A method for preparing a tertiary amine using a secondary amine as a raw material

Abstract

The present invention discloses a method for preparing a tertiary amine starting from a secondary amine. The method includes the steps of reacting a secondary amine with an acid to produce a protic ionic liquid, and reacting the protic ionic liquid with an aldehyde under the action of a reducing agent to produce a tertiary amine. The secondary amine is an aliphatic secondary amine and / or an aromatic secondary amine and / or a cyclic secondary amine, the acid is selected from one or more combinations of an organic carboxylic acid and an inorganic acid, the aldehyde is a monoaldehyde, a dialdehyde or an aldehyde polymer, and the reducing agent is one or more combinations of formic acid, sodium formate, oxalic acid, sodium oxalate and triphenylsilane. The protic ionic liquid in the present invention can play a self-catalytic role, so that the reaction conditions are mild, can be realized without high pressure or hydrogen gas reaction atmosphere, and a safe and environmentally friendly reducing agent can be used while ensuring high purity and high yield of the tertiary amine product.

Description

Technical Field

[0001] The present invention relates to a method for preparing a tertiary amine using a secondary amine as a raw material.

Background Art

[0002] Tertiary amines are widely used in industrial production and daily life, and can be used as fuel additives, raw materials for pesticide production, pharmaceutical synthesis, epoxy resin curing agents, intermediates for polyurethane catalysts, raw materials for the production of quaternary ammonium salts / alkalis, plasticizers, dyes, desulfurizing agents, etc.

[0003] In the traditional synthesis of tertiary amine products, generally a high-pressure fixed-bed reactor is used, and heterogeneous noble metal catalysts such as Pd and Pt supported on a carrier are used. It is also known that the reaction needs to be carried out under hydrogen gas conditions. For example, CN101460445A discloses a method for preparing diisopropylethylamine by aminating diisopropylamine and acetaldehyde using a suspension catalyst Pd / C as a catalyst, but the reaction requires high pressure and hydrogen gas conditions, and the noble metal catalyst is expensive.

[0004] It is also known that a tertiary amine can be produced by reacting a secondary amine with an aldehyde having two or more carbon atoms in the presence of a reducing agent without using a metal catalyst and without using hydrogen gas under normal pressure conditions. For example, Chinese Patent Publication CN101360726A discloses a method for preparing a tertiary amine by dropping a secondary amine into a mixed solution of an aldehyde and an acid. The feature of this method is that the aldehyde and formic acid are first mixed and heated to the reflux temperature, and then the secondary amine is added and reacted. This method has limitations on the addition order of raw materials, and when aldehyde or acid is dropped into the other two raw materials, the reaction yield clearly decreases. After the reaction, it is necessary to add a large amount of alkali (for example, an aqueous NaOH solution) to the reaction system to neutralize the reaction system so that a large amount of wastewater containing organic substances is generated in the reaction.

[0005] It is also known that Chinese Patent Publication No. CN102875385A discloses a method of using paraldehyde as a raw material, employing an acid catalyst for hydrolysis, and then reacting with diisopropylamine and a reducing metal hydride such as sodium borohydride to produce a tertiary amine. This patent does not disclose the purity of the tertiary amine product. At the same time, reducing agents used, such as sodium borohydride, are highly toxic, highly explosive, and sensitive to water, thus not contributing to the progress of the reaction.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a tertiary amine by reacting an improved protic ionic liquid with an aldehyde in view of the drawbacks and deficiencies of the prior art. This method is a homogeneous autocatalytic reaction, does not require high-pressure hydrogen gas and metal catalyst conditions, and can use a safe and environmentally friendly reducing agent, and the reaction material addition process is safer.

Means for Solving the Problems

[0007] To solve the above technical problems, the technical means adopted in the present invention are as follows.

[0008] A method for preparing a tertiary amine using a secondary amine as a raw material, comprising the steps of reacting the secondary amine with an acid to produce a protic ionic liquid, and reacting the protic ionic liquid with an aldehyde under the action of a reducing agent to produce a tertiary amine.

[0009] Furthermore, the number of carbon atoms of the secondary amine is 30 or less, preferably 25 or less, more preferably 20 or less, and / or the secondary amine is an aliphatic secondary amine and / or an aromatic secondary amine and / or a cyclic secondary amine, and / or the acid is selected from one or a combination of organic carboxylic acids and inorganic acids, and / or the aldehyde is a monoaldehyde, a dialdehyde or a polymer of an aldehyde.

[0010] Furthermore, the acid is 1 ~C 3 selected from one or a combination of organic carboxylic acids, hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, and preferably, the acid is selected from one or a combination of formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, carbonic acid, hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid.

[0011] In some embodiments of the present invention, the reducing agent is selected from one or a combination of formic acid, sodium formate, oxalic acid, sodium oxalate and triphenylsilane, and preferably, the reducing agent is selected from formic acid, sodium formate, oxalic acid or sodium oxalate.

[0012] The inventor discovers that a secondary amine and an acid can react under room temperature and atmospheric pressure conditions to generate a protic ionic liquid, the operation is safe and controllable, the molar ratio of the secondary amine to the acid is close to 1, and the consumption of the acid is small. Furthermore, when this protic ionic liquid and an aldehyde are reacted under the action of a reducing agent to generate a tertiary amine, mild reaction conditions for the secondary amine and the aldehyde to react to generate a tertiary amine can be realized, there is no need for high pressure and a hydrogen gas reduction atmosphere in the reaction process, the yield of this reaction is high, the purity of the obtained tertiary amine is high, and a safe and environmentally friendly reducing agent is used in the reaction system. The protic ionic liquid formed in the reaction system can act as a reaction catalyst, and the reaction system of the present invention is a self-catalytic reaction system, and there is no need to add a metal catalyst.

[0013] In some embodiments of the present invention, before the molar ratio of said secondary amine as a raw material for is 0.2 to 1.5, preferably 0.3 to 1.4, and particularly preferably 0.4 to 1.2.

[0014] In some embodiments of the present invention, before the molar ratio of said aldehyde for the protic ionic liquid

[0015] is 0.2 to 5.0, preferably 0.3 to 3.0, and particularly preferably 0.4 to 2.0. before said reducing agent for In some embodiments of the present invention, the molar ratio of

[0016] the protic ionic liquid

[0017] is 1.0 to 5.0, preferably 1.0 to 2.0.

[0018] In some embodiments of the present invention, the step of reacting the protic ionic liquid with an aldehyde under the action of a reducing agent to produce a tertiary amine is carried out at a pressure of 0 to 5.0 MPa, preferably 0 to 3.0 MPa, and particularly preferably 0 to 2.0 MPa.

[0019] In some embodiments of the present invention, the step of reacting the protic ionic liquid with an aldehyde under the action of a reducing agent to produce a tertiary amine is carried out at a temperature of 60 to 200 °C, preferably 120 to 160 °C.

[0020] In some embodiments of the present invention, the method 1) dropping the acid into the secondary amine, or dropping the secondary amine into the acid to form the protic ionic liquid; 2) adding the protic ionic liquid and the reducing agent to a reactor, and adding the aldehyde to the reactor; 3) injecting nitrogen gas until the pressure of the reaction system reaches 0 to 5.0 MPa, heating the temperature to 60 to 200 °C, and reacting for 5 to 300 minutes; 4) after the reaction is completed, purifying the reaction system to obtain the tertiary amine.

[0021] In some embodiments of the present invention, in step 1), the acid is dropped into an aqueous solution of the secondary amine to form the protic ionic liquid.

[0022] In some embodiments of the present invention, in step 1), the acid is dropped into the secondary amine in the form of an aqueous solution of the acid.

[0023] In some embodiments of the present invention, in step 2), the aldehyde can be added to the reactor once, intermittently, or continuously.

[0024] In some embodiments of the present invention, in step 2), the reducing agent can be added to the reactor once, intermittently, or continuously. In some embodiments of the present invention, in step 4), as the purification, atmospheric distillation or vacuum distillation can be performed according to the boiling point of the product.

[0025] In some embodiments of the present invention, as the reactor, a stirring container, an autoclave, a tubular reactor, a microreactor or a packed bubble column, preferably an autoclave, is used.

[0026] Furthermore, the structural formula of the secondary amine is

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0027] The structural formula of the protic ionic liquid is

Chemical formula

[0028] When the aldehyde is selected from a monoaldehyde having the structural formula [Chemical formula] or a polymer of a monoaldehyde having the structural formula [Chemical formula] the reaction formula between the protic ionic liquid and the aldehyde is as shown below [Chemical formula] When the aldehyde is selected from a dialdehyde having the structural formula [Chemical formula] the reaction formula between the protic ionic liquid and the aldehyde is as shown below [Chemical formula]

[0029] The protic ionic liquid first reacts with the aldehyde to generate the corresponding Schiff base, and the Schiff base is prepared and obtained by the reduction with a reducing agent to obtain the tertiary amine.

[0030] In some embodiments of the present invention, the R 1 , R 2 are independently selected from a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a 2-ethylhexyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a phenyl group, a 2-naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 2,4-dimethylphenyl group, a 2,5-dimethylphenyl group, a 2,6-dimethylphenyl group, a 3,4-dimethylphenyl group, a 3,5-dimethylphenyl group, a 2,3,4-trimethylphenyl group, a 2,3,5-trimethylphenyl group, a 2,3,6-trimethylphenyl group, a 2,4,6-trimethylphenyl group, a 2-ethylphenyl group, a 3-ethylphenyl group, a 4-ethylphenyl group, a 2-n-propylphenyl group, a 3-n-propylphenyl group or a 4-n-propylphenyl group.

[0031] In some other embodiments of the present invention, the R 1 , R 2 together with NH form azetidine, pyrrole, piperidine, cyclohexamethyleneimine, morpholine, piperazine or N-methylpiperazine.

[0032] In some embodiments of the present invention, the R 3is selected from H, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, an isohexyl group, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

[0033] In some embodiments of the present invention, the R 4 is selected from a single bond, a methylene group, an ethylidene group, a propylidene group, and a butylidene group.

[0034] In some embodiments of the present invention, the aldehyde is selected from acetaldehyde, paraldehyde, metaaldehyde, propionaldehyde, glycolaldehyde, glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, or adipaldehyde.

[0035] In some embodiments of the present invention, the secondary amine is selected from dimethylamine, diisopropylamine, piperidine, morpholine, or N-methylpiperazine; the aldehyde is selected from acetaldehyde, paraldehyde, metaaldehyde, propionaldehyde, glycolaldehyde, or succinaldehyde; and the tertiary amine is selected from dimethylethylamine, dimethylpropylamine, N,N,N’,N’-tetramethylbutanediamine, diisopropylethylamine, diisopropylethanolamine, N-ethylpiperidine, N-propylmorpholine, N-propylpiperazine, or N,N’-dipropylpiperazine.

[0036] In a particularly preferred embodiment of the present invention, acetaldehyde and dimethylamine react to form dimethylethylamine.

[0037] In a particularly preferred embodiment of the present invention, propionaldehyde and dimethylamine react to form dimethylpropylamine.

[0038] In a particularly preferred embodiment of the present invention, succinaldehyde and dimethylamine react to produce N,N,N’,N’-tetramethylbutanediamine.

[0039] In a particularly preferred embodiment of the present invention, acetaldehyde and diisopropylamine react to produce diisopropylethylamine.

[0040] In a particularly preferred embodiment of the present invention, paraldehyde and diisopropylamine react to produce diisopropylethylamine.

[0041] In a particularly preferred embodiment of the present invention, glycolaldehyde and diisopropylamine react to produce diisopropylethanolamine.

[0042] In a particularly preferred embodiment of the present invention, acetaldehyde and piperidine react to produce N-ethylpiperidine.

[0043] In a particularly preferred embodiment of the present invention, propionaldehyde and morpholine react to produce N-propylmorpholine.

[0044] In a particularly preferred embodiment of the present invention, propionaldehyde and piperazine react to produce N-propylpiperazine.

[0045] In a particularly preferred embodiment of the present invention, propionaldehyde and piperazine react to produce N,N’-dipropylpiperazine.

[0046] In a particularly preferred embodiment of the present invention, acetaldehyde and dicyclohexylamine react to produce N-ethyldicyclohexylamine.

[0047] In a particularly preferred embodiment of the present invention, acetaldehyde and diphenylamine react to produce N-ethyldiphenylamine.

Advantages of the Invention

[0048] Compared with the prior art, the present invention has the following advantages. In a system for producing a tertiary amine using a secondary amine as a raw material, the present invention creatively first adds an acid to react with the secondary amine to generate a protic ionic liquid, and then reacts the protic ionic liquid with an aldehyde to generate a tertiary amine. This protic ionic liquid can achieve self-catalysis so as to ensure high purity and high yield of the tertiary amine product, while the reaction conditions in this reaction system are mild, without the need for high pressure or a hydrogen gas reaction atmosphere, and a mild and safe reducing agent can be used. The tertiary amine product obtained in the present invention reaches a purity of 99% and a yield of 98%. Also, since this reaction is a homogeneous self-catalytic reaction, the production cost is also significantly reduced.

Brief Description of the Drawings

[0049]

Figure 1

Embodiments for Carrying Out the Invention

[0050] The present invention will be further described below with reference to examples. However, the present invention is not limited to the following examples. The implementation conditions adopted in the examples can be further adjusted according to the different requirements of specific uses, and the implementation conditions not specified are general conditions in the industry. The technical features of various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0051] All kinds of raw materials used in the following examples were purchased from Aladdin Reagent Company. Here, dimethylamine is an aqueous solution with a purity of 40%, and diisopropylamine, piperidine, morpholine, ethylamine, dicyclohexylamine, paraaldehyde, glycolaldehyde, succinaldehyde, acetic acid, propionic acid, and malonic acid are aqueous solutions with a purity of 99% or more. Piperazine, diphenylamine, sodium formate, oxalic acid, and sodium oxalate are solids with a purity of 99% or more. Formic acid is a solid with a purity of 98% or more. Hydrochloric acid is an aqueous solution with a purity of 36.5% or more. Phosphoric acid is an aqueous solution with a purity of 85% or more. Acetaldehyde, propionaldehyde, and concentrated sulfuric acid are aqueous solutions with a purity of 98% or more. Concentrated nitric acid is an aqueous solution with a purity of 65% or more.

[0052] Example 1 Synthesis of dimethylethylamine by the reaction of dimethylamine and acetaldehyde

[0053] In a 100 mL autoclave reactor, 15 g of a 40% aqueous solution of dimethylamine was added, and 7.5 g of a formic acid solution was added drop by drop into the reactor and stirred to form a homogeneous solution, preparing and obtaining an aqueous solution of a protic ionic liquid of dimethylamine formate. Then, 10 g of solid sodium formate and 6.5 g of an acetaldehyde solution were added to this aqueous solution of the protic ionic liquid. The reaction vessel was closed, nitrogen gas was injected to increase the pressure to 1 MPa, the temperature was raised to 140 °C, and the reaction was carried out for 120 minutes.

[0054] The mixture of reaction products is rectified and purified, distilled at normal pressure, and the fraction at 34 - 36 °C is collected. The fraction is analyzed for purity by gas chromatography. As the measurement program for using gas chromatography, the separation column is HP - 1, length: 60 m, inner diameter: 0.25 mm, carrier: nitrogen gas, temperature program: 55 °C, then the temperature is raised to 220 °C at a rate of 10 °C per minute, and finally held at 220 °C for 10 minutes. Dimethylethylamine with a purity of 99% is obtained, and the product yield is 95%.

[0055] Example 2 Formation of dimethylpropylamine from dimethylamine and propionaldehyde

[0056] Into a 100 mL autoclave reactor, 15 g of a 40% aqueous solution of dimethylamine is added, and 8 g of acetic acid solution is added drop by drop into the reactor, stirred to form a homogeneous solution, and an aqueous solution of a protic ionic liquid of dimethylamine acetate is prepared and obtained. Then, 10 g of sodium formate is added to this aqueous solution of the protic ionic liquid and 8 g of propionaldehyde solution is added, the reaction vessel is closed, nitrogen gas is injected to increase the pressure to 2 MPa, the temperature is raised to 160 °C, and the reaction is carried out for 120 minutes.

[0057] The mixture of reaction products is rectified and purified, distilled at normal pressure, and the fraction at 70 - 71 °C is collected. The fraction is analyzed for purity by gas chromatography. The method is the same as in Example 1. Dimethylpropylamine with a purity of 99% is obtained, and the product yield is 96%.

[0058] Example 3 Formation of N,N,N’,N’ - tetramethylbutanediamine from dimethylamine and succinaldehyde

[0059] 15 g of a 40% aqueous dimethylamine solution was added to a 100 mL autoclave reactor, and 11 g of a propionic acid solution was added dropwise into the reactor. After stirring to form a homogeneous solution, an aqueous solution of a protic ionic liquid of dimethylamine propionate was prepared and obtained. Subsequently, 13 g of oxalic acid and 5 g of succinaldehyde were added to this aqueous protic ionic liquid solution. The reaction vessel was closed, nitrogen gas was injected to increase the pressure to 2 MPa, the temperature was raised to 160 °C, and the reaction was carried out for 120 minutes.

[0060] The reaction product mixture was rectified and purified, distilled at atmospheric pressure, and the fraction at 166 - 167 °C was collected. The fraction was analyzed for purity by gas chromatography. The method was the same as in Example 1, and N,N,N’,N’-tetramethylbutanediamine with a purity of 99% was obtained, and the product yield was 95%.

[0061] Example 4 Synthesis of diisopropylethylamine by the reaction of diisopropylamine and acetaldehyde

[0062] 15 g of diisopropylamine was added to a 100 mL autoclave reactor, and an aqueous solution containing 15 g of concentrated hydrochloric acid was added dropwise into the reactor. After stirring to form a homogeneous solution, an aqueous solution of a protic ionic liquid of diisopropylamine hydrochloride (the NMR spectrum in DMSO is shown in Figure 1) was prepared and obtained. Subsequently, 10 g of sodium formate and 7 g of acetaldehyde were added to this aqueous protic ionic liquid solution. The reaction vessel was closed, nitrogen gas was injected to increase the pressure to 2 MPa, the temperature was raised to 120 °C, and the reaction was carried out for 30 minutes.

[0063] The reaction product mixture was rectified and purified, distilled at atmospheric pressure, and the fraction at 127 - 128 °C was collected. The fraction was analyzed for purity by gas chromatography. The method was the same as in Example 1, and diisopropylethylamine with a purity of 99% was obtained, and the product yield was 97%.

[0064] Example 5 Synthesis of Diisopropylethylamine by Reaction of Diisopropylamine and Paraaldehyde

[0065] Add 15 g of diisopropylamine to a 100 mL autoclave reactor, add an aqueous solution containing 7 g of formic acid into the reactor, stir to form a homogeneous solution, and prepare and obtain an aqueous solution of a protic ionic liquid of diisopropylamine formate (the NMR spectrum in DMSO is shown in Figure 1). Then, add 7 g of formic acid and 7 g of paraaldehyde to this aqueous solution of the protic ionic liquid, close the reaction vessel, inject nitrogen gas, maintain normal pressure (i.e., the pressure display number is 0 MPa), raise the temperature to 160 °C, and react for 120 minutes.

[0066] After the reaction is completed, the oil layer and the water layer are separated, and the water layer can be recycled and used as it is. Distill at normal pressure and collect the fraction at 127 - 128 °C. The fraction is analyzed for purity by gas chromatography. The method is the same as in Example 1, and diisopropylethylamine with a purity of 99% is obtained, and the product yield is 98%.

[0067] Example 6 Synthesis of Diisopropylethanolamine by Reaction of Diisopropylamine and Glycolaldehyde

[0068] Add 15 g of diisopropylamine to a 100 mL autoclave reactor, add drop by drop an aqueous solution containing 12 g of concentrated sulfuric acid (10% content) into the reactor, stir to form a homogeneous solution, and prepare and obtain an aqueous solution of a protic ionic liquid of diisopropylamine sulfate (the NMR spectrum in DMSO is shown in Figure 1). Then, add 10 g of sodium formate and 9 g of glycolaldehyde to this aqueous solution of the protic ionic liquid, close the reaction vessel, inject nitrogen gas to increase the pressure to 2 MPa, raise the temperature to 120 °C, and react for 30 minutes.

[0069] The mixture of reaction products is rectified and purified, distilled under normal pressure, and the fraction at 187 - 192 °C is collected. The fraction is analyzed for purity by gas chromatography. The method is the same as in Example 1, and diisopropylethanolamine with a purity of 99% is obtained, and the product yield is 94%.

[0070] Example 7 Synthesis of N - ethylpiperidine by reaction of piperidine and acetaldehyde

[0071] 8.5 g of piperidine is added to a 100 mL autoclave reactor, and an aqueous solution containing 10 g of phosphoric acid (content 10%) is added drop by drop into the reactor and stirred to form a homogeneous solution, preparing and obtaining an aqueous solution of a protic ionic liquid of piperidine phosphate. Then, 5.0 g of formic acid and 4.6 g of acetaldehyde are added to this aqueous solution of the protic ionic liquid. The reaction vessel is closed, nitrogen gas is injected to increase the pressure to 2 MPa, the temperature is raised to 160 °C, and the reaction is carried out for 90 minutes.

[0072] The mixture of reaction products is rectified and purified, distilled under normal pressure, and the fraction at 126 - 129 °C is collected. The fraction is analyzed for purity by gas chromatography. The method is the same as in Example 1, and N - ethylpiperidine with a purity of 99% is obtained, and the product yield is 94%.

[0073] Example 8 Synthesis of N - propylmorpholine by reaction of morpholine and propionaldehyde

[0074] 15 g of morpholine is added to a 100 mL autoclave reactor, and 17 g of concentrated hydrochloric acid is added drop by drop into the reactor and stirred to form a homogeneous solution, preparing and obtaining an aqueous solution of a protic ionic liquid of morpholine nitrate. Then, 12 g of sodium formate and 11 g of propionaldehyde are added to this aqueous solution of the protic ionic liquid. The reaction vessel is closed, nitrogen gas is injected, the pressure is increased to 2 MPa, the temperature is raised to 160 °C, and the reaction is carried out for 120 minutes.

[0075] The mixture that is the reaction product is subjected to fractional distillation for purification, distilled under reduced pressure, and the fraction at 67 - 69 °C under a pressure of 30 mmHg is collected. The fraction is analyzed for purity by gas chromatography. The method is the same as in Example 1, and N-propylmorpholine with a purity of 99% is obtained, and the product yield is 90%.

[0076] Example 9 Synthesis of N-propylpiperazine by the reaction of piperazine and propionaldehyde

[0077] 15 g of piperazine is added to a 100 mL autoclave reactor, and an aqueous solution containing 18 g of concentrated nitric acid (10% content) is added dropwise into the reactor and stirred to form a homogeneous solution, preparing and obtaining an aqueous solution of a protic ionic liquid of piperazine nitrate. Then, 12 g of sodium formate is added to this aqueous solution of the protic ionic liquid, the reaction vessel is closed, nitrogen gas is injected to increase the pressure to 2 MPa, the temperature is raised to 160 °C, and 10 g of propionaldehyde is injected within 1 hour and reacted for 120 minutes.

[0078] The mixture that is the reaction product is subjected to fractional distillation for purification, distilled under reduced pressure, and the fraction at 61 - 64 °C under a pressure of 15 mmHg is collected. The fraction is analyzed for purity by gas chromatography. The method is the same as in Example 1, and N-propylpiperazine with a purity of 99% is obtained, and the product yield is 91%.

[0079] Example 10 Synthesis of N,N'-dipropylpiperazine by the reaction of piperazine and propionaldehyde

[0080] 15 g of piperazine was added to a 100 mL autoclave reactor, and an aqueous solution containing 18 g of concentrated nitric acid (10% content) was added dropwise into the reactor, followed by stirring to form a homogeneous solution, preparing and obtaining an aqueous solution of a protic ionic liquid of piperazine nitrate. Then, 24 g of sodium formate and 20 g of propionaldehyde were added to this aqueous solution of the protic ionic liquid. The reaction vessel was closed, nitrogen gas was injected to increase the pressure to 2 MPa, the temperature was raised to 160 °C, and the reaction was carried out for 120 minutes.

[0081] The reaction product mixture was rectified and purified, distilled under reduced pressure, and the fraction at 84 - 88 °C under a pressure of 12 mmHg was collected. The fraction was analyzed for purity by gas chromatography. The method was the same as in Example 1, and N,N'-dipropylpiperazine with a purity of 99% was obtained, and the product yield was 90%.

[0082] Example 11 Synthesis of N,N,N',N'-tetramethylbutanediamine from dimethylamine and succinaldehyde

[0083] 15 g of a 40% aqueous solution of dimethylamine was added to a 100 mL autoclave reactor, and 14 g of an aqueous solution of malonic acid was added dropwise into the reactor, followed by stirring to form a homogeneous solution, preparing and obtaining an aqueous solution of a protic ionic liquid of dimethylamine malonate. Then, 13 g of oxalic acid was added to this aqueous solution of the protic ionic liquid. The reaction vessel was closed, nitrogen gas was injected to increase the pressure to 2 MPa, the temperature was raised to 160 °C, and the reaction was carried out for 120 minutes. Among them, 5 g of succinaldehyde was uniformly injected into the reaction system within the first 60 minutes.

[0084] The reaction product mixture was rectified and purified, distilled at atmospheric pressure, and the fraction at 166 - 167 °C was collected. The fraction was analyzed for purity by gas chromatography. The method was the same as in Example 1, and N,N,N',N'-tetramethylbutanediamine with a purity of 99% was obtained, and the product yield was 96%.

[0085] Example 12 Synthesis of N-ethyldicyclohexylamine from acetaldehyde and dicyclohexylamine

[0086] Add 24 g of an aqueous solution of dicyclohexylamine to a 100 mL autoclave reactor, add 14 g of concentrated hydrochloric acid drop by drop into the reactor, stir to form a homogeneous solution, prepare and obtain an aqueous solution of a protic ionic liquid of dicyclohexylamine hydrochloride. Then, add 10 g of sodium formate and 7 g of acetaldehyde to this aqueous protic ionic liquid solution, close the reaction vessel, inject nitrogen gas to increase the pressure to 2 MPa, raise the temperature to 160 °C, and react for 120 minutes.

[0087] The reaction product mixture is rectified and purified, distilled under reduced pressure, and the fraction at 137 - 138 °C at a pressure of 14 mmHg is collected. The fraction is analyzed for purity by gas chromatography, and the method is the same as in Example 1. N-ethyldicyclohexylamine with a purity of 99% is obtained, and the product yield is 94%.

[0088] Example 13 Synthesis of N-ethyldiphenylamine from acetaldehyde and diphenylamine

[0089] Add 23 g of solid diphenylamine to a 100 mL autoclave reactor, add drop by drop an aqueous solution (10% content) containing 12 g of concentrated sulfuric acid into the reactor, stir to form a homogeneous solution, prepare and obtain an aqueous solution of a protic ionic liquid of diphenylamine sulfate. Then, add 15 g of oxalic acid and 6 g of acetaldehyde to this aqueous protic ionic liquid solution, close the reaction vessel, inject nitrogen gas to increase the pressure to 2 MPa, raise the temperature to 160 °C, and react for 120 minutes.

[0090] The mixture of reaction products was rectified and purified under reduced pressure, and the fraction at 150 - 152 °C under a pressure of 14 mmHg was collected. The fraction was analyzed for purity by gas chromatography. The method was the same as in Example 1, and N - ethyldiphenylamine with a purity of 99% was obtained, and the product yield was 92%.

[0091] Example 14 Synthesis of triethylamine from diethylamine and acetaldehyde

[0092] 10 g of diethylamine was added to a 100 mL autoclave reactor. Then, 4.5 g of formic acid was added dropwise to prepare and obtain an aqueous solution of a protic ionic liquid of diethylamine formate. Then, 19 g of solid sodium oxalate and 6.5 g of acetaldehyde were added to this aqueous solution of the protic ionic liquid. The reaction vessel was closed, nitrogen gas was injected to increase the pressure to 2 MPa, the temperature was raised to 120 °C, and the reaction was carried out for 120 minutes.

[0093] After the reaction was completed, the gas remaining in the reactor was removed, and the mixture of reaction products was analyzed by gas chromatography. The gas chromatography was the same as in Example 1.

[0094] As a result of gas chromatography analysis, the reaction system contained tri ethylamine, that is, it was shown that ethylamine was generated from di ethylamine and acetaldehyde due to the reducing action of sodium formate. tri The mixture of reaction products was rectified and purified, distilled at normal pressure, and the fraction at 89 - 91 °C was collected. Triethylamine with a purity of 99% was obtained, and the product yield was 94%.

[0095] Comparative Example 1 Reaction of diisopropylamine and acetaldehyde

[0096] Add 15 g of diisopropylamine to a 100 mL autoclave reactor, then add 11 g of sodium formate and 7 g of acetaldehyde. Close the reaction vessel, inject nitrogen gas to increase the pressure to 2 MPa, raise the temperature to 120 °C, and react for 120 minutes.

[0097] After the reaction is completed, remove the gas remaining in the reactor and analyze the reaction product mixture by gas chromatography. The gas chromatography is the same as in Example 1. According to the gas chromatography analysis, only the sample peaks of acetaldehyde and diisopropylamine are present in the reaction product mixture, indicating that diisopropylethylamine is not produced in the reactor. Comparing this Comparative Example 1 with Example 4, it can be seen that a protic ionic liquid is formed from the acid and secondary amine added in the present invention. Such a protic ionic liquid reacts with aldehyde to form a Schiff base and is then easily reduced to a tertiary amine by a reducing agent. When no acid is added, it is known that a protic ionic liquid cannot be formed in the system and the secondary amine and aldehyde cannot react.

[0098] Comparative Example 2 Synthesis of diethylamine by the reaction of ethylamine and acetaldehyde

[0099] Add 7 g of ethylamine to a 100 mL autoclave reactor, then add 23 g of solid sodium formate and 14 g of acetaldehyde. Close the reaction vessel, inject nitrogen gas to increase the pressure to 2 MPa, raise the temperature to 120 °C, and react for 120 minutes.

[0100] After the reaction is completed, remove the gas remaining in the reactor and analyze the reaction product mixture by gas chromatography. The gas chromatography is the same as in Example 1.

[0101] As a result of gas chromatography analysis, it was shown that the reaction system contained diethylamine, that is, diethylamine was generated from ethylamine and acetaldehyde by the reducing action of sodium formate. The reaction product mixture was rectified and purified, distilled at normal pressure, and the fraction at 55-56 °C was collected to obtain diethylamine with a purity of 99%, and the product yield was 55%.

[0102] Generally, the reaction in which a primary amine and an aldehyde react to form a secondary amine is easier to carry out than the reaction in which the corresponding secondary amine and an aldehyde react to form a tertiary amine, and it is shown that the yield of the reaction in which a primary amine and an aldehyde react to form a secondary amine is higher than the yield of the reaction in which a tertiary amine is formed using the corresponding secondary amine as a raw material. On the other hand, Comparative Example 2 is a primary amine ethyl The reaction in which an amine and acetaldehyde react to form a secondary amine, diethylamine, has a yield that is clearly lower than the yield of the reaction in which the diethylamine of the present invention first forms a protic ionic liquid of diethylamine formate with formic acid and then this ionic liquid reacts with acetaldehyde and is reduced to form a tertiary amine, triethylamine. In the present invention, when a protic ionic liquid and an aldehyde react and are reduced to form a tertiary amine, it is shown that the protic ionic liquid not only participates in the reaction itself but also has a certain catalytic effect on the reaction.

[0103] The above examples are only for explaining the technical idea and features of the present invention, and for the purpose that those skilled in the art of this technology can understand the content of the present invention and implement it accordingly, but the protection scope of the present invention cannot be limited thereby. Any equivalent changes or modifications made substantially according to the idea of the present invention should be included in the protection scope of the present invention.

[0104] Neither the endpoints of the ranges disclosed in this specification nor any of the values are limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint value of each range and a single point value, and between single point values, one or more numerical ranges can be obtained by combining them with each other, and these numerical ranges should be regarded as specifically disclosed in this specification.

Claims

1. reacting a secondary amine with an acid to form a protic ionic liquid, and reacting the protic ionic liquid with an aldehyde in the presence of a reducing agent to form a tertiary amine; A method for preparing a tertiary amine using a secondary amine as a raw material, characterized in that; The structural formula of the secondary amine is 【Chemical 1】 wherein R1 and R2 are independently selected from an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a sec-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, an isohexyl group, a sec-hexyl group, an isoheptyl group, a sec-heptyl group, an isooctyl group, a sec-octyl group, a 2-ethylhexyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a 2-naphthyl group, a 2,3,4-trimethylphenyl group, a 2,3,5-trimethylphenyl group, a 2,3,6-trimethylphenyl group, a 2,4,6-trimethylphenyl group, a 2-ethylphenyl group, a 3-ethylphenyl group, a 4-ethylphenyl group, a 2-n-propylphenyl group, a 3-n-propylphenyl group, a 4-n-propylphenyl group, or R1 and R2 together with NH form a pyrrole, a piperidine, a morpholine, a piperazine, an N-methylpiperazine, a cyclohexamethyleneimine or an azetidine; The aldehyde is selected from a monoaldehyde having a structural formula of [Chemical 2] a polymer of a monoaldehyde having a structural formula of 【Chemical Formula 3】 or a dialdehyde having a structural formula of 【Chemical Formula 4】 wherein R3 is selected from a C1-C6 alkyl group and a C1-C6 alkyl group substituted with a hydroxyl group, and R4 is selected from a single bond and a C1-C4 alkylidene group; The molar ratio of the secondary amine to the acid is 0.4 to 1.2; The molar ratio of the aldehyde to the protic ionic liquid is 0.3 to 3.0; The molar ratio of the reducing agent to the protic ionic liquid is 1.0 to 2.0; The reducing agent is selected from one or a combination of formic acid, sodium formate, oxalic acid, sodium oxalate and triphenylsilane; The method comprises: 1) dropping the acid into the secondary amine or dropping the secondary amine into the acid to form the protic ionic liquid; 2) adding the protic ionic liquid and the reducing agent to the reactor, and adding the aldehyde to the reactor; 3) injecting nitrogen gas until the pressure of the reaction system reaches 2 to 5.0 MPa, heating the temperature to 60 to 200 °C, and reacting for 5 to 300 minutes; 4) after the reaction is completed, purifying the reaction system to obtain the tertiary amine; In step 4), the purification is atmospheric distillation or vacuum distillation. A method for preparing a tertiary amine using a secondary amine as a raw material. **Claim 2**: The acid is selected from one or a combination of organic carboxylic acids and inorganic acids. A method for preparing a tertiary amine using a secondary amine as a raw material according to claim 1, characterized in that. **Claim 3** The acid is selected from one or a combination of organic carboxylic acids having C １ to C ３ , hydrochloric acid, carbonic acid, sulfuric acid, phosphoric acid, and nitric acid A method for preparing a tertiary amine using a secondary amine as a raw material according to claim 1, characterized in that. **Claim 4**: The acid is selected from one or a combination of formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, carbonic acid, hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid. A method for preparing a tertiary amine using a secondary amine as a raw material according to claim 3, characterized in that. **Claim 5**: The reducing agent is selected from formic acid, sodium formate, oxalic acid, or sodium oxalate. A method for preparing a tertiary amine using a secondary amine as a raw material according to claim 1, characterized in that. **Claim 6**: The molar ratio of the aldehyde to the protic ionic liquid is 0.4 to 2.

0. A method for preparing a tertiary amine using a secondary amine as a raw material according to claim 1, characterized in that. **Claim 7** The step of reacting the secondary amine with an acid to generate a protic ionic liquid is carried out at room temperature and atmospheric pressure. A method for preparing a tertiary amine using a secondary amine as a raw material according to claim 1, characterized in that. **Claim 8**: The step of reacting the protic ionic liquid and the aldehyde under the action of a reducing agent to generate a tertiary amine is carried out at a temperature of 120 to 160 °C, and / or the reaction time of the protic ionic liquid and the aldehyde under the action of a reducing agent is 30 to 120 minutes. A method for preparing a tertiary amine using a secondary amine as a raw material according to claim 1, characterized in that. **Claim 9** In step 1), the acid is dropped into an aqueous solution of the secondary amine to form the protic ionic liquid, and / or in step 1), the acid is dropped into the secondary amine in the form of an aqueous solution of the acid, and / or in step 2), the aldehyde is added to the reactor once, intermittently, or continuously, and / or in step 2), the reducing agent is added to the reactor once, intermittently, or continuously. A method for preparing a tertiary amine using the secondary amine according to claim 1 as a raw material, characterized by the above.

10. The structural formula of the protic ionic liquid is 【Chemical Formula 5】 and n is selected from 1, 2 or 3, [X] ｎ- is C １ to C ３ organic carboxyl, CO ３ ２- HCO ３ - Cl - NO ３ - SO ４ ２- PO ４ ３－ HPO ４ ２- or H ２ PO ４－ selected from A method for preparing a tertiary amine using the secondary amine according to any one of claims 1 to 9 as a raw material, characterized by the above.

11. The R ３ is selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, an isohexyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, and / or the R ４ is selected from a single bond, a methylene group, an ethylidene group, a propylidene group, a butylidene group, and / or the aldehyde is selected from acetaldehyde, paraldehyde, metaaldehyde, propionaldehyde, glycolaldehyde, glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde or adipaldehyde A method for preparing a tertiary amine using the secondary amine according to claim 1 as a raw material, characterized by the above.

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