Dicationic quaternary ammonium base deep eutectic catalyst, synthetic method thereof and application of dicationic quaternary ammonium base deep eutectic catalyst in catalyzing RT base precursor reaction

Abstract

The invention relates to a dicationic quaternary ammonium strong base deep eutectic catalyst and a novel preparation method thereof, and relates to an application of the catalyst in an RT base precursor synthesis process. The preparation method comprises the following steps: by taking di-tert-amine as a raw material, firstly preparing sulfuric acid monoester quaternary ammonium salt by quaternization of sulfuric acid diester under a low-temperature condition, then performing high-temperature hydrolysis to obtain hydrogen sulfate quaternary ammonium salt, and finally performing ion exchange in alcohol to obtain quaternary ammonium base. According to the synthesis method, halogen is prevented from being introduced in the quaternization process, corrosion to equipment is reduced, the reaction speed is high, the conversion rate is high, and the product purity is high. And the synthesized quaternary ammonium base reacts with alcohols to prepare the dication type quaternary ammonium base deep eutectic catalyst with different proportions, and the dication type quaternary ammonium base deep eutectic catalyst can be used for catalyzing the RT base precursor synthesis reaction, has excellent catalytic effect and stability, and has wide application prospects.

Description

Technical Field

[0001] The present invention relates to a new process for synthesizing a deep eutectic catalyst and its application, and in particular to a process for preparing a quaternary ammonium base by using dimethyl sulfate and a ditertiary amine as raw materials through alkylation, hydrolysis and ion exchange steps, and finally reacting the quaternary ammonium base with a polyol to obtain a deep eutectic catalyst, as well as the application of the catalyst in the RT base synthesis process. Background Art

[0002] Quaternary ammonium alkali is a compound with the general formula [R4N]OH, where R is 4 identical or different hydrocarbon groups. Its molecular structure is similar to ammonium hydroxide and can be regarded as NH4 + Derivatives with hydrogen substituted in the quaternary ammonium base are easily deliquescent, readily soluble in water, and 100% ionized. Quaternary ammonium bases are strong organic bases with alkalinity comparable to that of NaOH or KOH and are typically used or stored in aqueous solutions. Quaternary ammonium bases have a wide range of industrial applications, primarily as catalysts for the preparation of organosilicones, phase transfer catalysts for promoting two-phase reactions, and templates for the synthesis of molecular sieves. They are widely used in the electronics industry, automotive exhaust purification, and VOC treatment. Quaternary ammonium bases can act as phase transfer catalysts, and their exceptionally strong alkalinity makes them widely used in the condensation of aniline and nitrobenzene to synthesize RT-base precursors. For example, patents CN105585507B and CN101906048A report the use of tetramethylammonium hydroxide, the simplest quaternary ammonium base, as a catalyst for the synthesis of RT-base precursors. However, tetramethylammonium hydroxide suffers from the drawbacks of easy decomposition and difficulty in recycling. Patent CN101830811B also discloses a method for catalyzing a condensation reaction using a mixture of a diquaternary ammonium base and a monoquaternary tetramethylammonium hydroxide base. This method improves the selectivity of nitrobenzene in the condensation reaction, while also enhancing the stability and recovery rate of the base. Therefore, it is of great significance to develop new strong quaternary ammonium bases with excellent catalytic effects and high stability, and to further modify these quaternary ammonium bases for use in the catalytic synthesis of RT base precursors.

[0003] At present, the research of quaternary ammonium base is more concentrated on the monoquaternary ammonium base, such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH) and tetrabutylammonium hydroxide (TBAH) etc., for the research of dicationic quaternary ammonium base based on synthesis of diamine and its application in RT base precursor synthesis is less.The synthesis of quaternary ammonium base is generally based on halogenated quaternary ammonium salt as raw material, and uses and comprises that methods such as silver oxide method, alkali displacement method, ion exchange resin method and electrolysis process that halide ion is changed into hydroxide ion and makes.As patent CN114560863A has disclosed a kind of method for raw material synthesis quaternary ammonium base based on triethylenediamine, patent CN116180111A has disclosed a kind of method for synthesizing cyclohexyltrimethylammonium hydroxide.These two all are to prepare quaternary ammonium base again after synthesizing corresponding halogenated quaternary ammonium salt first, and wherein the former uses ion exchange process, and the latter uses electrolysis process. Halogenated quaternary ammonium salts are obtained by quaternization of tertiary amines. The current mainstream synthesis method uses halogenated hydrocarbons as alkylating agents. For example, patent CN116162943A discloses a method for obtaining halogenated quaternary ammonium salts by directly reacting trimethylamine with ethyl chloride. This method can produce high-purity halogenated quaternary ammonium salts without the use of a catalyst, resulting in low production costs. However, the introduced halogen also has a serious corrosive effect on equipment.

[0004] In view of this, the present invention provides a new method for synthesizing a deep eutectic catalyst, which mainly includes two steps: the synthesis of a dicationic quaternary ammonium base and the synthesis of a deep eutectic catalyst. The method does not require the introduction of halogen, and the reaction conditions are relatively mild, the steps are simple, and the product yield is high. The synthesized new dicationic quaternary ammonium base deep eutectic catalyst can be used as a catalyst for the condensation of aniline and nitrobenzene to synthesize RT base precursors, and has the characteristics of good effect and high stability. Summary of the Invention

[0005] The present invention provides a novel method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst. The method does not require the introduction of halogen ions, and the reaction is carried out under relatively mild conditions.

[0006] The present invention provides a dicationic quaternary ammonium base deep eutectic catalyst, characterized in that the dicationic quaternary ammonium base deep eutectic catalyst is composed of a dicationic quaternary ammonium polyol salt, a dicationic quaternary ammonium hydroxide salt and water, wherein the molar ratio of the dicationic quaternary ammonium polyol salt to the dicationic quaternary ammonium hydroxide salt is 1:1-1:0, and the water content is 35%-45%; wherein the dicationic structural formula is [(CH3)4N-RN(CH3)4] 2+ , R is selected from alkyl, phenyl and alkyl containing ether group, preferably alkyl with less than six carbon atoms, more preferably methyl, ethyl and propyl; wherein the polyol anion is ethylene glycol anion [HOCH2CH2O] - or glycerol anion [HOCH2(CHOH)CH2O]- , preferably ethylene glycol anion.

[0007] The present invention also provides a method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst, which is characterized by comprising the following steps: Step 1, synthesis of a sulfate monoester type quaternary ammonium salt: dissolving a ditertiary amine in a solvent, slowly adding dimethyl sulfate dropwise under low temperature and vigorous stirring to react; heating after the addition is complete, and continuing the heat-keeping reaction; after the reaction is complete, evaporating most of the solvent to obtain a sulfate monoester type quaternary ammonium salt; Step 2, hydrolysis of the sulfate monoester type quaternary ammonium salt: adding water to the sulfate monoester type quaternary ammonium salt, heating the system to boiling, continuing the hydrolysis, and evaporating the alcohol and most of the water generated by the reaction to obtain the hydrogen sulfate type quaternary ammonium salt; Step 3, ion exchange: dissolving the above-mentioned hydrogen sulfate type quaternary ammonium salt in methanol, adding dropwise an inorganic strong base methanol solution, filtering to remove sulfate precipitate after ion exchange, and obtaining a quaternary ammonium base methanol solution; Step 4, synthesis of deep eutectic catalyst: water and polyol are added to the methanol solution of quaternary ammonium strong base, part of the quaternary ammonium base reacts with the polyol to form the corresponding polyol salt, and the methanol is removed under reduced pressure and heating conditions. The remaining quaternary ammonium base, polyol salt and water constitute a dicationic quaternary ammonium base deep eutectic catalyst.

[0008] Generally, the synthesis method of the present invention comprises the following steps: Step 1, Synthesis of a Sulfate Monoester Quaternary Ammonium Salt: Using anhydrous methanol as the solvent, add a predetermined amount of a ditertiary amine to a reaction vessel. Slowly add dimethyl sulfate (in a corresponding molar ratio) dropwise to the reaction vessel under low temperature and vigorous stirring. After the addition is complete, raise the temperature to 40-60°C and continue the reaction at this temperature for 1-2 hours. After the reaction is complete, remove most of the solvent to obtain a Sulfate Monoester Quaternary Ammonium Salt.

[0009] The reaction formula is: N,N,N,N -Tetramethyl-1,3-propylenediamine and dimethyl sulfate as examples)

[0010] In the above reaction, dimethyl sulfate is directly used as the alkylating agent, reacting with a ditertiary amine in a single step to produce the corresponding quaternary ammonium salt. The entire process does not require the introduction of additional halogens. Furthermore, this method produces a high-purity, fast-reacting sulfate monoester-type quaternary ammonium salt, and the product can be recovered by removing the solvent. Furthermore, the reaction does not require high reaction temperatures and does not generate gas during the process, making the overall experimental conditions relatively mild.

[0011] The ditertiary amine structure is (CH3)2NRN(CH3)2, wherein R includes but is not limited to alkyl, phenyl and alkyl containing ether group, among which methyl, ethyl, propyl and other alkyl groups with less than six carbon atoms are preferred; the mass ratio of the ditertiary amine used to methanol is 1:0.9~1:1.2; the molecular formula of the dimethyl sulfate is (CH3O)2SO2, and the molar ratio of the ditertiary amine to dimethyl sulfate is 1:2~1:2.4, among which the preferred ratio is 1:2.1.

[0012] The mass ratio of the methanol to the ditertiary amine is 1:0.9 to 1:1.2.

[0013] The dimethyl sulfate is slowly added to the ditertiary amine in a dropwise manner, and the total dropwise addition time is controlled to be 0.5-2 hours, preferably about 1 hour. During the dropwise addition process, the reaction temperature is controlled to be 0-25°C. After the dropwise addition is completed, the temperature is raised to 40-80°C and kept warm for 0.5-2 hours, preferably 50-60°C and kept warm for 1 hour.

[0014] After the reaction in step 1 is completed, most of the methanol is removed under normal pressure heating conditions, and the heating temperature is controlled to be 70-80°C.

[0015] Step 2, hydrolysis of sulfate monoester type quaternary ammonium salt: add a certain amount of water to the sulfate monoester type quaternary ammonium salt, heat the system to boiling, continue hydrolysis for a period of time, evaporate the alcohol and most of the water generated by the reaction, and obtain hydrogen sulfate type quaternary ammonium salt. The reaction formula is: (with N,N,N,N’,N’,N’ -Hexamethyl-1,3-propanediammonium monomethyl sulfate as an example)

[0016] During the hydrolysis, the amount of water added to the sulfuric acid monoester type quaternary ammonium salt is 5:1 to 10:1, and the addition method is slow dropwise addition, and the dropwise addition time is controlled to be 0.5 to 2 hours; the hydrolysis temperature is controlled to be 120 to 150 ° C, the hydrolysis time is 0.5 to 2 hours, and the preferred hydrolysis time is 1 hour. The water and alcohol evaporated by the reaction are condensed into another container for collection.

[0017] Step 3, ion exchange: dissolve hydrogen sulfate type quaternary ammonium salt in methanol, dropwise add a certain amount of inorganic strong base methanol solution, filter to remove sulfate precipitate after ion exchange, and obtain quaternary ammonium base methanol solution.

[0018] The reaction formula is: N,N,N,N’,N’,N’ -Hexamethyl-1,3-propanediammonium hydrogen sulfate as an example)

[0019] In the ion exchange step, the solvent used is methanol with a purity of 95% (containing 5% water). The inorganic strong base used is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, preferably sodium hydroxide. The ratio of the inorganic strong base (calculated as hydroxide) to the added sulfate diester is 2:1. The inorganic strong base methanol solution is dripped into the hydrogen sulfate-type quaternary ammonium salt methanol solution for 0.5 to 1 hour.

[0020] In the ion exchange, after adding an inorganic strong base methanol solution, the temperature is raised to 40-60° C., fully stirred and kept warm for 4-6 hours; after the ion exchange, the ion exchange rate obtained by the barium chloride method is not less than 99%.

[0021] Step 4, synthesis of a deep eutectic catalyst: adding a certain amount of water and a polyol to the obtained quaternary ammonium strong base methanol solution, removing the methanol under reduced pressure and heating conditions to obtain a dicationic quaternary ammonium base deep eutectic catalyst.

[0022] The reaction formula is: N,N,N,N’,N’,N’ -hexamethyl-1,3-propanediammonium hydroxide and ethylene glycol as examples)

[0023] In the synthesis of the deep eutectic catalyst, after the exchange is completed, the molar ratio of additional water to quaternary ammonium base is 8:1, and the added polyol is ethylene glycol, propylene glycol, etc., among which ethylene glycol is preferred. The amount added varies depending on the number of hydroxyl groups contained therein and the specific composition of the obtained deep eutectic catalyst. Generally speaking, the molar ratio of the added polyol to the quaternary ammonium base is 0.5:1~1:1, and the corresponding molar ratio of the polyol salt to the quaternary ammonium base is 1:1~1:0; the methanol removal temperature is 50~60°C, and the vacuum degree is 0.085~0.095 MPa; the water content of the obtained deep eutectic catalyst is 35%~45%.

[0024] The present invention also provides the use of the synthesized deep eutectic catalyst for catalyzing the condensation of aniline and nitrobenzene to synthesize an RT base precursor. A dicationic quaternary ammonium base deep eutectic catalyst, aniline, and nitrobenzene are uniformly mixed in appropriate proportions and reacted under certain reaction temperature and vacuum conditions to obtain the RT base precursor.

[0025] The reaction formula is as follows:

[0026] Generally, the catalytic reaction is operated under reduced pressure and heating conditions; the molar ratio of the reactants aniline, nitrobenzene and deep eutectic catalyst (calculated in terms of nitrogen content) is (4-6):1:(1-1.2); the reaction temperature is 70-80°C, the reaction vacuum is 0.085-0.095 MPa, and the reaction time is 4-5 h.

[0027] Beneficial effects: The present invention generates a sulfate monoester-type quaternary ammonium salt by directly reacting a ditertiary amine with a sulfate diester, thereby avoiding the introduction of halogens during the quaternization process, and has a fast reaction speed, a high conversion rate, a high product purity, and is easily recyclable. No catalyst is required, and the reaction conditions are mild. The sulfate waste generated during the ion exchange is non-toxic and harmless and easy to handle, thus providing a green and environmentally friendly production route. At the same time, this method provides a new route for the synthesis of quaternary ammonium bases, enriching the types of quaternary ammonium bases. The dicationic deep eutectic catalyst synthesized thereby has excellent catalytic effect and stability in the application of catalytic synthesis of RT base precursors. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to examples so that those skilled in the art can implement the invention with reference to the description. Example 1

[0029] Step 1: Weigh 65 g of tetramethylpropylenediamine into a flask and dissolve it in 75 g of anhydrous methanol. Use an ice-water bath to control the reaction temperature at 5°C. Weigh 133 g of dimethyl sulfate into a constant pressure dropping funnel and slowly add it dropwise to the flask at a constant speed for 57 minutes. After the addition is complete, use an oil bath to raise the temperature to 50°C and keep it warm for 1 hour. After the reaction is completed, raise the temperature to 70°C and remove most of the methanol to obtain N,N,N,N’,N’,N’ - Hexamethylpropanediammonium monomethyl sulfate; Step 2: Add all the obtained hexamethylpropane diammonium monomethyl sulfate salt into a flask, heat it to 140 °C using an oil bath, and continuously add 60 g of water dropwise under sufficient stirring to carry out hydrolysis reaction. Hydrolysis is carried out for a total of 1 h to obtain hexamethylpropane diammonium hydrogen sulfate. The evaporated water and methanol are condensed and collected in another flask; Step 3: Add 100 g of 95% methanol to the flask containing hexamethylpropane diammonium hydrogen sulfate to fully dissolve it. Take another flask and add 400 g of 95% methanol and 84 g of sodium hydroxide solid. After fully dissolving, add dropwise to the flask containing hexamethylpropane diammonium hydrogen sulfate for 1 hour; heat to 50 ° C in a water bath, keep warm for 4 hours, and then filter and collect the filtrate to obtain 692 g of a clear hexamethylpropane diammonium hydroxide methanol solution; Step 4: After the ion exchange is completed, 55 g of water and 31 g of ethylene glycol are added to the flask, the temperature is controlled at 50 ° C and the vacuum degree is 0.09 MPa, and the methanol is removed using a rotary evaporator to obtain 194 g of a deep eutectic catalyst. The specific components are determined by nuclear magnetic resonance, acid-base titration and Karl Fischer water determination as 70 g of hexamethylpropylenediammonium glycolate, 49 g of hexamethylpropylenediammonium hydroxide, and 74 g of water, wherein the molar ratio of hexamethylpropylenediammonium glycolate to hexamethylpropylenediammonium hydroxide is 1:1.

[0030] Catalytic condensation: Add 186 g (2 mol) of aniline, 49 g (0.4 mol) of nitrobenzene, and 78 g (0.2 mol) of a deep eutectic catalyst to a flask, stir evenly, heat to 70°C, adjust the vacuum to 0.085 MPa, and continue the reaction for 4 h. Liquid chromatography analysis shows a nitrobenzene conversion of 99% and a 96% yield of 4-nitrodiphenylamine and 4-nitrosodiphenylamine. Example 2

[0031] Step 1: Weigh 56 g of triethylenediamine into a flask, add 65 g of anhydrous methanol, and mix thoroughly. Use an ice-water bath to maintain the reaction temperature at 5°C. Weigh 133 g of dimethyl sulfate into a constant-pressure dropping funnel and slowly add it dropwise to the flask over a period of 58 minutes. After the addition is complete, heat the mixture to 50°C in an oil bath and maintain for 1 hour. After the reaction is complete, heat the mixture to 75°C to remove most of the methanol to obtain dimethyltriethylenediammonium monomethyl sulfate. Step 2: Add all the obtained dimethyltriethylenediammonium sulfate monomethyl ester salt into the flask, heat it to 130 °C using an oil bath, and continue to drop 80 g of water under sufficient stirring to carry out hydrolysis reaction for a total of 1 h to obtain N,N’ - dimethyltriethylenediammonium hydrogen sulfate, the distilled water and methanol are condensed into another flask; Step 3: Add 80 g of 95% methanol to the flask containing dimethyltriethylenediammonium hydrogen sulfate to fully dissolve it. Take another flask and add 400 g of 95% methanol and 84 g of sodium hydroxide solid to fully dissolve it. Then add it dropwise to the flask containing dimethyltriethylenediammonium hydrogen sulfate for 1 hour. Heat it to 55°C in a water bath, keep it warm for 4 hours, and then filter and collect the filtrate to obtain 627 g of a clear dimethyltriethylenediammonium hydroxide methanol solution. Step 4: After the ion exchange is completed, 60 g of water and 31 g of ethylene glycol are added to the flask, the temperature is controlled at 50 ° C and the vacuum degree is 0.095 MPa, and the methanol is removed using a rotary evaporator to obtain 188 g of deep eutectic catalyst. The specific components are determined by nuclear magnetic resonance, acid-base titration and Karl Fischer water determination as 66 g of dimethyltriethylenediammonium glycol salt, 44 g of dimethyltriethylenediammonium hydroxide salt, and 77 g of water, wherein the molar ratio of dimethyltriethylenediammonium glycol salt and dimethyltriethylenediammonium hydroxide salt is 1:1.

[0032] Catalytic condensation: Add 223 g (2.4 mol) of aniline, 49 g (0.4 mol) of nitrobenzene, and 75 g (0.2 mol) of a deep eutectic catalyst to a flask, stir well, heat to 70°C, adjust the vacuum to 0.085 MPa, and continue the reaction for 4 h. Liquid chromatography analysis shows a nitrobenzene conversion of 77% and a 73% yield of 4-nitrodiphenylamine and 4-nitrosodiphenylamine. Example 3

[0033] Step 1: Weigh 80 g of bis(dimethylaminoethyl)ether into a flask and dissolve it in 90 g of anhydrous methanol. Control the reaction temperature at 5°C using an ice-water bath. Weigh 133 g of dimethyl sulfate into a constant-pressure dropping funnel and slowly add it dropwise to the flask over a period of 54 minutes. After the addition is complete, heat the mixture to 50°C using an oil bath and maintain this temperature for 1 hour. After the reaction is complete, heat the mixture to 80°C to remove most of the methanol, yielding bis(trimethylaminoethyl)ether monomethyl sulfate. Step 2: Add all the obtained bistrimethylaminoethyl ether monomethyl sulfate salt into a flask, heat it to 140 °C using an oil bath, and continuously add 60 g of water dropwise under sufficient stirring to carry out hydrolysis reaction. Hydrolysis is carried out for a total of 1 h to obtain hexamethylpropanediammonium hydrogen sulfate. The evaporated water and methanol are condensed and collected in another flask; Step 3: Add 100 g of 95% methanol to the flask containing bistrimethylaminoethyl ether hydrogen sulfate to fully dissolve it. Take another flask and add 420 g of 95% methanol and 84 g of sodium hydroxide solid. After fully dissolving, add dropwise to the flask containing bistrimethylaminoethyl ether hydrogen sulfate for 1 hour; heat to 50 ° C in a water bath, keep warm for 4 hours, and then filter and collect the filtrate to obtain 739 g of a clear hexamethylpropanediammonium hydroxide methanol solution; Step 4: After the ion exchange is completed, 60 g of water and 31 g of ethylene glycol are added to the flask, the temperature is controlled at 50 ° C and the vacuum degree is 0.09 MPa, and the methanol is removed using a rotary evaporator to obtain 219 g of a deep eutectic catalyst. The specific components are determined by nuclear magnetic resonance, acid-base titration and Karl Fischer water determination as 78 g of bistrimethylaminoethyl ether glycol salt, 56 g of bistrimethylaminoethyl ether hydroxide salt, and 85 g of water, wherein the molar ratio of bistrimethylaminoethyl ether glycol salt and bistrimethylaminoethyl ether hydroxide salt is 1:1.

[0034] Catalytic condensation: Add 149 g (1.6 mol) of aniline, 49 g (0.4 mol) of nitrobenzene, and 88 g (0.2 mol) of a deep eutectic catalyst to a flask, stir well, heat to 75°C, adjust the vacuum to 0.095 MPa, and continue the reaction for 4 h. Liquid chromatography analysis shows a nitrobenzene conversion of 87% and a yield of 84% for 4-nitrodiphenylamine and 4-nitrosodiphenylamine. Example 4

[0035] Step 1: Weigh 86 g of tetramethylhexanediamine into a flask, add 103 g of anhydrous methanol and mix well. Use an ice-water bath to control the reaction temperature at 5°C. Weigh 133 g of dimethyl sulfate into a constant pressure dropping funnel and slowly add it dropwise into the flask for 55 minutes. After the addition is complete, use an oil bath to raise the temperature to 50°C and keep it warm for 1 hour. After the reaction is complete, raise the temperature to 70°C and remove most of the methanol to obtain N,N,N,N’,N’,N’ - Hexamethylhexanediammonium monomethyl sulfate; Step 2: Add all the obtained hexamethylhexanediammonium monomethyl sulfate salt into a flask, heat it to 140 °C using an oil bath, and continuously add 80 g of water dropwise under sufficient stirring to carry out hydrolysis reaction. Hydrolysis is carried out for a total of 1 h to obtain hexamethylhexanediammonium hydrogen sulfate. The evaporated water and methanol are condensed and collected in another flask; Step 3: Add 120 g of 95% methanol to the flask containing hexamethylhexanediammonium hydrogen sulfate to fully dissolve it. Take another flask and add 400 g of 95% methanol and 84 g of sodium hydroxide solid. After fully dissolving, add the resulting solution dropwise to the flask containing hexamethylhexanediammonium hydrogen sulfate for 1 hour. Heat the mixture to 50°C in a water bath, keep warm for 4 hours, and then filter and collect the filtrate to obtain 679 g of a clear hexamethylhexanediammonium hydroxide methanol solution. Step 4: After the ion exchange is completed, 55 g of water and 62 g of ethylene glycol are added to the flask. The temperature is controlled at 50 °C and the vacuum degree is 0.09 MPa. Methanol is removed using a rotary evaporator to obtain 251 g of a deep eutectic catalyst. The specific composition is determined by nuclear magnetic resonance, acid-base titration, and Karl Fischer water determination to be 162 g of hexamethylhexanediammonium glycolate and 89 g of water.

[0036] Catalytic condensation: Add 186 g (2 mol) of aniline, 49 g (0.4 mol) of nitrobenzene, and 100 g (0.2 mol) of a deep eutectic catalyst to a flask, stir evenly, heat to 70°C, adjust the vacuum to 0.085 MPa, and continue the reaction for 4 h. Liquid chromatography analysis shows a nitrobenzene conversion of 94% and a 92% yield of 4-nitrodiphenylamine and 4-nitrosodiphenylamine. Example 5

[0037] Step 1: Weigh 86 g of tetramethylhexanediamine into a flask, add 99 g of anhydrous methanol and mix well. Use an ice-water bath to control the reaction temperature at 5°C. Weigh 133 g of dimethyl sulfate into a constant pressure dropping funnel and slowly add it dropwise into the flask at a constant speed for 60 minutes. After the addition is complete, use an oil bath to raise the temperature to 50°C and keep it warm for 1 hour. After the reaction is completed, raise the temperature to 70°C and remove most of the methanol to obtain N,N,N,N’,N’,N’ - Hexamethylhexanediammonium monomethyl sulfate; Step 2: Add all the obtained hexamethylhexanediammonium monomethyl sulfate salt into a flask, heat it to 145 °C using an oil bath, and continuously add 75 g of water dropwise under sufficient stirring to carry out hydrolysis reaction. Hydrolysis is carried out for a total of 1 h to obtain hexamethylhexanediammonium hydrogen sulfate. The evaporated water and methanol are condensed and collected in another flask; Step 3: Add 100 g of 95% methanol to the flask containing hexamethylhexanediammonium hydrogen sulfate to fully dissolve it. Take another flask and add 390 g of 95% methanol and 84 g of sodium hydroxide solid. After fully dissolving, add the resulting solution dropwise to the flask containing hexamethylhexanediammonium hydrogen sulfate for 1 hour. Heat the mixture to 50°C in a water bath, keep warm for 4 hours, and then filter and collect the filtrate to obtain 656 g of a clear hexamethylhexanediammonium hydroxide methanol solution. Step 4: After the ion exchange is completed, 65 g of water and 46 g of propylene glycol are added to the flask, the temperature is controlled at 50 ° C and the vacuum degree is 0.095 MPa, and most of the methanol is removed using a rotary evaporator to obtain 246 g of a deep eutectic catalyst. The specific components are determined by nuclear magnetic resonance, acid-base titration and Karl Fischer water determination as 96 g of hexamethylhexammonium diammonium propylene glycol salt, 59 g of hexamethylhexammonium diammonium hydroxide salt, and 91 g of water, wherein the molar ratio of hexamethylhexammonium diammonium propylene glycol salt to hexamethylhexammonium diammonium hydroxide salt is 1:1.

[0038] Catalytic condensation: Add 186 g (2 mol) of aniline, 49 g (0.4 mol) of nitrobenzene, and 118 g (0.24 mol) of a deep eutectic catalyst to a flask, stir evenly, heat to 75°C, adjust the vacuum to 0.095 MPa, and continue the reaction for 4 h. Liquid chromatography analysis shows a nitrobenzene conversion of 97% and a 91% yield of 4-nitrodiphenylamine and 4-nitrosodiphenylamine.

[0039] The beneficial effects of the embodiment are as follows: in the preparation process of the dicationic quaternary ammonium base, an innovative dimethyl sulfate quaternization-hydrolysis-ion exchange route is used, which avoids the use of halogenated hydrocarbons, has a fast reaction speed, mild conditions, high product conversion rate, simple separation, and the methanol and water in the preparation process can be recycled and reused. The sulfate waste by-product in the ion exchange is non-toxic and harmless and easy to handle, which is a green and environmentally friendly production route; at the same time, this type of dicationic deep eutectic catalyst can be used to catalyze the condensation of nitrobenzene and aniline to synthesize RT base precursors, with excellent catalytic effect.

Claims

1. A dicationic quaternary ammonium base deep eutectic catalyst, characterized in that: The dicationic quaternary ammonium base deep eutectic catalyst is composed of dicationic quaternary ammonium polyol salt, dicationic quaternary ammonium hydroxide salt and water, wherein the molar ratio of dicationic quaternary ammonium polyol salt to dicationic quaternary ammonium hydroxide salt is 1:1-1:0, and the water content is 35%-45%; wherein the dicationic structural formula is [(CH3)4N-RN(CH3)4] 2+ , R is selected from alkyl, phenyl and alkyl containing ether group, preferably alkyl with less than six carbon atoms, more preferably methyl, ethyl and propyl; the polyol anion is ethylene glycol anion [HOCH2CH2O] - or glycerol anion [HOCH2(CHOH)CH2O] - , preferably ethylene glycol anion.

2. A method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst, characterized by: Including the following step; Step 1, synthesis of a sulfate monoester type quaternary ammonium salt: dissolving a ditertiary amine in a solvent, slowly adding dimethyl sulfate dropwise under low temperature and vigorous stirring to react; heating after the addition is complete, and continuing the heat-keeping reaction; after the reaction is complete, evaporating most of the solvent to obtain a sulfate monoester type quaternary ammonium salt; Step 2, hydrolysis of the sulfate monoester type quaternary ammonium salt: adding water to the sulfate monoester type quaternary ammonium salt, heating the system to boiling, continuing the hydrolysis, and evaporating the alcohol and most of the water generated by the reaction to obtain the hydrogen sulfate type quaternary ammonium salt; Step 3, ion exchange: dissolving the above-mentioned hydrogen sulfate type quaternary ammonium salt in methanol, adding dropwise an inorganic strong base methanol solution, filtering to remove sulfate precipitate after ion exchange, and obtaining a quaternary ammonium base methanol solution; Step 4, synthesis of deep eutectic catalyst: water and polyol are added to the methanol solution of quaternary ammonium strong base, part of the quaternary ammonium base reacts with the polyol to form the corresponding polyol salt, and the methanol is removed under reduced pressure and heating conditions. The remaining quaternary ammonium base, polyol salt and water constitute a dicationic quaternary ammonium base deep eutectic catalyst.

3. A method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst according to claim 2, characterized in that: In the synthesis of the monoester quaternary ammonium salt, the ditertiary amine structure is (CH3)2NRN(CH3)2, wherein R is selected from an alkyl group, a phenyl group, and an alkyl group containing an ether group, preferably an alkyl group with six or less carbon atoms, such as a methyl group, an ethyl group, and a propyl group; the molecular formula of the dimethyl sulfate is (CH3O)2SO2, and the molar ratio of the ditertiary amine to the dimethyl sulfate is 1:2~1:2.4, wherein the preferred ratio is 1:2.1; the solvent used is anhydrous methanol, and the mass ratio of methanol to the ditertiary amine is 0.9:1~1.2:

1.

4. A method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst according to claim 2, characterized in that: In the synthesis of the monoester-type quaternary ammonium salt of sulfuric acid, the total dripping time of slowly adding dimethyl sulfate is 0.5-2 h, and the preferred dripping time is controlled at about 1 h; the reaction temperature is controlled at 0-25 ° C during the dripping process; after the dripping is completed, the temperature is raised to 40-80 ° C and kept warm for 0.5-2 h, wherein the preferred insulation temperature is 50-60 ° C and the insulation time is 1 h; after the reaction is completed, most of the solvent is removed under normal pressure heating conditions, and the heating temperature is controlled at 70-80 ° C.

5. A method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst according to claim 2, characterized in that: In the hydrolysis of the monosulfate quaternary ammonium salt, the ratio of the amount of water added to the monosulfate quaternary ammonium salt is 5:1~10:1, and the addition method is slow dropwise addition, and the dropwise addition time is controlled within 0.5~2 h; the hydrolysis temperature is controlled to be 120~150 ° C, the hydrolysis time is 0.5~2 h, and the preferred hydrolysis time is 1 h. The water and alcohol evaporated by the reaction are condensed into another container for collection.

6. A method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst according to claim 2, characterized in that: In the ion exchange, the methanol used has a purity of 95% (containing 5% water); the inorganic strong base used is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, preferably sodium hydroxide; the ratio of the inorganic strong base (counted as hydroxide) to the initially added dimethyl sulfate substance is 2:1; the inorganic strong base methanol solution is dripped into the hydrogen sulfate type quaternary ammonium salt methanol solution, and the dripping time is 0.5 to 1 hour.

7. A method for synthesizing a dicationic quaternary ammonium base deep eutectic catalyst according to claim 2, characterized in that: In the ion exchange, after adding an inorganic strong base methanol solution, the temperature is raised to 40-60° C., fully stirred and kept warm for 4-6 hours; after the ion exchange, the ion exchange rate obtained by the barium chloride method is not less than 99%.

8. A novel synthesis method of a dicationic quaternary ammonium base deep eutectic catalyst according to claim 1, characterized in that: In the synthesis of the deep eutectic catalyst, the molar ratio of additional water to quaternary ammonium base is 6:1-8:1; the added polyol is selected from ethylene glycol and glycerol, with ethylene glycol being preferred; the molar ratio of the added polyol to the hydroxide of the quaternary ammonium base is 0.5:1-1:1, and the corresponding molar ratio of the polyol salt to the quaternary ammonium base is 1:1-1:0; the methanol removal temperature is 50-60°C, and the vacuum degree is 0.085-0.095 MPa; the water content of the obtained deep eutectic catalyst is 35%-45%.

9. A method for using a dicationic quaternary ammonium base deep eutectic catalyst in the synthesis of an RT base precursor, characterized in that: The dicationic quaternary ammonium base deep eutectic catalyst, aniline and nitrobenzene are uniformly mixed in proportion and reacted under certain reaction temperature and vacuum conditions to obtain an RT base precursor.

10. The method for using a dicationic quaternary ammonium base deep eutectic catalyst in the synthesis of an RT base precursor according to claim 9, characterized in that: The reaction is carried out under reduced pressure and heating conditions; the molar ratio of the reactants aniline, nitrobenzene, and deep eutectic catalyst (calculated in terms of nitrogen content) is (4-6):1:(1-1.2); the reaction temperature is 70-80°C, the reaction vacuum is 0.085-0.095 MPa, and the reaction time is 4-5 h.

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