Process for the preparation of a catalyst for the synthesis of 1-methylpyridinium chloride

Abstract

The application discloses a preparation method of a catalyst for synthesizing 1-methyl pyridine chloride, belongs to the technical field of catalyst synthesis, and utilizes the silica produced by the hydrolysis of tetraethyl orthosilicate under alkaline conditions to coat polypenyl sulfon, so as to obtain modified silica. The modified silica can further be chemically bonded with gamma-(2,3-epoxypropoxy) propyl trimethoxysilane, 1-aminopropyl-3-methyl imidazole tetrafluoroborate and hexamethylenetetramine, so as to obtain the catalyst for synthesizing 1-methyl pyridine chloride, and the synthesis conversion rate of 1-methyl pyridine chloride is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of catalyst synthesis, in particular to a preparation method of a catalyst for synthesizing 1-methylpyridinium chloride. BACKGROUND

[0002] For the synthesis of 1-methylpyridinium chloride, a Chinese patent with the application number CN115557884A discloses a process for synthesizing 1-methylpyridinium chloride at high temperature, which comprises: under the N2 atmosphere, pyridine is put into an autoclave, the pyridine is preheated to 60-80 DEG C, liquid chloromethane is started to be added dropwise, the chloromethane dropwise adding time is controlled to be 2-3 h, the reaction temperature is controlled to be 110-150 DEG C during the dropwise adding process, after the chloromethane dropwise adding is completed, 110-150 DEG C is kept for 15-30 min, and 1-methylpyridinium chloride is obtained, however, the reaction temperature in the technical solution is high, which is not conducive to energy saving, meanwhile, the boiling points of pyridine and chloromethane are low, and under high temperature, pyridine and chloromethane are easy to volatilize in large amounts, which is not conducive to the improvement of the conversion rate of the product and the recycling of the reaction substrate. SUMMARY

[0003] The application aims to provide a preparation method of a catalyst for synthesizing 1-methylpyridinium chloride, which can improve the conversion rate of 1-methylpyridinium chloride at a lower reaction temperature, so as to solve the problems in the above background technology.

[0004] To achieve the above-mentioned purpose, the application provides the following technical scheme:

[0005] As shown in the formula (I), a catalyst for synthesizing 1-methylpyridinium chloride is prepared by the following steps: Figure 1

[0006] Step S1, modified silicon dioxide and gamma-(2,3-epoxypropoxy) propyl trimethoxysilane are added into anhydrous ethanol, and are uniformly stirred, and then are heated to 40-60 DEG C, and continue to be stirred for 8-10 h, after the reaction is completed, centrifugal washing and 80 DEG C vacuum drying are carried out, and then epoxy-based silicon dioxide is obtained, wherein the amount ratio of the modified silicon dioxide, the gamma-(2,3-epoxypropoxy) propyl trimethoxysilane and the anhydrous ethanol is 4-5 mL:3-4 mL:60-65 mL, in the above preparation process, the hydroxyl group on the modified silicon dioxide and the silane group on the gamma-(2,3-epoxypropoxy) propyl trimethoxysilane are chemically bonded to obtain the epoxy-based silicon dioxide, and the structural formula is as shown in the formula (II). Figure 2

[0007] ​​Step S2, under the protection of nitrogen, the epoxy-based silica prepared in step S2 and 1-aminopropyl-3-methyl imidazole tetrafluoroborate are added into anhydrous DMF, stirred uniformly, heated to 60-70℃, and stirred for 6-8h to obtain a hydroxylated silica solution, wherein the ratio of the amount of epoxy-based silica, 1-aminopropyl-3-methyl imidazole tetrafluoroborate and anhydrous DMF is 0.75-1.25g: 0.5-1mL: 40-50mL, ring-opening reaction occurs between the epoxy groups on the epoxy-based silica and the amino groups on the 1-aminopropyl-3-methyl imidazole tetrafluoroborate to obtain a hydroxylated silica solution, and the structural formula is as shown in Figure 3 ;

[0008] Step S3, under the protection of nitrogen, hexamethylenetetramine and the hydroxylated silica solution prepared in step S3 are stirred uniformly, 15-17wt% hydrochloric acid aqueous solution is used to adjust the pH to 5.5-6.5, and the mixture is heated to 45-55℃ and stirred for 2-4h. After the reaction is completed, anhydrous DMF is removed by rotary evaporation to obtain a 1-methyl pyridine chloride synthesis catalyst, wherein the ratio of the amount of hexamethylenetetramine and the hydroxylated silica solution is 0.3-0.6g: 25-35mL, and acid-base neutralization reaction occurs between the hydroxyl groups in the hydroxylated silica solution and the hexamethylenetetramine to obtain the 1-methyl pyridine chloride synthesis catalyst.

[0009] Hexamethylenetetramine is a stable, low-toxicity, inexpensive tertiary amine compound. Under acidic conditions, it can react with hydroxylated silica to form a 1-methyl pyridine chloride synthesis catalyst in the form of a protonic ionic salt.

[0010] Further, the preparation method of the modified silica comprises the following steps:

[0011] Step A1, deionized water, 25-28wt% ammonia water and anhydrous ethanol are mixed uniformly to obtain a mixed solution a, wherein the ratio of the amount of deionized water, 25-28wt% ammonia water and anhydrous ethanol is 7-8mL: 6-8mL: 20mL;

[0012] Step A2, 55wt% polyhexyl resorcinol sulfone water solution and anhydrous ethanol are placed in the mixed solution a, ultrasonic treatment for 0.5-1h, stirring for 0.25h at 1000-1200rpm, then tetraethyl orthosilicate is added, continue to stir for 12-16h, after the reaction is completed, remove the ethanol and deionized water by rotary evaporation under reduced pressure, to obtain modified silica, wherein the amount ratio of 55wt% polyhexyl resorcinol sulfone water solution, anhydrous ethanol, mixed solution a and tetraethyl orthosilicate is 1-1.5g:70-80mL:30mL:15-20mL, the ammonia in the mixed solution a can act as a catalyst in the above reaction process, which can promote the hydrolysis of tetraethyl orthosilicate, and the molecular structure of polyhexyl resorcinol sulfone contains a large number of hydroxyl groups, which can be coated in the silica produced by the hydrolysis of tetraethyl orthosilicate, at the same time, the silica has high specific surface area, large pore size and is very stable in acidic medium.

[0013] Polyhexyl resorcinol sulfone contains sulfonic acid group and hydroxyl group, the sulfonic acid group can provide hydrogen ion as a catalyst for nucleophilic reaction, and the hydroxyl group can be grafted with other substances to achieve the purpose of fixing the catalyst.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] In the technical scheme of the present application, the polyhexyl resorcinol sulfone coated inside the silica in the 1-methyl pyridine chloride synthesis catalyst can act as a non-metal oxide supported solid acid, and the electron-donating sulfonic acid group in the polyhexyl resorcinol sulfone can promote the electrophilic substitution reaction of pyridine and chloromethane to generate 1-methyl pyridine chloride, the external silica is chemically bonded with the hydroxylated silica-hexamethyl tetramine with acidic and basic protonic ionic liquid structure, which is prepared by chemical bonding of gamma-(2,3-epoxypropoxy) propyl trimethoxysilane, 1-aminopropyl-3-methyl imidazole tetrafluoroborate and hexamethyl tetramine, the presence of proton hydrogen in the hydroxylated silica and 1-aminopropyl-3-methyl imidazole structure is conducive to the activation of chloromethane, and the presence of hexamethyl tetramine and tetrafluoroboric acid group is conducive to the dehydrogenation of the active methylene on pyridine, which reduces the difficulty of electrophilic substitution reaction of N atom on pyridine with chloromethane, and through synergistic effect, the catalytic performance of the prepared 1-methyl pyridine chloride synthesis catalyst is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The flow chart for the preparation of the 1-methyl pyridine chloride synthesis catalyst of the present application;

[0017] Figure 2 The structural formula of the modified silica in the present application;

[0018] Figure 3The structural formula of the hydroxylated silicon dioxide solution in the present application. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0020] Embodiment 1

[0021] The present embodiment provides a preparation method of modified silicon dioxide, comprising the following steps:

[0022] Step A1, 7.5 mL of deionized water, 7 mL of 26 wt% ammonia water and 20 mL of anhydrous ethanol are added to a three-necked flask, and mechanically mixed uniformly to obtain a mixed solution a;

[0023] Step A2, 1.25 g of 55 wt% aqueous solution of polymyxol sulfobranzine, 75 mL of anhydrous ethanol and 30 mL of the mixed solution a are added to a three-necked flask, ultrasonic treatment is performed for 0.75 h, stirring is performed at a speed of 1100 rpm for 0.25 h, then 17.5 mL of tetraethyl orthosilicate is added, and stirring is continued for 14 h, after the reaction is completed, anhydrous ethanol and deionized water are removed by rotary evaporation under reduced pressure, and the modified silicon dioxide is obtained.

[0024] Embodiment 2

[0025] The present embodiment provides a preparation method of a catalyst for synthesizing 1-methyl pyridine chloride, which is prepared from the following steps:

[0026] Step S1, 4 mL of the modified silicon dioxide prepared, 3 mL of γ-(2, 3-epoxypropoxy) propyl trimethoxysilane and 60 mL of anhydrous ethanol are added to a three-necked flask, mechanically stirred uniformly, heated to 40 DEG C, and stirred for 8 h, after the reaction is completed, centrifugal washing is performed, and vacuum drying is performed at 80 DEG C to obtain epoxy-modified silicon dioxide;

[0027] Step S2, under nitrogen protection, 0.75 g of the epoxy-modified silicon dioxide prepared in step S1, 0.5 mL of 1-aminopropyl-3-methyl imidazole tetrafluoroborate and 40 mL of anhydrous DMF are added to a three-necked flask, mechanically stirred uniformly, heated to 60 DEG C, and stirred for 6 h to obtain a hydroxylated silicon dioxide solution;

[0028] Step S3, under the protection of nitrogen, 0.3g hexamethylenetetramine and 25mL of the hydroxylated silica solution prepared in step S2 were added into a three-necked flask, mechanically stirred uniformly, the pH was adjusted to 5.5 with 15wt% hydrochloric acid aqueous solution, the temperature was raised to 45℃, and stirred for 2h. After the reaction was completed, the anhydrous DMF was removed by rotary evaporation to obtain the 1-methylpyridine chloride synthesis catalyst.

[0029] Example 3

[0030] The present embodiment provides a preparation method of a 1-methylpyridine chloride synthesis catalyst, which is prepared by the following steps:

[0031] Step S1, 4.5mL of the modified silica prepared in Example 1, 3.5mL of γ-(2,3-epoxypropoxy) propyl trimethoxysilane and 62.5mL of anhydrous ethanol were added into a three-necked flask, mechanically stirred uniformly, the temperature was raised to 50℃, and stirred for 9h. After the reaction was completed, centrifugal washing and vacuum drying at 80℃ were performed to obtain the epoxy-modified silica;

[0032] Step S2, under the protection of nitrogen, 1g of the epoxy-modified silica prepared in step S2, 0.75mL of 1-aminopropyl-3-methylimidazole tetrafluoroborate and anhydrous DMF were added into a three-necked flask, mechanically stirred uniformly, the temperature was raised to 65℃, and stirred for 7h to obtain a hydroxylated silica solution;

[0033] Step S3, under the protection of nitrogen, 0.45g hexamethylenetetramine and 30mL of the hydroxylated silica solution prepared in step S2 were added into a three-necked flask, mechanically stirred uniformly, the pH was adjusted to 6 with 16wt% hydrochloric acid aqueous solution, the temperature was raised to 50℃, and stirred for 3h. After the reaction was completed, the anhydrous DMF was removed by rotary evaporation to obtain the 1-methylpyridine chloride synthesis catalyst.

[0034] Example 4

[0035] The present embodiment provides a preparation method of a 1-methylpyridine chloride synthesis catalyst, which is prepared by the following steps:

[0036] Step S1, 5mL of the modified silica prepared in Example 1, 4mL of γ-(2,3-epoxypropoxy) propyl trimethoxysilane and 65mL of anhydrous ethanol were added into a three-necked flask, mechanically stirred uniformly, the temperature was raised to 60℃, and stirred for 10h. After the reaction was completed, centrifugal washing and vacuum drying at 80℃ were performed to obtain the epoxy-modified silica;

[0037] Step S3, under nitrogen protection, 1.25 g of the epoxy-modified silica prepared in step S1, 1 mL of 1-aminopropyl-3-methylimidazole tetrafluoroborate and 50 mL of anhydrous DMF were added into a three-necked flask, mechanically stirred uniformly, warmed to 70°C, stirred for 8 h to obtain a hydroxyl-modified silica solution;

[0038] Step S3, under nitrogen protection, 0.6 g of hexamethylenetetramine and 35 mL of the hydroxyl-modified silica solution prepared in step S2 were added into a three-necked flask, mechanically stirred uniformly, the pH was adjusted to 6.5 with 17 wt% hydrochloric acid aqueous solution, warmed to 55°C, stirred for 4 h, after the reaction was completed, the anhydrous DMF was removed by rotary evaporation to obtain a 1-methylpyridine chloride catalyst for synthesis.

[0039] Comparative Example 1

[0040] The aqueous solution of polynucleophilic sulfobenzoic acid in Example 1 was removed, and the remaining raw materials and preparation process were unchanged.

[0041] Comparative Example 2

[0042] The tetraethyl orthosilicate in Example 1 was removed, and the remaining raw materials and preparation process were unchanged.

[0043] Comparative Example 3

[0044] The γ-(2,3-epoxypropoxy)propyl trimethoxysilane in step S1 in Example 3 was removed, and the remaining raw materials and preparation process were unchanged.

[0045] Comparative Example 4

[0046] The 1-aminopropyl-3-methylimidazole tetrafluoroborate in step S2 in Example 3 was removed, and the remaining raw materials and preparation process were unchanged.

[0047] Comparative Example 5

[0048] The hexamethylenetetramine in step S3 in Example 3 was removed, and the remaining raw materials and preparation process were unchanged.

[0049] Application Example

[0050] At room temperature, the 2L autoclave was replaced by N2 for three times, first, the pyridine was pumped into the charging pipeline by peristaltic pump, the charging pipeline was filled with pyridine to exhaust, then 600g pyridine with 99.8% content and 30g 1-methyl pyridine chloride synthesis catalyst were pumped into the autoclave by peristaltic pump, the pyridine in the autoclave was heated to 60℃, liquid chloromethane was added dropwise into the autoclave, the speed of liquid chloromethane was adjusted to 4mL / min by plunger pump, the chloromethane charging time was 2h (the total amount of chloromethane was 441.6g), during the chloromethane dropwise process, after the charging was completed, the chloromethane inlet was closed, the temperature was kept at 65℃ for 30min, the pressure of the reaction was 1.25MPa, after the reaction was completed, the autoclave was cooled and discharged, and 1-methyl pyridine chloride was obtained.

[0051] Performance detection

[0052] The 1-methyl pyridine chloride synthesis catalyst prepared by examples 2-4 and comparative examples 1-5 was applied to application examples, and the content and reaction yield of 1-methyl pyridine chloride were detected by high performance liquid chromatography, and the specific detection results are shown in table 1:

[0053] High performance liquid chromatography detection conditions:

[0054] The chromatographic column was Waters Symmetry C18 column (150mm x 3 9mm i.d, 5μm); the mobile phase was C2H3N: H2O = 29:71, containing triethylamine 0.3%, pH = 3 (phosphoric acid adjustment), the flow rate was 1mL / min; the sample size was 10μL; the detector was DAD, and the detection wavelength was 260nm.

[0055] Table 1

[0056]

[0057] As can be seen from table 1, compared with comparative example 1-5, the 1-methyl pyridine chloride prepared by example 2-4 has higher content and yield, and the reason for the low content and reaction yield of 1-methyl pyridine chloride prepared by comparative example 1-5 is analyzed as follows:

[0058] In comparative example 1, the polymercaptol sulfon was removed, resulting in a large number of electron-donating sulfonic acid groups missing in the prepared catalyst, which further led to the reduction of the catalytic performance of the catalyst;

[0059] In comparative example 2, the tetraethyl orthosilicate was removed, resulting in the lack of solid acid catalyst and the loading material of proton type ionic base material in the prepared catalyst, so that the prepared catalyst could not play its good synergistic performance, and finally the performance of the catalyst was reduced;

[0060] In the comparative example 3, due to the removal of γ-(2, 3-epoxypropoxy) propyl trimethoxysilane, 1-aminopropyl-3-methyl imidazole tetrafluoroborate and hexamethylenetetramine added in the subsequent reaction are fixed on the surface of silica by chemical bonding, the synergy is reduced, and finally the performance of the catalyst is reduced;

[0061] In the comparative example 4, due to the removal of 1-aminopropyl-3-methyl imidazole tetrafluoroborate, the 1-aminopropyl-3-methyl imidazole structure beneficial to the activation of chloromethane and the tetrafluoroboric acid group structure beneficial to the dehydrogenation of the active methylene on pyridine are missing in the prepared catalyst, and at the same time, the subsequent addition of hexamethylenetetramine cannot play a good synergistic effect with the above structure, finally resulting in the performance of the prepared catalyst being reduced;

[0062] In the comparative example 5, due to the removal of hexamethylenetetramine, the structure beneficial to the dehydrogenation of the active methylene on pyridine is missing in the prepared catalyst, and finally the performance of the prepared catalyst is reduced.

[0063] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for producing a catalyst for the synthesis of 1-methylpyridinium chloride, characterized by, Comprising the following steps: S1: Preparation of epoxy-modified silica The modified silica and gamma-(2,3-epoxypropoxy) propyl trimethoxysilane are added to anhydrous ethanol, stirred uniformly, heated to 40-60℃, and continue to stir for 8-10h. After the reaction is completed, centrifugal washing and vacuum drying at 80℃ are performed to obtain the epoxy-modified silica. S2: Preparation of hydroxylated silica solution Under nitrogen protection, the epoxy-modified silica prepared in step S1 and 1-aminopropyl-3-methyl imidazole tetrafluoroborate are added to anhydrous DMF, stirred uniformly, heated to 60-70℃, and stirred for 6-8h to obtain the hydroxylated silica solution. S3: Preparation of 1-methyl pyridine chloride synthesis catalyst Under nitrogen protection, the hexamethylenetetramine and the hydroxylated silica solution prepared in step S2 are stirred uniformly, and 15wt%-17wt% hydrochloric acid aqueous solution is used to adjust the pH to 5.5-6.

5. The mixture is heated to 45-55℃ and stirred for 2-4h. After the reaction is completed, anhydrous DMF is removed by rotary evaporation to obtain the 1-methyl pyridine chloride synthesis catalyst. The preparation method of the modified silica comprises the following steps: Step A1, deionized water, 25-28wt% ammonia water and anhydrous ethanol are uniformly mixed to obtain a mixed solution a, wherein the amount ratio of deionized water, 25-28wt% ammonia water and anhydrous ethanol is 7-8mL:6-8mL:20mL; Step A2, 55wt% polyhexamethylol blue sulfonamide aqueous solution and anhydrous ethanol are placed in the mixed solution a, ultrasonic treatment is performed for 0.5-1h, stirring is performed at a speed of 1000-1200rpm for 0.25h, then tetraethyl orthosilicate is added, and stirring is continued for 12-16h. After the reaction is completed, ethanol and deionized water are removed by rotary evaporation under reduced pressure to obtain the modified silica.

2. The method for preparing a catalyst for synthesizing 1-methylpyridine chloride according to claim 1, characterized by, The amount ratio of the modified silica, gamma-(2,3-epoxypropoxy) propyl trimethoxysilane and anhydrous ethanol in S1 is 4-5mL:3-4mL:60-65mL.

3. The method for preparing the catalyst for the synthesis of 1-methylpyridine chloride as described in claim 1, characterized in that, The amount ratio of the epoxy-modified silica, 1-aminopropyl-3-methyl imidazole tetrafluoroborate and anhydrous DMF in S2 is 0.75-1.25g:0.5-1mL:40-50mL.

4. The method for preparing the catalyst for the synthesis of 1-methylpyridine chloride as described in claim 1, characterized in that, The amount ratio of the hexamethylenetetramine and the hydroxylated silica solution in S3 is 0.3-0.6g:25-35mL.

5. The method for preparing the catalyst for the synthesis of 1-methylpyridine chloride as described in claim 1, characterized in that, The amount ratio of the 55wt% polyhexamethylol blue sulfonamide aqueous solution, anhydrous ethanol, the mixed solution a and tetraethyl orthosilicate is 1-1.5g:70-80mL:30mL:15-20mL.

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