] Dissolve toluene in an organic solvent at a volume ratio of 1:30, add the above-mentioned catalyst I and catalyst II, then add liquid sulfur trioxide, stir and react for 2 hours, filter to remove catalyst I and catalyst II, cool and crystallize, centrifuge, wash and dry to obtain p-toluenesulfonic acid;

[0104] Wherein, the molar ratio of toluene to liquid sulfur trioxide is 1.4:1;

[0105] The mass ratio of catalyst I to catalyst II is 1:3, and the mass ratio of the total amount of catalyst I and catalyst II to toluene is 1:25;

[0106] The organic solvent is one of dichloromethane, chloroform or carbon tetrachloride.

[0107] Product analysis:

[0108] The prepared p-toluenesulfonic acid was analyzed by liquid chromatography, and the conversion rate of toluene and the selectivity of p-toluenesulfonic acid were calculated. The results are shown in Table 1.

[0109] Table 1: Summary of product analysis results of Example 1, Example 2, and Example 3

[0110]

[0111] Comparative Example 1

[0112] The preparation method of p-toluenesulfonic acid in this comparative example is as follows:

[0113] Dissolve toluene in an organic solvent at a volume ratio of 1:(20-30), then add liquid sulfur trioxide, stir and react for 1-2 hours, cool and crystallize, centrifuge, filter, wash and dry to obtain p-toluenesulfonic acid;

[0114] Wherein, the molar ratio of toluene to liquid sulfur trioxide is (1.2-1.4):1;

[0115] The organic solvent is one of dichloromethane, chloroform or carbon tetrachloride.

[0116] Product analysis:

[0117] The obtained p-toluenesulfonic acid was analyzed by liquid chromatography, and the conversion rate of toluene and the selectivity of p-toluenesulfonic acid were calculated. The results are shown in Table 2.

[0118] Table 2: Comparison of product analysis results of Example 1, Example 2, Example 3 and Comparative Example 1

[0119]

[0120] Comparative Example 2

[0121] The difference between this comparative example 2 and example 1 is that step S1 is removed, and catalyst I in step S4 is removed, and then the conversion rate of toluene and the selectivity of p-toluenesulfonic acid in comparative example 2 are calculated according to the product analysis calculation method in example 1, and the results are shown in Table 3.

[0122] Table 3: Comparison of product analysis results of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2

[0123]

[0124] It can be seen from Table 1, Table 2 and Table 3 that in Comparative Example 1, when toluene and sulfur trioxide are used to synthesize p-toluenesulfonic acid without adding a catalyst, the conversion rate of toluene and the selectivity of p-toluenesulfonic acid are 66.5% and 74.3%, respectively, which are lower than the conversion rate of toluene and the selectivity of p-toluenesulfonic acid in Examples 1, 2 and 3. In Comparative Example 2, after removing Catalyst I and only using Catalyst II to catalyze the synthesis of p-toluenesulfonic acid from toluene and sulfur trioxide, the conversion rate of toluene and the selectivity of p-toluenesulfonic acid are 93.7% and 92.4%, respectively, which are also lower than the conversion rate of toluene and the selectivity of p-toluenesulfonic acid in Examples 1, 2 and 3. It can be seen that tetraethyl silicate, tetraethyl titanate, anhydrous ethanol, nitric acid solution and deionized water are first mixed for reaction, and then (3-mercaptopropyl) trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate are added for further reaction to prepare a gel, and then the gel is heat-treated, ground and sieved to obtain catalyst I. When the catalyst I is used to catalyze the reaction of synthesizing p-toluenesulfonic acid from toluene and sulfur trioxide, not only can the conversion rate of toluene be effectively improved, thereby achieving the effect of increasing the output of p-toluenesulfonic acid, but also the selectivity of p-toluenesulfonic acid can be improved, and the generation of by-products such as meta- and ortho-isomers can be reduced, so as to improve the purity of the obtained p-toluenesulfonic acid.

[0125] Comparative Example 3

[0126] The difference between this comparative example 3 and example 1 is that step S3 is removed and catalyst II in step S4 is replaced with an equal amount of supported catalyst. Then, the conversion rate of toluene and the selectivity of p-toluenesulfonic acid in comparative example 3 are calculated according to the product analysis calculation method in example 1. The results are shown in Table 4.

[0127] Table 4: Comparison of product analysis results of Example 1, Example 2, Example 3 and Comparative Example 3

[0128]

[0129] Comparative Example 4

[0130] The difference between this comparative example 4 and example 1 is that steps S1 and S3 are removed, and catalyst I and catalyst II in step S4 are replaced with equal amounts of supported catalysts. Then, the conversion rate of toluene and the selectivity of p-toluenesulfonic acid in comparative example 3 are calculated according to the product analysis calculation method in example 1. The results are shown in Table 5.

[0131] Table 5: Comparison of product analysis results of Example 1, Example 2, Example 3 and Comparative Example 3, Comparative Example 4

[0132]

[0133] Comparative Example 5

[0134] The difference between this comparative example 5 and example 1 is that steps S2 and S3 are removed, and catalyst II in step S4 is replaced by an equal amount of catalyst I. Then, the conversion rate of toluene and the selectivity of p-toluenesulfonic acid in comparative example 3 are calculated according to the product analysis calculation method in example 1, and the results are shown in Table 6.

[0135] Table 6: Comparison of product analysis results of Example 1, Example 2, Example 3 and Comparative Examples 3-5

[0136]

[0137] As can be seen from Table 5 and Table 6, in Comparative Examples 4 and 5, when a single supported catalyst and a single catalyst I are used to catalyze the synthesis of p-toluenesulfonic acid from toluene and sulfur trioxide, the conversion rate of toluene and the selectivity of p-toluenesulfonic acid are both lower than those in Comparative Example 3 when catalyst I and a supported catalyst are used to jointly catalyze the synthesis of p-toluenesulfonic acid from toluene and sulfur trioxide. It can be seen that by first dissolving tannic acid and zirconium tetrachloride in deionized water to prepare a tannic acid solution and a zirconium tetrachloride solution, then heating the tannic acid solution, and adding the zirconium tetrachloride solution for reflux reaction to prepare a supported catalyst, since multiple phenolic hydroxyl groups in tannic acid can form a stable complex with zirconium ions in zirconium tetrachloride, this complex has multiple acidic centers, which can provide protons to promote the reaction of toluene and sulfur trioxide, so the supported catalyst can effectively catalyze the reaction of toluene and sulfur trioxide to synthesize p-toluenesulfonic acid. In addition, since the supported catalyst can produce a synergistic promoting effect with catalyst I, the catalyst II formed by the supported catalyst composite can synergistically improve the conversion rate of toluene with catalyst I, thereby improving the yield of p-toluenesulfonic acid.

[0138] In addition, it can be seen from Table 4 that after replacing catalyst II with an equal amount of supported catalyst in Comparative Example 3, when catalyst I and supported catalyst are used to jointly catalyze toluene and sulfur trioxide to synthesize p-toluenesulfonic acid, the conversion rate of toluene and the selectivity of p-toluenesulfonic acid are 97.3% and 93.8%, respectively. Among them, the conversion rate of toluene is not much different from that of Example 1, Example 2 and Example 3, but the selectivity of p-toluenesulfonic acid is significantly lower than that of Example 1, Example 2 and Example 3. It can be seen that by first dissolving triethylenediamine in ethyl acetate, then uniformly dispersing the prepared supported catalyst therein, and then adding 1,3-propane sultone to react to prepare an intermediate, and then uniformly dispersing the intermediate in deionized water, and adding hydrochloric acid to react, a composite material with catalytic effect is formed to obtain catalyst II. When catalyst II is added on the basis of catalyst I to catalyze the reaction of toluene and sulfur trioxide to synthesize p-toluenesulfonic acid, the selectivity of p-toluenesulfonic acid can be further improved, thereby improving the purity of the prepared p-toluenesulfonic acid.

[0139] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing high-purity p-toluenesulfonic acid, characterized in that: The steps include: S1: Preparation of Catalyst I Tetraethyl silicate and tetraethyl titanate are stirred and mixed uniformly, and anhydrous ethanol, nitric acid and deionized water are added, and after heating for reaction, (3-mercaptopropyl) trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate are added, and the reaction is continued by stirring and standing to prepare a gel, and after drying, heat treatment, grinding and sieving, a catalyst I is obtained; S2: Preparation of supported catalyst Dissolving tannic acid and zirconium tetrachloride in deionized water respectively to prepare tannic acid solution and zirconium tetrachloride solution, then adding the zirconium tetrachloride solution into the tannic acid solution for reflux reaction to obtain a supported catalyst; S3: Adding carrier catalyst to prepare catalyst II Dissolve triethylenediamine in ethyl acetate, add the above-mentioned carrier catalyst, and after uniform dispersion, add 1,3-propane sultone to react to prepare an intermediate, then uniformly disperse the intermediate in deionized water, add hydrochloric acid to reflux reaction, and obtain catalyst II through rotary evaporation and ultrasonic treatment; S4: Preparation of p-toluenesulfonic acid Dissolve toluene in an organic solvent at a volume ratio of 1:(20-30), add the above catalyst I and the above catalyst II, then add liquid sulfur trioxide, stir and react for 1-2 hours, filter to remove catalyst I and catalyst II, cool and crystallize, centrifuge, wash and dry to obtain p-toluenesulfonic acid; Wherein, the molar ratio of toluene to liquid sulfur trioxide is (1.2-1.4):1; The organic solvent is one of dichloromethane, chloroform or carbon tetrachloride; The preparation of catalyst I in step S1 specifically comprises the following steps: S1.1: Tetraethyl titanate and tetraethyl silicate are stirred and mixed evenly in a molar ratio of 1: (50-60), and then placed in a 0°C ice water bath, and then anhydrous ethanol, nitric acid solution and deionized water are added, and stirred for reaction for 1-2 hours to obtain a mixed solution; S1.2: The mixed solution is heated at 70-80°C for 1-2h, then raised to 80-90°C, and kept stirring and refluxed for 8-10h, then (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate are added, and the stirring and reflux are continued for 3-5h, and then allowed to stand for 10-12h to obtain a gel; S1.3: The gel is placed in a drying oven and heated at 110-120°C for 3-4 hours. After grinding and sieving, catalyst I is obtained. The preparation of the supported catalyst in step S2 specifically comprises the following steps: S2.1: Add tannic acid into deionized water at a solid-liquid ratio of 1 g: (30-40) mL, stir thoroughly to dissolve, and obtain a tannic acid solution; S2.2: Add zirconium tetrachloride into deionized water at a solid-liquid ratio of 1 g: (15-25) mL, stir thoroughly to dissolve, and obtain a zirconium tetrachloride solution; S2.3: heating the tannic acid solution to 70-80°C, adding the zirconium tetrachloride solution, and keeping the temperature under reflux for 8-10 hours under the protection of nitrogen. After filtering, washing and drying, grinding and sieving, a supported catalyst is obtained. Step S3 of adding a carrier catalyst to prepare catalyst II specifically comprises the following steps: S3.1: Add triethylenediamine to ethyl acetate at a solid-liquid ratio of 1 g: (8-10) mL, stir and mix evenly, then add the supported catalyst prepared in step S2.3, stir and disperse thoroughly, and obtain a supported dispersion; S3.2: adding 1,3-propane sultone to the carrier dispersion while stirring, and reacting for 46-50 hours under the protection of nitrogen, filtering, washing, rotary evaporation and drying to obtain an intermediate; S3.3: Add the above intermediate into distilled water at a solid-liquid ratio of 1 g: (0.4-0.8) mL, stir and disperse thoroughly, then add hydrochloric acid while stirring, and then heat and reflux at 70-80°C for 8-9 hours under the protection of nitrogen to obtain a mixed reaction liquid; S3.4: The mixed reaction liquid is subjected to rotary evaporation to remove excess water, and then subjected to ultrasonic treatment for 20-30 minutes. After filtration, washing and vacuum drying, catalyst II is obtained.

2. The method for preparing high-purity p-toluenesulfonic acid according to claim 1, characterized in that: The volume ratio of anhydrous ethanol, nitric acid solution and deionized water is 1:(12-14):(20-30), the concentration of nitric acid solution is 0.1 mol / L, and the mass ratio of tetraethyl silicate to anhydrous ethanol is (2.4-2.6):

1.

3. The method for preparing high-purity p-toluenesulfonic acid according to claim 1, characterized in that: The mass ratio of (3-mercaptopropyl)trimethoxysilane, phosphotungstic acid and lanthanum nitrate hexahydrate to tetraethyl silicate is (0.02-0.03):(1.6-1.8):(0.06-0.08):

1.

4. The method for preparing high-purity p-toluenesulfonic acid according to claim 1, characterized in that: The volume ratio of tannic acid solution to zirconium tetrachloride solution is (4-5):

1.

5. The method for preparing high-purity p-toluenesulfonic acid according to claim 1, characterized in that: The solid-liquid ratio of the supported catalyst to ethyl acetate is 1 g: (12-16) mL, and the mass ratio of 1,3-propane sultone to triethylenediamine is (2-3):

1.

6. The method for preparing high-purity p-toluenesulfonic acid according to claim 1, characterized in that: The solid-liquid ratio of the intermediate to hydrochloric acid is 1 g: (28-36) mL, and the concentration of hydrochloric acid is 0.2 mol / L.

7. The method for preparing high-purity p-toluenesulfonic acid according to claim 1, characterized in that: The mass ratio of catalyst I to catalyst II is 1:(2.6-3), and the mass ratio of the total amount of catalyst I and catalyst II to toluene is 1:(23-25).

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