A method for economically and continuously preparing tertiary amines

Abstract

The invention discloses a method for economically and continuously preparing tertiary amines. The method comprises the following steps: 1) reacting a secondary amine with an excess of acid to obtain a mixture containing a proton-type ionic liquid and unreacted acid; 2) reacting the mixture with an aldehyde in a reactor, using the unreacted acid as a reducing agent to generate a tertiary amine, and obtaining a reaction system containing the tertiary amine; 3) adding a secondary amine to the reaction system again for extraction and separation to obtain an organic phase and an aqueous phase, wherein the organic phase contains the tertiary amine, and the aqueous phase is circulated to the reactor for continuous reaction; the secondary amine in step 1) is the same as the secondary amine in step 3). The invention further improves the utilization rate of raw materials by adding a secondary amine that is the same as the reaction raw material to the reaction system containing the product tertiary amine, extracting the reaction system, and then rectifying the organic phase obtained by extraction to obtain a high-purity tertiary amine product, and recycling the aqueous phase obtained by extraction.

Description

Technical Field

[0001] The present invention relates to a method for economically and continuously preparing tertiary amines. Background Art

[0002] Tertiary amines are widely used in industrial production and life. They can be used as fuel additives, pesticide production, pharmaceutical synthesis, epoxy resin hardeners, intermediates of polyurethane catalysts, raw materials for preparing quaternary ammonium salts / bases, plasticizers, dyes, desulfurizers, etc.

[0003] The conventional synthesis of known tertiary amine products often uses a high-pressure fixed bed reaction device and uses a heterogeneous noble metal catalyst such as Pd or Pt supported on a carrier, and the reaction also needs to be carried out under hydrogen conditions. For example, CN101460445A discloses a method for preparing diisopropylethylamine by amination reaction of diisopropylamine and acetaldehyde using a suspended catalyst Pd / C as a catalyst, and the reaction requires high pressure and hydrogen conditions, and the noble metal catalyst is expensive.

[0004] It is also known that a tertiary amine can be generated by reacting a secondary amine and an aldehyde having more than 2 carbon atoms in the presence of a reducing agent without using a metal catalyst or hydrogen and under normal pressure. For example, Chinese patent 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 method is characterized in that the aldehyde and formic acid are first mixed, heated to reflux temperature, and then the secondary amine is added to react. The method has requirements for the dropwise addition sequence of the raw materials. When the aldehyde or acid is added dropwise to the other two raw materials, the reaction yield is significantly reduced. After the reaction is completed, a large amount of alkali (such as a 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 waste water containing organic matter.

[0005] It is also known that Chinese patent publication CN102875385A discloses a method of using paraldehyde as a raw material, hydrolyzing it with an acidic catalyst, and then reacting it with diisopropylamine and a reducing agent metal hydride such as sodium borohydride to produce a tertiary amine. The patent does not disclose the purity of the tertiary amine product. At the same time, the reducing agent used, such as sodium borohydride, is highly toxic, easily explosive, and sensitive to water, which is not conducive to the operation of the reaction. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for economically and continuously preparing tertiary amines in view of the shortcomings and deficiencies of the prior art. The method can be continuously produced, and the reaction raw materials can be fully utilized, no waste is discharged during the production process, and the method does not require high-pressure hydrogen and metal catalyst conditions, and the reaction process is safer.

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is as follows:

[0008] A method for continuously preparing tertiary amines, the method comprising the following steps: 1) reacting a secondary amine with an excess of acid to obtain a mixture containing a proton type ionic liquid and unreacted acid; 2) reacting the mixture with an aldehyde in a reactor, using the unreacted acid as a reducing agent to generate a tertiary amine, and obtaining a reaction system containing the tertiary amine; 3) adding a secondary amine to the reaction system again for extraction and separation to obtain an organic phase and an aqueous phase, wherein the organic phase contains the tertiary amine, and circulating the aqueous phase to the reactor for continuous reaction; the secondary amine in step 1) is the same as the secondary amine in step 3).

[0009] In some embodiments, the method further comprises the step of adding aldehyde and acid to the aqueous phase before the circulation, wherein the amount of adding aldehyde and acid is such that the molar ratio of the secondary amine, aldehyde and acid in the reactor remains unchanged.

[0010] In some embodiments, the method further comprises the step of distilling the organic phase to obtain a tertiary amine.

[0011] In some embodiments, the amount of the secondary amine added again in step 3) is such that the pH value of the aqueous phase is 10-13.

[0012] In some embodiments, the reactor is selected from a combination of one or more of a microchannel reactor, a continuous tank reactor and a tubular reactor, preferably a microchannel reactor or a tubular reactor, and further preferably a reactor combining a microchannel reactor and a tubular reactor.

[0013] In some embodiments, the reaction pressure in step 2) is 0-5.0 MPa, preferably 0-4.0 MPa, and particularly preferably 0-3.0 MPa. That is, the reaction of the present invention can also be carried out under normal pressure.

[0014] In some embodiments, the reaction temperature in step 2) is 60-250°C, preferably 120-220°C.

[0015] In some embodiments, the reaction time in step 2) is 5-300 minutes, preferably 30-120 minutes.

[0016] In some embodiments, the acid is selected from formic acid or oxalic acid. The acid first reacts with the secondary amine in step 1) to generate a protic ionic liquid, which then reacts with the aldehyde to generate the target product, a tertiary amine. The excess acid in step 1), such as formic acid or oxalic acid, can also be used as a reducing agent for the reaction of generating the tertiary amine in step 2), and no additional reducing agent needs to be added during the reaction. Moreover, using formic acid or oxalic acid as a reducing agent is safer than reducing agents such as sodium borohydride in the prior art.

[0017] In some embodiments, the molar ratio of the acid to the secondary amine is 1.0-4.0, preferably 1.1-3.0, particularly preferably 1.2-2.5. The molar ratio is an excess of acid.

[0018] In some embodiments, the molar ratio of the aldehyde to the secondary amine is 0.1-5.0, preferably 0.2-3.0, and particularly preferably 0.3-2.0.

[0019] In some embodiments, the secondary amine has 30 or less carbon atoms, preferably 25 or less, and more preferably 20 or less carbon atoms.

[0020] In some embodiments, the secondary amine is an aliphatic secondary amine, an aromatic secondary amine, or a cyclic secondary amine.

[0021] In some embodiments, the aldehyde is a monoaldehyde, a dialdehyde, or a polymer of aldehydes.

[0022] In some embodiments, the structural formula of the secondary amine is Wherein R1 and R2 are independently selected from C1-C8 alkyl, C4-C8 cycloalkyl, aryl or C7-C9 alkylaryl, or R1, R2 and NH together form a C3-C7 ring.

[0023] Further, R1 and R2 are independently selected from 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 or cyclooctyl, phenyl, 2-naphthyl, 2-methylphenyl, 3- phenyl, 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, 4-n-propylphenyl.

[0024] Furthermore, the R1, R2 and NH together form pyrrole, piperidine, morpholine, piperazine, N-methylpiperazine, cycloheximide or azocyclobutane.

[0025] In some embodiments, the aldehyde is selected from the group consisting of The monoaldehyde with the structural formula is The polymer of the monoaldehyde or the structural formula is The dialdehyde, wherein R3 is selected from H, C1-C6 alkyl, hydroxy-substituted C1-C6 alkyl, and R4 is selected from a single bond or C1-C4 alkylene.

[0026] Furthermore, R3 is selected from H, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, isohexyl, hydroxymethyl, hydroxyethyl, and hydroxypropyl.

[0027] Furthermore, the R4 is selected from a single bond, a methylene group, an ethylene group, a propylene group, and a butylene group.

[0028] Furthermore, the aldehyde is selected from acetaldehyde, trimeraldehyde, tetraacetaldehyde, propionaldehyde, glycoaldehyde, glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde or adipaldehyde.

[0029] The structural formula of the proton type ionic liquid is wherein R1 and R2 are independently selected from C1-C8 alkyl, C4-C8 cycloalkyl, aryl or C7-C9 alkylaryl, or R1, R2 and N together form a C3-C7 ring, n is selected from 1, 2 or 3, [X] n- Selected from formate or oxalate.

[0030] The aldehyde is selected from the group consisting of The monoaldehyde with the structural formula is When the polymer of the monovalent aldehyde is prepared, the reaction formula of the protic ionic liquid and the aldehyde is as follows:

[0031]

[0032] The aldehyde is selected from the group consisting of When the dialdehyde is substituted by the proton type ionic liquid, the reaction formula of the proton type ionic liquid and the aldehyde is as follows:

[0033]

[0034] The proton type ionic liquid first reacts with the aldehyde to generate the corresponding Schiff base, and the Schiff base is reduced by a reducing agent to prepare the tertiary amine.

[0035] In some embodiments, step 1) is performed at room temperature and atmospheric pressure.

[0036] In some embodiments, the secondary amine is selected from dimethylamine, diisopropylamine, and piperidine; the aldehyde is selected from acetaldehyde, trimeraldehyde, propionaldehyde, ethanolaldehyde, or succinaldehyde; the tertiary amine is selected from dimethylethylamine, dimethylpropylamine, N,N,N',N'-tetramethylbutanediamine, dimethylbutylamine, diisopropylethylamine, diisopropylpropylamine, and N-ethylpiperidine.

[0037] In a particularly preferred embodiment, acetaldehyde and dimethylamine are reacted to form dimethylethylamine.

[0038] In a particularly preferred embodiment, propionaldehyde and dimethylamine are reacted to form dimethylpropylamine.

[0039] In a particularly preferred embodiment, succinaldehyde and dimethylamine are reacted to form N,N,N',N'-tetramethylbutanediamine.

[0040] In a particularly preferred embodiment, acetaldehyde and diisopropylamine are reacted to form diisopropylethylamine.

[0041] In some embodiments, the method includes the following steps: 1) reacting a secondary amine with an excess of acid to obtain a mixture containing a proton-type ionic liquid and unreacted acid; 2) pumping the mixture and the aldehyde into the reactor through a plunger pump for reaction, the unreacted acid is used as a reducing agent to generate a tertiary amine, and a reaction system containing a tertiary amine is obtained, the reaction pressure is 0-5.0 MPa, the temperature is 60-200° C., and the time is 5-300 minutes; 3) adding the same type of secondary amine as in step 1) to the reaction system again for extraction and separation to obtain an organic phase and an aqueous phase; 4) distilling the organic phase to obtain a tertiary amine, adding aldehyde and acid to the aqueous phase, and circulating the aqueous phase to the reactor for continuous reaction, and the degree of adding aldehyde and acid is such that the molar ratio of the secondary amine, aldehyde and acid in the reactor remains unchanged.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] The present invention creatively synthesizes the corresponding tertiary amine continuously in a reaction system with secondary amine as raw material and aldehyde as reducing agent (acid), extracts the reaction system by adding the same secondary amine as the reaction raw material into the reaction system containing the product tertiary amine, and then rectifies the organic phase obtained by extraction to obtain a high-purity tertiary amine product, and at the same time recycles the aqueous phase obtained by extraction and returns it to the reactor so that the unreacted secondary amine and aldehyde therein are recycled, so that the utilization rate of the raw materials can be improved, and after continuous production by recycling, the utilization rate of the raw materials can achieve 100%. In order to better control the molar ratio of each material in the reactor, the present invention adds the corresponding aldehyde and acid raw materials to the aqueous phase before the aqueous phase is returned to the reactor.

[0044] In addition, the present invention creatively uses secondary amine as a raw material to generate tertiary amine in a system in which secondary amine is used as a raw material, firstly reacts the secondary amine with an acid to generate a proton-type ionic liquid, and then reacts the proton-type ionic liquid with an aldehyde under the premise that excess acid further acts as a reducing agent to generate a tertiary amine. The proton-type ionic liquid can play a self-catalytic role, so that the reaction system can achieve mild reaction conditions while ensuring high purity and high yield of the tertiary amine product, without the need for high pressure and hydrogen reaction atmosphere, and at the same time, the reaction can use a mild and safe acid as a reducing agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a diethylamine-formic acid protonic ionic liquid;

[0046] Figure 2 It is a di-n-propylamine-formic acid protonic ionic liquid;

[0047] Figure 3 It is a diisopropylamine-formic acid protonic ionic liquid;

[0048] Figure 4 It is a di-n-butylamine-formic acid protonic ionic liquid. DETAILED DESCRIPTION

[0049] The applicant submitted a patent application with application number 202210034548.2 in January 2023. The application first uses a secondary amine and an acid to react at room temperature and pressure to generate a proton-type ionic liquid, and then reacts the proton-type ionic liquid with an aldehyde in the presence of a reducing agent to generate a target product, a tertiary amine. Compared with the prior art that uses precious metal catalysts, or requires the addition of a large amount of alkali to the reaction system, or requires the use of metal hydrides such as sodium borohydride as a reducing agent, the proton-type ionic liquid in this application can act as a catalyst, and the reaction is a homogeneous autocatalytic reaction, which does not require high-pressure hydrogen and metal catalyst conditions, and can use a milder, safer and greener reducing agent.

[0050] In this application, the reaction product mixture containing tertiary amine is directly distilled and purified, which will cause a small amount of unreacted raw materials to be wasted without being fully utilized. On this basis, the inventors conducted further research and development and found that after the reaction is completed, the tertiary amine dissolved in the aqueous phase can be extracted into the organic phase by adding a secondary amine of the same type as the raw material secondary amine to the reaction product mixture. On the one hand, compared with the corresponding tertiary amine, the secondary amine has less steric hindrance and is easier to form corresponding salts with the acid radical ions in the solution; on the other hand, the solubility of the tertiary amine in water is worse than that of the secondary amine, and the tertiary amine can be separated from the aqueous phase by simple phase separation. The amount of the secondary amine added is preferably such that the pH in the aqueous phase is 10-13, so that the tertiary amine can be present in the organic phase in the form of molecules, and the unreacted small amount of acid and aldehyde raw materials are also in the aqueous phase, so that the reaction product can be extracted and separated to separate the tertiary amine and the small amount of unreacted aldehyde and acid raw materials. After extraction and separation, the tertiary amine can be further distilled and purified to improve the purity, and the secondary amine in the aqueous phase, as well as the unreacted aldehyde and acid can be recycled and returned to the reactor for use, and in order to ensure the constant ratio of raw materials in the reactor, before the aqueous phase returns to the reactor, the corresponding amount of aldehyde and acid is added to the reverse phase. With this scheme, the present application can realize the continuous production of tertiary amines, and the raw material utilization rate can achieve 100%.

[0051] The present invention is further described below in conjunction with the examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to the different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0052] Example 1

[0053] Dimethylamine and acetaldehyde react to synthesize dimethylethylamine:

[0054] Dimethylamine and formic acid were prepared into solution A at a molar ratio of 1:1.5, and solution A and acetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of acetaldehyde to dimethylamine of 1:1 by a plunger pump, the reaction pressure was controlled at 1 MPa, the reaction temperature was controlled at 140°C, and the residence time of the material was controlled at 120 minutes by adjusting the flow rate of the pump.

[0055] The reaction mass at the reactor outlet is mixed with dimethylamine, and the amount of dimethylamine added is such that the pH of the aqueous phase after stratification is 10. The mixture is phase separated. The obtained upper organic phase is rectified to obtain dimethylethylamine with a purity of 99.5%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding formic acid, and is returned to solution A as a raw material and continuously pumped into the reactor together with acetaldehyde for reaction.

[0056] After the reaction was completed, the final yield of dimethylethylamine was 98.6%.

[0057] Example 2

[0058] Synthesis of dimethylethylamine from dimethylamine and triacetaldehyde:

[0059] Dimethylamine and oxalic acid were prepared into solution A at a molar ratio of 1:1.6, and solution A and triacetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of triacetaldehyde to dimethylamine of 0.35:1 by a plunger pump, the reaction pressure was controlled at 2 MPa, the reaction temperature was controlled at 160°C, and the residence time of the material was controlled at 90 minutes by adjusting the flow rate of the pump.

[0060] The reaction material at the reactor outlet was mixed with dimethylamine, and the amount of dimethylamine added was such that the pH of the aqueous phase after stratification was 11. The mixture was phase separated. The obtained upper organic phase was rectified to obtain dimethylethylamine with a purity of 99.6%, and the obtained lower aqueous phase was configured to have the same composition as solution A by adding oxalic acid, and it was returned to solution A as a raw material and continued to be pumped into the reactor together with acetaldehyde for reaction.

[0061] After the reaction was completed, the final yield of dimethylethylamine was 99.2%.

[0062] Example 3

[0063] Synthesis of dimethylpropylamine from dimethylamine and propionaldehyde:

[0064] Dimethylamine and formic acid were prepared into solution A at a molar ratio of 1:1.4, and solution A and propionaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of propionaldehyde to dimethylamine of 1.1:1 by a plunger pump, the reaction pressure was controlled at 1.8 MPa, the reaction temperature was controlled at 180°C, and the residence time of the material was controlled at 80 minutes by adjusting the flow rate of the pump.

[0065] The reaction mass at the reactor outlet is mixed with dimethylamine, and the amount of dimethylamine added is such that the pH of the aqueous phase after stratification is 10.5. The mixture is phase separated. The obtained upper organic phase is distilled to obtain dimethylpropylamine with a purity of 99.7%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding formic acid, and it is returned to solution A as a raw material and continues to be pumped into the reactor together with propionaldehyde for reaction.

[0066] After the reaction was completed, the final yield of dimethylethylamine was 99.1%.

[0067] Example 4

[0068] Dimethylamine and butyraldehyde react to synthesize dimethylbutylamine:

[0069] Dimethylamine and oxalic acid were prepared into solution A at a molar ratio of 1:1.7, and solution A and butyraldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of butyraldehyde to dimethylamine of 1.2:1 by a plunger pump, the reaction pressure was controlled at 2.5 MPa, the reaction temperature was controlled at 180°C, and the residence time of the material was controlled at 90 minutes by adjusting the flow rate of the pump.

[0070] The reaction mass at the reactor outlet is mixed with dimethylamine, and the amount of dimethylamine added is such that the pH of the aqueous phase after stratification is 10. The mixture is phase separated. The obtained upper organic phase is distilled to obtain dimethylbutylamine with a purity of 99.8%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding oxalic acid, and it is returned to solution A as a raw material and continues to be pumped into the reactor together with butyraldehyde for reaction.

[0071] After the reaction was completed, the final yield of dimethylbutylamine was 99.4%.

[0072] Example 5

[0073] Dimethylamine and succinaldehyde react to synthesize N,N,N',N'-tetramethylbutanediamine:

[0074] Dimethylamine and formic acid were prepared into solution A at a molar ratio of 1:1.6, and solution A and succinaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of succinaldehyde to dimethylamine of 0.5:1 by a plunger pump, the reaction pressure was controlled at 2.5 MPa, the reaction temperature was controlled at 180°C, and the residence time of the material was controlled at 120 minutes by adjusting the flow rate of the pump.

[0075] The reaction mass at the reactor outlet is mixed with dimethylamine, and the amount of dimethylamine added is such that the pH of the aqueous phase after stratification is 11. The mixture is phase separated. The obtained upper organic phase is distilled to obtain N,N,N',N'-tetramethylbutylene diamine with a purity of 99.5%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding oxalic acid, and it is returned to solution A as a raw material and continues to be pumped into the reactor together with succinaldehyde for reaction.

[0076] After the reaction was completed, the final yield of N,N,N',N'-dimethylbutanediamine was 99.3%.

[0077] Example 6

[0078] Diethylamine and acetaldehyde react to synthesize triethylamine:

[0079] Diethylamine and formic acid are configured into solution A at a molar ratio of 1:1.5, and solution A and acetaldehyde are pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of acetaldehyde to diethylamine of 1.1:1 by a plunger pump, the reaction pressure is controlled at 2.1 MPa, the reaction temperature is controlled at 200° C., and the residence time of the material is controlled at 60 minutes by adjusting the flow rate of the pump.

[0080] The reaction mass at the reactor outlet is mixed with diethylamine in an amount such that the pH of the aqueous phase after stratification is 11. The mixture is phase separated. The obtained upper organic phase is rectified to obtain triethylamine with a purity of 99.5%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding formic acid, and is returned to solution A as a raw material and continuously pumped into the reactor together with acetaldehyde for reaction.

[0081] After the reaction was completed, the final yield of triethylamine was 99.7%.

[0082] The NMR of solution A component is as follows Figure 1 As shown, a diethylamine-formic acid protic ionic liquid is formed.

[0083] Example 7

[0084] Di-n-propylamine and acetaldehyde react to synthesize di-n-propylethylamine:

[0085] Di-n-propylamine and formic acid were prepared into solution A at a molar ratio of 1:1.5, and solution A and acetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of acetaldehyde to di-n-propylamine of 1.1:1 by a plunger pump, the reaction pressure was controlled at 2.2 MPa, the reaction temperature was controlled at 220° C., and the residence time of the material was controlled at 100 minutes by adjusting the flow rate of the pump.

[0086] The reaction mass at the reactor outlet is mixed with di-n-propylamine, and the amount of di-n-propylamine added is such that the pH of the aqueous phase after stratification is 11. The mixture is phase separated. The obtained upper organic phase is rectified to obtain di-n-propylethylamine with a purity of 99.6%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding formic acid, and it is returned to solution A as a raw material and continuously pumped into the reactor together with acetaldehyde for reaction.

[0087] After the reaction was completed, the final yield of di-n-propylethylamine was 99.3%.

[0088] The NMR of solution A component is as follows Figure 2 As shown, a di-n-propylamine-formic acid protic ionic liquid is formed.

[0089] Example 8

[0090] Diisopropylamine and triacetaldehyde react to synthesize diisopropylethylamine:

[0091] Diisopropylamine and formic acid were prepared into solution A at a molar ratio of 1:1.8, and solution A and triacetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of triacetaldehyde to diisopropylamine of 0.3:1 by a plunger pump, the reaction pressure was controlled at 3 MPa, the reaction temperature was controlled at 220° C., and the residence time of the material was controlled at 60 minutes by adjusting the flow rate of the pump.

[0092] The reaction mass at the reactor outlet was mixed with diisopropylamine in an amount such that the pH of the aqueous phase after separation was 10. The mixture was phase separated. The obtained upper organic phase was rectified to obtain diisopropylethylamine with a purity of 99.6%. The obtained lower aqueous phase was configured to have the same composition as solution A by adding formic acid, and it was returned to solution A as a raw material and continued to be pumped into the reactor together with triacetaldehyde for reaction.

[0093] After the reaction was completed, the final yield of diisopropylethylamine was 99.4%.

[0094] The NMR of solution A component is as follows Figure 3 As shown, a diisopropylamine-formic acid protic ionic liquid is formed.

[0095] Example 9

[0096] Diisopropylamine and propionaldehyde react to synthesize diisopropylpropylamine:

[0097] Diisopropylamine and formic acid were prepared into solution A at a molar ratio of 1:2.0, and solution A and propionaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of propionaldehyde to diisopropylamine of 1.1:1 by a plunger pump, the reaction pressure was controlled at 2 MPa, the reaction temperature was controlled at 200° C., and the residence time of the material was controlled at 60 minutes by adjusting the flow rate of the pump.

[0098] The reaction mass at the reactor outlet is mixed with diisopropylamine, and the amount of diisopropylamine added is such that the pH of the aqueous phase after stratification is 10. The mixture is phase separated. The obtained upper organic phase is distilled to obtain diisopropylamine with a purity of 99.7%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding formic acid, and it is returned to solution A as a raw material and continues to be pumped into the reactor together with propionaldehyde for reaction.

[0099] After the reaction was completed, the final yield of dimethylpropylamine was 99.3%.

[0100] Example 10

[0101] Diisopropylamine and n-butyraldehyde react to synthesize diisopropylpropylamine:

[0102] Diisopropylamine and formic acid were prepared into solution A at a molar ratio of 1:1.8, and solution A and butyraldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of n-butyraldehyde to diisopropylamine of 1:1 by a plunger pump, the reaction pressure was controlled at 2.5 MPa, the reaction temperature was controlled at 200°C, and the residence time of the material was controlled at 90 minutes by adjusting the flow rate of the pump.

[0103] The reaction mass at the reactor outlet is mixed with diisopropylamine, and the amount of diisopropylamine added is such that the pH of the aqueous phase after stratification is 10. The mixture is phase separated. The obtained upper organic phase is distilled to obtain diisopropylamine with a purity of 99.7%. The obtained lower aqueous phase is configured to have the same composition as solution A by adding formic acid, and it is returned to solution A as a raw material and continues to be pumped into the reactor together with butyraldehyde for reaction.

[0104] After the reaction was completed, the final yield of dimethylbutylamine was 99.2%.

[0105] Embodiment 11

[0106] Piperidine and acetaldehyde react to synthesize N-ethylpiperidine:

[0107] Piperidine and oxalic acid were prepared into solution A at a molar ratio of 1:1.8, and solution A and acetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of acetaldehyde to piperidine of 1.1:1 by a plunger pump, the reaction pressure was controlled at 2.5 MPa, the reaction temperature was controlled at 220°C, and the residence time of the material was controlled at 120 minutes by adjusting the flow rate of the pump.

[0108] The reaction mass at the reactor outlet was mixed with piperidine in an amount such that the pH of the aqueous phase after stratification was 11. The mixture was phase separated. The obtained upper organic phase was rectified to obtain N-ethylpiperidine with a purity of 99.5%. The obtained lower aqueous phase was configured to have the same composition as solution A by adding oxalic acid, and it was returned to solution A as a raw material and continued to be pumped into the reactor together with acetaldehyde for reaction.

[0109] After the reaction was completed, the final yield of N-ethylpiperidine was 99.1%.

[0110] Example 12

[0111] Di-n-butylamine and acetaldehyde react to synthesize di-n-butylethylamine:

[0112] Di-n-butylamine and formic acid were configured into solution A at a molar ratio of 1:1.6, and solution A and acetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of acetaldehyde to di-n-butylamine of 1.05:1 by a plunger pump, the reaction pressure was controlled at 2.3 MPa, the reaction temperature was controlled at 220° C., and the residence time of the material was controlled at 90 minutes by adjusting the flow rate of the pump.

[0113] The reaction mass at the reactor outlet was mixed with di-n-butylamine, and the amount of di-n-butylamine added was such that the pH of the aqueous phase after stratification was 11. The mixture was phase separated. The obtained upper organic phase was distilled to obtain di-n-butylethylamine with a purity of 99.5%. The obtained lower aqueous phase was configured to have the same composition as solution A by adding formic acid, and it was returned to solution A as a raw material and continued to be pumped into the reactor together with acetaldehyde for reaction.

[0114] After the reaction was completed, the final yield of di-n-butylethylamine was 99.5%.

[0115] The NMR of solution A component is as follows Figure 4 As shown, a di-n-butylamine-formic acid protic ionic liquid is formed.

[0116] Comparative Example 1

[0117] The reaction of dimethylamine and acetaldehyde:

[0118] Dimethylamine and formic acid were prepared into solution A at a molar ratio of 1:1.5, and solution A and acetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of acetaldehyde to dimethylamine of 1:1 by a plunger pump, the reaction pressure was controlled at 1 MPa, the reaction temperature was controlled at 140°C, and the residence time of the material was controlled at 120 minutes by adjusting the flow rate of the pump.

[0119] The reaction materials at the reactor outlet are directly fed into a distillation tower for separation to obtain dimethylethylamine with a purity of 99.5%. The final yield of dimethylethylamine is 95.1%.

[0120] Comparison of Comparative Example 1 with Example 1 shows that the present invention further improves the yield of the target product tertiary amine by adding a secondary amine for extraction and separation after the reaction is completed and recycling the aqueous phase, thereby making full use of the reaction raw materials and improving the utilization rate of the reaction raw materials.

[0121] Comparative Example 2

[0122] Diisopropylamine and triacetaldehyde react to synthesize diisopropylethylamine:

[0123] Diisopropylamine and formic acid were prepared into solution A at a molar ratio of 1:1.8, and solution A and triacetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of triacetaldehyde to diisopropylamine of 0.3:1 by a plunger pump, the reaction pressure was controlled at 3 MPa, the reaction temperature was controlled at 220° C., and the residence time of the material was controlled at 60 minutes by adjusting the flow rate of the pump.

[0124] The reaction materials at the reactor outlet are directly fed into a distillation tower for separation to obtain diisopropylethylamine with a purity of 99.2%. The final yield of diisopropylethylamine is 96.2%.

[0125] Comparing Comparative Example 2 with Example 8, it can be seen that the addition of secondary amine after the reaction for extraction and separation and recycling of the aqueous phase can further improve the yield of the target product tertiary amine, fully utilize the reaction raw materials, and improve the utilization rate of the reaction raw materials.

[0126] Comparative Example 3

[0127] Piperidine and acetaldehyde react to synthesize N-ethylpiperidine:

[0128] Piperidine and oxalic acid were prepared into solution A at a molar ratio of 1:1.8, and solution A and acetaldehyde were pumped into a microchannel reactor-tubular reactor combination reactor at a molar ratio of acetaldehyde to piperidine of 1.1:1 by a plunger pump, the reaction pressure was controlled at 2.5 MPa, the reaction temperature was controlled at 220°C, and the residence time of the material was controlled at 120 minutes by adjusting the flow rate of the pump.

[0129] The reaction materials at the reactor outlet are directly fed into a distillation tower for separation to obtain N-ethylpiperidine with a purity of 99.5%. The final yield of N-ethylpiperidine is 97.1%.

[0130] Comparing Comparative Example 2 with Example 11, it can be seen that the addition of secondary amine after the reaction for extraction and separation and recycling of the aqueous phase can further improve the yield of the target product tertiary amine, fully utilize the reaction raw materials, and improve the utilization rate of the reaction raw materials.

[0131] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0132] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A method for continuously preparing tertiary amines, characterized in that: The method comprises the following steps: 1) reacting a secondary amine with an excess of acid to obtain a mixture containing a proton-type ionic liquid and unreacted acid; 2) reacting the mixture with an aldehyde in a reactor, using the unreacted acid as a reducing agent to generate a tertiary amine to obtain a reaction system containing the tertiary amine; 3) adding a secondary amine to the reaction system again for extraction and separation to obtain an organic phase and an aqueous phase, wherein the organic phase contains the tertiary amine, and circulating the aqueous phase to the reactor for continuous reaction; the secondary amine in step 1) is the same as the secondary amine in step 3); In step 3), the amount of the secondary amine added again is such that the pH value of the aqueous phase is 10-13; The acid is selected from formic acid or oxalic acid; The structural formula of the secondary amine is Wherein R1 and R2 are independently selected from C1-C8 alkyl, or R1, R2 and NH together form a C3-C7 ring; The aldehyde is selected from the group consisting of The monoaldehyde with the structural formula is The polymer of the monoaldehyde or the structural formula is The dialdehyde, wherein R3 is selected from H, C1-C6 alkyl, hydroxy-substituted C1-C6 alkyl, R4 is selected from a single bond or C1-C4 alkylene; The method further comprises the step of adding aldehyde and acid to the aqueous phase before the circulation, wherein the amount of adding aldehyde and acid is such that the molar ratio of the secondary amine, aldehyde and acid in the reactor remains unchanged; The molar ratio of the acid to the secondary amine is 1.1-4.0; the molar ratio of the aldehyde to the secondary amine is 0.1-5.0; The structural formula of the proton type ionic liquid is wherein R1 and R2 are independently selected from C1-C8 alkyl, or R1, R2 and N together form a C3-C7 ring, n is selected from 1, 2 or 3, [X] n- Selected from formate or oxalate.

2. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The method further comprises the step of distilling the organic phase to obtain a tertiary amine.

3. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The reactor is selected from a combination of one or more of a microchannel reactor, a continuous tank reactor and a tubular reactor.

4. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The reaction pressure in step 2) is 0-5.0 MPa; and / or, the reaction temperature in step 2) is 60-250°C.

5. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The reaction time in step 2) is 5-300 minutes.

6. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The R1 and R2 are independently selected from 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, or R1, R2 together with NH form pyrrole, piperidine, morpholine, piperazine, N-methylpiperazine, cyclohexylimide or azocyclobutane.

7. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The R3 is selected from H, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, isohexyl, hydroxymethyl, hydroxyethyl, and hydroxypropyl.

8. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The R4 is selected from a single bond, a methylene group, an ethylene group, a propylene group, and a butylene group.

9. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The aldehyde is selected from acetaldehyde, trimeraldehyde, tetraacetaldehyde, propionaldehyde, glycoaldehyde, glyoxal, malondialdehyde, succindialdehyde, glutaraldehyde or adipaldehyde.

10. The method for continuously preparing tertiary amines according to claim 1, characterized in that: The method comprises the following steps: 1) reacting a secondary amine with an excess of acid to obtain a mixture containing a proton-type ionic liquid and unreacted acid; 2) pumping the mixture and the aldehyde into the reactor through a plunger pump for reaction, wherein the unreacted acid is used as a reducing agent to generate a tertiary amine to obtain a reaction system containing the tertiary amine, wherein the reaction pressure is 0-5.0 MPa, the temperature is 60-250° C., and the reaction time is 5-300 minutes; 3) adding the same secondary amine as that in step 1) to the reaction system again for extraction and separation to obtain an organic phase and an aqueous phase; 4) rectifying the organic phase to obtain a tertiary amine, adding aldehyde and acid to the aqueous phase, and circulating the aqueous phase to the reactor for continuous reaction, wherein the degree of adding aldehyde and acid is such that the molar ratio of the secondary amine, aldehyde and acid in the reactor remains unchanged.

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