Method for preparing tertiary amine from secondary amine

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 from a secondary amine. [Background technology]

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

[0003] It is known that the traditional synthesis of tertiary amine products generally uses high-pressure fixed-bed reactors, uses heterogeneous precious metal catalysts such as Pd, Pt, etc., which are mounted on carriers, and also requires the reaction to be carried out under hydrogen gas conditions.For example, CN101460445A discloses a method for preparing diisopropylamine by amination reaction of diisopropylamine and acetaldehyde using suspended catalyst Pd / C as catalyst, but the reaction requires high pressure and hydrogen gas conditions, and the precious metal catalyst is expensive.

[0004] It is also known that a secondary amine and an aldehyde having two or more carbon atoms are reacted in the presence of a reducing agent to produce a tertiary amine without using a metal catalyst or hydrogen gas under normal pressure conditions. For example, China 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, and the characteristic of this method is that an aldehyde and formic acid are first mixed and heated to a reflux temperature, and then a secondary amine is added to react. This method has restrictions on the order of addition of raw materials, and when an aldehyde or an acid is dropped into the other two raw materials, the reaction yield is obviously reduced. After the reaction is completed, a large amount of alkali (e.g., NaOH aqueous solution) needs to be added to the reaction system to neutralize the reaction system, so that the reaction produces a large amount of organic-containing wastewater.

[0005] It is also known that the Chinese laid open patent CN102875385A discloses a method for producing a tertiary amine by hydrolyzing paraldehyde using an acid catalyst and then reacting it with diisopropylamine and a reducing metal hydride, such as sodium borohydride, using paraldehyde as a raw material. This patent does not disclose the purity of the tertiary amine product, but at the same time, the reducing agent used, such as sodium borohydride, is highly toxic, highly explosive, and sensitive to water, and therefore does not contribute to the progress of the reaction. Summary of the Invention [Problem to be solved by the invention]

[0006] The technical problem to be solved by the present invention is to address the shortcomings and deficiencies of the prior art by providing an improved method for preparing a tertiary amine by reacting a protic ionic liquid with an aldehyde, which 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 process of adding reactants is safer. [Means for solving the problem]

[0007] In order 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 from a secondary amine as a raw material includes the steps of: reacting the secondary amine as a raw material with an acid to produce a protic ionic liquid; and reacting the protic ionic liquid with an aldehyde in the presence of a reducing agent to produce a tertiary amine.

[0009] Furthermore, the number of carbon atoms in 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 more combinations of organic carboxylic acids, inorganic acids, and / or the aldehyde is a monoaldehyde, dialdehyde or polymer of aldehydes.

[0010] Further, the acid is selected from one or a combination of a C1 to C3 organic carboxylic acid, hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and preferably, the acid is selected from one or a combination of a 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 invention, the reducing agent is selected from a combination of one or more of formic acid, sodium formate, oxalic acid, sodium oxalate, and triphenylsilane, preferably, the reducing agent is selected from formic acid, sodium formate, oxalic acid, or sodium oxalate.

[0012] The present inventors have found that a secondary amine and an acid can react under room temperature and normal pressure conditions to produce 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 the protic ionic liquid and an aldehyde are reacted with a reducing agent to produce a tertiary amine, a mild reaction condition can be realized in which the secondary amine and the aldehyde react to produce a tertiary amine, and the reaction process does not require high pressure or a hydrogen gas reducing atmosphere, and the yield of the 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-catalyzed reaction system, and no metal catalyst needs to be added.

[0013] In some embodiments of the present invention, the molar ratio of the secondary amine to the acid as a raw material 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, the molar ratio of the aldehyde to the protic ionic liquid is from 0.2 to 5.0, preferably from 0.3 to 3.0, and particularly preferably from 0.4 to 2.0.

[0015] In some embodiments of the present invention, the molar ratio of the reducing agent to the protic ionic liquid is from 1.0 to 5.0, preferably from 1.0 to 2.0.

[0016] In some embodiments of the present invention, the step of reacting the secondary amine with an acid to produce a protic ionic liquid is carried out at room temperature and atmospheric pressure.

[0017] In some embodiments of the present invention, the step of reacting the protic ionic liquid with an aldehyde by 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.

[0018] In some embodiments of the present invention, the step of reacting the protic ionic liquid with an aldehyde in the presence 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.

[0019] In some embodiments of the present invention, the time for which the protic ionic liquid and the aldehyde are reacted with the action of a reducing agent is 5 to 300 minutes, preferably 30 to 120 minutes.

[0020] In some embodiments of the invention, the method further comprises: 1) adding the acid dropwise to the secondary amine, or vice versa, 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 becomes 0 to 5.0 MPa, heating the reaction system 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 added dropwise to 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 added dropwise to 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 is added to the reactor once, intermittently, or continuously.

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

[0025] In some embodiments of the invention, the reactor is a stirred vessel, an autoclave, a tubular reactor, a microreactor or a packed bubble column, preferably an autoclave.

[0026] Furthermore, the structural formula of the secondary amine is [ka] wherein R1 and R2 are independently selected from a C1-C8 alkyl group, a C4-C8 cyclic alkyl group, an aryl group, or a C7-C9 alkaryl group; or R1 and R2 together with NH form a C3-C7 ring; and / or the aldehyde has the structural formula [ka] A monoaldehyde having the structural formula [ka] or a polymer of a monoaldehyde having the structural formula [ka] R3 is selected from H, a C1-C6 alkyl group, and a hydroxyl group-substituted C1-C6 alkyl group; and R4 is selected from a single bond or a C1-C4 alkylidene group.

[0027] The structural formula of the protic ionic liquid is [ka] R1 and R2 are independently selected from a C1 to C8 alkyl group, a C4 to C8 cyclic alkyl group, an aryl group, or a C7 to C9 alkaryl group, or R1 and R2 together with N form a C3 to C7 ring, n is selected from 1, 2, or 3; [X] n- is an organic carboxyl of C1 to C3, CO3 2- , HCO3 - , Cl - , NO3 - , SO4 2- , PO4 3- , HPO4 2- or H2PO4 - is selected from.

[0028] The aldehyde has the structural formula [ka] A monoaldehyde having the structural formula [ka] In the case where the protic ionic liquid is selected from a polymer of a monoaldehyde, the reaction between the protic ionic liquid and the aldehyde is as shown below: [ka] The aldehyde has the structural formula [ka] In the case where the dialdehyde is selected from the group consisting of dialdehydes represented by the formula: [ka]

[0029] The protic ionic liquid first reacts with the aldehyde to generate the corresponding Schiff base, which is then reduced with a reducing agent to prepare the tertiary amine.

[0030] In some embodiments of the present invention, R1 and R2 are independently selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, n-hexyl, isohexyl, sec-hexyl, n-heptyl, isoheptyl, sec-heptyl, n-octyl, isooctyl, sec-octyl, 2-ethylhexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclohex ... The group is selected from octyl, phenyl, 2-naphthyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl, 2,3,4-trimethylphenyl, 2,3,5-trimethylphenyl, 2,3,6-trimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-n-propylphenyl, 3-n-propylphenyl, and 4-n-propylphenyl.

[0031] In some other embodiments of the present invention, R1 and R2 together with NH form azetidine, pyrrole, piperidine, cyclohexamethyleneimine, morpholine, piperazine, or N-methylpiperazine.

[0032] In some embodiments of the invention, R3 is selected from H, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, isohexyl, hydroxymethyl, hydroxyethyl, and hydroxypropyl.

[0033] In some embodiments of the present invention, R4 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 invention, the aldehyde is selected from acetaldehyde, paraldehyde, metaldehyde, propionaldehyde, glycolaldehyde, glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, or adipaldehyde.

[0035] In some embodiments of the invention, the secondary amine is selected from dimethylamine, diisopropylamine, piperidine, morpholine, or N-methylpiperazine; the aldehyde is selected from acetaldehyde, paraldehyde, metaldehyde, 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 one particularly preferred embodiment of the invention, acetaldehyde and dimethylamine are reacted to produce dimethylethylamine.

[0037] In one particularly preferred embodiment of the invention, propionaldehyde and dimethylamine are reacted to produce dimethylpropylamine.

[0038] In one particularly preferred embodiment of the invention, succinaldehyde and dimethylamine are reacted to produce N,N,N',N'-tetramethylbutanediamine.

[0039] In one particularly preferred embodiment of the invention, acetaldehyde and diisopropylamine are reacted to produce diisopropylethylamine.

[0040] In one particularly preferred embodiment of the invention, paraldehyde and diisopropylamine are reacted to produce diisopropylethylamine.

[0041] In one particularly preferred embodiment of the present invention, glycolaldehyde and diisopropylamine are reacted to produce diisopropylethanolamine.

[0042] In one particularly preferred embodiment of the invention, acetaldehyde and piperidine are reacted to produce N-ethylpiperidine.

[0043] In one particularly preferred embodiment of the invention, propionaldehyde and morpholine are reacted to produce N-propylmorpholine.

[0044] In one particularly preferred embodiment of the invention, propionaldehyde and piperazine are reacted to produce N-propylpiperazine.

[0045] In one particularly preferred embodiment of the invention, propionaldehyde and piperazine are reacted to produce N,N'-dipropylpiperazine.

[0046] In one particularly preferred embodiment of the invention, acetaldehyde and dicyclohexylamine are reacted to produce N-ethyldicyclohexylamine.

[0047] In one particularly preferred embodiment of the invention, acetaldehyde and diphenylamine are reacted to produce N-ethyldiphenylamine. Effect of the Invention

[0048] Compared with the prior art, the present invention has the following advantages: The present invention is a system for producing tertiary amines using secondary amines as raw materials, which creatively adds an acid to react with the secondary amines to produce protic ionic liquid, and then reacts the protic ionic liquid with an aldehyde to produce tertiary amines, and the protic ionic liquid can play an autocatalytic role, so as to ensure high purity and high yield of the tertiary amine products, while realizing that the reaction conditions in the reaction system are mild, no high pressure or hydrogen gas reaction atmosphere is required, and a mild and safe reducing agent can be used. The tertiary amine products obtained by the present invention have a purity of 99% and a yield of 98%. In addition, the reaction is a homogeneous autocatalytic reaction, so that the production cost is greatly reduced. [Brief description of the drawings]

[0049] [Figure 1] NMR spectra of diisopropylamine and diisopropylamine formate with acid, hydrochloric acid, and sulfuric acid to form the corresponding protic ionic liquids. Here, diisopropylamine: δH(DMSO) 0.93(d,12H), 2.80(m,2H), 3.32(s,2H). Diisopropylamine formate protic ionic liquid: δH(DMSO) 1.18(d,12H), 3.31(m,2H), 8.80(s,1H). Diisopropylamine sulfate protic ionic liquid: δH(DMSO) 1.22(d,12H), 3.34(m,2H), 8.13(s,2H). Diisopropylamine hydrochloride protic ionic liquid: δH(DMSO) 1.25(d,12H), 3.31(m,2H), 8.89(s,2H). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 different requirements of specific use, and the implementation conditions not specified are general conditions in the industry. The technical features according to various embodiments of the present invention can be combined with each other as long as they are not contradictory to each other.

[0051] The raw materials used in the following examples are all purchased from Aladdin Reagent Company, where dimethylamine is an aqueous solution with a purity of 40%, diisopropylamine, piperidine, morpholine, ethylamine, dicyclohexylamine, paraldehyde, 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, and concentrated nitric acid is an aqueous solution with a purity of 65% or more.

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

[0053] In a 100mL autoclave reactor, add 15g of 40% dimethylamine aqueous solution, add 7.5g of formic acid solution dropwise into the reactor, stir to form a uniform solution, prepare and obtain an aqueous solution of protic ionic liquid of dimethylamine formate, then add 10g of sodium formate solid and 6.5g of acetaldehyde solution to this aqueous solution of protic ionic liquid, close the reaction vessel, inject nitrogen gas to increase the pressure to 1MPa, raise the temperature to 140℃, and react for 120 minutes.

[0054] The reaction product mixture is purified by rectification and distillation at normal pressure, and the fraction at 34-36°C is collected. The fraction is analyzed for purity by gas chromatography. The measurement program used for gas chromatography is separation column HP-1, length: 60m, inner diameter: 0.25mm, carrier: nitrogen gas, temperature program: 55°C, and then heated to 220°C at 10°C / min, and finally maintained 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] Add 15g of 40% dimethylamine aqueous solution to a 100mL autoclave reactor, add 8g of acetic acid solution dropwise into the reactor, and stir to form a homogeneous solution to prepare and obtain an aqueous solution of protic ionic liquid of dimethylamine acetate, then add 10g of sodium formate solution and 8g of propionaldehyde solution to this aqueous solution of protic ionic liquid, close the reaction vessel, inject nitrogen gas to increase the pressure to 2MPa, raise the temperature to 160℃, and react for 120 minutes.

[0057] The reaction product mixture is purified by rectification and distilled at normal pressure, and the fraction at 70-71°C is collected. The fraction is subjected to purity analysis by gas chromatography, and the method is the same as that 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] In a 100mL autoclave reactor, add 15g of 40% dimethylamine aqueous solution, add 11g of propionic acid solution drop by drop into the reactor, stir to form a uniform solution, prepare and obtain an aqueous solution of protic ionic liquid of dimethylamine propionate, then add 13g of oxalic acid and 5g of succinaldehyde to this aqueous solution of protic ionic liquid, close the reactor, inject nitrogen gas to increase the pressure to 2MPa, raise the temperature to 160℃, and react for 120 minutes.

[0060] The reaction product mixture is purified by rectification and distilled at normal pressure, and the fraction at 166-167°C is collected. The fraction is subjected to purity analysis by gas chromatography, and the method is the same as that in Example 1. N,N,N',N'-tetramethylbutanediamine with a purity of 99% is obtained, and the product yield is 95%.

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

[0062] Add 15 g of diisopropylamine to a 100 mL autoclave reactor, add dropwise an aqueous solution containing 15 g of concentrated hydrochloric acid into the reactor, and stir to form a homogeneous solution. An aqueous solution of diisopropylamine hydrochloride in a protic ionic liquid (the NMR spectrum in DMSO is shown in Figure 1) is prepared and obtained. 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 120°C, and react for 30 minutes.

[0063] The reaction product mixture is purified by rectification and distilled at normal pressure, and the fraction at 127-128°C is collected. The fraction is subjected to purity analysis by gas chromatography, and the method is the same as that in Example 1. Diisopropylethylamine with a purity of 99% is obtained, and the product yield is 97%.

[0064] Example 5 Synthesis of diisopropylethylamine by reaction of diisopropylamine and paraldehyde.

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

[0066] After the reaction is completed, the oil layer and the aqueous layer are separated, and the aqueous layer can be recycled as it is. Distillation is performed at normal pressure to collect the fraction at 127-128°C, and the fraction is subjected to purity analysis by gas chromatography. The method is the same as that in Example 1. 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 15g of diisopropylamine to a 100mL autoclave reactor, add 12g of concentrated sulfuric acid (10% content) dropwise into the reactor, and stir to form a homogeneous solution. Prepare and obtain an aqueous solution of protic ionic liquid of diisopropylamine sulfate (NMR spectrum in DMSO is shown in Figure 1). Then, add 10g of sodium formate and 9g of glycolaldehyde to this aqueous solution of protic ionic liquid, close the reaction vessel, inject nitrogen gas to increase the pressure to 2MPa, and heat the temperature to 120℃, and react for 30 minutes.

[0069] The reaction product mixture is purified by rectification and distilled at normal pressure, and the fraction at 187-192°C is collected. The fraction is subjected to purity analysis by gas chromatography, and the method is the same as that in Example 1. Diisopropylethanolamine with a purity of 99% is obtained, and the product yield is 94%.

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

[0071] Add 8.5g of piperidine to a 100mL autoclave reactor, add 10g of an aqueous solution containing phosphoric acid (10% content) dropwise into the reactor, and stir to form a homogeneous solution to prepare and obtain an aqueous solution of protic ionic liquid of piperidine phosphate. Then, add 5.0g of formic acid and 4.6g of acetaldehyde to this aqueous solution of protic ionic liquid, close the reaction vessel, inject nitrogen gas to increase the pressure to 2MPa, raise the temperature to 160℃, and react for 90 minutes.

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

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

[0074] Add 15g of morpholine to a 100mL autoclave reactor, add 17g of concentrated hydrochloric acid dropwise into the reactor, and stir to form a homogeneous solution to prepare and obtain an aqueous solution of protic ionic liquid of morpholine nitrate. Then add 12g of sodium formate and 11g of propionaldehyde to the aqueous solution of protic ionic liquid, close the reactor, inject nitrogen gas, increase the pressure to 2MPa, and raise the temperature to 160℃, and react for 120 minutes.

[0075] The reaction product mixture is purified by rectification and distillation under reduced pressure, and the fraction at 67-69°C under 30mmHg pressure is collected, and the fraction is subjected to purity analysis 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] Add 15g of piperazine to a 100mL autoclave reactor, add 18g of concentrated nitric acid (10% content) dropwise into the reactor, and stir to form a homogeneous solution to prepare and obtain an aqueous solution of protic ionic liquid of piperazine nitrate. Then add 12g of sodium formate to this aqueous protic ionic liquid solution, close the reaction vessel, inject nitrogen gas to increase the pressure to 2MPa, and within 1 hour of heating to 160°C, inject 10g of propionaldehyde and react for 120 minutes.

[0078] The reaction product mixture is purified by rectification and distillation under reduced pressure, and the fraction at 61-64°C under 15mmHg pressure is collected, and the fraction is subjected to purity analysis 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] Add 15g of piperazine to a 100mL autoclave reactor, add 18g of concentrated nitric acid (10% content) dropwise into the reactor, stir to form a homogeneous solution, prepare and obtain an aqueous solution of protic ionic liquid of piperazine nitrate, then add 24g of sodium formate and 20g of propionaldehyde to the aqueous solution of protic ionic liquid, close the reaction vessel, inject nitrogen gas to increase the pressure to 2MPa, raise the temperature to 160℃, and react for 120 minutes.

[0081] The reaction product mixture is purified by rectification and distillation under reduced pressure, and the fraction at 84-88°C under 12mmHg pressure is collected. The fraction is subjected to purity analysis by gas chromatography, and the method is the same as that in Example 1. N,N'-dipropylpiperazine with a purity of 99% is obtained, and the product yield is 90%.

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

[0083] In a 100mL autoclave reactor, add 15g of 40% dimethylamine aqueous solution, add 14g of malonic acid aqueous solution dropwise into the reactor, stir to form a uniform solution, prepare and obtain an aqueous solution of protic ionic liquid of dimethylamine malonate, then add 13g of oxalic acid to the aqueous protic ionic liquid solution, close the reactor, inject nitrogen gas to increase the pressure to 2MPa, raise the temperature to 160℃, and react for 120 minutes, of which 5g of succinaldehyde is uniformly injected into the reaction system in the previous 60 minutes.

[0084] The reaction product mixture is purified by rectification and distilled at normal pressure, and the fraction at 166-167°C is collected. The fraction is subjected to purity analysis by gas chromatography, and the method is the same as that in Example 1. N,N,N',N'-tetramethylbutanediamine with a purity of 99% is obtained, and the product yield is 96%.

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

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

[0087] The reaction product mixture is purified by rectification and distillation under reduced pressure, and the fraction at 137-138°C under 14mmHg pressure is collected. The fraction is subjected to purity analysis 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 23g of diphenylamine solid to a 100mL autoclave reactor, add 12g of concentrated sulfuric acid (10% content) dropwise into the reactor, and stir to form a homogeneous solution to obtain an aqueous solution of diphenylamine sulfate protic ionic liquid. Then add 15g of oxalic acid and 6g of acetaldehyde to the aqueous solution of protic ionic liquid, close the reactor, inject nitrogen gas to increase the pressure to 2MPa, and heat the temperature to 160℃, and react for 120 minutes.

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

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

[0092] Add 10 g of diethylamine to a 100 mL autoclave reactor, then drop 4.5 g of formic acid to prepare and obtain an aqueous solution of diethylamine formate and a protic ionic liquid. Then add 19 g of solid sodium oxalate and 6.5 g of acetaldehyde to this aqueous solution of 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 120 minutes.

[0093] After the reaction is completed, the gas remaining in the reactor is removed, and the reaction product mixture is analyzed by gas chromatography, which is the same as in Example 1.

[0094] Gas chromatography analysis shows that the reaction system contains diethylamine, that is, diethylamine is produced from ethylamine and acetaldehyde through the reduction of sodium formate. The reaction product mixture is purified by rectification and distilled at normal pressure, and the fraction of 89-91℃ is collected, and triethylamine with a purity of 99% is obtained, with a product yield of 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, the gas remaining in the reactor is removed, and the reaction product mixture is analyzed by gas chromatography. The gas chromatography is the same as in Example 1. According to the gas chromatography analysis, the reaction product mixture only has sample peaks of acetaldehyde and diisopropylamine, but diisopropylethylamine is not produced in the reactor. Comparing this Comparative Example 1 with Example 4, it is found that a protic ionic liquid is formed from the acid and secondary amine added in the present invention, and such a protic ionic liquid reacts with the aldehyde to produce a Schiff base, which is then easily reduced to a tertiary amine by a reducing agent, and when no acid is added, the system does not form a protic ionic liquid, and the secondary amine and aldehyde cannot react.

[0098] Comparative Example 2 Synthesis of diethylamine by 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, the gas remaining in the reactor is removed, and the reaction product mixture is analyzed by gas chromatography, which is the same as in Example 1.

[0101] Gas chromatography analysis shows that the reaction system contains diethylamine, that is, diethylamine is produced from ethylamine and acetaldehyde through the reduction of sodium formate. The reaction product mixture is purified by rectification and distilled at normal pressure, and the fraction at 55-56℃ is collected, and diethylamine with a purity of 99% is obtained, with a product yield of 55%.

[0102] Generally, the reaction of primary amine and aldehyde to generate secondary amine is easier to carry out than the reaction of corresponding secondary amine and aldehyde to generate tertiary amine, and the yield of primary amine and aldehyde to generate secondary amine is higher than the yield of corresponding secondary amine to generate tertiary amine using secondary amine as raw material.On the other hand, in Comparative Example 2, the yield of primary amine diethylamine and acetaldehyde to generate secondary amine diethylamine is obviously lower than the yield of the present invention in which diethylamine first generates protic ionic liquid of diethylamine formate with formic acid, and then this ionic liquid reacts with acetaldehyde and is reduced to generate tertiary amine triethylamine.In the present invention, when protic ionic liquid and aldehyde react to generate tertiary amine through reduction, 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 merely for the purpose of illustrating the technical ideas and features of the present invention, and are intended to enable those skilled in the art to understand and practice the contents of the present invention, but are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications substantially made according to the idea of ​​the present invention shall be included in the scope of protection of the present invention.

[0104] Any endpoints of ranges and any values ​​disclosed herein should be understood to be not limited to the exact ranges or values, but rather to include values ​​close to those ranges or values. Numerical ranges between the endpoints of each range, between the endpoints of each range and the single point value, and between the single point values ​​can be combined with each other to obtain one or more numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

Claims

1. The method includes the steps of: reacting a secondary amine as a raw material 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. A method for preparing a tertiary amine from a secondary amine, comprising the steps of: The structural formula of the secondary amine is 【Chemistry 1】 and R 1 and R 2 are independently selected from isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isohexyl, sec-hexyl, isoheptyl, sec-heptyl, isooctyl, sec-octyl, 2-ethylhexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, 2-naphthyl, 2,3,4-trimethylphenyl, 2,3,5-trimethylphenyl, 2,3,6-trimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-n-propylphenyl, 3-n-propylphenyl, and 4-n-propylphenyl; or forms pyrrole, piperidine, morpholine, piperazine, N-methylpiperazine, cyclohexamethyleneimine or azetidine together with NH; The aldehyde has the structural formula 【Chemistry 2】 A monoaldehyde having the structural formula 【Chemistry 3】 or a polymer of a monoaldehyde having the structural formula 【Chemistry 4】 R 3 is selected from a C 1 -C 6 alkyl group, a hydroxyl-substituted C 1 -C 6 alkyl group, and R 4 is selected from a single bond or a C 1 -C 4 alkylidene group; the molar ratio of said secondary amine to said acid is from 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 more combinations of formic acid, sodium formate, oxalic acid, sodium oxalate, and triphenylsilane; The method comprises: 1) adding the acid dropwise to the secondary amine, or adding the secondary amine dropwise to 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 2-5.0 MPa, heating to 60-200° C., and reacting for 5-300 minutes; 4) purifying the reaction system after the reaction is completed to obtain the tertiary amine; In step 4), the purification is atmospheric rectification or vacuum rectification; A method for preparing tertiary amines using secondary amines as raw materials.

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 the secondary amine according to claim 1 as a raw material.

3. The acid is １ ~C ３ , hydrochloric acid, carbonic acid, sulfuric acid, phosphoric acid, and nitric acid in combination. A method for preparing a tertiary amine using the secondary amine according to claim 1 as a raw material.

4. The acid is selected from one or more combinations 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 the secondary amine according to claim 3 as a raw material.

5. The reducing agent is selected from formic acid, sodium formate, oxalic acid, or sodium oxalate. A method for preparing a tertiary amine using the secondary amine according to claim 1 as a raw material.

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 the secondary amine according to claim 1 as a raw material.

7. The step of reacting the secondary amine with an acid to produce a protic ionic liquid is carried out at room temperature and normal pressure. A method for preparing a tertiary amine using the secondary amine according to claim 1 as a raw material.

8. The step of reacting the protic ionic liquid with the aldehyde under the action of a reducing agent to produce a tertiary amine is carried out at a temperature of 120 to 160°C, and / or the time for reacting the protic ionic liquid with the aldehyde under the action of a reducing agent is 30 to 120 minutes. A method for preparing a tertiary amine using the secondary amine according to claim 1 as a raw material.

9. In step 1), the acid is added dropwise to the aqueous solution of the secondary amine to form the protic ionic liquid; and / or in step 1), the acid is added dropwise to 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.

10. The structural formula of the protic ionic liquid is 【Chemistry 5】 and n is selected from 1, 2 or 3; [X] ｎ- is C １ ~C ３ Organic carboxyl, CO ３ ２- , HCO ３ - , Cl - , NO ３ - , S.O. ４ ２- , P.O. ４ ３－ , H.P.O. ４ ２- Or H ２ P.O. 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.

11. The R ３ is selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, isohexyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, and / or 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, metaldehyde, 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.

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